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Title: Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams

Abstract

During the contract period, absolute cross sections for projectile ionization, and in some cases for target ionization, were measured for energetic (MeV/u) low-charge-state heavy ions interacting with gases typically found in high and ultra-high vacuum environments. This information is of interest to high-energy-density research projects as inelastic interactions with background gases can lead to serious detrimental effects when intense ion beams are accelerated to high energies, transported and possibly confined in storage rings. Thus this research impacts research and design parameters associated with projects such as the Heavy Ion Fusion Project, the High Current and Integrated Beam Experiments in the USA and the accelerator upgrade at GSI-Darmstadt, Germany. Via collaborative studies performed at GSI-Darmstadt, at the University of East Carolina, and Texas A&M University, absolute cross sections were measured for a series of collision systems using MeV/u heavy ions possessing most, or nearly all, of their bound electrons, e.g., 1.4 MeV/u Ar{sup +}, Xe{sup 3+}, and U{sup 4,6,10+}. Interactions involving such low-charge-state heavy ions at such high energies had never been previously explored. Using these, and data taken from the literature, an empirical model was developed for extrapolation to much higher energies. In order to extend our measurements to muchmore » higher energies, the gas target at the Experimental Storage Ring in GSI-Darmstadt was used. Cross sections were measured between 20 and 50 MeV/u for U{sup 28+}- H{sub 2} and - N{sub 2}, the primary components found in high and ultra-high vacuum systems. Storage lifetime measurements, information inversely proportional to the cross section, were performed up to 180 MeV/u. The lifetime and cross section data test various theoretical approaches used to calculate cross sections for many-electron systems. Various high energy density research projects directly benefit by this information. As a result, the general public benefits indirectly. The original intent of this project was to measure absolute cross sections for electron loss from fast, low-charge-state, heavy ions for a wide range of charge states, impact energies, and projectiles in order to provide sufficient information for extrapolation to other energies or collision systems. Ideally, data for singly charged ions in the several to tens of MeV/u energy range was sought. Because of the limited number of facilities available that are capable of accelerating heavy ions to high velocities, several collaborations were established. Accelerator access for measurements plus specific accelerator limitations with respect to energies and charge states that could be accessed were the primary limiting factors in achieving these goals. However, as outlined below, we were able to obtain data for a broad range of parameters. These data, coupled with data taken from the literature, enabled us to provide guidance with respect to design parameters needed for various high energy density projects.« less

Authors:
Publication Date:
Research Org.:
Missouri University of Science and Technology (formerly University of Missouri-Rolla)
Sponsoring Org.:
Chicago Operations Office; USDOE Office of Science and Technology (EM-50)
OSTI Identifier:
964984
Report Number(s):
Final Technical Report
DOE Contract Number:
FG02-00ER54578
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; Fusion Energy Sciences

Citation Formats

DuBois, Robert D. Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams. United States: N. p., 2006. Web. doi:10.2172/964984.
DuBois, Robert D. Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams. United States. doi:10.2172/964984.
DuBois, Robert D. Fri . "Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams". United States. doi:10.2172/964984. https://www.osti.gov/servlets/purl/964984.
@article{osti_964984,
title = {Heavy Inertial Confinement Energy: Interactions Involoving Low charge State Heavy Ion Injection Beams},
author = {DuBois, Robert D},
abstractNote = {During the contract period, absolute cross sections for projectile ionization, and in some cases for target ionization, were measured for energetic (MeV/u) low-charge-state heavy ions interacting with gases typically found in high and ultra-high vacuum environments. This information is of interest to high-energy-density research projects as inelastic interactions with background gases can lead to serious detrimental effects when intense ion beams are accelerated to high energies, transported and possibly confined in storage rings. Thus this research impacts research and design parameters associated with projects such as the Heavy Ion Fusion Project, the High Current and Integrated Beam Experiments in the USA and the accelerator upgrade at GSI-Darmstadt, Germany. Via collaborative studies performed at GSI-Darmstadt, at the University of East Carolina, and Texas A&M University, absolute cross sections were measured for a series of collision systems using MeV/u heavy ions possessing most, or nearly all, of their bound electrons, e.g., 1.4 MeV/u Ar{sup +}, Xe{sup 3+}, and U{sup 4,6,10+}. Interactions involving such low-charge-state heavy ions at such high energies had never been previously explored. Using these, and data taken from the literature, an empirical model was developed for extrapolation to much higher energies. In order to extend our measurements to much higher energies, the gas target at the Experimental Storage Ring in GSI-Darmstadt was used. Cross sections were measured between 20 and 50 MeV/u for U{sup 28+}- H{sub 2} and - N{sub 2}, the primary components found in high and ultra-high vacuum systems. Storage lifetime measurements, information inversely proportional to the cross section, were performed up to 180 MeV/u. The lifetime and cross section data test various theoretical approaches used to calculate cross sections for many-electron systems. Various high energy density research projects directly benefit by this information. As a result, the general public benefits indirectly. The original intent of this project was to measure absolute cross sections for electron loss from fast, low-charge-state, heavy ions for a wide range of charge states, impact energies, and projectiles in order to provide sufficient information for extrapolation to other energies or collision systems. Ideally, data for singly charged ions in the several to tens of MeV/u energy range was sought. Because of the limited number of facilities available that are capable of accelerating heavy ions to high velocities, several collaborations were established. Accelerator access for measurements plus specific accelerator limitations with respect to energies and charge states that could be accessed were the primary limiting factors in achieving these goals. However, as outlined below, we were able to obtain data for a broad range of parameters. These data, coupled with data taken from the literature, enabled us to provide guidance with respect to design parameters needed for various high energy density projects.},
doi = {10.2172/964984},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 14 00:00:00 EDT 2006},
month = {Fri Apr 14 00:00:00 EDT 2006}
}

