Radial electric field control by electron injection in Tohoku University heliac

In this paper, we present experimental results of improvement for plasma confinement by controlling electric field with electron injection [1]. In order to generate the negative radial field, we inserted a hot cathode into the plasma and then biased negative voltage. We observed the plasma parameter changes after the hot cathode biasing: the increase of line density, the fluctuation suppression, the negative radial electric field formation, the plasma rotation, and the increase of the energy confinement time. These results suggest that the improvement of plasma confinement by the formation of negative radial electric field is achieved.