Numerical investigation of effects of Resonant Magnetic Perturbations on Runaway Electron losses in DIII-D

Post-disruption, high energy runaway electrons (REs) may severely damage plasma facing components. Therefore,controlling the RE impact location is of great importance. Recent experiments in DIII-D¹ showed that externally applied non-axisymmetric magnetic perturbations (RMPs) can change the toroidal phase of the RE impact on the wall, providing a promising way to avoid repeated impacts at the same location. In order to understand the experimental results, simulations have been carried out using the linear, single fluid MHD code MARS-F and the guiding center RE orbit tracing module REORBIT², considering 3D fields due to both MHD instabilities and RMP fields. In experiments, it has been observed that with applied n = 1 RMPs, the preferred toroidal phase of the (2/1) mode (and the resulting RE wetted area) is reliably changed in toroidal phase. This dynamic is captured in simulations by minimizing the total magnetic energy perturbations associated with the tearing instability and the applied RMP. This allows numerical estimate of the mode-locking phase and resulting RE wetted areas. Different configurations of the RMP (such as even and odd parities) are also investigated to guide future experiments.

[1] Claudio Marini, et al, this conference

[2] Yueqiang Liu, et al, Nucl. Fusion 59, 126021 (2019).

Work supported by Department of Energy under Awards: DE-FG02-07ER54917, DE-FC02-04ER54698, and DE-FG02-95ER54309.