Influence of the anode temperature on the breakdown voltage and conditioning characteristic of a vacuum gap

On the basis of the hypothesis that breakdown between plane electrodes in vacuum is initiated by a divergent electron beam which is emitted from the cathode and bombards the anode, equations are developed which show that the thermal conductivity and boiling temperature of the anode material play a dominant role in determining the breakdown voltage of an electrode system and its behaviour with respect to conditioning by repetitive sparking. The equations lead to a value of the order of 10 -4 A for the current carried by an electron beam at breakdown. The equations give agreement within 30% with the results obtained by Slivkov in 1958 with the anode heated to temperatures up to 800° C. The results of the present breakdown voltage and conditioning studies with the anode cooled by liquid nitrogen are given. The factors of agreement between theory and experiment range from 4 to 1.