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

L. Hesslow, O. Embréus, G. J. Wilkie, G. Papp, T. Fülöp

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number074010
JournalPlasma Physics and Controlled Fusion
Volume60
Issue number7
DOIs
Publication statusPublished - Jun 6 2018

Keywords

  • Fokker-Planck
  • disruption
  • runaway electron
  • tokamak

ASJC Scopus subject areas

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

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