Maintenance of a gas breakdown in argon using 10.6-μ cw radiation

An experimental study on a sustained optical discharge in argon was made. The discharge was initiated by using the high-power radiation from a pulsed CO2 laser and was maintained by using the 10.6-μ radiation from a low-power cw laser. An extensive pressure range, where the discharge can be maintained indefinitely, is found to exist. The discharge exhibits four distinct characteristics in the pressure range 2–17 atm. It is also found that the minimum cw power required to maintain the discharge is several orders of magnitude smaller than the power to initiate it and has a p−2 dependence on the gas pressure at low pressures. This dependence came from the ambipolar diffusion losses. An electron production and loss rate balance equation is found to adequately describe this minimum maintenance power dependence on the gas pressure.