A technique for studying the multiple emission sites on broad area electrodes in a vacuum

Observations of the transition radiation at the anode of a high voltage vacuum device using a low-light telescope have enabled the positions of the emission sites on the cathode to be determined accurately and have shown the way in which emitters are destroyed and sometimes produced at a breakdown. In addition, the electrical characteristics of the individual emission sites have been obtained by measuring the intensity of the transition radiation. This technique should allow the factors governing the voltage performance of industrial high voltage vacuum devices to be better understood.