Low-aspect-ratio toroidal equilibria of electron clouds

Abstract

Toroidal electron clouds with a low aspect ratio (as small as 1.3) and lasting for thousands of poloidal rotation periods have been formed in the laboratory. Characteristic toroidal effects like a large inward shift of the minor axis of equipotential contours, elliptical and triangular deformations, etc., have been observed experimentally for the first time. The results of new analytic and numerical investigations of low-aspect-ratio electron cloud equilibria, which reproduce many of the observed features, are also presented.