Numerical studies of electrode plasma formation and expansion in high power charged particle beam diodes

The current models of the plasma formation processes are relatively simple. Most PIC codes allow for space-charge limited electron emission once an electric-field threshold is exceeded but do not self-consistently model the physics of the cathode surface or the subsequent expansion of the cathode plasma. The model used for ion emission from the anode enables emission once the temperature rise from electron bombardment exceeds a threshold. This anode emission model generally does not self-consistently model the outgassing of the anode and subsequent ionization that precedes plasma formation nor does it treat the expansion. This paper will summarize the relevant literature on anode and cathode plasma formation in high-power diodes with a goal of developing and improving self-consistent dynamic models that describe this formation and expansion of these plasmas that are suitable for PIC codes.