Sample records for molecular beam mass

  1. Molecular Beam Mass Spectrometry (MBMS) (Revised) (Fact Sheet)

    SciTech Connect (OSTI)

    Not Available

    2011-07-01T23:59:59.000Z

    This fact sheet provides information about Molecular Beam Mass Spectrometry (MBMS) capabilities and applications at NREL's National Bioenergy Center. NREL has six MBMS systems that researchers and industry partners can use to understand thermochemical biomass conversion and biomass composition recalcitrance.

  2. Molecular beam mass spectrometric characterization of biomass pyrolysis products for fuels and chemicals

    SciTech Connect (OSTI)

    Agblevor, F.A.; Davis, M.F.; Evans, R.J. [National Renewal Energy Lab., Golden, CO (United States)

    1994-12-31T23:59:59.000Z

    Converting biomass feedstocks to fuels and chemicals requires rapid characterization of the wide variety of possible feedstocks. The combination of pyrolysis molecular beam mass spectrometry (Py-MBMS) and multivariate statistical analysis offers a unique capability for characterizing these feedstocks. Herbaceous and woody biomass feedstocks that were harvested at different periods were used in this study. The pyrolysis mass spectral data were acquired in real time on the MBMS, and multivariate statistical analysis (factor analysis) was used to analyze and classify Py-MBMS data into compound classes. The effect of harvest times on the thermal conversion of these feedstocks was assessed from these data. Apart from sericea lespedeza, the influence of harvest time on the pyrolysis products of the various feedstocks was insignificant. For sericea lespedeza, samples harvested before plant defoliation were significantly different from those harvested after defoliation. The defoliated plant samples had higher carbohydrate-derived pyrolysis products than the samples obtained from the foliated plant. Additionally, char yields from the defoliated plant samples were lower than those from the foliated plant samples.

  3. Rapid characterization of lignocellulosic feedstocks for fuels and chemicals: Molecular beam mass spectrometric approach

    SciTech Connect (OSTI)

    Agblevor, F.A.; Davis, M.F. [National Renewable Energy Lab., Golden, CO (United States)

    1996-12-31T23:59:59.000Z

    Rapid characterization of biomass feedstocks has a pivotal role in the development of biomass energy because of the large number of samples that must be analyzed due to the diversity of biomass feedstocks and the significant differences in the chemical and physical properties of these feedstocks. Several biomass feedstocks (herbaceous, woody, and agricultural residues) were screened for the effects of storage, season of harvest, geographic location, clonal, and species variation on the pyrolysis products of the feed stocks. For herbaceous species such as sericea lespedeza, the season of harvest had a significant effect on the pyrolysis products. Effects of clonal variation on the composition of hybrid poplar feedstocks was easily discerned with the molecular beam mass spectrometric analysis. The effect of geographic location on the poplar clones pyrolysis products was minimal. However in the case of switchgrass, varietal influence on the pyrolysis products was minimal, but where the plant was grown had a strong influence on the pyrolysis products of the feedstock. Significant differences because of species variation could also be shown from the pyrolysis products of various biomass feedstocks. The influence of storage time on biomass samples stored outside in the open could also be discerned from the pyrolysis products of the feedstocks. The differences noted in the pyrolysis products of the feedstocks were noted for samples which were significantly degraded during storage either through the action of microflora or weathering.

  4. Effusive molecular beam-sampled Knudsen flow reactor coupled to vacuum ultraviolet single photon ionization mass spectrometry using an external free radical source

    SciTech Connect (OSTI)

    Leplat, N.; Rossi, M. J. [Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland)] [Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland)

    2013-11-15T23:59:59.000Z

    A new apparatus using vacuum ultraviolet single photon ionization mass spectrometry (VUV SPIMS) of an effusive molecular beam emanating from a Knudsen flow reactor is described. It was designed to study free radical-molecule kinetics over a significant temperature range (300–630 K). Its salient features are: (1) external free radical source, (2) counterpropagating molecular beam and diffuse VUV photon beam meeting in a crossed-beam ion source of a quadrupole mass spectrometer with perpendicular ion extraction, (3) analog detection of the photocurrent of the free radical molecular cation, and (4) possibility of detecting both free radicals and closed shell species in the same apparatus and under identical reaction conditions owing to the presence of photoelectrons generated by the photoelectric effect of the used VUV-photons. The measured thermal molecular beam-to-background ratio was 6.35 ± 0.39 for Ar and 10.86 ± 1.59 for i-C{sub 4}H{sub 10} at 300 K, a factor of 2.52 and 1.50 smaller, respectively, than predicted from basic gas-dynamic considerations. Operating parameters as well as the performance of key elements of the instrument are presented and discussed. Coupled to an external free radical source a steady-state specific exit flow of 1.6 × 10{sup 11} and 5.0 × 10{sup 11} molecule s{sup ?1} cm{sup ?3} of C{sub 2}H{sub 5}{sup •} (ethyl) and t-C{sub 4}H{sub 9}{sup •} (t-butyl) free radicals have been detected using VUV SPIMS at their molecular ion m/z 29 and 57, respectively, at 300 K.

  5. Physics with fast molecular-ion beams

    SciTech Connect (OSTI)

    Kanter, E.P.

    1980-01-01T23:59:59.000Z

    Fast (MeV) molecular-ion beams provide a unique source of energetic projectile nuclei which are correlated in space and time. The recognition of this property has prompted several recent investigations of various aspects of the interactions of these ions with matter. High-resolution measurements on the fragments resulting from these interactions have already yielded a wealth of new information on such diverse topics as plasma oscillations in solids and stereochemical structures of molecular ions as well as a variety of atomic collision phenomena. The general features of several such experiments will be discussed and recent results will be presented.

  6. Counting molecular-beam grown graphene layers

    SciTech Connect (OSTI)

    Plaut, Annette S. [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom)] [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Wurstbauer, Ulrich [Department of Physics, Columbia University, New York, New York 10027 (United States)] [Department of Physics, Columbia University, New York, New York 10027 (United States); Pinczuk, Aron [Department of Physics, Columbia University, New York, New York 10027 (United States) [Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Garcia, Jorge M. [MBE Lab, IMM-Instituto de Microelectronica de Madrid (CNM-CSIC), Madrid, E-28760 (Spain)] [MBE Lab, IMM-Instituto de Microelectronica de Madrid (CNM-CSIC), Madrid, E-28760 (Spain); Pfeiffer, Loren N. [Electrical Engineering Department, Princeton University, New Jersey 08544 (United States)] [Electrical Engineering Department, Princeton University, New Jersey 08544 (United States)

    2013-06-17T23:59:59.000Z

    We have used the ratio of the integrated intensity of graphene's Raman G peak to that of the silicon substrate's first-order optical phonon peak, accurately to determine the number of graphene layers across our molecular-beam (MB) grown graphene films. We find that these results agree well both, with those from our own exfoliated single and few-layer graphene flakes, and with the results of Koh et al.[ACS Nano 5, 269 (2011)]. We hence distinguish regions of single-, bi-, tri-, four-layer, etc., graphene, consecutively, as we scan coarsely across our MB-grown graphene. This is the first, but crucial, step to being able to grow, by such molecular-beam-techniques, a specified number of large-area graphene layers, to order.

  7. BEAM RELATED SYSTEMATICS IN HIGGS BOSON MASS MEASUREMENT

    E-Print Network [OSTI]

    BEAM RELATED SYSTEMATICS IN HIGGS BOSON MASS MEASUREMENT A.RASPEREZA DESY, Notkestrasse 85, D­22607#erential luminosity spectrum measurements and beam energy spread on the precision of the Higgs boson mass measurement possible impact of the beam related systematic errors on the Higgs boson mass measurement is discussed

  8. Yuan T. Lee's Crossed Molecular Beam Experiment

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del SolStrengtheningWildfires mayYuan T. Lee's Crossed Molecular Beam Experiment Home |

  9. BEAM RELATED SYSTEMATICS IN HIGGS BOSON MASS MEASUREMENT

    E-Print Network [OSTI]

    BEAM RELATED SYSTEMATICS IN HIGGS BOSON MASS MEASUREMENT A.RASPEREZA DESY, Notkestrasse 85, D-22607 and differential luminosity spectrum measurements and beam energy spread on the precision of the Higgs boson mass such as Higgs boson mass, decay branching fractions and production rate. However, most of these studies did

  10. Note: High density pulsed molecular beam for cold ion chemistry

    SciTech Connect (OSTI)

    Kokish, M. G.; Rajagopal, V.; Marler, J. P.; Odom, B. C., E-mail: b-odom@northwestern.edu [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

    2014-08-15T23:59:59.000Z

    A recent expansion of cold and ultracold molecule applications has led to renewed focus on molecular species preparation under ultrahigh vacuum conditions. Meanwhile, molecular beams have been used to study gas phase chemical reactions for decades. In this paper, we describe an apparatus that uses pulsed molecular beam technology to achieve high local gas densities, leading to faster reaction rates with cold trapped ions. We characterize the beam's spatial profile using the trapped ions themselves. This apparatus could be used for preparation of molecular species by reactions requiring excitation of trapped ion precursors to states with short lifetimes or for obtaining a high reaction rate with minimal increase of background chamber pressure.

  11. Molecular primary probe for secondary ion mass spectrometry of organics

    SciTech Connect (OSTI)

    Appelhans, A.D.; Delmore, J.E.

    1988-01-01T23:59:59.000Z

    In the course of development of a fast, highly focused neutral molecular primary beam probe for Secondary Ion Mass Spectrometry (SIMS), the question as to the relative efficiency of a molecule versus an atom for producing secondary ions of organic molecules was raised. Theoretical and experimental studies have indicated sputtering efficiency should increase as more energy is deposited near the surface. This would seem to be especially true when trying to sputter large organic molecules that must be desorbed from the surface with minimum molecular heating to remain intact. The kinetic energy of an SF6 molecule is distributed among 7 atoms and the SF6 molecule is large (geometrically) compared to an atom. Thus although at equivalent accelerating voltages an SF6/sup /minus// molecular ion (146 u) and a Cs atomic ion (133 u) deposit nearly the same amount of energy, the spatial distribution of this energy on surface will be quite different. The SF6 molecule will deposit more energy near the surface. To determine if this results in more efficient sputtering of molecules residing on the surface we have compared the SF6 molecular beam with a Cs atomic ion beam under organic static SIMS conditions. 5 refs., 1 tab.

  12. Molecular beam studies of reaction dynamics

    SciTech Connect (OSTI)

    Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01T23:59:59.000Z

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  13. The mean molecular mass of Titan's atmosphere

    E-Print Network [OSTI]

    Withers, Paul

    , Mars, Mars #12;Science Questions · Mean molecular mass (µ) -> Chemical composition · How did Titan form? · Current reservoirs of volatiles · Ethane/methane puddles/ocean · Thermal structure of atmosphere #12, delicate, etc ­ T/p sensors are simple, cheap, reliable · Is it possible to know µ based on simple

  14. Multiple-ion-beam time-of-flight mass spectrometer Andreas Rohrbacher and Robert E. Continettia)

    E-Print Network [OSTI]

    Continetti, Robert E.

    /ionization and the molecular ions of two different proteins myoglobin and lysozyme , created by matrix assisted laser,7 and matrix assisted desorption and ionization MALDI 8­11 have become avail- able to allow the mass the samples with a robot- driven capillary,15 a scanning ion beam,16 or spatial resolu- tion was achieved

  15. Apparatus and methods for continuous beam fourier transform mass spectrometry

    DOE Patents [OSTI]

    McLuckey, Scott A. (Oak Ridge, TN); Goeringer, Douglas E. (Oak Ridge, TN)

    2002-01-01T23:59:59.000Z

    A continuous beam Fourier transform mass spectrometer in which a sample of ions to be analyzed is trapped in a trapping field, and the ions in the range of the mass-to-charge ratios to be analyzed are excited at their characteristic frequencies of motion by a continuous excitation signal. The excited ions in resonant motions generate real or image currents continuously which can be detected and processed to provide a mass spectrum.

  16. DYNAMICS OF INFRARED MULTIPHOTON DISSOCIATION OF SF6 BY MOLECULAR BEAM METHOD

    E-Print Network [OSTI]

    Grant, E.R.

    2010-01-01T23:59:59.000Z

    molecular beam apparatus has been adapted to study the dynamics of excitationdynamics of molecular decomposition and the degree of vibrational excitation,

  17. Note: A helical velocity selector for continuous molecular beams

    SciTech Connect (OSTI)

    Szewc, Carola; Collier, James D.; Ulbricht, Hendrik [School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ (United Kingdom)

    2010-10-15T23:59:59.000Z

    We report on a modern realization of the classic helical velocity selector for gas phase particle beams. The device operates stably under high vacuum conditions at rotational frequencies limited only by commercial dc motor capabilities. Tuning the rotational frequency allows selective scanning over a broad velocity band. The width of the selected velocity distributions at full-width-half-maximum is as narrow as a few percent of the selected mean velocity and independent of the rotational speed of the selector. The selector generates low vibrational noise amplitudes comparable to mechanically damped state-of-the-art turbo-molecular pumps and is therefore compatible with vibration sensitive experiments like molecule interferometry.

  18. Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy A. J. Ptak, L. J-assisted molecular-beam epitaxy to study the dependence of oxygen incorporation on polarity and oxygen partial pressure. Oxygen incorporates at a rate ten times faster on nitrogen-polar GaN than on the Ga polarity

  19. Mass spectrometer with electron source for reducing space charge effects in sample beam

    DOE Patents [OSTI]

    Houk, Robert S.; Praphairaksit, Narong

    2003-10-14T23:59:59.000Z

    A mass spectrometer includes an ion source which generates a beam including positive ions, a sampling interface which extracts a portion of the beam from the ion source to form a sample beam that travels along a path and has an excess of positive ions over at least part of the path, thereby causing space charge effects to occur in the sample beam due to the excess of positive ions in the sample beam, an electron source which adds electrons to the sample beam to reduce space charge repulsion between the positive ions in the sample beam, thereby reducing the space charge effects in the sample beam and producing a sample beam having reduced space charge effects, and a mass analyzer which analyzes the sample beam having reduced space charge effects.

  20. Nuclear-mass dependence of azimuthal beam-helicity and beam-charge asymmetries in deeply virtual Compton scattering

    E-Print Network [OSTI]

    The HERMES collaboration; A. Airapetian

    2010-01-22T23:59:59.000Z

    The nuclear-mass dependence of azimuthal cross section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studiedfor hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.

  1. Fabrication of precision high quality facets on molecular beam epitaxy material

    DOE Patents [OSTI]

    Petersen, Holly E. (Tracy, CA); Goward, William D. (Antioch, CA); Dijaili, Sol P. (Moraga, CA)

    2001-01-01T23:59:59.000Z

    Fabricating mirrored vertical surfaces on semiconductor layered material grown by molecular beam epitaxy (MBE). Low energy chemically assisted ion beam etching (CAIBE) is employed to prepare mirrored vertical surfaces on MBE-grown III-V materials under unusually low concentrations of oxygen in evacuated etching atmospheres of chlorine and xenon ion beams. UV-stabilized smooth-surfaced photoresist materials contribute to highly vertical, high quality mirrored surfaces during the etching.

  2. Focusing of intense and divergent ion beams in a magnetic mass analyzer

    SciTech Connect (OSTI)

    Jianlin, Ke; Changgeng, Zhou; Rui, Qiu; Yonghong, Hu [Institute of Nuclear Physics and Chemistry, CAEP, 621900 Mianyang (China)

    2014-07-15T23:59:59.000Z

    A magnetic mass analyzer is used to determine the beam composition of a vacuum arc ion source. In the analyzer, we used the concentric multi-ring electrodes to focus the intense and divergent ion beams. We describe the principle, design, and the test results of the focusing device. The diameter of the beam profile is less than 20 mm when the accelerating voltage is 30 kV and the focusing voltage is about 2.0 kV. The focusing device has been successfully used in the magnetic mass analyzer to separate Ti{sup +}, Ti{sup 2+}, and Ti{sup 3+}.

  3. A crossed molecular beam study of the O(/sup 1/D/sub 2/)+CH/sub 4/ reaction

    SciTech Connect (OSTI)

    Casavecchia, P.; Buss, R.J.; Sibener, S.J.; Lee, Y.T.

    1980-12-15T23:59:59.000Z

    A cross molecular beam experiment was performed to study the O(/sup 1/D/sub 2/)+CH/sub 4/ reaction. The results show that hydrogen atom elimination reaction greatly exceeds molecular hydrogen elimination. (AIP)

  4. Mass Resolving Power Requirement for Molecular Formula Determination of Fossil Oils

    E-Print Network [OSTI]

    Weston, Ken

    Mass Resolving Power Requirement for Molecular Formula Determination of Fossil Oils Chang Samuel numbers based on the molecular formulas determined from accurate mass measurement.1 We have reported of molecular formulas of the components is reviewed. The resolving power required for overlapping compound

  5. CROSSED MOLECULAR BEAM STUDIES OF UN-IMOLECULAR REACTION DYNAMICS

    E-Print Network [OSTI]

    Buss, R.J.

    2010-01-01T23:59:59.000Z

    Cambridge, Mass. , 1972. R. J. Buss and Y. T. Lee, FaradayS. J. Sibener, R. J. Buss, and Y. T. Lee, Xlth Inter­S. J. Sibener, R. J. Buss, and Y. T. Lee, Rev. Sci.

  6. Growth of GaN on Ge(111) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lieten, R. R.; Degroote, S.; Cheng, K.; Leys, M.; Kuijk, M.; Borghs, G. [MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium) and ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium); ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2006-12-18T23:59:59.000Z

    The epitaxial growth of GaN on Ge is reported. The authors found that direct growth of GaN performs exceptionally well on Ge(111) with plasma assisted molecular beam epitaxy. A streaky reflection high energy electron diffraction pattern is observed during growth. X-ray diffraction showed a rocking curve full width at half maximum of only 371 arc sec for a 38 nm GaN layer and indicates an abrupt interface between the GaN and Ge. Secondary ion mass spectrometry shows limited diffusion of Ga atoms into the Ge substrate and Ge atoms into the GaN layers. Current-voltage measurements show rectifying behavior for n-GaN on p-Ge. Their results indicate that GaN growth on Ge does not require intermediate layers, allowing the Ge substrate to be used as back contact in vertical devices. A p-n junction formed between GaN and Ge can be used in heterojunction devices.

  7. /II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy

    E-Print Network [OSTI]

    Atwater, Harry

    /II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy Shouleh Nikzad, Selmer S. Wong, Channing C. Ahn, Aimee L. Smith molecular beam epitaxy system, using reflection electron energy loss spectroscopy, in conjunction

  8. GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY

    E-Print Network [OSTI]

    Feenstra, Randall

    1 GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY C. K. Inoki ABSTRACT We have explored the growth of GaN on porous SiC substrates by plasma-assisted molecular beam Ga droplets. Plan-view TEM observations indicate that the GaN layers grown on porous substrates

  9. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN single crystal by sodium fluxScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  10. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    doped MOCVD grown GaN on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN singleScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  11. Mass Spectral Molecular Networking of Living Microbial Colonies

    SciTech Connect (OSTI)

    Watrous, Jeramie D.; Roach, Patrick J.; Alexandrov, Theodore; Heath, Brandi S.; Yang, Jane Y.; Kersten, Roland; vander Voort, Menno; Pogliano, Kit; Gross, Harald; Raaijmakers, Jos M.; Moore, Bradley S.; Laskin, Julia; Bandeira, Nuno; Dorrestein, Pieter C.

    2012-06-26T23:59:59.000Z

    Integrating the governing chemistry with the genomics and phenotypes of microbial colonies has been a "holy grail" in microbiology. This work describes a highly sensitive, broadly applicable, and costeffective approach that allows metabolic profiling of live microbial colonies directly from a Petri dish without any sample preparation. Nanospray desorption electrospray ionization mass spectrometry (MS), combined with alignment of MS data and molecular networking, enabled monitoring of metabolite production from live microbial colonies from diverse bacterial genera, including Bacillus subtilis, Streptomyces coelicolor, Mycobacterium smegmatis, and Pseudomonas aeruginosa. This work demonstrates that, by using these tools to visualize small molecular changes within bacterial interactions, insights can be gained into bacterial developmental processes as a result of the improved organization of MS/MS data. To validate this experimental platform, metabolic profiling was performed on Pseudomonas sp. SH-C52, which protects sugar beet plants from infections by specific soil-borne fungi [R. Mendes et al. (2011) Science 332:1097–1100]. The antifungal effect of strain SHC52 was attributed to thanamycin, a predicted lipopeptide encoded by a nonribosomal peptide synthetase gene cluster. Our technology, in combination with our recently developed peptidogenomics strategy, enabled the detection and partial characterization of thanamycin and showed that it is amonochlorinated lipopeptide that belongs to the syringomycin family of antifungal agents. In conclusion, the platform presented here provides a significant advancement in our ability to understand the spatiotemporal dynamics of metabolite production in live microbial colonies and communities.

  12. Production of pulsed, mass-selected beams of metal and semiconductor clusters

    SciTech Connect (OSTI)

    Kamalou, Omar; Rangama, Jimmy; Ramillon, Jean-Marc; Guinement, Patrick; Huber, Bernd A. [CIMAP, CEA-CNRS-ENSICaen-UCBN, Bv. Henry Becquerel (B.P. 5133), F-14070 Caen Cedex 05 (France)

    2008-06-15T23:59:59.000Z

    We report on the development of a beam line for mass-selected metal and semiconductor clusters. The cluster source combines the principles of plasma sputtering and gas condensation. Both techniques together allow to produce clusters in a wide size range. With the aid of a time-of-flight system, small clusters (i.e., Cu{sub n}{sup +}, n<100) are selected and pure beams containing only one cluster size are provided. For large clusters (containing several thousands of atoms), a beam with a narrow size distribution is obtained. A 90 deg. quadrupole deviator is used to separate charged clusters from neutral ones.

  13. Investigation of Supersonic Molecular Beam Injection into the HL-1M Tokamak

    SciTech Connect (OSTI)

    Yao Lianghua; Feng Beibin; Dong Jaifu; Zhou Yan; Cui Zhengying; Cao Jianyong; Tang Nianyi; Feng Zhen; Xiao Zhenggui; Song Xianming; Hong Wenyu; Wang, Enyao; Liu Yong [Southwestern Institute of Physics (China)

    2002-07-15T23:59:59.000Z

    As a new fueling method, supersonic molecular beam injection (SMBI) has been successfully developed and used in the HL-1M tokamak and HT-7 superconducting tokamak. SMBI can enhance penetration depth and fueling efficiency. It can be considered a significant improvement over conventional gas puffing. In recent experiments, hydrogen clusters have been found in the beam produced by high working gas pressure. The hydrogen particles of the beam have penetrated into the plasma center region, in which the average velocity of the injected beam is >1200 m/s. The rate of increase of electron density for SMBI, d[bar]n{sub e}/dt, approaches that of small ice pellet injection (PI). The plasma density increases step by step after multipulse SMBI, just as with the effects of multipellet fueling. Comparison of fueling effects was made between SMBI and small ice PI in the same shot of ohmic discharge in HL-1M.

  14. High performance double pulse doped pseudomorphic AlGaAs/InGaAs transistors grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Hoke, W.E.; Lyman, P.S.; Labossier, W.H.; Brierley, S.K.; Hendriks, H.T.; Shanfield, S.R.; Aucoin, L.M.; Kazior, T.E. [Raytheon Research Division, Lexington, MA (United States)] [Raytheon Research Division, Lexington, MA (United States)

    1992-05-01T23:59:59.000Z

    Double pulse doped AlGaAs/InGaAs pseudomorphic high electron mobility transistors have been grown by molecular-beam epitaxy on GaAs substrates. Hall mobilities in excess of 7100 cm{sup 2}/V s at 300 K and 25000 cm{sup 2}/V s at 77 K are obtained with a sheet density of 3 x 10{sup 12} cm{sup {minus}2}. Photoluminescence measurements indicate that two electronic subbands are occupied, and the subband energies are determined. The doping pulses are resolved in secondary ion mass spectrometry measurements. Using a double recess process, transistors have been fabricated that have produced state of the art microwave performance. At 10 GHz a 1.2 mm device has simultaneously achieved a power added efficiency of 70%, output power of 0.97 W, and gain of 10 dB. 17 refs., 5 figs., 1 tab.

  15. (In,Mn)As quantum dots: Molecular-beam epitaxy and optical properties

    SciTech Connect (OSTI)

    Bouravleuv, A. D., E-mail: bour@mail.ioffe.ru; Nevedomskii, V. N. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Ubyivovk, E. V. [St. Petersburg State University (Russian Federation)] [St. Petersburg State University (Russian Federation); Sapega, V. F. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Khrebtov, A. I. [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation)] [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation); Samsonenko, Yu. B.; Cirlin, G. E.; Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-08-15T23:59:59.000Z

    Self-assembled (In,Mn)As quantum dots are synthesized by molecular-beam epitaxy on GaAs (001) substrates. The experimental results obtained by transmission electron microscopy show that doping of the central part of the quantum dots with Mn does not bring about the formation of structural defects. The optical properties of the samples, including those in external magnetic fields, are studied.

  16. Assessment of molecular effects on neutrino mass measurements from tritium beta decay

    E-Print Network [OSTI]

    Bodine, L I; Robertson, R G H

    2015-01-01T23:59:59.000Z

    The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino mass-squared values are consistent with zero instead of being significantly negative. On the other hand, the calculated molecular final-state branching ratios are in tension with dissociation experiments performed in the 1950s. We re-examine the theory of the final-state spectrum of molecular tritium decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the vibrational- and rotational-state distribution i...

  17. Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates

    E-Print Network [OSTI]

    Steckl, Andrew J.

    Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates R. Birkhahn and A grown by MBE on sapphire substrates. In this letter, we report on Er-doped GaN growth experiments on Si Er-doped -GaN thin films grown on Si 111 . The GaN was grown by molecular beam epitaxy using solid

  18. Characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Lo, Ikai; Pang, Wen-Yuan; Hsu, Yu-Chi; Hsieh, Chia-Ho; Shih, Cheng-Hung; Chou, Mitch M. C. [Department of Physics and Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Chen, Wen-Yen; Hsu, Tzu-Min [Department of Physics, National Central University, Jhong-li, Taoyuan 32001, Taiwan (China); Hsu, Gary Z. L. [United Crystal Corporation, No.243-3, Wenshan, 36061, Miaoli, Taiwan (China)

    2013-06-15T23:59:59.000Z

    The characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy on LiAlO{sub 2} substrate was studied by cathodoluminescence and photoluminescence measurements. We demonstrated that the cathodoluminescence from oblique semi-polar surfaces of mushroom-shaped GaN was much brighter than that from top polar surface due to the reduction of polarization field on the oblique semi-polar surfaces. It implies that the oblique semi-polar surface is superior for the light-emitting surface of wurtzite nano-devices.

  19. Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001)

    E-Print Network [OSTI]

    Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001) Wenzhi Lin, Jeongihm], but not hexagonal (wurtzite) GaN, a fast-developing semiconductor material with important technological applicationsN on wurtzite GaN(0001), by employing e-beam evaporation in an ultra-high vacuum MBE cham- ber. The FeN films

  20. Synchrotron based mass spectrometry to investigate the molecular properties of mineral-organic associations

    SciTech Connect (OSTI)

    Liu, Suet Yi; Kleber, Markus; Takahashi, Lynelle K.; Nico, Peter; Keiluweit, Marco; Ahmed, Musahid

    2013-04-01T23:59:59.000Z

    Soil organic matter (OM) is important because its decay drives life processes in the biosphere. Analysis of organic compounds in geological systems is difficult because of their intimate association with mineral surfaces. To date there is no procedure capable of quantitatively separating organic from mineral phases without creating artifacts or mass loss. Therefore, analytical techniques that can (a) generate information about both organic and mineral phases simultaneously and (b) allow the examination of predetermined high-interest regions of the sample as opposed to conventional bulk analytical techniques are valuable. Laser Desorption Synchrotron Postionization (synchrotron-LDPI) mass spectrometry is introduced as a novel analytical tool to characterize the molecular properties of organic compounds in mineral-organic samples from terrestrial systems, and it is demonstrated that when combined with Secondary Ion Mass Spectrometry (SIMS), can provide complementary information on mineral composition. Mass spectrometry along a decomposition gradient in density fractions, verifies the consistency of our results with bulk analytical techniques. We further demonstrate that by changing laser and photoionization energies, variations in molecular stability of organic compounds associated with mineral surfaces can be determined. The combination of synchrotron-LDPI and SIMS shows that the energetic conditions involved in desorption and ionization of organic matter may be a greater determinant of mass spectral signatures than the inherent molecular structure of the organic compounds investigated. The latter has implications for molecular models of natural organic matter that are based on mass spectrometric information.

  1. Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

    SciTech Connect (OSTI)

    Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

    2014-03-01T23:59:59.000Z

    We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

  2. Lattice constant and substitutional composition of GeSn alloys grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Bhargava, Nupur; Coppinger, Matthew; Prakash Gupta, Jay; Kolodzey, James [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States)] [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States); Wielunski, Leszek [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)] [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)

    2013-07-22T23:59:59.000Z

    Single crystal epitaxial Ge{sub 1?x}Sn{sub x} alloys with atomic fractions of tin up to x = 0.145 were grown by solid source molecular beam epitaxy on Ge (001) substrates. The Ge{sub 1?x}Sn{sub x} alloys formed high quality, coherent, strained layers at growth temperatures below 250 °C, as shown by high resolution X-ray diffraction. The amount of Sn that was on lattice sites, as determined by Rutherford backscattering spectrometry channeling, was found to be above 90% substitutional in all alloys. The degree of strain and the dependence of the effective unstrained bulk lattice constant of Ge{sub 1?x}Sn{sub x} alloys versus the composition of Sn have been determined.

  3. High quality molecular beam epitaxial growth on patterned GaAs substrates

    SciTech Connect (OSTI)

    Smith, J.S.; Derry, P.L.; Margalit, S.; Yariv, A.

    1985-10-01T23:59:59.000Z

    In this letter we describe a procedure for high quality molecular beam epitaxy (MBE) growth over finely patterned GaAs substrates which is suitable for device fabrication requiring lateral definition of small (approx.1--2 ..mu..m) dimension. This method was used for the fabrication of index guided laser arrays. Yields of individual lasers exceeded 90%, and thresholds were uniform to 10%. Temperature and flux ratio dependence of faceting during MBE growth over patterned substrates is shown for temperatures ranging from 580 to 700 /sup 0/C and for As/Ga flux ratios from 1.4:1 to 4:1. The real index guided structure, which can be formed by a single MBE growth over a ridged substrate, is discussed. This technique should prove useful in the fabrication of devices which take advantage of unique features formed during regrowth by MBE.

  4. Fe-doped InN layers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Wang Xinqiang; Liu Shitao; Ma Dingyu; Zheng Xiantong; Chen Guang; Xu Fujun; Tang Ning; Shen Bo [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Zhang Peng; Cao Xingzhong; Wang Baoyi [State Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Huang Sen; Chen, Kevin J. [Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology (Hong Kong); Zhou Shengqiang [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01314 Dresden (Germany); Yoshikawa, Akihiko [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2012-10-22T23:59:59.000Z

    Iron(Fe)-doped InN (InN:Fe) layers have been grown by molecular beam epitaxy. It is found that Fe-doping leads to drastic increase of residual electron concentration, which is different from the semi-insulating property of Fe-doped GaN. However, this heavy n-type doping cannot be fully explained by doped Fe-concentration ([Fe]). Further analysis shows that more unintentionally doped impurities such as hydrogen and oxygen are incorporated with increasing [Fe] and the surface is degraded with high density pits, which probably are the main reasons for electron generation and mobility reduction. Photoluminescence of InN is gradually quenched by Fe-doping. This work shows that Fe-doping is one of good choices to control electron density in InN.

  5. Molecular-beam epitaxial growth of boron-doped GaAs films

    SciTech Connect (OSTI)

    Hoke, W.E.; Lemonias, P.J.; Weir, D.G. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    GaAs films doped with boron in the 10{sup 20} cm{sup {minus}3} range were grown by solid source molecular-beam epitaxy. Lattice contractions were observed in x-ray double crystal spectra. Substitutional boron concentrations up to 1.7x10{sup 20} cm{sup {minus}3} were obtained with narrow x-ray linewidths and specular surface morphology. For a given boron flux, the substitutional concentration was dependent on growth temperature. P-type conductivity due to boron incorporation was measured in the films with hole concentration reaching 1x10{sup 19} cm{sup {minus}3}. The lattice contractions exhibited good thermal stability for rapid thermal anneals. 10 refs., 3 figs., 2 tabs.

  6. Structure and electrical properties of polycrystalline SiGe films grown by molecular beam deposition

    SciTech Connect (OSTI)

    Chistokhin, I. B., E-mail: igor@thermo.isp.nsc.ru; Gutakovskii, A. K.; Deryabin, A. S. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Division (Russian Federation)

    2007-03-15T23:59:59.000Z

    The structural and electrical properties of polycrystalline Si{sub 0.5}Ge{sub 0.5} films 150 nm thick grown by molecular beam deposition at temperatures of 200-550 deg. C on silicon substrates coated with amorphous layers of silicon oxynitride were studied. It is shown that the films consist of a mixture of amorphous and polycrystalline phases. The amorphous phase fraction decreases from {approx}50% in films deposited at 200 deg. C to zero in films grown at 550 deg. C. Subsequent 1-h annealing at a temperature of 550 deg. C results in complete solid-phase crystallization of all films. The electron transport of charge carriers in polycrystalline films occurs by the thermally activated mechanism associated with the energy barrier of {approx}0.2 eV at grain boundaries. Barrier lowering upon additional annealing of SiGe films correlates with an increase in the average grain size.

  7. Antimony segregation in stressed SiGe heterostructures grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Drozdov, M. N.; Novikov, A. V.; Yurasov, D. V., E-mail: Inquisitor@ipm.sci.nnov.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2013-11-15T23:59:59.000Z

    The effects of the growth temperature, composition, and elastic strains in separate layers on the segregation of antimony are studied experimentally for stressed SiGe structures grown by molecular beam epitaxy. It is established that the growth conditions and parameters of the structures exert an interrelated influence on the segregation of Sb: the degree of the influence of the composition and elastic stresses in the SiGe layers on Sb segregation depends on the growth temperature. It is shown that usage of a method previously proposed by us for the selective doping of silicon structures with consideration for the obtained dependences of Sb segregation on the growth conditions and parameters of the SiGe layers makes it possible to form SiGe structures selectively doped with antimony.

  8. Electrical characterization of ensemble of GaN nanowires grown by the molecular beam epitaxy technique

    SciTech Connect (OSTI)

    Kolkovsky, Vl. [Technische Universität Dresden, 01062 Dresden (Germany)] [Technische Universität Dresden, 01062 Dresden (Germany); Zytkiewicz, Z. R.; Sobanska, M.; Klosek, K. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)] [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)

    2013-08-26T23:59:59.000Z

    High quality Schottky contacts are formed on GaN nanowires (NWs) structures grown by the molecular beam epitaxy technique on Si(111) substrate. The current-voltage characteristics show the rectification ratio of about 10{sup 3} and the leakage current of about 10{sup ?4} A/cm{sup 2} at room temperature. From the capacitance-voltage measurements the free carrier concentration in GaN NWs is determined as about 10{sup 16} cm{sup ?3}. Two deep levels (H200 and E280) are found in the structures containing GaN NWs. H200 is attributed to an extended defect located at the interface between the substrate and SiN{sub x} or near the sidewalls at the bottom of the NWs whereas E280 is tentatively assigned to a gallium-vacancy- or nitrogen interstitials-related defect.

  9. Assessment of molecular effects on neutrino mass measurements from tritium beta decay

    E-Print Network [OSTI]

    L. I. Bodine; D. S. Parno; R. G. H. Robertson

    2015-02-12T23:59:59.000Z

    The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino mass-squared values are consistent with zero instead of being significantly negative. On the other hand, the calculated molecular final-state branching ratios are in tension with dissociation experiments performed in the 1950s. We re-examine the theory of the final-state spectrum of molecular tritium decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the vibrational- and rotational-state distribution in the ground electronic state. General features can be reproduced quantitatively from considerations of kinematics and zero-point motion. We summarize the status of validation efforts and suggest means for resolving the apparent discrepancy in dissociation rates.

  10. AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates

    E-Print Network [OSTI]

    Manfra, Michael J.

    PS-4 AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates Nils ABSTRACT Molecular Beam Epitaxy of GaN and related alloys is becoming a rival to the more established, and HVPE SI-GaN templates on sapphire. While sapphire and SI-Sic are established substrates for the growth

  11. Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M. FEENSTRA

    E-Print Network [OSTI]

    Feenstra, Randall

    years as a substrate for both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy of GaN of the substrate preparation and growth technique. Experimental GaN films of typically 1 mm thickness are deposited1 Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M

  12. Polarity inversion of N-face GaN by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Wong, M.H.; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Wu Feng; Mates, Thomas E.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2008-11-01T23:59:59.000Z

    The polarity of GaN grown by plasma-assisted molecular beam epitaxy was inverted from N-face to Ga-face by simultaneously exposing the surface to Mg and activated N fluxes during a growth interruption at a reduced substrate temperature. Growth studies suggested that a Mg{sub x}N{sub y} compound was responsible for inverting the crystal. The change in polarity was verified in situ by reflection high energy electron diffraction via GaN surface reconstructions, and ex situ by convergent beam electron diffraction and KOH etch studies. The surface of the inverted material showed smooth step flow features. Ga-face high electron mobility transistors with good dc and small signal performance were fabricated on the inverted epilayers. A drain-source current of 0.84 A/mm was measured at a gate-source voltage of +1 V. Current-gain cutoff and maximum oscillation frequencies of 22 and 53 GHz, respectively, were measured in these devices. The device performance is similar to that of Ga-face transistors with comparable dimensions.

  13. Molecular beam epitaxy of n-type ZnS: A wide band gap emitter for heterojunction PV devices

    E-Print Network [OSTI]

    Atwater, Harry

    Molecular beam epitaxy of n-type ZnS: A wide band gap emitter for heterojunction PV devices Jeffrey and AZO transparent conductive oxides did not. Applications to novel PV devices incorporating low electron-ray diffraction, zinc compounds. I. INTRODUCTION The growing interest in scalable, thin-film photovoltaics (PV

  14. A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    as a function of substrate temperature and dopant flux for Ga-polarity and N-polarity GaN. Incorporation GaN templates on (0001) sapphire substrates. The doped layers were grown at a rate of 0.25 µmA Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam

  15. Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity York, 12222 Abstract: We have grown GaN on porous SiC substrates and studied the effect of substrate show that the GaN film grown on porous substrates contains open tubes and a low dislocation density

  16. The chemistry of Si{sub 3}N{sub 4} and Si deposition studied using molecular beam techniques

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.; Breiland, W.G.

    1992-08-01T23:59:59.000Z

    Molecular beam techniques can be used to obtain valuable kinetic information for the chemistry of high temperature deposition processes. Molecular beam measurements of Si{sub 3}N{sub 4} deposited from SiF{sub 4} and NH{sub 3} have shown that the CVD reactor chemistry is dominated by surface reactions of the starting gases. Using a beam of heated silane, it is shown that the translational and internal energy of the gas does not influence its surface reactivity in silicon CVD. The IRIS (Imaging of Radicals Interacting with Surfaces) technique for measuring the surface reactivity of radicals during deposition is also discussed with examples (SiH, SiO and NH). 5 refs., 4 figs.

  17. The chemistry of Si sub 3 N sub 4 and Si deposition studied using molecular beam techniques

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.; Breiland, W.G.

    1992-01-01T23:59:59.000Z

    Molecular beam techniques can be used to obtain valuable kinetic information for the chemistry of high temperature deposition processes. Molecular beam measurements of Si{sub 3}N{sub 4} deposited from SiF{sub 4} and NH{sub 3} have shown that the CVD reactor chemistry is dominated by surface reactions of the starting gases. Using a beam of heated silane, it is shown that the translational and internal energy of the gas does not influence its surface reactivity in silicon CVD. The IRIS (Imaging of Radicals Interacting with Surfaces) technique for measuring the surface reactivity of radicals during deposition is also discussed with examples (SiH, SiO and NH). 5 refs., 4 figs.

  18. Method for Characterization of Low Molecular Weight Organic Acids in Atmospheric Aerosols Using Ion Chromatography Mass

    E-Print Network [OSTI]

    Dickerson, Russell R.

    spectrometry (ESI-MS).17-19 ESI has the advantage of being compatible with polar mobile phases, and softMethod for Characterization of Low Molecular Weight Organic Acids in Atmospheric Aerosols Using Ion Chromatography Mass Spectrometry Lacey C. Brent,* Jessica L. Reiner, Russell R. Dickerson, and Lane C. Sander

  19. DOI: 10.1002/asia.201000560 Supramolecular Synthons in Designing Low Molecular Mass Gelling Agents

    E-Print Network [OSTI]

    Raghavan, Srinivasa

    to generate supramolec- ular functional materials. To use supramolecular synthons successfully in designing, testify to the power of supramolecular synthons.[3] Among the various supramolecular functional materials#12;DOI: 10.1002/asia.201000560 Supramolecular Synthons in Designing Low Molecular Mass Gelling

  20. Elemental Speciation by Parallel Elemental and Molecular Mass Spectrometry and Peak Profile

    E-Print Network [OSTI]

    Derry, Louis A.

    -amino acid standards (0.005-15 ppm as Se). The molecular MS (atmospheric pressure chemical ionization time spectrometry (ICPMS) or atmospheric pressure ionization mass spectrometry (API-MS, e.g., atmospheric pressure by HPLC-ICPMS requires retention index matching with an appropriate standard. Such an approach may yield

  1. Radiation environment simulations at the Tevatron, studies of the beam profile and measurement of the Bc meson mass

    SciTech Connect (OSTI)

    Nicolas, Ludovic Y.

    2005-09-01T23:59:59.000Z

    The description of a computer simulation of the CDF detector at Fermilab and the adjacent accelerator parts is detailed, with MARS calculations of the radiation background in various elements of the model due to the collision of beams and machine-related losses. Three components of beam halo formation are simulated for the determination of the principal source of radiation background in CDF due to beam losses. The effect of a collimator as a protection for the detector is studied. The simulation results are compared with data taken by a CDF group. Studies of a 150 GeV Tevatron proton beam are performed to investigate the transverse diffusion growth and distribution. A technique of collimator scan is used to scrape the beam under various experimental conditions, and computer programs are written for the beam reconstruction. An average beam halo growth speed is given and the potential of beam tail reconstruction using the collimator scan is evaluated. A particle physics analysis is conducted in order to detect the B{sub c} {yields} J/{psi}{pi} decay signal with the CDF Run II detector in 360 pb{sup -1} of data. The cut variables and an optimization method to determine their values are presented along with a criterion for the detection threshold of the signal. The mass of the B{sub c} meson is measured with an evaluation of the significance of the signal.

  2. Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy

    SciTech Connect (OSTI)

    Krockenberger, Yoshiharu; Karimoto, Shin-ichi; Yamamoto, Hideki; Semba, Kouich [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

    2012-10-15T23:59:59.000Z

    We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 Degree-Sign C. TiN films grown at 720 Degree-Sign C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T{sub c}) is well above 5 K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field ({mu}{sub 0}H{sub c2}) as well as the corresponding coherence length ({xi}{sub GL}) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length Script-Small-L Almost-Equal-To 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films.

  3. Pellet and Molecular Beam Injection Fueling on the HL-1M Tokamak

    SciTech Connect (OSTI)

    Xiao Zhenggui; Li Bo; Li Li; Liu Dequan; Yao Lianghua; Dong Jiafu; Guo Gancheng; Deng Zhongchao; Zheng Yinjia; Hong Wenyu; Yan Longwen; Liu Yi; Liu Yong; Wang, Enyao [Southwestern Institute of Physics (China)

    2003-01-15T23:59:59.000Z

    The Eight-shot Pellet Injector (EPI) and Molecular Beam Injector (MBI) as new plasma fueling methods have been developed and installed on the HL-1M tokamak for fueling experiments. The main structures and characteristics of the fueling device and the typical fueling experimental results with EPI and the MBI are reported. In these experiments, typical responses of plasma in discharges with PI and MBI are the peaked density profile Q{sub n} n{sub e}(0)/<(n{sub e})> of >1.65 for MBI and of 2 for PI. The improvement of confinement time E is usually better than 10 to 30% of Gas Puffing (GP) discharge in the same operation condition. In addition, the penetration depth and deposition region of fueling particles, the variance of soft X-ray sawteeth, the rotation and flow of plasma in edge region as well as the photographing of ablation clouds with PI and MBI are compared and presented in this paper.

  4. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited)

    SciTech Connect (OSTI)

    Andrieu, S., E-mail: stephane.andrieu@univ-lorraine.fr; Bonell, F.; Hauet, T.; Montaigne, F. [Institut Jean Lamour, Nancy University/CNRS, Bd des Aiguillettes, BP239, 54506 Vandoeuvre-lès-Nancy (France); Calmels, L.; Snoeck, E. [CEMES, CNRS and Toulouse University, 29 rue Jeanne Marvig, 31055 Toulouse (France); Lefevre, P.; Bertran, F. [Synchrotron SOLEIL-CNRS, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette cedex (France)

    2014-05-07T23:59:59.000Z

    The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe{sub 1?x}V{sub x} electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe{sub 1?X}Co{sub x}/MgO/Fe{sub 1?X}Co{sub x} (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty ?1 minority spin state towards the Fermi level.

  5. InAlN/GaN Bragg reflectors grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM, Universidad Politecnica de Madrid, Avda Complutense s/n, 28040 Madrid (Spain); Hosseini, D.; Peiro, F. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, SCT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2010-12-01T23:59:59.000Z

    We report on molecular beam epitaxy growth and characterization of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs), with peak reflectivity centered around 400 nm. Thanks to the well tuned ternary alloy composition, crack-free surfaces have been obtained, as confirmed by both optical and transmission electron microscopy (TEM). Their good periodicity and well-defined interfaces have been confirmed by both x-ray diffraction and TEM measurements. Peak reflectivity values as high as 60% with stop bands of 30 nm have been demonstrated. Optical measurements revealed that discrepancy between the obtained (60%) and the theoretically expected ({approx}75%) reflectivity is a consequence of significant residual absorption ({approx}35%). TEM measurements revealed the coexistence of zinc-blende and wurtzite phases, as well as planar defects, mainly in GaN. These defects are suggested as the potential source of the undesired absorption and/or scattering effects that lowered the DBRs' peak reflectivity.

  6. NO-assisted molecular-beam epitaxial growth of nitrogen substituted EuO

    SciTech Connect (OSTI)

    Wicks, R. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada); Altendorf, S. G.; Caspers, C.; Kierspel, H.; Sutarto, R. [II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Tjeng, L. H. [II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany); Damascelli, A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada); Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)

    2012-04-16T23:59:59.000Z

    We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO{sub 1-x}N{sub x} films with good control over the films' nitrogen concentration. In situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu{sup 3+}4f{sup 6} and a corresponding decrease in the number of Eu{sup 2+}4f{sup 7}, indicating that nitrogen is being incorporated in its 3{sup -} oxidation state. While small amounts of Eu{sup 3+} in over-oxidized Eu{sub 1-{delta}}O thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu{sup 3+} in EuO{sub 1-x}N{sub x} still allows the ferromagnetic phase to exist with an unaffected T{sub c}, thus providing an ideal model system to study the interplay between the magnetic f{sup 7} (J = 7/2) and the non-magnetic f{sup 6} (J = 0) states close to the Fermi level.

  7. ARE MOLECULAR OUTFLOWS AROUND HIGH-MASS STARS DRIVEN BY IONIZATION FEEDBACK?

    SciTech Connect (OSTI)

    Peters, Thomas; Klessen, Ralf S. [Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Zentrum fuer Astronomie, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Klaassen, Pamela D. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Mac Low, Mordecai-Mark [Department of Astrophysics, American Museum of Natural History, 79th Street at Central Park West, New York, NY 10024-5192 (United States); Banerjee, Robi, E-mail: tpeters@physik.uzh.ch [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)

    2012-11-20T23:59:59.000Z

    The formation of massive stars exceeding 10 M {sub Sun} usually results in large-scale molecular outflows. Numerical simulations, including ionization, of the formation of such stars show evidence for ionization-driven molecular outflows. Here we examine whether the outflows seen in these models reproduce the observations. We compute synthetic ALMA and CARMA maps of CO emission lines of the outflows, and compare their signatures to existing single-dish and interferometric data. We find that the ionization-driven models can only reproduce weak outflows around high-mass star-forming regions. We argue that expanding H II regions probably do not represent the dominant mechanism for driving observed outflows. We suggest instead that observed outflows are driven by the collective action of the outflows from the many lower-mass stars that inevitably form around young massive stars in a cluster.

  8. High-frequency modulation of AlGaAs/GaAs lasers grown on Si substrate by molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, H.Z.; Paslaski, J.; Yariv, A.; Morkoc, H.

    1988-02-22T23:59:59.000Z

    We report on the frequency response of quantum well lasers on Si substrates grown by molecular beam epitaxy. Ridge waveguide lasers of 10 ..mu..m x 380 ..mu..m having threshold currents as low as 40 mA were used in this study. Measurements were performed up to a frequency of 4.5 GHz with a resultant modulation corner frequency of 2.5 GHz when the laser was operated about 20% above the threshold.

