Investigation of a low-pressure He-Xe discharge in spot mode

One of the promising candidates for new mercury-free lamps is a low-pressure discharge in a helium-xenon mixture. This discharge with a hot spot on an oxide cathode has been investigated in dc mode. The temperatures of the gas and the cathode surface in the spot vicinity have been measured and used as input parameters for a two-dimensional fluid modelling of the discharge. The model is based on the particle balance equations for the charged particles and excited atoms, Poisson's equation, the energy balance equation for the electrons and a lookup table for the electron transport coefficients and collision rate coefficients determined from a kinetic treatment. The spatial density profiles of the xenon metastable and resonance atoms in front of the spot obtained from the modelling are compared with those measured by laser absorption techniques. The charged particle densities and fluxes in the cathode region and on the cathode surface are discussed.