Optimized electrode configuration for various plasma focus gas mixtures

Summary form only given, as follows. The Mather-type 25-kj dense plasma focus (DPF) at the University of Illinois is currently being used to study electrode designs intended to optimize performance with various fusion fuels of interest for space propulsion applications. The DPF device consists of 20x2-/spl mu/f capacitors in parallel arranged in four perpendicular arms (12.5 kJ at 25 keV). The current during the discharge can reach 700 kA (/spl sim/500 kA pinch current). For space propulsion, the DPF operates similarly to other MPD devices, but with the added advantage that, when suitable fuels are used, fusion reactions occur in the plasma that pinches at the tip of the inner electrode, adding energy to the flowing jet gas. This enhances the thrust-to-weight ratio of the thruster. Theory predicts that advanced fuels such as /sup 3/He-D yield high temperature (100 keV) and dense (/spl sim/10/sup 22/ cm/sup -3/) plasmoids when the dimensions of the anode and cathode are optimized. It has already been shown on the University of Illinois' facility that using D/sub 2/ with the suitable electrode dimensions, neutron yields about six times higher than for conventional electrode configuration operating with the same current and total energy were achieved. We report them on the results obtained with a /sup 4/He-D mixture, using electrode dimensions optimized for that mixture. Optimizing the electrode configuration requires matching dimensions with the rundown time of the plasma along the electrode.