Edge modeling and simulation of Plasma Injector (Pi3) plasmas with lithium walls

General Fusion works towards commercial power generation through magnetized target fusion (MTF) [M. Laberge, J. Fusion Energy 38, 199–203 (2019)]. Target plasmas in this MTF scheme use a spherical tokamak (ST) generated through coaxial helicity injection by a Marshall gun into a liquid metal cavity, which compresses the plasma for a few milliseconds until the plasma reaches ignition. The plasma injector (Pi3) is a non-compressing experimental device at General Fusion with solid lithium walls used to study and to improve target plasmas. In this work we present results of the edge modeling and simulation of Pi3 plasmas using the UEDGE code [T.D. Rognlien et al., J. Nucl. Mater. 196–198, 347 (1992)]. We evolve the plasma for a few milliseconds to study the effect of neutral hydrogen and neutral and partially ionized lithium on the plasma dynamics and on the mechanisms for energy transport and deposition to the walls. We compare simulated profiles of plasma density and electron temperature to experimental measurements from a movable triple Langmuir probe in Pi3. We also compare simulated hydrogen and lithium line radiation and measurements of a visible camera in Pi3, finding good qualitative agreement between simulation and experiment.