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Title: Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas

Abstract

An implicit assumption made in the vast majority of studies of runaway electrons is that they are well confined to a given magnetic flux surface, thus allowing the use of slab or bounce averaged formulations that ignore the spatial transport of runaway electrons. While such an assumption is known to break down in the presence of strong 3D magnetic field perturbations, we show that it can be violated even for an axisymmetric magnetic field under conditions representative of an actively mitigated disrupting plasma. Specifically, the low temperature and large impurity content typical of a post thermal quench plasma are shown to provide a drastic enhancement of the diffusive and convective transport of runaways electrons, where the convective component is found to be dominated by the Ware pinch. This inward convective flux allows runaway electrons to be displaced toward the plasma center, where they are eventually detrapped and reaccelerated, thus focusing populations of runaway electrons in the inner portion of the plasma. The resulting runaway electron distribution is shown to settle into a well-defined spatial eigenmode, whose form is often insensitive to the spatial distribution of the original seed population. The underlying transport processes responsible for determining the width and shapemore » of the spatial runaway electron eigenmode are analyzed under a range of circumstances characteristic of a post thermal quench plasma.« less

Authors:
ORCiD logo [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); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
OSTI Identifier:
1485407
Report Number(s):
LA-UR-18-28325
Journal ID: ISSN 0741-3335
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Name: Plasma Physics and Controlled Fusion; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Magnetic Fusion Energy

Citation Formats

McDevitt, Christopher J., Guo, Zehua, and Tang, Xianzhu. Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas. United States: N. p., 2018. Web. doi:10.1088/1361-6587/aaf4d1.
McDevitt, Christopher J., Guo, Zehua, & Tang, Xianzhu. Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas. United States. doi:10.1088/1361-6587/aaf4d1.
McDevitt, Christopher J., Guo, Zehua, and Tang, Xianzhu. Thu . "Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas". United States. doi:10.1088/1361-6587/aaf4d1.
@article{osti_1485407,
title = {Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas},
author = {McDevitt, Christopher J. and Guo, Zehua and Tang, Xianzhu},
abstractNote = {An implicit assumption made in the vast majority of studies of runaway electrons is that they are well confined to a given magnetic flux surface, thus allowing the use of slab or bounce averaged formulations that ignore the spatial transport of runaway electrons. While such an assumption is known to break down in the presence of strong 3D magnetic field perturbations, we show that it can be violated even for an axisymmetric magnetic field under conditions representative of an actively mitigated disrupting plasma. Specifically, the low temperature and large impurity content typical of a post thermal quench plasma are shown to provide a drastic enhancement of the diffusive and convective transport of runaways electrons, where the convective component is found to be dominated by the Ware pinch. This inward convective flux allows runaway electrons to be displaced toward the plasma center, where they are eventually detrapped and reaccelerated, thus focusing populations of runaway electrons in the inner portion of the plasma. The resulting runaway electron distribution is shown to settle into a well-defined spatial eigenmode, whose form is often insensitive to the spatial distribution of the original seed population. The underlying transport processes responsible for determining the width and shape of the spatial runaway electron eigenmode are analyzed under a range of circumstances characteristic of a post thermal quench plasma.},
doi = {10.1088/1361-6587/aaf4d1},
journal = {Plasma Physics and Controlled Fusion},
issn = {0741-3335},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {11}
}

Journal Article:
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