Title: Spatial Transport of Runaway Electrons in Axisymmetric Tokamak Plasmas

Journal Article · · Plasma Physics and Controlled Fusion
ORCiD logo [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
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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.

Research Organization:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1485407
Report Number(s):
LA-UR--18-28325
Journal Information:
Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 2 Vol. 61; ISSN 0741-3335
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English

References (29)

On the relativistic large-angle electron collision operator for runaway avalanches in plasmas journal January 2018
Generalized collision operator for fast electrons interacting with partially ionized impurities journal November 2018
Plasma Transport in Toroidal Confinement Systems journal January 1972
Runaway electrons and the evolution of the plasma current in tokamak disruptions journal October 2006
Phase-space dynamics of runaway electrons in tokamaks journal September 2010
Theory of runaway electrons in ITER: Equations, important parameters, and implications for mitigation journal March 2015
On the inward drift of runaway electrons during the plateau phase of runaway current journal March 2016
Lifetime and universal distribution of seed runaway electrons journal November 2017
Numerical simulation of runaway electrons: 3-D effects on synchrotron radiation and impurity-based runaway current dissipation journal May 2018
Control of runaway electron energy using externally injected whistler waves journal March 2018
Monte Carlo evaluation of transport coefficients journal January 1981
Relativistic limitations on runaway electrons journal June 1975
Chapter 3: MHD stability, operational limits and disruptions journal June 2007
Runaway electron drift orbits in magnetostatic perturbed fields journal March 2011
Runaway electron confinement modelling for rapid shutdown scenarios in DIII-D, Alcator C-Mod and ITER journal May 2011
Control and dissipation of runaway electron beams created during rapid shutdown experiments in DIII-D journal July 2013
Stability analysis of runaway-driven waves in a tokamak journal March 2015
Formation of hot ion populations in fusion plasmas by close collisions with fast particles journal March 1993
Analysis of shot-to-shot variability in post-disruption runaway electron currents for diverted DIII-D discharges journal July 2012
Numerical characterization of bump formation in the runaway electron tail journal January 2016
Relation of the runaway avalanche threshold to momentum space topology journal January 2018
Theory of Two Threshold Fields for Relativistic Runaway Electrons journal April 2015
Effect of Partially Screened Nuclei on Fast-Electron Dynamics journal June 2017
Role of Kinetic Instability in Runaway-Electron Avalanches and Elevated Critical Electric Fields journal June 2018
Pinch Effect for Trapped Particles in a Tokamak journal July 1970
Electron Heat Transport in a Tokamak with Destroyed Magnetic Surfaces journal January 1978
On the inward drift of runaway electrons during the plateau phase of runaway current text January 2016
Effect of partially-screened nuclei on fast-electron dynamics text January 2017
On the relativistic large-angle electron collision operator for runaway avalanches in plasmas text January 2017

Cited By (1)

Avalanche mechanism for runaway electron amplification in a tokamak plasma journal April 2019

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