Characterizing MHD instabilities and scrape-off-layer currents in HBT-EP using the NIMROD code*

The NIMROD [1] and PSI-Tet [2] codes are being used to validate multiphysics (xMHD+conducting wall) models for the prediction of Scrape-Off-Layer (SOL) currents in tokamaks using high-resolution current, magnetic, and optical diagnostics on the HBT-EP tokamak [3]. Early application of the NIMROD code using a perfectly conducting, circular wall and multiple equilibrium current and pressure profiles to characterize resistive MHD instabilities in the HBT-EP tokamak will be presented. Comparison of predicted signals for linear and nonlinear calculations of non-disruptive mode activity to experimental measurements, including a high-resolution poloidal EUV array, will be shown. Future plans for this project to investigate and validate numerical models for wall-connected currents within the SOL using the diverse, high-resolution diagnostics available on HBT-EP will also be presented. Results from this investigation will be used to validate and/or improve existing models for predicted current dynamics between the plasma and the first wall in ITER and next step devices.

[1] C. Sovinec et al., J. Comput. Phys. (2004)

[2] C. Hansen et al., Phys. Plasmas 22 (2015)

[3] J. Levesque et al., Nucl. Fusion 57 (2017)