GB473149A - Improvements in or relating to thermionic cathodes producing a directed electron beam - Google Patents

Abstract

473,149. Thermionic cathodes. ZEITLINE, V., ZEITLINE, A., and KLIATCHKO, V. April 8, 1936, No. 10389. Convention date, April 8, 1935. [Class 39 (i)] A thermionic cathode structure producing a directed electron beam is mounted inside an electric discharge device so as to be isolated from atmospheric pressure and the cathode is supported immediately adjacent its heated emissive surface by supports, expansion of which is freely permitted transversely to the direction of electron emission whereby thermal expansion of the structure is taken up by the supports in a transverse direction and the emissive surface is maintained substantially accurately in its axial position within the device. In the form shown in Fig. 1, an insulating tube 1 carrying the cathode 3 is mounted transversely within the anode 7, its ends projecting through apertures therein and engaging spring fingers 20, 21 which permit transverse expansion of the tube. 6 is a control electrode. In a modification the heater is bent into a hairpin to reduce its magnetic field and passes through two parallel insulating tubes bound together by metallic ribbons at the ends. The cathode may be replaced by a wire wound helically over the tubes and coated with emissive material. In another form a pot-shaped cathode is supported on transverse bars mounted at the ends similarly to Fig. 1, and four short heating tubes are inserted in a pocket at the back of the cathode. In another method, a transverse heater tube is supported at the ends by pillars mounted in a yieldable disc, for example of mica, which fits within an anode. In Fig. 6 a pot-shaped cathode 3 has a radially extending flange 3a which is clamped between two insulating members 14a, 14b, the heater being inserted in the recess 3b. In Fig. 7, the cathode tube 1 extends in an axial direction, and the emissive surface 5 is coated on the inside at one end. Rigid rods 16, 17 adjacent the surface 5 are arranged to expand freely in a transverse direction. Further support rods 16a, 17a are similarly mounted but are also flexible to take up axial expansion of the tube.