Accession Number : AD0429464


Title :   A STUDY OF THE PROJECTIONS ON ELECTRODES AND THEIR EFFECT ON ELECTRICAL BREAKDOWN IN VACUUM,


Corporate Author : ILLINOIS UNIV URBANA COORDINATED SCIENCE LAB


Personal Author(s) : Tomaschke,Harry E


Report Date : Jan 1964


Pagination or Media Count : 104


Abstract : Recent studies of electrical breakdown in clean vacuum systems indicate that breakdown is initiated by field emission current and occurs at a value of the electric field which is approximately a constant independent of the electrode geometry and the spacing between the electrodes. It has been postulaced that sharp projections on the cathode cause a local enhancement of the electric field and hence almost all of the field emission current is emitted form these projections. The present investigation was undertaken to investigate the characteristics of projections that exist on electrode surfaces and to determine the correlation between the geometry the projections and the prebreak-down current-voltage characteristics of the electrodes. Fowler-Nordheim plots of the prebreadkdown currents predicted that the projections should be of the order of 10 to the minus 4 power to 10 to the minus 5 power cm in diameter and have a length about ten times the diameter. Direct observations of electrode profiles with an electron microscope confirmed that projections of the predicted size and shape did exist on the electrode surface. Electrical breakdown resulted in the disappearance of one or more projections and sometimes caused the formation of new projections. (Author)


Descriptors :   *FIELD EMISSION , ELECTRIC ARCS , ELECTRODES , VACUUM , ELECTRIC FIELDS , CATHODES , ELECTRIC DISCHARGES , SURFACES , SURFACE PROPERTIES , ELECTRIC CURRENT , HEATERS , VACUUM APPARATUS


Distribution Statement : APPROVED FOR PUBLIC RELEASE