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

Abstract

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 ~6.1 cm µs−1. The average current sheet thickness in the axial acceleration phase is found to be ~3 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.