Abstract: A cathode for a secondary emission structure comprised of a superconductive material is described. In one embodiment the cathode comprises a layer of a superconductive material such as yttrium barium cupric oxide, or rare earth substituted neodymium cupric oxides. The layer may be bonded to a metal electrode or preferably the cathode consist of a superconductive or conductive oxide. The use of a superconductive material provides a cathode having suitable secondary emission characteristics and, furthermore, which being conductive at room temperatures, as well as, temperatures of operation of the cathode, obviating the need for a use of a very thin film of a secondary emission material.

Abstract: A potted heater assembly and a method of forming such a potted heater assembly comprises the steps of introducing into a mold having a filament disposed therein a slurry containing a liquid vehicle and particles of a refractory ceramic, said particles having a cylindrical shape and a diameter of generally less than a micron. The method further includes the step of removing the liquid vehicle from the slurry to leave behind a consolidated ceramic embedding the filament, and heating the ceramic having the embedded filament to further consolidate the ceramic to provide said ceramic having a density of at least 85% of theoretical density for the particular ceramic. The potted heating assembly having a ceramic potting embedding a filament heater is provided having higher post-sinter density than prior assemblies and has substantially higher strength.