The design of high-voltage insulators for spacecraft traveling wave tubes

As part of a study on high-voltage design concepts used in microwave tube technology, a number of different insulator designs were studied. This work demonstrated the presence of surface charge and its effect on the voltage holdoff performance and the conditioning process. Insulators may be characterized by the breakdown voltage, the conditioning speed, and the dependence on surface charge. Insulators with anode field enhancements gave the best performance. Field enhancements at the cathode side were less harmful if stepped insulator shapes were chosen. Effective conditioning required at least a limited number of breakdowns. With sufficient conditioning breakdowns all insulator geometries tested reached an averaged breakdown field exceeding 12 kV/mm