High density implosion experiments using GEKKO XII glass laser system

Gekko XII 1.053-μm Nd glass laser system has been constructed to produce output energy 20kJ at Ins and peak power 40TW at 0.Ins for the inertial confinement fusion experiments. GEKKO XII has twelve laser amplifier chains whose output aperture is 35cm in diameter. The output beams are focused onto the target by using F/3, f=1050mm aspherical lenses. The spot size at focus plane is about 60μm in diameter. Several types of targets such as ablative, explosive and Cannonball were used for the implosion experiments. The short pulse (100ps) implosion experiments by GEKKO XII were performed in order to study the neutron yield dependence on target structures using the Cannonball target with two, four and twelve holes on the outer tamper as well as usual ones. When the neutron yield was plotted against the irradiated laser energy per fuel pellet mass, the Cannonball target showed higher neutron yield than any other simple targets. The highest DT neutron yield of 4x10/sup 10/ was observed at the irradiated laser power of 25TW. The two-hole Cannonball showed the highest implosion symmetry. The Cannonball target had the higher specific neutron yield. The ion temperature estimated from the neutron time-of-flight reached up to 10keV