Adjoint FokkerPlanck equation and runaway electron dynamics
The adjoint FokkerPlanck equation method is applied to study the runaway probability function and the expected slowingdown 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 slowingdown 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:

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 Princeton Univ., NJ (United States)
 Columbia Univ., New York, NY (United States)
 Publication Date:
 Grant/Contract Number:
 FG0203ER54696
 Type:
 Accepted Manuscript
 Journal Name:
 Physics of Plasmas
 Additional Journal Information:
 Journal Volume: 23; Journal Issue: 1; Journal ID: ISSN 1070664X
 Publisher:
 American Institute of Physics (AIP)
 Research Org:
 Columbia Univ., NY (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICS AND COMPUTING; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
 OSTI Identifier:
 1468793
 Alternate Identifier(s):
 OSTI ID: 1234783
Liu, Chang, Brennan, Dylan P., Bhattacharjee, Amitava, and Boozer, Allen H.. Adjoint FokkerPlanck equation and runaway electron dynamics. United States: N. p.,
Web. doi:10.1063/1.4938510.
Liu, Chang, Brennan, Dylan P., Bhattacharjee, Amitava, & Boozer, Allen H.. Adjoint FokkerPlanck equation and runaway electron dynamics. United States. doi:10.1063/1.4938510.
Liu, Chang, Brennan, Dylan P., Bhattacharjee, Amitava, and Boozer, Allen H.. 2016.
"Adjoint FokkerPlanck equation and runaway electron dynamics". United States.
doi:10.1063/1.4938510. https://www.osti.gov/servlets/purl/1468793.
@article{osti_1468793,
title = {Adjoint FokkerPlanck equation and runaway electron dynamics},
author = {Liu, Chang and Brennan, Dylan P. and Bhattacharjee, Amitava and Boozer, Allen H.},
abstractNote = {The adjoint FokkerPlanck equation method is applied to study the runaway probability function and the expected slowingdown 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 slowingdown 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.},
doi = {10.1063/1.4938510},
journal = {Physics of Plasmas},
number = 1,
volume = 23,
place = {United States},
year = {2016},
month = {1}
}