Enhanced efficiency from a Xe excimer barrier discharge lamp employing short-pulsed excitation

We have measured the efficiency and spatial characteristics of output radiation as a function of fill pressure for a Xe excimer lamp employing a short voltage pulse (approximately 100 ns) excitation circuit, and compared the results with those obtained using conventional AC (ie. sinusoidal voltage waveform). When using pulsed excitation, VUV output is obtained from a homogenous discharge at efficiencies which increase linearly with Xe pressure in the range 50-750 torr up to 3.2× the maximum efficiency obtained when using AC. When using AC excitation, the efficiency saturates with increasing pressure >350 torr for which pressures the discharge appearance is altered from a diffuse discharge to one which is comprised of stochastic or stationary filaments. We have also recorded discharge spectra which highlight the different character of the homogenous and filamented types of discharges. It is deduced that the enhanced efficiency arises due to the capability of pulsed excitation to produce a homogenous (glow-like) discharge at higher pressure, which brings about more optimal electron density and temperature conditions for exclusively exciting Xe metastables than possible using AC. We attribute the homogenizing effect of short-pulsed excitation to the rapid rate at which the applied E-field increases to the necessary value for homogenous discharge breakdown to proceed at a faster rate than the formation of filaments.