HEATING UNIFORMITY OF A MICROWAVE-DISCHARGE PLASMA TO REDISTRIBUTE A SOLID-FUEL LAYER INSIDE A CRYOGENIC TARGET FOR INERTIAL CONFINEMENT FUSION

In the plasma layering technique, a microwave discharge plasma is turn ed on in the void of a nonuniform solid fuel layer inside a cryogenic laser fusion target to redistribute the nonuniform layer into a unifor m one. The heating uniformity of the plasma initiated by a one-dimensi onal electric field was examined experimentally and theoretically by m aking a glow discharge in a quartz shell located in a strong microwave field at room temperature. The heating uniformity on the inner surfac e of the shell was estimated by measuring the surface temperature of t he shell. When the frequency of the external electric field was 2.45 G Hz, the resultant measured heating uniformity at the gas density of <0 .7 g/m(3) should be sufficient to obtain a uniform solid fuel layer fo r laser implosion experiments. At higher gas densities, the heating un iformity was insufficient because of the nonuniform distribution of th e plasma. Countermeasures to improve the uniformity are discussed. (C) 1995 American Vacuum Society.