Patent GB-608047-A (GB)
Title: Improvements relating to electron beam valves
IPC: H01J25/78
Filed: 1945-11-03
Abstract: 608,047. Electric resonators. HARRIES, J. H. O. Nov. 3, 1945, No. 29221. [Class 40 (viii)] [Also in Group XL (a)] An electron beam valve has a resonator made up of three subcavities 19, 20, 21, Figs. 2, 3, of which the sub-cavities 19, 21 are smaller in transverse area and in axial dimension than the sub-cavity 20; the septum 22 has a parallel-sided deflection slot across which in operation an alternating transverse electric field is set up; the septum 23 has a slot and a pair of grids g<1>, g3, one on either side of the slot and two alternating electric fields parallel to the axis are set up in the sub-cavity 21; the three sub-cavities oscillate together at a single frequency. The modes of oscillation and the designing procedure are discussed in detail. The arrangement may act as a self-excited oscillator, or as a detector, or may be used for the reception or transmission of electromagnetic waves. The section of the sub-cavities may be cylindrical, Fig. 3, or rectangular, Fig. 9 (not shown). Energy is fed out of the resonator to a wave-guide 18, Fig. 2, through one or more slots cut in the wall of the sub-cavity 21. The sub-cavity 21 has its outer wall bent towards the septum 23 and provided with grids g<2>, g<4>, on either side of a central slot therein, the electrons being collected by a back plate 13 or by a "bucket" (not shown). Either of the sub-cavities 19 or 21 may have a flexible end to allow frequency adjustment after manufacture and during operation. Means described in Specification 606,177, [Group XL (a)], may be used to suppress secondary electrons which would normally be produced at the grids g<1>, g<2>, g3, g<4>. The sub-cavities are preferably made of copper pressings welded together by mounting them on a jig comprising two rods in a holder in vacuo with interleaved silver foil and heating in an eddy current furnace, but may be machined out of solid metal or built up out of flat stampings. The pressing 26 is curved so as to assist in forming the electron beam. The resonator is fixed by screws 31 to a ring 32 to the opposite faces of which glass envelope portions 34, 35 are sealed; the wave-guide 18 is mounted on the ring 32. The .electron gun 9, 10 is mounted on a transverse insulating bar 39 of ceramic material clamped to a similar bar 40 carried by two copper tubes 41. In modifications, the re-entrant portion of the sub-cavity 21 may be omitted, Fig. 10 (not shown), the grids g<2> and g<4> may be omitted, Fig. 11 (not shown), a number of resonators 8a, 8b, 8c, Fig. 13, may be arranged in a bank with intercoupling slots and may feed energy into a wave-guide 49, and are used with a common cathode 9a. The output of a single resonator device may be stabilized and controlled by inserting a probe electrode in the sub-cavity 21 and leading the current from the probe via controlling means to the electron gun, Fig. 14 (not shown); alternatively, the output from the control means may be led to recording means. In all forms, the beam may be modulated in the gun. The Provisional Specification refers to resonators in the form of square prisms, spheres and cylinders as being unsuitable for the invention. The axial length of the input and output sub-cavities is about one half the length of the main sub-cavity. The output septum may consist of a grid mesh, the apertures of which may be larger at the centre than at the edges. The beam after passing through the resonator may excite a resonator tuned to a higher frequency than the deflection frequency or variations in the beam current may be used to indicate the presence of oscillation. The input sub-cavity may have a plurality of beam entrance slots.