Spot Mode Operation of a Low-Pressure Helium–Xenon Glow Discharge

The cathode region (CR) of a low-pressure He-Xe discharge with a flat thermionic emitting cathode in spot mode has been experimentally investigated by means of tunable diode laser absorption spectroscopy. Due to the strong inhomogeneity of the spot plasma, a multidimensional consideration of the CR is necessary to obtain correct results. This was achieved by an experimental setup, which provides a space-resolved measurement of the absorption signal. Furthermore, the plasma inhomogeneity was considered in the subsequent analysis of the obtained data too. The gas temperature in the surrounding volume was determined. Furthermore, the spatial density profile of the xenon 6
s
[3/2]
₂
metastable atoms was measured in the vicinity of the spot.