Magnetic probe measurements of current sheet dynamics in a coaxial plasma accelerator

A high-frequency multiple magnetic probe assembly has been specifically fabricated for the study of current sheet dynamics in the axial acceleration phase of a low-energy dense plasma focus (DPF) device operated in a nitrogen gas medium. The response time of each probe is of the order of 1 ns and the tiny structure of the probe is well suited to sense the magnetic field associated with a pulsed plasma without perturbing the plasma unduly. The magnetic probes were calibrated using a simple, novel and reliable calibration technique and the calibration factor is found to be 0.34 +/- 0.028 T V-1. Our study reveals that the parabolic current sheet accelerates as it propagates through the electrode assembly, reaching a rundown velocity of similar to6.1 cm mus(-1). The average current sheet thickness in the axial acceleration phase is found to be similar to3 cm. In our case, the current shedding and mass loss factors are estimated to be 32% and 40% respectively. Our approach of using a high-frequency multiple magnetic probe assembly for the study of current sheet dynamics in a DPF device is highly effective in obtaining precise and accurate measurements.