Analysis and improvement of HV-components for spacecraft traveling-wave tubes

A report is presented on the analysis and improvement of HV traveling-wave tube (TWT) components for use in spacecraft. The investigation includes a theoretical study, involving electric field and pressure calculations, and an experimental one, involving partial-discharge measurements as a supplement to the standard voltage withstand tests. Improvement of the designs under study has been achieved mainly by the reduction of the cathode electric fields, thus reducing primary emission. A problem inherent in most space tubes is the fact that they are subjected to preflight tests in air, although designed for use in the satellite vacuum. This concerns primarily the outside connections and the HV cable. Because vacuum and air operation impose different and sometimes conflicting design requirements, these preflight tests are not representative of the HV performance in orbit and may even cause insulation degradation as a result of partial discharges. The methods used are presented, discussed, and illustrated, and, based on the results, some general conclusions and recommendations are formulated regarding the design, operation, and testing of HV-TWT components