skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Heavy Ion Fusion Science Virtual National Laboratory 1st Quarter FY09 Milestone Report

Abstract

No abstract prepared.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
945605
Report Number(s):
LLNL-TR-409568
TRN: US0901182
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION; 99 GENERAL AND MISCELLANEOUS; LABORATORIES; COMPUTERIZED SIMULATION; HEAVY ION FUSION REACTIONS

Citation Formats

Friedman, A, Anders, A, Cohen, R H, Davidson, R C, Dorf, M, Grote, D P, Yung, J, Kaganovich, I D, Lidia, S M, Logan, B G, Markidis, S, Roy, P K, Seidl, P A, Vay, J L, and Welch, D R. Heavy Ion Fusion Science Virtual National Laboratory 1st Quarter FY09 Milestone Report. United States: N. p., 2008. Web. doi:10.2172/945605.
Copy to clipboard
Friedman, A, Anders, A, Cohen, R H, Davidson, R C, Dorf, M, Grote, D P, Yung, J, Kaganovich, I D, Lidia, S M, Logan, B G, Markidis, S, Roy, P K, Seidl, P A, Vay, J L, & Welch, D R. Heavy Ion Fusion Science Virtual National Laboratory 1st Quarter FY09 Milestone Report. United States. doi:10.2172/945605.
Copy to clipboard
Friedman, A, Anders, A, Cohen, R H, Davidson, R C, Dorf, M, Grote, D P, Yung, J, Kaganovich, I D, Lidia, S M, Logan, B G, Markidis, S, Roy, P K, Seidl, P A, Vay, J L, and Welch, D R. Mon . "Heavy Ion Fusion Science Virtual National Laboratory 1st Quarter FY09 Milestone Report". United States. doi:10.2172/945605. https://www.osti.gov/servlets/purl/945605.
Copy to clipboard
@article{osti_945605,
title = {Heavy Ion Fusion Science Virtual National Laboratory 1st Quarter FY09 Milestone Report},
author = {Friedman, A and Anders, A and Cohen, R H and Davidson, R C and Dorf, M and Grote, D P and Yung, J and Kaganovich, I D and Lidia, S M and Logan, B G and Markidis, S and Roy, P K and Seidl, P A and Vay, J L and Welch, D R},
abstractNote = {No abstract prepared.},
doi = {10.2172/945605},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Dec 22 00:00:00 EST 2008},
month = {Mon Dec 22 00:00:00 EST 2008}
}
Copy to clipboard
Technical Report:
View Technical Report
DOI:  10.2172/945605
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • ; ;
    This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory has completed simulations of a fast correction scheme to compensate for chromatic and time-dependent defocusing effects in the transport of ion beams to the target plane in the NDCX-1 facility. Physics specifications for implementation in NDCX-1 and NDCX-2 have been established. This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory has completed simulations of a fast correction scheme to compensate for chromatic and time-dependent defocusing effects in the transport of ion beams to the target plane in the NDCX-1 facility. Physics specifications formore » implementation in NDCX-1 and NDCX-2 have been established. Focal spot differences at the target plane between the compressed and uncompressed regions of the beam pulse have been modeled and measured on NDCX-1. Time-dependent focusing and energy sweep from the induction bunching module are seen to increase the compressed pulse spot size at the target plane by factors of two or more, with corresponding scaled reduction in the peak intensity and fluence on target. A time-varying beam envelope correction lens has been suggested to remove the time-varying aberration. An Einzel (axisymmetric electric) lens system has been analyzed and optimized for general transport lines, and as a candidate correction element for NDCX-1. Attainable high-voltage holdoff and temporal variations of the lens driving waveform are seen to effect significant changes on the beam envelope angle over the duration of interest, thus confirming the utility of such an element on NDCX-1. Modeling of the beam dynamics in NDCX-1 was performed using a time-dependent (slice) envelope code and with the 3-D, self-consistent, particle-in-cell code WARP. Proof of concept was established with the slice envelope model such that the spread in beam waist positions relative to the target plane can be minimized with a carefully designed Einzel lens waveform and transport line. WARP simulations have verified the efficacy of the Einzel lens while including more detailed beam physics. WARP simulations have also indicated some unpredicted transittime effects, and methods are currently being explored to compensate and reduce this complication. We have explored the use of an Einzel lens, or system of Einzel lenses, to compensate for chromatic aberrations in the beam focal spot in the NDCX-2 target plane. The final beam manipulations in NDCX-2 (linear velocity ramp, charge neutralization, high field final focus solenoid) are similar to NDCX-1 though the NDCX-2 beam has much higher energy and current. The most relevant distinctions are that the pulse duration at the entrance to the drift compression section is tenfold shorter, and that the beam energy tenfold higher, than in NDCX-1. Placing a time-dependent, envelope angle correcting element at the neutralized drift region entrance presents a very significant challenge to voltage holdoff and voltage swing V(t) in a single Einzel lens. Placing the Einzel lens(es) further upstream reduces the required voltage risetime V'(t) to effect the necessary envelope correction, while increasing the duration over which the timedependent voltage must vary. While this simplifies the technological challenge of designing and operating a Einzel lens in NDCX-2, it does require much finer control of the correcting waveform and measurements of its effect on space-charge dominated beams over a much longer axial path length to target than in the NDCX-1.« less

