Fast ignitor research at the Institute of Laser Engineering, Osaka University

The physics element relevant to the fast ignitor in inertial confinement fusion has been extensively studied. Laser-hole boring with enormous photon pressures into overcritical densities was experimentally proved by density measurements with XUV laser probing. Ultra-intense laser interactions at a relativistic parameter regime were studied with a 50-TW glass laser system and a 100-TW glass laser system synchronized with a long pulse laser system. In the study of relativistic laser beam propagation in a 100-μm scale-length plasma, a special propagation mode (super-penetration mode) was observed, where the beam propagated into overdense regions close to the solid target surface. At the super-penetration mode, 20% of the laser energy converted to energetic electrons toward the target inside, while the coupling efficiency was 40% without the long scale-length plasmas. The high-density energetic electron transport and heating of solid material was also studied, indicating beamlike propagation of the energetic ...