SUPER-ASHURA KrF LASER DEVELOPMENT

摘要

The super-ASHURA KrF laser aims at a total energy on target of 8 kJ with 12 spatially smoothed and temporally tailored pulses. To achieve this goal, a main amplifier and an optical system for 12 pulse multiplexing with spatial smoothing and pulse shaping functions are being added to the working ASHURA (660 J, six beams) system. The main amplifier (60 cm window aperture, 270 ns duration) is strongly pumped by 16 electron beams to achieve high stage gain and high efficiency at the same time. In short pulse (150 ns) test operations, a significantly improved electron beam deposition efficiency of 29% has been achieved. Further improvement (up to 40%) by correcting the e-beam shape and temporal impedance mismatching will lead to an overall amplifier efficiency (optical output energy/initially stored electric energy) of 4%. Twelve-beam optics for pulse multiplexing is being installed. A one dimensional smoothing effect of the broadband random phase irradiation has been demonstrated. Further pulse compression by 72 pulse multiplexing is also being planned.