Role of Kinetic Instability in Runaway-Electron Avalanches and Elevated Critical Electric Fields

Chang Liu, Eero Hirvijoki, Guo Yong Fu, Dylan P. Brennan, Amitava Bhattacharjee, Carlos Paz-Soldan

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

The effects of kinetic whistler wave instabilities on the runaway-electron (RE) avalanche is investigated. With parameters from experiments at the DIII-D National Fusion Facility, we show that RE scattering from excited whistler waves can explain several poorly understood experimental results. We find an enhancement of the RE avalanche for low density and high electric field, but for high density and low electric field the scattering can suppress the avalanche and raise the threshold electric field, bringing the present model much closer to observations. The excitation of kinetic instabilities and the scattering of resonant electrons are calculated self-consistently using a quasilinear model and local approximation. We also explain the observed fast growth of electron cyclotron emission signals and excitation of very low-frequency whistler modes observed in the quiescent RE experiments at DIII-D tokamak. Simulations using ITER parameters show that by controlling the background thermal plasma density and temperature, the plasma waves can also be excited spontaneously in tokamak disruptions and the avalanche generation of runaway electrons may be suppressed.

Original languageEnglish (US)
Article number265001
JournalPhysical review letters
Volume120
Issue number26
DOIs
StatePublished - Jun 28 2018

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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