Exciplex emission induced by nanosecond-pulsed microdischarge arrays operating at high repetition rate frequency

Arrays of microhollow cathode discharges or cathode boundary layer discharges were operated in krypton?chlorine mixtures resulting in an intense ultraviolet emission at 222?nm. It was demonstrated that nanosecond duration pulses applied at high repetition frequency allowed one to simultaneously ignite and sustain discharges inside all the microcavities of the arrays without using any resistive ballast. Self-repelling properties of adjacent plasmas expanding onto the cathode surface for the negative polarity part of the high-voltage pulses were demonstrated, resulting in a self-limitation of the available cathode surface for an individual microdischarge. Spectroscopic investigations allowed us to determine the gas temperature and evolution of the 222?nm band intensity versus the partial pressures and deposited power. Optimum partial pressure ranges for chlorine and krypton were 0.2?0.8?mbar and 50?70?mbar, respectively. The 222?nm band intensity increased linearly with the deposited energy per pulse and the pulse repetition frequency provided that the mean deposited energy was lower than 7?W. Above this value a cooling of the device should be implemented.