Effect of axial magnetic field variations on asymmetry-induced transport in a non-neutral plasma trap

Abstract

It has been suggested that magnetically trapped particles play a role in the asymmetry-induced radial transport observed in the Occidental non-neutral plasma trap. This magnetic trapping would occur due to a small increase (β≡δB∕B≈0.4%) in magnetic field at the center of our solenoid and would keep low velocity particles confined to the ends of the trap. To test this suggestion, three coils of additional windings have been added to the trap solenoid thus allowing adjustment of the axial field variation δB. The effect of these adjustments on typical radial flux resonances is investigated. Making B as uniform as possible reduces β by a factor of 5.9, but this produces little change in the transport. Varying β over the broader range from −8.5% to 9.5% gives variations of 20%–90% in the magnitude, peak frequency, and width of the flux resonances, but these variations do not match the predictions of a simple model of trapped particle transport based on isotropic particle distributions.