Influence of the 3He isotope on the output parameters of theHe-Kr hollow cathode laser

Abstract

The influence of the 3He isotope as a buffer gas on theoperating characteristics of the He-Kr hollow cathode laser is studied. Acomparison of the laser output power and gain on the KrII 469.4 nm andKrII 431.8 nm lines in 3He-Kr and 4He-Kr gas mixtures is made andan increase of 33% is observed in the case of the 3He-Kr gas mixture.A simple qualitative analysis of the plasma kinetics shows that theobserved increase of the laser output parameters is due to the increasedrate constant for the excitation transfer reaction and the increaseddensity of the He(2 3S1) metastable atoms and Kr ground state ions.The main reasons for this are the higher mean relative velocity of thecolliding particles and the higher rate of electron cooling in 3He-Krplasma.Peak output powers of 10 W and 1.5 W and small signal gains over thelosses of 85% m-1 and 64% m-1 are measured for the blue andviolet lines, respectively, from a 21 cm active length at 17.5 kPa 3Hepressure, 17 Pa Kr pressure and 96 A peak current. These values aresignificantly higher compared to earlier investigations. The operatingdischarge conditions are enlarged considerably; up to 21 kPa He pressureand 100 A peak current. The laser design chosen contributes to theachievement of this goal.