B-dot probe measurements on plasma plume expansion across the magnetic field

Abstract

Time-varying diamagnetism in laser-produced plasma moving across a transverse magnetic field for different field strengths has been studied using fast imaging and magnetic probe. The emphasis of the present work is on the development of suitable B-dot probe, quantitative analysis of induced diamagnetic field in an expanding plasma plume and its effect on the applied magnetic field profiles. A Helmholtz coil with pulsed power system is used to produce uniform magnetic field varying from 0.13 T to 0.57 T. Helmholtz coil allows the plume imaging along the magnetic field lines, which gives the direct structural information of the induced diamagnetic cavity. A high frequency three-axis B-dot probe has been developed to measure the transient magnetic field. Different experimental approaches have been used to test the response, sensitivity and calibration of the developed probe. It has been observed that induced magnetic field displaced the external magnetic field that is plasma plume shows the diamagnetic behaviour for considered magnetic field range. The probe signals in directions orthogonal to the applied/induced magnetic lines are correlated with the distortion in applied magnetic field in three dimensional space, which is consistent with recently simulated topology of external magnetic field in similar experimental conditions [Patel et al, 2021 Plasma Phys. Control. Fusion 63 115020 ].