Existence of the plug potential bounce ions is essential in order to improve the confinement in the tandem mirror. Plug potentials are created on both sides of the tandem mirror plasma by microwave injection. Anchor cells with non-axisymmetric magnetic configuration are installed between the both plug/barrier cells to stabilize the MHD instability. The magnetically trapped ions in the central cell are scattered from the mirror trapped region to the bounce region in which ions are bounced at the both plug potentials or the strongest magnetic mirror regions in the plug/barrier cells through the long bouncing path including the anchor cell. We investigated influence of the radial transport of the bounce ion on the radial electric field.
The trajectories of the bounce ions are affected by the electric and magnetic fields. Usually it seems that the electrostatic potential is almost constant along the magnetic field line. However, the magnetic flux tube with a circular cross section on the central mid-plane is strongly deformed at the anchor cell, that is, the eccentricity of the cross section of the flux tube is 0.999819 at the anchor mirror. Therefore, it seems that the magnetic flux tube does not necessarily coincide with　the equi-potential surface because the radial electric field will be strongly high locally at the anchor mirror throat region.
We calculated in a first stage the trajectories of the bounce ions that started from the mid-plane at the central cell and reflected at the inner mirror throat (IMT) of the plug/barrier cell. The deformation factor, which flattened the radial potential profiles, was introduced as a criterion of the different shapes, and two types of radial potential profiles were assumed in the central cell, that is, one is axisymmetric and the other is non-axisymmetric. Results about the radial transport were found and importance of the radial electric field control was pointed out for the core plasma in order to improve the confinement.