Development of a plasma-coupled circuit model for MHD simulations of inductive helicity injection

Due to the complexity of current drive mechanisms in inductive helicity injection, numerical simulations are vital to understanding present results and predicting future devices. Numerical simulations of the HIT-SI(3) experiments using Hall-MHD models in the NIMROD [1] and PSI-Tet [2] codes have produced good agreement with experimental observations. However, differences remain in several important quantities (ex. mean current and magnetic profiles). Previously, experimental comparisons directly imposed the observed injector flux and current waveforms. However, such definitions imply a “high-impedance” injector current circuit in contrast to reality. Additionally, observations show significant feedback between plasma dynamics and driven circuit waveforms. Improvements to the injector boundary conditions have been developed to: 1) support “low-impedance” for both the injector flux and current and 2) enable coupling a self-consistent external circuit to the MHD model to provide a complete plug-to-plasma model. Development of these models and results from simulations will be presented, focusing on experimental comparison and validation.

1- K. Morgan et al. Phys. Plasmas 24, 122510 (2017)

2- C. Hansen et al. Phys. Plasmas 22, 042505  (2015)