Faraday Cup Designs for High Efficiency Determination of Energy- and Angular-Resolved Charged Particle Fluxes
In order to build a spacecraft, we must understand how the construction materials will behave in the space environment (i.e. when subjected to the solar wind). The USU Materials Physics Group performs electron emission tests on spacecraft materials in an Ultra-high vacuum (UHV) test chamber (Fig.1). The chamber utilizes Faraday cups (Fig.2) in order to quantify electron flux at a location within the chamber. This measurement is important in characterizing beam profiles of electron guns used in UHV experiments. Perhaps more importantly, the Faraday cups are used to detect secondary electrons (SE) and back-scattered electrons (BSE) emitted from the surface of at test material. Faraday cups provide a means to quantify the SEs and BSEs emitted from a material by measuring the current resulting from these electrons striking the inside walls of the Faraday cup. The ability to quantify these SEs and BSEs emitted from a given material is an important application of this instrument. How a material behaves when charged particles strike it is an essential material property when dealing with spacecraft materials. Faraday cups facilitate the understanding of this behavior. The intent of this project is to characterize the performance of current Faraday Cup detectors (used by the Materials Physics Group), how we can optimize that performance in order to obtain more accurate measurements, and how we can alter the design to meet desired requirements such as energy and angular resolution.