Status of short-pulse KrF amplifier research and development at HILL, Szeged

The small saturation energy density of excimers requires amplifiers of large cross-sections for amplification of short pulses of already medium power. Homogeneous excitation of large volumes of Fluorine-based gas mixtures by discharge pumping is a critical interplay of the properties of both pumping and preionization; generally necessitating an intense, spatially and temporally controlled xray preionization. In the present realization at High Intensity Laser Laboratory (HILL) the stringent intensity requirements of preionization are fulfilled by reducing the pulse duration of the x-ray flash to ~16 ns, and by positioning the x-ray source in the near vicinity of the active volume. By proper choice of the positions of two cylindrical x-ray guns the spatial distribution of preionization can be tuned to (and around) the optimum distribution giving a practical method to compensate for eventual inhomogenities of the E-field of excitation and to tune the discharge to the desired geometry. In this way the realization of a KrF excimer amplifier of ~5 x 4 cm2 cross-section is presented.