Plasma Kinetics in Inert Gas Filled Thermionic Devices

Drift-diffusion and Particle-in-Cell (PIC) simulations of weakly ionized plasmas in novel thermionic devices filled with low-pressure inert gases are performed. The plasma is created by repetitive nanosecoznd pulses and is allowed to decay between the pulses. Modeling indicates that the negative space charge created by electron emission helps in trapping ions in the plasma. This trapping and the low bulk recombination rate result in a relatively long plasma lifetime. Thus, ionizing pulses with relatively low repetition rate and power budget can sustain a plasma which would allow collection of a substantial portion of the thermionically emitted current.

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