Simulation of Instability Driven Edge Currents with Non-Axisymmetric Resistive Walls in HBT-EP

In experimental magnetized plasmas, currents in the first wall, vacuum vessel, and other conducting structures can have a strong influence on plasma dynamics. These effects are complicated by the 3D nature of device structures, which dictate available current paths. Progress on simulations to study currents flowing in the scrape-off layer during unstable and saturated MHD mode activity in the High Beta Tokamak (HBT-EP) will be presented. The arbitrary geometry, 3D extended MHD code PSI-Tet is applied to study linear and non-linear plasma dynamics in HBT-EP focusing on toroidal asymmetries in the adjustable conducting wall. Comparison of currents and magnetic data from simulations with edge current diagnostics recently installed in HBT-EP will be presented. Comparison between simulations with an experimentally accurate 3D resistive wall, using PSI-Tet, and simulations with an axisymmetric perfectly conducting wall, using NIMROD, will also be presented. Simulations of detailed experimental geometries are enabled by the PSI-Tet code [1], which employs a high order finite element method on unstructured tetrahedral grids generated directly from CAD models.

[1] C. Hansen et al. Phys. of Plasmas 22, 042505 (2015)