Self-consistent simulation of resistive kink instabilities with runaway electrons

TL;DR

This paper introduces a new fluid simulation model for runaway electrons in tokamaks, capturing their interaction with plasma instabilities and providing insights into electron loss mechanisms relevant for ITER.

Contribution

A novel fluid-based model for runaway electrons integrated into M3D-C1, enabling self-consistent simulation of plasma instabilities involving runaway electrons.

Findings

Runaway electrons are largely lost during kink instabilities.

Plasma current shifts from runaway to Ohmic current.

Simulation results agree well with experimental data.

Abstract

A new fluid model for runaway electron simulation based on fluid description is introduced and implemented in the magnetohydrodynamics code M3D-C1, which includes self-consistent interactions between plasma and runaway electrons. The model utilizes the method of characteristics to solve the continuity equation for the runaway electron density with large convection speed, and uses a modified Boris algorithm for pseudo particle pushing. The model was employed to simulate magnetohydrodynamics instabilities happening in a runaway electron final loss event in the DIII-D tokamak. Nonlinear simulation reveals that a large fraction of runaway electrons get lost to the wall when kink instabilities are excited and form stochastic field lines in the outer region of the plasma. Plasma current converts from runaway electron current to Ohmic current, and get pinched at the magnetic axis. Given the good agreement with experiment, the simulation model provides a reliable tool to study macroscopic plasma instabilities in existence of runaway electron current, and can be used to support future studies of runaway electron mitigation strategies in ITER.