  9. Impact of substrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Armstrong, A; Poblenz, C; Green, D S; Mishra, U K; Speck, J S; Ringel, S A

    2006-01-01T23:59:59.000Z

    GaN grown by molecular beam epitaxy and codoped with carbon and silicon were investigated for substratesubstrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN

  10. Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen

    E-Print Network [OSTI]

    York, Robert A.

    Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen Materials Department March 2005 Titanium dioxide TiO2, with the rutile structure was grown on 0001 oriented GaN and 0001 Al0.33Ga0.67N/GaN heterostructure field effect transistor HFET structures by molecular beam epitaxy. X

  11. Impact of growth conditions on vacancy-type defects in silicon-germanium structures grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Shoukri, Kareem M.; Haddara, Yaser M.; Knights, A.P.; Coleman, P.G. [Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario L8S 4K1 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Physics, University of Bath, Bath BA2 7AY (United Kingdom)

    2005-03-28T23:59:59.000Z

    Silicon-germanium layers of either 200 nm or 250 nm have been grown via molecular-beam epitaxy (MBE) on p-type (001) silicon substrates. Each sample was prepared using a unique combination of buffer-layer type, buffer-layer growth temperature, and layer Ge content. Vacancy-type defects have been identified using beam-based positron annihilation. These results, combined with those from previous work, indicate the size and concentration of defects in MBE grown SiGe layers depend strongly upon the buffer-layer growth temperature (T). For T>500 deg. C vacancy point defect concentrations are below the detectable limit of the measurement. As T is decreased to 300 deg. C, vacancy clusters form in the buffer layer and point defects appear in the SiGe film, even for a SiGe growth temperature of 500 deg. C.

  12. Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Rolland, Chloe; Coinon, Christophe; Wallart, Xavier; Leturcq, Renaud [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France)] [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France); Caroff, Philippe [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France) [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)

    2013-06-03T23:59:59.000Z

    We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.

  13. Optical properties of strain-free AlN nanowires grown by molecular beam epitaxy on Si substrates

    SciTech Connect (OSTI)

    Wang, Q.; Zhao, S.; Connie, A. T.; Shih, I.; Mi, Z., E-mail: zetian.mi@mcgill.ca [Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9 (Canada); Gonzalez, T.; Andrews, M. P. [Department of Chemistry, McGill University, 801 Sherbrooke St West, Montreal, Quebec H3A 0B8 (Canada); Du, X. Z.; Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-06-02T23:59:59.000Z

    The optical properties of catalyst-free AlN nanowires grown on Si substrates by molecular beam epitaxy were investigated. Such nanowires are nearly free of strain, with strong free exciton emission measured at room temperature. The photoluminescence intensity is significantly enhanced, compared to previously reported AlN epilayer. Moreover, the presence of phonon replicas with an energy separation of ?100?meV was identified to be associated with the surface-optical phonon rather than the commonly reported longitudinal-optical phonon, which is further supported by the micro-Raman scattering experiments.

  14. Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO{sub 2{+-}x}

    SciTech Connect (OSTI)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2012-12-01T23:59:59.000Z

    We have conducted a detailed thin film growth structure of oxygen engineered monoclinic HfO{sub 2{+-}x} grown by reactive molecular beam epitaxy. The oxidation conditions induce a switching between (111) and (002) texture of hafnium oxide. The band gap of oxygen deficient hafnia decreases with increasing amount of oxygen vacancies by more than 1 eV. For high oxygen vacancy concentrations, defect bands form inside the band gap that induce optical transitions and p-type conductivity. The resistivity changes by several orders of magnitude as a function of oxidation conditions. Oxygen vacancies do not give rise to ferromagnetic behavior.

  15. Residual and nitrogen doping of homoepitaxial nonpolar m-plane ZnO films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Taienoff, D.; Deparis, C.; Teisseire, M.; Morhain, C. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique (CRHEA-CNRS), Rue B. Gregory, F-06560 Valbonne Sophia Antipolis (France); Al-Khalfioui, M.; Vinter, B.; Chauveau, J.-M. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique (CRHEA-CNRS), Rue B. Gregory, F-06560 Valbonne Sophia Antipolis (France); Universite de Nice Sophia Antipolis, Parc Valrose F-06103 Nice (France)

    2011-03-28T23:59:59.000Z

    We report the homoepitaxial growth by molecular beam epitaxy of high quality nonpolar m-plane ZnO and ZnO:N films over a large temperature range. The nonintentionally doped ZnO layers exhibit a residual doping as low as {approx}10{sup 14} cm{sup -3}. Despite an effective incorporation of nitrogen, p-type doping was not achieved, ZnO:N films becoming insulating. The high purity of the layers and their low residual n-type doping evidence compensation mechanisms in ZnO:N films.

  16. Room temperature infrared photoresponse of self assembled Ge/Si (001) quantum dots grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Singha, R. K.; Manna, S.; Das, S.; Dhar, A.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2010-06-07T23:59:59.000Z

    We report on the observation of intraband near infrared (approx3.1 mum) and mid infrared (approx6.2 mum) photocurrent response at room temperature using Ge/Si self-assembled quantum dots grown by molecular beam epitaxy. Due to the bimodal size distribution and SiGe intermixing, distinguishable photoluminescence transitions are observed at 10 K, below and above the optical band gap of bulk Ge. The observed redshift in photocurrent with increasing temperature has been explained by the excitonic electric field originated due to infrared excitation at low temperatures. A good correlation between the spectral photocurrent response and photoluminescence of the quantum dots has been established.

  17. Transition between wurtzite and zinc-blende GaN: An effect of deposition condition of molecular-beam epitaxy

    SciTech Connect (OSTI)

    Shi, B. M.; Xie, M. H.; Wu, H. S.; Wang, N.; Tong, S. Y. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tang, Hong Kong (China)

    2006-10-09T23:59:59.000Z

    GaN exists in both wurtzite and zinc-blende phases and the growths of the two on its (0001) or (111) surfaces are achieved by choosing proper deposition conditions of molecular-beam epitaxy (MBE). At low substrate temperatures but high gallium fluxes, metastable zinc-blende GaN films are obtained, whereas at high temperatures and/or using high nitrogen fluxes, equilibrium wurtzite phase GaN epilayers resulted. This dependence of crystal structure on substrate temperature and source flux is not affected by deposition rate. Rather, the initial stage nucleation kinetics plays a primary role in determining the crystallographic structures of epitaxial GaN by MBE.

  18. Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, Yen-Ting [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Araki, Tsutomu [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan)] [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan); Palisaitis, Justinas; Persson, Per O. Å.; Olof Holtz, Per; Birch, Jens [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Chen, Li-Chyong [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China)] [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Chen, Kuei-Hsien [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Nanishi, Yasushi [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)] [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)

    2013-11-11T23:59:59.000Z

    Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (<35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a “narrow-pass” approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.

  19. Low virial parameters in molecular clouds: Implications for high-mass star formation and magnetic fields

    SciTech Connect (OSTI)

    Kauffmann, Jens; Pillai, Thushara [Astronomy Department, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Goldsmith, Paul F., E-mail: jens.kauffmann@astro.caltech.edu, E-mail: tpillai@astro.caltech.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Boulevard, Pasadena, CA 91109 (United States)

    2013-12-20T23:59:59.000Z

    Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only 'supercritical' cloud fragments are able to collapse and form stars. The virial parameter ? = M {sub vir}/M, which compares the virial mass to the actual mass, provides one way to gauge stability against collapse. Supercritical cloud fragments are characterized by ? ? 2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters ? ? 2 prevail in clouds. This would suggest that collapse toward star formation is a gradual and relatively slow process and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters <<2 and compile a catalog of 1325 virial parameter estimates. Low values of ? are in particular observed for regions of high-mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable 'competitive accretion' in HMSF, constrain some models of 'monolithic collapse', and might explain the absence of high-mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ?1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases.

  20. Fundamental studies of the plasma extraction and ion beam formation processes in inductively coupled plasma mass spectrometry

    SciTech Connect (OSTI)

    Niu, Hongsen

    1995-02-10T23:59:59.000Z

    The fundamental and practical aspects are described for extracting ions from atmospheric pressure plasma sources into an analytical mass spectrometer. Methodologies and basic concepts of inductively coupled plasma mass spectrometry (ICP-MS) are emphasized in the discussion, including ion source, sampling interface, supersonic expansion, slumming process, ion optics and beam focusing, and vacuum considerations. Some new developments and innovative designs are introduced. The plasma extraction process in ICP-MS was investigated by Langmuir measurements in the region between the skimmer and first ion lens. Electron temperature (T{sub e}) is in the range 2000--11000 K and changes with probe position inside an aerosol gas flow. Electron density (n{sub e}) is in the range 10{sup 8}--10{sup 10} {sup {minus}cm }at the skimmer tip and drops abruptly to 10{sup 6}--10{sup 8} cm{sup {minus}3} near the skimmer tip and drops abruptly to 10{sup 6}--10{sup 8} cm{sup {minus}3} downstream further behind the skimmer. Electron density in the beam leaving the skimmer also depends on water loading and on the presence and mass of matrix elements. Axially resolved distributions of electron number-density and electron temperature were obtained to characterize the ion beam at a variety of plasma operating conditions. The electron density dropped by a factor of 101 along the centerline between the sampler and skimmer cones in the first stage and continued to drop by factors of 10{sup 4}--10{sup 5} downstream of skimmer to the entrance of ion lens. The electron density in the beam expansion behind sampler cone exhibited a 1/z{sup 2} intensity fall-off (z is the axial position). An second beam expansion originated from the skimmer entrance, and the beam flow underwent with another 1/z{sup 2} fall-off behind the skimmer. Skimmer interactions play an important role in plasma extraction in the ICP-MS instrument.

  1. Molecular Inventories and Chemical Evolution of Low-mass Protostellar Envelopes

    E-Print Network [OSTI]

    J. K. Jorgensen; F. L. Schoeier; E. F. van Dishoeck

    2003-12-09T23:59:59.000Z

    This paper presents the first substantial study of the chemistry of the envelopes around a sample of 18 low-mass pre- and protostellar objects for which physical properties have previously been derived from radiative transfer modeling of their dust continuum emission. Single-dish line observations of 24 transitions of 9 molecular species (not counting isotopes) including HCO+, N2H+, CS, SO, SO2, HCN, HNC, HC3N and CN are reported. The line intensities are used to constrain the molecular abundances by comparison to Monte Carlo radiative transfer modeling of the line strengths. An empirical chemical network is constructed on the basis of correlations between the abundances of various species. For example, it is seen that the HCO+ and CO abundances are linearly correlated, both increasing with decreasing envelope mass. Species such as CS, SO and HCN show no trend with envelope mass. In particular no trend is seen between ``evolutionary stage'' of the objects and the abundances of the main sulfur- or nitrogen-containing species. Among the nitrogen-bearing species abundances of CN, HNC and HC3N are found to be closely correlated, which can be understood from considerations of the chemical network. The CS/SO abundance ratio is found to correlate with the abundances of CN and HC3N, which may reflect a dependence on the atomic carbon abundance. An anti-correlation is found between the deuteration of HCO+ and HCN, reflecting different temperature dependences for gas-phase deuteration mechanisms. The abundances are compared to other protostellar environments. In particular it is found that the abundances in the cold outer envelope of the previously studied class 0 protostar IRAS16293-2422 are in good agreement with the average abundances for the presented sample of class 0 objects.

  2. Gas source molecular beam epitaxy of scandium nitride on silicon carbide and gallium nitride surfaces

    SciTech Connect (OSTI)

    King, Sean W., E-mail: sean.king@intel.com; Davis, Robert F. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nemanich, Robert J. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-11-01T23:59:59.000Z

    Scandium nitride (ScN) is a group IIIB transition metal nitride semiconductor with numerous potential applications in electronic and optoelectronic devices due to close lattice matching with gallium nitride (GaN). However, prior investigations of ScN have focused primarily on heteroepitaxial growth on substrates with a high lattice mismatch of 7%–20%. In this study, the authors have investigated ammonia (NH{sub 3}) gas source molecular beam epitaxy (NH{sub 3}-GSMBE) of ScN on more closely lattice matched silicon carbide (SiC) and GaN surfaces (<3% mismatch). Based on a thermodynamic analysis of the ScN phase stability window, NH{sub 3}-GSMBE conditions of 10{sup ?5}–10{sup ?4} Torr NH{sub 3} and 800–1050?°C where selected for initial investigation. In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Rutherford backscattering measurements showed all ScN films grown using these conditions were stoichiometric. For ScN growth on 3C-SiC (111)-(?3?×??3)R30° carbon rich surfaces, the observed attenuation of the XPS Si 2p and C 1s substrate core levels with increasing ScN thickness indicated growth initiated in a layer-by-layer fashion. This was consistent with scanning electron microscopy (SEM) images of 100–200?nm thick films that revealed featureless surfaces. In contrast, ScN films grown on 3C-SiC (111)-(3?×?3) and 3C-SiC (100)-(3?×?2) silicon rich surfaces were found to exhibit extremely rough surfaces in SEM. ScN films grown on both 3C-SiC (111)-(?3?×??3)R30° and 2H-GaN (0001)-(1?×?1) epilayer surfaces exhibited hexagonal (1?×?1) low energy electron diffraction patterns indicative of (111) oriented ScN. X-ray diffraction ?-2? rocking curve scans for these same films showed a large full width half maximum of 0.29° (1047?arc sec) consistent with transmission electron microscopy images that revealed the films to be poly-crystalline with columnar grains oriented at ?15° to the [0001] direction of the 6H-SiC (0001) substrate. In-situ reflection electron energy loss spectroscopy measurements determined the band-gap for the NH{sub 3}-GSMBE ScN films to be 1.5?±?0.3 eV, and thermal probe measurements indicated all ScN films to be n-type. The four point probe sheet resistance of the ScN films was observed to increase with decreasing growth temperature and decreased with unintentional oxygen incorporation. Hg probe capacitance–voltage measurements indicated N{sub D}-N{sub A} decreased with decreasing growth temperature from 10{sup 19} to 10{sup 20}/cm{sup 3} for the lowest resistivity films to ?5?×?10{sup 16}/cm{sup 3} for the highest resistivity films. In-situ ultraviolet photoelectron spectroscopy measurements additionally showed the valence band maximum moving from 1.4 to 0.8 eV below the Fermi level with decreasing growth temperature consistent with the increased resistivity and reduction in carrier concentration. These results suggest that additional reductions in ScN carrier concentrations can be achieved via continued optimization of ScN growth conditions and selection of substrate orientation and surface termination.

  3. The effect of cluster formation on mass separation in binary molecular beams

    E-Print Network [OSTI]

    Sibener, Steven

    , a liquid nitrogen cooled titanium sublimation pump, and a 60 l s 1 turbomolecular pump, and has a base

  4. A precise Higgs mass measurement at the ILC and test beam data analyses

    E-Print Network [OSTI]

    Boyer, Edmond

    for the Higgs boson mass measurement, while the cross section could be measured to 5%; if we make some assumptions about the Higgs boson's decay, for example a Standard Model Higgs boson with a dominant invisible

  5. Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions

    SciTech Connect (OSTI)

    Zhang Meng; Bhattacharya, Pallab; Guo Wei; Banerjee, Animesh [Department of Electrical Engineering and Computer Science, Solid-State Electronics Laboratory, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

    2010-03-29T23:59:59.000Z

    Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 deg. C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1x10{sup 18} cm{sup -3}. The corresponding doping efficiency and hole mobility are approx4.9% and 3.7 cm{sup 2}/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (lambda{sub peak}=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 OMEGA.

  6. Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Wu, Z. H. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Kawai, Y.; Honda, Y.; Yamaguchi, M.; Amano, H. [Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Fang, Y.-Y.; Chen, C. Q. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Kondo, H.; Hori, M. [Graduate School of Engineering, Plasma Nanotechnology Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan)

    2011-04-04T23:59:59.000Z

    In this letter, we have investigated the structural properties of thick InGaN layers grown on GaN by plasma-assisted molecular beam epitaxy, using two growth rates of 1.0 and 3.6 A/s. A highly regular superlattice (SL) structure is found to be spontaneously formed in the film grown at 3.6 A/s but not in the film grown at 1.0 A/s. The faster grown film also exhibits superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank-Read dislocation generation mechanism within the spontaneously formed SL structure.

  7. Ultra-low resistance ohmic contacts to GaN with high Si doping concentrations grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Afroz Faria, Faiza; Guo Jia; Zhao Pei; Li Guowang; Kumar Kandaswamy, Prem; Wistey, Mark; Xing Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2012-07-16T23:59:59.000Z

    Ti/Al/Ni/Au ohmic contacts were formed on heavily doped n{sup +} metal-polar GaN samples with various Si doping concentrations grown by molecular beam epitaxy. The contact resistivity (R{sub C}) and sheet resistance (R{sub sh}) as a function of corresponding GaN free carrier concentration (n) were measured. Very low R{sub C} values (<0.09 {Omega} mm) were obtained, with a minimum R{sub C} of 0.035 {Omega} mm on a sample with a room temperature carrier concentration of {approx}5 Multiplication-Sign 10{sup 19} cm{sup -3}. Based on the systematic study, the role of R{sub C} and R{sub sh} is discussed in the context of regrown n{sup +} GaN ohmic contacts for GaN based high electron mobility transistors.

  8. Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Johnston, S. W. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Umbel, R. [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendelloesung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 {mu}m GaAs/(100)GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 {mu}s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge.

  9. Super-dense array of Ge quantum dots grown on Si(100) by low-temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Talochkin, A. B., E-mail: tal@isp.nsc.ru; Shklyaev, A. A. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Mashanov, V. I. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation)

    2014-04-14T23:59:59.000Z

    Ge layer grown on Si(100) at the low temperature of ?100?°C by molecular beam epitaxy is studied using scanning tunneling microscopy and Raman spectroscopy. It is found that crystalline and pseudomorphic to the Si substrate Ge islands are formed at the initial growth stage. The islands acquire the base size of 1.2–2.6?nm and they form arrays with the super-high density of (5–8)?×?10{sup 12}?cm{sup ?2} at 1–2?nm Ge coverages. Such a density is at least 10 times higher than that of Ge “hut” clusters grown via the Stranski-Krastanov growth mode. It is shown that areas between the crystalline Ge islands are filled with amorphous Ge, which is suggested to create potential barrier for holes localized within the islands. As a result, crystalline Ge quantum dots appear being isolated from each other.

  10. Intrinsic ultrathin topological insulators grown via molecular beam epitaxy characterized by in-situ angle resolved photoemission spectroscopy

    SciTech Connect (OSTI)

    Lee, J. J.; Vishik, I. M.; Ma, Y.; Shen, Z. X. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Schmitt, F. T.; Moore, R. G. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)

    2012-07-02T23:59:59.000Z

    We demonstrate the capability of growing high quality ultrathin (10 or fewer quintuple layers) films of the topological insulators Bi{sub 2}Se{sub 3} and Bi{sub 2}Te{sub 3} using molecular beam epitaxy. Unlike previous growth techniques, which often pin the Fermi energy in the conduction band for ultrathin samples, our samples remain intrinsic bulk insulators. We characterize these films using in-situ angle resolved photoemission spectroscopy, which is a direct probe of bandstructure, and ex-situ atomic force microscopy. We find that the conduction band lies above the Fermi energy, indicating bulk insulating behavior with only the surface states crossing the Fermi energy. The use of a thermal cracker allows for more stoichiometric flux rates during growth, while still creating intrinsically doped films, paving the way for future improvements in growth of topological insulators.

  11. Spinel-structured metal oxide on a substrate and method of making same by molecular beam epitaxy

    DOE Patents [OSTI]

    Chambers, Scott A.

    2006-02-21T23:59:59.000Z

    A method of making a spinel-structured metal oxide on a substrate by molecular beam epitaxy, comprising the step of supplying activated oxygen, a first metal atom flux, and at least one other metal atom flux to the surface of the substrate, wherein the metal atom fluxes are individually controlled at the substrate so as to grow the spinel-structured metal oxide on the substrate and the metal oxide is substantially in a thermodynamically stable state during the growth of the metal oxide. A particular embodiment of the present invention encompasses a method of making a spinel-structured binary ferrite, including Co ferrite, without the need of a post-growth anneal to obtain the desired equilibrium state.

  12. Influence of substrate quality on structural properties of AlGaN/GaN superlattices grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Schubert, F. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); Merkel, U.; Schmult, S. [TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany); Mikolajick, T. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany)

    2014-02-28T23:59:59.000Z

    Short-period AlGaN/GaN superlattices were established as versatile test structures to investigate the structural properties of molecular beam epitaxy (MBE)-grown GaN and AlGaN layers and their dependence on the GaN substrate quality. X-ray diffractometry data of the investigated superlattices allow access to relevant structural parameters such as aluminum mole fraction and layer thicknesses. The occurrence of theoretically predicted intense high-order satellite peaks and pronounced interface fringes in the diffraction pattern reflects abrupt interfaces and perfect 2-dimensional growth resulting in smooth surfaces. The data unambiguously demonstrate that the structural quality of the MBE grown layers is limited by the structural properties of the GaN substrate.

  13. High quality InAlN single layers lattice-matched to GaN grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM, Universidad Politecnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Rebled, J. M.; Peiro, F. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, CCiT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2011-07-18T23:59:59.000Z

    We report on properties of high quality {approx}60 nm thick InAlN layers nearly in-plane lattice-matched to GaN, grown on c-plane GaN-on-sapphire templates by plasma-assisted molecular beam epitaxy. Excellent crystalline quality and low surface roughness are confirmed by X-ray diffraction, transmission electron microscopy, and atomic force microscopy. High annular dark field observations reveal a periodic in-plane indium content variation (8 nm period), whereas optical measurements evidence certain residual absorption below the band-gap. The indium fluctuation is estimated to be {+-} 1.2% around the nominal 17% indium content via plasmon energy oscillations assessed by electron energy loss spectroscopy with sub-nanometric spatial resolution.

  14. Rapid silicon outdiffusion from SiC substrates during molecular-beam epitaxial growth of AlGaN/GaN/AlN transistor structures

    SciTech Connect (OSTI)

    Hoke, W.E.; Torabi, A.; Mosca, J.J.; Hallock, R.B.; Kennedy, T.D. [Raytheon RF Components, 362 Lowell Street, Andover, Massachusetts 01810 (United States)

    2005-10-15T23:59:59.000Z

    AlGaN/GaN/AlN transistor structures were grown onto SiC substrates by molecular-beam epitaxy. Under aluminum-rich growth conditions for the AlN nucleation layer, undesirable n-type conduction is observed near the GaN/AlN interface for even thick (>1000 A) AlN layers. Silicon is identified as the unwanted dopant from secondary-ion mass spectroscopy measurements. Atomic force microscopy surface maps reveal free aluminum metal on AlN surfaces grown under modest aluminum-rich conditions. It is proposed that rapid silicon migration is caused by molten aluminum reacting with the SiC substrate resulting in dissolved silicon that rapidly migrates through the growing AlN layer. This behavior is significantly reduced using a growth flux ratio of aluminum to reactive nitrogen close to unity. The resulting buffer leakage current of the GaN high electron mobility transistor structure is reduced by more than four orders of magnitude.

  15. Molecular characterization of organic aerosol using nanospray desorption/ electrospray ionization mass spectrometry: CalNex 2010 field study

    E-Print Network [OSTI]

    Goldstein, Allen

    Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA c Chemical and Materials Sciences molecular species were detected in the mass range of 50e400 m/z using positive mode ESI of aerosol samples in the 0.18e0.32 mm size range. Our analysis focused on identification of two main groups: compounds

  16. Crossed Molecular Beam Studies of Phenyl Radical Reactions with Propene and 2-Butene Daniel R. Albert, Michael A. Todt and H. Floyd Davis*

    E-Print Network [OSTI]

    Davis, H. Floyd

    Cornell University Ithaca, New York 14853 Abstract The reaction of phenyl radicals with propene has been studied at collision energies of 84 and 108 kJ/mol using the crossed molecular beams technique decreases as the collision energy increases. However, we find at both collision energies that the formation

  17. Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam ABSTRACT We present the structural and surface characterization of the alloy formation of scandium gallium GaN (w-GaN) spurred much interest in related III-nitrides such as aluminium nitride (Al

  18. Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures directly on sapphire substrates

    E-Print Network [OSTI]

    Manfra, Michael J.

    Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures-dimensional arrays Appl. Phys. Lett. 100, 203117 (2012) Partially filled intermediate band of Cr-doped GaN films Appl at telecommunication wavelengths J. Appl. Phys. 111, 093721 (2012) GaN epitaxy on Cu(110) by metal organic chemical

  19. Effect of dislocation scattering on the transport properties of InN grown on GaN substrates by molecular beam epitaxy

    E-Print Network [OSTI]

    Effect of dislocation scattering on the transport properties of InN grown on GaN substrates on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation, optical, and transport properties of InN on GaN substrates. In this work, we have studied the MBE growth

  20. Hexagonal Growth Spirals on GaN Grown by Molecular Beam Epitaxy: Kinetics vs Thermodynamics

    E-Print Network [OSTI]

    Cohen, Philip I.

    prepared, Ga-polar GaN(0001) templates. The surface morphology was studied using reflection high-energy-edge energy of 0.26 eV/Ã?. They suggest that local conditions at step edges dominate the growth. 1 conducted ex situ using AFM. Desorption mass spectrometry (DMS) was used to measure the GaN growth rate. Our

  1. Studies of silicon cluster--metal atom compound formation in a supersonic molecular beam

    SciTech Connect (OSTI)

    Beck, S.M.

    1987-10-01T23:59:59.000Z

    The first observation of a reaction between a metal atom and silicon in a supersonic jet to form metal atom silicon clusters is reported. Using the technique of laser vaporization supersonic expansion with metal carbonyl seeded carrier gas, clusters of the form MSi/sub n/ have been detected by ArF and KrF laser photoionization time-of-flight mass spectrometry. Three transition metals have been investigated, Cr, Mo, and W. The dominant product cluster peaks observed in the mass spectra obtained for all three metals corresponds to identical but remarkable cluster stoichiometries. The dominant peaks have formulas given by MSi/sub n/ where n = 15 and n = 16. The metal--semiconductor clusters are relatively more stable towards photofragmentation than the bare silicon cluster of the same size. The observation of these new species may be relevant to reactions which occur at the interface between a silicon wafer and deposited metals.

  2. Structural characterization of ZnO films grown by molecular beam epitaxy on sapphire with MgO buffer

    SciTech Connect (OSTI)

    Pecz, B.; El-Shaer, A.; Bakin, A.; Mofor, A.-C.; Waag, A.; Stoemenos, J. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig (Germany); Physics Department, Aristotle University, University Campus, 54006 Thessaloniki (Greece)

    2006-11-15T23:59:59.000Z

    The structural characteristics of the ZnO film grown on sapphire substrate using a thin MgO buffer layer were studied using transmission electron microscopy and high-resolution x-ray diffraction. The growth was carried out in a modified plasma-molecular beam epitaxy system. The observed misfit dislocations were well confined at the sapphire overgrown interface exhibiting domain matching epitaxy, where the integral multiples of lattice constants match across the interface. The main extended defects in the ZnO film were the threading dislocations having a mean density of 4x10{sup 9} cm{sup -2}. The formation of the MgO buffer layer as well as the ZnO growth were monitored in situ by reflection high-energy electron diffraction. The very thin {approx}1 nm, MgO buffer layer can partially interdiffuse with the ZnO as well as react with the Al{sub 2}O{sub 3} substrate forming an intermediate epitaxial layer having the spinel (MgO/Al{sub 2}O{sub 3}) structure.

  3. Critical thickness and strain relaxation in molecular beam epitaxy-grown SrTiO{sub 3} films

    SciTech Connect (OSTI)

    Wang, Tianqi; Ganguly, Koustav; Marshall, Patrick; Xu, Peng; Jalan, Bharat [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)] [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2013-11-18T23:59:59.000Z

    We report on the study of the critical thickness and the strain relaxation in epitaxial SrTiO{sub 3} film grown on (La{sub 0.3}Sr{sub 0.7})(Al{sub 0.65}Ta{sub 0.35})O{sub 3} (001) (LSAT) substrate using the hybrid molecular beam epitaxy approach. No change in the film's lattice parameter (both the in-plane and the out-of-plane) was observed up to a film thickness of 180 nm, which is in sharp contrast to the theoretical critical thickness of ?12 nm calculated using the equilibrium theory of strain relaxation. For film thicknesses greater than 180 nm, the out-of-plane lattice parameter was found to decrease hyperbolically in an excellent agreement with the relaxation via forming misfit dislocations. Possible mechanisms are discussed by which the elastic strain energy can be accommodated prior to forming misfit dislocations leading to such anomalously large critical thickness.

  4. Control of tensile strain and interdiffusion in Ge/Si(001) epilayers grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Luong, T. K. P.; Dau, M. T.; Zrir, M. A.; Le Thanh, V.; Petit, M. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France)] [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Stoffel, M.; Rinnert, H. [Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France)] [Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Ghrib, A.; El Kurdi, M.; Boucaud, P. [Institut d'Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Ba-carett. 220, 91405 Orsay (France)] [Institut d'Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Ba-carett. 220, 91405 Orsay (France); Murota, J. [Research Institute of Electrical Communications, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)] [Research Institute of Electrical Communications, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2013-08-28T23:59:59.000Z

    Tensile-strained and n-doped Ge has emerged as a potential candidate for the realization of optoelectronic devices that are compatible with the mainstream silicon technology. Tensile-strained Ge/Si epilayers can be obtained by using the difference of thermal expansion coefficients between Ge and Si. We have combined various surface, structural, and compositional characterizations to investigate the growth mode and the strain state in Ge/Si epilayers grown by molecular-beam epitaxy. The Ge growth was carried out using a two-step approach: a low-temperature growth to produce relaxed and smooth buffer layers, which is followed by a high-temperature growth to get high quality Ge layers. The existence of a substrate temperature window from 260 to 300 °C is evidenced, which allows to completely suppress the Ge/Si Stranski-Krastanov growth. As a consequence of the high temperature growth, a tensile strain lying in the range of 0.22%–0.24% is obtained. Concerning the effect of thermal annealing, it is shown that cyclic annealing may allow increasing the tensile strain up to 0.30%. Finally, we propose an approach to use carbon adsorption to suppress Si/Ge interdiffusion, which represents one of the main obstacles to overcome in order to realize pure Ge-based optoelectronic devices.

  5. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Limbach, F. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Gotschke, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Stoica, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Calarco, R. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Sutter, E. [Brookhaven National Lab., Upton, NY (United States); Ciston, J. [Brookhaven National Lab., Upton, NY (United States); Cusco, R. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Artus, L. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Kremling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Hofling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Worschech, L. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Grutzmacher, D. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany)

    2011-01-07T23:59:59.000Z

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.

  6. Characteristics of AlN/GaN nanowire Bragg mirror grown on (001) silicon by molecular beam epitaxy

    SciTech Connect (OSTI)

    Heo, Junseok; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)] [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States); Zhou, Zifan [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States)] [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Guo, Wei [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)] [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ooi, Boon S. [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)] [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2013-10-28T23:59:59.000Z

    GaN nanowires containing AlN/GaN distributed Bragg reflector (DBR) heterostructures have been grown on (001) silicon substrate by molecular beam epitaxy. A peak reflectance of 70% with normal incidence at 560 nm is derived from angle resolved reflectance measurements on the as-grown nanowire DBR array. The measured peak reflectance wavelength is significantly blue-shifted from the ideal calculated value. The discrepancy is explained by investigating the reflectance of the nanoscale DBRs with a finite difference time domain technique. Ensemble nanowire microcavities with In{sub 0.3}Ga{sub 0.7}N nanowires clad by AlN/GaN DBRs have also been characterized. Room temperature emission from the microcavity exhibits considerable linewidth narrowing compared to that measured for unclad In{sub 0.3}Ga{sub 0.7}N nanowires. The resonant emission is characterized by a peak wavelength and linewidth of 575 nm and 39 nm, respectively.

  7. Direct imaging of InSb (110)-(1x1) surface grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Mishima, T. D. [Homer L. Dodge Department of Physics and Astronomy, and Center for Semiconductor Physics in Nanostructures, University of Oklahoma, Norman, Oklahoma 73019 (United States)

    2011-10-01T23:59:59.000Z

    High-resolution transmission electron microscopy under a profile imaging condition (HR-profile TEM) was employed to determine the structural model for the InSb(110)-(1x1) relaxation surface grown by molecular beam epitaxy (MBE). HR-profile TEM analyses indicate that the chevron model, which is widely accepted for zinc-blende-type III-V(110)-(1x1) surfaces prepared by cleavage, is also applicable to the InSb(110)-(1x1) surface prepared under an Sb-rich MBE condition. The assignment of atomic species (In or Sb) of InSb(110)-(1x1) surfaces was confirmed based on a HR-profile TEM image that captures the connected facets of InSb(110)-(1x1) and InSb(111)B-(2x2). On the basis of the well-known atomic species of InSb(111)B-(2x2), the atomic species of the InSb(110)-(1x1) surface were deduced straightforwardly: the atoms shifted upward and downward at the topmost layer of the InSb(110)-(1x1) surface are Sb and In, respectively. The atomic arrangements of the InSb(110)-(1x1)-InSb(111)B-(2x2) facet determined by HR-profile TEM may represent the atomic arrangements of zinc-blende-type III-V(331)B surfaces.

  8. Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2006-07-01T23:59:59.000Z

    Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2x10{sup 6} cm{sup -2}. A threshold current density of J{sub th}{approx}1.65 kA/cm{sup 2} for the as-cleaved, gain-guided AlGaInP laser grown on SiGe/Si was obtained at the peak emission wavelength of 680 nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods.

  9. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kushvaha, S. S., E-mail: kushvahas@nplindia.org; Pal, P.; Shukla, A. K.; Joshi, Amish G.; Gupta, Govind; Kumar, M.; Singh, S.; Gupta, Bipin K.; Haranath, D. [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)

    2014-02-15T23:59:59.000Z

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 ?m thick GaN epi-layer on sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 10{sup 8} cm{sup ?2} at 750 °C) than that of the low temperature grown sample (1.1 × 10{sup 9} cm{sup ?2} at 730 °C). A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  10. TWO MASS DISTRIBUTIONS IN THE L 1641 MOLECULAR CLOUDS: THE HERSCHEL CONNECTION OF DENSE CORES AND FILAMENTS IN ORION A

    SciTech Connect (OSTI)

    Polychroni, D. [Department of Astrophysics, University of Athens, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis, 15784 Zografos, Athens (Greece)] [Department of Astrophysics, University of Athens, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis, 15784 Zografos, Athens (Greece); Schisano, E.; Elia, D.; Molinari, S.; Turrini, D.; Rygl, K. L. J.; Benedettini, M.; Busquet, G.; Di Giorgio, A. M.; Pestalozzi, M.; Pezzuto, S. [Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), via del Fosso del Cavaliere 100, I-00133 Roma (Italy)] [Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Roy, A.; André, Ph.; Hennemann, M.; Hill, T.; Könyves, V. [Laboratoire AIM, CEA/IRFU CNRS/INSU Université Paris Diderot, Paris-Saclay, F-91191 Gif-sur-Yvette (France)] [Laboratoire AIM, CEA/IRFU CNRS/INSU Université Paris Diderot, Paris-Saclay, F-91191 Gif-sur-Yvette (France); Martin, P. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)] [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Di Francesco, J. [National Research Council Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)] [National Research Council Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Arzoumanian, D. [IAS, CNRS (UMR 8617), Université Paris-Sud, Bâtiment 121, F-91400 Orsay (France)] [IAS, CNRS (UMR 8617), Université Paris-Sud, Bâtiment 121, F-91400 Orsay (France); Bontemps, S., E-mail: dpolychroni@phys.uoa.gr [Université de Bordeaux, Laboratoire d' Astrophysique de Bordeaux, CNRS/INSU, UMR 5804, BP 89, F-33271, Floirac Cedex (France); and others

    2013-11-10T23:59:59.000Z

    We present Herschel survey maps of the L 1641 molecular clouds in Orion A. We extracted both the filaments and dense cores in the region. We identified which of the dense sources are proto- or pre-stellar, and studied their association with the identified filaments. We find that although most (71%) of the pre-stellar sources are located on filaments there, is still a significant fraction of sources not associated with such structures. We find that these two populations (on and off the identified filaments) have distinctly different mass distributions. The mass distribution of the sources on the filaments is found to peak at 4 M {sub ?} and drives the shape of the core mass function (CMF) at higher masses, which we fit with a power law of the form dN/dlogM?M {sup –1.4±0.4}. The mass distribution of the sources off the filaments, on the other hand, peaks at 0.8 M {sub ?} and leads to a flattening of the CMF at masses lower than ?4 M {sub ?}. We postulate that this difference between the mass distributions is due to the higher proportion of gas that is available in the filaments, rather than in the diffuse cloud.

  11. Role of Ion Damage on Unintentional Ca Incorporation During the Plasma-Assisted Molecular-Beam Epitaxy Growth of Dilute Nitrides Using N2/Ar Source Gas Mixtures

    SciTech Connect (OSTI)

    Oye, M. M.; Bank, S. R.; Ptak, A. J.; Reedy, R. C.; Goorsky, M. S.; Holmes Jr., A. L.

    2008-05-01T23:59:59.000Z

    Unintentional Ca incorporation caused by Ca-contaminated substrate surfaces on as-purchased GaAs wafers are known to limit the efficiency of solar cells based on dilute nitride materials. This article focuses on further understanding the conditions and mechanisms by which these Ca impurities incorporate. Plasma-assisted molecular-beam epitaxy utilizing a 1% N{sub 2} in Ar precursor gas mixture was used to grow GaAs at 400 and 580 C, and GaN{sub 0.01}As{sub 0.99} at 400 C. Two plasma operating combinations of rf power and gas flow rate were used to generate different amounts and energies of both ions and other plasma species, while keeping nitrogen incorporation constant. The ions were characterized with a dual-grid, retarding-field ion energy analyzer, and the corresponding ion energy distributions are presented to correlate ions with Ca incorporation. When appropriate, dc-biased deflector plates were used to remove ions during growth. Secondary ion mass spectrometry was used to measure Ca in GaAs and GaN{sub 0.01}As{sub 0.99}. Ca incorporation was observed in the dilute nitride samples, but the effects of ions did not exceed other Ca incorporation mechanisms associated with defects due to both low temperature growth and nitrogen incorporation; however, different neutral active nitrogen species (atomic N and metastable N{sub 2}) may be a factor. Ca incorporation measured in GaAs grown at 400 C with a pure Ar plasma is predominantly due to defects associated with low temperature growth, as opposed to plasma damage caused by the ions. GaAs growths at 580 C without a plasma did not exhibit Ca incorporation, but growth at 580 C with ions from a pure Ar plasma caused Ca incorporation.

  12. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect (OSTI)

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D. [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)

    2013-09-15T23:59:59.000Z

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  13. Nucleation and Stoichiometry Dependence of rutile-TiO2(001)/GaN(0001) Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Feenstra, Randall

    the initial nucleation and the stoichiometry of rutile- TiO2(001) grown on wurtzite GaN(0001) by radio explore the growth of rutile-TiO2(001) on wurtzite GaN(0001) by oxygen plasma-assisted molecular beam) was maintained constant at 400 W. The substrates were commercially available wurtzite Ga-polar GaN(0001) grown

  14. Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular-type GaN(000¯1) by MBE using a custom built Hf electron beam source and an ammonia leak. The films were). It was found that epitaxial growth of Hf is possible even at room temperature. GaN films varying in thickness

  15. Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics 

    E-Print Network [OSTI]

    Sawyer, Holly Ann

    2006-04-12T23:59:59.000Z

    Ion mobility-mass spectrometry (IM-MS), gas-phase hydrogen/deuterium (H/D) exchange ion molecule reactions and molecular modeling provide complimentary information and are used here for the characterization of peptide ion structure, including fine...

  16. Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics

    E-Print Network [OSTI]

    Sawyer, Holly Ann

    2006-04-12T23:59:59.000Z

    Ion mobility-mass spectrometry (IM-MS), gas-phase hydrogen/deuterium (H/D) exchange ion molecule reactions and molecular modeling provide complimentary information and are used here for the characterization of peptide ion structure, including fine...

  17. Molecular Science Computing | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Scientific Capabilities Molecular Science Computing Overview Cell Isolation and Systems Analysis Deposition and Microfabrication Mass Spectrometry Microscopy Molecular Science...

  18. Crystal orientation mechanism of ZnTe epilayers formed on different orientations of sapphire substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Nakasu, T., E-mail: n-taizo.nakasu@asagi.waseda.jp; Yamashita, S.; Aiba, T.; Hattori, S.; Sun, W.; Taguri, K.; Kazami, F. [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, M. [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials and Technology, Waseda University, Tokyo 169-0051 (Japan)

    2014-10-28T23:59:59.000Z

    The electrooptic effect in ZnTe has recently attracted research attention, and various device structures using ZnTe have been explored. For application to practical terahertz wave detector devices based on ZnTe thin films, sapphire substrates are preferred because they enable the optical path alignment to be simplified. ZnTe/sapphire heterostructures were focused upon, and ZnTe epilayers were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. Epitaxial relationships between the ZnTe thin films and the sapphire substrates with their various orientations were investigated using an X-ray diffraction pole figure method. (0001) c-plane, (1-102) r-plane, (1-100) m-plane, and (11-20) a-plane oriented sapphire substrates were used in this study. The epitaxial relationship between ZnTe and c-plane sapphire was found to be (111) ZnTe//(0001) sapphire with an in-plane orientation relationship of [?211] ZnTe//[1-100] sapphire. It was found that the (211)-plane ZnTe layer was grown on the m-plane of the sapphire substrates, and the (100)-plane ZnTe layer was grown on the r-plane sapphire. When the sapphire substrates were inclined from the c-plane towards the m-axis direction, the orientation of the ZnTe thin films was then tilted from the (111)-plane to the (211)-plane. The c-plane of the sapphire substrates governs the formation of the (111) ZnTe domain and the ZnTe epilayer orientation. These crystallographic features were also related to the atom arrangements of ZnTe and sapphire.

  19. Localized Si enrichment in coherent self-assembled Ge islands grown by molecular beam epitaxy on (001)Si single crystal

    SciTech Connect (OSTI)

    Valvo, M. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95127 Catania (Italy); Bongiorno, C.; Giannazzo, F. [IMM-CNR, VIII strada 5, 95121 Catania (Italy); Terrasi, A. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95127 Catania (Italy); MATIS IMM-CNR UOS Catania (Universita), via S. Sofia 64, 95123 Catania (Italy)

    2013-01-21T23:59:59.000Z

    Transmission electron microscopy (TEM), atomic force microscopy, and Rutherford backscattering spectrometry (RBS) have been used to investigate the morphology, structure, and composition of self-assembled Ge islands grown on Si (001) substrates by molecular beam epitaxy (MBE) at different temperatures. Increasing the temperature from 550 Degree-Sign C to 700 Degree-Sign C causes progressive size and shape uniformity, accompanied by enhanced Si-Ge intermixing within the islands and their wetting layer. Elemental maps obtained by energy filtered-TEM (EF-TEM) clearly show pronounced Si concentration not only in correspondence of island base perimeters, but also along their curved surface boundaries. This phenomenon is strengthened by an increase of the growth temperature, being practically negligible at 550 Degree-Sign C, while very remarkable already at 650 Degree-Sign C. The resulting island shape is affected, since this localized Si enrichment not only provides strain relief near their highly stressed base perimeters but it also influences the cluster surface energy by effective alloying, so as to form Si-enriched SiGe interfaces. Further increase to 700 Degree-Sign C causes a shape transition where more homogenous Si-Ge concentration profiles are observed. The crucial role played by local 'flattened' alloyed clusters, similar to truncated pyramids with larger bases and enhanced Si enrichment at coherently stressed interfaces, has been further clarified by EF-TEM analysis of a multi-layered Ge/Si structure containing stacked Ge islands grown at 650 Degree-Sign C. Sharp accumulation of Si has been here observed not only in proximity of the uncapped island surface in the topmost layer but also at the buried Ge/Si interfaces and even in the core of such capped Ge islands.

  20. Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kamyczek, P.; Placzek-Popko, E.; Zielony, E.; Gumienny, Z. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Zytkiewicz, Z. R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-14T23:59:59.000Z

    In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77?K–350?K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (?-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E{sub 1}?=?0.65?eV, ?{sub 1}?=?8.2 × 10{sup ?16} cm{sup 2} and E{sub 2}?=?0.58?eV, ?{sub 2}?=?2.6 × 10{sup ?15} cm{sup 2} whereas for the two low-temperature majority traps they were equal to E{sub 3}?=?0.18?eV, ?{sub 3}?=?9.7 × 10{sup ?18} cm{sup 2} and E{sub 4}?=?0.13?eV, ?{sub 4}?=?9.2 × 10{sup ?18} cm{sup 2}. The possible origin of the traps is discussed and the results are compared with data reported elsewhere.

  1. Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

    SciTech Connect (OSTI)

    Novikov, S. V.; Staddon, C. R.; Foxon, C. T.; Yu, K. M.; Broesler, R.; Hawkridge, M.; Liliental-Weber, Z.; Walukiewicz, W.; Denlinger, J.; Demchenko, I.

    2009-10-06T23:59:59.000Z

    The authors have succeeded in growing GaN1?xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As{sub 2} flux at low (as low as 100 C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x > 0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from -3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of -0.8 eV at x - 0.8. The composition dependence of the band gap of the crystalline GaN{sub 1?x}As{sub x} alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN{sub 1?x}As{sub x} with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN{sub 1?x}As{sub x} alloys have short-range ordering that resembles random crystalline GaN{sub 1?x}As{sub x} alloys. They have demonstrated the possibility of the growth of amorphous GaN{sub 1?x}As{sub x} layers with variable As content on glass substrates

  2. Three-dimensional molecular imaging by infrared laser ablation electrospray ionization mass spectrometry

    SciTech Connect (OSTI)

    Vertes, Akos; Nemes, Peter

    2012-10-30T23:59:59.000Z

    The field of the invention is atmospheric pressure mass spectrometry (MS), and more specifically a process and apparatus which combine infrared laser ablation with electrospray ionization (ESI).

  3. Three-dimensional molecular imaging by infrared laser ablation electrospray ionization mass spectrometry

    DOE Patents [OSTI]

    Vertes, Akos (Reston, VA); Nemes, Peter (Silver Spring, MD)

    2011-06-21T23:59:59.000Z

    The field of the invention is atmospheric pressure mass spectrometry (MS), and more specifically a process and apparatus which combine infrared laser ablation with electrospray ionization (ESI).

  4. Three-dimensional molecular imaging by infrared laser ablation electrospray ionization mass spectrometry

    DOE Patents [OSTI]

    Vertes, Akos; Nemes, Peter

    2013-07-16T23:59:59.000Z

    The field of the invention is atmospheric pressure mass spectrometry (MS), and more specifically a process and apparatus which combine infrared laser ablation with electrospray ionization (ESI).

  5. Molecular Beam Kinetics | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    desorption... The Deposition Angle-Dependent Density of Amorphous Solid Water Films. The index of refraction and thickness of amorphous solid water (ASW) films are determined...

  6. Molecular Beam Epitaxy | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    hold the promise of turning sunlight into fuel. They are excellent candidates for solar hydrolysis -... Angling chromium to let oxygen through Posted: Wednesday, September...

  7. Time-Resolved Molecular Characterization of Limonene/Ozone Aerosol using High-Resolution Electrospray Ionization Mass Spectrometry

    SciTech Connect (OSTI)

    Bateman, Adam P.; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2009-09-09T23:59:59.000Z

    Molecular composition of limonene/O3 secondary organic aerosol (SOA) was investigated using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as a function of reaction time. SOA was generated by ozonation of D-limonene in a reaction chamber and sampled at different time intervals using a cascade impactor. The SOA samples were extracted into acetonitrile and analyzed using a HR-ESI-MS instrument with a resolving power of 100,000 (m/?m). The resulting mass spectra provided detailed information about the extent of oxidation inferred from the O:C ratios, double bond equivalency (DBE) factors, and aromaticity indexes (AI) in hundreds of identified individual SOA species.

  8. On the Validity of Collider-Mass Scaling for Molecular Rotational Excitation

    E-Print Network [OSTI]

    Walker, Kyle M; Stancil, P C; Balakrishnan, N; Forrey, R C

    2014-01-01T23:59:59.000Z

    Rate coefficients for collisional processes such as rotational and vibrational excitation are essential inputs in many astrophysical models. When rate coefficients are unknown, they are often estimated using known values from other systems. The most common example is to use He-collider rate coefficients to estimate values for other colliders, typically H$_2$, using scaling arguments based on the reduced mass of the collision system. This procedure is often justified by the assumption that the inelastic cross section is independent of the collider. Here we explore the validity of this approach focusing on rotational inelastic transitions for collisions of H, para-H$_2$, $^3$He, and $^4$He with CO in its vibrational ground state. We compare rate coefficients obtained via explicit calculations to those deduced by standard reduced-mass scaling. Not surprisingly, inelastic cross sections and rate coefficients are found to depend sensitively on both the reduced mass and the interaction potential energy surface. We ...

