Adjoint Fokker-Planck equation and runaway electron dynamics

Journal Article · Fri Jan 15 04:00:00 EST 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4938510· OSTI ID:22493801

Liu, Chang; Brennan, Dylan P.; Bhattacharjee, Amitava ^[1]; Boozer, Allen H. ^[2]

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1. Princeton University, Princeton, New Jersey 08544 (United States)
2. Columbia University, New York, New York 10027 (United States)

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.

• OSTI ID: 22493801
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 1 Vol. 23; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

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