The action of strong electric fields on the current from a thermionic cathode

Abstract

It is well known that the “Saturation Current” from a thermionic source rises continuously as the applied voltage is raised and in reality never reaches a saturation value. W. Schottky predicted this rise in the saturation current on theoretical grounds and obtained a rough experimental confirmation of his theoretical formula. The present investigation was undertaken to find what connection it has with the emission of electrons from cold metals under the action of intense electric fields. If the truth of Schottky’s theory be assumed it is possible to deduce the value of the electronic charge e from observations of the rise of the saturation current with the applied field. It was not the primary intention of the author to determine the value of e in this way, nevertheless the results obtained show that the method might be developed into one of some accuracy, and thus to give a value of this important constant in a way differing completely from that of Millikan (oil drop method), Perrin (Brownian movement) or of Hull and Williams (shot effect).