Suppression of secondary emission of electrons from end plate in expander of open trap

The influence of secondary emission from the end plate in the expander divertor on the energy confinement in linear plasma devices was considered. A numerical model was developed to calculate a distribution of the electric potential along a magnetic field line in the expander divertor. The model assumes weak collisions and the absence of cross-field losses of both ions and electrons. The potential profiles in the case of both no and strong secondary emission are presented. It was shown that expansion of the magnetic field in the divertor can effectively suppress the influence of cold electrons on energy confinement even if the secondary emission coefficient is more than unity. The dependence of energy lost per one ion leaving the mirror on the secondary emission coefficient was studied. The influence of partial energy recuperation by cold electrons on the total energy balance was discussed. It has been shown that the energy loss per one ion is not sensitive to the recirculation of cold electrons if the secondary emission coefficient is not too large. Published under license by AIP Publishing.