The effect of a nested trap on the orbital motion of a pure electron plasma

The nested trap has the unique capability of simultaneously confining plasmas of opposite charges and is expected to be used for research on vortex dynamics and antimatter. However, in a nested trap, the potential distributions for the confining electrons and ion plasmas differ, leading to distinct E×B drift motions. To isolate the plasma motion induced by the external electric field applied to form the nested trap, we investigated the orbital motion of a pure electron plasma confined off-axis. Two distinct phases were identified: phase I, exhibiting inverse rotation opposite to the direction of the orbital angular velocity Ωself driven by the self-electric field, and phase II, exhibiting time-dependent reverse rotation. In phase I, we observed a dependence on the ratio of positive to negative electrode voltages in the nested trap. By contrast, we showed that a comprehensive explanation of phase II requires consideration of the side well effect, which arises from particles that are initially confined throughout the nested trap and subsequently settle into the side well region.