Generalized collision operator for fast electrons interacting with partially ionized impurities

L. Hesslow, O. Embréus, M. Hoppe, T. C. DuBois, G. Papp, M. Rahm, T. Fülöp

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Accurate modelling of the interaction between fast electrons and partially ionized atoms is important for evaluating tokamak disruption mitigation schemes based on material injection. This requires accounting for the effect of screening of the impurity nuclei by the cloud of bound electrons. In this paper, we generalize the Fokker-Planck operator in a fully ionized plasma by accounting for the effect of screening. We detail the derivation of this generalized operator, and calculate the effective ion length scales, needed in the components of the collision operator, for a number of ion species commonly appearing in fusion experiments. We show that for high electric fields, the secondary runaway growth rate can be substantially larger than in a fully ionized plasma with the same effective charge, although the growth rate is significantly reduced at near-critical electric fields. Furthermore, by comparison with the Boltzmann collision operator, we show that the Fokker-Planck formalism is accurate even for large impurity content.

Original languageEnglish
Article number905840605
JournalJournal of Plasma Physics
Volume84
Issue number6
DOIs
Publication statusPublished - Dec 1 2018

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operators
impurities
collisions
electrons
screening
electric fields
ions
derivation
fusion
injection
formalism
nuclei
atoms
interactions

Keywords

  • Fusion plasma
  • Runaway electrons

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Generalized collision operator for fast electrons interacting with partially ionized impurities. / Hesslow, L.; Embréus, O.; Hoppe, M.; DuBois, T. C.; Papp, G.; Rahm, M.; Fülöp, T.

In: Journal of Plasma Physics, Vol. 84, No. 6, 905840605, 01.12.2018.

Research output: Contribution to journalArticle

Hesslow, L. ; Embréus, O. ; Hoppe, M. ; DuBois, T. C. ; Papp, G. ; Rahm, M. ; Fülöp, T. / Generalized collision operator for fast electrons interacting with partially ionized impurities. In: Journal of Plasma Physics. 2018 ; Vol. 84, No. 6.
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