Atomic Model Calculations of Gain Saturation in the 46.9 nm Line of Ne-like Ar

Abstract

The gain saturation in the 46.9 nm line of the Ar+8 laser is analyzed using an atomic kinetics code. The dependence of the gain (G) on the electron kinetic temperature (Te) in the region (50 -150 eV) is calculated in the quasi steady-state approximation for the different values of the electron density (Ne) and the plasma radius (rpl). The influence of radiat on trapping, ion random and mean velocities, Stark line broadening and refraction losses on the gain saturation is taken into consideration. For rpl = 150-600 μm, the amplplication (G > 0 cm-1) exists in the large temperature/density domain (Te = 60-150 eV, Ne = 0.5-10 × 1018 cm-3). However, the value Gs ∼ 1.4 cm-1 required for the gain saturation at the typical plasma length Lpl ∼ 15 cm is reached in the extremely narrow density regions at the high temperatures. The saturation is reached for rpl = 600 μm at Tse = 150 eV in the region Nse = 1.8-2 × 1018 cm -3, for rpl = 300 μm at Tse = 125 eV and Nse = 2.5-3 × 1018 cm-3, and for rpl = 150 μm at Tse = 110 eV and Nse = 3-4 × 1018 cm-3. The broadest density region (Nse = 2 -8 × 1018 cm-3) is predicted for the narrowest column (rpl = 150 μm) at the highest temperature (Tse = 150 eV). The operation in the broadest density region Nse, should make easier achievement of the gain saturation in the experiments.