Abstract: Cathodes having a support for emissive material of foamed carbon are mechanically stable and resistant to detrition and have a homogeneous pore distribution.

Abstract: In a thermionic cathode having a planar emissive body and a heating element of pyrolytic graphite which is provided on the side of the emissive body remote from the emissive surface of the emissive body, a uniform temperature distribution adjusts during operation throughout the overall emissive surface when the heating element is planar and the crystallographic c-axis of the pyrolytic graphite extends everywhere normal to the surface of the heating element facing the emissive body. As a result of this the possibility is obtained of realizing a planar, "rapid", induction-free unipotential cathode having a substantially ideal homogeneous temperature distribution.

Abstract: Disclosed are grid electrodes of glassy carbon which have good mechanical and electrical properties and can be manufactured in a simple manner with a great dimensional stability. The grid electrodes may be made by two alternative methods. In one method a body of cured synthetic resin is formed or processed into the shape of the desired electrode, after which it is carbonized. In the second method a preshaped body of cured synthetic resin which is in the unprocessed state, is carbonized after which the resulting glassy carbon body is further processed to the desired electrode, preferably by laser beam cutting.