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Title: Threshold for electron trapping nonlinearity in Langmuir waves

Abstract

We assess when electron trapping nonlinearity is expected to be important in Langmuir waves. The basic criterion is that the inverse of the detrapping rate {nu}{sub d} of electrons in the trapping region of velocity space must exceed the bounce period of deeply trapped electrons, {tau}{sub B}{identical_to}(n{sub e}/{delta}n){sup 1/2}2{pi}/{omega}{sub pe}. A unitless figure of merit, the 'bounce number'N{sub B}{identical_to}1/{nu}{sub d}{tau}{sub B}, encapsulates this condition and defines a trapping threshold amplitude for which N{sub B}=1. The detrapping rate is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code LOKI, show trapping nonlinearity increases continuously with N{sub B} for transverse loss, and is significant for N{sub B} Almost-Equal-To 1. The detrapping rate due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified manner. A simple way to combine convective and collisional detrapping is given. Application to underdense plasma conditions in inertial confinement fusion targets is presented. The results show that convective transverse loss is usually the most potent detrapping process in a single f/8 laser speckle. For typical plasma andmore » laser conditions on the inner laser cones of the National Ignition Facility, local reflectivities {approx}3% are estimated to produce significant trapping effects.« less

Authors:
; ; ; ;  [1];  [2]
  1. Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
  2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Publication Date:
OSTI Identifier:
22068887
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 11; Other Information: (c) 2012 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; ELECTRON-ELECTRON COLLISIONS; ELECTRON-ION COLLISIONS; INCLINATION; INERTIAL CONFINEMENT; LANGMUIR FREQUENCY; LASERS; NONLINEAR PROBLEMS; PERFORMANCE; PLASMA; REFLECTIVITY; SCATTERING; TRAPPED ELECTRONS; US NATIONAL IGNITION FACILITY

Citation Formats

Strozzi, D. J., Williams, E. A., Hinkel, D. E., Langdon, A. B., Banks, J. W., and Rose, H. A. Threshold for electron trapping nonlinearity in Langmuir waves. United States: N. p., 2012. Web. doi:10.1063/1.4767644.
Strozzi, D. J., Williams, E. A., Hinkel, D. E., Langdon, A. B., Banks, J. W., & Rose, H. A. Threshold for electron trapping nonlinearity in Langmuir waves. United States. doi:10.1063/1.4767644.
Strozzi, D. J., Williams, E. A., Hinkel, D. E., Langdon, A. B., Banks, J. W., and Rose, H. A. Thu . "Threshold for electron trapping nonlinearity in Langmuir waves". United States. doi:10.1063/1.4767644.
@article{osti_22068887,
title = {Threshold for electron trapping nonlinearity in Langmuir waves},
author = {Strozzi, D. J. and Williams, E. A. and Hinkel, D. E. and Langdon, A. B. and Banks, J. W. and Rose, H. A.},
abstractNote = {We assess when electron trapping nonlinearity is expected to be important in Langmuir waves. The basic criterion is that the inverse of the detrapping rate {nu}{sub d} of electrons in the trapping region of velocity space must exceed the bounce period of deeply trapped electrons, {tau}{sub B}{identical_to}(n{sub e}/{delta}n){sup 1/2}2{pi}/{omega}{sub pe}. A unitless figure of merit, the 'bounce number'N{sub B}{identical_to}1/{nu}{sub d}{tau}{sub B}, encapsulates this condition and defines a trapping threshold amplitude for which N{sub B}=1. The detrapping rate is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code LOKI, show trapping nonlinearity increases continuously with N{sub B} for transverse loss, and is significant for N{sub B} Almost-Equal-To 1. The detrapping rate due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified manner. A simple way to combine convective and collisional detrapping is given. Application to underdense plasma conditions in inertial confinement fusion targets is presented. The results show that convective transverse loss is usually the most potent detrapping process in a single f/8 laser speckle. For typical plasma and laser conditions on the inner laser cones of the National Ignition Facility, local reflectivities {approx}3% are estimated to produce significant trapping effects.},
doi = {10.1063/1.4767644},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 11,
volume = 19,
place = {United States},
year = {2012},
month = {11}
}