Kinetic model of the active medium of a He – Ar laser pumped by a hard ioniser

A detailed nonstationary model of a He – Ar laser pumped by a hard ioniser is developed. It is found by numerical simulation that the pumping of the upper laser level is governed either by the three-body recombination of atomic argon ions with electrons or the dissociative recombination of molecular argon ions with electrons, depending on the argon content in a gas mixture. The conversion of dimer molecular argon ions into trimers, the quenching of the upper laser level by neutral atoms, and the spectral line broadening determine the optimum lasing conditions for the total mixture pressure and the partial argon pressure for different excitation conditions. The model adequately describes experiments using electron beam and nuclear pumping. The optimisation of a 1.79-μm nuclear-pumped He – Ar laser in the VIR-2M reactor gave a maximum laser efficiency of 1.2 %.