In Situ Thermal Characterization of the Accelerator Grid of an Ion Thruster

摘要

The application of an electric propulsion diagnostic systemfor in situ thermal characterization of electric thrustersnis studied, as described previously. Exemplarily, the surface temperature profile of the accelerator grid of a griddednion thruster RIT-22 is obtained and characterized. In situ pyrometer line scans in combination with precisenmeasurements of geometrical grid parameters are demonstrated. The accelerator grid surface temperature of thenfiring thruster is obtained by amodel calculation that requires the knowledge of geometrical grid parameters, such asnhole diameter, distance between holes, or grid shape. These parameters are also measured in situ with antelemicroscope for high-resolution optical imaging and a triangular laser head for surface profile scanning. Thendistance between grid surface and pyrometer optics are precisely monitored with the support of the triangular lasernhead, for which the position is fixed with respect to the pyrometer. The distance measurement allows for correctingnthe measurement spot size of the pyrometer. The temperature profiles at three different beam power levels (1250,n2250, and 4000W), and warm-up and cool-down phases demonstrate the capabilities of the complex equipment. It isnfound that thermal steady state is reached after 4 h of thruster firing. Furthermore, it is shown that the acceleratorngrid surface temperature increases almost linearly with increasing beam current.