Kinetics of high pressure argon-helium pulsed gas discharge

Abstract

Simulations of a pulsed direct current discharge are performed for a 7% argon in helium mixture at a pressure of 270 Torr using both zero- and one-dimensional models. Kinetics of species relevant to the operation of an optically pumped rare-gas laser are analyzed throughout the pulse duration to identify key reaction pathways. Time dependent densities, electron temperatures, current densities, and reduced electric fields in the positive column are analyzed over a single 20 μs pulse, showing temporal agreement between the two models. Through the use of a robust reaction rate package, radiation trapping is determined to play a key role in reducing Ar(1s5) metastable loss rates through the reaction sequence Ar(1s5)+e−→Ar(1s4)+e− followed by Ar(1s4)→Ar+ℏω. Collisions with He are observed to be responsible for Ar(2p9) mixing, with nearly equal rates to Ar(2p10) and Ar(2p8). Additionally, dissociative recombination of Ar2+ is determined to be the dominant electron loss mechanism for the simulated discharge conditions and cavity size.