Studies of Field Emission and Electrical Breakdown Between Extended Nickel Surfaces in Vacuum

Abstract

Experimental studies of field emission and breakdown with nickel cathodes in planar diodes and a cylindrical projection tube are presented. These demonstrate that the currents preceding electrical breakdown are due to field emission from protruding whiskers. An activation of these whiskers can proceed by desorption of gases, and very high electric fields are capable of inducing new intensely emitting whiskers to appear. At critical electrical fields the whiskers disrupt, leaving molten pools at the cathode even in the cylindrical geometry where the anode can play no part in the process. Image disappearance may be caused by the whisker's melting. An estimate of the whisker height can be made from the size of the images in the projection tube. Application of the Fowler‐Nordheim equation enables the current emitting area and the field magnification factor of a protuberance to be estimated. Whisker melting may be the origin of Cranberg's clumps for circuit limited breakdown.