A long pulse discharge excited ArF laser

An X-ray preionised, discharge excited ArF excimer laser, lambda = 193 nm, has been studied in the long pulse regime. The laser performance is found t o be primarily dependent on the discharge stability, and therefore, on the gas composition, preionization timing and the pumping power. Using X-ray pr eionization and prepulse-mainpulse excitation, laser pulselengths of up to 120-ns full-width at half-maximum at 4 mJ/l are obtained by decreasing the partial pressures of the active ingredients, F-2 and Ar, and using Ne as a buffergas. This is almost six times as long as usual for discharge excited ArF lasers.