Effect of Anode Shapes on Neutron Emission from a Repetitive Plasma Focus Device

Summary form only given. The conventional tapered anode of the NX2 repetitive plasma focus device has been changed to two other shapes (straight and spherical) to investigate the effect of anode shape on neutron emission characteristics of the device. An average total neutron yield (averaged over 30 shots) is measured for these three different anode types at various combinations of deuterium filling gas pressures and at different repetition rates. The newly designed beryllium counter and He proportional counter are used for estimation of neutron yield for repetitive operation of the NX2 plasma focus device. The time resolved neutron emission characteristics of the devices under different operating conditions are measured using two PMT based plastic scintillator detectors located at different radial distances from the anode axis. It is found that there is no significant difference in the average neutron yield (typically of the order of 10 s neutrons per shot) for different anode shapes for plasma focus operating at 0.1 Hz. However the pressure at which the maximum neutron yield occurs depends on the anode shape. The anode with spherical tip shows the most stable neutron emission with consistently good neutron yield over a much wider pressure range than the other anode shapes. For the straight cylindrical anode the average neutron yield was found to decrease with increasing shot repetition frequency from 0.03 to 1 Hz. The characteristics of the time resolved neutron emission for these three anode shapes are presently being analyzed and will be presented.