  9. Donor and acceptor levels in ZnO homoepitaxial thin films grown by molecular beam epitaxy and doped with plasma-activated nitrogen

    SciTech Connect (OSTI)

    Muret, Pierre [Departement Nanosciences, Institut Neel, CNRS, BP166, 38042 Grenoble and Universite Joseph Fourier, Grenoble (France); Tainoff, Dimitri; Morhain, Christian [Centre de Recherche sur l'HeteroEpitaxie et ses Applications, rue Bernard Gregory, CNRS, 06500 Valbonne (France); Chauveau, Jean-Michel [Centre de Recherche sur l'HeteroEpitaxie et ses Applications, rue Bernard Gregory, CNRS, 06500 Valbonne (France); Universite de Nice Sophia Antipolis, Parc Valrose F-06103 Nice (France)

    2012-09-17T23:59:59.000Z

    Deep level transient spectroscopy of both majority and minority carrier traps is performed in a n-type, nitrogen doped homoepitaxial ZnO layer grown on a m-plane by molecular beam epitaxy. Deep levels, most of them being not detected in undoped ZnO, lie close to the band edges with ionization energies in the range 0.12-0.60 eV. The two hole traps with largest capture cross sections are likely acceptors, 0.19 and 0.48 eV from the valence band edge, able to be ionized below room temperature. These results are compared with theoretical predictions and other experimental data.

  10. The study of in situ scanning tunnelling microscope characterization on GaN thin film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Yang, R.; Krzyzewski, T.; Jones, T. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)] [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2013-03-18T23:59:59.000Z

    The epitaxial growth of GaN by Plasma Assisted Molecular Beam Epitaxy was investigated by Scanning Tunnelling Microscope (STM). The GaN film was grown on initial GaN (0001) and monitored by in situ Reflection High Energy Electron Diffraction and STM during the growth. The STM characterization was carried out on different sub-films with increased thickness. The growth of GaN was achieved in 3D mode, and the hexagonal edge of GaN layers and growth gradient were observed. The final GaN was of Ga polarity and kept as (0001) orientation, without excess Ga adlayers or droplets formed on the surface.

  11. Dosimetric Evaluation Between Megavoltage Cone-Beam Computed Tomography and Body Mass Index for Intracranial, Thoracic, and Pelvic Localization

    SciTech Connect (OSTI)

    VanAntwerp, April E. [Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH (United States); Raymond, Sarah M., E-mail: raymons9@ccf.org [Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH (United States); Addington, Mark C.; Gajdos, Stephen; Vassil, Andrew; Xia, Ping [Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH (United States)

    2011-10-01T23:59:59.000Z

    The aim of this study was to evaluate radiation dose for organs at risk (OAR) within the cranium, thorax, and pelvis from megavoltage cone-beam computed tomography (MV-CBCT). Using a clinical treatment planning system, CBCT doses were calculated from 60 patient datasets using 27.4 x 27.4 cm{sup 2} field size and 200{sup o} arc length. The body mass indices (BMIs) for these patients range from 17.2-48.4 kg/m{sup 2}. A total of 60 CBCT plans were created and calculated with heterogeneity corrections, with monitor units (MU) that varied from 8, 4, and 2 MU per plan. The isocenters of these plans were placed at defined anatomical structures. The maximum dose, dose to the isocenter, and mean dose to the selected critical organs were analyzed. The study found that maximum and isocenter doses were weakly associated with BMI, but linearly associated with the total MU. Average maximum/isocenter doses in the cranium were 10.0 ({+-} 0.18)/7.0 ({+-} 0.08) cGy, 5.0 ({+-} 0.09)/3.5 ({+-} 0.05) cGy, and 2.5 ({+-} .04)/1.8 ({+-} 0.05) cGy for 8, 4, and 2 MU, respectively. Similar trends but slightly larger maximum/isocenter doses were found in the thoracic and pelvic regions. For the cranial region, the average mean doses with a total of 8 MU to the eye, lens, and brain were 9.7 ({+-} 0.12) cGy, 9.1 ({+-} 0.16) cGy, and 7.2 ({+-} 0.10) cGy, respectively. For the thoracic region, the average mean doses to the lung, heart, and spinal cord were 6.6 ({+-} 0.05) cGy, 6.9 ({+-} 1.2) cGy, and 4.7 ({+-} 0.8) cGy, respectively. For the pelvic region, the average mean dose to the femoral heads was 6.4 ({+-} 1.1) cGy. The MV-CBCT doses were linearly associated with the total MU but weakly dependent on patients' BMIs. Daily MV-CBCT has a cumulative effect on the total body dose and critical organs, which should be carefully considered for clinical impacts.

  12. Compositional Analysis of the High Molecular Weight Ethylene Oxide Propylene Oxide Copolymer by MALDI Mass Spectrometry

    E-Print Network [OSTI]

    Houshia, Orwa Jaber

    2012-01-01T23:59:59.000Z

    The composition of narrow distribution poly ethylene oxide-propylene oxide copolymer (Mw ~ 8700 Da) was studied using matrix assisted laser desorption ionization (MALDI) mass spectrometry. The ethylene oxide-propylene oxide copolymer produced oligomers separated by 14 Da. The average resolving power over the entire spectrum was 28,000. Approximately 448 isotopically resolved peaks representing about 56 oligomers are identified. Although agreement between experimental and calculated isotopic distributions was strong, the compositional assignment was difficult. This is due to the large number of possible isobaric components. The purpose of this research is to resolve and study the composition of high mass copolymer such as ethylene oxide-propylene oxide.

  13. A crossed molecular beams study of the reaction of the ethynyl radical )) with allene (H2CCCH2(X1

    E-Print Network [OSTI]

    Kaiser, Ralf I.

    molecular hydrogen (H2),8,9 molecular oxygen (O2),10 and water (H2O)11 via hydrocarbons 2,12­16 to nitrogen role in the synthesis of polyynes, polycyclic aromatic hydrocarbons (PAHs), and soot particles;1 (PAHs) and aerosol particles.22,23 Since the macroscopic alteration of combustion systems and planetary

  14. Zinc-blende (Cubic) GaN and AlGaN Layers, Structures and Bulk Crystals by Molecular Beam Epitaxy

    SciTech Connect (OSTI)

    Novikov, Sergei V.; Zainal, Norzaini; Akimov, Andrey V.; Staddon, Chris R.; Foxon, C. Thomas; Kent, Anthony J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-11-01T23:59:59.000Z

    We have studied the growth of zinc-blende GaN and AlGaN layers, structures and bulk crystals by molecular beam epitaxy (MBE). We have developed a process for growth by MBE of free-standing cubic GaN layers. Undoped thick cubic GaN films were grown on semi-insulating GaAs (001) substrates by a modified plasma-assisted molecular beam epitaxy (PA-MBE) method and were removed from the GaAs substrate after the growth. The resulting free-standing GaN wafers with thicknesses in the 30-100 {mu}m range may be used as substrates for further epitaxy of cubic GaN-based structures and devices. We have developed procedures to cleave the wafers into 10x10 mm{sup 2} square substrates and to polish them to produce epi-ready surfaces. The first GaN/InGaN LEDs on our zinc-blende GaN substrates have been demonstrated by our collaborators at Sharp Laboratories of Europe.

  15. Si (111) substrates as highly effective pseudomasks for selective growth of GaN material and devices by ammonia-molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tang, H.; Haffouz, S.; Bardwell, J.A. [Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

    2006-04-24T23:59:59.000Z

    The unique property of Si (111) as effective pseudomask substrate for selective growth of GaN by ammonia-molecular-beam epitaxy is reported. The critical nucleation temperature of GaN on Si (111) surface is found to be as low as 700 deg. C, much lower than that on sapphire or AlN surface. As a result, selective growth of GaN is possible by ammonia-molecular-beam epitaxy on Si (111) substrates using a patterned AlN buffer layer. The wide range of growth temperatures (700-900 deg. C) available for selective growth is a critical advantage for control and optimization of the facet characteristics of the selectively grown GaN patterns as required for potential fabrication of site-specific GaN or InGaN quantum dots. The demonstrated ease of selective growth of GaN on silicon has also implications in potential on-chip integration of GaN devices with silicon devices.

  16. Tracing Embedded Stellar Populations in Clusters and Galaxies using Molecular Emission: Methanol as a Signature of the Low-Mass End of the IMF

    E-Print Network [OSTI]

    Kristensen, L E

    2015-01-01T23:59:59.000Z

    Most low-mass protostars form in clusters, in particular high-mass clusters; however, how low-mass stars form in high-mass clusters and what the mass distribution is, are still open questions both in our own Galaxy and elsewhere. To access the population of forming embedded low-mass protostars observationally, we propose to use molecular outflows as tracers. Because the outflow emission scales with mass, the effective contrast between low-mass protostars and their high-mass cousins is greatly lowered. In particular, maps of methanol emission at 338.4 GHz (J=7_0 - 6_0 A+) in low-mass clusters illustrate that this transition is an excellent probe of the low-mass population. We here present a model of a forming cluster where methanol emission is assigned to every embedded low-mass protostar. The resulting model image of methanol emission is compared to recent ALMA observations toward a high-mass cluster and the similarity is striking: the toy model reproduces observations to better than a factor of two and sugge...

  17. Molecular Gas in Early-type Galaxies

    E-Print Network [OSTI]

    Alatalo, Katherine Anne

    2012-01-01T23:59:59.000Z

    toward the center (first seen in the molecular gas in A+3.4 Molecular Gas Mass . . . . . . .of the molecular gas . . . . . . . . . . 2.4.3 Mass of

  18. Molecular Characterization of Organic Aerosols Using Nanospray Desorption/Electrospray Ionization-Mass Spectrometry

    SciTech Connect (OSTI)

    Roach, Patrick J.; Laskin, Julia; Laskin, Alexander

    2010-10-01T23:59:59.000Z

    Nanospray desorption electrospray ionization (Nano-DESI) combined with high-resolution mass spectrometry (HR/MS) is a promising approach for detailed chemical characterization of atmospheric organic aerosol (OA) collected in laboratory and field experiments. In Nano-DESI analyte is desorbed into a solvent bridge formed between two capillaries and the analysis surface, which enables fast and efficient characterization of OA collected on substrates without special sample preparation. Stable signals achieved using Nano-DESI make it possible to obtain high-quality HR/MS data using only a small amount of material (<10 ng). Furthermore, Nano-DESI enables efficient detection of chemically labile compounds in OA, which is important for understanding chemical aging phenomena.

  19. Molecular opacities for low-mass metal-poor AGB stars undergoing the Third Dredge Up

    E-Print Network [OSTI]

    S. Cristallo; O. Straniero; M. T. Lederer; B. Aringer

    2007-06-14T23:59:59.000Z

    The concomitant overabundances of C, N and s-process elements are commonly ascribed to the complex interplay of nucleosynthesis, mixing and mass loss taking place in Asymptotic Giant Branch stars. At low metallicity, the enhancement of C and/or N may be up to 1000 times larger than the original iron content and significantly affects the stellar structure and its evolution. For this reason, the interpretation of the already available and still growing amount of data concerning C-rich metal-poor stars belonging to our Galaxy as well as to dwarf spheroidal galaxies would require reliable AGB stellar models for low and very low metallicities. In this paper we address the question of calculation and use of appropriate opacity coefficients, which take into account the C enhancement caused by the third dredge up. A possible N enhancement, caused by the cool bottom process or by the engulfment of protons into the convective zone generated by a thermal pulse and the subsequent huge third dredge up, is also considered. Basing on up-to-date stellar models, we illustrate the changes induced by the use of these opacity on the physical and chemical properties expected for these stars.

  20. Submilliampere threshold current pseudomorphic InGaAs/AlGaAs buried-heterostructure quantum well lasers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Eng, L.E.; Chen, T.R.; Sanders, S.; Zhuang, Y.H.; Zhao, B.; Yariv, A. (Department of Applied Physics, California Institute of Technology, Pasadena, California 91125 (US)); Morkoc, H. (The Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801)

    1989-10-02T23:59:59.000Z

    We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm{sup 2} at 990 nm were measured for 1540-{mu}m-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-{mu}m-wide stripe and 425-{mu}m-long cavity. With reflective coatings the best device showed 0.9 mA threshold current ({ital L}=225 {mu}m). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

  1. Domain formation due to surface steps in topological insulator Bi{sub 2}Te{sub 3} thin films grown on Si (111) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Borisova, S.; Kampmeier, J.; Mussler, G.; Grützmacher, D. [Peter Grünberg Institute-9, Forschungszentrum Jülich, Jülich 52425 (Germany) [Peter Grünberg Institute-9, Forschungszentrum Jülich, Jülich 52425 (Germany); Jülich Aachen Research Alliance, Fundamentals of Future Information Technologies, Jülich 52425 (Germany); Luysberg, M. [Peter Grünberg Institute-5 and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich 52425 (Germany)] [Peter Grünberg Institute-5 and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich 52425 (Germany)

    2013-08-19T23:59:59.000Z

    The atomic structure of topological insulators Bi{sub 2}Te{sub 3} thin films on Si (111) substrates grown in van der Waals mode by molecular beam epitaxy has been investigated by in situ scanning tunneling microscopy and scanning transmission electron microscopy. Besides single and multiple quintuple layer (QL) steps, which are typical for the step-flow mode of growth, a number of 0.4 QL steps is observed. We determine that these steps originate from single steps at the substrate surface causing domain boundaries in the Bi{sub 2}Te{sub 3} film. Due to the peculiar structure of these domain boundaries the domains are stable and penetrate throughout the entire film.

  2. Dislocation reduction via selective-area growth of InN accompanied by lateral growth by rf-plasma-assisted molecular-beam epitaxy

    SciTech Connect (OSTI)

    Kamimura, Jumpei [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 330-0012 (Japan); Kishino, Katsumi; Kikuchi, Akihiko [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 330-0012 (Japan); Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2010-10-04T23:59:59.000Z

    We investigated the selective-area growth (SAG) of InN by rf-plasma-assisted molecular-beam epitaxy using molybdenum (Mo)-mask-patterned sapphire (0001) substrates, which resulted in the formation of regularly arranged N-polar InN microcrystals. Transmission electron microscopy observation confirmed that the laterally grown side areas were nearly dislocation-free, although many threading dislocations (10{sup 9}-10{sup 10} cm{sup -2}) were generated at the InN/sapphire interface and propagated into the center of the InN microcrystals along the crystal c-axis. The laterally grown InN microcrystals exhibited narrow near-IR emission spectra with a peak photon energy of 0.627 eV and a linewidth of 39 meV at room temperature.

  3. Molecular-beam epitaxial growth and characterization of inverted, pulse-doped AlGaAs/InGaAs transistor structures

    SciTech Connect (OSTI)

    Hoke, W.E.; Lyman, P.S.; Brierley, S.K. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    Inverted, pulse-doped AlGaAs/InGaAs pseudomorphic high electron mobility transistor structures were grown by molecular-beam epitaxy. Growth conditions were optimized to improve the quality of the selectively doped AlGaAs layer and to minimize dopant diffusion into the InGaAs channel. The sheet densities and mobilities of the inverted structure were found to be essentially equivalent to those obtained with the normal structure. Shubnikov-de Haas measurements exhibited strong oscillations in the magnetoresistance and plateaus in the Hall resistance. Four optical transitions from the lowest bound electron and hole quantum well states were observed in room-temperature photoluminescence spectra. 15 refs., 4 figs.

  4. In-situ spectroscopic ellipsometry for real time composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Dat, R.; Aqariden, F.; Chandra, D.; Shih, H.D. [Raytheon TI Systems, Sensors and Infrared Lab., Dallas, TX (United States); Duncan, W.M. [Texas Instruments Inc., Dallas, TX (United States). Components and Materials Research Center

    1998-12-31T23:59:59.000Z

    Spectral ellipsometry (SE) was applied to in situ composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy (MBE), and the impact of surface topography of the Hg{sub 1{minus}x}Cd{sub x}Te layers on the accuracy of SE was investigated. Of particular importance is the presence of surface defects, such as voids in MBE-Hg{sub 1{minus}x}Cd{sub x}Te layers. While dislocations do not have any significant impact on the dielectric functions, the experimental data in this work show that MBE-Hg{sub 1{minus}x}Cd{sub x}Te samples having the same composition, but different void densities, have different effective dielectric functions.

  5. Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al{sub 2}O{sub 3} by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sobanska, Marta, E-mail: sobanska@ifpan.edu.pl; Klosek, Kamil; Borysiuk, Jolanta; Kret, Slawomir; Tchutchulasvili, Giorgi; Gieraltowska, Sylwia; Zytkiewicz, Zbigniew R. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-28T23:59:59.000Z

    We report on plasma-assisted molecular beam epitaxial growth of GaN nanowires (NWs) on Si(111) substrates with a thin amorphous Al{sub 2}O{sub 3} buffer layer deposited by atomic layer deposition. Comparison of nucleation kinetics shows that presence of amorphous Al{sub 2}O{sub 3} buffer significantly enhances spontaneous nucleation of GaN NWs. Slower nucleation was observed on partially amorphous silicon nitride films. No growth of NWs was found on sapphire substrate under the same growth conditions which we explain by a low density of defects on monocrystalline substrate surface where NWs may nucleate. Our finding shows that tuning of substrate microstructure is an efficient tool to control rate of self-induced nucleation of GaN NWs.

  6. Highly mismatched N-rich GaN{sub 1-x}Sb{sub x} films grown by low temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Yu, K. M.; Walukiewicz, W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Sarney, W. L.; Svensson, S. P. [US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)] [US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States); Novikov, S. V.; Foxon, C. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)] [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Detert, D.; Zhao, R. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States) [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Denlinger, J. D. [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Dubon, O. D. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States) [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2013-03-11T23:59:59.000Z

    We have grown N-rich, dilute Sb GaN{sub 1-x}Sb{sub x} alloys by low temperature molecular beam epitaxy. At low growth temperature of <100 Degree-Sign C the material loses crystallinity and becomes primarily amorphous with small crystallites of 2-5 nm at a Sb composition of >4 at. %. Despite the different microstructures found for GaN{sub 1-x}Sb{sub x} alloys with different composition, the absorption edge shifts continuously from 3.4 eV (GaN) to close to 1 eV for samples with Sb content >30 at. %. GaN{sub 1-x}Sb{sub x} alloys with less than 5 at. % Sb show sufficient bandgap reduction ({approx}2 eV), making them suitable for photoelectrochemical applications.

  7. Near-infrared intersubband absorption in molecular-beam epitaxy-grown lattice-matched InAlN/GaN superlattices

    SciTech Connect (OSTI)

    Malis, O.; Edmunds, C. [Department of Physics, Binghamton University, Binghamton, New York 13902 (United States); Manfra, M. J.; Sivco, D. L. [Bell Laboratories, Alcatel-Lucent, Murray Hill, New Jersey 07974 (United States)

    2009-04-20T23:59:59.000Z

    Strong near-infrared intersubband absorption is observed directly at room temperature in silicon-doped lattice-matched InAlN/GaN superlattices grown by molecular-beam epitaxy on GaN templates grown by hydride vapor-phase epitaxy. X-ray diffraction characterization of the heterostructures indicates excellent layer thickness uniformity and low interface roughness. For 2-4.5 nm quantum wells, the intersubband transition energies span the technologically relevant range between 2.3 and 2.9 {mu}m. The experimental results are in good agreement with calculations of the transition energies using a conduction band offset of 1 eV and spontaneous polarization of 3 MV/cm.

  8. High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Lang, J. R.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Neufeld, C. J.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2011-03-28T23:59:59.000Z

    High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorption measurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

  9. Surface morphology evolution of m-plane (1100) GaN during molecular beam epitaxy growth: Impact of Ga/N ratio, miscut direction, and growth temperature

    SciTech Connect (OSTI)

    Shao Jiayi; Tang Liang; Malis, Oana [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Edmunds, Colin [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Gardner, Geoff [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Manfra, Michael [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2013-07-14T23:59:59.000Z

    We present a systematic study of morphology evolution of [1100] m-plane GaN grown by plasma-assisted molecular beam epitaxy on free-standing m-plane substrates with small miscut angles towards the -c [0001] and +c [0001] directions under various gallium to nitrogen (Ga/N) ratios at substrate temperatures T = 720 Degree-Sign C and T = 740 Degree-Sign C. The miscut direction, Ga/N ratio, and growth temperature are all shown to have a dramatic impact on morphology. The observed dependence on miscut direction supports the notion of strong anisotropy in the gallium adatom diffusion barrier and growth kinetics. We demonstrate that precise control of Ga/N ratio and substrate temperature yields atomically smooth morphology on substrates oriented towards +c [0001] as well as the more commonly studied -c [0001] miscut substrates.

  10. Step-flow anisotropy of the m-plane GaN (1100) grown under nitrogen-rich conditions by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sawicka, Marta; Siekacz, Marcin; Skierbiszewski, Czeslaw [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Turski, Henryk; Krysko, Marcin; DziePcielewski, Igor; Grzegory, Izabella [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); Smalc-Koziorowska, Julita [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Warsaw University of Technology, Faculty of Material Science and Engineering, Woloska 141, PL-02-507 Warszawa (Poland)

    2011-06-15T23:59:59.000Z

    The homoepitaxial growth of m-plane (1100) GaN was investigated by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions. The surface morphologies as a function of sample miscut were studied, providing evidence for a strong growth anisotropy that is a consequence of the anisotropy of Ga adatom diffusion barriers on the m-plane surface recently calculated ab initio[Lymperakis and Neugebauer, Phys. Rev. B 79, 241308(R) (2009)]. We found that substrate miscut toward [0001] implies a step flow toward <1126> while substrate miscut toward [0001] causes formation of atomic steps either perpendicular or parallel to the [0001] direction, under N-rich conditions at 730 deg C. We describe the growth conditions for achieving atomically flat m-plane GaN layers with parallel atomic steps.

  11. Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

    SciTech Connect (OSTI)

    Furtmayr, Florian; Vielemeyer, Martin; Stutzmann, Martin; Eickhoff, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Arbiol, Jordi [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain); TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, c/ Lluis Sole i Sabaris 1-3, E-08080 Barcelona, CAT (Spain); Estrade, Sonia; Peiro, Francesca; Morante, Joan Ramon [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain)

    2008-08-01T23:59:59.000Z

    The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

  12. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lotsari, A.; Kehagias, Th.; Katsikini, M.; Arvanitidis, J.; Ves, S.; Komninou, Ph.; Dimitrakopulos, G. P., E-mail: gdim@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A. [Department of Physics, Microelectronics Research Group, University of Crete, P.O. Box 2208, GR 71003, Greece and IESL, FORTH, P.O. Box 1385, GR71110 Heraklion (Greece); Christofilos, D. [Physics Division, School of Technology, Aristotle University of Thessaloniki, GR54124 Thessaloniki (Greece)

    2014-06-07T23:59:59.000Z

    Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.

  13. Distance Restraints from Crosslinking Mass Spectrometry: Mining a Molecular Dynamics Simulation Database to Evaluate Lysine-Lysine Distances

    SciTech Connect (OSTI)

    Merkley, Eric D.; Rysavy, Steven; Kahraman, Abdullah; Hafen, Ryan P.; Daggett, Valerie; Adkins, Joshua N.

    2014-03-18T23:59:59.000Z

    Integrative structural biology models the structures of protein complexes that are intractable by classical structural methods (because of extreme size, dynamics, or heterogeneity) by combining computational structural modeling with data from experimental methods. One such method is chemical cross-linking mass spectrometry (XL-MS), in which cross-linked peptides, derived from a covalently cross-linked protein complex and identified by liquid chromatography-mass spectrometry, pinpoint protein residues close in three-dimensional space. The commonly used lysine-reactive N-hydroxysuccinimide ester reagents disuccinimidylsuberate (DSS) and bis(sulfosuccinimidyl)suberate (BS3) have a linker arm that is 11.4 Å long when fully extended. However, XL-MS studies on proteins of known structure frequently report cross-links that exceed this distance. Typically, a tolerance of ~3 Å is added to the theoretical maximum to account for this observation, with little justification for the value chosen. We used the Dynameomics database, a repository of high-quality molecular dynamics simulations of 807 proteins representative of all protein folds, to investigate the change in lysine-lysine distances resulting from native-state dynamics on the time-scale of tens of nanoseconds. We conclude that observed cross-links are consistent with a protein structure if the distance between cross-linked lysine N? atoms is less than the cross-linker length plus 11.3 Å. For DSS or BS3, this corresponds to a C? to C? distance of 30.4 Å. This analysis provides a theoretical basis for the widespread practice of adding a tolerance to the crosslinker length when comparing XL-MS results to structures, and indicates the appropriate values of an XLMS derived distance constraint to use in structural modeling.

  14. Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(0001) by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(000¯1) by Molecular Beam Epitaxy R.Held, B.E. Ishaug, A. Parkhomovsky, A.M. Dabiran, and P (October 7, 1999) GaN(000¯1)filmsweregrownbymolecularbeamepitaxyusingammoniaandelemental

  15. Molecular Science Computing | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Molecular Science Computing Overview Cell Isolation and Systems Analysis Deposition and Microfabrication Mass Spectrometry Microscopy Molecular Science Computing NMR and EPR...

  16. The molecular emissions and the infall motion in the high-mass young stellar object G8.68-0.37

    E-Print Network [OSTI]

    Ren, Zhiyuan; Zhu, Ming; Liu, Tie; Peng, Ruisheng; Shengli,; Qin,; Li, Lixin

    2012-01-01T23:59:59.000Z

    We present a multi-wavelength observational study towards the high-mass young stellar object G8.68-0.37. A single massive gas-and-dust core is observed in the (sub)millimeter continuum and molecular line emissions. We fitted the spectral energy distribution (SED) from the dust continuum emission. The best-fit SED suggests the presence of two components with temperature of $T_{\\rm d}=20$ K and 120 K, respectively. The core has a total mass of up to $1.5\\times10^3$ $M_{\\odot}$ and bolometric luminosity of $2.3\\times10^4 L_{\\odot}$. Both the mass and luminosity are dominated by the cold component ($T_{\\rm d}=20$ K). The molecular lines of C$^{18}$O, C$^{34}$S, DCN, and thermally excited CH$_3$OH are detected in this core. Prominent infall signatures are observed in the $^{12}$CO $(1-0)$ and $(2-1)$. We estimated an infall velocity of 0.45 km s$^{-1}$ and mass infall rate of $7\\times10^{-4} M_{\\odot}$ year$^{-1}$. From the molecular lines, we have found a high DCN abundance and relative abundance ratio to HCN. Th...

  17. Absolute infrared vibrational band intensities of molecular ions determined by direct laser absorption spectroscopy in fast ion beams

    SciTech Connect (OSTI)

    Keim, E.R.; Polak, M.L.; Owrutsky, J.C.; Coe, J.V.; Saykally, R.J. (Department of Chemistry, University of California, Berkeley, CA (USA))

    1990-09-01T23:59:59.000Z

    The technique of direct laser absorption spectroscopy in fast ion beams has been employed for the determination of absolute integrated band intensities ({ital S}{sup 0}{sub {ital v}}) for the {nu}{sub 3} fundamental bands of H{sub 3}O{sup +} and NH{sup +}{sub 4}. In addition, the absolute band intensities for the {nu}{sub 1} fundamental bands of HN{sup +}{sub 2} and HCO{sup +} have been remeasured. The values obtained in units of cm{sup {minus}2} atm{sup {minus}1} at STP are 1880(290) and 580(90) for the {nu}{sub 1} fundamentals of HN{sup +}{sub 2} and HCO{sup +}, respectively; and 4000(800) and 1220(190) for the {nu}{sub 3} fundamentals of H{sub 3}O{sup +} and NH{sup +}{sub 4}, respectively. Comparisons with {ital ab} {ital initio} results are presented.

  18. Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. II. Sub-band-gap luminescence and electron irradiation effects

    SciTech Connect (OSTI)

    Robins, Lawrence H.; Bertness, Kris A.; Barker, Joy M.; Sanford, Norman A.; Schlager, John B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    2007-06-01T23:59:59.000Z

    GaN nanowires with diameters of 50-250 nm, grown by catalyst-free molecular beam epitaxy, were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 to 297 K. Both as-grown samples and dispersions of the nanowires onto other substrates were examined. The properties of the near-band-edge PL and CL spectra were discussed in Part I of this study by [Robins et al. [L. H. Robins, K. A. Bertness, J. M. Barker, N. A. Sanford, and J. B. Schlager, J. Appl. Phys. 101,113505 (2007)]. Spectral features below the band gap, and the effect of extended electron irradiation on the CL, are discussed in Part II. The observed sub-band-gap PL and CL peaks are identified as phonon replicas of the free-exciton transitions, or excitons bound to structural defects or surface states. The defect-related peaks in the nanowires are correlated with luminescence lines previously reported in GaN films, denoted the Y lines [M. A. Reshchikov and H. Morkoc, J. Appl. Phys. 97, 061301 (2005)]. The CL was partially quenched by electron beam irradiation for an extended time; the quenching was stronger for the free and shallow-donor-bound exciton peaks than for the defect-related peaks. The quenching appeared to saturate at high irradiation dose (with final intensity {approx_equal}30% of initial intensity) and was reversible on thermal cycling to room temperature. The electron irradiation-induced quenching of the CL is ascribed to charge injection and trapping phenomena.

  19. Compact hydrogen/helium isotope mass spectrometer

    DOE Patents [OSTI]

    Funsten, Herbert O. (Los Alamos, NM); McComas, David J. (Los Alamos, NM); Scime, Earl E. (Morgantown, WV)

    1996-01-01T23:59:59.000Z

    The compact hydrogen and helium isotope mass spectrometer of the present invention combines low mass-resolution ion mass spectrometry and beam-foil interaction technology to unambiguously detect and quantify deuterium (D), tritium (T), hydrogen molecule (H.sub.2, HD, D.sub.2, HT, DT, and T.sub.2), .sup.3 He, and .sup.4 He concentrations and concentration variations. The spectrometer provides real-time, high sensitivity, and high accuracy measurements. Currently, no fieldable D or molecular speciation detectors exist. Furthermore, the present spectrometer has a significant advantage over traditional T detectors: no confusion of the measurements by other beta-emitters, and complete separation of atomic and molecular species of equivalent atomic mass (e.g., HD and .sup.3 He).

  20. Electrical spin injection into InGaAs/GaAs quantum wells: A comparison between MgO tunnel barriers grown by sputtering and molecular beam epitaxy methods

    SciTech Connect (OSTI)

    Barate, P.; Zhang, T. T.; Vidal, M.; Renucci, P.; Marie, X.; Amand, T. [Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 avenue de Rangueil, 31077 Toulouse (France); Liang, S.; Devaux, X.; Hehn, M.; Mangin, S.; Lu, Y., E-mail: yuan.lu@univ-lorraine.fr [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France); Frougier, J.; Jaffrès, H.; George, J. M. [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 avenue A. Fresnel, 91767 Palaiseau (France); Xu, B.; Wang, Z. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, Beijing 100083 (China); Zheng, Y. [Institut des NanoSciences de Paris, UPMC, CNRS UMR 7588, 4 place Jussieu, 75005 Paris (France); Tao, B. [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Han, X. F. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)

    2014-07-07T23:59:59.000Z

    An efficient electrical spin injection into an InGaAs/GaAs quantum well light emitting diode is demonstrated thanks to a CoFeB/MgO spin injector. The textured MgO tunnel barrier is fabricated by two different techniques: sputtering and molecular beam epitaxy. The maximal spin injection efficiency is comparable for both methods. Additionally, the effect of annealing is also investigated for the two types of samples. Both samples show the same trend: an increase of the electroluminescence circular polarization (P{sub c}) with the increase of annealing temperature, followed by a saturation of P{sub c} beyond 350?°C annealing. Since the increase of P{sub c} starts well below the crystallization temperature of the full CoFeB bulk layer, this trend could be mainly due to an improvement of chemical structure at the top CoFeB/MgO interface. This study reveals that the control of CoFeB/MgO interface is essential for an optimal spin injection into semiconductor.

  1. X-ray magnetic circular dichroism for Co{sub x}Fe{sub 4?x}N (x?=?0, 3, 4) films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Ito, Keita; Sanai, Tatsunori; Yasutomi, Yoko; Toko, Kaoru; Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Zhu, Siyuan; Kimura, Akio [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Takeda, Yukiharu; Saitoh, Yuji [Condensed Matter Science Division, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)

    2014-05-07T23:59:59.000Z

    We evaluated orbital (m{sub orb}) and spin magnetic moments (m{sub spin}) of Co{sub x}Fe{sub 4?x}N (x?=?0, 3, 4) epitaxial thin films grown by molecular beam epitaxy using x-ray magnetic circular dichroism, and discussed the dependence of these values on x. Site-averaged m{sub spin} value of Fe atoms was deduced to be 1.91??{sub B} per atom, and that of Co atoms to be 1.47??{sub B} per atom in Co{sub 3}FeN at 300?K. These values are close to 1.87??{sub B} per Fe atom in Fe{sub 4}N and 1.43??{sub B} per Co atom in Co{sub 4}N, respectively. This result implies that the Fe and Co atoms in the Co{sub 3}FeN films were located both at corner and face-centered sites in the anti-perovskite lattice. Spin magnetic moments per unit cell were decreased linearly with increasing x in Co{sub x}Fe{sub 4?x}N. This tendency is in good agreement with theory predicted by the first-principle calculation.

  2. Energy band alignment of atomic layer deposited HfO{sub 2} on epitaxial (110)Ge grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    The band alignment properties of atomic layer HfO{sub 2} film deposited on epitaxial (110)Ge, grown by molecular beam epitaxy, was investigated using x-ray photoelectron spectroscopy. The cross-sectional transmission electron microscopy exhibited a sharp interface between the (110)Ge epilayer and the HfO{sub 2} film. The measured valence band offset value of HfO{sub 2} relative to (110)Ge was 2.28 {+-} 0.05 eV. The extracted conduction band offset value was 2.66 {+-} 0.1 eV using the bandgaps of HfO{sub 2} of 5.61 eV and Ge bandgap of 0.67 eV. These band offset parameters and the interface chemical properties of HfO{sub 2}/(110)Ge system are of tremendous importance for the design of future high hole mobility and low-power Ge-based metal-oxide transistor devices.

  3. Interfacial structure and defect analysis of nonpolar ZnO films grown on R-plane sapphire by molecular beam epitaxy

    SciTech Connect (OSTI)

    Vennegues, P.; Korytov, M.; Deparis, C.; Zuniga-Perez, J.; Morhain, C. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Chauveau, J. M. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Physics Department, University of Nice Sophia-Antipolis, Parc Valrose 06103 Nice (France)

    2008-04-15T23:59:59.000Z

    The interfacial relationship and the microstructure of nonpolar (11-20) ZnO films epitaxially grown on (1-102) R-plane sapphire by molecular beam epitaxy are investigated by transmission electron microscopy. The already-reported epitaxial relationships [1-100]{sub ZnO} parallel [11-20]{sub sapphire} and <0001>{sub ZnO} parallel [-1101]{sub sapphire} are confirmed, and we have determined the orientation of the Zn-O (cation-anion) bond along [0001]{sub ZnO} in the films as being uniquely defined with respect to a reference surface Al-O bond on the sapphire substrate. The microstructure of the films is dominated by the presence of I{sub 1} basal stacking faults [density=(1-2)x10{sup 5} cm{sup -1}] and related partial dislocations [density=(4-7)x10{sup 10} cm{sup -2}]. It is shown that I{sub 1} basal stacking faults correspond to dissociated perfect dislocations, either c or a+c type.

  4. InGaP/InGaAlP double-heterostructure and multiquantum-well laser diodes grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tanaka, H.; Kawamura, Y.; Nojima, S.; Wakita, K.; Asahi, H.

    1987-03-01T23:59:59.000Z

    Room-temperature continuous-wave (cw) operation is achieved in the MBE (molecular-beam epitaxy)-grown InGaP/InGaAlP double-heterostructure (DH) visible laser diodes with a threshold current of 110 mA. The lasing wavelength and threshold current density under pulsed operation are 666 nm and as low as 3.9 kA/cm/sup 2/, respectively. This result is achieved by the introduction of H/sub 2/ into the growth chamber during growth, the continuous growth from one layer to the next layer, and the introduction of a GaAs buffer layer. InGaP/InGaAlP quantum well structures are also grown. From photoluminescence measurements, the conduction-band discontinuity ..delta..E/sub c/ is estimated to be 0.43 of the band-gap difference ..delta..E/sub g/. Furthermore, the multiquantum-well (MQW) structure is found to be stable under thermal treatment at temperatures as high as 750 /sup 0/C. Room-temperature pulsed operation of InGaP/InGaAlP MQW laser diodes is achieved for the first time. The lasing wavelength is 658 nm with a threshold current density of 7.6 kA/cm/sup 2/. cw operation is also achieved in the MQW laser diodes at -125 /sup 0/C.

  5. High-electron-mobility GaN grown on free-standing GaN templates by ammonia-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Kyle, Erin C. H., E-mail: erinkyle@umail.ucsb.edu; Kaun, Stephen W.; Burke, Peter G.; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wu, Yuh-Renn [Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei City 10617, Taiwan (China)

    2014-05-21T23:59:59.000Z

    The dependence of electron mobility on growth conditions and threading dislocation density (TDD) was studied for n{sup ?}-GaN layers grown by ammonia-based molecular beam epitaxy. Electron mobility was found to strongly depend on TDD, growth temperature, and Si-doping concentration. Temperature-dependent Hall data were fit to established transport and charge-balance equations. Dislocation scattering was analyzed over a wide range of TDDs (?2?×?10{sup 6}?cm{sup ?2} to ?2?×?10{sup 10}?cm{sup ?2}) on GaN films grown under similar conditions. A correlation between TDD and fitted acceptor states was observed, corresponding to an acceptor state for almost every c lattice translation along each threading dislocation. Optimized GaN growth on free-standing GaN templates with a low TDD (?2?×?10{sup 6}?cm{sup ?2}) resulted in electron mobilities of 1265 cm{sup 2}/Vs at 296?K and 3327 cm{sup 2}/Vs at 113?K.

  6. Growth diagram of N-face GaN (0001{sup ¯}) grown at high rate by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Okumura, Hironori, E-mail: okumura@engineering.ucsb.edu; McSkimming, Brian M.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States); Huault, Thomas; Chaix, Catherine [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)] [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)

    2014-01-06T23:59:59.000Z

    N-face GaN was grown on free-standing GaN (0001{sup ¯}) substrates at a growth rate of 1.5??m/h using plasma-assisted molecular beam epitaxy. Difference in growth rate between (0001{sup ¯}) and (0001) oriented GaN depends on nitrogen plasma power, and the (0001{sup ¯}) oriented GaN had only 70% of the growth rate of the (0001) oriented GaN at 300?W. Unintentional impurity concentrations of silicon, carbon, and oxygen were 2?×?10{sup 15}, 2?×?10{sup 16}, and 7?×?10{sup 16}?cm{sup ?3}, respectively. A growth diagram was constructed that shows the dependence of the growth modes on the difference in the Ga and active nitrogen flux, ?{sub Ga}????{sub N*}, and the growth temperature. At high ?{sub Ga}????{sub N*} (?{sub Ga}????{sub N*}), two-dimensional (step-flow and layer-by-layer) growth modes were realized. High growth temperature (780?°C) expanded the growth window of the two-dimensional growth modes, achieving a surface with rms roughness of 0.48?nm without Ga droplets.

  7. Molecular beam epitaxy and structural anisotropy of m-plane InN grown on free-standing GaN

    SciTech Connect (OSTI)

    Koblmueller, G.; Hirai, A.; Wu, F.; Gallinat, C. S.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Metcalfe, G. D.; Shen, H.; Wraback, M. [U. S. Army Research Laboratory, Sensors and Electron Devices Directorate, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2008-10-27T23:59:59.000Z

    This study reports on the growth of high-quality nonpolar m-plane [1100] InN films on free-standing m-plane GaN substrates by plasma-assisted molecular beam epitaxy. Optimized growth conditions (In/N ratio {approx}1 and T=390-430 deg. C) yielded very smooth InN films with undulated features elongated along the [1120] orientation. This directionality is associated with the underlying defect structure shown by the anisotropy of x-ray rocking curve widths parallel to the [1120] (i.e., 0.24 deg. - 0.34 deg.) and [0001] (i.e., 1.2 deg. - 2.7 deg.) orientations. Williamson-Hall analysis and transmission electron microscopy identified the mosaic tilt and lateral coherence length and their associations with different densities of dislocations and basal-plane stacking faults. Ultimately, very low band gap energies of {approx}0.67 eV were measured by optical absorption similar to the best c-plane InN.

  8. Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect (OSTI)

    Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E. [CEA-Grenoble, INAC/SP2M/NPSC, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Doisneau, B. [SIMaP, Grenoble INP, Domaine Universitaire, BP 75, 38402 Saint Martin d'Heres (France); Sarigiannidou, E. [LMGP, Grenoble INP, 3 Parvis Louis Neel, BP 257, 38016 Grenoble cedex 1 (France)

    2011-08-01T23:59:59.000Z

    We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  9. Growth kinetics of AlN and GaN films grown by molecular beam epitaxy on R-plane sapphire substrates

    SciTech Connect (OSTI)

    Chandrasekaran, R.; Moustakas, T. D. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Ozcan, A. S.; Ludwig, K. F. [Physics Department, Boston University, Boston, Massachusetts 02215 (United States); Zhou, L.; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2010-08-15T23:59:59.000Z

    This paper reports the growth by molecular beam epitaxy of AlN and GaN thin films on R-plane sapphire substrates. Contrary to previous findings that GaN grows with its (1120) A-plane parallel to the (1102) R-plane of sapphire, our results indicate that the crystallographic orientation of the III-nitride films is strongly dependent on the kinetic conditions of growth for the GaN or AlN buffer layers. Thus, group III-rich conditions for growth of either GaN or AlN buffers result in nitride films having (1120) planes parallel to the sapphire surface, and basal-plane stacking faults parallel to the growth direction. The growth of these buffers under N-rich conditions instead leads to nitride films with (1126) planes parallel to the sapphire surface, with inclined c-plane stacking faults that often terminate threading dislocations. Moreover, electron microscope observations indicate that slight miscut ({approx}0.5 deg. ) of the R-plane sapphire substrate almost completely suppresses the formation of twinning defects in the (1126) GaN films.

  10. Transport and optical properties of c-axis oriented wedge shaped GaN nanowall network grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Bhasker, H. P.; Dhar, S. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra-400076 (India); Thakur, Varun; Kesaria, Manoj; Shivaprasad, S. M. [Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Bangalore- 560064 (India)

    2014-02-21T23:59:59.000Z

    The transport and optical properties of wedge-shaped nanowall network of GaN grown spontaneously on cplane sapphire substrate by Plasma-Assisted Molecular Beam Epitaxy (PAMBE) show interesting behavior. The electron mobility at room temperature in these samples is found to be orders of magnitude higher than that of a continuous film. Our study reveals a strong correlation between the mobility and the band gap in these nanowall network samples. However, it is seen that when the thickness of the tips of the walls increases to an extent such that more than 70% of the film area is covered, it behaves close to a flat sample. In the sample with lower surface coverage (?40% and ?60%), it was observed that the conductivity, mobility as well as the band gap increase with the decrease in the average tip width of the walls. Photoluminescence (PL) experiments show a strong and broad band edge emission with a large (as high as ? 90 meV) blue shift, compared to that of a continuous film, suggesting a confinement of carriers on the top edges of the nanowalls. The PL peak width remains wide at all temperatures suggesting the existence of a high density of tail states at the band edge, which is further supported by the photoconductivity result. The high conductivity and mobility observed in these samples is believed to be due to a “dissipation less” transport of carriers, which are localized at the top edges (edge states) of the nanowalls.

  11. High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels

    SciTech Connect (OSTI)

    Koblmueller, G. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Chu, R. M.; Raman, A.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States)

    2010-02-15T23:59:59.000Z

    We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr{sub 4} to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm{sup 2}/V s and the dc drain current reached {approx}1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods.

  12. Indium and impurity incorporation in InGaN films on polar, nonpolar, and semipolar GaN orientations grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Browne, David A.; Young, Erin C.; Lang, Jordan R.; Hurni, Christophe A.; Speck, James S. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

    2012-07-15T23:59:59.000Z

    The effects of NH{sub 3} flow, group III flux, and substrate growth temperature on indium incorporation and surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. The incorporation of unintentional impurity elements (H, C, O) in InGaN films was studied as a function of growth temperature for growth on polar (0001) GaN on sapphire templates, nonpolar (1010) bulk GaN, and semipolar (1122), (2021) bulk GaN substrates. Enhanced indium incorporation was observed on both (1010) and (2021) surfaces relative to c-plane, while reduced indium incorporation was observed on (1122) for co-loaded conditions. Indium incorporation was observed to increase with decreasing growth temperature for all planes, while being relatively unaffected by the group III flux rates for a 1:1 Ga:In ratio. Indium incorporation was found to increase at the expense of a decreased growth rate for higher ammonia flows; however, smooth surface morphology was consistently observed for growth on semipolar orientations. Increased concentrations of oxygen and hydrogen were observed on semipolar and nonpolar orientations with a clear trend of increased hydrogen incorporation with indium content.

  13. Study of Gd-doped Bi{sub 2}Te{sub 3} thin films: Molecular beam epitaxy growth and magnetic properties

    SciTech Connect (OSTI)

    Harrison, S. E.; Huo, Y.; Harris, J. S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Collins-McIntyre, L. J.; Hesjedal, T., E-mail: Thorsten.Hesjedal@physics.ox.ac.uk [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Li, S. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Baker, A. A. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire OX11 0DE (United Kingdom); Shelford, L. R.; Laan, G. van der [Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire OX11 0DE (United Kingdom); Pushp, A.; Parkin, S. S. P. [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-01-14T23:59:59.000Z

    Incorporation of magnetic dopants into topological insulators to break time-reversal symmetry is a prerequisite for observing the quantum anomalous Hall (QAHE) effect and other novel magnetoelectric phenomena. GdBiTe{sub 3} with a Gd:Bi ratio of 1:1 is a proposed QAHE system, however, the reported solubility limit for Gd doping into Bi{sub 2}Te{sub 3} bulk crystals is between ?0.01 and 0.05. We present a magnetic study of molecular beam epitaxy grown (Gd{sub x}Bi{sub 1–x}){sub 2}Te{sub 3} thin films with a high Gd concentration, up to x ? 0.3. Magnetometry reveals that the films are paramagnetic down to 1.5?K. X-ray magnetic circular dichroism at the Gd M{sub 4,5} edge at 1.5?K reveals a saturation field of ?6?T, and a slow decay of the magnetic moment with temperature up to 200?K. The Gd{sup 3+} ions, which are substitutional on Bi sites in the Bi{sub 2}Te{sub 3} lattice, exhibit a large atomic moment of ?7??{sub B}, as determined by bulk-sensitive superconducting quantum interference device magnetometry. Surface oxidation and the formation of Gd{sub 2}O{sub 3} lead to a reduced moment of ?4??{sub B} as determined by surface-sensitive x-ray magnetic circular dichroism. Their large atomic moment makes these films suitable for incorporation into heterostructures, where interface polarization effects can lead to the formation of magnetic order within the topological insulators.

  14. Strain control of AlGaN/GaN high electron mobility transistor structures on silicon (111) by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Aidam, Rolf; Diwo, Elke; Rollbuehler, Nicola; Kirste, Lutz; Benkhelifa, Fouad [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

    2012-06-01T23:59:59.000Z

    This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN-based high electron mobility transistor structures grown on 4 in. Si (111) substrates. In situ measurements of wafer curvature during growth proved to be a very powerful method to analyze the buffer layer's thickness dependent strain. The Ga/N ratio at the beginning of growth of the GaN buffer layer is the critical parameter to control the compressive strain of the entire grown structure. An engineered amount of compressive strain must be designed into the structure to perfectly compensate for the tensile strain caused by differences in the thermal expansion coefficient between the epi-layer and substrate during sample cool down from growth temperatures. A maximum film thickness of 4.2 {mu}m was achieved without the formation of any cracks and a negligible bow of the wafers below 10 {mu}m. Measurement of the as-grown wafers revealed depth profiles of the charge carrier concentration comparable to values achieved on SiC substrates and mobility values of the two dimensional electron gas in the range 1230 to 1350 cm{sup 2}/Vs at a charge carrier concentration of 6.5-7 10{sup 12}/cm{sup 2}. First results on processed wafers with 2 {mu}m thick buffer layer indicate very promising results with a resistance of the buffer, measured on 200 {mu}m long contacts with 15 {mu}m pitch, in the range of R > 10{sup 9}{Omega} at 100 V and breakdown voltages up to 550 V.

