Microwave conditioned dc discharges for excitation of rare-gas-halide lasers

Discharge-pumped rare-gas halide (RGH) lasers have undergone extensive development during the last five years. Applications of these lasers in systems requiring pulse energies of several joules and repetition rates of up to one kilohertz are now under consideration. Yet there remain several unsolved problems with discharge-pumped RGH lasers which limit their applicability in systems requiring long operating lifetimes. The switch used to control the current applied to the discharge is one of these problems. Other problem areas include impurities, which can reduce the performance of RGH lasers, and stable operation, which requires a good preionization scheme. A number of approaches to solve these problems are under investigation. In the following report we outline in more detail the nature of these problems. We discuss possible solutions based on microwave excited discharge technology and actual experiments that have been performed applying these methods. The application of microwave techniques to RGH laser technology is particularly appealing because of the advanced state of microwave devices. High-power (multiple megawatt) sources in the 1-10 GHa range with microsecond pulse lengths and kilohertz repetition rates are available. Experimental devices have demonstrated gigawatt power levels. Transport of these high-power levels can be accomplished using standard techniques.