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Title: Runaway electron production during intense electron beam penetration in dense plasma

Abstract

Relativistic electrons are efficiently generated when multiterawatt lasers focused to ultrahigh intensities > or approx. 10{sup 19} W/cm{sup 2} illuminate the surface of dense plasma targets. A theoretical study finds that during typical picosecond pulse widths, significant amounts of Dreicer produced runaway electrons can build up due to the high axial electric field driving the neutralizing return current. An important consequence is that there will be a conversion of plasma current to runaway electron current, which is maximized at some optimum value of the beam-to-plasma density ratio N{sub b}=n{sub b}/n{sub e}, depending on the plasma collisionality. At collisionalities representative of solid target experiments, complete conversion to runaway electrons can only take place over a certain range of N{sub b} values. At higher collisionalities and pulse widths, applicable to the fast ignition concept for inertial confinement fusion, it was found that conversion to runaways has a peak at {approx}90% around N{sub b}{approx}0.06. Significant lessening of target material heating by Joule current dissipation is also possible, since part of the beam energy loss is transferred through the electric field directly to the formation of energetic runaways. Implications for beam transport inhibition by the electric field are also discussed.

Authors:
;  [1];  [2]
  1. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20960117
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2424430; (c) 2007 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 TRANSPORT; BEAM-PLASMA SYSTEMS; ELECTRIC CURRENTS; ELECTRIC FIELDS; ELECTRON BEAMS; ENERGY LOSSES; HEATING; INERTIAL CONFINEMENT; PLASMA DENSITY; PULSES; RELATIVISTIC PLASMA; RELATIVISTIC RANGE; RUNAWAY ELECTRONS; THERMONUCLEAR IGNITION

Citation Formats

Parks, P. B., Cowan, T. E., and University of Nevada-Nevada Terawatt Facility, Reno, Nevada 89557-0042. Runaway electron production during intense electron beam penetration in dense plasma. United States: N. p., 2007. Web. doi:10.1063/1.2424430.
Parks, P. B., Cowan, T. E., & University of Nevada-Nevada Terawatt Facility, Reno, Nevada 89557-0042. Runaway electron production during intense electron beam penetration in dense plasma. United States. doi:10.1063/1.2424430.
Parks, P. B., Cowan, T. E., and University of Nevada-Nevada Terawatt Facility, Reno, Nevada 89557-0042. Mon . "Runaway electron production during intense electron beam penetration in dense plasma". United States. doi:10.1063/1.2424430.
@article{osti_20960117,
title = {Runaway electron production during intense electron beam penetration in dense plasma},
author = {Parks, P. B. and Cowan, T. E. and University of Nevada-Nevada Terawatt Facility, Reno, Nevada 89557-0042},
abstractNote = {Relativistic electrons are efficiently generated when multiterawatt lasers focused to ultrahigh intensities > or approx. 10{sup 19} W/cm{sup 2} illuminate the surface of dense plasma targets. A theoretical study finds that during typical picosecond pulse widths, significant amounts of Dreicer produced runaway electrons can build up due to the high axial electric field driving the neutralizing return current. An important consequence is that there will be a conversion of plasma current to runaway electron current, which is maximized at some optimum value of the beam-to-plasma density ratio N{sub b}=n{sub b}/n{sub e}, depending on the plasma collisionality. At collisionalities representative of solid target experiments, complete conversion to runaway electrons can only take place over a certain range of N{sub b} values. At higher collisionalities and pulse widths, applicable to the fast ignition concept for inertial confinement fusion, it was found that conversion to runaways has a peak at {approx}90% around N{sub b}{approx}0.06. Significant lessening of target material heating by Joule current dissipation is also possible, since part of the beam energy loss is transferred through the electric field directly to the formation of energetic runaways. Implications for beam transport inhibition by the electric field are also discussed.},
doi = {10.1063/1.2424430},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}