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

To improve reliability of pulsed 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 appear in the inner surface of the quartz envelope opposite to metallic reflector inside amplifier. Scanning electron microscopy and X-ray photoelectron spectroscopy data demonstrate that the chemical composition of whitish participant is SiO₂. To understand the thermal damage mechanism of lamp envelope, the plasma channel profiles are captured by a high speed CCD camera. Photographs indicate that the existence of metallic reflector beside silica envelope results in uneven distribution of plasma. The temperature is higher in the region with high plasma density. This leads 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.