Development of driver laser system for 0.1-Hz X-ray laser

Ochi, Yoshihiro; Kawachi, Tetsuya; Hasegawa, Noboru; Nagashima, Keisuke; Nishikino, Masaharu; Kishimoto, Maki; Tanaka, Momoko

We have developed a chirped pulse amplification laser with flash lamp pumped zigzag slab Nd:glass amplifiers for pumping the TCE X-ray lasers at 0.1-Hz repetition rate at the Japan Atomic Energy Agency. The laser provided 7 J/1.6 ps main pulse and 1/8 intensity pre-pulse at 1.2 ns before the main pulse. An energy fluctuation at 0.1-Hz operation was 20% (RMS), which was comparable with our present laser using rod amplifiers. The line focus on the target surface was 20 m in the width and 0.8 cm in the length. By using this laser, gain saturated Ni-like silver laser ( = 13.9 nm) with energy output of 1 J was obtained. In this case, the gain coefficient (G) was 41.9 cm up to the plasma length (L) of 0.39 cm, resulting G L = 16.3. The beam divergence of the Ni-like silver laser was 3 mrad. Consequently, the peak spectrum brilliance was estimated to be 10 photons/s/mm/mrad2/0.1%BW.