Anode Shape and Structure Effects on Dense Plasma Focus Neutron Yield
The Dense Plasma Focus (DPF) is a simple Z-pinch device with the ability of producing X-rays and neutrons. Neutron production from a DPF is susceptible to electrical parameters such as voltage and current, as well as mechanical parameters including electrode geometry and insulator sleeve length. Experiments that investigate three different anode geometries on a 4.6 kJ DPF device with a voltage of ~20 kV and a current of ~230kA were carried out. Two anodes with a hemispherical tip, one with and one without a hollow, were explored as well as an anode with a flat tip, hollo, and concentric slits. In order to analyze the pinches produced in these experiments, a neutron activation detector, X-ray PIN diodes, and a series of time-resolved Schlieren probing, were used. Hollow anodes create a higher neutron yield based on recent magnetohydrodynamics simulations that show the extension and dynamics of pinches in the hollow structure. Experimental evidence of extension of the pinch column is shown for the first time using the flat top hollow anode with slits. The maximum neutron yield obtained in these experiments was 1.97E ± 0.1×108 neutrons per pulse which was acquired using the hemispherical hollow anode while hard X-ray emission was observed with the hemispherical solid anode. Based on this analysis, one can conclude that anode with a hollow is optimal for neutron production while one without a hollow is prone to ablation and serves as an X-ray source.