  15. The use of a high intensity neutrino beam from the ESS proton linac for measurement of neutrino CP violation and mass hierarchy

    E-Print Network [OSTI]

    E. Baussan; M. Dracos; T. Ekelof; E. Fernandez Martinez; H. Ohman; N. Vassilopoulos

    2013-02-09T23:59:59.000Z

    It is proposed to complement the ESS proton linac with equipment that would enable the production, concurrently with the production of the planned ESS beam used for neutron production, of a 5 MW beam of 10$^{23}$ 2.5 GeV protons per year in microsecond short pulses to produce a neutrino Super Beam, and to install a megaton underground water Cherenkov detector in a mine to detect $\

  16. The use the a high intensity neutrino beam from the ESS proton linac for measurement of neutrino CP violation and mass hierarchy

    E-Print Network [OSTI]

    Baussan, E; Ekelof, T; Martinez, E Fernandez; Ohman, H; Vassilopoulos, N

    2012-01-01T23:59:59.000Z

    It is proposed to complement the ESS proton linac with equipment that would enable the production, concurrently with the production of the planned ESS beam used for neutron production, of a 5 MW beam of 10$^{23}$ 2.5 GeV protons per year in microsecond short pulses to produce a neutrino Super Beam, and to install a megaton underground water Cherenkov detector in a mine to detect $\

  17. Molecular Characterization of Organosulfates in Organic Aerosols from Shanghai and Los Angeles Urban Areas by Nanospray-Desorption Electrospray Ionization High-Resolution Mass Spectrometry

    SciTech Connect (OSTI)

    Tao, Shikang; Lu, Xiaohui; Levac, Nicole A.; Bateman, Adam P.; Nguyen, Tran B.; Bones, David L.; Nizkorodov, Sergey; Laskin, Julia; Laskin, Alexander; Yang, Xin

    2014-08-21T23:59:59.000Z

    Aerosol samples collected in the urban areas of Shanghai and Los Angeles were analyzed by nanospray-desorption electrospray ionization mass spectrometry (nano-DESI MS) with high mass resolution (m/?m=100,000). Solvent mixtures of acetonitrile/water and acetonitrile/toluene were used to extract and ionize polar and non-polar compounds, respectively. A diverse mixture of oxygenated hydrocarbons, organosulfates, organonitrates, and organics with reduced nitrogen were detected in the Los Angeles sample. Majority of the organics in the Shanghai sample were detected as organosulfates. The dominant organosulfates in the two samples have distinctly different molecular characteristics. Specifically, organosulfates in the Los Angeles sample were dominated by isoprene- or monoterpene-derived products, while organosulfates of yet unknown origin in the Shanghai sample had distinctive characteristics of long aliphatic carbon chains and low degree of oxidation and unsaturation. The use of acetonitrile/toluene solvent facilitated identification of this type of organosulfates, suggesting they could be missed in previous studies relying on sample extraction using common polar solvents. The high molecular weight and low degree of unsaturation and oxidization of the organosulfates detected in the Shanghai sample suggest that they may act as surfactants, and plausibly affect the surface tension and hygroscopicity of the atmospheric particulate matter. We propose that direct esterification of carbonyl or hydroxyl compounds by sulfates or sulfuric acid in liquid phase could be the formation pathway of these special organosulfates. Long-chain alkanes from vehicle emissions might be their precursors.

  18. Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases

    SciTech Connect (OSTI)

    Kim, Hyunjung [University of Tennessee, Knoxville (UTK); Kaczmarski, Krzysztof [University of Tennessee and Rzeszow University of Technology, Poland; Guiochon, Georges A [ORNL

    2006-03-01T23:59:59.000Z

    The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

  19. Effects of gallium doping on properties of a-plane ZnO films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Han, Seok Kyu; Lee, Hyo Sung; Lim, Dong Seok; Hong, Soon-Ku; Yoon, Nara; Oh, Dong-Cheol; Ahn, Byung Jun; Song, Jung-Hoon; Yao, Takafumi [Department of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Department of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea and Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Center for Optoelectronic Materials and Devices, Department of Defense Science and Technology, Hoseo University, Cheonan 330-713 (Korea, Republic of); Department of Physics, Kongju National University, Gongju 314-701 (Korea, Republic of); Center for Interdisciplinary Research, Tohoku University, Sendai 980-8587 (Japan)

    2011-05-15T23:59:59.000Z

    The authors report on the structural, optical, and electrical properties of Ga-doped a-plane (1120) ZnO films grown by plasma-assisted molecular beam epitaxy. Ga doping level was controlled by changing the Ga cell temperatures from 350 to 470 deg. C with an interval of 30 deg. C. With up to Ga cell temperatures of 440 deg. C, single crystalline Ga-doped a-plane ZnO films were grown; however, the sample with a Ga cell temperature of 470 deg. C showed polycrystalline features. The typical striated surface morphology normally observed from undoped ZnO films disappeared with Ga doping. ZnO films doped with Ga cell temperatures up to 440 deg. C did not show a significant change in full width at half maximum (FWHM) values of (1120) x-ray rocking curves by doping. The smallest FWHM values were 0.433 deg. ({phi}=90 deg.) and 0.522 deg. ({phi}=0 deg. ) for the sample with a Ga cell temperature of 350 deg. C. The polycrystalline ZnO film with excessive Ga doping at the Ga cell temperature of 470 deg. C showed significantly increased FWHM values. Hall measurements at room temperature (RT) revealed that electron concentration began to be saturated at the Ga cell temperature of 440 deg. C and electron mobility was drastically reduced at the Ga cell temperature of 470 deg. C. The carrier concentration of Ga-doped ZnO films were controlled from 7.2x10{sup 18} to 3.6x10{sup 20} cm{sup -3}. Anisotropic electrical properties (carrier concentration and Hall mobility) were observed in measurements by the van der Pauw method depending on the direction (c- or m-direction) for the undoped sample but not observed for the doped samples. RT photoluminescence (PL) spectra from the Ga-doped single crystalline ZnO films showed dominant near band edge (NBE) emissions with negligibly deep level emission. The NBE intensity in PL spectra increases with Ga doping.

  20. Deep levels in a-plane, high Mg-content Mg{sub x}Zn{sub 1-x}O epitaxial layers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Guer, Emre [Department of Physics, Faculty of Science, Atatuerk University, Erzurum 25240 (Turkey); 205 Dreese Laboratory, Department of Electrical and Computer Engineering, The Ohio State University, 2015 Neil Avenue, Columbus, Ohio 43210-1272 (United States); Tabares, G.; Hierro, A. [Dpto. Ingenieria Electronica and ISOM, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Arehart, A.; Ringel, S. A. [205 Dreese Laboratory, Department of Electrical and Computer Engineering, Ohio State University, 2015 Neil Avenue, Columbus, Ohio 43210-1272 (United States); Chauveau, J. M. [CRHEA-CNRS, 06560 Valbonne (France); University of Nice Sophia Antipolis, ParcValrose, 06102 Nice Cedex 2 (France)

    2012-12-15T23:59:59.000Z

    Deep level defects in n-type unintentionally doped a-plane Mg{sub x}Zn{sub 1-x}O, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of Mg{sub x}Zn{sub 1-x}O were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of E{sub c} - 1.4 eV, 2.1 eV, 2.6 V, and E{sub v} + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at E{sub c} - 2.1 eV, E{sub v} + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at E{sub v} + 0.3 eV and E{sub c} - 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the E{sub v} + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the E{sub c} - 1.4 eV and E{sub c} - 2.6 eV levels in Mg alloyed samples.

  1. High resistivity LT-In{sub 0.47}Ga{sub 0.53}P grown by gas source molecular beam epitaxy

    SciTech Connect (OSTI)

    He, Y.; El-Masry, N.A. [North Carolina State Univ., Raleigh, NC (United States); Look, D.C. [Wright State Univ., Dayton, OH (United States)] [and others

    1993-12-01T23:59:59.000Z

    Low-temperature (LT) growth of In{sub 0.47}Ga{sub 0.53}P was carried out in the temperature range from 200 to 260{degrees}C by gas source molecular beam epitaxy using solid Ga and In and precracked PH{sub 3}. The Hall measurements of the as-grown film showed a resistivity of {approximately}10{sup 6} {Omega}-cm at room temperature whereas the annealed film (at 600{degrees}C for 1 h) had at least three orders of magnitude, higher resistivity. The Hall measurements, also, indicated activation energies of {approximately}0.5 and 0.8 eV for the as-grown and annealed samples, respectively. Double-crystal x-ray diffraction showed that the LT-InGaP films had {approximately}47% In composition. The angular separation, {Delta}{theta}, between the GaAs substrate and the as-grown LT-InGaP film on (004) reflection was increased by 20 arc-s after annealing. In order to better understand the annealing effect, a LT-InGaP film was grown on an InGaP film grown at 480{degrees}C. While annealing did not have any effect on the HT-InGaP peak position, the LT-InGaP peak was shifted toward the HT-InGaP peak, indicating a decrease in the LT-InGaP lattice parameter. Cross-sectional transmission electron microscopy indicates the presence of phase separation in LT-InGaP films, manifested in the form of a {open_quote}precipitate-like{close_quotes} microstructure. The analytical scanning transmission electron microscopy analysis of the LT-InGaP film revealed a group-V nonstoichiometric deviation of {approximately}0.5 at% P. To our knowledge, this is the first report about the growth and characterization of LT-InGaP films. 12 refs., 5 figs.

  2. Growth of In{sub 2}O{sub 3}(100) on Y-stabilized ZrO{sub 2}(100) by O-plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Bourlange, A.; Payne, D. J.; Egdell, R. G.; Foord, J. S.; Edwards, P. P.; Jones, M. O. [Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (United Kingdom); Schertel, A. [Carl Zeiss SMT AG, Carl-Zeiss-Strasse 56, 73447 Oberkochen (Germany); Dobson, P. J. [Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Kidlington, Oxon OX5 1PF (United Kingdom); Hutchison, J. L. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2008-03-03T23:59:59.000Z

    Thin films of In{sub 2}O{sub 3} have been grown on Y-stabilized ZrO{sub 2}(100) by oxygen plasma assisted molecular beam epitaxy with a substrate temperature of 650 deg. C. Ordered epitaxial growth was confirmed by high resolution transmission electron microscopy. The position of the valence band onset in the x-ray photoemission spectra of the epitaxial films is found to be inconsistent with the widely quoted value of 3.75 eV for the fundamental bandgap of In{sub 2}O{sub 3} and suggests a revised value of 2.67 eV.

  3. High characteristics temperature of strain-compensated 1.3 {micro}m InAsP/InGaP/InP multi-quantum well lasers grown by all solid source molecular beam epitaxy

    SciTech Connect (OSTI)

    Savolainen, P.; Toivonen, M.; Salokatve, A. [Tampere Univ. of Technology (Finland). Dept. of Physics; Asonen, H. [Tutcore Ltd., Tampere (Finland); Murison, R. [EG and G Optoelectronics Canada, Vaudreuil, Quebec (Canada)

    1996-12-31T23:59:59.000Z

    The present lasers have very good characteristic temperature values for the threshold current. In order to maintain such performance in cw mode, one should either use narrow waveguide (buried) type of laser structure or reduce the number of QWs. If the number of QW`s is reduced, total gain decreases and this should be compensated by increasing the optical confinement factor. In this paper the authors have demonstrated the suitability of InAsP/InGaP strain-compensated system for high temperature lasers emitting 1.3 {micro}m and the potential of all solid source molecular beam epitaxy for growth of optoelectronic devices.

  4. Metallic beam development for the Facility for Rare Isotope Beam

    SciTech Connect (OSTI)

    Machicoane, Guillaume, E-mail: machicoa@nscl.msu.edu; Cole, Dallas; Leitner, Daniela; Neben, Derek; Tobos, Larry [Facility for Rare Isotope Beam, Michigan State University, East Lansing, Michigan 48824 (United States)] [Facility for Rare Isotope Beam, Michigan State University, East Lansing, Michigan 48824 (United States)

    2014-02-15T23:59:59.000Z

    The Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) will accelerate a primary ion beam to energies beyond 200 MeV/u using a superconducting RF linac and will reach a maximum beam power of 400 kW on the fragmentation target. The beam intensity needed from the ECR ion source is expected to be between 0.4 and 0.5 emA for most medium mass to heavy mass elements. Adding to the challenge of reaching the required intensity, an expanded list of primary beams of interest has been established based on the production rate and the number of isotope beams that could be produced with FRIB. We report here on the development done for some of the beam in the list including mercury (natural), molybdenum ({sup 98}Mo), and selenium ({sup 82}Ser)

  5. Herschel Key Program, "Dust, Ice, and Gas In Time" (DIGIT): the origin of molecular and atomic emission in low-mass protostars in Taurus

    E-Print Network [OSTI]

    Lee, Jeong-Eun; Lee, Seokho; Evans, Neal J; Green, Joel D

    2014-01-01T23:59:59.000Z

    Six low-mass embedded sources (L1489, L1551-IRS5, TMR1, TMC1-A, L1527, and TMC1) in Taurus have been observed with Herschel-PACS to cover the full spectrum from 50 to 210 $\\mu$m as part of the Herschel key program, "Dust, Ice, and Gas In Time (DIGIT)". The relatively low intensity of the interstellar radiation field surrounding Taurus minimizes contamination of the [C II] emission associated with the sources by diffuse emission from the cloud surface, allowing study of the [C II] emission from the source. In several sources, the [C II] emission is distributed along the outflow, as is the [O I] emission. The atomic line luminosities correlate well with each other, as do the molecular lines, but the atomic and molecular lines correlate poorly. The relative contribution of CO to the total gas cooling is constant at $\\sim$30 %, while the cooling fraction by H$_2$O varies from source to source, suggesting different shock properties resulting in different photodissociation levels of H$_2$O. The gas with a power-law...

  6. Probing Molecular Associations of Field-Collected and Laboratory-Generated SOA with Nano-DESI High-Resolution Mass Spectrometry

    SciTech Connect (OSTI)

    O'Brien, Rachel E.; Nguyen, Tran B.; Laskin, Alexander; Laskin, Julia; Hayes, Patrick L.; Liu, Shang; Jimenez, Jose L.; Russell, Lynn M.; Nizkorodov, Sergey; Goldstein, Allen H.

    2013-01-30T23:59:59.000Z

    Aerosol samples from the 2010 CalNex field study in Bakersfield (BF) and Los Angeles (LA) were analyzed using positive mode nanospray-desorption electrospray ionization mass spectrometry (nano-DESI-MS). Secondary organic aerosol (SOA) produced in a photochemical chamber by photooxidation of diesel (DSL) fuel and isoprene (ISO) under humid, high-NOx conditions, was analyzed for comparison. Three groups of organic compounds with zero, one, or two nitrogen atoms in their molecular formulas (0N, 1N, 2N) were compared in detail. The composition of ambient SOA exhibited greater overlap with DSL than with ISO. The overlap of the chamber experiments with the BF data was relatively consistent throughout the day while the overlap with LA data increased significantly in the noon-6pm sample, consistent with the SOA plume arriving from downtown Los Angeles. BF samples were more oxidized, contained more organic nitrogen, and had more overlap with the chamber data compared to LA samples. The addition of gaseous ammonia (NH3) to the DSL experiment was necessary to generate many of the 2N compounds observed in BF. This analysis demonstrates that DSL and ISO were important sources but cannot account for all of the observed ambient compounds indicating that other sources of organics were also likely important.

  7. Two-dimensional weak anti-localization in Bi{sub 2}Te{sub 3} thin film grown on Si(111)-(7 Multiplication-Sign 7) surface by molecular beam epitaxy

    SciTech Connect (OSTI)

    Roy, Anupam; Guchhait, Samaresh; Sonde, Sushant; Dey, Rik; Pramanik, Tanmoy; Rai, Amritesh; Movva, Hema C. P.; Banerjee, Sanjay K. [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States)] [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States); Colombo, Luigi [Texas Instruments, 12500 TI Boulevard, Dallas, Texas 75266 (United States)] [Texas Instruments, 12500 TI Boulevard, Dallas, Texas 75266 (United States)

    2013-04-22T23:59:59.000Z

    We report on low temperature transport studies of Bi{sub 2}Te{sub 3} topological insulator thin films grown on Si(111)-(7 Multiplication-Sign 7) surface by molecular beam epitaxy. A sharp increase in the magnetoresistance with magnetic field at low temperature indicates the existence of weak anti-localization. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model, and the extracted phase coherence length shows a power-law dependence with temperature indicating the existence of a two-dimensional system. An insulating ground state has also been observed at low temperature showing a logarithmic divergence of the resistance that appears to be the influence of electron-electron interaction in a two-dimensional system.

  8. Structural properties of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

    SciTech Connect (OSTI)

    Liu, X.; Leiner, J.; Dobrowolska, M.; Furdyna, J. K. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Fan, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); Zhang, Y.-H. [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Cao, H.; Chen, Y. P. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Kirby, B. J. [Center for Neutron Research, NIST, Gaithersburg, Maryland 20899 (United States)

    2011-10-24T23:59:59.000Z

    Thin films of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.

  9. Molecular Beam Epitaxial Growth of Bi2Te3 and Sb2Te3 Topological Insulators on GaAs (111) Substrates: A Potential Route to Fabricate Topological Insulator p-n Junction

    E-Print Network [OSTI]

    Zhaoquan Zeng; Timothy A. Morgan; Dongsheng Fan; Chen Li; Yusuke Hirono; Xian Hu; Yanfei Zhao; Joon Sue Lee; Zhiming M. Wang; Jian Wang; Shuiqing Yu; Michael E. Hawkridge; Mourad Benamara; Gregory J. Salamo

    2013-03-11T23:59:59.000Z

    High quality Bi2Te3 and Sb2Te3 topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi2Te3 and Sb2Te3 films. Hall and magnetoresistance measurements indicate that p type Sb2Te3 and n type Bi2Te3 topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

  10. Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn{sub 1-x}Mg{sub x}O layers by molecular beam epitaxy

    SciTech Connect (OSTI)

    Xia, Y.; Vinter, B.; Chauveau, J.-M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France); University of Nice Sophia-Antipolis, 06103 Nice (France); Brault, J.; Nemoz, M.; Teisseire, M.; Leroux, M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France)

    2011-12-26T23:59:59.000Z

    Nonpolar (1120) Al{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (1120) Zn{sub 0.74}Mg{sub 0.26}O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.

  11. Elimination of columnar microstructure in N-face InAlN, lattice-matched to GaN, grown by plasma-assisted molecular beam epitaxy in the N-rich regime

    SciTech Connect (OSTI)

    Ahmadi, Elaheh; Wienecke, Steven; Keller, Stacia; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Shivaraman, Ravi; Wu, Feng; Kaun, Stephen W.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-02-17T23:59:59.000Z

    The microstructure of N-face InAlN layers, lattice-matched to GaN, was investigated by scanning transmission electron microscopy and atom probe tomography. These layers were grown by plasma-assisted molecular beam epitaxy (PAMBE) in the N-rich regime. Microstructural analysis shows an absence of the lateral composition modulation that was previously observed in InAlN films grown by PAMBE. A room temperature two-dimensional electron gas (2DEG) mobility of 1100 cm{sup 2}/V s and 2DEG sheet charge density of 1.9?×?10{sup 13}?cm{sup ?2} was measured for N-face GaN/AlN/GaN/InAlN high-electron-mobility transistors with lattice-matched InAlN back barriers.

  12. Role of an ultra-thin AlN/GaN superlattice interlayer on the strain engineering of GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Shen, X. Q.; Takahashi, T.; Matsuhata, H.; Ide, T.; Shimizu, M. [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan)] [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan); Rong, X.; Chen, G.; Wang, X. Q.; Shen, B. [School of Physics, Peking University, Beijing 100871 (China)] [School of Physics, Peking University, Beijing 100871 (China)

    2013-12-02T23:59:59.000Z

    We investigate the role of an ultra-thin AlN/GaN superlattice interlayer (SL-IL) on the strain engineering of the GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy. It is found that micro-cracks limitted only at the SL-IL position are naturally generated. These micro-cracks play an important role in relaxing the tensile strain caused by the difference of the coefficient of thermal expansion between GaN and Si and keeping the residual strain in the crack-free GaN epilayers resulted from the SL-IL during the growth. The mechanism understanding of the strain modulation by the SL-IL in the GaN epilayers grown on Si substrates makes it possible to design new heterostructures of III-nitrides for optic and electronic device applications.

  13. Imaging mass spectrometer with mass tags

    DOE Patents [OSTI]

    Felton, James S.; Wu, Kuang Jen; Knize, Mark G.; Kulp, Kristen S.; Gray, Joe W.

    2010-06-01T23:59:59.000Z

    A method of analyzing biological material by exposing the biological material to a recognition element, that is coupled to a mass tag element, directing an ion beam of a mass spectrometer to the biological material, interrogating at least one region of interest area from the biological material and producing data, and distributing the data in plots.

  14. Imaging mass spectrometer with mass tags

    DOE Patents [OSTI]

    Felton, James S.; Wu, Kuang Jen J.; Knize, Mark G.; Kulp, Kristen S.; Gray, Joe W.

    2013-01-29T23:59:59.000Z

    A method of analyzing biological material by exposing the biological material to a recognition element, that is coupled to a mass tag element, directing an ion beam of a mass spectrometer to the biological material, interrogating at least one region of interest area from the biological material and producing data, and distributing the data in plots.

  15. Luminosity and beam-beam

    E-Print Network [OSTI]

    Papotti, G; Trad, G

    We report on observations on luminosity evolution and beam-beam interaction from the 2011 physics run. Extrapolations for 2012 are attempted and a list of desired studies and machine developments is included.

  16. InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular-beam epitaxy with a valved phosphorus cracker

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular; accepted 17 November 1995 The growth and device characterization of an InGaP/GaAs double-quality phosphorus-containing compounds.1­4 The growth of high-performance InGaP/ GaAs and InGaAs/InP single

  17. Low energy beta-beams

    E-Print Network [OSTI]

    Cristina Volpe

    2009-11-13T23:59:59.000Z

    The main goal of a beta-beam facility is to determine the possible existence of CP violation in the lepton sector, the value of the third neutrino mixing angle and the mass hierarchy. Here we argue that a much broader physics case can be covered since the beta-beam concept can also be used to establish a low energy beta-beam facility. We discuss that the availability of neutrino beams in the 100 MeV energy range offers a unique opportunity to perform neutrino scattering experiments of interest for nuclear physics, for the study of fundamental interactions and of core-collapse supernova physics.

  18. Molecular Characterization of Biomass Burning Aerosols Using...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Biomass Burning Aerosols Using High Resolution Mass Spectrometry. Molecular Characterization of Biomass Burning Aerosols Using High Resolution Mass Spectrometry. Abstract: Chemical...

  19. Airfoil sampling of a pulsed Laval beam with tunable vacuum ultraviolet (VUV) synchrotron ionization quadrupole mass spectrometry: Application to low--temperature kinetics and product detection

    SciTech Connect (OSTI)

    Soorkia, Satchin; Liu, Chen-Lin; Savee, John D.; Ferrell, Sarah J.; Leone, Stephen R.; Wilson, Kevin R.

    2011-10-12T23:59:59.000Z

    A new pulsed Laval nozzle apparatus with vacuum ultraviolet (VUV) synchrotron photoionization quadrupole mass spectrometry is constructed to study low-temperature radicalneutralchemical reactions of importance for modeling the atmosphere of Titan and the outer planets. A design for the sampling geometry of a pulsed Laval nozzle expansion has beendeveloped that operates successfully for the determination of rate coefficients by time-resolved mass spectrometry. The new concept employs airfoil sampling of the collimated expansion withexcellent sampling throughput. Time-resolved profiles of the high Mach number gas flow obtained by photoionization signals show that perturbation of the collimated expansion by theairfoil is negligible. The reaction of C2H with C2H2 is studied at 70 K as a proof-of-principle result for both low-temperature rate coefficient measurements and product identification basedon the photoionization spectrum of the reaction product versus VUV photon energy. This approach can be used to provide new insights into reaction mechanisms occurring at kinetic ratesclose to the collision-determined limit.

  20. Two-dimensional imaging of laser-induced fluorescence: OH in a plasma-generated molecular beam scattering from a silicon surface

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States)

    1996-02-01T23:59:59.000Z

    Low-temperature plasmas are used for a wide variety of materials processing applications, especially in the fabrication of microelectronic devices. Thus plasma processes, such as etching, deposition, and cleaning, are the subject of much current research. However, achieving a detailed understanding of such systems, especially for computer simulations, requires a great deal of kinetic information about the physics and chemistry. One particular aspect, the reactions of radicals generated in the plasma at the surfaces of the substrates, is important in determining the performance of a plasma process. However, such reactions are not well studied because there are few experimental techniques available that can directly probe them. Here, two-dimensional (2-D) imaging is a significant improvement to the IRIS (imaging of radicals interacting with surfaces) technique for measuring the reactivity of plasma-generated radicals at surfaces. Several interesting phenomena resulting from the effects of saturation of the optical transition and of molecular translation during the radiative lifetime of OH have now been observed directly.

  1. Adsorption of iso-/n-butane on an Anatase Thin Film: A Molecular...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    iso-n-butane on an Anatase Thin Film: A Molecular Beam Scattering and TDS Study. Adsorption of iso-n-butane on an Anatase Thin Film: A Molecular Beam Scattering and TDS Study....

  2. Polarization induced hole doping in graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Li, Shibin; Zhang, Ting; Wu, Jiang; Yang, Yajie; Wang, Zhiming; Wu, Zhiming; Chen, Zhi; Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)] [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2013-02-11T23:59:59.000Z

    Polarization induced hole doping on the order of {approx}10{sup 18} cm{sup -3} is achieved in linearly graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy. Graded Al{sub x}Ga{sub 1-x}N and conventional Al{sub 0.7}Ga{sub 0.3}N layers grown on AlN are beryllium (Be) doped via epitaxial growth. The hole concentration in graded Al{sub x}Ga{sub 1-x}N:Be (x = 0.7 {approx} 1) layers demonstrates that polarization generates hole charges from Be dopant. The Al{sub 0.7}Ga{sub 0.3}N layer is not conductive owing to the absence of carriers generated from the Be dopant without the inducement of polarization. Polarization doping provides an approach to high efficiency p-type doping in high Al composition AlGaN.

  3. Structure and magnetism in strained Ge{sub 1-x-y}Sn{sub x}Mn{sub y} films grown on Ge(001) by low temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Prestat, E. [INAC, SP2M, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Karlsruher Institut fuer Technologie (KIT), Laboratorium fuer Elektronenmikroskopie, D-76128 Karlsruhe (Germany); Barski, A.; Bellet-Amalric, E.; Morel, R.; Tainoff, D.; Jain, A.; Porret, C.; Bayle-Guillemaud, P.; Jamet, M. [INAC, SP2M, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Jacquot, J.-F. [INAC, SCIB, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France)

    2013-07-01T23:59:59.000Z

    In this letter, we study the structural and magnetic properties of Ge{sub 1-x-y}Sn{sub x}Mn{sub y} films grown on Ge(001) by low temperature molecular beam epitaxy using X-ray diffraction, high resolution transmission electron microscopy, and superconducting quantum interference device. Like in Mn doped Ge films, Mn atoms diffuse during the growth and aggregate into vertically aligned Mn-rich nanocolumns of a few nanometers in diameter. Transmission electron microscopy observations in plane view clearly indicate that the Sn incorporation is not uniform with concentration in Mn rich vertical nanocolumns lower than the detection limit of electron energy loss spectroscopy. The matrix exhibits a GeSn solid solution while there is a Sn-rich GeSn shell around GeMn nanocolumns. The magnetization in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} layers is higher than in Ge{sub 1-x}Mn{sub x} films. This magnetic moment enhancement in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} is probably related to the modification of the electronic structure of Mn atoms in the nanocolumns by the Sn-rich shell, which is formed around the nanocolumns.

  4. Strain states of AlN/GaN-stress mitigating layer and their effect on GaN buffer layer grown by ammonia molecular beam epitaxy on 100-mm Si(111)

    SciTech Connect (OSTI)

    Ravikiran, L.; Radhakrishnan, K.; Agrawal, M. [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)] [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Dharmarasu, N.; Munawar Basha, S. [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)] [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)

    2013-09-28T23:59:59.000Z

    The effect of strain states of AlN/GaN-stress mitigating layer (SML) on buried crack density and its subsequent influence on the residual stresses in GaN buffer layers grown using ammonia-molecular beam epitaxy on 100-mm Si(111) substrate has been investigated. Different stages involved in the formation of buried cracks, which are crack initialization, growth of relaxed AlN layer, and subsequent lateral over growth, are identified using in-situ curvature measurements. While the increase of GaN thickness in AlN/GaN-SML enhanced its compressive strain relaxation and resulted in reduced buried crack spacing, the variation of AlN thickness did not show any effect on the crack spacing. Moreover, the decrease in the crack spacing (or increase in the buried crack density) was found to reduce the residual compression in 1st and 2nd GaN layers of AlN/GaN-SML structure. The higher buried crack density relaxed the compressive strain in 1st GaN layer, which further reduced its ability to compensate the tensile stress generated during substrate cool down, and hence resulted in lower residual compressive stress in 2nd GaN layer.

  5. analytical mass spectrometry: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    analytical methods for solving a variety of molecular structure problems. Among high. Extension of mass spectrometry to the analysis of high molecular weight materials,...

  6. Beams 92: Proceedings. Volume 2, Ion beams, electron beams, diagnostics

    SciTech Connect (OSTI)

    Mosher, D.; Cooperstein, G. [eds.] [Naval Research Lab., Washington, DC (United States)] [eds.; Naval Research Lab., Washington, DC (United States)

    1993-12-31T23:59:59.000Z

    This report contains papers on the following topics. Ion beam papers; electron beam papers; and these papers have been indexed separately elsewhere.

  7. Structural and band alignment properties of Al{sub 2}O{sub 3} on epitaxial Ge grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Patra, P. K. [Department of Biomedical Engineering and Department of Mechanical Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States); Ma, A. W. K. [Department of Chemical and Biomolecular Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Aphale, A.; Macwan, I. [Department of Electrical and Computer Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States)

    2013-04-07T23:59:59.000Z

    Structural and band alignment properties of atomic layer Al{sub 2}O{sub 3} oxide film deposited on crystallographically oriented epitaxial Ge grown in-situ on (100), (110), and (111)A GaAs substrates using two separate molecular beam epitaxy chambers were investigated using cross-sectional transmission microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). High-resolution triple axis x-ray measurement demonstrated pseudomorphic and high-quality Ge epitaxial layer on crystallographically oriented GaAs substrates. The cross-sectional TEM exhibited a sharp interface between the Ge epilayer and each orientation of the GaAs substrate as well as the Al{sub 2}O{sub 3} film and the Ge epilayer. The extracted valence band offset, {Delta}E{sub v}, values of Al{sub 2}O{sub 3} relative to (100), (110), and (111) Ge orientations using XPS measurement were 3.17 eV, 3.34 eV, and 3.10 eV, respectively. Using XPS data, variations in {Delta}E{sub v} related to the crystallographic orientation were {Delta}E{sub V}(110)Ge>{Delta}E{sub V}(100)Ge{>=}{Delta}E{sub V}(111)Ge and the conduction band offset, {Delta}E{sub c}, related to the crystallographic orientation was {Delta}E{sub c}(111)Ge>{Delta}E{sub c}(110)Ge>{Delta}E{sub c}(100)Ge using the measured {Delta}E{sub v}, bandgap of Al{sub 2}O{sub 3} in each orientation, and well-known Ge bandgap of 0.67 eV. These band offset parameters are important for future application of Ge-based p- and n-channel metal-oxide field-effect transistor design.

  8. BEAMS Lab at MIT: Status report

    E-Print Network [OSTI]

    Liberman, Rosa G.

    The Biological Engineering Accelerator Mass Spectrometry (BEAMS) Lab at the Massachusetts Institute of Technology is a facility dedicated to incorporating AMS into life sciences research. As such, it is focused exclusively ...

  9. Opto-acoustic interactions in gravitational wave detectors: Comparing flat-top beams with Gaussian beams

    SciTech Connect (OSTI)

    Gras, S.; Blair, D. G.; Ju, L. [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2010-02-15T23:59:59.000Z

    To reduce the thermal noise in the future generation of gravitational wave detectors, flat-top beams have been proposed to replace conventional Gaussian beams, so as to obtain better averaging over the Brownian motion of the test masses. Here, we present a detailed investigation of the unwanted opto-acoustic interactions in such interferometers, which can lead to the phenomenon of parametric instability. Our results show that the increased overlap of the Mesa beams with the test masses leads to approximately 3 times as many unstable modes in comparison to a similar interferometer with Gaussian beams.

  10. CROSSED MOLECULAR BEAM STUDIES OF CHEMILUMINESCENT REACTIONS

    E-Print Network [OSTI]

    Kahler, Carol Cuzens

    2013-01-01T23:59:59.000Z

    inch thick quartz plate (ESCO Optics grade Sl-UV) pressedis varied. ird lens (G) (ESCO Optics, fused silica, 2 inch·I~UV, The fourth lens (H) (ESCO Optics, fused silica, grade

  11. CROSSED MOLECULAR BEAM STUDIES OF CHEMILUMINESCENT REACTIONS

    E-Print Network [OSTI]

    Kahler, Carol Cuzens

    2013-01-01T23:59:59.000Z

    dimensions Effusive - Quasi Effusive Source Diameter of Nozzle .015 inch (.038 em) Distance to collision zone (no skimmer or spacer) .

  12. Molecular Beam Epitaxy, Multi-source | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    to form reliable, low-resistance Ohmic contacts is of critical importance to the ongoing development of oxide electronics. Most metals... The Impacts of Cation Stoichiometry and...

  13. Dudley Herschbach: Chemical Reactions and Molecular Beams

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisitingContract ManagementDiscovering HowAna MooreDrought-induced treeDryDudley

  14. Yuan T. Lee and Molecular Beam Studies

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del SolStrengtheningWildfires may

  15. Accelerator beam profile analyzer

    DOE Patents [OSTI]

    Godel, Julius B. (Bayport, NY); Guillaume, Marcel (Grivegnee, BE); Lambrecht, Richard M. (East Quogue, NY); Withnell, Ronald (East Setauket, NY)

    1976-01-01T23:59:59.000Z

    A beam profile analyzer employing sector or quadrant plates each servo controlled to outline the edge of a beam.

  16. In situ secondary ion mass spectrometry analysis

    SciTech Connect (OSTI)

    Groenewold, G.S.; Applehans, A.D.; Ingram, J.C.; Delmore, J.E.; Dahl, D.A.

    1993-01-01T23:59:59.000Z

    The direct detection of tributyl phosphate (TBP) on rocks using molecular beam surface analysis [MBSA or in situ secondary ion mass spectrometry (SIMS)] is demonstrated. Quantities as low as 250 ng were detected on basalt and sandstone with little or no sample preparation. Detection of TBP on soil has proven to be more problematic and requires further study. Ethylenediaminetetraacetic acid (EDTA) is more difficult to detect because it is very reactive with surfaces of interest. Nevertheless, it is possible to detect EDTA if the acidity of the surface is controlled. The detection of EDTA-metal complexes is currently an open question, but evidence is presented for the detection of ions arising from a EDTA-lead complex. Carboxylic acids (i.e., citric, ascorbic, malic, succinic, malonic, and oxalic) give characteristic SIM spectra, but their detection on sample surfaces awaits evaluation.

  17. Molecular Chemistry of Organic Aerosols Through the Application...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Chemistry of Organic Aerosols Through the Application of High Resolution Mass Spectrometry. Molecular Chemistry of Organic Aerosols Through the Application of High Resolution Mass...

  18. Beam Status

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItem NotEnergy,ARMForms About Batteries Batteries An error occurred. TryRing CurrentBeam

  19. Beam History

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWP TWPAlumniComplex historian ...BESFor Users LiveBattling birdBeam

  20. Beam History

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWP TWPAlumniComplex historian ...BESFor Users LiveBattlingBeam

  1. Beam geometry selection using sequential beam addition

    SciTech Connect (OSTI)

    Popple, Richard A., E-mail: rpopple@uabmc.edu; Brezovich, Ivan A.; Fiveash, John B. [Department of Radiation Oncology, The University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, Alabama 35294 (United States)] [Department of Radiation Oncology, The University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, Alabama 35294 (United States)

    2014-05-15T23:59:59.000Z

    Purpose: The selection of optimal beam geometry has been of interest since the inception of conformal radiotherapy. The authors report on sequential beam addition, a simple beam geometry selection method, for intensity modulated radiation therapy. Methods: The sequential beam addition algorithm (SBA) requires definition of an objective function (score) and a set of candidate beam geometries (pool). In the first iteration, the optimal score is determined for each beam in the pool and the beam with the best score selected. In the next iteration, the optimal score is calculated for each beam remaining in the pool combined with the beam selected in the first iteration, and the best scoring beam is selected. The process is repeated until the desired number of beams is reached. The authors selected three treatment sites, breast, lung, and brain, and determined beam arrangements for up to 11 beams from a pool comprised of 25 equiangular transverse beams. For the brain, arrangements were additionally selected from a pool of 22 noncoplanar beams. Scores were determined for geometries comprised equiangular transverse beams (EQA), as well as two tangential beams for the breast case. Results: In all cases, SBA resulted in scores superior to EQA. The breast case had the strongest dependence on beam geometry, for which only the 7-beam EQA geometry had a score better than the two tangential beams, whereas all SBA geometries with more than two beams were superior. In the lung case, EQA and SBA scores monotonically improved with increasing number of beams; however, SBA required fewer beams to achieve scores equivalent to EQA. For the brain case, SBA with a coplanar pool was equivalent to EQA, while the noncoplanar pool resulted in slightly better scores; however, the dose-volume histograms demonstrated that the differences were not clinically significant. Conclusions: For situations in which beam geometry has a significant effect on the objective function, SBA can identify arrangements equivalent to equiangular geometries but using fewer beams. Furthermore, SBA provides the value of the objective function as the number of beams is increased, allowing the planner to select the minimal beam number that achieves the clinical goals. The method is simple to implement and could readily be incorporated into an existing optimization system.

  2. Molecular Characterization of Nitrogen Containing Organic Compounds...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Nitrogen Containing Organic Compounds in Biomass Burning Aerosols Using High Resolution Mass Molecular Characterization of Nitrogen Containing Organic Compounds in Biomass Burning...

  3. X-ray beam finder

    DOE Patents [OSTI]

    Gilbert, H.W.

    1983-06-16T23:59:59.000Z

    An X-ray beam finder for locating a focal spot of an X-ray tube includes a mass of X-ray opaque material having first and second axially-aligned, parallel-opposed faces connected by a plurality of substantially identical parallel holes perpendicular to the faces and a film holder for holding X-ray sensitive film tightly against one face while the other face is placed in contact with the window of an X-ray head.

  4. Vacuum-Ultraviolet Photoionization and Mass Spectrometric Characterization of Lignin Monomers Coniferyl and Sinapyl Alcohols

    SciTech Connect (OSTI)

    Takahashi, Lynelle K.; Zhou, Jia; Kostko, Oleg; Golan, Amir; Leone, Stephen R.; Ahmed, Musahid

    2011-02-09T23:59:59.000Z

    The fragmentation mechanisms of monolignols under various energetic processes are studied with jet-cooled thermal desorption molecular beam (TDMB) mass spectrometry (MS), 25 keV Bi3+ secondary ion MS (SIMS), synchrotron vacuum-ultraviolet secondary neutral MS (VUV-SNMS) and theoretical methods. Experimental and calculated appearance energies of fragments observed in TDMB MS indicate that the coniferyl alcohol photoionization mass spectra contain the molecular parent and several dissociative photoionization products. Similar results obtained for sinapyl alcohol are also discussed briefly. Ionization energies of 7.60 eV ? 0.05 eV for coniferyl alcohol and<7.4 eV for both sinapyl and dihydrosinapyl alcohols are determined. The positive ion SIMS spectrum of coniferyl alcohol shares few characteristic peaks (m/z = 137 and 151) with the TDMB mass spectra, shows extensive fragmentation, and does not exhibit clear molecular parent signals. VUV-SNMS spectra, on the other hand, are dominated by the parent ion and main fragments also present in the TDMB spectra. Molecular fragmentation in VUV-SNMS spectra can be reduced by increasing the extraction delay time. Some features resembling the SIMS spectra are also observed in the desorbed neutral products. The monolignol VUV-SNMS peaks shared with the TDMB mass spectra suggest that dissociative photoionization of ion-sputtered neutral molecules predominate in the VUV-SNMS mass spectra, despite the extra internal energy imparted in the initial ion impact. The potential applications of these results to imaging mass spectrometry of bio-molecules are discussed.

  5. Neutral beam dump with cathodic arc titanium gettering

    SciTech Connect (OSTI)

    Smirnov, A.; Korepanov, S. A.; Putvinski, S. [Tri Alpha Energy Inc., Rancho Santa Margarita, California 92688 (United States); Krivenko, A. S.; Murakhtin, S. V.; Savkin, V. Ya. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation)

    2011-03-15T23:59:59.000Z

    An incomplete neutral beam capture can degrade the plasma performance in neutral beam driven plasma machines. The beam dumps mitigating the shine-through beam recycling must entrap and retain large particle loads while maintaining the beam-exposed surfaces clean of the residual impurities. The cathodic arc gettering, which provides high evaporation rate coupled with a fast time response, is a powerful and versatile technique for depositing clean getter films in vacuum. A compact neutral beam dump utilizing the titanium arc gettering was developed for a field-reversed configuration plasma sustained by 1 MW, 20-40 keV neutral hydrogen beams. The titanium evaporator features a new improved design. The beam dump is capable of handling large pulsed gas loads, has a high sorption capacity, and is robust and reliable. With the beam particle flux density of 5 x 10{sup 17} H/(cm{sup 2}s) sustained for 3-10 ms, the beam recycling coefficient, defined as twice the ratio of the hydrogen molecular flux leaving the beam dump to the incident flux of high-energy neutral atoms, is {approx}0.7. The use of the beam dump allows us to significantly reduce the recycling of the shine-through neutral beam as well as to improve the vacuum conditions in the machine.

  6. High speed x-ray beam chopper

    DOE Patents [OSTI]

    McPherson, Armon (Oswego, IL); Mills, Dennis M. (Naperville, IL)

    2002-01-01T23:59:59.000Z

    A fast, economical, and compact x-ray beam chopper with a small mass and a small moment of inertia whose rotation can be synchronized and phase locked to an electronic signal from an x-ray source and be monitored by a light beam is disclosed. X-ray bursts shorter than 2.5 microseconds have been produced with a jitter time of less than 3 ns.

  7. Molecular phosphorus ion source for semiconductor technology

    SciTech Connect (OSTI)

    Gushenets V. I.; Hershcovitch A.; Bugaev, A.S.; Oks, E.M.; Kulevoy, T.V.

    2012-02-15T23:59:59.000Z

    This paper presents results on the generation of molecular phosphorus ion beams in a hot filament ion source. Solid red phosphorous is evaporated mainly as tetra-atomic molecules up to a temperature of 800 C. Thus, one of the main conditions for producing maximum P{sub 4}{sup +} fraction in the beam is to keep the temperature of the phosphorous oven, the steam line and the discharge chamber walls no greater than 800 C. The prior version of our ion source was equipped with a discharge chamber cooling system. The modified source ensured a P{sub 4}{sup +} ion beam current greater than 30% of the total beam current.

  8. Magnetismo Molecular (Molecular Magentism)

    SciTech Connect (OSTI)

    Reis, Mario S [Universidade Federal Fluminense, Brasil; Moreira Dos Santos, Antonio F [ORNL

    2010-07-01T23:59:59.000Z

    The new synthesis processes in chemistry open a new world of research, new and surprising materials never before found in nature can now be synthesized and, as a wonderful result, observed a series of physical phenomena never before imagined. Among these are many new materials the molecular magnets, the subject of this book and magnetic properties that are often reflections of the quantum behavior of these materials. Aside from the wonderful experience of exploring something new, the theoretical models that describe the behavior these magnetic materials are, in most cases, soluble analytically, which allows us to know in detail the physical mechanisms governing these materials. Still, the academic interest in parallel this subject, these materials have a number of properties that are promising to be used in technological devices, such as in computers quantum magnetic recording, magnetocaloric effect, spintronics and many other devices. This volume will journey through the world of molecular magnets, from the structural description of these materials to state of the art research.

  9. 2012 MOLECULAR AND IONIC CLUSTERS GORDON RESEARCH CONFERENCE, JANUARY 29 - FEBRUARY 3, 2012

    SciTech Connect (OSTI)

    Anne McCoy

    2012-02-03T23:59:59.000Z

    The Gordon Research Conference on 'Molecular and Ionic Clusters' focuses on clusters, which are the initial molecular species found in gases when condensation begins to occur. Condensation can take place solely from molecules interacting with each other, mostly at low temperatures, or when molecules condense around charged particles (electrons, protons, metal cations, molecular ions), producing ion molecule clusters. These clusters provide models for solvation, allow a pristine look at geometric as well as electronic structures of molecular complexes or matter in general, their interaction with radiation, their reactivity, their thermodynamic properties and, in particular, the related dynamics. This conference focuses on new ways to make clusters composed of different kinds of molecules, new experimental techniques to investigate the properties of the clusters and new theoretical methods with which to calculate the structures, dynamical motions and energetics of the clusters. Some of the main experimental methods employed include molecular beams, mass spectrometry, laser spectroscopy (from infrared to XUV; in the frequency as well as the time domain) and photoelectron spectroscopy. Techniques include laser absorption spectroscopy, laser induced fluorescence, resonance enhanced photoionization, mass-selected photodissociation, photofragment imaging, ZEKE photoelectron spectroscopy, etc. From the theoretical side, this conference highlights work on potential surfaces and measurable properties of the clusters. The close ties between experiment, theory and computation have been a hallmark of the Gordon Research Conference on Molecular and Ionic Clusters. In the 2012 meeting, we plan to have sessions that will focus on topics including: (1) The use of cluster studies to probe fundamental phenomena; (2) Finite size effects on structure and thermodynamics; (3) Intermolecular forces and cooperative effects; (4) Molecular clusters as models for solvation; and (5) Studies of clusters at XUV light sources.

  10. Beam position monitor

    DOE Patents [OSTI]

    Alkire, Randy W.; Rosenbaum, Gerold; Evans, Gwyndaf

    2003-07-22T23:59:59.000Z

    An apparatus for determining the position of an x-ray beam relative to a desired beam axis. Where the apparatus is positioned along the beam path so that a thin metal foil target intersects the x-ray beam generating fluorescent radiation. A PIN diode array is positioned so that a portion of the fluorescent radiation is intercepted by the array resulting in an a series of electrical signals from the PIN diodes making up the array. The signals are then analyzed and the position of the x-ray beam is determined relative to the desired beam path.

  11. Mapping Molecular Space with Mass Spectrometry /

    E-Print Network [OSTI]

    Nguyen, Don Duy

    2013-01-01T23:59:59.000Z

    L & Oliveira AC (2009) Microalgae as a raw material forP (2010) Biofuels from microalgae—A review of technologiesThe tide turns towards microalgae. Current research aims to

  12. Mapping Molecular Space with Mass Spectrometry /

    E-Print Network [OSTI]

    Nguyen, Don Duy

    2013-01-01T23:59:59.000Z

    L & Owende P (2010) Biofuels from microalgae—A review of2009) Microalgae as a raw material for biofuels production.microalgae. Current research aims to produce traditional biofuels

  13. Mapping Molecular Space with Mass Spectrometry /

    E-Print Network [OSTI]

    Nguyen, Don Duy

    2013-01-01T23:59:59.000Z

    microalgae. Current research aims to produce traditional biofuels from algae, but their potential to generate sustainable energy

  14. BEAMS3D Neutral Beam Injection Model

    SciTech Connect (OSTI)

    Lazerson, Samuel

    2014-04-14T23:59:59.000Z

    With the advent of applied 3D fi elds in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous velocity reduction, and pitch angle scattering are modeled with the ADAS atomic physics database [1]. Benchmark calculations are presented to validate the collisionless particle orbits, neutral beam injection model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields.

  15. Center for Beam Physics

    E-Print Network [OSTI]

    Chattopadhyay, S.

