Mechanism for limiting the repetition frequency of pulses from a copper vapor laser

Measurements are reported of the populations of the copper atom ${}^2D_{5/2}$ levels and of the frequency characteristics of a copper laser utilizing self-terminating transitions, in tubes of diameter 20,27, and 40 mm. It was shown that the optimal repetition frequency was determined not by the relaxation rate of the metastable level but by the plasma recombination rate. In a pure $Cu-Ne$ mixture the recombination took place as a result of ambipolar diffusion, so that a lowering of the optimal repetition frequency from 13-16 to 4-5 kHz was observed on increasing the diameter of the coaxial tubes from 2 to 4 cm. The addition of hydrogen to the $Cu-Ne$ mixture led to an increase in the efficiency of the three-body volume recombination mechanism and to a substantial raising of the optimal repetition frequency.