Cryogenic targets and related technologies at ILE Osaka University

Abstract

Described are two approaches to make cryogenic inertial fusion targets that have a uniform solid or liquid fuel layer inside a spherical hollow fuel capsule. One is to utilize low-density, low-atomic-number plastic foam to sustain liquid fuel (foam method) and the other is to initiate a glow discharge in the void of a solid fuel layer to symmetrize the solid layer (plasma layering method). In the foam method, we have successfully made a foam shell with a gas barrier to prevent the fuel from evaporation by means of density-matched emulsion method followed by an interfacial polycondensation method. Foam shells having diameters of 600–1550 μm and wall thicknesses of 10–50 μm were coated with a normal density plastic layer having thickness of 4–10 μm. These foam shells were provided for implosion experiments with the Gekko XII glass laser system. In the plasma layering process, we examined the feasibility of the method by performing experiments using krypton gas and liquid nitrogen. A nonuniform solid krypton layer was redistributed into a uniform one after a 30 min discharge induced by an external 2.45 GHz microwave field. Experimental results on the heat generation in shells indicated that this technique can redistribute 10 K solid fuel into a uniform layer using intermittent discharges.