Continuum kinetic investigation of effects of ion impact secondary electron emission on sheath formation near Z-pinch electrodes*

Understanding the plasma-material interactions at the biased electrode surfaces of Z-pinch thermonuclear fusion reactors is vital to better inform electrode design. Previous simulation results suggest that high energy, sheath-accelerated ions, despite being fewer in number, may induce significant secondary electron emission, especially so at the cathode. We implement a well-benchmarked model of ion impact secondary electron emission as a boundary condition for the Vlasov solver in the code Gkeyll. We simulate an electrostatic proton-electron plasma to examine how plasma sheath formation changes with bias potential when including ion impact electron emission. The secondary electron emission is hypothesized to increase the saturation current as the electric potential bias increases. At higher bias potentials, the large secondary electron yield near the cathode may result in a possible sheath reversal or dynamic sheath instabilities. We present results for various wall materials.