Variation of soft X-ray emission with gas pressure in a plasma focus

The variation of the soft X-ray emission in a low energy (3 kJ, 15 kV) plasma focus over a range of pressures is investigated. The working gases are argon and an argon-hydrogen mixture. The X rays are detected using an assembly of PIN-Si diodes with differential filtering and with a multipinhole camera, soft X rays originating from the plasma and from electron beam activity on the copper anode are observed. In general, three pressure regimes can be discerned. In the first regime, both the plasma X rays and the copper line radiation are weak. In the second regime, the X-ray emission is intense and the contribution from copper lines is strong. In the third pressure regime, the plasma X rays are intense while contribution from the copper X-rays are weak.