  • ; ; ; ...
    This milestone has been met. In the previous quarter (3rd quarter FY2008), the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) completed the new experimental target chamber facility for future Warm Dense Matter (WDM) experiments [1]. The target chamber is operational and target experiments are now underway, using beams focused by a final focus solenoid and compressed by an improved bunching waveform. Initial experiments have demonstrated the capability of the Neutralized Drift Compression Experiment (NDCX) beam to heat bulk matter in target foils. The experiments have focused on tuning and characterizing the NDCX beam in the target chamber, implementing themore » target assembly, and implementing target diagnostics in the target chamber environment. We have completed a characterization and initial optimization of the compressed and uncompressed NDCX beam entering the target chamber. The neutralizing plasma has been significantly improved to increase the beam neutralization in the target chamber. Preliminary results from recent beam tests of a gold cone for concentrating beam energy on target are encouraging and indicate the potential to double beam intensity on target. Other advantages of the cone include the large amount of neutralizing secondary electrons expected from the grazing incidence at the cone walls, and the shielding of the target from the edges of the beam pulse. The first target temperature measurements with the fast optical pyrometer were made on Sep. 12, 2008. The fast optical pyrometer is a unique and significant new diagnostic. These new results demonstrate for the first time beam heating of the target to a temperature well over 2000 K. The initial experimental results are suggestive of potentially interesting physics. The rapid initial rise and subsequent decay of the target temperature during the beam pulse indicate changes in the balance of beam heating and target evaporative cooling, a behavior which may be affected by phenomena such as droplet formation and rapid changes in the optical properties of the hot target material. NDCX, possibly uniquely, is capable of studying these changes because of its wide range of diagnostic capabilities. These capabilities include target diagnostics already in place such as the fast pyrometer and streak camera, as well as the ability to measure both ion beam transmission and optical transmission through the foil. Measurements with these diagnostic techniques can help determine the rate at which the target is breaking up into droplets and the rate at which its bulk optical properties are changing.« less

  • ; ; ; ...
    Simulations suggest that the plasma density must exceed the beam density throughout the drift compression and focusing section in order to inhibit the space charge forces that would limit the spot size and beam intensity on the target. WDM experiments will therefore require plasma densities up to 10{sup 14}/cm{sup 3}, with the highest density in the last few centimeters before the target. This work was guided by the simulations performed for the FY09 Q1 milestone. This milestone has been met and we report results of modifications made to the NDCX beamline to improve the longitudinal and radial distribution of themore » neutralizing plasma in the region near the target plane. In Section 2, we review pertinent simulation results from the FY09 Q1 milestone. Section 3 describes the design, and beam measurements following installation, of a biased, self-supporting metal grid that produces neutralizing electrons from glancing interception of beam ions. Section 4 describes the design and initial testing of a compact Ferro-Electric Plasma Source (FEPS) that will remove the remaining 'exclusion zone' in the neutralizing plasma close to the target plane. Section 5 describes the modification of the beamline to decrease the gap between the FEPS section exit and the final focus solenoid (FFS). Section 6 presents a summary and conclusions.« less

  • ; ; ; ...
    This milestone has been met. The effort contains two main components: (1) Experimental results of warm dense matter target experiments on optimized NDCX-I configurations that include measurements of target temperature and transient target behavior. (2) A theoretical model of the target response to beam heating that includes an equilibrium heating model of the target foil and a model for droplet formation in the target for comparison with experimental results. The experiments on ion-beam target heating use a 300-350-keV K{sup +} pulsed beam from the Neutralized Compression Drift Experiment (NDCX-I) accelerator at LBNL. The NDCX-I accelerator delivers an uncompressed pulse beammore » of several microseconds with a typical power density of >100 kW/cm{sup 2} over a final focus spot size of about 1 mm. An induction bunching module the NDCX-I compresses a portion of the beam pulse to reach a much higher power density over 2 nanoseconds. Under these conditions the free-standing foil targets are rapidly heated to temperatures to over 4000 K. We model the target thermal dynamics using the equation of heat conduction for the temperature T(x,t) as a function of time (t) and spatial dimension along the beam direction (x). The competing cooling processes release energy from the surface of the foil due to evaporation, radiation, and thermionic (Richardson) emission. A description of the experimental configuration of the target chamber and results from initial beam-target experiments are reported in our FY08 4th Quarter and FY09 2nd Quarter Milestone Reports. The WDM target diagnostics include a high-speed multichannel optical pyrometer, optical streak camera, VISAR, and high-speed gated cameras. The fast optical pyrometer is a unique and significant new diagnostic which provides valuable information on the temperature evolution of the heated target.« less

  • ; ; ; ...
    This milestone has been accomplished. The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) has developed and implemented an initial beam-in-plasma implicit modeling capability in Warp; has carried out tests validating the behavior of the models employed; has compared the results of electrostatic and electromagnetic models when applied to beam expansion in an NDCX-I relevant regime; has compared Warp and LSP results on a problem relevant to NDCX-I; has modeled wave excitation by a rigid beam propagating through plasma; and has implemented and begun testing a more advanced implicit method that correctly captures electron drift motion even when timesteps toomore » large to resolve the electron gyro-period are employed. The HIFS-VNL is well on its way toward having a state-of-the-art source-to-target simulation capability that will enable more effective support of ongoing experiments in the NDCX series and allow more confident planning for future ones.« less