Observation of a Radial Current at a Plug/Barrier Cell in GAMMA10

Abstract

This paper presents a picture of current flow relevant to the plug/barrier cell and an end plate installed on the end wall of the GAMMA 10 tandem mirror. Detailed analyses show that, during electron cyclotron resonance heating for plug potential formation, a net electron current flows through the end plate. In the plug/barrier cell, on the other hand, ion currents are detected during ECRH on ring electrodes newly installed near the side wall of the vacuum vessel. A part of the radial ion currents is connected to the axial net electron current flowing through the end plate. This indicates that a residual non-ambipolar diffusion still remains. The radial ion current in the plug/barrier cell includes another component that originates form the axial ion flux emanating from the central region. This suggests radial diffusion of ions during potential plugging.