INFLUENCE OF INSULATOR CONTAMINATION BY COPPER EVAPORATION ON NEUTRONYIELD IN A LOW-ENERGY PLASMA-FOCUS

Deterioration of neutron yield in a low-energy plasma focus operated b y a single 32 muF, 15 V, (3.6 kJ) capacitor is observed. When the cumu lative discharge energy over successive shots across an insulator slee ve approaches 1.6 MJ, the neutron yield from the device starts deterio rating. The insulator sleeve, when examined, is found to have a approx imately 3 mum thick layer of copper desposit. The contaminated sleeve surface appears rough with a grain-type structure. It is therefore con cluded that the degradation of neutron yield in our low-energy device occurs due to Cu deposit on the insulator sleeve surface. The situatio n may improve if low-sputtering-rate conductors are employed for the e lectrodes of the device.