Radial Electric Field Control for Retardation of Radial Transport of Bounce Ions in the Tandem Mirror

Existence of the bounced ions by the plug potential is essential in order to improve the confinement in the tandem mirror. The anchor cell with non-axisymmetric magnetic field configuration is installed between the plug/ barrier cell and the central cell to stabilize the magnetohydrodynamics (MHD) instability. The electro-statically trapped ions are bounced at the plug region after passing through the anchor cell from the central cell. The trajectories of the bounce ions are calculated on the assumption that the cross-sectional shape of the magnetic flux tube is slightly different from the cross-sectional shape of the equi-potential surface at the mirror throats of the anchor cell. Radial drift is estimated as a function of the discrepancy of the shapes. It is pointed out that control of the radial electric field is effective to retard the radial transport. Keywords: radial electric field, bounce ion, trajectory, radial transport, tandem mirro