(under subclass 337) Cathodes where the cathode member is formed with a hollow cavity, the cathode member being designed to emit electrons from the interior walls of the hollow cavity.
SEE OR SEARCH THIS CLASS, SUBCLASS:
346, for cathodes under subclass 643 which include a body or mass of electron emissive material which is at least partly enclosed within a support or carrier member, the support or carrier being permeable to electrons, or being permeable to the electron emissive material so that the material can permeate the support or carrier and form a coating thereon.
