POPULATION-INVERSION IN A RECOMBINING HELIUM PLASMA MIXING WITH HYDROGEN MOLECULAR GAS IN A TPD-I MACHINE

A high potentiality of plasma cooling and its mechanism are theoretically revealed for a helium plasma which comes into contact with hydrogen molecular gas in the TPD-I machine. The stationary population inversion between the levels n=2 and 3 of the He+ ion, which is due to mixing of the stationary high-temperature helium plasma and the hydrogen molecular gas, is simulated and discussed in comparison with cooling due to the mixing of the plasma and the atomic hydrogen gas. The calculation also shows that the gain per unit length of the He II 164 nm line is ∼ 2 cm-1 for the laser oscillation under optimum initial helium plasma (Te ∼ 30 eV and ne ∼ 3.5 × 1016 cm-3) contacted with hydrogen molecular gas at a pressure of 0.1 Torr. © 1990 The Japan Society of Applied Physics.