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Title: Adjoint Fokker-Planck equation and runaway electron dynamics

The adjoint Fokker-Planck equation method is applied to study the runaway probability function and the expected slowing-down time for highly relativistic runaway electrons, including the loss of energy due to synchrotron radiation. In direct correspondence to Monte Carlo simulation methods, the runaway probability function has a smooth transition across the runaway separatrix, which can be attributed to effect of the pitch angle scattering term in the kinetic equation. However, for the same numerical accuracy, the adjoint method is more efficient than the Monte Carlo method. The expected slowing-down time gives a novel method to estimate the runaway current decay time in experiments. A new result from this work is that the decay rate of high energy electrons is very slow when E is close to the critical electric field. This effect contributes further to a hysteresis previously found in the runaway electron population.
Authors:
; ;  [1] ;  [2]
  1. Princeton University, Princeton, New Jersey 08544 (United States)
  2. Columbia University, New York, New York 10027 (United States)
Publication Date:
OSTI Identifier:
22493801
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 1; Other Information: (c) 2016 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; ACCURACY; COMPUTERIZED SIMULATION; ELECTRIC FIELDS; ENERGY LOSSES; FOKKER-PLANCK EQUATION; HYSTERESIS; INCLINATION; KINETIC EQUATIONS; MONTE CARLO METHOD; RELATIVISTIC RANGE; RUNAWAY ELECTRONS; SCATTERING; SLOWING-DOWN; SYNCHROTRON RADIATION