First experiments looking at the symmetry of the plasma formation phase of the dense plasma focus using d-dot probes

Abstract

The Dense Plasma Focus is being considered as the basis of sophisticated technologies such as an energy producing fusion machine, space propulsion for interplanetary and deep space missions and nanomaterial fabrication. However, there are problems with ensuring a reliable and reproducible operation of the device. It does not operate well immediately after the device is exposed to atmosphere and re-evacuated. A series of training shots is required after which the operation stabilizes until the vacuum chamber is opened again. Our previous work on numerical simulation of the formation phase shows that plasma behaviour on hydrodynamic time scales is difficult to predict because of simultaneous presence of many time scales and scale lengths. A systematic understanding of the role of the training shots in the formation process therefore requires a new experimental approach. This paper presents the first experiments looking at the symmetry of the discharge during its formation phase. The new diagnostic uses 3 d-dot probes symmetrically placed outside the squirrel cage cathode looking at the insulator through gaps between cathode rods. First results are presented and discussed.