Study of soft X-rays from depleted uranium assisted pre-ionized plasma in a low energy Mather type plasma focus device

Abstract

This thesis describes the experimental investigations of the soft X-ray emission and the plasma dynamics in a Mather type plasma focus device operated in different gases (Neon, Helium, Deuterium, Neon+Helium) by changing different parameters like charging voltage, capacitor bank energy, discharge current, anode shape, gas pressure and influence of preionization. The objectives of the studies are to enhance soft X-ray emission. The Rogowski coil, high voltage probe, PIN diodes and pinhole camera masked with appropriate absorption filters are used for diagnostics. Specifically attention is paid to tailor the radiation in different energy windows i.e. 1− 1.56 keV and 4−8.33 keV. A single 12.5 μF capacitor charged at 19-23 kV (2.25-3.3 kJ), with a field distortion type sparkgap as switch is used to transfer the energy to the system. In the first experiment, the effect of preionization caused by depleted uranium (92U238) on soft X-ray and total X-ray emission is investigated by varying the neon gas pressure with and without preionization. The X-ray yield and pinhole images are found strongly influenced by the preionization and the pressure of the working gas. The soft X-ray yield of 82.5 ± 4.0 J in 1.3–1.56 keV energy window is obtained with preionization of neon gas at the optimum pressure, leading to the conversion efficiency of 2.5% of the stored energy. The total X-ray yield with preionization is 195 ± 9.0 J in 4π geometry measured at the optimum pressure giving conversion efficiency of 5.9%. The time integrated images indicate the broadening of X-ray emission zone with preionization. The second experiment is performed with helium as filling gas. The highest soft X-ray yield of 0.25 ± 0.01 J is obtained without preionization, which increases to 0.50 ± 0.02 J with preionization at optimum pressure. The total X-ray yield 1.50 ± 0.07 J without preionization, is enhanced to 2.44 ± 0.11 J with preionization. The plasma focus duration has been increased with preionization conforming enhancement and improvement in X-ray. This has also been conformed by the symmetric and enlarges pinch images with preionization.