Two-fluid (plasma-neutral) Extended-MHD simulations of spheromak configurations in the HIT-SI3 experiment with PSI-Tet*

A self-consistent, two-fluid (plasma-neutral) dynamic neutral model has been implemented into the 3-D, Extended-MHD code called PSI-Tet. A monatomic, hydrogenic neutral fluid reacts with an MHD plasma fluid in this model. Density, momentum, and energy are evolved for both the plasma and neutral species. The implemented plasma-neutral model in PSI-Tet is used to simulate decaying spheromak configurations in the HIT-SI3 experimental geometry, which are compared to two-photon absorption laser induced fluorescence (TALIF) measurements. Validation results between TALIF measurements and PSI-Tet simulations with the implemented dynamic neutral model will be presented. Preliminary plasma-neutral simulations of HIT-SI3 spheromak plasmas sustained with steady, inductive helicity injection (SIHI) will be presented. Lastly, comparisons between plasma density measurements made with a new tomography diagnostic system and plasma-neutral simulations of driven HIT-SI3 plasmas will be presented, and potential benefits of possible extensions of the plasma-neutral model will be discussed.