    2010-01-01T23:59:59.000Z

    interactions, ultra-high intensity lasers, 3D Laser Imagingconcepts, ultra-high intensity lasers, x-ray generation,interests: Ultra-high vacuum, particle beam and laser beam

  16. Bioheat and Mass Transfer Educational Initiatives for

    E-Print Network [OSTI]

    Texas at Austin, University of

    fluid and molecular transport Cornell Datta Ugrad heat and mass fundamentals Datta fluid mechBioheat and Mass Transfer Educational Initiatives for ASME K-17 Committee Ken Diller University of Texas #12;Outline of Presentation · Summary of submitted bioheat and mass transfer syllabi from K-17

  17. HERSCHEL MEASUREMENTS OF MOLECULAR OXYGEN IN ORION

    SciTech Connect (OSTI)

    Goldsmith, Paul F.; Chen, Jo-Hsin; Li Di [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Liseau, Rene; Black, John H. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Bell, Tom A. [Centro de Astrobiologia, CSIC-INTA, 28850 Madrid (Spain); Hollenbach, David [SETI Institute, Mountain View, CA 94043 (United States); Kaufman, Michael J. [Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States); Lis, Dariusz C. [California Institute of Technology, Cahill Center for Astronomy and Astrophysics 301-17, Pasadena, CA 91125 (United States); Melnick, Gary [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 66, Cambridge, MA 02138 (United States); Neufeld, David [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Pagani, Laurent; Encrenaz, Pierre [LERMA and UMR8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris (France); Snell, Ronald [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Benz, Arnold O.; Bruderer, Simon [Institute of Astronomy, ETH Zurich, Zurich (Switzerland); Bergin, Edwin [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Caselli, Paola [School of Physics and Astronomy, University of Leeds, Leeds (United Kingdom); Caux, Emmanuel [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Falgarone, Edith, E-mail: Paul.F.Goldsmith@jpl.nasa.gov [LRA/LERMA, CNRS, UMR8112, Observatoire de Paris and Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France)

    2011-08-20T23:59:59.000Z

    We report observations of three rotational transitions of molecular oxygen (O{sub 2}) in emission from the H{sub 2} Peak 1 position of vibrationally excited molecular hydrogen in Orion. We observed the 487 GHz, 774 GHz, and 1121 GHz lines using the Heterodyne Instrument for the Far Infrared on the Herschel Space Observatory, having velocities of 11 km s{sup -1} to 12 km s{sup -1} and widths of 3 km s{sup -1}. The beam-averaged column density is N(O{sub 2}) = 6.5 x 10{sup 16} cm{sup -2}, and assuming that the source has an equal beam-filling factor for all transitions (beam widths 44, 28, and 19''), the relative line intensities imply a kinetic temperature between 65 K and 120 K. The fractional abundance of O{sub 2} relative to H{sub 2} is (0.3-7.3) x 10{sup -6}. The unusual velocity suggests an association with a {approx}5'' diameter source, denoted Peak A, the Western Clump, or MF4. The mass of this source is {approx}10 M{sub sun} and the dust temperature is {>=}150 K. Our preferred explanation of the enhanced O{sub 2} abundance is that dust grains in this region are sufficiently warm (T {>=} 100 K) to desorb water ice and thus keep a significant fraction of elemental oxygen in the gas phase, with a significant fraction as O{sub 2}. For this small source, the line ratios require a temperature {>=}180 K. The inferred O{sub 2} column density {approx_equal}5 x 10{sup 18} cm{sup -2} can be produced in Peak A, having N(H{sub 2}) {approx_equal} 4 x 10{sup 24} cm{sup -2}. An alternative mechanism is a low-velocity (10-15 km s{sup -1}) C-shock, which can produce N(O{sub 2}) up to 10{sup 17} cm{sup -2}.

  18. Center for Beam Physics

    E-Print Network [OSTI]

    Chattopadhyay, S.

    2010-01-01T23:59:59.000Z

    FEL Collaboration: Photocathode/SCRF Collaboration: Two-BeamUniversity on Photocathode/ SCRF technology, LBNL-BNL on

  19. Beam Dynamics for ARIA

    E-Print Network [OSTI]

    Ekdahl, Carl

    2015-01-01T23:59:59.000Z

    Beam dynamics issues are assessed for a new linear induction electron accelerator being designed for flash radiography of large explosively driven hydrodynamic experiments. Special attention is paid to equilibrium beam transport, possible emittance growth, and beam stability. It is concluded that a radiographic quality beam will be produced possible if engineering standards and construction details are equivalent to those on the present radiography accelerators at Los Alamos.

  20. Development of the Holifield Radioactive Ion Beam Facility

    SciTech Connect (OSTI)

    Tatum, B.A.

    1997-08-01T23:59:59.000Z

    The Holifield Radioactive Ion Beam Facility (HRIBF) construction project has been completed and the first radioactive ion beam has been successfully accelerated. The project, which began in 1992, has involved numerous facility modifications. The Oak Ridge Isochronous Cyclotron has been converted from an energy booster for heavy ion beams to a light ion accelerator with internal ion source. A target-ion source and mass analysis system have been commissioned as key components of the facility`s radioactive ion beam injector to the 25MV tandem electrostatic accelerator. Beam transport lines have been completed, and new diagnostics for very low intensity beams have been developed. Work continues on a unified control system. Development of research quality radioactive beams for the nuclear structure and nuclear astrophysics communities continues. This paper details facility development to date.

  1. DEVELOPMENT OF EMITTANCE ANALYSIS SOFTWARE FOR ION BEAM CHARACTERIZATION

    SciTech Connect (OSTI)

    Padilla, M. J.; Liu, Y.

    2007-01-01T23:59:59.000Z

    Transverse beam emittance is a crucial property of charged particle beams that describes their angular and spatial spread. It is a fi gure of merit frequently used to determine the quality of ion beams, the compatibility of an ion beam with a given beam transport system, and the ability to suppress neighboring isotopes at on-line mass separator facilities. Generally a high quality beam is characterized by a small emittance. In order to determine and improve the quality of ion beams used at the Holifi eld Radioactive Ion beam Facility (HRIBF) for nuclear physics and nuclear astrophysics research, the emittances of the ion beams are measured at the off-line Ion Source Test Facilities. In this project, emittance analysis software was developed to perform various data processing tasks for noise reduction, to evaluate root-mean-square emittance, Twiss parameters, and area emittance of different beam fractions. The software also provides 2D and 3D graphical views of the emittance data, beam profi les, emittance contours, and RMS. Noise exclusion is essential for accurate determination of beam emittance values. A Self-Consistent, Unbiased Elliptical Exclusion (SCUBEEx) method is employed. Numerical data analysis techniques such as interpolation and nonlinear fi tting are also incorporated into the software. The software will provide a simplifi ed, fast tool for comprehensive emittance analysis. The main functions of the software package have been completed. In preliminary tests with experimental emittance data, the analysis results using the software were shown to be accurate.

  2. Temperature dependence of ion-beam mixing in crystalline and amorphous germanium isotope multilayer structures

    SciTech Connect (OSTI)

    Radek, M.; Bracht, H., E-mail: bracht@uni-muenster.de [Institute of Materials Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster (Germany); Posselt, M.; Liedke, B.; Schmidt, B. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01328 Dresden (Germany); Bougeard, D. [Institut für Experimentelle und Angewandte Physik, 93040 Regensburg (Germany)

    2014-01-14T23:59:59.000Z

    Self-atom mixing induced by 310 keV gallium (Ga) ion implantation in crystalline and preamorphized germanium (Ge) at temperatures between 164 K and 623 K and a dose of 1?×?10{sup 15}?cm{sup ?2} is investigated using isotopic multilayer structures of alternating {sup 70}Ge and {sup nat}Ge layers grown by molecular beam epitaxy. The distribution of the implanted Ga atoms and the ion-beam induced depth-dependent self-atom mixing was determined by means of secondary ion mass spectrometry. Three different temperature regimes of self-atom mixing, i.e., low-, intermediate-, and high-temperature regimes are observed. At temperatures up to 423 K, the mixing is independent of the initial structure, whereas at 523?K, the intermixing of the preamorphized Ge structure is about twice as high as that of crystalline Ge. At 623?K, the intermixing of the initially amorphous Ge structure is strongly reduced and approaches the mixing of the crystalline material. The temperature dependence of ion-beam mixing is described by competitive amorphization and recrystallization processes.

  3. BEAM DYNAMICS STUDIES FOR THE SPIRAL-2 PROJECT J-L. Biarrotte#

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    this construction phase: freezing of the low-energy beam transport lines of the injector, consolidation of the mass of freezing the layout of the injector low-energy beam transport lines, as is shown in Figure 1, superconducting linac, and high-energy beam transport lines (HEBTs). The injector includes two ECR sources (one

  4. {sup 18}Ne production for the Beta beams project

    SciTech Connect (OSTI)

    Hodák, Rastislav [Institute of Experimental and Applied Physics, CTU in Prague, Horská 3/22a, CZ-12800 Prague (Czech Republic); Mendonça, Tania M. [IFIMUP and IN - Institute of Nanosciences and Nanotechnologies, Rua do Campo Alegre 687, 4169-007 Porto, Portugal and CERN, CH-1211 Geneva 23 (Swaziland); Stora, Thierry [CERN, CH-1211 Geneva 23 (Switzerland)

    2013-12-30T23:59:59.000Z

    Intense relativistic (anti)neutrino beams are an unique tool required to study fundamental properties of neutrinos such as neutrino oscillation parameters, as well as their Majorana or Dirac nature, the lepton number conservation hypothesis and the absolute neutrino mass scale. Such beams originate from acceleration of ?-decaying radioactive ions (“Beta beams”). A molten fluoride salt target has been developed for the production of the required rates of low-Q baseline isotope {sup 18}Ne for the Beta beams project. The prototyped unit has been tested on-line at ISOLDE-CERN. In this contribution an overview of the prototyping and on-line tests is presented.

  5. Speckle Patterns with Atomic and Molecular de Broglie Waves

    SciTech Connect (OSTI)

    Patton, Forest S.; Deponte, Daniel P.; Kevan, Stephen D. [Department of Physics, University of Oregon, Eugene, Oregon 97403-1274 (United States); Elliott, Greg S. [Department of Physics, University of Puget Sound, Tacoma, Washington 98416 (United States)

    2006-07-07T23:59:59.000Z

    We have developed a nozzle source that delivers a continuous beam of atomic helium or molecular hydrogen having a high degree of transverse coherence and with adequate optical brightness to enable new kinds of experiments. Using this source we have measured single slit diffraction patterns and the first ever speckle-diffraction patterns using atomic and molecular de Broglie waves. Our results suggest fruitful application of coherent matter beams in dynamic scattering and diffractive imaging at short wavelength and with extreme surface sensitivity.

  6. LBNL-46223, CBP Note 350 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS IN THE LHC

    E-Print Network [OSTI]

    Furman, Miguel

    LBNL-46223, CBP Note 350 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS IN THE LHC M. A. Furman, W. C. Turner, Center for Beam Physics, LBNL, Berkeley, CA 94720, USA Abstract We present beam-beam simulation of simulations: (a) to as- sess undesirable effects from LBNL's luminosity monitor- ing scheme for the LHC [2

  7. LBNL-45363, CBP Note 333 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS

    E-Print Network [OSTI]

    Furman, Miguel

    LBNL-45363, CBP Note 333 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS Miguel A. Furman, Center for Beam Physics, LBNL, Berkeley, CA 94720 Abstract We present beam-beam simulation results from a strong undesirable effects from LBNL's sweeping lumi- nosity monitoring scheme for the LHC [1], and (b) to assess

  8. Piezoelectric energy harvester having planform-tapered interdigitated beams

    DOE Patents [OSTI]

    Kellogg, Rick A. (Tijeras, NM); Sumali, Hartono (Albuquerque, NM)

    2011-05-24T23:59:59.000Z

    Embodiments of energy harvesters have a plurality of piezoelectric planform-tapered, interdigitated cantilevered beams anchored to a common frame. The plurality of beams can be arranged as two or more sets of beams with each set sharing a common sense mass affixed to their free ends. Each set thus defined being capable of motion independent of any other set of beams. Each beam can comprise a unimorph or bimorph piezoelectric configuration bonded to a conductive or non-conductive supporting layer and provided with electrical contacts to the active piezoelectric elements for collecting strain induced charge (i.e. energy). The beams are planform tapered along the entirety or a portion of their length thereby increasing the effective stress level and power output of each piezoelectric element, and are interdigitated by sets to increase the power output per unit volume of a harvester thus produced.

  9. Methods of Beam Cooling

    E-Print Network [OSTI]

    Sessler, A. M.

    2008-01-01T23:59:59.000Z

    of Optical Stochastic Cooling", presented at PAC, (1995).1991). Hangst, J. , "Laser Cooling of a Stored Ion Beam - ATheorem and Phase Space Cooling", Proceedings of the

  10. Broad beam ion implanter

    DOE Patents [OSTI]

    Leung, Ka-Ngo (Hercules, CA)

    1996-01-01T23:59:59.000Z

    An ion implantation device for creating a large diameter, homogeneous, ion beam is described, as well as a method for creating same, wherein the device is characterized by extraction of a diverging ion beam and its conversion by ion beam optics to an essentially parallel ion beam. The device comprises a plasma or ion source, an anode and exit aperture, an extraction electrode, a divergence-limiting electrode and an acceleration electrode, as well as the means for connecting a voltage supply to the electrodes.

  11. Courses on Beam Physics

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    is an incomplete listing of course available for beam physics. United States Particle Accelerator School The US Particle Accelerator School provides educational programs in the...

  12. Method and apparatus for measuring the momentum, energy, power, and power density profile of intense particle beams

    DOE Patents [OSTI]

    Gammel, George M. (Merrick, NY); Kugel, Henry W. (Somerset, NJ)

    1992-10-06T23:59:59.000Z

    A method and apparatus for determining the power, momentum, energy, and power density profile of high momentum mass flow. Small probe projectiles of appropriate size, shape and composition are propelled through an intense particle beam at equal intervals along an axis perpendicular to the beam direction. Probe projectiles are deflected by collisions with beam particles. The net beam-induced deflection of each projectile is measured after it passes through the intense particle beam into an array of suitable detectors.

  13. Laser Desorption Single-Photon Ionization of Asphaltenes: Mass Range, Compound Sensitivity, and Matrix Effects

    E-Print Network [OSTI]

    Zare, Richard N.

    Laser Desorption Single-Photon Ionization of Asphaltenes: Mass Range, Compound Sensitivity and flow assurance. Laser desorption single-photon ionization mass spectrometry (LDSPI-MS) has emerged, such as their molecular mass distribution and dominant molecular architecture.1,6-11 Laser mass spectrometry, including

  14. Production of a beam of highly vibrationally excited CO using perturbations

    E-Print Network [OSTI]

    Bartels, Nils

    An intense molecular beam of CO (X[superscript 1]?[superscript +]) in high vibrational states (v = 17, 18) was produced by a new approach that we call PUMP – PUMP – PERTURB and DUMP. The basic idea is to access high ...

  15. Neutrino Masses

    E-Print Network [OSTI]

    Christian Weinheimer; Kai Zuber

    2013-09-04T23:59:59.000Z

    The various experiments on neutrino oscillation evidenced that neutrinos have indeed non-zero masses but cannot tell us the absolute neutrino mass scale. This scale of neutrino masses is very important for understanding the evolution and the structure formation of the universe as well as for nuclear and particle physics beyond the present Standard Model. Complementary to deducing constraints on the sum of all neutrino masses from cosmological observations two different methods to determine the neutrino mass scale in the laboratory are pursued: the search for neutrinoless double $\\beta$-decay and the direct neutrino mass search by investigating single $\\beta$-decays or electron captures. The former method is not only sensitive to neutrino masses but also probes the Majorana character of neutrinos and thus lepton number violation with high sensitivity. Currently quite a few experiments with different techniques are being constructed, commissioned or are even running, which aim for a sensitivity on the neutrino mass of {\\cal O}(100) meV. The principle methods and these experiments will be discussed in this short review.

  16. Laser beam generating apparatus

    DOE Patents [OSTI]

    Warner, B.E.; Duncan, D.B.

    1994-02-15T23:59:59.000Z

    Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus is described. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 7 figures.

  17. Laser beam generating apparatus

    DOE Patents [OSTI]

    Warner, B.E.; Duncan, D.B.

    1993-12-28T23:59:59.000Z

    Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 11 figures.

  18. B13+: Photodriven Molecular Wankel Engine

    SciTech Connect (OSTI)

    Zhang, Jin; Sergeeva, Alina P.; Sparta, Manuel; Alexandrova, Anastassia N.

    2012-07-09T23:59:59.000Z

    Synthetic molecular motors that are capable of delivering controlled movement upon energy input are one of the key building blocks in nanomachinery. The major energy sources of molecular motors are from chemical reactions, photon beams, or electric current, which are converted into mechanical forces through the excitation of the electronic states of the molecule. The energy scale of the electronic excitation is normally two orders of magnitude larger than the molecular vibrational frequencies. To reduce the heat dissipation and increase the energy utilization efficiency, a motor running purely on the electronic ground-state (GS) potential energy surfaces is highly desirable.

  19. First Beam to FACET

    SciTech Connect (OSTI)

    Erickson, R.; Clarke, C.; Colocho, W.; Decker, F.-J.; Hogan, M.; Kalsi, S.; Lipkowitz, N.; Nelson, J.; Phinney, N.; Schuh, P.; Sheppard, J.; Smith, H.; Smith, T.; Stanek, M.; Turner, J.; Warren, J.; Weathersby, S.; Wienands, U.; Wittmer, W.; Woodley, M.; Yocky, G.; /SLAC

    2011-12-13T23:59:59.000Z

    The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new Facility for Advanced Accelerator Experimental Tests (FACET) while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). On June 23, 2011, the first electron beam was transported through this new facility. Commissioning of FACET is in progress. On June 23, 2011, an electron beam was successfully transported through the new FACET system to a dump in Sector 20 in the linac tunnel. This was achieved while the last third of the linac, operating from the same control room, but with a separate injector system, was providing an electron beam to the Linac Coherent Light Source (LCLS), demonstrating that concurrent operation of the two facilities is practical. With the initial checkout of the new transport line essentially complete, attention is now turning toward compressing the electron bunches longitudinally and focusing them transversely to support a variety of accelerator science experiments.

  20. Growth and characterization of dilute nitride GaN{sub x}P{sub 1?x} nanowires and GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowires on Si (111) by gas source molecular beam epitaxy

    SciTech Connect (OSTI)

    Sukrittanon, S. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92037 (United States); Dobrovolsky, A.; Chen, W. M.; Buyanova, I. A. [Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping (Sweden); Kang, Won-Mo; Kim, Bong-Joong [Department of Materials Science and Engineering, Gwangju institute of Science and Technology (GIST), Gwangju 500-712 (Korea, Republic of); Jang, Ja-Soon [Department of Electronic Engineering, LED-IT Fusion Technology Research Center, Yeungnam University, Daegu 712-749 (Korea, Republic of); Tu, C. W. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92037 (United States)

    2014-08-18T23:59:59.000Z

    We have demonstrated self-catalyzed GaN{sub x}P{sub 1?x} and GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowire growth by gas-source molecular beam epitaxy. The growth window for GaN{sub x}P{sub 1?x} nanowires was observed to be comparable to that of GaP nanowires (?585?°C to ?615?°C). Transmission electron microscopy showed a mixture of cubic zincblende phase and hexagonal wurtzite phase along the [111] growth direction in GaN{sub x}P{sub 1?x} nanowires. A temperature-dependent photoluminescence (PL) study performed on GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowires exhibited an S-shape dependence of the PL peaks. This suggests that at low temperature, the emission stems from N-related localized states below the conduction band edge in the shell, while at high temperature, the emission stems from band-to-band transition in the shell as well as recombination in the GaN{sub x}P{sub 1?x} core.

  1. Molecular beam epitaxial growth of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators on GaAs (111) substrates: a potential route to fabricate topological insulator p-n junction

    SciTech Connect (OSTI)

    Zeng, Zhaoquan; Morgan, Timothy A.; Li, Chen; Hirono, Yusuke; Hu, Xian; Hawkridge, Michael E.; Benamara, Mourad; Salamo, Gregory J. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States)] [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Fan, Dongsheng; Yu, Shuiqing [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Zhao, Yanfei [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China)] [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); Lee, Joon Sue [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)] [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Jian [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China) [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Zhiming M. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

    2013-07-15T23:59:59.000Z

    High quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} films. Hall and magnetoresistance measurements indicate that p type Sb{sub 2}Te{sub 3} and n type Bi{sub 2}Te{sub 3} topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

  2. Impacts of anisotropic lattice relaxation on crystal mosaicity and luminescence spectra of m-plane Al{sub x}Ga{sub 1-x}N films grown on m-plane freestanding GaN substrates by NH{sub 3} source molecular beam epitaxy

    SciTech Connect (OSTI)

    Hoshi, T.; Hazu, K.; Ohshita, K.; Kagaya, M.; Onuma, T.; Chichibu, S. F. [CANTech, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Fujito, K. [Optoelectronics Laboratory, Mitsubishi Chemical Corporation, 1000 Higashi-Mamiana, Ushiku 300-1295 (Japan); Namita, H. [Mitsubishi Chemical Group Science and Technology Research Center, Inc., 8-3-1 Chuo, Ami, Inashiki 300-0332 (Japan)

    2009-02-16T23:59:59.000Z

    In-plane anisotropic lattice relaxation was correlated with the crystal mosaicity and luminescence spectra for m-plane Al{sub x}Ga{sub 1-x}N films grown on a freestanding GaN substrate by NH{sub 3}-source molecular beam epitaxy. The homoepitaxial GaN film exhibited A- and B-excitonic emissions at 8 K, which obeyed the polarization selection rules. For Al{sub x}Ga{sub 1-x}N overlayers, the m-plane tilt mosaic along c-axis was the same as the substrate as far as coherent growth was maintained (x{<=}0.25). However, it became more severe than along the a-axis for lattice-relaxed films (x{>=}0.52). The results are explained in terms of anisotropic lattice and thermal mismatches between the film and the substrate. Nonetheless, all the Al{sub x}Ga{sub 1-x}N films exhibited a near-band-edge emission peak and considerably weak deep emission at room temperature.

  3. STOCHASTIC COOLING OF BUNCHED BEAMS

    E-Print Network [OSTI]

    Bisognano, J.J.

    2010-01-01T23:59:59.000Z

    March 11-13, 1981 STOCHASTIC COOLING OF BUNCHED BEAMS J.J.W-7406-BW-48 STOCHASTIC COOLING OF BUNCHED BEAMS* J.J.longitudinal stochastic cooling of bunched particle beams.

  4. The Growth of GaN on Si by the Beam Flux Modulation

    SciTech Connect (OSTI)

    Roh, C. H.; Ha, M. W.; Song, H. J.; Choi, H. G.; Lee, J. H.; Ra, Y. W.; Hahn, C. K. [Compound Semiconductor Devices Research Center, Energy-Display R and D Division, Korea Electronics Technology Institute, Seongnam (Korea, Republic of)

    2011-12-23T23:59:59.000Z

    AlGaN/GaN HEMT structure was grown on Si (111) substrate by plasma-assisted molecular beam epitaxy (PA-MBE) using a beam flux modulation methods. In this result, it was verified that the propagation of treading dislocation (TD) due to N-rich GaN layer was effectively suppressed.

  5. Negligible Sample Heating from Synchrotron Infrared Beam Michael C. Martina

    E-Print Network [OSTI]

    Negligible Sample Heating from Synchrotron Infrared Beam Michael C. Martina , Nelly M. Tsvetkovab of Molecular and Cellular Biology, University of California at Davis, USA Infrared (IR) spectroscopy is one can now obtain diffraction-limited spot sizes with high signal intensity in an infrared microscope

  6. Simulations of beam-beam and beam-wire interactions in RHIC

    SciTech Connect (OSTI)

    Kim, Hyung J.; Sen, Tanaji; /Fermilab; Abreu, Natalia P.; Fischer, Wolfram; /Brookhaven

    2009-02-01T23:59:59.000Z

    The beam-beam interaction is one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and strong localized long-range beam-beam effects are experimentally investigated in the RHIC collider. Tune shift, beam transfer function, and beam loss rate are measured in dedicated experiments. In this paper, they report on simulations to study the effect of beam-wire interactions based on diffusive apertures, beam loss rates, and beam transfer function using a parallelized weak-strong beam simulation code (BBSIMC). The simulation results are compared with measurements performed in RHIC during 2007 and 2008.

  7. Ion beam lithography system

    DOE Patents [OSTI]

    Leung, Ka-Ngo

    2005-08-02T23:59:59.000Z

    A maskless plasma-formed ion beam lithography tool provides for patterning of sub-50 nm features on large area flat or curved substrate surfaces. The system is very compact and does not require an accelerator column and electrostatic beam scanning components. The patterns are formed by switching beamlets on or off from a two electrode blanking system with the substrate being scanned mechanically in one dimension. This arrangement can provide a maskless nano-beam lithography tool for economic and high throughput processing.

  8. Inverse time-of-flight spectrometer for beam plasma research

    SciTech Connect (OSTI)

    Yushkov, Yu. G., E-mail: yuyushkov@gmail.com; Zolotukhin, D. B.; Tyunkov, A. V. [Tomsk State University of Control Systems and Radioelectronics, 40 Lenin Ave., Tomsk 634050 (Russian Federation); Oks, E. M. [Tomsk State University of Control Systems and Radioelectronics, 40 Lenin Ave., Tomsk 634050 (Russian Federation); Institute of High Current Electronics SB RAS, 2/3, Akademichesky Ave., Tomsk 634055 (Russian Federation); Savkin, K. P. [Institute of High Current Electronics SB RAS, 2/3, Akademichesky Ave., Tomsk 634055 (Russian Federation)

    2014-08-15T23:59:59.000Z

    The paper describes the design and principle of operation of an inverse time-of-flight spectrometer for research in the plasma produced by an electron beam in the forevacuum pressure range (5–20 Pa). In the spectrometer, the deflecting plates as well as the drift tube and the primary ion beam measuring system are at high potential with respect to ground. This provides the possibility to measure the mass-charge constitution of the plasma created by a continuous electron beam with a current of up to 300 mA and electron energy of up to 20 keV at forevacuum pressures in the chamber placed at ground potential. Research results on the mass-charge state of the beam plasma are presented and analyzed.

  9. Sandia Energy - Molecular Geochemistry

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    molecular spectroscopy, and molecular simulation to complex multicomponent and multiphase systems; particular emphasis on the use of molecular simulation and various...

  10. Molecular phosphorus ion source for semiconductor technology

    SciTech Connect (OSTI)

    Gushenets, V. I.; Bugaev, A. S.; Oks, E. M. [Institute of High Current Electronics SB RAS, Tomsk 634055 (Russian Federation); Hershcovitch, A. [Brookhaven National Laboratory, Upton, New York 11973 (United States); Kulevoy, T. V. [Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation)

    2012-02-15T23:59:59.000Z

    This paper presents results on the generation of molecular phosphorus ion beams in a hot filament ion source. Solid red phosphorous is evaporated mainly as tetra-atomic molecules up to a temperature of 800 deg. C. Thus, one of the main conditions for producing maximum P{sub 4}{sup +} fraction in the beam is to keep the temperature of the phosphorous oven, the steam line and the discharge chamber walls no greater than 800 deg. C. The prior version of our ion source was equipped with a discharge chamber cooling system. The modified source ensured a P{sub 4}{sup +} ion beam current greater than 30% of the total beam current.

  11. Coherent beam-beam mode in the LHC

    E-Print Network [OSTI]

    Buffat, X; Giachino, R; Herr, W; Papotti, G; Pieloni, T; White, S

    2014-01-01T23:59:59.000Z

    Observations of single bunch beam-beam coherent modes during dedicated experiments in the LHC are presented. Their role in standard operation for physics is discussed and, in particular, candidates of beam-beam coherent mode driven unstable by the machine impedance are presented.

  12. Focused ion beam system

    DOE Patents [OSTI]

    Leung, K.; Gough, R.A.; Ji, Q.; Lee, Y.Y.

    1999-08-31T23:59:59.000Z

    A focused ion beam (FIB) system produces a final beam spot size down to 0.1 {mu}m or less and an ion beam output current on the order of microamps. The FIB system increases ion source brightness by properly configuring the first (plasma) and second (extraction) electrodes. The first electrode is configured to have a high aperture diameter to electrode thickness aspect ratio. Additional accelerator and focusing electrodes are used to produce the final beam. As few as five electrodes can be used, providing a very compact FIB system with a length down to only 20 mm. Multibeamlet arrangements with a single ion source can be produced to increase throughput. The FIB system can be used for nanolithography and doping applications for fabrication of semiconductor devices with minimum feature sizes of 0.1 m or less. 13 figs.

  13. Final focus test beam

    SciTech Connect (OSTI)

    Not Available

    1991-03-01T23:59:59.000Z

    This report discusses the following: the Final Focus Test Beam Project; optical design; magnets; instrumentation; magnetic measurement and BPM calibration; mechanical alignment and stabilization; vacuum system; power supplies; control system; radiation shielding and personnel protection; infrastructure; and administration.

  14. Pulsed ion beam source

    DOE Patents [OSTI]

    Greenly, John B. (Lansing, NY)

    1997-01-01T23:59:59.000Z

    An improved pulsed ion beam source having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center.

  15. LHC beam behaviour

    E-Print Network [OSTI]

    Herr, W

    2010-01-01T23:59:59.000Z

    An attempt is made to extract information on the LHC beam behaviour and dynamics from the observations made during the first runs in 2009. Although no systematic studies have been made, some basic properties can be established and in particular the observations in the presence of two beams and in collision are studied. They are analyzed in view of the foreseen runs at higher energy and possible improvements are proposed.

  16. Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development

    SciTech Connect (OSTI)

    Gilpatrick, John D. [Los Alamos National Laboratory; Batygin, Yuri K. [Los Alamos National Laboratory; Gonzales, Fermin [Los Alamos National Laboratory; Gruchalla, Michael E. [Los Alamos National Laboratory; Kutac, Vincent G. [Los Alamos National Laboratory; Martinez, Derwin [Los Alamos National Laboratory; Sedillo, James Daniel [Los Alamos National Laboratory; Pillai, Chandra [Los Alamos National Laboratory; Rodriguez Esparza, Sergio [Los Alamos National Laboratory; Smith, Brian G. [Los Alamos National Laboratory

    2012-05-15T23:59:59.000Z

    The Los Alamos Neutron Science Center (LANSCE) is replacing Wire Scanner (WS) beam profile measurement systems. Three beam development tests have taken place to test the new wire scanners under beam conditions. These beam development tests have integrated the WS actuator, cable plant, electronics processors and associated software and have used H{sup -} beams of different beam energy and current conditions. In addition, the WS measurement-system beam tests verified actuator control systems for minimum profile bin repeatability and speed, checked for actuator backlash and positional stability, tested the replacement of simple broadband potentiometers with narrow band resolvers, and tested resolver use with National Instruments Compact Reconfigurable Input and Output (cRIO) Virtual Instrumentation. These beam tests also have verified how trans-impedance amplifiers react with various types of beam line background noise and how noise currents were not generated. This paper will describe these beam development tests and show some resulting data.

  17. Photon beam position monitor

    DOE Patents [OSTI]

    Kuzay, T.M.; Shu, D.

    1995-02-07T23:59:59.000Z

    A photon beam position monitor is disclosed for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade ''shadowing''. Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation. 18 figs.

  18. Single element laser beam shaper

    DOE Patents [OSTI]

    Zhang, Shukui (Yorktown, VA); Michelle D. Shinn (Newport News, VA)

    2005-09-13T23:59:59.000Z

    A single lens laser beam shaper for converting laser beams from any spatial profile to a flat-top or uniform spatial profile. The laser beam shaper includes a lens having two aspheric surfaces. The beam shaper significantly simplifies the overall structure in comparison with conventional 2-element systems and therefore provides great ease in alignment and reduction of cost.

  19. Beam Dynamics Challenges for the ILC

    SciTech Connect (OSTI)

    Kubo, Kiyoshi; /KEK, Tsukuba; Seryi, Andrei; /SLAC; Walker, Nicholas; /DESY; Wolski, Andy; /Cockcroft Inst. Accel. Sci. Tech.

    2008-02-13T23:59:59.000Z

    The International Linear Collider (ILC) is a proposal for 500 GeV center-of-mass electron-positron collider, with a possible upgrade to {approx}1 TeV center-of-mass. At the heart of the ILC are the two {approx}12 km 1.3 GHz superconducting RF (SCRF) linacs which will accelerate the electron and positron beams to an initial maximum energy of 250 GeV each. The Global Design Effort (GDE)--responsible for the world-wide coordination of this uniquely international project--published the ILC Reference Design Report in August of 2007 [1]. The ILC outlined in the RDR design stands on a legacy of over fifteen-years of R&D. The GDE is currently beginning the next step in this ambitious project, namely an Engineering Design phase, which will culminate with the publication of an Engineering Design Report (EDR) in mid-2010. Throughout the history of linear collider development, beam dynamics has played an essential role. In particular, the need for complex computer simulations to predict the performance of the machine has always been crucial, not least because the parameters of the ILC represent in general a large extrapolation from where current machines operate today; many of the critical beam-dynamics features planned for the ILC can ultimately only be truly tested once the ILC has been constructed. It is for this reason that beam dynamics activities will continue to be crucial during the Engineering Design phase, as the available computer power and software techniques allow ever-more complex and realistic models of the machine to be developed. Complementary to the computer simulation efforts are the need for well-designed experiments at beam-test facilities, which--while not necessarily producing a direct demonstration of the ILC-like parameters for the reasons mentioned above--can provide important input and benchmarking for the computer models.

  20. Ultrahigh vacuum and low-temperature cleaning of oxide surfaces using a low-concentration ozone beam

    SciTech Connect (OSTI)

    Pratt, A. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Graziosi, P.; Bergenti, I.; Dediu, A. [CNR – ISMN, Consiglio Nazionale delle Ricerche – Istituto per lo Studio dei Materiali Nanostrutturati, v. Gobetti 101, 40129 Bologna (Italy); Prezioso, M. [Department of Electrical and Computer Engineering, Harold Frank Hall, University of California, Santa Barbara, California 93106 (United States); Yamauchi, Y., E-mail: yamauchi.yasushi@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-07-15T23:59:59.000Z

    We present a novel method of delivering a low-concentration (<15%) ozone beam to an ultra-high vacuum environment for the purpose of cleaning and dosing experimental samples through oxidation processing. The system described is safe, low-cost, and practical and overcomes the limitations of ozone transport in the molecular flow environment of high or ultrahigh vacuum whilst circumventing the use of pure ozone gas which is potentially highly explosive. The effectiveness of this method in removing surface contamination is demonstrated through comparison of high-temperature annealing of a simple oxide (MgO) in ozone and oxygen environments as monitored using quadrupole mass spectroscopy and Auger electron spectroscopy. Additionally, we demonstrate the potential of ozone for obtaining clean complex oxide surfaces without the need for high-temperature annealing which may significantly alter surface structure.

  1. Mass Chain Evaluation for A=95

    SciTech Connect (OSTI)

    Basu, S.K.; Sonzogni, A.; Basu, Swapan Kr.; Mukherjee, Gopal; Sonzogni, A. A.

    2011-08-01T23:59:59.000Z

    A full evaluation of the mass chain A = 95 has been done in the ENSDF format taking into account all the available data until June 2009. Excited states populated by in-beam nuclear reactions and by radioactive decay have been considered. The 'evp' editor, developed at the NNDC, has been used for the evaluation. This mass chain was last evaluated in 1993. Many new and improved data were reported since then. A total of 13 nuclei have been evaluated.

  2. Measurement of the W Boson Mass

    E-Print Network [OSTI]

    Baringer, Philip S.; Bean, Alice; Clutter, Justace Randall; Moulik, Tania; Wilson, Graham Wallace; Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.

    2009-10-01T23:59:59.000Z

    30Tata Institute of Fundamental Research, Mumbai, India 31University College Dublin, Dublin, Ireland 32Korea Detector Laboratory, Korea University, Seoul, Korea 33SungKyunKwan University, Suwon, Korea 34CINVESTAV, Mexico City, Mexico 35FOM... in the plane perpendicular to the beam direction: the trans- verse mass mT , the electron transverse momentum peT , and the neutrino transverse momentum p#1;T . The transverse mass is defined as m...

  3. ICFA Beam Dynamics Newsletter

    SciTech Connect (OSTI)

    Ben-Zvi I.; Kuczewski A.; Altinbas, Z.; Beavis, D.; Belomestnykh,; Dai, J. et al

    2012-07-01T23:59:59.000Z

    The Collider-Accelerator Department at Brookhaven National Laboratory is building a high-brightness 500 mA capable Energy Recovery Linac (ERL) as one of its main R&D thrusts towards eRHIC, the polarized electron - hadron collider as an upgrade of the operating RHIC facility. The ERL is in final assembly stages, with injection commisioning starting in October 2012. The objective of this ERL is to serve as a platform for R&D into high current ERL, in particular issues of halo generation and control, Higher-Order Mode (HOM) issues, coherent emissions for the beam and high-brightness, high-power beam generation and preservation. The R&D ERL features a superconducting laser-photocathode RF gun with a high quantum efficiency photoccathode served with a load-lock cathode delivery system, a highly damped 5-cell accelerating cavity, a highly flexible single-pass loop and a comprehensive system of beam instrumentation. In this ICFA Beam Dynamics Newsletter article we will describe the ERL in a degree of detail that is not usually found in regular publications. We will discuss the various systems of the ERL, following the electrons from the photocathode to the beam dump, cover the control system, machine protection etc and summarize with the status of the ERL systems.

  4. Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test

    SciTech Connect (OSTI)

    Jana, M.R.; Bross, A.; Chung, M.; Greer, S.; Johnstone, C.; Kobilarcik, T.; Koizumi, G.; Leonova, M.; Moretti, A.; Popovic, M.; Schwartz, T.; /Fermilab /IIT, Chicago /PDT, Torino

    2012-05-15T23:59:59.000Z

    Recent High Pressure RF (HPRF) cavity experiment at MuCool Test Area (MTA) has used 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces the electrons. These electrons consume RF power inside the cavity. Number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is {approx} 1200. The measurement of beam position and profile are necessary. MTA is flammable gas (Hydrogen) hazard zone so we have developed a passive beam diagnostic instrument using Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. Neutral density filter was used to avoid saturation of CCD camera. Image data is filtered and fitted with Gaussian function to compute the beam size. The beam profile obtained from scintillation screen shall be compared with multi-wire beam profile.

  5. Beam Profile Monitor With Accurate Horizontal And Vertical Beam Profiles

    DOE Patents [OSTI]

    Havener, Charles C [Knoxville, TN; Al-Rejoub, Riad [Oak Ridge, TN

    2005-12-26T23:59:59.000Z

    A widely used scanner device that rotates a single helically shaped wire probe in and out of a particle beam at different beamline positions to give a pair of mutually perpendicular beam profiles is modified by the addition of a second wire probe. As a result, a pair of mutually perpendicular beam profiles is obtained at a first beamline position, and a second pair of mutually perpendicular beam profiles is obtained at a second beamline position. The simple modification not only provides more accurate beam profiles, but also provides a measurement of the beam divergence and quality in a single compact device.

  6. Grazing incidence beam expander

    SciTech Connect (OSTI)

    Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

    1985-01-01T23:59:59.000Z

    A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

  7. Beam characteristics of energy-matched flattening filter free beams

    SciTech Connect (OSTI)

    Paynter, D.; Weston, S. J.; Cosgrove, V. P. [St James Institute of Oncology The Leeds Teaching Hospitals NHS Trust, Medical Physics, Leeds LS9 7TF (United Kingdom)] [St James Institute of Oncology The Leeds Teaching Hospitals NHS Trust, Medical Physics, Leeds LS9 7TF (United Kingdom); Evans, J. A. [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds (United Kingdom)] [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds (United Kingdom); Thwaites, D. I. [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds, United Kingdom and Institute of Medical Physics, School of Physics, University of Sydney (Australia)] [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds, United Kingdom and Institute of Medical Physics, School of Physics, University of Sydney (Australia)

    2014-05-15T23:59:59.000Z

    Purpose: Flattening filter free (FFF) linear accelerators can increase treatment efficiency and plan quality. There are multiple methods of defining a FFF beam. The Elekta control system supports tuning of the delivered FFF beam energy to enable matching of the percentage depth-dose (PDD) of the flattened beam at 10 cm depth. This is compared to FFF beams where the linac control parameters are identical to those for the flattened beam. All beams were delivered on an Elekta Synergy accelerator with an Agility multi-leaf collimator installed and compared to the standard, flattened beam. The aim of this study is to compare “matched” FFF beams to both “unmatched” FFF beams and flattened beams to determine the benefits of matching beams. Methods: For the three modes of operation 6 MV flattened, 6 MV matched FFF, 6 MV unmatched FFF, 10 MV flattened, 10 MV matched FFF, and 10 MV unmatched FFF beam profiles were obtained using a plotting tank and were measured in steps of 0.1 mm in the penumbral region. Beam penumbra was defined as the distance between the 80% and 20% of the normalized dose when the inflection points of the unflattened and flattened profiles were normalized with the central axis dose of the flattened field set as 100%. PDD data was obtained at field sizes ranging from 3 cm × 3 cm to 40?cm × 40 cm. Radiation protection measurements were additionally performed to determine the head leakage and environmental monitoring through the maze and primary barriers. Results: No significant change is made to the beam penumbra for FFF beams with and without PDD matching, the maximum change in penumbra for a 10 cm × 10 cm field was within the experimental error of the study. The changes in the profile shape with increasing field size are most significant for the matched FFF beam, and both FFF beams showed less profile shape variation with increasing depth when compared to flattened beams, due to consistency in beam energy spectra across the radiation field. The PDDs of the FFF beams showed less variation with field size, the d{sub max} value was deeper for the matched FFF beam than the FFF beam and deeper than the flattened beam for field sizes greater than 5 cm × 5 cm. The head leakage when using the machine in FFF mode is less than half that for a flattened beam, but comparable for both FFF modes. The radiation protection dose-rate measurements show an increase of instantaneous dose-rates when operating the machines in FFF mode but that increase is less than the ratio of MU/min produced by the machine. Conclusions: The matching of a FFF beam to a flattened beam at a depth of 10 cm in water by increasing the FFF beam energy does not reduce any of the reported benefits of FFF beams. Conversely, there are a number of potential benefits resulting from matching the FFF beam; the depth of maximum dose is deeper, the out of field dose is potentially reduced, and the beam quality and penetration more closely resembles the flattened beams currently used in clinical practice, making dose distributions in water more alike. Highlighted in this work is the fact that some conventional specifications and methods for measurement of beam parameters such as penumbra are not relevant and further work is required to address this situation with respect to “matched” FFF beams and to determine methods of measurement that are not reliant on an associated flattened beam.

  8. Attenuation of Beaming Oscillations Near Neutron Stars

    E-Print Network [OSTI]

    M. Coleman Miller

    2000-07-17T23:59:59.000Z

    Observations with RXTE have revealed kilohertz quasi-periodic brightness oscillations (QPOs) from nearly twenty different neutron-star low-mass X-ray binaries (LMXBs). These frequencies often appear as a pair of kilohertz QPOs in a given power density spectrum. In many models the higher-frequency of these QPOs is a beaming oscillation at the frequency of a nearly circular orbit at some radius near the neutron star. In such models it is expected that there will also be beaming oscillations at the stellar spin frequency and at overtones of the orbital frequency, but no strong QPOs have been detected at these frequencies. We therefore examine the processes that can attenuate beaming oscillations near neutron stars, and in doing so extend the work on this subject that was initiated by the discovery of lower-frequency QPOs from LMXBs. Among our main results are (1)in a spherical scattering cloud, all overtones of rotationally modulated beaming oscillations are attenuated strongly, not just the even harmonics, and (2)it is possible to have a relatively high-amplitude modulation near the star at, e.g., the stellar spin frequency, even if no peak at that frequency is detectable in a power density spectrum taken at infinity. We discuss the application of these results to modeling of kilohertz QPOs.

  9. Molecular Foundry

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOne of

  10. Molecular Foundry

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOne

  11. Molecular Foundry

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOneThe

  12. Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments

    E-Print Network [OSTI]

    G. Vidali; V. Pirronello; L. Li; J. Roser; G. Manico; R. Mehl; A. Lederhendler; H. B. Perets; J. R. Brucato; O. Biham

    2008-11-21T23:59:59.000Z

    The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions present in interstellar clouds.

  13. Observation of Coherent Beam-beam Effects in the LHC

    E-Print Network [OSTI]

    Buffat, X; Giachino, R; Herr, W; Papotti, G; Pieloni, T; Calaga, R; White, S M

    2011-01-01T23:59:59.000Z

    Early collisions in the LHC with a very limited number of bunches with high intensities indicated the presence of coherent beam-beam driven oscillations. Here we discuss the experimental results and compare with the expectations.

  14. Electron beam dynamics for the ISIS bremsstrahlung beam generation system

    E-Print Network [OSTI]

    Block, Robert E. (Robert Edward)

    2011-01-01T23:59:59.000Z

    An electron beam transport system was designed for use in the Bremsstrahlung Beam Generation System of the Integrated Stand-off Inspection System (ISIS). The purpose of this electron transport system was to provide for ...

  15. Heavy Oil Upgrading from Electron Beam (E-Beam) Irradiation 

    E-Print Network [OSTI]

    Yang, Daegil

    2011-02-22T23:59:59.000Z

    hydrocarbons. Second, we studied the energy transfer mechanism of E-Beam upgrading to optimize the process. Third, we conducted a preliminary economic analysis based on energy consumption and compared the economics of E-Beam upgrading with conventional...

  16. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    Detector chamber. (Q) Main chamber ion pump- (S) Rotation (from ion pumps. (A) Buffer chamber ion pump feedthrough. (B) Quadrupole chamber ion pump feedthrough. (C) Coolant

  17. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    temperature cycling and since the chambers are difficult to access and view in the -Un­ completed condition, the construction and welding

  18. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    on 0.063" dowel pins press fit into the ends of the slideinto the center was press fit into the dividing wall as theID, 0.156" thick) are press fit into the end of the drive

  19. Reactions of carbon atoms in pulsed molecular beams

    SciTech Connect (OSTI)

    Reisler, H. [Univ. of Southern California, Los Angeles (United States)

    1993-12-01T23:59:59.000Z

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  20. Pulsed ion beam source

    DOE Patents [OSTI]

    Greenly, J.B.

    1997-08-12T23:59:59.000Z

    An improved pulsed ion beam source is disclosed having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center. 12 figs.

  1. Colliding beams of light

    E-Print Network [OSTI]

    B. V. Ivanov

    2002-12-28T23:59:59.000Z

    The stationary gravitational field of two identical counter-moving beams of pure radiation is found in full generality. The solution depends on an arbitrary function and a parameter which sets the scale of the energy density. Some of its properties are studied. Previous particular solutions are derived as subcases.

  2. Ion-beam technologies

    SciTech Connect (OSTI)

    Fenske, G.R. [Argonne National Lab., IL (United States)

    1993-01-01T23:59:59.000Z

    This compilation of figures and diagrams reviews processes for depositing diamond/diamond-like carbon films. Processes addressed are chemical vapor deposition (HFCVD, PACVD, etc.), plasma vapor deposition (plasma sputtering, ion beam sputtering, evaporation, etc.), low-energy ion implantation, and hybrid processes (biased sputtering, IBAD, biased HFCVD, etc.). The tribological performance of coatings produced by different means is discussed.

  3. Future Directions of Structural Mass Spectrometry using Hydroxyl Radical Footprinting

    SciTech Connect (OSTI)

    J Kiselar; M Chance

    2011-12-31T23:59:59.000Z

    Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposure of proteins to a 'white' X-ray beam for milliseconds provides sufficient oxidative modification to surface amino acid side chains, which can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular subdomains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review, we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that the selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal-to-noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis-driven structural mass spectrometry experiments.

  4. The Cooling of Particle Beams

    E-Print Network [OSTI]

    Sessler, Andrew M.

    2008-01-01T23:59:59.000Z

    67, 15. Hangst, J "Laser Cooling of a Stored Ion Beam - ATheorem an.d Phase Space Cooling", Proceedings of theWorkshop on Beam Cooling and Related Topics, Montreaux, CERN

  5. Hadron beams session-summary

    SciTech Connect (OSTI)

    Terwilliger, K.M. (University of Michigan, Ann Arbor, MI 48109-1120, USA (US))

    1989-05-05T23:59:59.000Z

    The status of presently operating polarized beams at Fermilab, the AGS, and KEK is discussed. Other schemes such as Siberian Snakes and self-polarization of a beam in situ are briefly analyzed.(AIP)

  6. Laser beam pulse formatting method

    DOE Patents [OSTI]

    Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

    1994-08-09T23:59:59.000Z

    A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

  7. Cryogenic Beam Loss Monitors for the Superconducting Magnets of the LHC

    E-Print Network [OSTI]

    Bartosik, MR; Sapinski, M; Kurfuerst, C; Griesmayer, E; Eremin, V; Verbitskaya, E

    2014-01-01T23:59:59.000Z

    The Beam Loss Monitor detectors close to the interaction points of the Large Hadron Collider are currently located outside the cryostat, far from the superconducting coils of the magnets. In addition to their sensitivity to lost beam particles, they also detect particles coming from the experimental collisions, which do not contribute significantly to the heat deposition in the superconducting coils. In the future, with beams of higher energy and brightness resulting in higher luminosity, distinguishing between these interaction products and dangerous quench-provoking beam losses from the primary proton beams will be challenging. The system can be optimised by locating beam loss monitors as close as possible to the superconducting coils, inside the cold mass in a superfluid helium environment, at 1.9 K. The dose then measured by such Cryogenic Beam Loss Monitors would more precisely correspond to the real dose deposited in the coil. The candidates under investigation for such detectors are based on p+-n-n+ si...

  8. HEAVY GOLD CLUSTER BEAMS production and identi cation

    E-Print Network [OSTI]

    Boyer, Edmond

    . This method is based on the acceleration of the clusters to high energy (MeV) and on the measurement, after to select heavy Aun cluster beams for applications at low energy (keV) in mass spectrometry. 1. Introduction, with a multianode detector 7], the number of constituents coming out of the foil. High energy clusters, accelerated

  9. Molecular Gas in Galaxies

    E-Print Network [OSTI]

    F. Combes

    2000-07-21T23:59:59.000Z

    Knowledge of the molecular component of the ISM is fundamental to understand star formation. The H2 component appears to dominate the gas mass in the inner parts of galaxies, while the HI component dominates in the outer parts. Observation of the CO and other lines in normal and starburst galaxies have questioned the CO-to-H2 conversion factor, and detection of CO in dwarfs have shown how sensitive the conversion f actor is to metallicity. Our knowledge has made great progress in recent years, because of sensitivity and spatial resolution improvements. Large-scale CO maps of nearby galaxies are now available, which extend our knowledge on global properties, radial gradients, and spiral structure of the molecular ISM. Millimetric interferometers reveal high velocity gradients in galaxy nuclei, and formation of embedded structures, like bars within bars. Galaxy interactions are very effective to enhance gas concentrations and trigger starbursts. Nuclear disks or rings are frequently observed, that concentrate the star formation activity. Since the density of starbursting galaxies is strongly increasing with redshift, the CO lines and the mm dust emission are a privileged tool to follow evolution of galaxies and observe the ISM dynamics at high redshift: they could give an answer about the debated question of the star-formation history, since many massive remote starbursts could be dust-enshrouded.

