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Title: Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect

Abstract

To study runaway electron generation in disruptions, we have extended the three-dimensional (two-dimensional in momentum space; one-dimensional in the radial direction) Fokker-Planck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a self-consistent manner. A particular focus is placed on the hot-tail effect in two-dimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electron-electron slowing down time for a few times of the pre-quench thermal velocity. It contributes to not only the enhancement of the primary runaway electron generation but also the broadening of the runaway electron distribution in the pitch angle direction. If the thermal energy loss during the major disruption is assumed to be isotropic, there are hot-tail electrons that have sufficiently large perpendicular momentum, and the runaway electron distribution becomes broader in the pitch angle direction. In addition, the pitch angle scattering also yields the broadening. Since the electric field is reduced due to the burst of runaway electron generation, the time required for accelerating electrons to the runaway region becomes longer. The longer acceleration period makes the pitch-angle scattering more effective.

Authors:
;  [1];  [2]
  1. Department of Engineering, Kyoto University, Kyoto 615-8540 (Japan)
  2. National Institutes for Quantum and Radiological Science and Technology, Aomori 039-3212 (Japan)
Publication Date:
OSTI Identifier:
22600118
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; DISTRIBUTION; DISTRIBUTION FUNCTIONS; ELECTRIC FIELDS; ELECTRON TEMPERATURE; ENERGY LOSSES; FOKKER-PLANCK EQUATION; INCLINATION; ION TEMPERATURE; ONE-DIMENSIONAL CALCULATIONS; PLASMA; RELATIVISTIC RANGE; RUNAWAY ELECTRONS; SCATTERING; SLOWING-DOWN; TAIL ELECTRONS; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp, Fukuyama, A., and Yagi, M. Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect. United States: N. p., 2016. Web. doi:10.1063/1.4953606.
Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp, Fukuyama, A., & Yagi, M. Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect. United States. doi:10.1063/1.4953606.
Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp, Fukuyama, A., and Yagi, M. Wed . "Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect". United States. doi:10.1063/1.4953606.
@article{osti_22600118,
title = {Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect},
author = {Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp and Fukuyama, A. and Yagi, M.},
abstractNote = {To study runaway electron generation in disruptions, we have extended the three-dimensional (two-dimensional in momentum space; one-dimensional in the radial direction) Fokker-Planck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a self-consistent manner. A particular focus is placed on the hot-tail effect in two-dimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electron-electron slowing down time for a few times of the pre-quench thermal velocity. It contributes to not only the enhancement of the primary runaway electron generation but also the broadening of the runaway electron distribution in the pitch angle direction. If the thermal energy loss during the major disruption is assumed to be isotropic, there are hot-tail electrons that have sufficiently large perpendicular momentum, and the runaway electron distribution becomes broader in the pitch angle direction. In addition, the pitch angle scattering also yields the broadening. Since the electric field is reduced due to the burst of runaway electron generation, the time required for accelerating electrons to the runaway region becomes longer. The longer acceleration period makes the pitch-angle scattering more effective.},
doi = {10.1063/1.4953606},
journal = {Physics of Plasmas},
number = 6,
volume = 23,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}