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

Laser operation on the Au-II 282.3 nm ultraviolet transition is obtained using a high-voltage segmented hollow-cathode discharge tube. The metal vapor is produced by means of cathode sputtering. A small amount of argon is added to the helium buffer gas in order to achieve higher sputtering yield. Measurements of the laser power and small signal gain indicate that the optimal partial concentration of argon is in the range of 0.25%-0.75%. Quasi-continuous wave output power of 100 mW is obtained from a 34-cm-long active region while the highest small-signal gain is 52% m Ϫ1. To explain the basic features of the laser operation we present a model of the segmented hollow-cathode discharge. All the discharge characteristics are calculated in a self-consistent way except the temperature of slow electrons. The trajectories of fast electrons emitted from the cathode are followed by Monte Carlo simulation. Rate equations of ion, metastable and metal atom densities are solved in the negative glow, while another Monte Carlo code is applied for the fast heavy particles in the cathode sheath. The spatial distribution of the gas temperature and the thermalization of sputtered metal atoms are calculated as well. The laser characteristics predicted by the model are in reasonable agreement with the experimental results.

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