Vol. 13, issue 03, article # 3

Abstract:

High power Ar-Xe laser devices often face the problem of premature termination of laser output power with respect to the pumping pulse. Several reasons, including temperature effects, outgassing of impurities from walls as well as electron induced effects have been discussed. Here, two experiments, elucidating the influence of water vapor contents in the lasing gas mixture on laser output power and laser threshold, and the effect of temperature rise in the laser gas on amplitude and shape of the laser output pulse, have been performed at the Munich Tandem accelerator, using 100 MeV 32S9+ beams for pumping, thus simulating nuclear pumped laser (NPL) experiments at a pumping power density of ~100 W/cm³. To study the influence of water vapor on laser parameters, highly purified 500 mbar Ar gas containing 0.5% Xe was used with well defined amounts of water vapor added. A continuous decrease of laser power was observed with increasing water concentration. A simple model is used to explain the data. Rate constants for quenching the upper level (KQH₂O), and a ratio of the rate constant for electron attachment to water vapor to the total recombination rate of 4 10-9 cm³/s and 6 10-16 cm³, respectively were obtained from this model. A second experiment has been performed, using ultra-high purity laser gases to measure the temperature dependence of laser output. The laser gas mixture, containing of 327 mbar Ar and 3 mbar Xe at room temperature, was pumped using rectangular 50 ms pulses (rise time ~100 ns) of 100 MeV 32S9+ ions. In a pure Ar-Xe mixture, a decrease of laser output power with increasing temperature could be observed. Extreme afterglow lasing, reaching more than 20% of the entire energy in the 50 ms laser output and lasting for more than 20 ms was observed in the temperature range between 400 K and 570 K.