Performance of solid insulators in vacuum

In the last decade considerable research effort has been devoted to the exploitation of vacuum as an insulating medium. The impetus for this work has come mainly from the rapidly expanding technology of high power x-ray tubes, high energy particle accelerators and space exploration. Most of the research endeavour has been devoted to the study of breakdown across vacuum gaps under steady d.c. fields. Comparatively little attention has been given to the problems of solid insulators in vacuum. In any high voltage vacuum device there must be at least one insulator/vacuum interface which is subjected to the full voltage of the device. The physical size of the vacuum enclosure is often determined by the insulation performances of the solid insulator. Insulators are used for the support of high voltage electrodes and in many cases form the vacuum enclosure (e.g. x-ray and accelerator tubes).