A Study of the Azimuthal Electron Drift in an E×B Discharge Using a Non-invasive Antenna Array

A non-invasive antenna array is used to study medium and high-frequency plasma instabilities and to generate a spatial and temporal map of the azimuthal drift current in a coaxial Hall discharge. Typical Hall plasmas are characterized by strongly magnetized electrons and streaming ions and it is hoped that a better understanding of the azimuthal drift in such devices might further elucidate the importance of various mechanisms on bulk electron mobility in the broader range of E×B discharge plasmas. In this study, the time dependent measurements of induced current in loop antennas encircling the outer insulating channel walls during quasi-steady state are used to qualitatively investigate the correlation of instabilities with fluctuations in electron mobility. The calibration of the antenna array is done numerically and verified experimentally at multiple frequencies. High frequency oscillations consistent with those described in the previous literature are reported. In addition, preliminary results of using the array to characterize the azimuthal current distribution are obtained using fast current interruption on a timescale shorter than that characterizing plasma relaxation. ________________________________________________________________________