Modeling the effect of wall asymmetry on MHD instabilities and scrape-off-layer currents in HBT-EP

The NIMROD [1] and PSI-Tet [2] codes are used to validate multiphysics models for the prediction of resistive MHD mode structures and Scrape-Off-Layer (SOL) currents in tokamaks using high-resolution current, magnetic, and optical diagnostic data from the HBT-EP tokamak [3]. Available signals are used to constrain equilibrium profiles using linear calculations. With added limiters, efforts to reproduce non-disruptive, saturated, nonlinear mode activity as observed in HBT-EP is underway. Comparison of simulated signals to experimental measurements, including poloidal and tangential EUV arrays, will be shown. Applications to creating a self-consistent picture of internal MHD instability structures and sawtoothing activity will be discussed. Effects of 3D wall resistivity are investigated within NIMROD and compared to results from PSI-Tet, which captures the 3D wall geometry. Plans to validate numerical models for wall-connected currents within the SOL using the diverse, high-resolution diagnostics on HBT-EP will also be presented, with applications for improving models of 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 (2015)

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