FokkerPlanck simulation of runaway electron generation in disruptions with the hottail effect
Abstract
To study runaway electron generation in disruptions, we have extended the threedimensional (twodimensional in momentum space; onedimensional in the radial direction) FokkerPlanck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a selfconsistent manner. A particular focus is placed on the hottail effect in twodimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electronelectron slowing down time for a few times of the prequench 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 hottail 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 pitchangle scattering more effective.
 Authors:
 Department of Engineering, Kyoto University, Kyoto 6158540 (Japan)
 National Institutes for Quantum and Radiological Science and Technology, Aomori 0393212 (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; FOKKERPLANCK EQUATION; INCLINATION; ION TEMPERATURE; ONEDIMENSIONAL CALCULATIONS; PLASMA; RELATIVISTIC RANGE; RUNAWAY ELECTRONS; SCATTERING; SLOWINGDOWN; TAIL ELECTRONS; THREEDIMENSIONAL CALCULATIONS; TWODIMENSIONAL CALCULATIONS
Citation Formats
Nuga, H., Email: nuga@pgrp.nucleng.kyotou.ac.jp, Fukuyama, A., and Yagi, M.. FokkerPlanck simulation of runaway electron generation in disruptions with the hottail effect. United States: N. p., 2016.
Web. doi:10.1063/1.4953606.
Nuga, H., Email: nuga@pgrp.nucleng.kyotou.ac.jp, Fukuyama, A., & Yagi, M.. FokkerPlanck simulation of runaway electron generation in disruptions with the hottail effect. United States. doi:10.1063/1.4953606.
Nuga, H., Email: nuga@pgrp.nucleng.kyotou.ac.jp, Fukuyama, A., and Yagi, M.. 2016.
"FokkerPlanck simulation of runaway electron generation in disruptions with the hottail effect". United States.
doi:10.1063/1.4953606.
@article{osti_22600118,
title = {FokkerPlanck simulation of runaway electron generation in disruptions with the hottail effect},
author = {Nuga, H., Email: nuga@pgrp.nucleng.kyotou.ac.jp and Fukuyama, A. and Yagi, M.},
abstractNote = {To study runaway electron generation in disruptions, we have extended the threedimensional (twodimensional in momentum space; onedimensional in the radial direction) FokkerPlanck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a selfconsistent manner. A particular focus is placed on the hottail effect in twodimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electronelectron slowing down time for a few times of the prequench 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 hottail 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 pitchangle scattering more effective.},
doi = {10.1063/1.4953606},
journal = {Physics of Plasmas},
number = 6,
volume = 23,
place = {United States},
year = 2016,
month = 6
}

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