Technical Report:

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  • Our principal goals, and activities in support of those goals, over the next five years are as follows: (1) Optimize the properties of the NDCX-II beam for each class of target experiments; achieve quantitative agreement with measurements; develop improved machine configurations and operating points. To accomplish these goals, we plan to use Warp to simulate NDCX-II from source to target, in full kinetic detail, including first-principles modeling of beam neutralization by plasma. The output from an ensemble of Warp runs (representing shot-to-shot variations) will be used as input to target simulations using ALE-AMR on NERSC, and other codes. (2) Developmore » enhanced versions of NDCX-II (the machine is designed to be extensible and reconfigurable), and carry out studies to define a next-step ion beam facility. To accomplish these goals, much of the work will involve iterative optimization employing Warp runs that assume ideal beam neutralization downstream of the accelerator. (3) Carry out detailed target simulations in the Warm Dense Matter regime using the ALE-AMR code, including surface tension effects, liquid-vapor coexistence, and accurate models of both the driving beam and the target geometry. For this we will need to make multiple runs (to capture shot-to-shot variations), and to both develop and employ synthetic diagnostics (to enable comparison with experiments). The new science that will be revealed is the physics of the transition from the liquid to vapor state of a volumetrically superheated material, wherein droplets are formed, and wherein phase transitions, surface tension and hydrodynamics all play significant roles in the dynamics. These simulations will enable calculations of equation of state and other material properties, and will also be of interest for their illumination of the science of droplet formation.« less
  • The charge-state distributions of ions emerging from carbon foils were compared for equal velocity monoatomic negative ions incident on the foil. Such comparisons were performed for O/sub 2//sup -/ vs O/sup -/ and for C/sub 3//sup -/ vs C/sup -/ and C/sub 4//sup -/ vs C/sup -/. Measured charge state distributions are shown for carbon and oxygen respectively and how the observed effect varies with foil thickness for the oxygen case. In all cases, the distribution is shifted toward lower average charge states for the molecular beams and the effect persists even though attenuated up to and including the thickestmore » foils used. The most straightforward interpretation of these results is that for each component of the cluster there are more correlated electrons available for pickup than for single ions. 1 reference. (JFP)« less
  • In 1967, R.L. Hirsch reported neutron production rates of 10/sup 10/ neutrons per second from an electrostatic inertial confinement device. The device consisted of six ion guns injecting deuterium or a mixture of deuterium and tritium ions into an evacuated cathode chamber at 30 to 150 keV. No previous theoretical model for this experiment has adequately explained the observed neutron fluxes. A new model that includes the effects of charge exchange and ionization in the ion guns is analyzed. This model predicts three main features of the observed neutron flux; neutron output proportional to gun current, neutron production localized atmore » the center of the evacuated chamber, and neutron production decreasing with increasing neutral background gas density. Previous analysis modelled the ion guns as being monoenergetic. In this study, the ion gun output is modelled as a mixture of ions and fast neutrals with energies ranging from zero to the maximum gun energy. Using this theoretical model, a survey of the possible operating parameters indicates that the device was probably operated at or near the most efficient combined values of voltage and background pressure. Applications of the theory to other devices are discussed.« less
  • A new code, bimc, is under development to determine if a beam of heavy ions can be focused to the necessary spot-size radius of about 2 mm within an inertial confinement reactor chamber where the background gas densities are on the order of 10{sup 14}--10{sup 15} cm{sup {minus}3} Lithium (or equivalent). Beam transport is expected to be strongly affected by stripping and collective plasma phenomena; however, if propagation is possible in this regime, it could lead to simplified reactor designs. The beam is modeled using a 2 1/2 D particle-in-cell (PIC) simulation code coupled with a Monte Carlo (MC) methodmore » for analyzing collisions. The MC code follows collisions between the beam ions and neutral background gas atoms that account for the generation of electrons and background gas ions (ionization), and an increase of the charge state of the beam ions (stripping). The PIC code models the complete dynamics of the interaction of the various charged particle species with the self generated electromagnetic fields. Details of the code model and preliminary results are presented.« less
  • From February to July 2006, I have been doing research as a guest at Lawrence Berkeley National Laboratory (LBNL), in the Heavy Ion Fusion group. This internship, which counts as one semester in my master's program in France, I was very pleased to do it in a field that I consider has the beauty of fundamental physics, and at the same time the special appeal of a quest for a long-term and environmentally-respectful energy source. During my stay at LBNL, I have been involved in three projects, all of them related to Neutralized Drift Compression Experiment (NDCX). The first one,more » experimental and analytical, has consisted in measuring the effects of the eddy currents induced by the pulsed magnets in the conducting plates of the source and diagnostic chambers of the Solenoid Transport Experiment (STX, which is a subset of NDCX). We have modeled the effect and run finite-element simulations that have reproduced the perturbation to the field. Then, we have modified WARP, the Particle-In-Cell code used to model the whole experiment, in order to import realistic fields including the eddy current effects and some details of each magnet. The second project has been to take part in a campaign of WARP simulations of the same experiment to understand the leakage of electrons that was observed in the experiment as a consequence to some diagnostics and the failure of the electrostatic electron trap. The simulations have shown qualitative agreement with the measured phenomena, but are still in progress. The third project, rather theoretical, has been related to the upcoming target experiment of a thin aluminum foil heated by a beam to the 1-eV range. At the beginning I helped by analyzing simulations of the hydrodynamic expansion and cooling of the heated material. But, progressively, my work turned into making estimates for the nature of the liquid/vapor two-phase flow. In particular, I have been working on criteria and models to predict the formation of droplets, their size, and their partial or total evaporation in the expanding flow.« less