Azimuthal and axial dispersion relations of low-frequency oscillations in partially magnetized plasma with crossed electric and magnetic fields

Abstract

This paper presents the results of the azimuthal and axial wave diagnostics of a partially magnetized E × B Penning source. Various probes were employed, namely, a two-tip probe for azimuthal waves and two- and four-probe arrays for axial waves, to investigate the spatial characteristics of the instability using a two-point probe technique. The azimuthally aligned tips of the two-tip probe facilitated the investigation of the evolution of the azimuthal dispersion relation, which exhibited a well-known azimuthally propagative spoke at low discharge voltages. By utilizing axially aligned four-probe arrays with a probe distance of 3 mm and two-probe arrays with a relatively long probe distance of 20 mm, we sought to determine whether the rotating spoke propagated in the axial direction in the cylindrical E × B source. Our findings suggest that the rotating spoke originated near the axial center and propagated toward each cathode, rotating in a direction tilted from the azimuthal direction.