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Title: Robust heavy-ion-beam illumination against a direct-drive-pellet displacement in inertial confinement fusion

Abstract

Nonuniformity of heavy-ion-beam (HIB) illumination is one of key issues in the HIB inertial confinement fusion (ICF): implosion symmetry should be less than a few percent in order to compress a fuel sufficiently and release fusion energy effectively. In this paper a new HIB illumination scheme is presented in order to realize a robust illumination scheme against a displacement of a direct-driven fuel pellet in an ICF reactor. It is known that the HIB illumination nonuniformity is sensitive to a little pellet displacement from a reactor chamber center; a pellet displacement of only 50-100 {mu}m was tolerable in the conventional HIB illumination schemes. In this paper by three-dimensional computer simulations a new robust HIB illumination scheme was found, in which a 200-300 {mu}m displacement is allowed.

Authors:
; ; ; ;  [1];  [2];  [3]
  1. Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585 (Japan)
  2. (Bulgaria)
  3. (Japan)
Publication Date:
OSTI Identifier:
20782398
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 12; Journal Issue: 12; Other Information: DOI: 10.1063/1.2140684; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM-PLASMA SYSTEMS; COMPUTERIZED SIMULATION; FUEL PELLETS; HEAVY IONS; ILLUMINANCE; IMPLOSIONS; INERTIAL CONFINEMENT; ION BEAMS; PLASMA; PLASMA SIMULATION; SYMMETRY; THERMONUCLEAR FUELS

Citation Formats

Miyazawa, K., Ogoyski, A.I., Kawata, S., Someya, T., Kikuchi, T., Department of Physics, Varna Technical University, Varna 9010, and Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585. Robust heavy-ion-beam illumination against a direct-drive-pellet displacement in inertial confinement fusion. United States: N. p., 2005. Web. doi:10.1063/1.2140684.
Miyazawa, K., Ogoyski, A.I., Kawata, S., Someya, T., Kikuchi, T., Department of Physics, Varna Technical University, Varna 9010, & Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585. Robust heavy-ion-beam illumination against a direct-drive-pellet displacement in inertial confinement fusion. United States. doi:10.1063/1.2140684.
Miyazawa, K., Ogoyski, A.I., Kawata, S., Someya, T., Kikuchi, T., Department of Physics, Varna Technical University, Varna 9010, and Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585. Thu . "Robust heavy-ion-beam illumination against a direct-drive-pellet displacement in inertial confinement fusion". United States. doi:10.1063/1.2140684.
@article{osti_20782398,
title = {Robust heavy-ion-beam illumination against a direct-drive-pellet displacement in inertial confinement fusion},
author = {Miyazawa, K. and Ogoyski, A.I. and Kawata, S. and Someya, T. and Kikuchi, T. and Department of Physics, Varna Technical University, Varna 9010 and Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585},
abstractNote = {Nonuniformity of heavy-ion-beam (HIB) illumination is one of key issues in the HIB inertial confinement fusion (ICF): implosion symmetry should be less than a few percent in order to compress a fuel sufficiently and release fusion energy effectively. In this paper a new HIB illumination scheme is presented in order to realize a robust illumination scheme against a displacement of a direct-driven fuel pellet in an ICF reactor. It is known that the HIB illumination nonuniformity is sensitive to a little pellet displacement from a reactor chamber center; a pellet displacement of only 50-100 {mu}m was tolerable in the conventional HIB illumination schemes. In this paper by three-dimensional computer simulations a new robust HIB illumination scheme was found, in which a 200-300 {mu}m displacement is allowed.},
doi = {10.1063/1.2140684},
journal = {Physics of Plasmas},
number = 12,
volume = 12,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
  • Key issues of heavy-ion beam (HIB) inertial confinement fusion (ICF) include an efficient beam transport, beam focus, uniform fuel pellet implosion, etc. The HIB final transport and a direct-drive fuel pellet implosion by computer simulations in HIB ICF are examined. To realize a fine focus on a fuel pellet, space charge neutralization of incident-focusing HIBs may be required at HIB final transport. First, an insulator annular tube guide is proposed at the final portion of the transport, through which an HIB is transported. The physical mechanism of HIB charge neutralization based on an insulator guide is as follows: The localmore » electric field created by HIB induces local discharges, and a plasma is produced on the insulator inner surface. Then electrons are extracted from the plasma by HIB net space charge. The emitted electrons neutralize the beam space charge and move together with the HIB. After the final transport, the HIBs enter a reactor gas and illuminate a fuel pellet. Direct-drive DT pellet implosion were also simulated. The simulation results present a density valley formation by a Pb HIB deposition in a fuel pellet energy absorber layer and a radiation-smoothing effect along the density valley. The density valley provides radiation confinement, and beam nonuniformity can be smoothed along the valley.« less
  • OAK-B135 Target areal density (rR) asymmetries are studied for OMEGA direct-drive spherical implosions. Data indicate that these asymmetries are randomly distributed over time and space. It is shown that the rms variation should, in general, be proportional to the rms variation of on-target laser intensity with an amplification factor of 2/3(CR-1), largely due to the effects of capsule convergence (CR). This result imposes an upper limit to illumination asymmetry that an imploded ignition capsule could tolerate and is relevant to implosions on the National Ignition Facility.
  • The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10{sup −4} level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-spheremore » illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).« less
  • Issues with coupling efficiency, beam illumination symmetry, and Rayleigh-Taylor instability are discussed for spherical heavy-ion-beam-driven targets with and without hohlraums. Efficient coupling of heavy-ion beams to compress direct-drive inertial fusion targets without hohlraums is found to require ion range increasing several-fold during the drive pulse. One-dimensional implosion calculations using the LASNEX inertial confinement fusion target physics code shows the ion range increasing fourfold during the drive pulse to keep ion energy deposition following closely behind the imploding ablation front, resulting in high coupling efficiencies (shell kinetic energy/incident beam energy of 16% to 18%). Ways to increase beam ion range whilemore » mitigating Rayleigh-Taylor instabilities are discussed for future work.« less
  • Analysis and numerical simulations of the smoothing of the speckled illumination of a direct-drive inertial confinement fusion target are presented. In particular, the spatial spectrum of the integrated target fluence is compared across smoothing methods. Two categories of smoothing methods are considered. In one method spatially incoherent light is amplified and directed onto the target, whereas in the other the light is phase modulated and spectrally dispersed before being amplified and then focused through a random phase plate onto the target. The dependence of the smoothed spatial spectrum on the characteristics of phase modulation and dispersion is examined for bothmore » sinusoidal and more general phase modulation. It is shown that smoothing with nonsinusoidal phase modulation can result in spatial spectra that are substantially identical to that obtained with the incoherent light method in which random phase plates are present in both methods and identical beam divergence is assumed. {copyright} 1997 Optical Society of America« less