Electromagnetic Design of a Runaway Electron Mitigation Coil Option for ARC and Model Validation on HBT-EP

Electromagnetic modeling for the design of a runaway electron mitigation coil (REMC) on ARC [1] is presented as an optional addition to the baseline disruption mitigation system. Comparison between SPARC and ARC REMC modeling identifies similar normalized induced current performance for a range of disruption timescales. The modeling workflow utilizes ThinCurr, a thin-wall, 3D electromagnetic modeling code, predicting currents and fields in the coupled REMC, plasma, vacuum vessel, and operational coil system [2]. This workflow is validated using current quench-induced REMC currents on HBT-EP, which reach about 15% of the pre-disruption plasma current. The rapid, iterative design process used for the ARC REMC is discussed, including position, resistance, and self-inductance dependencies. A preliminary design composed of a hollow square cross-section coil is proposed. Validation of the workflow using HBT-EP REMC operations will be presented. Good agreement is observed between experiment and modeling for inductively driven REMC currents and field perturbations at Mirnov sensor arrays. The remaining errors are primarily attributed to the challenge of predicting and measuring coil self-inductances, metrology differences, and mispredicted eddy currents. The validation increases confidence in SPARC and ARC REMC predictions.

1. J. Hillesheim, et al., APS DPP 66th (2024) Contributed TO06.00002

2. C. Hansen, et al., Comput. Phys. Commun. 315 (2025) 109713