Energy characterization of a high-density plume using a directional micro-Retarding Potential Analyzer

Summary form only given. A single-orifice Retarding Potential Analyzer (RPA) has been coupled with a microchannel plate (MCP) of 0.315% transparency to produce viable ion energy measurements within plasma plumes of density greater than 1/spl times/10/sup 18/ m/sup -3/. Consisting of several variably biased electrodes, an RPA sensor allows ions with sufficient energy access to a collection plate while repelling electrons and low energy ions. This paper addresses the experimental validation of a Directional micro-Retarding Potential Analyzer (D/spl mu/RPA) to a similar single-orifice RPA without a microchannel plate in the plume of a high-powered Hall Thruster. Single-orifice RPAs have previously been designed for Hall thruster plume characterization, with particle number densities of approximately 1/spl times/10/sup 16/ m/sup -3/. Investigations into the validity of the MCP design concept, specifically the ability to eliminate space charge limitations and potential breakdown phenomena between electrodes, are also described. This paper also demonstrates the segmented current collection theory and the unstructured 3D particle in cell (PIC) simulations developed for the D/spl mu/RPA channel flow.