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arXiv · 1501.04735

Mechanism of runaway electron beam formation during plasma disruptions in tokamaks

S. S. Abdullaev·K. H. Finken·K. Wongrach·M. Tokar·H. R. Koslowski·O. Willi·L. Zeng·the TEXTOR team
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Abstract

A new physical mechanism of formation of runaway electron (RE) beams during plasma disruptions in tokamaks is proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode number magnetohydrodynamic (MHD) modes. It is conjectured that the runaway electron beam is formed in the central plasma region confined inside the intact magnetic surface located between $q=1$ and the closest low--order rational magnetic surfaces [$q=5/4$ or $q=4/3$, \dots]. It results in that runaway electron beam current has a helical nature with a predominant $m/n=1/1$ component. The thermal quench and current quench times are estimated using the collisional models for electron diffusion and ambipolar particle transport in a stochastic magnetic field, respectively. Possible mechanisms for the decay of the runaway electron current owing to an outward drift electron orbits and resonance interaction of high--energy electrons with the $m/n=1/1$ MHD mode are discussed.

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S. S. Abdullaev, K. H. Finken, K. Wongrach, M. Tokar, H. R. Koslowski, O. Willi, L. Zeng, the TEXTOR team. 2015-04-27. Mechanism of runaway electron beam formation during plasma disruptions in tokamaks. https://doi.org/10.1063/1.4919253

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