GB635479A - Improvements in and relating to magnetrons - Google Patents

Abstract

635,479. Magnetrons. BRITISH THOMSONHOUSTON CO., Ltd. Sept. 10, 1945, No. 23332. Convention date, June 22, 1942. [Class 39 (i)] A multi-resonator magnetron comprises a pair of pole-pieces 40, 41, Fig. 1, preferably permanently magnetized, located within a ferromagnetic container, e.g. of cold rolled steel, which serves as a low reluctance return path for the magnetic flux. In a modification, Fig. 6, the arrangement is unsymmetrical, 150 being a permanently-magnetized pole-piece and 162 a multi-cavity anode of ferromagnetic material which is magnetized by induction by the polepiece 150. The envelope is closed by headers 11, 12 and has cooling fins 14 of which 15 serves as a mounting flange. The pole-pieces 40, 41 are secured to discs 48, 49 based on the headers 11, 12 by clamping rings 51, 52 and are supported and spaced from the anode by discs 56, 57 and rings 54, 55. The cathode leads pass through a central aperture in pole-piece 40, and an exhaust tubulation 85 is attached to the other pole-piece 41 over a central aperture therein. The multi-cavity anode has small channels cut in the periphery thereof to receive rings of brazing material and a large channel 29 to reduce the weight. The indirectly-heated cathode has a flanged sleeve 32 closed at either end by discs 36, 37 and is positioned by insulating beads 62, 63, and the cathode leads 37<1>, 371 are positioned by insulators 76, 77. A centring stud 68 projecting from disc 36 is received in bead 63. The cathode leads 37<1>, 37<1> are secured to heavy leads 79, 80 sealed through metal eyelet 82 by glass body 81. The polepieces 40, 41 may be of an alloy of aluminium, nickel and cobalt such as those described in Specifications 423,897 and 424,746, [both in Group II], or of an alloy of iron, nickel, and titanium. The surfaces of the pole-pieces adjacent to the interelectrode space are finished by grinding and are then copper-plated to reduce high-frequency losses. Slots 49<1> in members 48, 49, holes 90 in discs 56, 57, and hole 92 in anode 20 allow all the parts of the device to be evacuated during manufacture. Energy is extracted by coupling loop 100 and tapered transmission line 107, 110 hermetically sealed by glass bead 112. In a slight modification, Fig. 5 (not shown), the cathode is grounded to the envelope and the anode is insulated therefrom. In the embodiment of Fig. 6, a supporting and spacing ring 154 is provided for pole-piece 150 and the cathode 157 is insulated from pole-piece 150 by member 158. The anode 162 is of iron or steel and is coated with copper. It has four radially-extending tubular channels 165 communicating with the space above the anode by slots 166 and also with a central opening (not shown) in the anode. The channels 165 serve as resonators. The Specification as open to inspection under Sect. 91 suggests that the anode structure of Fig. 6 may be permanently magnetized. This subject-matter does not appear in the Specification as accepted.