Numerical experiments on anode length optimised neutron yield for a sub kJ plasma focus device

Plasma Focus (PF) device is a source of radiation such as X-rays, electrons, ions and neutrons with deuterium gas due to very fast compression and heating of plasma by self-magnetic force. Published literature shows the numerical neutron yield variation with pressure, inductance, plasma current, scaling laws with neutron. In this paper, anode length influence on neutron yield & other parameters are studied with numerical experiments. Five-phase, Lee model, RADPFV5.15 code is utilized for numerical experiments to analyze the neutron production for a sub kJ PF device (400J, 20kV). Computed results for anode lengths of 12mm (PF1) and 20mm (PF2) are compared with the measured neutron yield and other parameters versus pressure data. Computed maximum neutron yield 2.49 10 * 6 n/shot at 9mbar and 1.29 10 * 6 n/shot at 4mbar are reasonably well agreement with measured 1.9 10 * 6 n/shot at 10mbar and 0.8 10 * 6 n/shot at 3.5mbar for PF1 & PF2, respectively. In a typical PF device operation, it is expected that the neutron yield (Yn) to be same for varied anode length at different pressure values. The higher anode length should be compensated with lower pressure to match both maximum current time (tpeak) and pinch time (tpinch) to get the maximum neutron generation. But, it is not followed by the PF2. The reason seems that, with the use of PF2 (longer anode), the cross sectional area of the channel gets effectively reduced, which accounts for loading of current sheath at comparatively lower operating pressure