Spot mode operation of a helium-xenon discharge for lighting

A dc low-pressure discharge in a helium-xenon mixture with the cathode spot on a flat oxide cathode has been investigated. The temperature of the cathode surface in the vicinity of the spot was determined experimentally. Furthermore, the gas temperature and the spatial density profile of the xenon 1s5 metastable atoms were measured in front of the spot. A fluid model was applied to determine the particle densities and fluxes in the cathode region. This model comprises the particle balance equations for the charged particles and metastable atoms, Poisson’s equation, the energy balance equation for the electrons and a lookup table for the electron transport coefficients and collision rates determined from a kinetic treatment.