The role of recombination in constriction of a positive column of a glow discharge in inert gases

Abstract

The work is aimed at the experimental determination of the role of volume recombination in a positive column of a DC discharge in helium during the transition from a diffuse homogeneous state to a constricted stratified regime under real discharge conditions of high electron and gas temperatures (Te ≈ 2 eV, Tg > 1000 K). The investigation is based on the probe measurements of the wall current determined by the flux of charged particles towards the boundary of a cylindrical discharge tube. The experiments were carried out in helium, neon, and argon in the range of reduced pressures 1.2 - 300 Torr·cm. In heavy inert gases, the transition to a constricted regime is determined by the active loss of charged particles in the volume. In contrast to neon and argon, experiments in helium demonstrated that the role of volume recombination is insignificant during the transition to a constricted regime. The rate of volume losses in helium in real conditions is very low compared to neon and argon. The obtained results allow one to calculate the volume recombination rate by comparing the experimentally measured wall currents with the corresponding numerical calculations within the collision-radiative model.