Comparison of the effect of rotating electric fields and rotating magnetic fields on the diocotron instability using particle-in-cell simulations

Recently, a beam collimator system using a hollow electron beam to enclose a circulating beam has been proposed for the high energy vacuum. In this system, the hollow electron beam should remain stable during propagation, obviously. However, the diocotron instability, which is one of the nonneutral plasma instabilities induced by shear in the flow velocity of surface waves, makes the deformation of the beam. Therefore, it is important to control the hollow electron beam at first. Previously, we investigated the stabilizing effect of periodic dipole magnets on the diocotron instability using a two-dimensional particle-in-cell simulation. In the simulation, the beam cross section of the hollow electron beam was investigated under periodic dipole magnets in addition to the axial magnetic field. In addition to the previous work, we study the effect of rotating-wall electric fields on the diocotron instability, which also makes perturbations on the ExB drift, and compared the results of rotating magnetic fields.