Deuterium–argon admixture for plasma focus neutron generation

Abstract The plasma pinch generated by plasma focus discharge features a spatially asymmetric ion acceleration due to the rapid change of the localized electromagnetic field. The neutron emission is attributed to deuteron beam interaction at the proximities of the plasma pinch and thermonuclear reaction in the pinch. Neutron is produced by more than the thermonuclear reaction, with two phases of neutron emissions clearly identified to have correlated with at least two different mechanisms. We investigated the impact of a high mass percentage of argon in the deuterium plasma pinch on the resulting neutron emission and the breakdown initiated in the electrode system. The electrical breakdown phenomenon is initiated at the backwall of the electrode system assisted by the surface current tracking of the insulator. At the same pressure with different mass ratios of the deuterium–argon mixture, the breakdown voltage is measured, and the corresponding neutron emission is analyzed. Neutron yield was measured by a calibrated indium activation counter placed at an angle from the axis of the electrodes. At a mass ratio of 50% deuterium and 50% argon, the highest average neutron yield was measured which was (3.0 ± 0.6) × 10 7 neutrons per shot, and an average breakdown voltage of 11.8 ± 1.8 kV and an average energy into the pinch of 139 ± 16 J were calculated. The pure deuterium discharge yielded an average (4.7 ± 0.8) × 10 6 neutrons per shot, while the average breakdown voltage of 12.1 ± 1.6 kV and the average energy into the pinch of 83 ± 17 J were calculated. The 50% argon admixture could increase the energy into the pinch to more than 60%, resulting in more than 5 times higher neutron yield. The ion temperature evaluated from the computation code was 1 keV, inversely proportional to the percent mass of argon. The intriguing plasma focus phenomenon is related to the implosion mechanisms and the plasma instabilities that are strongly affected by the participating ion species.