Conditioning of the Sparky III Dense Plasma Focus for Optimization of Neutron Yield

The Sparky III dense plasma focus (DPF) at the University of Nevada, Reno is a repetition-rated, low-inductance, 220 kA driver that produces neutrons via D-D fusion. Collaborative experiments with the Naval Research Laboratory on Sparky III show that maximum neutron yields are only achieved after a set of conditioning shots are performed. These shots condition the electrodes and optimizes the DPF performance – a common procedure in other DPF drivers. Residual gas analysis (RGA) and time-integrated optical emission spectroscopy (OES) are used to diagnose the mechanisms that affect neutron yield over the course of a conditioning run. Results of the RGA and spectra indicate a correlation between a reduction in impurities, such as water vapor and its fragments, after each set of conditioning shots and an overall enhancement of neutron yield. Neutron bubble detector dosimeters, time-of-flight detectors, and Rogowski coil current measurements corroborate these results over the conditioning run. A complete conditioning run provides an average optimized neutron yield per shot of about 4 x 10⁷ neutrons and stronger plasma pinching behavior as observed in current and X-ray measurements.