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Title: Enhanced stopping of macro-particles in particle-in-cell simulations

We derive an equation for energy transfer from relativistic charged particles to a cold background plasma appropriate for finite-size particles that are used in particle-in-cell simulation codes. Expressions for one-, two-, and three-dimensional particles are presented, with special attention given to the two-dimensional case. This energy transfer is due to the electric field of the wake set up in the background plasma by the relativistic particle. The enhanced stopping is dependent on the q{sup 2}/m, where q is the charge and m is the mass of the relativistic particle, and therefore simulation macro-particles with large charge but identical q/m will stop more rapidly. The stopping power also depends on the effective particle shape of the macro-particle. These conclusions are verified in particle-in-cell simulations. We present 2D simulations of test particles, relaxation of high-energy tails, and integrated fast ignition simulations showing that the enhanced drag on macro-particles may adversely affect the results of these simulations in a wide range of high-energy density plasma scenarios. We also describe a particle splitting algorithm which can potentially overcome this problem and show its effect in controlling the stopping of macro-particles.
Authors:
;  [1] ;  [1] ;  [2] ;  [1] ;  [2] ;  [2] ;  [3] ; ;  [4] ;  [5]
  1. Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)
  2. (United States)
  3. Lawrence Livermore National Laboratory, California 94550 (United States)
  4. GoLP/Instituto de Plasma e Fusão Nuclear, 1049-001 Lisboa (Portugal)
  5. University of Rochester, Rochester, New York (United States)
Publication Date:
OSTI Identifier:
22252821
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHARGED PARTICLES; DRAG; ELECTRIC FIELDS; ENERGY DENSITY; ENERGY TRANSFER; PLASMA; RELATIVISTIC RANGE; SIMULATION; STOPPING POWER; TEST PARTICLES; THERMONUCLEAR IGNITION; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS