Modelling of the parametric behaviour of a self-heated copper vapour laser: Issues governing the thermal runaway behaviour of the plasma tube wall temperature

A computer model has been used to simulate the discharge kinetics and parametric behaviour of a self-heated copper vapour laser for a wide range of optimum and non-optimum conditions. The results indicate that the ground state copper density and the peak electron temperature are the two most important parameters that affect laser performance. The results also confirm the existence of a threshold wall temperature (or threshold copper density) above which the plasma tube becomes thermally unstable with respect to the deposited electrical power, the wall temperature and the copper density, ultimately leading to thermal runaway. At low pulse repetition frequency (prf<8kHz), the thermal instability restricts the copper density (and laser output power) to values well below optimum.