  10. Secondary ion mass spectrometry (SIMS)! Seminar 4 (UN)!

    E-Print Network [OSTI]

    Â?umer, Slobodan

    for compositional analysis of solid surfaces and thin films. When a surface is bombarded by high energy beam! ! Secondary ion mass spectrometry (SIMS)! Seminar 4 (UN)! ! ! ! ! ! ! ! ! Author: Nina Kovacic! ___________________________________________________________________________! ABSTRACT! ! Secondary ion mass spectrometry (SIMS) is an analytical experimental technique, used

  11. Nanoscale molecularly imprinted polymers and method thereof

    DOE Patents [OSTI]

    Hart, Bradley R. (Brentwood, CA); Talley, Chad E. (Brentwood, CA)

    2008-06-10T23:59:59.000Z

    Nanoscale molecularly imprinted polymers (MIP) having polymer features wherein the size, shape and position are predetermined can be fabricated using an xy piezo stage mounted on an inverted microscope and a laser. Using an AMF controller, a solution containing polymer precursors and a photo initiator are positioned on the xy piezo and hit with a laser beam. The thickness of the polymeric features can be varied from a few nanometers to over a micron.

  12. Molecular Characterization of S- and N-containing Organic Constituents in Ambient Aerosols by negative ion mode High-Resolution Nanospray Desorption Electrospray Ionization Mass Spectrometry: CalNex 2010 field study

    SciTech Connect (OSTI)

    O'Brien, Rachel E.; Laskin, Alexander; Laskin, Julia; Rubitschun, Caitlin L.; Surratt, Jason D.; Goldstein, Allen H.

    2014-11-27T23:59:59.000Z

    Samples of ambient aerosols from the 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study were analyzed using Nanospray Desorption Electrospray Ionization High Resolution Mass Spectrometry (nano-DESI/MS). Four samples per day were collected in Bakersfield, CA on June 20-24 with a collection time of 6 hours per sample. Four characteristic groups of organic constituents were identified in the samples: compounds containing carbon, hydrogen, and oxygen only (CHO), sulfur- (CHOS), nitrogen-(CHON), and both nitrogen- and sulfur-containing organics (CHONS). Within the groups, organonitrates, organosulfates, and nitroxy organosulfates were assigned based on accurate mass measurements and elemental ratio comparisons. Changes in the chemical composition of the aerosol samples were observed throughout the day. The number of observed CHO compounds increased in the afternoon samples, suggesting regional photochemical processing as a source. The average number of CHOS compounds had the smallest changes throughout the day, consistent with a more broadly distributed source. Both of the nitrogen-containing groups (CHON and CHONS) had greater numbers of compounds in the night and morning samples, indicating that nitrate radical chemistry was likely a source for those compounds. Most of the compounds were found in submicron particles. The size distribution of CHON compounds was bimodal. We conclude that the majority of the compounds observed were secondary in nature with both biogenic and anthropogenic sources.

  13. Beam-helicity and beam-charge asymmetries associated with deeply virtual Compton scattering on the unpolarised proton

    E-Print Network [OSTI]

    Airapetian, A; Akopov, Z; Aschenauer, E C; Augustyniak, W; Avakian, R; Avetissian, A; Avetisyan, E; Blok, H P; Borissov, A; Bowles, J; Bryzgalov, V; Burns, J; Capiluppi, M; Capitani, G P; Cisbani, E; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; Deconinck, W; De Leo, R; De Nardo, L; De Sanctis, E; Diefenthaler, M; Di Nezza, P; Düren, M; Ehrenfried, M; Elbakian, G; Ellinghaus, F; Fantoni, A; Felawka, L; Frullani, S; Gabbert, D; Gapienko, G; Gapienko, V; Garibaldi, F; Gavrilov, G; Giordano, F; Gliske, S; Golembiovskaya, M; Hadjidakis, C; Hartig, M; Hasch, D; Hoek, M; Holler, Y; Imazu, Y; Jackson, H E; Jo, H S; Kaiser, R; Karyan, G; Keri, T; Kinney, E; Kisselev, A; Kobayashi, N; Korotkov, V; Kozlov, V; Kravchenko, P; Krivokhijine, V G; Lagamba, L; Lapikás, L; Lehmann, I; Lenisa, P; Lorenzon, W; Ma, B -Q; Mahon, D; Makins, N C R; Manaenkov, S I; Manfré, L; Mao, Y; Marianski, B; de la Ossa, A Martinez; Marukyan, H; Miller, C A; Miyachi, Y; Movsisyan, A; Muccifora, V; Murray, M; Mussgiller, A; Nappi, E; Naryshkin, Y; Nass, A; Nowak, W -D; Pappalardo, L L; Perez-Benito, R; Petrosyan, A; Raithel, M; Reimer, P E; Reolon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanftl, F; Schäfer, A; Schnell, G; Schüler, K P; Seitz, B; Shibata, T -A; Shutov, V; Stancari, M; Statera, M; Steffens, E; Steijger, J J M; Stewart, J; Taroian, S; Terkulov, A; Truty, R; Trzcinski, A; Tytgat, M; Van Haarlem, Y; Van Hulse, C; Veretennikov, D; Vikhrov, V; Vilardi, I; Wang, S; Yaschenko, S; Ye, Z; Yen, S; Yu, W; Zagrebelnyy, V; Zeiler, D; Zihlmann, B; Zupranski, P

    2012-01-01T23:59:59.000Z

    Beam-helicity and beam-charge asymmetries in the hard exclusive leptoproduction of real photons from an unpolarised hydrogen target by a 27.6 GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a missing-mass event selection technique. The asymmetry amplitudes extracted from this data set are more precise than those extracted from the earlier data set of 1996-2005 previously analysed in the same manner by HERMES. The results from the two data sets are compatible with each other. Results from these combined data sets are extracted and constitute the most precise asymmetry amplitude measurements made in the HERMES kinematic region using a missing-mass event selection technique.

  14. Beam-helicity and beam-charge asymmetries associated with deeply virtual Compton scattering on the unpolarised proton

    E-Print Network [OSTI]

    The HERMES Collaboration; A. Airapetian; N. Akopov; Z. Akopov; E. C. Aschenauer; W. Augustyniak; R. Avakian; A. Avetissian; E. Avetisyan; H. P. Blok; A. Borissov; J. Bowles; V. Bryzgalov; J. Burns; M. Capiluppi; G. P. Capitani; E. Cisbani; G. Ciullo; M. Contalbrigo; P. F. Dalpiaz; W. Deconinck; R. De Leo; L. De Nardo; E. De Sanctis; M. Diefenthaler; P. Di Nezza; M. Düren; M. Ehrenfried; G. Elbakian; F. Ellinghaus; A. Fantoni; L. Felawka; S. Frullani; D. Gabbert; G. Gapienko; V. Gapienko; F. Garibaldi; G. Gavrilov; F. Giordano; S. Gliske; M. Golembiovskaya; C. Hadjidakis; M. Hartig; D. Hasch; M. Hoek; Y. Holler; Y. Imazu; H. E. Jackson; H. S. Jo; R. Kaiser; G. Karyan; T. Keri; E. Kinney; A. Kisselev; N. Kobayashi; V. Korotkov; V. Kozlov; P. Kravchenko; V. G. Krivokhijine; L. Lagamba; L. Lapikás; I. Lehmann; P. Lenisa; W. Lorenzon; B. -Q. Ma; D. Mahon; N. C. R. Makins; S. I. Manaenkov; L. Manfré; Y. Mao; B. Marianski; A. Martinez de la Ossa; H. Marukyan; C. A. Miller; Y. Miyachi; A. Movsisyan; V. Muccifora; M. Murray; A. Mussgiller; E. Nappi; Y. Naryshkin; A. Nass; W. -D. Nowak; L. L. Pappalardo; R. Perez-Benito; A. Petrosyan; M. Raithel; P. E. Reimer; A. R. Reolon; C. Riedl; K. Rith; G. Rosner; A. Rostomyan; J. Rubin; D. Ryckbosch; Y. Salomatin; F. Sanftl; A. Schäfer; G. Schnell; K. P. Schüler; B. Seitz; T. -A. Shibata; V. Shutov; M. Stancari; M. Statera; E. Steffens; J. J. M. Steijger; J. Stewart; S. Taroian; A. Terkulov; R. Truty; A. Trzcinski; M. Tytgat; Y. Van Haarlem; C. Van Hulse; D. Veretennikov; V. Vikhrov; I. Vilardi; S. Wang; S. Yaschenko; Z. Ye; S. Yen; W. Yu; V. Zagrebelnyy; D. Zeiler; B. Zihlmann; P. Zupranski

    2012-06-29T23:59:59.000Z

    Beam-helicity and beam-charge asymmetries in the hard exclusive leptoproduction of real photons from an unpolarised hydrogen target by a 27.6 GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a missing-mass event selection technique. The asymmetry amplitudes extracted from this data set are more precise than those extracted from the earlier data set of 1996-2005 previously analysed in the same manner by HERMES. The results from the two data sets are compatible with each other. Results from these combined data sets are extracted and constitute the most precise asymmetry amplitude measurements made in the HERMES kinematic region using a missing-mass event selection technique.

  15. Recent advances of strong-strong beam-beam simulation

    SciTech Connect (OSTI)

    Qiang, Ji; Furman, Miguel A.; Ryne, Robert D.; Fischer, Wolfram; Ohmi,Kazuhito

    2004-09-15T23:59:59.000Z

    In this paper, we report on recent advances in strong-strong beam-beam simulation. Numerical methods used in the calculation of the beam-beam forces are reviewed. A new computational method to solve the Poisson equation on nonuniform grid is presented. This method reduces the computational cost by a half compared with the standard FFT based method on uniform grid. It is also more accurate than the standard method for a colliding beam with low transverse aspect ratio. In applications, we present the study of coherent modes with multi-bunch, multi-collision beam-beam interactions at RHIC. We also present the strong-strong simulation of the luminosity evolution at KEKB with and without finite crossing angle.

  16. Measurement of the Higgs Boson Mass with a Linear e+e- Collider

    E-Print Network [OSTI]

    P. Garcia-Abia; W. Lohmann; A. Raspereza

    2005-05-30T23:59:59.000Z

    The potential of a linear e+e- collider operated at a centre-of-mass energy of 350 GeV is studied for the measurement of the Higgs boson mass. An integrated luminosity of 500 fb-1 is assumed. For Higgs boson masses of 120, 150 and 180 GeV the uncertainty on the Higgs boson mass measurement is estimated to be 40, 65 and 70 MeV, respectively. The effects of beam related systematics, namely a bias in the beam energy measurement, the beam energy spread and the luminosity spectrum due to beamstrahlung, on the precision of the Higgs boson mass measurement are investigated. In order to keep the systematic uncertainty on the Higgs boson mass well below the level of the statistical error, the beam energy measurement must be controlled with a relative precision better than 10-4.

  17. Results of long-range beam-beam studies - scaling with beam separation and intensity

    E-Print Network [OSTI]

    Assmann, R; Buffat, X; Calaga, R; Giachino, R; Herr, W; Metral, E; Papotti, G; Pieloni, T; Roy, G; Trad, G; Kaltchev, D; CERN. Geneva. ATS Department

    2012-01-01T23:59:59.000Z

    We studied possible limitations due to the long-range beam-beam effects in the LHC. With a large number of bunches and collisions in all interaction points, we have reduced the crossing angles to enhance long-range beam-beam effects to evaluate their influence on dynamic aperture and losses. Different beta* and intensities have been used in two dedicated experiments and allow the test of the expected scaling laws.

  18. Ion beam generating apparatus

    DOE Patents [OSTI]

    Brown, Ian G. (1088 Woodside Rd., Berkeley, CA 94708); Galvin, James (2 Commodore #276, Emeryville, CA 94608)

    1987-01-01T23:59:59.000Z

    An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam.

  19. Ion beam generating apparatus

    DOE Patents [OSTI]

    Brown, I.G.; Galvin, J.

    1987-12-22T23:59:59.000Z

    An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam. 10 figs.

  20. Stationary nonlinear Airy beams

    SciTech Connect (OSTI)

    Lotti, A. [Dipartimento di Fisica e Matematica, Universita del'Insubria, Via Valleggio 11, I-22100 Como (Italy); Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Faccio, D. [Dipartimento di Fisica e Matematica, Universita del'Insubria, Via Valleggio 11, I-22100 Como (Italy); School of Engineering and Physical Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Couairon, A. [Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Papazoglou, D. G. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Materials Science and Technology Department, University of Crete, GR-71003 Heraklion (Greece); Panagiotopoulos, P.; Tzortzakis, S. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Abdollahpour, D. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Physics Department, University of Crete, GR-71003 Heraklion (Greece)

    2011-08-15T23:59:59.000Z

    We demonstrate the existence of an additional class of stationary accelerating Airy wave forms that exist in the presence of third-order (Kerr) nonlinearity and nonlinear losses. Numerical simulations and experiments, in agreement with the analytical model, highlight how these stationary solutions sustain the nonlinear evolution of Airy beams. The generic nature of the Airy solution allows extension of these results to other settings, and a variety of applications are suggested.

  1. Axion beams at HERA?

    E-Print Network [OSTI]

    K. Piotrzkowski

    2007-01-09T23:59:59.000Z

    If the recently observed anomaly in the PVLAS experiment is due to the axion, then the powerful beams of synchrotron photons, propagating through high magnetic field of the HERA beamline, become strong axion sources. This gives a unique opportunity of detection of the axion-photon interactions by installing a small detector in the HERA tunnel, and to corroborate the axion hypothesis within a few days of running.

  2. Physics with Rare Isotope Beams

    SciTech Connect (OSTI)

    Segel, Ralph E. [Northwestern University] [Northwestern University

    2013-11-08T23:59:59.000Z

    Using stable and radioactive beams provided by ATLAS nuclear reactions of special interest in astrophysics have been studied with emphasis on breakout from the hot CNO cycle to the rp-process. The masses of nuclear fragments provided by a strong fission source have been measured in order to help trace the path of the r process. 8Li ions produced by the d(7Li,8Li)n reaction have been trapped and the electrons and alphas emitted in the ensuing beta-decay measured. The neutrino directions were therefore determined, which leads to a measurement of the electron-neutrino correlation. The energies and kinematics are such that a sensitive search for any tensor admixture could be performed and an upper limit of 0.6% was placed on any such admixture. Earlier work on the electromagnetic form factors of the proton was extended. Graduate students were active participants in all of these eperiments, which formed the basis for six PhD theses.

  3. Understanding the Poor Resolution from Test Beam RunUnderstanding the Poor Resolution from Test Beam Run 2004 Straw Test beam results2004 Straw Test beam results

    E-Print Network [OSTI]

    1 Understanding the Poor Resolution from Test Beam RunUnderstanding the Poor Resolution from Test Beam Run aah #12;2 2004 Straw Test beam results2004 Straw Test beam results ! Doc # 3308 v#3 by A. Ledovskoy " Using Data from 2004 Test Beam " Used "triplet" method for beam nominally perpendicular to Straw

  4. Fast beam studies of free radical photodissociation

    SciTech Connect (OSTI)

    Neumark, D.M. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01T23:59:59.000Z

    The authors have developed a novel technique for studying the photodissociation spectroscopy and dynamics of free radicals. In these experiments, radicals are generated by laser photodetachment of a fast (6-8 keV) mass-selected negative ion beam. The resulting radicals are photodissociated with a second laser, and the photofragments are collected and detected with high efficiency using a microchannel plate detector. The overall process is: ABC{sup -} {yields} ABC + e{sup -} {yields} A + BC, AB + C. Two types of fragment detection schemes are used. To map out the photodissociation cross-section of the radical, the photodissociation laser is scanned and the total photofragment yield is measured as a function of wavelength. In other experiments, the photodissociation frequency is fixed and the photofragment masses, kinetic energy release, and scattering angle is determined for each photodissociation event.

  5. Mapping the core mass function to the initial mass function

    E-Print Network [OSTI]

    Guszejnov, David

    2014-01-01T23:59:59.000Z

    It has been shown that fragmentation within self-gravitating, turbulent molecular clouds ("turbulent fragmentation") can naturally explain the observed properties of protostellar cores, including the core mass function (CMF). Here, we extend recently-developed analytic models for turbulent fragmentation to follow the time-dependent hierarchical fragmentation of self-gravitating cores, until they reach effectively infinite density (and form stars). We show that turbulent fragmentation robustly predicts two key features of the IMF. First, a high-mass power-law scaling very close to the Salpeter slope, which is a generic consequence of the scale-free nature of turbulence and self-gravity. We predict the IMF slope (-2.3) is slightly steeper then the CMF slope (-2.1), owing to the slower collapse and easier fragmentation of large cores. Second, a turnover mass, which is set by a combination of the CMF turnover mass (a couple solar masses, determined by the `sonic scale' of galactic turbulence, and so weakly depend...

  6. Ion Mobility Mass Spectrometry Direct Isotope Abundance Analysis

    SciTech Connect (OSTI)

    Manuel J. Manard, Stephan Weeks, Kevin Kyle

    2010-05-27T23:59:59.000Z

    The nuclear forensics community is currently engaged in the analysis of illicit nuclear or radioactive material for the purposes of non-proliferations and attribution. One technique commonly employed for gathering nuclear forensics information is isotope analysis. At present, the state-of-the-art methodology for obtaining isotopic distributions is thermal ionization mass spectrometry (TIMS). Although TIMS is highly accurate at determining isotope distributions, the technique requires an elementally pure sample to perform the measurement. The required radiochemical separations give rise to sample preparation times that can be in excess of one to two weeks. Clearly, the nuclear forensics community is in need of instrumentation and methods that can expedite their decision making process in the event of a radiological release or nuclear detonation. Accordingly, we are developing instrumentation that couples a high resolution IM drift cell to the front end of a MS. The IM cell provides a means of separating ions based upon their collision cross-section and mass-to-charge ratio (m/z). Two analytes with the same m/z, but with different collision cross-sections (shapes) would exit the cell at different times, essentially enabling the cell to function in a similar manner to a gas chromatography (GC) column. Thus, molecular and atomic isobaric interferences can be effectively removed from the ion beam. The mobility selected chemical species could then be introduced to a MS for high-resolution mass analysis to generate isotopic distributions of the target analytes. The outcome would be an IM/MS system capable of accurately measuring isotopic distributions while concurrently eliminating isobaric interferences and laboratory radiochemical sample preparation. The overall objective of this project is developing instrumentation and methods to produce near real-time isotope distributions with a modular mass spectrometric system that performs the required gas-phase chemistry and separations. The system couples a high-resolution ion mobility (IM) drift cell to the front end of a mass spectrometer (MS) allowing for chemical separation prior to isotope distribution analyses. This will yield isotope ratio measurement capabilities with minimal sample preparation.

  7. Conceptual design of elliptical cavities for intensity and position sensitive beam measurements in storage rings

    E-Print Network [OSTI]

    Sanjari, M S; Hülsmann, P; Litvinov, Yu A; Nolden, F; Piotrowski, J; Steck, M; Stöhlker, Th

    2015-01-01T23:59:59.000Z

    Position sensitive beam monitors are indispensable for the beam diagnostics in storage rings. Apart from their applications in the measurements of beam parameters, they can be used in non-destructive in-ring decay studies of radioactive ion beams as well as enhancing precision in the isochronous mass measurement technique. In this work, we introduce a novel approach based on cavities with elliptical cross-section, in order to compensate for existing limitations in ion storage rings. The design is aimed primarily for future heavy ion storage rings of the FAIR project. The conceptual design is discussed together with simulation results.

  8. Plasma-beam traps and radiofrequency quadrupole beam coolers

    SciTech Connect (OSTI)

    Maggiore, M., E-mail: mario.maggiore@lnl.infn.it; Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S. [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy)] [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy); Caruso, A.; Longhitano, A. [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy)] [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy); Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M. [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)] [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)

    2014-02-15T23:59:59.000Z

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

  9. Multifragmentation at the balance energy of mass asymmetric colliding nuclei

    E-Print Network [OSTI]

    Supriya Goyal

    2011-06-20T23:59:59.000Z

    Using the quantum molecular dynamics model, we study the role of mass asymmetry of colliding nuclei on the fragmentation at the balance energy and on its mass dependence. The study is done by keeping the total mass of the system fixed as 40, 80, 160, and 240 and by varying the mass asymmetry of the ($\\eta$ = $\\frac{A_{T}-A_{P}}{A_{T}+A_{P}}$; where $A_{T}$ and $A_{P}$ are the masses of the target and projectile, respectively) reaction from 0.1 to 0.7. Our results clearly indicate a sizeable effect of the mass asymmetry on the multiplicity of various fragments. The mass asymmetry dependence of various fragments is found to increase with increase in total system mass (except for heavy mass fragments). Similar to symmetric reactions, a power law system mass dependence of various fragment multiplicities is also found to exit for large asymmetries.

  10. Observations of beam-beam effects at the LHC

    E-Print Network [OSTI]

    Papotti, G; Herr, W; Giachino, R; Pieloni, T

    2014-01-01T23:59:59.000Z

    This paper introduces a list of observations related to the beam-beam interaction that were collected over the first years of LHC proton physics operation (2010-12). Beam-beam related effects not only have been extensively observed and recorded, but have also shaped the operation of the LHC for high-intensity proton running in a number of ways: the construction of the filling scheme, the choice of luminosity levelling techniques, measures to mitigate instabilities, and the choice of settings for improving performance (e.g. to reduce losses), among others.

  11. Precision Absolute Beam Current Measurement of Low Power Electron Beam

    SciTech Connect (OSTI)

    Ali, M. M.; Bevins, M. E.; Degtiarenko, P.; Freyberger, A.; Krafft, G. A.

    2012-11-01T23:59:59.000Z

    Precise measurements of low power CW electron beam current for the Jefferson Lab Nuclear Physics program have been performed using a Tungsten calorimeter. This paper describes the rationale for the choice of the calorimeter technique, as well as the design and calibration of the device. The calorimeter is in use presently to provide a 1% absolute current measurement of CW electron beam with 50 to 500 nA of average beam current and 1-3 GeV beam energy. Results from these recent measurements will also be presented.

  12. Neutral Beam Excitation

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's Possible for Renewable Energy:Nanowire Solar541,9337, 2011 at3, Issue 30 NewNetworks,Beam

  13. Beam characterization by wavefront sensor

    DOE Patents [OSTI]

    Neal, D.R.; Alford, W.J.; Gruetzner, J.K.

    1999-08-10T23:59:59.000Z

    An apparatus and method are disclosed for characterizing an energy beam (such as a laser) with a two-dimensional wavefront sensor, such as a Shack-Hartmann lenslet array. The sensor measures wavefront slope and irradiance of the beam at a single point on the beam and calculates a space-beamwidth product. A detector array such as a charge coupled device camera is preferably employed. 21 figs.

  14. Beam emittance measurements at Fermilab

    SciTech Connect (OSTI)

    Wendt, Manfred; Eddy, Nathan; Hu, Martin; Scarpine, Victor; Syphers, Mike; Tassotto, Gianni; Thurman-Keup, Randy; Yang, Ming-Jen; Zagel, James; /Fermilab

    2008-01-01T23:59:59.000Z

    We give short overview of various beam emittance measurement methods, currently applied at different machine locations for the Run II collider physics program at Fermilab. All these methods are based on beam profile measurements, and we give some examples of the related instrumentation techniques. At the end we introduce a multi-megawatt proton source project, currently under investigation at Fermilab, with respect to the beam instrumentation challenges.

  15. Properties of Inconel 625 Mesh Structures Grown by Electron Beam Additive Manufacturing

    SciTech Connect (OSTI)

    List III, Frederick Alyious [ORNL; Dehoff, Ryan R [ORNL; Lowe, Larry E [ORNL; Sames, William J [ORNL

    2014-01-01T23:59:59.000Z

    Relationships between electron beam parameters (beam current, beam speed, and beam focus) and physical properties (mass, diameter, elastic modulus, and yield strength) have been investigated for Inconel 625 mesh cubes fabricated using an additive manufacturing technology based on electron beam melting. The elastic modulus and yield strength of the mesh cubes have been systematically varied by approximately a factor of ten by changing the electron beam parameters. Simple models have been used to understand better these relationships. Structural anisotropies of the mesh associated with the layered build architecture have been observed and may contribute, along with microstructural anisotropies, to the anisotropic mechanical properties of the mesh. Knowledge of this kind is likely applicable to other metal and alloy systems and is essential to rapidly realize the full potential of this burgeoning technology.

  16. First LHC Beams in ATLAS

    E-Print Network [OSTI]

    Krieger, P

    2009-01-01T23:59:59.000Z

    This is a talk on the ATLAS single beam running, to be given on February 9th at the Aspen Winter Conference.

  17. ANL Beams and Applications Seminar

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    characterization of the laser and electron beams of the Cornell Energy Recovery Linac Heng Li Cornell University June 18 Interbeam Scattering Studies at CesrTA Michael Ehrlichman...

  18. Broad-band beam buncher

    DOE Patents [OSTI]

    Goldberg, David A. (Walnut Creek, CA); Flood, William S. (Berkeley, CA); Arthur, Allan A. (Martinez, CA); Voelker, Ferdinand (Orinda, CA)

    1986-01-01T23:59:59.000Z

    A broad-band beam buncher is disclosed, comprising an evacuated housing, an electron gun therein for producing an electron beam, a buncher cavity having entrance and exit openings through which the beam is directed, grids across such openings, a source providing a positive DC voltage between the cavity and the electron gun, a drift tube through which the electron beam travels in passing through such cavity, grids across the ends of such drift tube, gaps being provided between the drift tube grids and the entrance and exit grids, a modulator for supplying an ultrahigh frequency modulating signal to the drift tube for producing velocity modulation of the electrons in the beam, a drift space in the housing through which the velocity modulated electron beam travels and in which the beam is bunched, and a discharge opening from such drift tube and having a grid across such opening through which the bunched electron beam is discharged into an accelerator or the like. The buncher cavity and the drift tube may be arranged to constitute an extension of a coaxial transmission line which is employed to deliver the modulating signal from a signal source. The extended transmission line may be terminated in its characteristic impedance to afford a broad-band response and the device as a whole designed to effect broad-band beam coupling, so as to minimize variations of the output across the response band.

  19. Ion source for high-precision mass spectrometry

    DOE Patents [OSTI]

    Todd, P.J.; McKown, H.S.; Smith, D.H.

    1982-04-26T23:59:59.000Z

    The invention is directed to a method for increasing the precision of positive-ion relative abundance measurements conducted in a sector mass spectrometer having an ion source for directing a beam of positive ions onto a collimating slit. The method comprises incorporating in the source an electrostatic lens assembly for providing a positive-ion beam of circular cross section for collimation by the slit. 2 figures, 3 tables.

  20. Molecular Dynamics Simulation of GaAs Molecular Beam Epitaxy D. A. Murdick,1

    E-Print Network [OSTI]

    Wadley, Haydn

    of Virginia, Charlottesville, Virginia 22904, USA 2 Department of Materials, University of Oxford, Oxford OX1 3PH, UK ABSTRACT The vapor deposition of epitaxial GaAs and (Ga,Mn)As thin films during far-temperature growth of Ga0.94Mn0.06As and the Mn clustering trends in as-grown films. INTRODUCTION GaAs is widely used

  1. NEUTRAL-BEAM INJECTION

    SciTech Connect (OSTI)

    Kunkel, W.B.

    1980-06-01T23:59:59.000Z

    The emphasis in the preceding chapters has been on magnetic confinement of high temperature plasmas. The question of production and heating of such plasmas has been dealt with relatively more briefly. It should not be inferred, however, that these matters must therefore be either trivial or unimportant. A review of the history reveals that in the early days all these aspects of the controlled fusion problem were considered to be on a par, and were tackled simultaneously and with equal vigor. Only the confinement problem turned out to be much more complex than initially anticipated, and richer in challenge to the plasma physicist than the questions of plasma production and heating. On the other hand, the properties of high-temperature plasmas and plasma confinement can only be studied experimentally after the problems of production and of heating to adequate temperatures are solved. It is the purpose of this and the next chapter to supplement the preceding discussions with more detail on two important subjects: neutral-beam injection and radio-frequency heating. These are the major contenders for heating in present and future tokamak and mirror fusion experiments, and even in several proposed reactors. For neutral beams we emphasize here the technology involved, which has undergone a rather remarkable development. The physics of particle and energy deposition in the plasma, and the discussion of the resulting effects on the confined plasma, have been included in previous chapters, and some experimental results are quoted there. Other heating processes of relevance to fusion are mentioned elsewhere in this book, in connection with the experiments where they are used: i.e. ohmic heating, adiabatic compression heating, and alpha-particle heating in Chapter 3 by H.P. Furth; more ohmic heating in Chapter 7, and shock-implosion heating, laser heating, and relativistic-electron beam heating in Chapter 8, both by W. E. Quinn. These methods are relatively straightforward in their physics and their technology, or in any case they are considered to be adequately covered by these other authors.

  2. Studies of beam dynamics in relativistic klystron two-beam accelerators

    SciTech Connect (OSTI)

    Lidia, Steven M.

    1999-11-01T23:59:59.000Z

    Two-beam accelerators (TBAs) based upon free-electron lasers (FELs) or relativistic klystrons (RK-TBAs) have been proposed as efficient power sources for next generation high-energy linear colliders. Studies have demonstrated the possibility of building TBAs from X-band ({approximately}8-12 GHz) through Ka band ({approximately} 30-35 GHz) frequency regions. Provided that further prototyping shows stable beam propagation with minimal current loss and production of good quality, high-power rf fields, this technology is compatible with current schemes for electron-positron colliders in the multi-TeV center-of-mass scale. A new method of simulating the beam dynamics in accelerators of this type has been developed in this dissertation. There are three main components to this simulation. The first is a tracking algorithm to generate nonlinear transfer maps for pushing noninteracting particles through the external fields. The second component is a 3D Particle-In-Cell (PIC) algorithm that solves a set of Helmholtz equations for the self-fields, including the conducting boundary condition, and generates impulses that are interleaved with the nonlinear maps by means of a split-operation algorithm. The Helmholtz equations are solved by a multi-grid algorithm. The third component is an equivalent circuit equation solver that advances the modal rf cavity fields in time due to excitation by the modulated beam. The RTA project is described, and the simulation code is used to design the latter portions of the experiment. Detailed calculations of the beam dynamics and of the rf cavity output are presented and discussed. A beamline design is presented that will generate nearly 1.2 GW of power from 40 input, gain, and output rv cavities over a 10 m distance. The simulations show that beam current losses are acceptable, and that longitudinal and transverse focusing techniques are sufficient capable of maintaining a high degree of beam quality along the entire beamline. Additional experimental efforts are also described.

  3. Laser acceleration of ion beams

    E-Print Network [OSTI]

    I. A. Egorova; A. V. Filatov; A. V. Prozorkevich; S. A. Smolyansky; D. B. Blaschke; M. Chubaryan

    2007-02-01T23:59:59.000Z

    We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.

  4. Head-on beam-beam collisions with high intensities and long range beam-beam studies in the LHC

    E-Print Network [OSTI]

    Albert, M; Assmann, R; Buffat, X; Calaga, R; Cornelis, K; Fitterer, M; Giachino, R; Herr, W; Miyamoto, R; Norman, L; Papotti, G; Pieloni, T; Ponce, L; Redaelli, S; Schaumann, M; Trad, G; Wollmann, D

    2011-01-01T23:59:59.000Z

    In two experiments we studied possible limitations due to the beam-beam effects in the LHC. In the first experiment we collided high intensity bunches head-on to explore the region for high luminosity collisions. In the second test we reduced the crossing angle in the presence of long range encounters to increase their effects.

  5. Adaptive Optics Imaging of IRAS 18276-1431: a bipolar pre-planetary nebula with circumstellar "searchlight beams" and "arcs"

    E-Print Network [OSTI]

    Contreras, C S; Sahai, R; De Paz, A G; Morris, M

    2006-01-01T23:59:59.000Z

    We present high-angular resolution images of the post-AGB nebula IRAS18276-1431 (also known as OH17.7-2.0) obtained with the Keck II Adaptive Optics (AO) system in its Natural Guide Star (NGS) mode in the Kp, Lp, and Ms near-infrared bands. We also present supporting optical F606W and F814W HST images as well as interferometric observations of the 12CO(J=1-0), 13CO(J=1-0), and 2.6mm continuum emission with OVRO. The envelope of IRAS18276-1431 displays a clear bipolar morphology in our optical and NIR images with two lobes separated by a dark waist and surrounded by a faint 4.5"x3.4" halo. Our Kp-band image reveals two pairs of radial ``searchlight beams'' emerging from the nebula center and several intersecting, arc-like features. From our CO data we derive a mass of M>0.38[D/3kpc]^2 Msun and an expansion velocity v_exp=17km/s for the molecular envelope. The density in the halo follows a radial power-law proportional to r^-3, which is consistent with a mass-loss rate increasing with time. Analysis of the NIR ...

  6. Simulation of multicomponent evaporation in electron beam melting and refining

    SciTech Connect (OSTI)

    Powell, A.; Szekely, J. [Massachusetts Inst. of Tech., Cambridge, MA (United States); Van Den Avyle, J.; Damkroger, B. [Sandia National Labs., Albuquerque, NM (United States)

    1996-06-01T23:59:59.000Z

    Experimental results and a mathematical model are presented to describe differential evaporation rates in electron beam melting of titanium alloys containing aluminum and vanadium. Experiments characterized the evaporation rate of commercially pure titanium, and vapor composition over titanium with up to 6% Al and 4.5% V content as a function of beam power, scan frequency and background pressure. The model is made up of a steady-state heat and mass transport model of a melting hearth and a model of transient thermal and flow behavior near the surface. Activity coefficients for aluminum and vanadium in titanium are roughly estimated by fitting model parameters to experimental results. Based on the ability to vary evaporation rate by 10-15% using scan frequency alone, we discuss the possibility of on-line composition control by means of intelligent manipulation of the electron beam.

  7. The COMPASS Setup for Physics with Hadron Beams

    E-Print Network [OSTI]

    Abbon, Ph.; Akhunzyanov, R.; Alexandrov, Yu.; Alexeev, M.G.; Alexeev, G.D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Austregesilo, A.; Badelek, B.; Balestra, F.; Barth, J.; Baum, G.; Beck, R.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bicker, K.; Bielert, E.R.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Buchele, M.; Burtin, E.; Capozza, L.; Ciliberti, P.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Colantoni, M.; Cotte, D.; Crespo, M.L.; Curiel, Q.; Dafni, T.; Dalla Torre, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Desforge, D.; Dinkelbach, A.M.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Durand, D.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Finger, M.; M. Finger jr; Fischer, H.; Franco, C.; von Hohenesche, N. du Fresne; Friedrich, J.M.; Frolov, V.; Gatignon, L.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Giganon, A.; Gnesi, I.; Gobbo, B.; Goertz, S.; Gorzellik, M.; Grabmuller, S.; Grasso, A.; Gregori, M.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Haas, F.; von Harrach, D.; Hahne, D.; Hashimoto, R.; Heinsius, F.H.; Herrmann, F.; Hinterberger, F.; Hoppner, Ch.; Horikawa, N.; d'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Jorg, P.; Joosten, R.; Kabuss, E.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kroumchtein, Z.V.; Kuchinski, N.; Kuhn, R.; Kunne, F.; Kurek, K.; Kurjata, R.P.; Lednev, A.A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G.K.; Marchand, C.; Marroncle, J.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Menon, G.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Moinester, M.A.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.I.; Novy, J.; Nowak, W.D.; Nunes, Ana Sofia; Olshevsky, A.G.; Orlov, I.; Ostrick, M.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Pesaro, G.; Pesaro, V.; Peshekhonov, D.V.; Pires, C.; Platchkov, S.; Pochodzalla, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Reymond, J-M.; Rocco, E.; Rossiyskaya, N.S.; Rousse, J.Y.; Ryabchikov, D.I.; Rychter, A.; Samartsev, A.; Samoylenko, V.D.; Sandacz, A.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schluter, T.; Schmidt, K.; Schmieden, H.; Schonning, K.; Schopferer, S.; Schott, M.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Wolbeek, J. ter; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Tskhay, V.; Uhl, S.; Uman, I.; Virius, M.; Wang, L.; Weisrock, T.; Weitzel, Q.; Wilfert, M.; Windmolders, R.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.

    2014-01-01T23:59:59.000Z

    The main characteristics of the COMPASS experimental setup for physics with hadron beams are described. This setup was designed to perform exclusive measurements of processes with several charged and/or neutral particles in the final state. Making use of a large part of the apparatus that was previously built for spin structure studies with a muon beam, it also features a new target system as well as new or upgraded detectors. The hadron setup is able to operate at the high incident hadron flux available at CERN. It is characterised by large angular and momentum coverages, large and nearly flat acceptances, and good two and three-particle mass resolutions. In 2008 and 2009 it was successfully used with positive and negative hadron beams and with liquid hydrogen and solid nuclear targets. This article describes the new and upgraded detectors and auxiliary equipment, outlines the reconstruction procedures used, and summarises the general performance of the setup.

  8. Toward automated beam optics control

    SciTech Connect (OSTI)

    Silbar, R.R.; Schultz, D.E.

    1987-01-01T23:59:59.000Z

    We have begun a program aiming toward automatic control of charged-particle beam optics using artificial intelligence programming techniques. In developing our prototype, we are working with LISP machines and the KEE expert system shell. Our first goal was to develop a ''mouseable'' representation of a typical beam line. This responds actively to changes entered from the mouse or keyboard, giving an updated display of the beam line itself, its optical properties, and the instrumentation and control devices as seen by the operater. We have incorporated TRANSPORT, written in Fortran but running as a callable procedure in the LISP environment, for simulation of the beam-line optics. This paper describes the experience gained in meeting our first goal and discusses plans to extend the work so that it is usable, in realtime, on an operating beam line. 11 refs.

  9. Formation of the diphenyl molecule in the crossed beam reaction of phenyl radicals with benzene

    SciTech Connect (OSTI)

    Zhang Fangtong; Gu Xibin; Kaiser, Ralf I. [Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822 (United States)

    2008-02-28T23:59:59.000Z

    The chemical dynamics to form the D5-diphenyl molecule, C{sub 6}H{sub 5}C{sub 6}D{sub 5}, via the neutral-neutral reaction of phenyl radicals (C{sub 6}H{sub 5}) with D6-benzene (C{sub 6}D{sub 6}), was investigated in a crossed molecular beams experiment at a collision energy of 185 kJ mol{sup -1}. The laboratory angular distribution and time-of-flight spectra of the C{sub 6}H{sub 5}C{sub 6}D{sub 5} product were recorded at mass to charge m/z of 159. Forward-convolution fitting of our data reveals that the reaction dynamics are governed by an initial addition of the phenyl radical to the {pi} electron density of the D6-benzene molecule yielding a short-lived C{sub 6}H{sub 5}C{sub 6}D{sub 6} collision complex. The latter undergoes atomic deuterium elimination via a tight exit transition state located about 30 kJ mol{sup -1} above the separated reactants; the overall reaction to form D5-diphenyl from phenyl and D6-benzene was found to be weakly exoergic. The explicit identification of the D5-biphenyl molecules suggests that in high temperature combustion flames, a diphenyl molecule can be formed via a single collision event between a phenyl radical and a benzene molecule.

  10. Excited-Level Lifetimes and Hyperfine-Structure Measurements on Ions using Collinear Laser Ion-Beam Spectroscopy

    E-Print Network [OSTI]

    Jin, J.; Church, David A.

    1994-01-01T23:59:59.000Z

    resolve isotopic beams of Ca+ or Cl+. However, each isotopic mass had a different velocity, and hence Doppler shift, following subsequent acceleration to and within the DSS. Consequently ion isotopes other than the dominant iso- tope had significantly...

  11. Delivering High IntensityDelivering High Intensity Proton Beam:Proton Beam

    E-Print Network [OSTI]

    McDonald, Kirk

    11 Delivering High IntensityDelivering High Intensity Proton Beam:Proton Beam: Lessons for the NextFACT08NuFACT08 ­­ 4 July4 July S. ChildressS. Childress ­­ Proton BeamsProton Beams 22 Presentation OutlinePresentation Outline Key Proton Beam ConsiderationsKey Proton Beam Considerations The First

  12. Molecular information ratchets 

    E-Print Network [OSTI]

    Wilson, Adam Christopher

    2012-11-28T23:59:59.000Z

    In the emerging aield of molecular machines, a molecular ratchet is a chemical system that allows the positional displacement of a submolecular component of be captured and directionally relea ...

  13. Laser beam alignment apparatus and method

    DOE Patents [OSTI]

    Gruhn, Charles R. (Martinez, CA); Hammond, Robert B. (Los Alamos, NM)

    1981-01-01T23:59:59.000Z

    The disclosure relates to an apparatus and method for laser beam alignment. Thermoelectric properties of a disc in a laser beam path are used to provide an indication of beam alignment and/or automatic laser alignment.

  14. EMSL - Molecular Science Computing

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    computing Resources and Techniques Molecular Science Computing - Sophisticated and integrated computational capabilities, including scientific consultants, software, Cascade...

  15. Neutrino mass matrix

    SciTech Connect (OSTI)

    Strobel, E.L.

    1985-01-01T23:59:59.000Z

    Given the many conflicting experimental results, examination is made of the neutrino mass matrix in order to determine possible masses and mixings. It is assumed that the Dirac mass matrix for the electron, muon, and tau neutrinos is similar in form to those of the quarks and charged leptons, and that the smallness of the observed neutrino masses results from the Gell-Mann-Ramond-Slansky mechanism. Analysis of masses and mixings for the neutrinos is performed using general structures for the Majorana mass matrix. It is shown that if certain tentative experimental results concerning the neutrino masses and mixing angles are confirmed, significant limitations may be placed on the Majorana mass matrix. The most satisfactory simple assumption concerning the Majorana mass matrix is that it is approximately proportional to the Dirac mass matrix. A very recent experimental neutrino mass result and its implications are discussed. Some general properties of matrices with structure similar to the Dirac mass matrices are discussed.

  16. Electrostatic wire stabilizing a charged particle beam

    DOE Patents [OSTI]

    Prono, D.S.; Caporaso, G.J.; Briggs, R.J.

    1983-03-21T23:59:59.000Z

    In combination with a charged particle beam generator and accelerator, apparatus and method are provided for stabilizing a beam of electrically charged particles. A guiding means, disposed within the particle beam, has an electric charge induced upon it by the charged particle beam. Because the sign of the electric charge on the guiding means and the sign of the particle beam are opposite, the particles are attracted toward and cluster around the guiding means to thereby stabilize the particle beam as it travels.

  17. Ultra High Mass Range Mass Spectrometer System

    DOE Patents [OSTI]

    Reilly, Peter T. A. [Knoxville, TN

    2005-12-06T23:59:59.000Z

    Applicant's present invention comprises mass spectrometer systems that operate in a mass range from 1 to 10.sup.16 DA. The mass spectrometer system comprising an inlet system comprising an aerodynamic lens system, a reverse jet being a gas flux generated in an annulus moving in a reverse direction and a multipole ion guide; a digital ion trap; and a thermal vaporization/ionization detector system. Applicant's present invention further comprises a quadrupole mass spectrometer system comprising an inlet system having a quadrupole mass filter and a thermal vaporization/ionization detector system. Applicant's present invention further comprises an inlet system for use with a mass spectrometer system, a method for slowing energetic particles using an inlet system. Applicant's present invention also comprises a detector device and a method for detecting high mass charged particles.

  18. Effective Mass and Energy-Mass Relationship

    E-Print Network [OSTI]

    Viktor Ariel

    2012-05-14T23:59:59.000Z

    The particle effective mass is often a challenging concept in solid state physics due to the many different definitions of the effective mass that are routinely used. Also, the most commonly used theoretical definition of the effective mass was derived from the assumption of a parabolic energy-momentum relationship, E(p), and therefore should not be applied to non-parabolic materials. In this paper, we use wave-particle duality to derive a definition of the effective mass and the energy-mass approximation suitable for non-parabolic materials. The new energy-mass relationship can be considered a generalization of Einstein's E=mc^2 suitable for arbitrary E(p) and therefore applicable to solid state materials and devices. We show that the resulting definition of the effective mass seems suitable for non-paraboic solid state materials such as HgCdTe, GaAs, and graphene.

  19. MEASUREMENT OF BEAM CHARACTERISTICS FOR PHOTO- ELECTRON BEAM...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    electron beam is expected to be used in a wide field, such as X-ray generation by inverse Compton scattering, pulse radiolysis, etc. The laser driven photo cathode rf gun system is...

  20. Electron beam machining using rotating and shaped beam power distribution

    DOE Patents [OSTI]

    Elmer, J.W.; O`Brien, D.W.

    1996-07-09T23:59:59.000Z

    An apparatus and method are disclosed for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: (1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and (2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1,000 {micro}m (1 mm or larger), compared to the 250 {micro}m diameter of laser drilling. 5 figs.

  1. Electron beam machining using rotating and shaped beam power distribution

    DOE Patents [OSTI]

    Elmer, John W. (Pleasanton, CA); O'Brien, Dennis W. (Livermore, CA)

    1996-01-01T23:59:59.000Z

    An apparatus and method for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: 1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and 2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1000 .mu.m (1 mm or larger), compared to the 250 .mu.m diameter of laser drilling.

  2. Alight a beam and beaming light: A theme with variations

    SciTech Connect (OSTI)

    Chattopadhyay, S. [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California94720 (United States)] [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California94720 (United States)

    1998-05-01T23:59:59.000Z

    The interaction of light (coherent and incoherent) with charged particle beams is explored in various configurations: incoherent scattering of coherent light (laser) from an incoherent particle beam (high temperature), coherent scattering of coherent light (laser) from a {open_quotes}cold{close_quotes} (bunched) beam, femtosecond generation of particle and light beams via {open_quotes}optical slicing{close_quotes} and Thomson/Compton scattering techniques, etc. The domains of ultrashort temporal duration (femtoseconds) as well as ultrashort wavelengths (x rays and shorter), with varying degrees of coherence, are explored. The relevance to a few critical areas of research in the natural sciences, e.g., ultrafast material, chemical and biological processes, protein folding, particle phase space cooling, etc. are touched upon. All the processes discussed involve proper interpretation and understanding of coherent states of matter and radiation, as well as the quality and quantity of information and energy embedded in them. {copyright} {ital 1998 American Institute of Physics.}

  3. PURIFICATION OF IRIDIUM BY ELECTRON BEAM MELTING

    SciTech Connect (OSTI)

    Ohriner, Evan Keith [ORNL

    2008-01-01T23:59:59.000Z

    The purification of iridium metal by electron beam melting has been characterized for 48 impurity elements. Chemical analysis was performed by glow discharge mass spectrographic (GDMS) analysis for all elements except carbon, which was analyzed by combustion. The average levels of individual elemental impurities in the starting powder varied from 37 g/g to 0.02 g/g. The impurity elements Li, Na, Mg, P, S, Cl, K, Ca, Mn, Co, Ni, Cu, Zn, As, Pd, Ag, Cd, Sn, Sb, Te, Ba, Ce, Tl, Pb, and Bi were not detectable following the purification. No significant change in concentration of the elements Ti, V, Zr, Nb, Mo, and Re was found. The elements B, C, Al, Si, Cr, Fe, Ru, Rh, and Pt were partially removed by vaporization during electron beam melting. Langmuir's equation for ideal vaporization into a vacuum was used to calculate for each impurity element the expected ratio of impurity content after melting to that before melting. Equilibrium vapor pressures were calculated using Henry's law, with activity coefficients obtained from published data for the elements Fe, Ti, and Pt. Activity coefficients were estimated from enthalpy data for Al, Si, V, Cr, Mn, Co, Ni, Zr, Nb, Mo, and Hf and an ideal solution model was used for the remaining elements. The melt temperature was determined from measured iridium weight loss. Excellent agreement was found between measured and calculated impurity ratios for all impurity elements. The results are consistent with some localized heating of the melt pool due to rastering of the electron beam, with an average vaporization temperature of 3100 K as compared to a temperature of 2965 K calculated for uniform heating of the melt pool. The results are also consistent with ideal mixing in the melt pool.

  4. Thermal stresses in laminated beams

    E-Print Network [OSTI]

    Marcano, Victor Manuel

    1983-01-01T23:59:59.000Z

    Stresses Acting on a Section of the Laminated Beam -------- 15 5. Loading Geometry and Material Characteristics of the Test Problem 21 6. Simply-Supported Beam with a Sinusoidal Load--------- 30 7. Shear Stress Distribution for a Simply- Supported... 24. Normal Stress Distribution for a Cantilever Laminated Beam, T-Z sinzx/L --------------- 58 m. i 25. Axial Stress Distribution for a Cantilever Laminated Bearq, T-T (2z/8+1) 2 mi 27. Normal Stress Distribution for ("/L) ? ---- 6O 2 a...

