Effect of partially ionized impurities and radiation on the effective critical electric field for runaway generation

We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2018-05
Main Authors: Hesslow, Linnea, Embréus, Ola, Wilkie, George J, Papp, Gergely, Fülöp, Tünde
Format: Article
Language:English
Subjects:
Bremsstrahlung
Critical field (superconductivity)
Decay rate
Electric fields
Electron density
Free electrons
Impurities
Kinetic equations
Plasma
Tokamak devices
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the classical Connor-Hastie field, and even exceeds the value obtained by replacing the free electron density by the total electron density (including both free and bound electrons). Using a kinetic equation solver with an inductive electric field, we show that the runaway current decay after an impurity injection is expected to be linear in time and proportional to the effective critical electric field in highly inductive tokamak devices. This is relevant for the efficacy of mitigation strategies for runaway electrons since it reduces the required amount of injected impurities to achieve a certain current decay rate.
ISSN:2331-8422
DOI:10.48550/arxiv.1802.00717