Adjoint Fokker-Planck equation and runaway electron dynamics

Journal Article · 13 January 2016 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.4938510 · OSTI ID:1468793

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

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1. Princeton Univ., NJ (United States)
2. Columbia Univ., New York, NY (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.

• Research Organization: Columbia Univ., NY (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-03ER54696
• OSTI ID: 1468793
• Alternate ID(s): OSTI ID: 1234783
• Journal Information: Physics of Plasmas, Vol. 23, Issue 1; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English