  5. Thermal stresses in laminated beams 

    E-Print Network [OSTI]

    Marcano, Victor Manuel

    1983-01-01T23:59:59.000Z

    Stresses Acting on a Section of the Laminated Beam -------- 15 5. Loading Geometry and Material Characteristics of the Test Problem 21 6. Simply-Supported Beam with a Sinusoidal Load--------- 30 7. Shear Stress Distribution for a Simply- Supported... 24. Normal Stress Distribution for a Cantilever Laminated Beam, T-Z sinzx/L --------------- 58 m. i 25. Axial Stress Distribution for a Cantilever Laminated Bearq, T-T (2z/8+1) 2 mi 27. Normal Stress Distribution for ("/L) ? ---- 6O 2 a...

  6. Circular, confined distribution for charged particle beams

    DOE Patents [OSTI]

    Garnett, R.W.; Dobelbower, M.C.

    1995-11-21T23:59:59.000Z

    A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location. 26 figs.

  7. Circular, confined distribution for charged particle beams

    DOE Patents [OSTI]

    Garnett, Robert W. (Los Alamos, NM); Dobelbower, M. Christian (Toledo, OH)

    1995-01-01T23:59:59.000Z

    A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location.

  8. Beam-powered lunar rover design

    SciTech Connect (OSTI)

    Dagle, J.E.; Coomes, E.P.; Antoniak, Z.I.; Bamberger, J.A.; Bates, J.M.; Chiu, M.A.; Dodge, R.E.; Wise, J.A.

    1992-03-01T23:59:59.000Z

    Manned exploration of our nearest neighbors in the solar systems is the primary goal of the Space Exploration Initiative (SEI). An integral part of any manned lunar or planetary outpost will be a system for manned excursions over the surface of the planet. This report presents a preliminary design for a lunar rover capable of supporting four astronauts on long-duration excursions across the lunar landscape. The distinguishing feature of this rover design is that power is provided to rover via a laser beam from an independent orbiting power satellite. This system design provides very high power availability with minimal mass on the rover vehicle. With this abundance of power, and with a relatively small power-system mass contained in the rover, the vehicle can perform an impressive suite of mission-related activity. The rover might be used as the first outpost for the lunar surface (i.e., a mobile base). A mobile base has the advantage of providing extensive mission activities without the expense of establishing a fixed base. This concept has been referred to as Rove First.'' A manned over, powered through a laser beam, has been designed for travel on the lunar surface for round-trip distances in the range of 1000 km, although the actual distance traveled is not crucial since the propulsion system does not rely on energy storage. The life support system can support a 4-person crew for up to 30 days, and ample power is available for mission-related activities. The 8000-kg rover has 30 kW of continuous power available via a laser transmitter located at the Earth-moon L1 libration point, about 50,000 km above the surface of the moon. This rover, which is designed to operate in either day or night conditions, has the flexibility to perform a variety of power-intensive missions. 24 refs.

  9. Beam-powered lunar rover design

    SciTech Connect (OSTI)

    Dagle, J.E.; Coomes, E.P.; Antoniak, Z.I.; Bamberger, J.A.; Bates, J.M.; Chiu, M.A.; Dodge, R.E.; Wise, J.A.

    1992-03-01T23:59:59.000Z

    Manned exploration of our nearest neighbors in the solar systems is the primary goal of the Space Exploration Initiative (SEI). An integral part of any manned lunar or planetary outpost will be a system for manned excursions over the surface of the planet. This report presents a preliminary design for a lunar rover capable of supporting four astronauts on long-duration excursions across the lunar landscape. The distinguishing feature of this rover design is that power is provided to rover via a laser beam from an independent orbiting power satellite. This system design provides very high power availability with minimal mass on the rover vehicle. With this abundance of power, and with a relatively small power-system mass contained in the rover, the vehicle can perform an impressive suite of mission-related activity. The rover might be used as the first outpost for the lunar surface (i.e., a mobile base). A mobile base has the advantage of providing extensive mission activities without the expense of establishing a fixed base. This concept has been referred to as ``Rove First.`` A manned over, powered through a laser beam, has been designed for travel on the lunar surface for round-trip distances in the range of 1000 km, although the actual distance traveled is not crucial since the propulsion system does not rely on energy storage. The life support system can support a 4-person crew for up to 30 days, and ample power is available for mission-related activities. The 8000-kg rover has 30 kW of continuous power available via a laser transmitter located at the Earth-moon L1 libration point, about 50,000 km above the surface of the moon. This rover, which is designed to operate in either day or night conditions, has the flexibility to perform a variety of power-intensive missions. 24 refs.

  10. Confined energy distribution for charged particle beams

    DOE Patents [OSTI]

    Jason, Andrew J. (Los Alamos, NM); Blind, Barbara (Los Alamos, NM)

    1990-01-01T23:59:59.000Z

    A charged particle beam is formed to a relatively larger area beam which is well-contained and has a beam area which relatively uniformly deposits energy over a beam target. Linear optics receive an accelerator beam and output a first beam with a first waist defined by a relatively small size in a first dimension normal to a second dimension. Nonlinear optics, such as an octupole magnet, are located about the first waist and output a second beam having a phase-space distribution which folds the beam edges along the second dimension toward the beam core to develop a well-contained beam and a relatively uniform particle intensity across the beam core. The beam may then be expanded along the second dimension to form the uniform ribbon beam at a selected distance from the nonlinear optics. Alternately, the beam may be passed through a second set of nonlinear optics to fold the beam edges in the first dimension. The beam may then be uniformly expanded along the first and second dimensions to form a well-contained, two-dimensional beam for illuminating a two-dimensional target with a relatively uniform energy deposition.

  11. STOCHASTIC COOLING FOR BUNCHED BEAMS.

    SciTech Connect (OSTI)

    BLASKIEWICZ, M.

    2005-05-16T23:59:59.000Z

    Problems associated with bunched beam stochastic cooling are reviewed. A longitudinal stochastic cooling system for RHIC is under construction and has been partially commissioned. The state of the system and future plans are discussed.

  12. Molecular electrostatic potentials by systematic molecular fragmentation

    SciTech Connect (OSTI)

    Reid, David M.; Collins, Michael A. [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)] [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)

    2013-11-14T23:59:59.000Z

    A simple method is presented for estimating the molecular electrostatic potential in and around molecules using systematic molecular fragmentation. This approach estimates the potential directly from the electron density. The accuracy of the method is established for a set of organic molecules and ions. The utility of the approach is demonstrated by estimating the binding energy of a water molecule in an internal cavity in the protein ubiquitin.

  13. Mass Spectral Molecular Networking of Living Microbial Colonies...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of Living Microbial Colonies. Abstract: Integrating the governing chemistry with the genomics and phenotypes of microbial colonies has been a "holy grail" in...

  14. Stability diagram of colliding beams

    E-Print Network [OSTI]

    Buffat, X; Mounet, N; Pieloni, T

    2014-01-01T23:59:59.000Z

    The effect of the beam-beam interactions on the stability of impedance mode is discussed. The detuning is evaluated by the means of single particle tracking in arbitrarily complex collision configurations, including lattice non-linearities, and used to numerically evaluate the dispersion integral. This approach also allows the effect of non-Gaussian distributions to be considered. Distributions modified by the action of external noise are discussed.

  15. Single lens laser beam shaper

    DOE Patents [OSTI]

    Liu, Chuyu (Newport News, VA); Zhang, Shukui (Yorktown, VA)

    2011-10-04T23:59:59.000Z

    A single lens bullet-shaped laser beam shaper capable of redistributing an arbitrary beam profile into any desired output profile comprising a unitary lens comprising: a convex front input surface defining a focal point and a flat output portion at the focal point; and b) a cylindrical core portion having a flat input surface coincident with the flat output portion of the first input portion at the focal point and a convex rear output surface remote from the convex front input surface.

  16. Mass spectrometric immunoassay

    DOE Patents [OSTI]

    Nelson, Randall W; Williams, Peter; Krone, Jennifer Reeve

    2013-07-16T23:59:59.000Z

    Rapid mass spectrometric immunoassay methods for detecting and/or quantifying antibody and antigen analytes utilizing affinity capture to isolate the analytes and internal reference species (for quantification) followed by mass spectrometric analysis of the isolated analyte/internal reference species. Quantification is obtained by normalizing and calibrating obtained mass spectrum against the mass spectrum obtained for an antibody/antigen of known concentration.

  17. Mass spectrometric immunoassay

    DOE Patents [OSTI]

    Nelson, Randall W (Phoenix, AZ); Williams, Peter (Phoenix, AZ); Krone, Jennifer Reeve (Granbury, TX)

    2007-12-04T23:59:59.000Z

    Rapid mass spectrometric immunoassay methods for detecting and/or quantifying antibody and antigen analytes utilizing affinity capture to isolate the analytes and internal reference species (for quantification) followed by mass spectrometric analysis of the isolated analyte/internal reference species. Quantification is obtained by normalizing and calibrating obtained mass spectrum against the mass spectrum obtained for an antibody/antigen of known concentration.

  18. The effect of inclination and stand-off on the dynamic response of beams impacted by slugs of a granular material

    E-Print Network [OSTI]

    Uth, T.; Wadley, H. N. G.; Deshpande, V. S.

    2014-12-04T23:59:59.000Z

    areal masses of 𝑚 = 5.6  kg  m-2. The rigid beam was machined from a solid block of aluminium alloy and served as a reference to quantify the momentum transmitted into a nominally rigid structure. Sandwich beams comprised two identical AISI 304... stainless steel, while the sandwich beams of equal areal mass comprised stainless steel face sheets and an aluminium honeycomb core. High-speed imaging was used to measure the transient transverse deflection of the beams, to record the dynamic modes...

  19. Electron beam diagnostic for profiling high power beams

    DOE Patents [OSTI]

    Elmer, John W. (Danville, CA); Palmer, Todd A. (Livermore, CA); Teruya, Alan T. (Livermore, CA)

    2008-03-25T23:59:59.000Z

    A system for characterizing high power electron beams at power levels of 10 kW and above is described. This system is comprised of a slit disk assembly having a multitude of radial slits, a conducting disk with the same number of radial slits located below the slit disk assembly, a Faraday cup assembly located below the conducting disk, and a start-stop target located proximate the slit disk assembly. In order to keep the system from over-heating during use, a heat sink is placed in close proximity to the components discussed above, and an active cooling system, using water, for example, can be integrated into the heat sink. During use, the high power beam is initially directed onto a start-stop target and after reaching its full power is translated around the slit disk assembly, wherein the beam enters the radial slits and the conducting disk radial slits and is detected at the Faraday cup assembly. A trigger probe assembly can also be integrated into the system in order to aid in the determination of the proper orientation of the beam during reconstruction. After passing over each of the slits, the beam is then rapidly translated back to the start-stop target to minimize the amount of time that the high power beam comes in contact with the slit disk assembly. The data obtained by the system is then transferred into a computer system, where a computer tomography algorithm is used to reconstruct the power density distribution of the beam.

  20. KTeV beam systems design report

    SciTech Connect (OSTI)

    Bocean, V.; Childress, S.; Coleman, R. [and others

    1997-09-01T23:59:59.000Z

    The primary and secondary beams for the KTeV experiments E799-II and E832 are discussed. The specifications are presented and justified. The technical details of the implementation of the primary beam transport and stability are detailed. The target, beam dump, and radiation safety issues are discussed. The details of the collimation system for the pair of secondary beams are presented.

  1. Head-on beam-beam tune shifts with high brightness beams in the LHC

    E-Print Network [OSTI]

    Alemany, R; Calaga, R; Cornelis, K; Fitterer, M; Giachino, R; Herr, W; McPherson, A; Miyamoto, R; Papotti, G; Pieloni, T; Redaelli, S; Roncarolo, F; Schaumann, M; Suykerbuyk, R; Trad, G; Paret, S

    2011-01-01T23:59:59.000Z

    In this experiment (fills 1765, 1766) we have collided bunches with highest brightness, i.e. small emittances and high intensities, to explore the achievable beam-beam tune shift for head-on collisions. Different parameters and filling schemes have been used for this experiment and tune shifts above 0.015 have been achieved in single collisions and above 0.030 for two collision points.

  2. eRHIC ring-ring design with head-on beam-beam compensation

    SciTech Connect (OSTI)

    Montag,C.; Blaskiewicz, M.; Pozdeyev, E.; Fischer, W.; MacKay, W. W.

    2009-05-04T23:59:59.000Z

    The luminosity of the eRHIC ring-ring design is limited by the beam-beam effect exerted on the electron beam. Recent simulation studies have shown that the beam-beam limit can be increased by means of an electron lens that compensates the beam-beam effect experienced by the electron beam. This scheme requires proper design of the electron ring, providing the correct betatron phase advance between interaction point and electron lens. We review the performance of the eRHIC ring-ring version and discuss various parameter sets, based on different cooling schemes for the proton/ion beam.

  3. Nufact 2008 The Beta Beam WP Beta beam R&D status

    E-Print Network [OSTI]

    McDonald, Kirk

    Nufact 2008 The Beta Beam WP Nufact 08 1 Beta beam R&D status Elena Wildner, CERN on behalf of the Beta Beam Study Group EURISOL/Euronu #12;Nufact 2008 The Beta Beam WP Nufact08Nufact08 Outline Recall, EURISOL Ion Production Loss Management Improvements New Program, EuroNu 2 #12;Nufact 2008 The Beta Beam WP

  4. Atomic and molecular supernovae

    SciTech Connect (OSTI)

    Liu, W.

    1997-12-01T23:59:59.000Z

    Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

  5. Neutrino mass matrix

    SciTech Connect (OSTI)

    Capps, R.H.; Strobel, E.L.

    1985-07-01T23:59:59.000Z

    It is assumed that the Dirac mass matrix for the neutrinos (..nu../sub e/,..nu../sub ..mu../,..nu../sub tau/) is similar in form to those for the quarks and charged leptons, and that the smallness of the observed ..nu.. masses results from the Gell-Mann--Ramond--Slansky mechanism. It is shown that if certain tentative experimental results concerning the ..nu.. masses and mixing angles are confirmed, significant limitations may be placed on the Majorana mass matrix. The most satisfactory simple assumption concerning the Majorana mass matrix is that it is approximately proportional to the Dirac mass matrix. Some general properties of the Dirac matrices are discussed.

  6. State-to-state dynamics of molecular energy transfer

    SciTech Connect (OSTI)

    Gentry, W.R.; Giese, C.F. [Univ. of Minnesota, Minneapolis (United States)

    1993-12-01T23:59:59.000Z

    The goal of this research program is to elucidate the elementary dynamical mechanisms of vibrational and rotational energy transfer between molecules, at a quantum-state resolved level of detail. Molecular beam techniques are used to isolate individual molecular collisions, and to control the kinetic energy of collision. Lasers are used both to prepare specific quantum states prior to collision by stimulated-emission pumping (SEP), and to measure the distribution of quantum states in the collision products by laser-induced fluorescence (LIF). The results are interpreted in terms of dynamical models, which may be cast in a classical, semiclassical or quantum mechanical framework, as appropriate.

  7. Generate Uniform Transverse Distributed Electron Beam along a Beam Line

    E-Print Network [OSTI]

    Jiao, Y

    2015-01-01T23:59:59.000Z

    It has been reported that transverse distribution shaping can help to further enhance the energy extraction efficiency in a terawatt, tapered X-ray free-electron laser. Thus, methods of creating and keeping almost uniform transverse distributed (UTD) beam within undulators are required. This study shows that a UTD electron beam can be generated within evenly distributed drift sections where undulators can be placed, by means of octupoles and particular optics. A concrete design is presented, and numerical simulations are done to verify the proposed method.

  8. Water in the envelopes and disks around young high-mass stars

    E-Print Network [OSTI]

    Floris van der Tak; Malcolm Walmsley; Fabrice Herpin; Cecilia Ceccarelli

    2005-10-21T23:59:59.000Z

    Single-dish spectra and interferometric maps of (sub)mm lines of H2O-18 and HDO are used to study the chemistry of water in eight regions of high-mass star formation. The spectra indicate HDO excitation temperatures of ~110 K and column densities in an 11'' beam of ~2x10^14 cm^-2 for HDO and ~2x10^17 cm^-2 for H2O, with the N(HDO)/N(H2O) ratio increasing with decreasing temperature. Simultaneous observations of CH3OH and SO2 indicate that 20-50% of the single-dish line flux arises in the molecular outflows of these objects. The outflow contribution to the H2O-18 and HDO emission is estimated to be 10-20%. Radiative transfer models indicate that the water abundance is low (~10^-6) outside a critical radius corresponding to a temperature in the protostellar envelope of ~100 K, and `jumps' to H2O/H2 ~ 10^-4 inside this radius. This value corresponds to the observed abundance of solid water and together with the derived HDO/H2O abundance ratios of ~1/1000 suggests that the origin of the observed water is evaporation of grain mantles. This idea is confirmed in the case of AFGL 2591 by interferometer observations of HDO, H2O-18 and SO2 lines, which reveal compact (~800 AU) emission with a systematic velocity gradient. This size is similar to that of the 1.3 mm continuum towards AFGL 2591, from which we estimate a mass of ~0.8 M0, or ~5% of the mass of the central star. We speculate that we may be observing a circumstellar disk in an almost face-on orientation.

  9. REQUIREMENTS AND GUIDELINES FOR NSLS EXPERIMENTAL BEAM LINE VACUUM SYSTEMS-REVISION B.

    SciTech Connect (OSTI)

    FOERSTER,C.

    1999-05-01T23:59:59.000Z

    Typical beam lines are comprised of an assembly of vacuum valves and shutters referred to as a ''front end'', optical elements to monochromatize, focus and split the photon beam, and an experimental area where a target sample is placed into the photon beam and data from the interaction is detected and recorded. Windows are used to separate sections of beam lines that are not compatible with storage ring ultra high vacuum. Some experimental beam lines share a common vacuum with storage rings. Sections of beam lines are only allowed to vent up to atmospheric pressure using pure nitrogen gas after a vacuum barrier is established to protect ring vacuum. The front end may only be bled up when there is no current in the machine. This is especially true on the VUV storage ring where for most experiments, windows are not used. For the shorter wavelength, more energetic photons of the x-ray ring, beryllium windows are used at various beam line locations so that the monochromator, mirror box or sample chamber may be used in a helium atmosphere or rough vacuum. The window separates ring vacuum from the environment of the downstream beam line components. The stored beam lifetime in the storage rings and the maintenance of desirable reflection properties of optical surfaces depend upon hydrocarbon-free, ultra-high vacuum systems. Storage ring vacuum systems will operate at pressures of {approximately} 1 x 10{sup {minus}10} Torr without beam and {approximately} 1 x 10{sup {minus}9} Torr with beam. Systems are free of hydrocarbons in the sense that no pumps, valves, etc. containing organics are used. Components are all-metal, chemically cleaned and bakeable. To the extent that beam lines share a common vacuum with the storage ring, the same criteria will hold for beam line components. The design philosophy for NSLS beam lines is to use all-metal, hydrocarbon-free front end components and recommend that experimenters use this approach for common vacuum hardware downstream of front ends. O-ring-sealed valves, if used, are not permitted upstream of the monochromator exit aperture. It will be the responsibility of users to demonstrate that their experiment will not degrade the pressure or quality of the storage ring vacuum. As a matter of operating policy, all beam lines will be monitored for prescribed pressure and the contribution of high mass gases to this pressure each time a beam line has been opened to ring vacuum.

  10. Physics Opportunities with Meson Beams

    E-Print Network [OSTI]

    Briscoe, William J; Haberzettl, Helmut; Manley, D Mark; Naruki, Megumi; Strakovsky, Igor I; Swanson, Eric S

    2015-01-01T23:59:59.000Z

    Over the past two decades, meson photo- and electro-production data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even nonexistent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state of-the-art meson-beam facility needs to be constructed. The present paper summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.

  11. Divergence of optical vortex beams

    E-Print Network [OSTI]

    Reddy, Salla Gangi; Prabhakar, Shashi; Anwar, Ali; Banerji, J; Singh, R P

    2015-01-01T23:59:59.000Z

    We show, both theoretically and experimentally, that the propagation of optical vortices in free space can be analysed by using the width ($w(z)$) of the host Gaussian beam and the inner and outer radii of the vortex beam at the source plane ($z=0$) as defined in \\textit{Optics Letters \\textbf{39,} 4364-4367 (2014)}. We also studied the divergence of vortex beams, considered as the rate of change of inner or outer radius with the propagation distance, and found that it varies with the order in the same way as that of the inner and outer radii at zero propagation distance. These results may be useful in designing optical fibers for orbital angular momentum modes that play a crucial role in quantum communication.

  12. EMSL - Mass Spectrometry

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    mass-spectrometry Proteomics Capabilities High resolution and mass accuracy Fourier-transform ion cyclotron resonance (FT-ICR) spectrometers, from 6 Tesla (T) to 15T and 21T in...

  13. DEPARTAMENTO DE BIOMEDICINA MOLECULAR

    E-Print Network [OSTI]

    . Estudio celular y mo- lecular de malaria maternal. rohernan@mail.cinvestav.mx ÍndiceÍndiceÍndice #12 (1994) Cinvestav. Temas de investigación: Estudio molecular y celular de las proteínas involucradas en el patogénesis de la amibiasis y caracterización molecular de la motilidad celular en Entamoeba

  14. Shimmed electron beam welding process

    DOE Patents [OSTI]

    Feng, Ganjiang (Clifton Park, NY); Nowak, Daniel Anthony (Alplaus, NY); Murphy, John Thomas (Niskayuna, NY)

    2002-01-01T23:59:59.000Z

    A modified electron beam welding process effects welding of joints between superalloy materials by inserting a weldable shim in the joint and heating the superalloy materials with an electron beam. The process insures a full penetration of joints with a consistent percentage of filler material and thereby improves fatigue life of the joint by three to four times as compared with the prior art. The process also allows variable shim thickness and joint fit-up gaps to provide increased flexibility for manufacturing when joining complex airfoil structures and the like.

  15. Finding beam focus errors automatically

    SciTech Connect (OSTI)

    Lee, M.J.; Clearwater, S.H.; Kleban, S.D.

    1987-01-01T23:59:59.000Z

    An automated method for finding beam focus errors using an optimization program called COMFORT-PLUS. The steps involved in finding the correction factors using COMFORT-PLUS has been used to find the beam focus errors for two damping rings at the SLAC Linear Collider. The program is to be used as an off-line program to analyze actual measured data for any SLC system. A limitation on the application of this procedure is found to be that it depends on the magnitude of the machine errors. Another is that the program is not totally automated since the user must decide a priori where to look for errors. (LEW)

  16. Elbow mass flow meter

    DOE Patents [OSTI]

    McFarland, Andrew R. (College Station, TX); Rodgers, John C. (Santa Fe, NM); Ortiz, Carlos A. (Bryan, TX); Nelson, David C. (Santa Fe, NM)

    1994-01-01T23:59:59.000Z

    Elbow mass flow meter. The present invention includes a combination of an elbow pressure drop generator and a shunt-type mass flow sensor for providing an output which gives the mass flow rate of a gas that is nearly independent of the density of the gas. For air, the output is also approximately independent of humidity.

  17. Molecular Hydrogen in Infrared Cirrus

    E-Print Network [OSTI]

    Kristen Gillmon; J. Michael Shull

    2005-07-25T23:59:59.000Z

    We combine data from our recent FUSE survey of interstellar molecular hydrogen absorption toward 50 high-latitude AGN with COBE-corrected IRAS 100 micron emission maps to study the correlation of infrared cirrus with H2. A plot of the H2 column density vs. IR cirrus intensity shows the same transition in molecular fraction, f_H2, as seen with total hydrogen column density, N_H. This transition is usually attributed to H2 self-shielding, and it suggests that many diffuse cirrus clouds contain H2 in significant fractions, f_H2 = 1-30%. These clouds cover approximately 50% of the northern sky at latitudes b > 30 degrees, at temperature-corrected 100 micron intensities D_100 > 1.5 MJy/sr. The sheetlike cirrus clouds, with hydrogen densities n_H > 30 cm^-3, may be compressed by dynamical processes at the disk-halo interface, and they are conducive to H2 formation on grain surfaces. Exploiting the correlation between N(H2) and 100 micron intensity, we estimate that cirrus clouds at b > 30 contain approximately 3000 M_sun in H2. Extrapolated over the inner Milky Way, the cirrus may contain 10^7 M_sun of H2 and 10^8 M_sun in total gas mass. If elevated to 100 pc, their gravitational potential energy is ~10^53 erg.

  18. Transverse beam shape measurements of intense proton beams using optical transition radiation

    SciTech Connect (OSTI)

    Scarpine, Victor E.; /Fermilab

    2012-03-01T23:59:59.000Z

    A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

  19. Thermographic calorimetry of the neutral beam injectors heating beams at TJ-II

    SciTech Connect (OSTI)

    Fuentes, C.; Liniers, M.; Guasp, J.; Doncel, J.; Botija, J.; Wolfers, G.; Alonso, J.; Acedo, M.; Sanchez, E.; Marcon, G.; Weber, M.; Carrasco, R.; Sarasola, X.; Zurro, B.; Tera, J. [Laboratorio Nacional de Fusion/Asociacion EURATOM-CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain)

    2006-10-15T23:59:59.000Z

    A new beam diagnostic based on infrared thermography has been developed for the neutral beam injectors of the stellarator TJ-II. A highly anisotropic movable target intercepts the beam at its entrance into the stellarator. The thermal print of the beam is captured with a high resolution infrared camera. The infrared images of the target can be translated, with the appropriate analysis, into power density patterns of the beam. The system is calibrated in situ with two thermocouples adiabatically mounted in the target. The two-dimensional beam power density distribution can be accurately characterized allowing beam optimization with respect to the different parameters involved in the beam formation and transport.

  20. Circumbinary Molecular Rings Around Young Stars in Orion

    E-Print Network [OSTI]

    Luis A. Zapata; Paul T. P. Ho; Luis F. Rodriguez; Peter Schilke; Stan Kurtz

    2007-07-09T23:59:59.000Z

    We present high angular resolution 1.3 mm continuum, methyl cyanide molecular line, and 7 mm continuum observations made with the Submillimeter Array and the Very Large Array, toward the most highly obscured and southern part of the massive star forming region OMC1S located behind the Orion Nebula. We find two flattened and rotating molecular structures with sizes of a few hundred astronomical units suggestive of circumbinary molecular rings produced by the presence of two stars with very compact circumstellar disks with sizes and separations of about 50 AU, associated with the young stellar objects 139-409 and 134-411. Furthermore, these two circumbinary rotating rings are related to two compact and bright {\\it hot molecular cores}. The dynamic mass of the binary systems obtained from our data are $\\geq$ 4 M$_\\odot$ for 139-409 and $\\geq$ 0.5 M$_\\odot$ for 134-411. This result supports the idea that intermediate-mass stars will form through {\\it circumstellar disks} and jets/outflows, as the low mass stars do. Furthermore, when intermediate-mass stars are in multiple systems they seem to form a circumbinary ring similar to those seen in young, multiple low-mass systems (e.g., GG Tau and UY Aur).

  1. The study of colliding molecular clumps evolution

    E-Print Network [OSTI]

    S. B. Vinogradov; P. Berczik

    2007-01-12T23:59:59.000Z

    The results of study of the gravitational fragmentation in the interstellar medium (ISM) by clump-clump collisions are presented. We suggest, that collision of clumps, that are subparts of Giant Molecular Clouds (GMC) may be on of the basic mechanism, which result to ISM fragmentation and define the dynamical as well as statistical characteristics (e.g. the mass spectra) of protostellar condensation. In the present paper, we describe our 3D SPH-modeling, in isothermal approximation, of supersonic collisions of two identical clumps with a few variants of initial impact parameters ($\\beta$), that cover the wide range. Our results shown, that at all $\\beta$ in system began intensive fragmentation. The resulting fragments mass function depend from initial impact parameter. The obtained mass spectra have the slopes in a good enough agreement with observational data for our Galaxy -- especially for large impact parameters, which are more realistic as for large clumps ensembles.

  2. Site control technique for quantum dots using electron beam induced deposition

    SciTech Connect (OSTI)

    Iizuka, Kanji; Jung, JaeHun; Yokota, Hiroshi [Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro, Minami-saitama, Saitama 3458501 (Japan)

    2014-05-15T23:59:59.000Z

    To develop simple and high throughput sit definition technique for quantum dots (QDs), the electron beam induced deposition (EBID) method was used as desorption guide of phosphorus atoms form InP substrate. As the results one or a few indium (In) droplets (DLs) were created in the carbon grid pattern by thermal annealing at a temperature of 450°C for 10 min in the ultra high vacuum condition. The size of In DLs was larger than QDs, but arsenide DLs by molecular beam in growth chamber emitted wavelength of 1.028?m at 50K by photoluminescence measurement.

  3. High energy laser beam dump

    DOE Patents [OSTI]

    Halpin, John (Tracy, CA)

    2004-09-14T23:59:59.000Z

    The laser beam dump is positioned in a housing. An absorbing glass plate means is operatively connected to the housing. A heat sync means for extracting heat from the absorbing glass plate means is operatively connected to the housing and operatively connected to the absorbing glass plate means.

  4. Relativistic atomic beam spectroscopy II

    SciTech Connect (OSTI)

    NONE

    1991-12-31T23:59:59.000Z

    We are requesting support for a postdoctoral person to participate in H{sup -} studies at Los Alamos. In addition, we are requesting funding for a state-of-the-art YAG laser system that would allow us to obtain data at three times our present rate with improved beam quality.

  5. Direct analysis of samples by mass spectrometry: From elements to bio-molecules using laser ablation inductively couple plasma mass spectrometry and laser desorption/ionization mass spectrometry

    SciTech Connect (OSTI)

    Perdian, David C.

    2009-08-19T23:59:59.000Z

    Mass spectrometric methods that are able to analyze solid samples or biological materials with little or no sample preparation are invaluable to science as well as society. Fundamental research that has discovered experimental and instrumental parameters that inhibit fractionation effects that occur during the quantification of elemental species in solid samples by laser ablation inductively coupled plasma mass spectrometry is described. Research that determines the effectiveness of novel laser desorption/ionization mass spectrometric methods for the molecular analysis of biological tissues at atmospheric pressure and at high spatial resolution is also described. A spatial resolution is achieved that is able to analyze samples at the single cell level.

  6. Bunch length effects in the beam-beam compensation with an electron lens

    SciTech Connect (OSTI)

    Fischer, W.; Luo, Y.; Montag, C.

    2010-02-25T23:59:59.000Z

    Electron lenses for the head-on beam-beam compensation are under construction at the Relativistic Heavy Ion Collider. The bunch length is of the same order as the {beta}-function at the interaction point, and a proton passing through another proton bunch experiences a substantial phase shift which modifies the beam-beam interaction. We review the effect of the bunch length in the single pass beam-beam interaction, apply the same analysis to a proton passing through a long electron lens, and study the single pass beam-beam compensation with long bunches. We also discuss the beam-beam compensation of the electron beam in an electron-ion collider ring.

  7. antinucleon beams: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    interaction of fields induced by the beam with their environment. Beam current transformers as well as beam position monitors are based on this principle. The signals induced...

  8. automatic beam alignment: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    interaction of fields induced by the beam with their environment. Beam current transformers as well as beam position monitors are based on this principle. The signals induced...

  9. accidental beam loss: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    interaction of fields induced by the beam with their environment. Beam current transformers as well as beam position monitors are based on this principle. The signals induced...

  10. antiparticle beams: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    interaction of fields induced by the beam with their environment. Beam current transformers as well as beam position monitors are based on this principle. The signals induced...

  11. accelerating beam stability: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    particle beams (beam intercepting devices BIDs). For the design of BIDs, the increasing heat load onto these devices due to energetic and focused beams and - in most cases -...

  12. accelerated oxygen-14 beam: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    particle beams (beam intercepting devices BIDs). For the design of BIDs, the increasing heat load onto these devices due to energetic and focused beams and - in most cases -...

  13. accelerator school beam: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    particle beams (beam intercepting devices BIDs). For the design of BIDs, the increasing heat load onto these devices due to energetic and focused beams and - in most cases -...

  14. Combining tissue-phantom ratios to provide a beam-quality specifier for flattening filter free photon beams

    SciTech Connect (OSTI)

    Dalaryd, Mårten, E-mail: Marten.Dalaryd@med.lu.se; Knöös, Tommy [Department of Clinical Sciences, Medical Radiation Physics, Lund University, P.O. Box 117, Lund SE-221 00, Sweden and Radiation Physics, Skåne University Hospital, Lund SE-221 85 (Sweden); Ceberg, Crister [Department of Clinical Sciences, Medical Radiation Physics, Lund University, P.O. Box 117, Lund SE-221 00 (Sweden)

    2014-11-01T23:59:59.000Z

    Purpose: There are currently several commercially available radiotherapy treatment units without a flattening filter in the beam line. Unflattened photon beams have an energy and lateral fluence distribution that is different from conventional beams and, thus, their attenuation properties differ. As a consequence, for flattening filter free (FFF) beams, the relationship between the beam-quality specifier TPR{sub 20,10} and the Spencer–Attix restricted water-to-air mass collision stopping-power ratios, (L{sup -}/?){sub air}{sup water}, may have to be refined in order to be used with equivalent accuracy as for beams with a flattening filter. The purpose of this work was twofold. First, to study the relationship between TPR{sub 20,10} and (L{sup -}/?){sub air}{sup water} for FFF beams, where the flattening filter has been replaced by a metal plate as in most clinical FFF beams. Second, to investigate the potential of increasing the accuracy in determining (L{sup -}/?){sub air}{sup water} by adding another beam-quality metric, TPR{sub 10,5}. The relationship between (L{sup -}/?){sub air}{sup water} and %dd(10){sub x} for beams with and without a flattening filter was also included in this study. Methods: A total of 24 realistic photon beams (10 with and 14 without a flattening filter) from three different treatment units have been used to calculate (L{sup -}/?){sub air}{sup water}, TPR{sub 20,10}, and TPR{sub 10,5} using the EGSnrc Monte Carlo package. The relationship between (L{sup -}/?){sub air}{sup water} and the dual beam-quality specifier TPR{sub 20,10} and TPR{sub 10,5} was described by a simple bilinear equation. The relationship between the photon beam-quality specifier %dd(10){sub x} used in the AAPM’s TG-51 dosimetry protocol and (L{sup -}/?){sub air}{sup water} was also investigated for the beams used in this study, by calculating the photon component of the percentage depth dose at 10 cm depth with SSD 100 cm. Results: The calculated (L{sup -}/?){sub air}{sup water} for beams without a flattening filter was 0.3% lower, on average, than for beams with a flattening filter and comparable TPR{sub 20,10}. Using the relationship in IAEA, TRS-398 resulted in a root mean square deviation (RMSD) of 0.0028 with a maximum deviation of 0.0043 (0.39%) from Monte Carlo calculated values. For all beams in this study, the RMSD between the proposed model and the Monte Carlo calculated values was 0.0006 with a maximum deviation of 0.0013 (0.1%). Using an earlier proposed relationship [Xiong and Rogers, Med. Phys. 35, 2104–2109 (2008)] between %dd(10){sub x} and (L{sup -}/?){sub air}{sup water} gave a RMSD of 0.0018 with a maximum deviation of 0.0029 (0.26%) for all beams in this study (compared to RMSD 0.0015 and a maximum deviation of 0.0048 (0.47%) for the relationship used in AAPM TG-51 published by Almond et al. [Med. Phys. 26, 1847–1870 (1999)]). Conclusions: Using TPR{sub 20,10} as a beam-quality specifier, for the flattening filter free beams used in this study, gave a maximum difference of 0.39% between (L{sup -}/?){sub air}{sup water} predicted using IAEA TRS-398 and Monte Carlo calculations. An additional parameter for determining (L{sup -}/?){sub air}{sup water} has been presented. This parameter is easy to measure; it requires only an additional dose measurement at 5 cm depth with SSD 95 cm, and provides information for accurate determination of the (L{sup -}/?){sub air}{sup water} ratio for beams both with and without a flattening filter at the investigated energies.

  15. Transport of elliptic intense charged -particle beams

    E-Print Network [OSTI]

    Zhou, J. (Jing), 1978-

    2006-01-01T23:59:59.000Z

    The transport theory of high-intensity elliptic charged-particle beams is presented. In particular, the halo formation and beam loss problem associated with the high space charge and small-aperture structure is addressed, ...

  16. Neutral particle beam sensing and steering

    DOE Patents [OSTI]

    Maier, II, William B. (Los Alamos, NM); Cobb, Donald D. (Los Alamos, NM); Robiscoe, Richard T. (Los Alamos, NM)

    1991-01-01T23:59:59.000Z

    The direction of a neutral particle beam (NPB) is determined by detecting Ly.alpha. radiation emitted during motional quenching of excited H(2S) atoms in the beam during movement of the atoms through a magnetic field. At least one detector is placed adjacent the beam exit to define an optical axis that intercepts the beam at a viewing angle to include a volume generating a selected number of photons for detection. The detection system includes a lens having an area that is small relative to the NPB area and a pixel array located in the focal plane of the lens. The lens viewing angle and area pixel array are selected to optimize the beam tilt sensitivity. In one embodiment, two detectors are placed coplanar with the beam axis to generate a difference signal that is insensitive to beam variations other than beam tilt.

  17. On Gaussian Beams Described by Jacobi's Equation

    E-Print Network [OSTI]

    Smith, Steven T.

    Gaussian beams describe the amplitude and phase of rays and are widely used to model acoustic propagation. This paper describes four new results in the theory of Gaussian beams. (1) A new version of the ?ervený equations ...

  18. Autogenerator of beams of charged particles

    DOE Patents [OSTI]

    Adler, R.J.; Mazarakis, M.G.; Miller, R.M.; Shope, S.L.; Smith, D.L.

    1983-10-31T23:59:59.000Z

    An autogenerating apparatus provides secondary intense relativistic current beam pulses in response to an injected beam pulse. One or more electromagnetic energy storage devices are provided in conjunction with gaps along a beam propagation path for the injected beam pulse. For injected beam pulses which are no longer than double the transit time of electromagnetic waves within the storage devices (which may be resonant cavities), distinct secondary beam pulses are generated by each of the energy storage devices. The beam propagation path, together with the one or more gaps provided therein, operates as a pulse forming transmission line cavity, in which the separate cavities associated with the gaps provide delays for electromagnetic waves generated at the gaps. After doubly traversing the cavity, the electromagnetic waves cause the gap to generate the secondary beam pulses, which are thus delayed by a time interval equal to the double transit time for the induced wave within the cavity.

  19. Autogenerator of beams of charged particles

    DOE Patents [OSTI]

    Adler, Richard J. (Albuquerque, NM); Mazarakis, Michael G. (Albuquerque, NM); Miller, Robert B. (Albuquerque, NM); Shope, Steven L. (Albuquerque, NM); Smith, David L. (Albuquerque, NM)

    1986-01-01T23:59:59.000Z

    An autogenerating apparatus provides secondary intense relativistic current beam pulses in response to an injected beam pulse. One or more electromagnetic energy storage devices are provided in conjunction with gaps along a beam propagation path for the injected beam pulse. For injected beam pulses which are no longer than double the transit time of electromagnetic waves within the storage devices (which may be resonant cavities), distinct secondary beam pulses are generated by each of the energy storage devices. The beam propagation path, together with the one or more gaps provided therein, operates as a pulse forming transmission line cavity, in which the separate cavities associated with the gaps provide delays for electromagnetic waves generated at the gaps. After doubly traversing the cavity, the electromagnetic waves cause the gap to generate the secondary beam pulses, which are thus delayed by a time interval equal to the double transit time for the induced wave within the cavity.

  20. Molecular heat pump

    E-Print Network [OSTI]

    Dvira Segal; Abraham Nitzan

    2005-10-11T23:59:59.000Z

    We propose a novel molecular device that pumps heat against a thermal gradient. The system consists of a molecular element connecting two thermal reservoirs that are characterized by different spectral properties. The pumping action is achieved by applying an external force that periodically modulates molecular levels. This modulation affects periodic oscillations of the internal temperature of the molecule and the strength of its coupling to each reservoir resulting in a net heat flow in the desired direction. The heat flow is examined in the slow and fast modulation limits and for different modulation waveforms, thus making it possible to optimize the device performance.

  1. Mass Spectrometer | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of strong brown carbon chromophores. Citation: Laskin J, A Laskin, S Nizkorodov, PJ Roach, PA Eckert, MK Gilles, B Wang, HJ Lee, and Q Hu.2014."Molecular Selectivity of Brown...

  2. Apparatus and method of determining molecular weight of large molecules

    DOE Patents [OSTI]

    Fuerstenau, S.; Benner, W.H.; Madden, N.M.; Searles, W.

    1998-06-23T23:59:59.000Z

    A mass spectrometer determines the mass of multiply charged high molecular weight molecules. This spectrometer utilizes an ion detector which is capable of simultaneously measuring the charge z and transit time of a single ion as it passes through the detector. From this transit time, the velocity of the single ion may then be derived, thus providing the mass-to-charge ratio m/z for a single ion which has been accelerated through a known potential. Given z and m/z, the mass m of the single ion can then be calculated. Electrospray ions with masses in excess of 1 MDa and charge numbers greater than 425 e{sup {minus}} are readily detected. The on-axis single ion detection configuration enables a duty cycle of nearly 100% and extends the practical application of electrospray mass spectrometry to the analysis of very large molecules with relatively inexpensive instrumentation. 14 figs.

  3. Apparatus and method of determining molecular weight of large molecules

    DOE Patents [OSTI]

    Fuerstenau, Stephen (Montrose, CA); Benner, W. Henry (Danville, CA); Madden, Norman (Livermore, CA); Searles, William (Fremont, CA)

    1998-01-01T23:59:59.000Z

    A mass spectrometer determines the mass of multiply charged high molecular weight molecules. This spectrometer utilizes an ion detector which is capable of simultaneously measuring the charge z and transit time of a single ion as it passes through the detector. From this transit time, the velocity of the single ion may then be derived, thus providing the mass-to-charge ratio m/z for a single ion which has been accelerated through a known potential. Given z and m/z, the mass m of the single ion can then be calculated. Electrospray ions with masses in excess of 1 MDa and charge numbers greater than 425 e.sup.- are readily detected. The on-axis single ion detection configuration enables a duty cycle of nearly 100% and extends the practical application of electrospray mass spectrometry to the analysis of very large molecules with relatively inexpensive instrumentation.

  4. Maskless, resistless ion beam lithography

    SciTech Connect (OSTI)

    Ji, Qing

    2003-03-10T23:59:59.000Z

    As the dimensions of semiconductor devices are scaled down, in order to achieve higher levels of integration, optical lithography will no longer be sufficient for the needs of the semiconductor industry. Alternative next-generation lithography (NGL) approaches, such as extreme ultra-violet (EUV), X-ray, electron-beam, and ion projection lithography face some challenging issues with complicated mask technology and low throughput. Among the four major alternative NGL approaches, ion beam lithography is the only one that can provide both maskless and resistless patterning. As such, it can potentially make nano-fabrication much simpler. This thesis investigates a focused ion beam system for maskless, resistless patterning that can be made practical for high-volume production. In order to achieve maskless, resistless patterning, the ion source must be able to produce a variety of ion species. The compact FIB system being developed uses a multicusp plasma ion source, which can generate ion beams of various elements, such as O{sub 2}{sup +}, BF{sub 2}{sup +}, P{sup +} etc., for surface modification and doping applications. With optimized source condition, around 85% of BF{sub 2}{sup +}, over 90% of O{sub 2}{sup +} and P{sup +} have been achieved. The brightness of the multicusp-plasma ion source is a key issue for its application to maskless ion beam lithography. It can be substantially improved by optimizing the source configuration and extractor geometry. Measured brightness of 2 keV He{sup +} beam is as high as 440 A/cm{sup 2} {center_dot} Sr, which represents a 30x improvement over prior work. Direct patterning of Si thin film using a focused O{sub 2}{sup +} ion beam has been investigated. A thin surface oxide film can be selectively formed using 3 keV O{sub 2}{sup +} ions with the dose of 10{sup 15} cm{sup -2}. The oxide can then serve as a hard mask for patterning of the Si film. The process flow and the experimental results for directly patterned poly-Si features are presented. The formation of shallow pn-junctions in bulk silicon wafers by scanning focused P{sup +} beam implantation at 5 keV is also presented. With implantation dose of around 10{sup 16} cm{sup -2}, the electron concentration is about 2.5 x 10{sup 18} cm{sup -3} and electron mobility is around 200 cm{sup 2}/V{center_dot}s. To demonstrate the suitability of scanning FIB lithography for the manufacture of integrated circuit devices, SOI MOSFET fabrication using the maskless, resistless ion beam lithography is demonstrated. An array of microcolumns can be built by stacking multi-aperture electrode and insulator layers. Because the multicusp plasma source can achieve uniform ion density over a large area, it can be used in conjunction with the array of microcolumns, for massively parallel FIB processing to achieve reasonable exposure throughput.

  5. High Gradient Two-Beam Electron Accelerator

    SciTech Connect (OSTI)

    Jiang, Y. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Kazakov, S. Yu. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Kuzikov, S. V. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Institute of Applied Physics, Nizhny Novgorod, 603600 (Russian Federation); Hirshfield, J. L. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States)

    2010-11-04T23:59:59.000Z

    A high-gradient two-beam electron accelerator structure using detuned cavities is described. A self-consistent theory based on a circuit model is presented to calculate idealized acceleration gradient, transformer ratio, and efficiency for energy transfer from the drive beam to the accelerated beam. Experimental efforts are being carried out to demonstrate this acceleration concept.

  6. Laser Telecommunication timeLaser beam

    E-Print Network [OSTI]

    La Rosa, Andres H.

    Laser Telecommunication Experiment Laser time Laser beam intensity timeLaser beam Laser battery Laser connected to a circuit without a modulator. Bottom graph illustrates what happen when a modulating signal is superimposed to the DC voltage driving the laser Laser beam intensity DC Input voltage DC

  7. Nondestructive Damage Detection in General Beams 

    E-Print Network [OSTI]

    Dincal, Selcuk

    2010-12-08T23:59:59.000Z

    Representation of the First Damage Case on the Finite Element Mesh of the Slender Beam ...................................................... 41 Figure 3.12 Schematic Representation of the Second Damage Case on the Finite Element Mesh... of the Slender Beam ...................................................... 42 Figure 3.13 Schematic Representation of the Third Damage Case on the Finite Element Mesh of the Slender Beam ...................................................... 44...

  8. JET neutral beam power upgrade Introduction

    E-Print Network [OSTI]

    JET neutral beam power upgrade Introduction A tokamak is a complex assembly, a system of systems the challenging requirements that fusion demands. The neutral beam heating system and its upgrade for the JET systems) are the main plasma heating scheme on fusion devices such as JET and ITER. The JET neutral beam

  9. Beam heat load in superconducting wigglers

    E-Print Network [OSTI]

    Casalbuoni, S

    2013-01-01T23:59:59.000Z

    The beam heat load is a fundamental input parameter for the design of superconducting wigglers since it is needed to specify the cooling power. In this presentation I will review the possible beam heat load sources and the measurements of beam heat load performed and planned onto the cold vacuum chambers installed at different synchrotron light sources.

  10. Lateral stability of long precast concrete beams

    E-Print Network [OSTI]

    Burgoyne, Chris

    buckling L length of beam vx lateral de¯ection measured in the minor- axis direction (which rotates with yLateral stability of long precast concrete beams T. J. Stratford, BA, BEng, and C. J. Burgoyne, BA, making them more susceptible to buckling failure. This paper shows that once the beam is positioned

  11. Results of long range beam-beam studies and observations during operation in the LHC

    E-Print Network [OSTI]

    Alemany, R; Buffat, X; Calaga, R; Fitterer, M; Giachino, R; Hemelsoet, GH; Herr, W; Papotti, G; Pieloni, T; Poyer, M; Schaumann, M; Trad, G; Wollmann, D

    2011-01-01T23:59:59.000Z

    We studied possible limitations due to the long range beam-beam effects in the LHC. With a larger number of bunches and collisions in all interaction points, we have reduced the crossing angles to enhance long range beam-beam effects to evaluate their influence on dynamic aperture and losses. Experience from operation with reduced separation was analysed and provides additional evidence.

  12. Small system for tritium accelerator mass spectrometry

    DOE Patents [OSTI]

    Roberts, M.L.; Davis, J.C.

    1993-02-23T23:59:59.000Z

    Apparatus for ionizing and accelerating a sample containing isotopes of hydrogen and detecting the ratios of hydrogen isotopes contained in the sample is disclosed. An ion source generates a substantially linear ion beam including ions of tritium from the sample. A radio-frequency quadrupole accelerator is directly coupled to and axially aligned with the source at an angle of substantially zero degrees. The accelerator accelerates species of the sample having different mass to different energy levels along the same axis as the ion beam. A spectrometer is used to detect the concentration of tritium ions in the sample. In one form of the invention, an energy loss spectrometer is used which includes a foil to block the passage of hydrogen, deuterium and [sup 3]He ions, and a surface barrier or scintillation detector to detect the concentration of tritium ions. In another form of the invention, a combined momentum/energy loss spectrometer is used which includes a magnet to separate the ion beams, with Faraday cups to measure the hydrogen and deuterium and a surface barrier or scintillation detector for the tritium ions.

