Computational study of capacitively coupled high-pressure glow discharges in helium

Abstract—The structure of a capacitively coupled high-pressure glow (HPG) discharge in high-purity helium is investigated using a detailed one-dimensional modeling approach. Impurity effects are modeled using trace amounts of nitrogen gas in helium. Average electron temperatures and densities for the HPG discharge are sim-ilar to their low-pressure counterpart. Helium-dimer ions domi-nate the discharge structure for sufficiently high-current densities, but model impurity nitrogen ions are found to be dominant for low-discharge currents. Helium dimer metastable atoms are found to be the dominant metastable species in the discharge. The high collisionality of the HPG plasma results in significant discharge po-tential drop across the bulk plasma region, electron Joule heating in the bulk plasma, and electron elastic collisional losses. High col-lisionality also results in very low ion-impact energies of order 1 eV at the electrode surfaces. Index Terms—High-pressure glow (HPG) discharge, compu-tational modeling, capacitively coupled helium plasma, plasma impurity effects. I