THE EFFECTS OF HE ADDITION ON THE PERFORMANCE OF THE FISSION-FRAGMENT EXCITED AR/XE ATOMIC XENON LASER

The intrinsic power efficiency of the atomic xenon laser depends upon the electron density because of the mixing of the laser levels by electron collisions while the electron density in high-pressure particle-beam excited plasmas increases with increasing gas temperature. Therefore, in order to reduce the amount of electron collisional mixing when operating at high-energy loadings (> 100's J/1-atm) mixtures having a high-heat capacity are required. In particle-beam excited Ar/Xe mixtures, which typically yield the highest intrinsic laser efficiencies, increasing the gas pressure to increase the heat capacity is not always practical due to the high-stopping power of the gas mixture. For this reason we have experimentally and theoretically investigated adding He to Ar/Xe mixtures in studies of a fission-fragment excited atomic xenon laser. Adding He increases the heat capacity without appreciably perturbing the favourable kinetics resulting in efficient operation of the laser in Ar/Xe mixtures. We find that when adding He to Ar/Xe mixtures the dominant laser transition switches from 1.73 to 2.03-mu-m without significantly decreasing the efficiency. The laser pulse length also increases, an effect attributed to a lowering of both the electron temperature and gas temperatures.