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Title: Models of primary runaway electron distribution in the runaway vortex regime

Abstract

Generation of runaway electrons (RE) beams can possibly induce the most deleterious effect of tokamak disruptions. A number of recent numerical calculations have confirmed the formation of a RE bump in their energy distribution by taking into account Synchrontron radiational damping force due to RE’s gyromotions. Here, we present a detailed examination on how the bump location changes at different pitch-angle and the characteristics of the RE pitch-angle distribution. Although REs moving along the magnetic field are preferably accelerated and then populate the phase-space of larger pitch-angle mainly through diffusions, an off-axis peak can still form due to the presence of the vortex structure which causes accumulation of REs at low pitch-angle. A simplified Fokker- Planck model and its semi-analytical solutions based on local expansions around the O point is used to illustrate the characteristics of RE distribution around the O point of the runaway vortex in phase-space. The calculated energy location of the O point together with the local energy and pitch-angle distributions agree with the full numerical solution.

Authors:
 [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1412896
Alternate Identifier(s):
OSTI ID: 1420636
Report Number(s):
[LA-UR-17-24071]
[Journal ID: ISSN 1070-664X; TRN: US1800402]
Grant/Contract Number:  
[AC52-06NA25396]
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
[ Journal Volume: 24; Journal Issue: 11]; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetic Fusion Energy

Citation Formats

Guo, Zehua, Tang, Xian-Zhu, and McDevitt, Christopher J. Models of primary runaway electron distribution in the runaway vortex regime. United States: N. p., 2017. Web. doi:10.1063/1.5006917.
Guo, Zehua, Tang, Xian-Zhu, & McDevitt, Christopher J. Models of primary runaway electron distribution in the runaway vortex regime. United States. doi:10.1063/1.5006917.
Guo, Zehua, Tang, Xian-Zhu, and McDevitt, Christopher J. Wed . "Models of primary runaway electron distribution in the runaway vortex regime". United States. doi:10.1063/1.5006917. https://www.osti.gov/servlets/purl/1412896.
@article{osti_1412896,
title = {Models of primary runaway electron distribution in the runaway vortex regime},
author = {Guo, Zehua and Tang, Xian-Zhu and McDevitt, Christopher J.},
abstractNote = {Generation of runaway electrons (RE) beams can possibly induce the most deleterious effect of tokamak disruptions. A number of recent numerical calculations have confirmed the formation of a RE bump in their energy distribution by taking into account Synchrontron radiational damping force due to RE’s gyromotions. Here, we present a detailed examination on how the bump location changes at different pitch-angle and the characteristics of the RE pitch-angle distribution. Although REs moving along the magnetic field are preferably accelerated and then populate the phase-space of larger pitch-angle mainly through diffusions, an off-axis peak can still form due to the presence of the vortex structure which causes accumulation of REs at low pitch-angle. A simplified Fokker- Planck model and its semi-analytical solutions based on local expansions around the O point is used to illustrate the characteristics of RE distribution around the O point of the runaway vortex in phase-space. The calculated energy location of the O point together with the local energy and pitch-angle distributions agree with the full numerical solution.},
doi = {10.1063/1.5006917},
journal = {Physics of Plasmas},
number = [11],
volume = [24],
place = {United States},
year = {2017},
month = {11}
}

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