Effects of the Reflector Design on the Flash Lamps Developed for the LMJ

Summary form only given. When operating the LIL, which is the prototype of the LMJ, we have observed an unexpected behaviour of several flash lamps after a few hundreds of shots. A whitening appeared near the anode, constituted of a deposition of SiO
₂
molecule in the inner part of the quartz tube. An investigation of the performance of these lamps was performed in terms of the emitted spectrum. We have shown that the pollution is not yet enough to affect the pumping efficiency of the lamp: the emitted light is only diffused. Nevertheless, because we need to guarantee their behaviour for thousands of shots, we recently started experiments in order to understand the whitening, and to intent to suppress it. In this paper, we present these studies. In particular, we show that the reflector design has a strong influence on the plasma formation inside the lamp. Photographs of the lamp discharge indicate that the geometry of the system lamp-reflector influences the homogeneity of the plasma. We think that regions where there are high plasma densities contribute to the whitening. We are carrying-on experiments with a full-scale LMJ amplifier prototype to test the new reflector design.