The effects of He addition on the performance of the fission-fragment excited Ar/Xe atomic xenon laser

Abstract

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/l-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 favorable 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 pm 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.

Comments About Nuclear-Pumped Laser Research in the United States

“…The differences were attributed to a reduction in diatomic absorbing species with increasing temperature and differences in the temperature dependence of the optical absorption cross-sections for NeXe + and Xe 2 + . Later, Kushner and colleagues discussed the effects of He addition on the performance of fission fragment excited Ar/Xe lasers [36]. This was viewed as an important laser system because both Russian and Sandia researchers were studying such systems experimentally.…”

Lasers with Nuclear Pumping

“…The spectra of rare-gas atoms have a number of intensive lines belonging to the transitions (n + 1)p-(n + 1)s (where n ¼ 5, 4, 3, 2 for Xe, Kr, Ar, and Ne, respectively), which end in metastable states (n + 1)s. The efficiency of populating the upper levels (n + 1)p in a recombination-nonequilibrium plasma is very high [80,81], so these transitions are promising in the search for lasing. However, in order to obtain lasing on the transitions (n + 1)p-(n + 1)s in cw mode, a high depopulating rate of (n + 1)s-levels is necessary.…”

“…Single-photon spectrometry is the basis of the method of subthreshold diagnostics of active NPL media, developed at FEI [79,80]. Further, we shall briefly examine the most significant studies dedicated to researching the luminescence characteristics of gas media excited by ionizing radiation.…”

“…To test the model, data obtained from the pumping of Ar-Xe laser with electron beam [69,78] and uranium fission fragments [79] were used. Later on this model was improved and was used to calculate the characteristics of NPLs using mixtures of He (Ne)-Ar-Xe (λ ¼ 1.73, 2.03, 2.63, 3.37 μm) excited by uranium fission fragments [80,81].…”

He–Xe microdischarges: Comparison of simulation results with experimental data

“…Experimental studies of plasma discharges in PDPs are extremely difficult due to the very small cell dimensions and complicated panel structure. 3,5,[10][11][12][13][14][15] As in Meunier, Belenguer, and Boeuf, 5 a Holstein escape factor is used to describe the lengthening of the apparent lifetime of the resonant state Xe*( 3 P 1 ) due to radiation trapping, and the resonance radiation is assumed to be optically thin. Such measurements can also be used for the validation of simulation models.…”