Potential Distribution in the End Region of the GAMMA10 Tandem Mirror Associated with Electron Flow Control

Abstract

Potential distribution in an end region of the GAMMA10 tandem mirror is investigated associated with experiments for control of an electron flow to a floating endplate installed on an end wall of the vacuum vessel. The end region has an open field configuration. Mesh bias and thermal dike experiments have been carried out in order to reduce a heat flow to the endplate by suppression of secondary electron emission from the endplate. Variations of the axial potential distribution in the two experiments are studied. The observed variations agree with predictions of a theoretical potential model. This agreement shows a strong effect of the secondary electrons on the potential distribution in the end region and also indicates that the potential distribution is predominantly determined by axial particle transport. In this study, production of Yushmanov electrons is also shown.