  13. Small system for tritium accelerator mass spectrometry

    DOE Patents [OSTI]

    Roberts, Mark L. (Livermore, CA); Davis, Jay C. (Livermore, CA)

    1993-01-01T23:59:59.000Z

    Apparatus for ionizing and accelerating a sample containing isotopes of hydrogen and detecting the ratios of hydrogen isotopes contained in the sample is disclosed. An ion source generates a substantially linear ion beam including ions of tritium from the sample. A radio-frequency quadrupole accelerator is directly coupled to and axially aligned with the source at an angle of substantially zero degrees. The accelerator accelerates species of the sample having different mass to different energy levels along the same axis as the ion beam. A spectrometer is used to detect the concentration of tritium ions in the sample. In one form of the invention, an energy loss spectrometer is used which includes a foil to block the passage of hydrogen, deuterium and .sup.3 He ions, and a surface barrier or scintillation detector to detect the concentration of tritium ions. In another form of the invention, a combined momentum/energy loss spectrometer is used which includes a magnet to separate the ion beams, with Faraday cups to measure the hydrogen and deuterium and a surface barrier or scintillation detector for the tritium ions.

  14. Top quark mass measurements

    SciTech Connect (OSTI)

    Hill, Christopher S.; /UC, Santa Barbara

    2004-12-01T23:59:59.000Z

    The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.

  15. MassMass transfer andtransfer and MassMass transfer andtransfer and

    E-Print Network [OSTI]

    Zevenhoven, Ron

    Heat conductivity T'1 Heat flux h" (W/m2), local and overall heat transfer coeffients h1 Heat transfer coefficientcoefficient /1/1 Mass flow species A:interface a p A = A mol/s M f1 (L) 2 (G) Mass transfer rate per area: A = A/a = "A mol/(m2·s) 1 (L) 2 (G) xi C1.i M t f ffi i t k x C y 1.i AA !!! Mass transfer coefficients

  16. Mass and Heat Recovery

    E-Print Network [OSTI]

    Hindawai, S. M.

    2010-01-01T23:59:59.000Z

    - 1 - MASS AND HEAT RECOVERY SYSTEM SALAH MAHMOUD HINDAWI DIRECTOR HINDAWI FOR ENGINEERING SERVICES & CONTRACTING NEW DAMIETTA , EGYPT ABSTRACT : In the last few years heat recovery was under spot . and in air conditioning fields... ) as a heat recovery . and I use the water as a mass recovery . The source of mass and heat recovery is the condensate water which we were dispose and connect it to the drain lines . THE BENEFIT OF THIS SYSTEM ARE : 1) Using the heat energy from...

  17. Asymptotic Analysis of Cooperative Molecular Motor System

    E-Print Network [OSTI]

    Durrett, Richard

    Mesoscale Model for Collections of Molecular Motors Stochastic Asymptotic Techniques #12;Molecular Motors

  18. First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE

    SciTech Connect (OSTI)

    Schmidt, H. T.; Thomas, R. D.; Gatchell, M.; Rosen, S.; Reinhed, P.; Loefgren, P.; Braennholm, L.; Blom, M.; Bjoerkhage, M.; Baeckstroem, E.; Alexander, J. D.; Leontein, S.; Zettergren, H.; Liljeby, L.; Kaellberg, A.; Simonsson, A.; Hellberg, F.; Mannervik, S.; Larsson, M.; Geppert, W. D. [Department of Physics, Stockholm University, SE-10691 Stockholm (Sweden); and others

    2013-05-15T23:59:59.000Z

    We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (C{sub n}{sup -}, n= 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C{sub 2}{sup -} molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s {+-} 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10{sup -14} mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.

  19. Electron beam diagnostic for space charge measurement of an ion beam

    SciTech Connect (OSTI)

    Roy, Prabir K.; Yu, Simon S.; Henestroza, Enrique; Eylon, Shmuel; Shuman, Derek B.; Ludvig, Jozsef; Bieniosek, Frank M.; Waldron, William L.; Greenway, Wayne G.; Vanecek, David L.; Hannink, Ryan; Amezcua, Monserrat

    2004-09-25T23:59:59.000Z

    A non-perturbing electron beam diagnostic system for measuring the charge distribution of an ion beam is developed for Heavy Ion Fusion (HIF) beam physics studies. Conventional diagnostics require temporary insertion of sensors into the beam, but such diagnostics stop the beam, or significantly alter its properties. In this diagnostic a low energy, low current electron beam is swept transversely across the ion beam; the measured electron beam deflection is used to infer the charge density profile of the ion beam. The initial application of this diagnostic is to the Neutralized Transport Experiment (NTX), which is exploring the physics of space-charge-dominated beam focusing onto a small spot using a neutralizing plasma. Design and development of this diagnostic and performance with the NTX ion beamline is presented.

  20. Stability of Single Particle Motion with Head-On Beam-Beam Compensation in the RHIC

    SciTech Connect (OSTI)

    Luo,Y.; Fischer, W.; Abreu, N.

    2008-05-01T23:59:59.000Z

    To compensate the large tune shift and tune spread generated by the head-on beam-beam interactions in the polarized proton run in the Relativistic Heavy Ion Collider (RHIC), we proposed a low energy electron beam with a Gaussian transverse profiles to collide head-on with the proton beam. In this article, with a weak-strong beam-beam interaction model, we investigate the stability of single particle motion in the presence of head-on beam-beam compensation. Tune footprints, tune diffusion, Lyapunov exponents, and 10{sup 6} turn dynamic apertures are calculated and compared between the cases without and with beam-beam compensation. A tune scan is performed and the possibility of increasing the bunch intensity is studied. The cause of tune footprint foldings is discussed, and the tune diffusion and Lyapunov exponent analysis are compared.

  1. Nuclear Masses in Astrophysics

    E-Print Network [OSTI]

    Christine Weber; Klaus Blaum; Hendrik Schatz

    2008-12-09T23:59:59.000Z

    Among all nuclear ground-state properties, atomic masses are highly specific for each particular combination of N and Z and the data obtained apply to a variety of physics topics. One of the most crucial questions to be addressed in mass spectrometry of unstable radionuclides is the one of understanding the processes of element formation in the Universe. To this end, accurate atomic mass values of a large number of exotic nuclei participating in nucleosynthesis are among the key input data in large-scale reaction network calculations. In this paper, a review on the latest achievements in mass spectrometry for nuclear astrophysics is given.

  2. Multiple mass solvers

    E-Print Network [OSTI]

    B. Jegerlehner

    1997-08-29T23:59:59.000Z

    We present a general method to construct multiple mass solvers from standard algorithms. As an example, the BiCGstab-M algorithm is derived.

  3. EMSL - Mass Spectrometer

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    MS) with high mass resolution (m&61636;m100,000). Solvent mixtures of acetonitrilewater and acetonitriletoluene were used to extract and ionize polar and non-polar...

  4. Summary of session 3 on synchrotron radiation and beam dynamics

    SciTech Connect (OSTI)

    Shiltsev, V.; /Fermilab; Metral, E.; /CERN

    2010-12-01T23:59:59.000Z

    We summarize presentations, discussions and general conclusions of the Workshop session on 'Beam Dynamics Issues'. Major subjects include effects due to synchrotron radiation (SR), cryogenic loads, electron cloud, impedances, intra-beam scattering (IBS) and beam-beam interactions.

  5. A dynamical definition of quasibound molecular clusters Sarah A. Harris and Ian J. Forda)

    E-Print Network [OSTI]

    Ford, Ian

    A dynamical definition of quasibound molecular clusters Sarah A. Harris and Ian J. Forda of a quasibound cluster are identified through a retrospective dynamical definition. The trajectory of a molecular is satisfied, however, at the instant that the energy of the departing molecule in the center of mass frame

  6. Beam intensity upgrade at Fermilab

    SciTech Connect (OSTI)

    Marchionni, A.; /Fermilab

    2006-07-01T23:59:59.000Z

    The performance of the Fermilab proton accelerator complex is reviewed. The coming into operation of the NuMI neutrino line and the implementation of slip-stacking to increase the anti-proton production rate has pushed the total beam intensity in the Main Injector up to {approx} 3 x 10{sup 13} protons/pulse. A maximum beam power of 270 kW has been delivered on the NuMI target during the first year of operation. A plan is in place to increase it to 350 kW, in parallel with the operation of the Collider program. As more machines of the Fermilab complex become available with the termination of the Collider operation, a set of upgrades are being planned to reach first 700 kW and then 1.2 MW by reducing the Main Injector cycle time and by implementing proton stacking.

  7. Oxygen ion-beam microlithography

    DOE Patents [OSTI]

    Tsuo, Y. Simon (Lakewood, CO)

    1991-01-01T23:59:59.000Z

    A method of providing and developing a resist on a substrate for constructing integrated circuit (IC) chips includes the following steps: of depositing a thin film of amorphous silicon or hydrogenated amorphous silicon on the substrate and exposing portions of the amorphous silicon to low-energy oxygen ion beams to oxidize the amorphous silicon at those selected portions. The nonoxidized portions are then removed by etching with RF-excited hydrogen plasma. Components of the IC chip can then be constructed through the removed portions of the resist. The entire process can be performed in an in-line vacuum production system having several vacuum chambers. Nitrogen or carbon ion beams can also be used.

  8. Oxygen ion-beam microlithography

    DOE Patents [OSTI]

    Tsuo, Y.S.

    1991-08-20T23:59:59.000Z

    A method of providing and developing a resist on a substrate for constructing integrated circuit (IC) chips includes the following steps: of depositing a thin film of amorphous silicon or hydrogenated amorphous silicon on the substrate and exposing portions of the amorphous silicon to low-energy oxygen ion beams to oxidize the amorphous silicon at those selected portions. The nonoxidized portions are then removed by etching with RF-excited hydrogen plasma. Components of the IC chip can then be constructed through the removed portions of the resist. The entire process can be performed in an in-line vacuum production system having several vacuum chambers. Nitrogen or carbon ion beams can also be used. 5 figures.

  9. The MICE Muon Beam Line

    SciTech Connect (OSTI)

    Apollonio, Marco [High Energy Physics Group, Department of Physics, Imperial College London SW7 2AZ (United Kingdom)

    2011-10-06T23:59:59.000Z

    In the Muon Ionization Cooling Experiment (MICE) at RAL, muons are produced and transported in a dedicated beam line connecting the production point (target) to the cooling channel. We discuss the main features of the beamline, meant to provide muons with momenta between 140 MeV/c and 240 MeV/c and emittances up to 10 mm rad, which is accomplished by means of a diffuser. Matching procedures to the MICE cooling channel are also described. In summer 2010 we performed an intense data taking campaign to finalize the calibration of the MICE Particle Identification (PID) detectors and the understanding of the beam line, which completes the STEPI phase of MICE. We highlight the main results from these data.

  10. Neutron beam testing of triblades

    SciTech Connect (OSTI)

    Michalak, Sarah E [Los Alamos National Laboratory; Du Bois, Andrew J [Los Alamos National Laboratory; Storlie, Curtis B [Los Alamos National Laboratory; Rust, William N [Los Alamos National Laboratory; Du Bois, David H [Los Alamos National Laboratory; Modl, David G [Los Alamos National Laboratory; Quinn, Heather M [Los Alamos National Laboratory; Blanchard, Sean P [Los Alamos National Laboratory; Manuzzato, Andrea [UNIV DEGLI STUDI DI PADOVA ITALY

    2010-12-16T23:59:59.000Z

    Four IBM Triblades were tested in the Irradiation of Chips and Electronics facility at the Los Alamos Neutron Science Center. Triblades include two dual-core Opteron processors and four PowerXCell 8i (Cell) processors. The Triblades were tested in their field configuration while running different applications, with the beam aimed at the Cell processor or the Opteron running the application. Testing focused on the Cell processors, which were tested while running five different applications and an idle condition. While neither application nor Triblade was statistically important in predicting the hazard rate, the hazard rate when the beam was aimed at the Opterons was significantly higher than when it was aimed at the Cell processors. In addition, four Cell blades (one in each Triblade) suffered voltage shorts, leading to their inoperability. The hardware tested is the same as that in the Roadrunner supercomputer.

  11. Fresnel diffraction patterns as accelerating beams

    E-Print Network [OSTI]

    Zhang, Yiqi; Zheng, Huaibin; Wu, Zhenkun; Li, Yuanyuan; Lu, Keqing; Zhang, Yanpeng

    2013-01-01T23:59:59.000Z

    We demonstrate that beams originating from Fresnel diffraction patterns are self-accelerating in free space. In addition to accelerating and self-healing, they also exhibit parabolic deceleration property, which is in stark contrast to other accelerating beams. We find that the trajectory of Fresnel paraxial accelerating beams is similar to that of nonparaxial Weber beams. Decelerating and accelerating regions are separated by a critical propagation distance, at which no acceleration is present. During deceleration, the Fresnel diffraction beams undergo self-smoothing, in which oscillations of the diffracted waves gradually focus and smooth out at the critical distance.

  12. Beam Cooling with ionisation losses

    E-Print Network [OSTI]

    C. Rubbia; A. Ferrari; Y. Kadi; V. Vlachoudis

    2006-02-03T23:59:59.000Z

    A novel type of particle "cooling", called Ionization Cooling, is applicable to slow (v of the order of 0.1c) ions stored in a small ring. The many traversals through a thin foil enhance the nuclear reaction probability, in a steady configuration in which ionisation losses are recovered at each turn by a RF-cavity. For a uniform target "foil" the longitudinal momentum spread diverges exponentially since faster (slower) particles ionise less (more) than the average. In order to "cool" also longitudinally, a chromaticity has to be introduced with a wedge shaped "foil". Multiple scattering and straggling are then "cooled" in all three dimensions, with a method similar to the one of synchrotron cooling, but valid for low energy ions. Particles then stably circulate in the beam indefinitely, until they undergo for instance nuclear processes in the thin target foil. This new method is under consideration for the nuclear production of a few MeV/A ion beams. Simple reactions, for instance Li 7 + D Li 8 + p, are more favourably exploited with the heavier ion colliding against a gas-jet D2 target. Kinematics is generally very favourable, with emission angles in a narrow angular cone and a relatively concentrated outgoing energy spectrum which allows an efficient collection as a neutral gas in a tiny volume with a technology at high temperatures perfected at ISOLDE. It is however of a much more general applicability. The method appears capable of producing a "table top" storage ring with an accumulation rate in excess of 10**14 Li-8 radioactive ion/s for possible use for radioactive beams for physics studies (for example for beta-beams) or for therapy.

  13. Scattering apodizer for laser beams

    DOE Patents [OSTI]

    Summers, M.A.; Hagen, W.F.; Boyd, R.D.

    1984-01-01T23:59:59.000Z

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  14. Scattering apodizer for laser beams

    DOE Patents [OSTI]

    Summers, Mark A. (Livermore, CA); Hagen, Wilhelm F. (Livermore, CA); Boyd, Robert D. (Livermore, CA)

    1985-01-01T23:59:59.000Z

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  15. Bipolar molecular outflows driven by hydromagnetic protostellar winds

    E-Print Network [OSTI]

    Christopher D. Matzner; Christopher F. McKee

    1999-09-29T23:59:59.000Z

    We demonstrate that magnetically-collimated protostellar winds will sweep ambient material into thin, radiative, momentum-conserving shells whose features reproduce those commonly observed in bipolar molecular outflows. We find the typical position-velocity and mass-velocity relations to occur in outflows in a wide variety of ambient density distributions, regardless of the time histories of their driving winds.

  16. Thermodiffusion in model nanofluids by molecular dynamics simulations

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Thermodiffusion in model nanofluids by molecular dynamics simulations G. Galliero1,2,* , S. Volz3-Jones fluids and for model nanofluids (spherical non-metallic nanoparticles + Lennard-Jones fluid) where concentration. Then, in nanofluids in the liquid state, by changing the nature of the nanoparticle (size, mass

  17. Generation of low-divergence laser beams

    DOE Patents [OSTI]

    Kronberg, James W. (108 Independent Blvd., Aiken, SC 29801)

    1993-01-01T23:59:59.000Z

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source.

  18. Generation of low-divergence laser beams

    DOE Patents [OSTI]

    Kronberg, J.W.

    1993-09-14T23:59:59.000Z

    Apparatus for transforming a conventional beam of coherent light, having a Gaussian energy distribution and relatively high divergence, into a beam in which the energy distribution approximates a single, non-zero-order Bessel function and which therefore has much lower divergence. The apparatus comprises a zone plate having transmitting and reflecting zones defined by the pattern of light interference produced by the combination of a beam of coherent light with a Gaussian energy distribution and one having such a Bessel distribution. The interference pattern between the two beams is a concentric array of multiple annuli, and is preferably recorded as a hologram. The hologram is then used to form the transmitting and reflecting zones by photo-etching portions of a reflecting layer deposited on a plate made of a transmitting material. A Bessel beam, containing approximately 50% of the energy of the incident beam, is produced by passing a Gaussian beam through such a Bessel zone plate. The reflected beam, also containing approximately 50% of the incident beam energy and having a Bessel energy distribution, can be redirected in the same direction and parallel to the transmitted beam. Alternatively, a filter similar to the Bessel zone plate can be placed within the resonator cavity of a conventional laser system having a front mirror and a rear mirror, preferably axially aligned with the mirrors and just inside the front mirror to generate Bessel energy distribution light beams at the laser source. 11 figures.

  19. Particle beam injector system and method

    DOE Patents [OSTI]

    Guethlein, Gary

    2013-06-18T23:59:59.000Z

    Methods and devices enable coupling of a charged particle beam to a radio frequency quadrupole accelerator. Coupling of the charged particle beam is accomplished, at least in-part, by relying on of sensitivity of the input phase space acceptance of the radio frequency quadrupole to the angle of the input charged particle beam. A first electric field across a beam deflector deflects the particle beam at an angle that is beyond the acceptance angle of the radio frequency quadrupole. By momentarily reversing or reducing the established electric field, a narrow portion of the charged particle beam is deflected at an angle within the acceptance angle of the radio frequency quadrupole. In another configuration, beam is directed at an angle within the acceptance angle of the radio frequency quadrupole by the first electric field and is deflected beyond the acceptance angle of the radio frequency quadrupole due to the second electric field.

  20. Dust Emission from the Perseus Molecular Cloud

    E-Print Network [OSTI]

    S. Schnee; J. Li; A. A. Goodman; A. I. Sargent

    2008-05-27T23:59:59.000Z

    Using far-infrared emission maps taken by IRAS and Spitzer and a near-infrared extinction map derived from 2MASS data, we have made dust temperature and column density maps of the Perseus molecular cloud. We show that the emission from transiently heated very small grains and the big grain dust emissivity vary as a function of extinction and dust temperature, with higher dust emissivities for colder grains. This variable emissivity can not be explained by temperature gradients along the line of sight or by noise in the emission maps, but is consistent with grain growth in the higher density and lower temperature regions. By accounting for the variations in the dust emissivity and VSG emission, we are able to map the temperature and column density of a nearby molecular cloud with better accuracy than has previously been possible.

  1. mass communication advertising &

    E-Print Network [OSTI]

    Finzi, Adrien

    mass communication advertising & public relations introduction. Graduate programs in the Department of Mass Communication, Advertising, and Public Relations provide an entry to a wide spectrum of careers in the communication industry. Classes, internships, site visits, and presentations by top professionals offer students

  2. The Origins of Mass

    ScienceCinema (OSTI)

    Lincoln, Don

    2014-08-07T23:59:59.000Z

    The Higgs boson was discovered in July of 2012 and is generally understood to be the origin of mass. While those statements are true, they are incomplete. It turns out that the Higgs boson is responsible for only about 2% of the mass of ordinary matter. In this dramatic new video, Dr. Don Lincoln of Fermilab tells us the rest of the story.

  3. The Origins of Mass

    SciTech Connect (OSTI)

    Lincoln, Don

    2014-07-30T23:59:59.000Z

    The Higgs boson was discovered in July of 2012 and is generally understood to be the origin of mass. While those statements are true, they are incomplete. It turns out that the Higgs boson is responsible for only about 2% of the mass of ordinary matter. In this dramatic new video, Dr. Don Lincoln of Fermilab tells us the rest of the story.

  4. Fermionic Molecular Dynamics: Multifragmentation in heavy-ion collisions and in excited nuclei

    E-Print Network [OSTI]

    H. Feldmeier; J. Schnack

    1997-03-17T23:59:59.000Z

    Within Fermionic Molecular Dynamics we investigate fragmentation of a compound system which was created in a heavy-ion collision at a beam energy in the Fermi energy domain and the decay of excited iron nuclei. We show that in FMD many-body correlations play an important role in the formation of fragments.

  5. Massive Quiescent Cores in Orion. -- II. Core Mass Function

    E-Print Network [OSTI]

    Li, D; Goldsmith, P F; Langer, W D

    2006-01-01T23:59:59.000Z

    We have surveyed submillimeter continuum emission from relatively quiescent regions in the Orion molecular cloud to determine how the core mass function in a high mass star forming region compares to the stellar initial mass function. Such studies are important for understanding the evolution of cores to stars, and for comparison to formation processes in high and low mass star forming regions. We used the SHARC II camera on the Caltech Submillimeter Observatory telescope to obtain 350 \\micron data having angular resolution of about 9 arcsec, which corresponds to 0.02 pc at the distance of Orion. Our analysis combining dust continuum and spectral line data defines a sample of 51 Orion molecular cores with masses ranging from 0.1 \\Ms to 46 \\Ms and a mean mass of 9.8 \\Ms, which is one order of magnitude higher than the value found in typical low mass star forming regions, such as Taurus. The majority of these cores cannot be supported by thermal pressure or turbulence, and are probably supercritical.They are th...

  6. Absorption Mode FT-ICR Mass Spectrometry Imaging

    SciTech Connect (OSTI)

    Smith, Donald F.; Kilgour, David P.; Konijnenburg, Marco; O'Connor, Peter B.; Heeren, Ronald M.

    2013-12-03T23:59:59.000Z

    Fourier transform ion cyclotron resonance mass spectrometry offers the highest mass resolving power for molecular imaging experiments. This high mass resolving power ensures that closely spaced peaks at the same nominal mass are resolved for proper image generation. Typically higher magnetic fields are used to increase mass resolving power. However, a gain in mass resolving power can also be realized by phase correction of the data for absorption mode display. In addition to mass resolving power, absorption mode offers higher mass accuracy and signal-to-noise ratio over the conventional magnitude mode. Here we present the first use of absorption mode for Fourier transform ion cyclotron resonance mass spectrometry imaging. The Autophaser algorithm is used to phase correct each spectrum (pixel) in the image and then these parameters are used by the Chameleon work-flow based data processing software to generate absorption mode ?Datacubes? for image and spectral viewing. Absorption mode reveals new mass and spatial features that are not resolved in magnitude mode and results in improved selected ion image contrast.

  7. Submicro and Nano Structured Porous Materials for the Production of High-Intensity Exotic Radioactive Ion Beams

    E-Print Network [OSTI]

    Fernandes, Sandrina; Stora, Thierry

    2010-01-01T23:59:59.000Z

    ISOLDE, the CERN Isotope Separator On-line DEvice is a unique source of low energy beams of radioactive isotopes - atomic nuclei that have too many or too few neutrons to be stable. The facility is like a small ‘chemical factory’, giving the possibility of changing one element to another, by selecting the atomic mass of the required isotope beam in the mass separator, rather as the ‘alchemists’ once imagined. It produces a total of more than 1000 different isotopes from helium to radium, with half-lives down to milliseconds, by impinging a 1.4 GeV proton beam from the Proton Synchrotron Booster (PSB) onto special targets, yielding a wide variety of atomic fragments. Different components then extract the nuclei and separate them according to mass. The post-accelerator REX (Radioactive beam EXperiment) at ISOLDE accelerates the radioactive beams up to 3 MeV/u for many experiments. A wide international user radioactive ion beam (RIB) community investigates fundamental aspects of nuclear physics, particle...

  8. Integral window/photon beam position monitor and beam flux detectors for x-ray beams

    DOE Patents [OSTI]

    Shu, Deming (Darien, IL); Kuzay, Tuncer M. (Naperville, IL)

    1995-01-01T23:59:59.000Z

    A monitor/detector assembly in a synchrotron for either monitoring the position of a photon beam or detecting beam flux may additionally function as a vacuum barrier between the front end and downstream segment of the beamline in the synchrotron. A base flange of the monitor/detector assembly is formed of oxygen free copper with a central opening covered by a window foil that is fused thereon. The window foil is made of man-made materials, such as chemical vapor deposition diamond or cubic boron nitrate and in certain configurations includes a central opening through which the beams are transmitted. Sensors of low atomic number materials, such as aluminum or beryllium, are laid on the window foil. The configuration of the sensors on the window foil may be varied depending on the function to be performed. A contact plate of insulating material, such as aluminum oxide, is secured to the base flange and is thereby clamped against the sensor on the window foil. The sensor is coupled to external electronic signal processing devices via a gold or silver lead printed onto the contact plate and a copper post screw or alternatively via a copper screw and a copper spring that can be inserted through the contact plate and coupled to the sensors. In an alternate embodiment of the monitor/detector assembly, the sensors are sandwiched between the window foil of chemical vapor deposition diamond or cubic boron nitrate and a front foil made of similar material.

  9. A power beaming based infrastructure for space power

    SciTech Connect (OSTI)

    Bamberger, J.A.

    1991-08-01T23:59:59.000Z

    At present all space mission power requirements are met by integral, on-board, self-contained power systems. To provide needed flexibility for space exploration and colonization, an additional approach to on-board, self-contained power systems is needed. Power beaming, an alternative approach to providing power, has the potential to provide increased mission flexibility while reducing total mass launched into space. Laser-power beaming technology provides a viable power and communication infrastructure that can be developed sequentially as it is applied to power satellite constellations in Earth orbit and to orbital transport vehicles transferring satellites and cargos to geosynchronous orbit and beyond. Coupled with nuclear electric propulsion systems for cargo transport, the technology can be used to provide global power to the Lunar surface and to Mars' surface and moons. The technology can be developed sequentially as advances in power system and propulsion system technology occur. This paper presents stepwise development of an infrastructure based on power beaming that can support the space development and exploration goals of the Space Exploration Initiative. Power scenarios based on commonality of power systems hardware with cargo transport vehicles are described. Advantages of this infrastructure are described. 12 refs., 4 figs., 1 tab.

  10. A GROUND-BASED MEASUREMENT OF THE RELATIVISTIC BEAMING EFFECT IN A DETACHED DOUBLE WHITE DWARF BINARY

    SciTech Connect (OSTI)

    Shporer, Avi [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Santa Barbara, CA 93117 (United States); Kaplan, David L. [Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States); Steinfadt, Justin D. R.; Bildsten, Lars [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States); Howell, Steve B. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Mazeh, Tsevi, E-mail: ashporer@lcogt.ne [Wise Observatory, Tel Aviv University, Tel Aviv 69978 (Israel)

    2010-12-20T23:59:59.000Z

    We report on the first ground-based measurement of the relativistic beaming effect (aka Doppler boosting). We observed the beaming effect in the detached, non-interacting eclipsing double white dwarf (WD) binary NLTT 11748. Our observations were motivated by the system's high mass-ratio and low-luminosity ratio, leading to a large beaming-induced variability amplitude at the orbital period of 5.6 hr. We observed the system during three nights at the 2.0 m Faulkes Telescope North with the SDSS-g' filter and fitted the data simultaneously for the beaming, ellipsoidal, and reflection effects. Our fitted relative beaming amplitude is (3.0 {+-} 0.4) x 10{sup -3}, consistent with the expected amplitude from a blackbody spectrum given the photometric primary radial velocity (RV) amplitude and effective temperature. This result is a first step in testing the relation between the photometric beaming amplitude and the spectroscopic RV amplitude in NLTT 11748 and similar systems. We did not identify any variability due to the ellipsoidal or reflection effects, consistent with their expected undetectable amplitude for this system. Low-mass, helium-core WDs are expected to reside in binary systems, where in some of those systems the binary companion is a faint C/O WD and the two stars are detached and non-interacting, as in the case of NLTT 11748. The beaming effect can be used to search for the faint binary companion in those systems using wide-band photometry.

  11. Charged Kaon Mass Measurement using the Cherenkov Effect

    E-Print Network [OSTI]

    The MIPP Collaboration; N. Graf; A. Lebedev; R. J. Abrams; U. Akgun; G. Aydin; W. Baker; P. D. Barnes Jr.; T. Bergfeld; L. Beverly; A. Bujak; D. Carey; C. Dukes; F. Duru; G. J. Feldman; A. Godley; E. Gülmez; Y. O. Günayd?n; H. R. Gustafson; L. Gutay; E. Hartouni; P. Hanlet; S. Hansen; M. Heffner; C. Johnstone; D. Kaplan; O. Kamaev; J. Kilmer; J. Klay; M. Kostin; D. Lange; J. Ling; M. J. Longo; L. C. Lu; C. Materniak; M. D. Messier; H. Meyer; D. E. Miller; S. R. Mishra; K. Nelson; T. Nigmanov; A. Norman; Y. Onel; J. M. Paley; H. K. Park; A. Penzo; R. J. Peterson; R. Raja; D. Rajaram; D. Ratnikov; C. Rosenfeld; H. Rubin; S. Seun; N. Solomey; R. Soltz; E. Swallow; R. Schmitt; P. Subbarao; Y. Torun; T. E. Tope; K. Wilson; D. Wright; K. Wu

    2010-01-04T23:59:59.000Z

    The two most recent and precise measurements of the charged kaon mass use X-rays from kaonic atoms and report uncertainties of 14 ppm and 22 ppm yet differ from each other by 122 ppm. We describe the possibility of an independent mass measurement using the measurement of Cherenkov light from a narrow-band beam of kaons, pions, and protons. This technique was demonstrated using data taken opportunistically by the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory which recorded beams of protons, kaons, and pions ranging in momentum from +37 GeV/c to +63 GeV/c. The measured value is 491.3 +/- 1.7 MeV/c^2, which is within 1.4 sigma of the world average. An improvement of two orders of magnitude in precision would make this technique useful for resolving the ambiguity in the X-ray data and may be achievable in a dedicated experiment.

  12. Ultra-high-mass mass spectrometry with charge discrimination using cryogenic detectors

    DOE Patents [OSTI]

    Frank, Matthias (Berkeley, CA); Mears, Carl A. (Oakland, CA); Labov, Simon E. (Berkeley, CA); Benner, W. Henry (Danville, CA)

    1999-01-01T23:59:59.000Z

    An ultra-high-mass time-of-flight mass spectrometer using a cryogenic particle detector as an ion detector with charge discriminating capabilities. Cryogenic detectors have the potential for significantly improving the performance and sensitivity of time-of-flight mass spectrometers, and compared to ion multipliers they exhibit superior sensitivity for high-mass, slow-moving macromolecular ions and can be used as "stop" detectors in time-of-flight applications. In addition, their energy resolving capability can be used to measure the charge state of the ions. Charge discrimination is very valuable in all time-of-flight mass spectrometers. Using a cryogenically-cooled Nb-Al.sub.2 O.sub.3 -Nb superconductor-insulator-superconductor (SIS) tunnel junction (STJ) detector operating at 1.3 K as an ion detector in a time-of-flight mass spectrometer for large biomolecules it was found that the STJ detector has charge discrimination capabilities. Since the cryogenic STJ detector responds to ion energy and does not rely on secondary electron production, as in the conventionally used microchannel plate (MCP) detectors, the cryogenic detector therefore detects large molecular ions with a velocity-independent efficiency approaching 100%.

  13. Absolute neutrino mass measurements

    SciTech Connect (OSTI)

    Wolf, Joachim [Karlsruhe Institute of Technology (KIT), IEKP, Postfach 3640, 76021 Karlsruhe (Germany)

    2011-10-06T23:59:59.000Z

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  14. Improvements on the accuracy of beam bugs

    SciTech Connect (OSTI)

    Chen, Y.J.; Fessenden, T.

    1998-08-17T23:59:59.000Z

    At LLNL resistive wall monitors are used to measure the current and position used on ETA-II show a droop in signal due to a fast redistribution time constant of the signals. This paper presents the analysis and experimental test of the beam bugs used for beam current and position measurements in and after the fast kicker. It concludes with an outline of present and future changes that can be made to improve the accuracy of these beam bugs. of intense electron beams in electron induction linacs and beam transport lines. These, known locally as ''beam bugs'', have been used throughout linear induction accelerators as essential diagnostics of beam current and location. Recently, the development of a fast beam kicker has required improvement in the accuracy of measuring the position of beams. By picking off signals at more than the usual four positions around the monitor, beam position measurement error can be greatly reduced. A second significant source of error is the mechanical variation of the resistor around the bug.

  15. Analytical calculation of the smear for long-range beam-beam interactions

    E-Print Network [OSTI]

    Kaltchev, D I

    2010-01-01T23:59:59.000Z

    The Lie-algebraic method is used to develop generalized Courant-Snyder invariant in the presence of an arbitrary number of beam-beam collisions, head-on or long-range, in a storage ring collider. The invariant is obtained by concatenating nonlinear beam-beam maps in the horizontal plane and to first order in the beam-beam parameter. Tracking evidence is presented to illustrate that with LHC parameters the invariant is indeed preserved and can be used to predict the smear of horizontal emittance observed in tracking simulations. We discuss the limits of applicability of this model for realistic LHC collision schemes.

  16. Synchrotron radiation damping, intrabeam scattering and beam-beam simulations for HE-LHC

    SciTech Connect (OSTI)

    Valishev, A.; /Fermilab

    2011-03-01T23:59:59.000Z

    The proposed High-Energy LHC project presents an unusual combination of strong synchrotron radiation damping and intrabeam scattering, which is not seen in present-day hadron colliders. The subject of investigation reported in this paper was the simulation of beam-beam effect for the HE-LHC parameters. Parameters of SR and IBS are calculated, and the luminosity evolution is simulated in the absence of beam-beam interaction. Then, a weak-strong numerical simulation is used to predict the effect of beam-beam interaction on particle losses and emittance evolution.

  17. Substructured multibody molecular dynamics.

    SciTech Connect (OSTI)

    Grest, Gary Stephen; Stevens, Mark Jackson; Plimpton, Steven James; Woolf, Thomas B. (Johns Hopkins University, Baltimore, MD); Lehoucq, Richard B.; Crozier, Paul Stewart; Ismail, Ahmed E.; Mukherjee, Rudranarayan M. (Rensselaer Polytechnic Institute, Troy, NY); Draganescu, Andrei I.

    2006-11-01T23:59:59.000Z

    We have enhanced our parallel molecular dynamics (MD) simulation software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator, lammps.sandia.gov) to include many new features for accelerated simulation including articulated rigid body dynamics via coupling to the Rensselaer Polytechnic Institute code POEMS (Parallelizable Open-source Efficient Multibody Software). We use new features of the LAMMPS software package to investigate rhodopsin photoisomerization, and water model surface tension and capillary waves at the vapor-liquid interface. Finally, we motivate the recipes of MD for practitioners and researchers in numerical analysis and computational mechanics.

  18. Proton beam therapy control system

    DOE Patents [OSTI]

    Baumann, Michael A; Beloussov, Alexandre V; Bakir, Julide; Armon, Deganit; Olsen, Howard B; Salem, Dana

    2013-12-03T23:59:59.000Z

    A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

  19. Proton beam therapy control system

    DOE Patents [OSTI]

    Baumann, Michael A; Beloussov, Alexandre V; Bakir, Julide; Armon, Deganit; Olsen, Howard B; Salem, Dana

    2013-06-25T23:59:59.000Z

    A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

  20. Protective laser beam viewing device

    DOE Patents [OSTI]

    Neil, George R.; Jordan, Kevin Carl

    2012-12-18T23:59:59.000Z

    A protective laser beam viewing system or device including a camera selectively sensitive to laser light wavelengths and a viewing screen receiving images from the laser sensitive camera. According to a preferred embodiment of the invention, the camera is worn on the head of the user or incorporated into a goggle-type viewing display so that it is always aimed at the area of viewing interest to the user and the viewing screen is incorporated into a video display worn as goggles over the eyes of the user.

  1. Proton beam therapy control system

    DOE Patents [OSTI]

    Baumann, Michael A. (Riverside, CA); Beloussov, Alexandre V. (Bernardino, CA); Bakir, Julide (Alta Loma, CA); Armon, Deganit (Redlands, CA); Olsen, Howard B. (Colton, CA); Salem, Dana (Riverside, CA)

    2008-07-08T23:59:59.000Z

    A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

  2. Proton beam therapy control system

    DOE Patents [OSTI]

    Baumann, Michael A. (Riverside, CA); Beloussov, Alexandre V. (San Bernardino, CA); Bakir, Julide (Alta Loma, CA); Armon, Deganit (Longmeadow, MA); Olsen, Howard B. (Irvine, CA); Salem, Dana (Riverside, CA)

    2010-09-21T23:59:59.000Z

    A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

  3. Nuclear astrophysics and electron beams

    SciTech Connect (OSTI)

    Schwenk, A. [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany)

    2013-11-07T23:59:59.000Z

    Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei.

  4. SPEAR3 Beam Line Availability

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's PossibleRadiation Protection245C Unlimited ReleaseWelcome ton n u a l r e p o rMarch 21,SPEAR3Beam

  5. BIOLOGICAL ANALYSIS Mass Spectrometry

    E-Print Network [OSTI]

    Greenaway, Alan

    Microscope) Analytical Equipment · High Performance Liquid Chromatography · Fast Protein Liquid Chromatography · Gas Chromatography · GC/MS · Elemental Analyser Molecular Biology Equipment · Biorad PCR Machine reactor for scale up studies In-line Particle sizers Rheometers Separation tanks Oscillating column (4m

  6. Masses of Fundamental Particles

    E-Print Network [OSTI]

    Hidezumi Terazawa

    2014-06-11T23:59:59.000Z

    In the original paper entitled, "Masses of Fundamental Particles"(arXiv:1109.3705v5, 10 Feb 2012), not only the masses of fundamental particles including the weak bosons, Higgs boson, quarks, and leptons, but also the mixing angles of quarks and those of neutrinos are all explained and/or predicted in the unified composite models of quarks and leptons successfully. In this addendum entitled, "Higgs Boson Mass in the Minimal Unified Subquark Model", it is emphasized that the Higgs boson mass is predicted to be about 130Gev in the minimal unified subquark model, which agrees well with the experimental values of 125-126GeV recently found by the ATLAS and CMS Collaborations at the LHC.

  7. Microlens Mass Functions

    E-Print Network [OSTI]

    William D. Heacox

    2005-10-10T23:59:59.000Z

    A non-parametric statistical model is constructed to directly relate The distribution of observed microlens timescales to that of the mass Function of the population from which the lenses are drawn, corrected For observational selection based on timescales and event amplifications. Explicit distributions are derived for microlensing impact parameters and maximum amplifications; both are shown to be statistically independent of all other parameters in the problem, including lens mass. The model is used to demonstrate that the narrow range of microlens timescales observed toward the Large Magellanic Cloud (LMC) is probably not consistent with lensing by a widely distributed spheroidal population of large velocity dispersion, as expected of a dark halo; but is consistent with lensing within a rotating thick disk. Poor numerical conditioning on the statistical connection between lens masses and event timescales, and small number statistics, severely limit the mass function information obtainable from current microlensing surveys toward the LMC.

  8. (Quantum Molecular Dynamics Method) (Classical Molecular Dynamics Method)

    E-Print Network [OSTI]

    Maruyama, Shigeo

    1-1 (Quantum Molecular Dynamics Method) (Classical Molecular Dynamics Method) 2) Verlet(Verlet's leap frog) (17)(18) ( ) i i ii m t t t t t t F vv + -= + 22 (17

  9. The trigger system of the ICARUS experiment for the CNGS beam

    E-Print Network [OSTI]

    M. Antonello; B. Baibussinov; P. Benetti; F. Boffelli; A. Bubak; E. Calligarich; S. Centro; A. Cesana; K. Cieslik; D. B. Cline; A. G. Cocco; A. Dabrowska; D. Dequal; A. Dermenev; R. Dolfini; A. Falcone; C. Farnese; A. Fava; A. Ferrari; G. Fiorillo; D. Gibin; S. Gninenko; A. Guglielmi; M. Haranczyk; J. Holeczek; M. Kirsanov; J. Kisiel; I. Kochanek; J. Lagoda; S. Mania; A. Menegolli; G. Meng; C. Montanari; M. Nicoletto; S. Otwinowski; P. Picchi; F. Pietropaolo; P. Plonski; A. Rappoldi; G. L. Raselli; M. Rossella; C. Rubbia; P. Sala; A. Scaramelli; E. Segreto; F. Sergiampietri; D. Stefan; R. Sulej; M. Szarska; M. Terrani; M. Torti; F. Varanini; S. Ventura; C. Vignoli; H. Wang; X. Yang; A. Zalewska; A. Zani; K. Zaremba

    2014-08-08T23:59:59.000Z

    The ICARUS T600 detector, with its 470 tons of active mass, is the largest liquid Argon TPC ever built. Operated for three years in the LNGS underground laboratory, it has collected thousands of CNGS neutrino beam interactions and cosmic ray events with energy spanning from tens of MeV to tens of GeV, with a trigger system based on scintillation light, charge signal on TPC wires and time information (for beam related events only). The performance of trigger system in terms of efficiency, background and live-time as a function of the event energy for the CNGS data taking is presented.

  10. Radiation beam calorimetric power measurement system

    DOE Patents [OSTI]

    Baker, John (Livermore, CA); Collins, Leland F. (Pleasanton, CA); Kuklo, Thomas C. (Ripon, CA); Micali, James V. (Dublin, CA)

    1992-01-01T23:59:59.000Z

    A radiation beam calorimetric power measurement system for measuring the average power of a beam such as a laser beam, including a calorimeter configured to operate over a wide range of coolant flow rates and being cooled by continuously flowing coolant for absorbing light from a laser beam to convert the laser beam energy into heat. The system further includes a flow meter for measuring the coolant flow in the calorimeter and a pair of thermistors for measuring the temperature difference between the coolant inputs and outputs to the calorimeter. The system also includes a microprocessor for processing the measured coolant flow rate and the measured temperature difference to determine the average power of the laser beam.

  11. Focused electron and ion beam systems

    DOE Patents [OSTI]

    Leung, Ka-Ngo; Reijonen, Jani; Persaud, Arun; Ji, Qing; Jiang, Ximan

    2004-07-27T23:59:59.000Z

    An electron beam system is based on a plasma generator in a plasma ion source with an accelerator column. The electrons are extracted from a plasma cathode in a plasma ion source, e.g. a multicusp plasma ion source. The beam can be scanned in both the x and y directions, and the system can be operated with multiple beamlets. A compact focused ion or electron beam system has a plasma ion source and an all-electrostatic beam acceleration and focusing column. The ion source is a small chamber with the plasma produced by radio-frequency (RF) induction discharge. The RF antenna is wound outside the chamber and connected to an RF supply. Ions or electrons can be extracted from the source. A multi-beam system has several sources of different species and an electron beam source.

  12. Virtual mask digital electron beam lithography

    DOE Patents [OSTI]

    Baylor, Larry R. (Farragut, TN); Thomas, Clarence E. (Knoxville, TN); Voelkl, Edgar (Oak Ridge, TN); Moore, James A. (Powell, TN); Simpson, Michael L. (Knoxville, TN); Paulus, Michael J. (Knoxville, TN)

    1999-01-01T23:59:59.000Z

    Systems and methods for direct-to-digital holography are described. An apparatus includes a laser; a beamsplitter optically coupled to the laser; a reference beam mirror optically coupled to the beamsplitter; an object optically coupled to the beamsplitter, a focusing lens optically coupled to both the reference beam mirror and the object; and a digital recorder optically coupled to the focusing lens. A reference beam is incident upon the reference beam mirror at a non-normal angle, and the reference beam and an object beam are focused by the focusing lens at a focal plane of the digital recorder to form an image. The systems and methods provide advantages in that computer assisted holographic measurements can be made.

  13. Rippled beam free electron laser amplifier

    DOE Patents [OSTI]

    Carlsten, Bruce E. (Los Alamos, NM)

    1999-01-01T23:59:59.000Z

    A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a TM.sub.0n mode. A waveguide defines an axial centerline and, a solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam.

  14. HIGEE Mass Transfer

    E-Print Network [OSTI]

    Mohr, R. J.; Fowler, R.

    HIGEE MASS TRANSFER R.J. Mohr and R. Fowler GLITSCH, INC. Dallas, Texas ABSTRACT Distillation, absorption, and gas stripping have traditionally been performed in tall columns utilizing trays or packing. Columns perform satisfactorily... transfer system which utilizes a rotating bed of packing to achieve high efficiency separations, and consequent reduction in size and weight. INTRODUCTION HIGEE is probably one of the most interesting developments in mass transfer equipment made...

  15. Mass of Cu-57

    E-Print Network [OSTI]

    Gagliardi, Carl A.; Semon, D. R.; Tribble, Robert E.; Vanausdeln, L. A.

    1986-01-01T23:59:59.000Z

    the experimental and theoretical Coulomb displacement energies for similar cases in A =17 and 41 has been attributed~ to ground state correlations in the nuclear wave functions. It is in- teresting to examine the mass 57 mirror nuclei to investi- gate... indicated. Reference 9. 'Reference 7. Reference 6. 'This work. 34 MASS OF Cu 1665 the 3=57 Coulomb displacement energy, using radial wave functions obtained in a spherical Hartree-Fock cal- culation, assuming a closed Ni core, and including...

  16. A ground-based measurement of the relativistic beaming effect in a detached double WD binary

    E-Print Network [OSTI]

    Shporer, Avi; Steinfadt, Justin D R; Bildsten, Lars; Howell, Steve B; Mazeh, Tsevi

    2010-01-01T23:59:59.000Z

    We report on the first ground-based measurement of the relativistic beaming effect (aka Doppler boosting). We observed the beaming effect in the detached, non-interacting eclipsing double white dwarf (WD) binary NLTT 11748. Our observations were motivated by the system's high mass ratio and low luminosity ratio, leading to a large beaming-induced variability amplitude at the orbital period of 5.6 hr. We observed the system during 3 nights at the 2.0m Faulkes Telescope North with the SDSS-g' filter, and fitted the data simultaneously for the beaming, ellipsoidal and reflection effects. Our fitted relative beaming amplitude is (3.0 +/- 0.4) x 10^(-3), consistent with the expected amplitude from a blackbody spectrum given the photometric primary radial velocity amplitude and effective temperature. This result is a first step in testing the relation between the photometric beaming amplitude and the spectroscopic radial velocity amplitude in NLTT 11748 and similar systems. We did not identify any variability due t...

  17. Interfacial Properties of Electron Beam Cured Composites

    SciTech Connect (OSTI)

    Eberle, C.C.

    1999-12-30T23:59:59.000Z

    The objectives of the CRADA are to: Confirm that fiber-resin adhesion is responsible for the observed poor shear properties; Determine the mechanism(s) responsible for poor adhesion between carbon fibers and epoxy resins after e-beam curing; Develop and evaluate resin systems and fiber treatments to improve the properties of e-beam cured, carbon-fiber-reinforced composites; and Develop refined methods for processing e-beam cured, carbon-fiber-reinforced composites.

  18. B13+: Photodriven Molecular Wankel Engine. | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    B13+: Photodriven Molecular Wankel Engine. B13+: Photodriven Molecular Wankel Engine. Abstract: Synthetic molecular motors that are capable of delivering controlled movement upon...

  19. Molecular Biology DEGREE PROGRAMME

    E-Print Network [OSTI]

    Levi, Ran

    to the course co-ordinator for that module (See University Catalogue of Courses or SMS World Wide Web Pages in molecular biology have a wide range of career options, including virtually all areas of biology, medicine with mastering statistics, graphics and word processing software packages. General Enquiries The Degree Programme

  20. High power, high beam quality regenerative amplifier

    DOE Patents [OSTI]

    Hackel, Lloyd A. (Livermore, CA); Dane, Clifford B. (Livermore, CA)

    1993-01-01T23:59:59.000Z

    A regenerative laser amplifier system generates high peak power and high energy per pulse output beams enabling generation of X-rays used in X-ray lithography for manufacturing integrated circuits. The laser amplifier includes a ring shaped optical path with a limited number of components including a polarizer, a passive 90 degree phase rotator, a plurality of mirrors, a relay telescope, and a gain medium, the components being placed close to the image plane of the relay telescope to reduce diffraction or phase perturbations in order to limit high peak intensity spiking. In the ring, the beam makes two passes through the gain medium for each transit of the optical path to increase the amplifier gain to loss ratio. A beam input into the ring makes two passes around the ring, is diverted into an SBS phase conjugator and proceeds out of the SBS phase conjugator back through the ring in an equal but opposite direction for two passes, further reducing phase perturbations. A master oscillator inputs the beam through an isolation cell (Faraday or Pockels) which transmits the beam into the ring without polarization rotation. The isolation cell rotates polarization only in beams proceeding out of the ring to direct the beams out of the amplifier. The diffraction limited quality of the input beam is preserved in the amplifier so that a high power output beam having nearly the same diffraction limited quality is produced.