CRYOGENIC TARGETS AND RELATED TECHNOLOGIES AT ILE OSAKA-UNIVERSITY

Described are two approaches to make cryogenic inertial fusion targets that have a uniform solid or liquid fuel layer inside a spherical hol low fuel capsule. One is to utilize low-density, low-atomic-number pla stic foam to sustain liquid fuel (foam method) and the other is to ini tiate 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 diamete rs of 600-1550 mum and wall thicknesses of 10-50 mum were coated with a normal density plastic layer having thickness of 4-10 mum. These foa m shells were provided for implosion experiments with the Gekko XIII g lass laser system. In the plasma layering process, we examined the fea sibility of the method by performing experiments using krypton gas and liquid nitrogen. A nonuniform solid krypton layer was redistributed i nto a uniform one after a 30 min discharge induced by an external 2.45 GHz microwave field. Experimental results on the heat generation in s hells indicated that this technique can redistribute 10 K solid fuel i nto a uniform layer using intermittent discharges.