Thermal damage mechanism of xenon lamp silica envelope during high-power discharge

To improve the reliability of xenon lamps in optical amplifier of inertial confinement fusion (ICF) facility, high power xenon lamps were tested with the power modules similar to NIF facility in US. Though operating at a relatively safe energy loading factor of 0.2 or so, unexpected behavior of some lamps was observed while peak power value of discharge pulse was higher than 300 mega watts. Milky white participants appeared in the inner surface of the quartz envelope opposite to metallic reflector inside amplifier. Scanning electron microscopy and X-ray photoelectron spectroscopy data demonstrated that the chemical composition of whitish participant was SiO₂. To understand the thermal damage mechanism of the lamp envelope, the plasma channel profiles were captured by a high speed CCD camera. The photographs indicated that the existence of metallic reflector beside silica envelope resulted in an uneven distribution of plasma. The temperature was higher in the region with high plasma density. This leaded to local evaporation of silica glass and the whitening of quartz envelope. The results are helpful to optimize the design of discharge circuit of power module and reflector of amplifier of ICF facility. (authors)