Models of high-power discharges for metal-Xe excimer lasers

Abstract

High-power (∼108 W/l) discharges in metal-doped Xe are modeled for typical metal atom densities of 1015–1017 cm−3 and Xe densities of ∼1020 cm−3, and electron densities of 1014–1017 cm−3 as appropriate for proposed excimer lasers. Na is used as a prototype species, while its properties are varied to indicate some of the changes that could result from the use of different metals. The model includes sixteen excited levels of Na, three ionic species, the excimer levels of NaXe, and Na2. The degree of ionization is determined by collisional multistep excitation and ionization of excited atoms versus dissociative recombination of electrons with Na+2. Steady-state conditions in the positive column are calculated for typical gas temperatures of ∼0.06 eV and electron temperatures Te of 0.3–0.5 eV. The Na population distribution is largely Boltzmann at the electron temperature and the electron density is close to the Saha equilibrium value except at low electron temperatures and very high extracted laser powers. Useful gain and extracted powers of ∼10 MW/cm3 are predicted for the higher Te and Na densities, with the pulse width limited to ∼10−7 sec by gas heating. The model indicates that a metal which produces a deeply bound product state via dissociative recombination could yield a very efficient high-power laser or gain cell.