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1-Hz Bead-Pellet Injection System for Fusion Reaction Engaged by a Laser HAMA Using Ultra-Intense Counter Beams

Yoshitaka Mori, Yasuhiko Nishimura, Katsuhiro Ishii, Ryohei Hanayama, Yoneyoshi Kitagawa, Takashi Sekine, Yasuki Takeuchi, Nakahiro Satoh, Takashi Kurita, Yoshinori Kato, Norio Kurita, Toshiyuki Kawashima, Osamu Komeda, Tatsumi Hioki, Tomoyoshi Motohiro, Atsushi Sunahara, Yasuhiko Sentoku, Eisuke Miura, Akifumi Iwamoto, Hitoshi Sakagami

Fusion Science and Technology / Volume 75 / Number 1 / January 2019 / Pages 36-48

Technical Paper /

Received:October 13, 2017
Accepted:July 3, 2018
Published:December 8, 2018

The injection and engagement of pellets using laser beam irradiation is one of the key technologies to realize a laser-driven inertial fusion energy (IFE) reactor. We irradiated ultra-intense laser (11 TW: 0.6 J/110  fs  2 beams with a focal intensity of 510 W/cm) in counter configuration on flying 1-mm-diameter deuterated polystyrene beads beyond 600 pellets on an average at 1 Hz and 10 min per cycle for 4 years. An injection system delivers pellets with free-fall that consists of a header for pellet delivery by disk rotation and a detection unit for synchronizing the motion of a pellet for laser engagement in time. During laser irradiation, the free-falling pellet placement was at Δx = 1 mm, Δy = 0.4 mm on a plane perpendicular to the falling direction, and Δz = 0.1 mm in the falling direction at the moment of laser irradiation. Using a two-directional probe shadowgraph system, we succeeded in aligning the pellet-falling position with a laser engagement probability greater than 70%; the probability improved from the previous experiments wherein the probabilities were less than 20%. As a result, the shot probability is 27% for gamma-ray generation resulting from ultra-intense laser-matter interactions and 22% for detection of signals corresponding to fusion neutrons with a maximum yield of 4  10 n/shot. The neutron reaction induced from an integrated system of pellet injector and laser is a decisive step in the research and development of an IFE reactor.