Modeling Plasma-Material Interactions for a Sheared-Flow-Stabilized Z Pinch

A major challenge for any device that could sustain Q = 1 conditions for a substantial time, is the

impact of the edge plasma on the plasma-facing components (PFCs). For Zap’s FuZE and FuZE-Q

devices, the cathode and anode are exposed to plasma for tens of microseconds, leading to

heat and particle fluxes that can result in melting of metallic components and the sublimation of

graphitic materials.

In this work, the heat and particle fluxes to PFCs are derived from 2D MHD whole-device

modeling (WDM). Because the magnetic field is tangential to the surface in these models, only a

small fraction of the Bohm flux is expected to reach the surface. Importantly, it is assumed that

any applied voltage drops across the cathode sheath width. A Green’s function solution to the

semi-infinite 1D heat equation is used to predict the time-dependent surface temperature and

resulting thermal erosion. The model incorporates the effects of prompt redeposition of

sputtered and evaporated particles. Estimates of heat loads, thermal and sputtering erosion are

presented for different plasma-facing components. Also shown are electron emittance models

based on thermionic/Schottky emission, ionization of eroded material, and ion-induced

secondary electron generation.