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Title: On the efficacy of imploding plasma liners for magnetized fusion target compression

Abstract

A new theoretical model is formulated to study the idea of merging a spherical array of converging plasma jets to form a 'plasma liner' that further converges to compress a magnetized plasma target to fusion conditions [Y. C. F. Thio et al., 'Magnetized target fusion in a spheroidal geometry with standoff drivers', Current Trends in International Fusion Research II, edited by E. Panarella (National Research Council Canada, Ottawa, Canada, 1999)]. For a spherically imploding plasma liner shell with high initial Mach number (M=liner speed/sound speed) the rise in liner density with decreasing radius r goes as {rho}{approx}1/r{sup 2}, for any constant adiabatic index {gamma}=d ln p/d ln {rho}. Accordingly, spherical convergence amplifies the ram pressure of the liner on target by the factor A{approx}C{sup 2}, indicating strong coupling to its radial convergence C=r{sub m}/R, where r{sub m}(R)=jet merging radius (compressed target radius), and A=compressed target pressure/initial liner ram pressure. Deuterium-tritium (DT) plasma liners with initial velocity {approx}100 km/s and {gamma}=5/3, need to be hypersonic M{approx}60 and thus cold in order to realize values of A{approx}10{sup 4} necessary for target ignition. For optically thick DT liners, T<2 eV, n>10{sup 19}-10{sup 20} cm{sup -3}, blackbody radiative cooling is appreciable and may counteractmore » compressional heating during the later stages of the implosion. The fluid then behaves as if the adiabatic index were depressed below 5/3, which in turn means that the same amplification A=1.6x10{sup 4} can be accomplished with a reduced initial Mach number M{approx_equal}12.7({gamma}-0.3){sup 4.86}, valid in the range (10<M<60). Analytical calculations indicate that the hydrodynamic efficiency for plasma liners assembled by current and anticipated plasma jets is <4%. A new similarity model for fusion {alpha}-particle heating of the collapsed liner indicates that 'spark' ignition of the DT liner fuel does not appear to be possible for magnetized fusion targets with typical threshold values of areal density {rho}R<0.02 g cm{sup -2}.« less

Authors:
 [1]
  1. General Atomics, P.O. Box 85608, San Diego, California 92186-5688 (United States)
Publication Date:
OSTI Identifier:
21120440
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 15; Journal Issue: 6; Other Information: DOI: 10.1063/1.2948346; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALPHA PARTICLES; AMPLIFICATION; COMPRESSION; DEUTERIUM; EFFICIENCY; IMPLOSIONS; MACH NUMBER; PLASMA; PLASMA HEATING; PLASMA JETS; RADIATIVE COOLING; SOUND WAVES; SPHERICAL CONFIGURATION; THERMONUCLEAR IGNITION; TRITIUM

Citation Formats

Parks, P B. On the efficacy of imploding plasma liners for magnetized fusion target compression. United States: N. p., 2008. Web. doi:10.1063/1.2948346.
Parks, P B. On the efficacy of imploding plasma liners for magnetized fusion target compression. United States. https://doi.org/10.1063/1.2948346
Parks, P B. Sun . "On the efficacy of imploding plasma liners for magnetized fusion target compression". United States. https://doi.org/10.1063/1.2948346.
@article{osti_21120440,
title = {On the efficacy of imploding plasma liners for magnetized fusion target compression},
author = {Parks, P B},
abstractNote = {A new theoretical model is formulated to study the idea of merging a spherical array of converging plasma jets to form a 'plasma liner' that further converges to compress a magnetized plasma target to fusion conditions [Y. C. F. Thio et al., 'Magnetized target fusion in a spheroidal geometry with standoff drivers', Current Trends in International Fusion Research II, edited by E. Panarella (National Research Council Canada, Ottawa, Canada, 1999)]. For a spherically imploding plasma liner shell with high initial Mach number (M=liner speed/sound speed) the rise in liner density with decreasing radius r goes as {rho}{approx}1/r{sup 2}, for any constant adiabatic index {gamma}=d ln p/d ln {rho}. Accordingly, spherical convergence amplifies the ram pressure of the liner on target by the factor A{approx}C{sup 2}, indicating strong coupling to its radial convergence C=r{sub m}/R, where r{sub m}(R)=jet merging radius (compressed target radius), and A=compressed target pressure/initial liner ram pressure. Deuterium-tritium (DT) plasma liners with initial velocity {approx}100 km/s and {gamma}=5/3, need to be hypersonic M{approx}60 and thus cold in order to realize values of A{approx}10{sup 4} necessary for target ignition. For optically thick DT liners, T<2 eV, n>10{sup 19}-10{sup 20} cm{sup -3}, blackbody radiative cooling is appreciable and may counteract compressional heating during the later stages of the implosion. The fluid then behaves as if the adiabatic index were depressed below 5/3, which in turn means that the same amplification A=1.6x10{sup 4} can be accomplished with a reduced initial Mach number M{approx_equal}12.7({gamma}-0.3){sup 4.86}, valid in the range (10<M<60). Analytical calculations indicate that the hydrodynamic efficiency for plasma liners assembled by current and anticipated plasma jets is <4%. A new similarity model for fusion {alpha}-particle heating of the collapsed liner indicates that 'spark' ignition of the DT liner fuel does not appear to be possible for magnetized fusion targets with typical threshold values of areal density {rho}R<0.02 g cm{sup -2}.},
doi = {10.1063/1.2948346},
url = {https://www.osti.gov/biblio/21120440}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 15,
place = {United States},
year = {2008},
month = {6}
}