Measurement of Charging and Discharging of High Resistivity Spacecraft Materials by Electron Beams
Paper presented at the 1st AIAA Atmospheric and Space Environments Conference. PDF available for download through link above.
New instrumentation has been developed for in situ measurements of the electron beaminduced surface voltage of high resistivity spacecraft materials in an existing ultra-high vacuum electron emission analysis chamber. Design details, calibration and characterization measurements of the system are presented, showing sensitivity to a range of surface voltages from <1 V to>12000 V, with resolution <1 V. The spatial profile of the voltage across the sample surface was measured by sweeping small electrodes across the>surface, using a paddle attached to a vacuum compatible stepper motor mounted within a hemispherical grid retarding field analyzer. These electrodes formed one end of a floating charge transfer probe that enabled measurements to be made by a standard electrostatic field probe external to the vacuum chamber. Surface voltage measurements were also made periodically during the electron beam charging process and as the surface discharged to a grounded substrate after exposure. Analysis of the measured curves provides information on the material electron yields and bulk resistivity.