Patent GB-615620-A (GB)
Title: Electron discharge devices
IPC: H01J23/22
Filed: 1945-03-08
Abstract: 615,620. Magnetrons. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. March 8, 1945, Nos. 5844 and 5845. Convention dates, March 8, 1944. [Class 39 (i)] An ultra-high-frequency discharge device comprises a plurality of anode segments defining the boundary of the cathode space and connected by cavity resonators, a cathode insulatingly supported on the anode, an element or insert of magnetic material on one side of the anode and a magnet having one of its polepieces in register with said element or insert. An anode block 10 which is an assembly of stamped copper sheets is provided with a central opening 11 and a plurality of radially directed slots which form cavity resonators, an indirectly heated cathode 14 extending along the axis of the opening 11. The block is supported by means of brackets mounted on a header 22. A pair of cylindrical inserts 15, 16 having tapered ends and consisting of magnetic material such as annealed cold-rolled steel is supported from the block 10 by a rod and bead construction 17-18, 17<1>-18<1> and rods 19, 20. The header has holes punched to admit the heater-cathode leads 26 and a tubular member 31 for the coupling loop conductor 29, 30. The insert 15 has a varying central bore for receiving cathode 14, the large bore receiving the cathode flange and the cathode' only contacting the remainder of the insert at the restricted portion 38. Slots 40, 41 contain ceramic tubing 42, 43 through which pass the cathode heater leads. The insert 15 is electrically connected to the cathode. The spaces between the inserts and the anode, and between the inserts and the wall of the envelope are .030 to .040 ins. wide. A plate 83 of non-magnetic material may be threaded as at 84 on each of the inserts so that they are adjustable to control the operation frequency of the tube or they could be supported adjustably on the rods 19, 20. The material for the insert has a lower coefficient of expansion than the rod and spacer and compensates for the downward change in frequency due to the thermal expansion of the cavity resonators. In a modification (not shown), the anode block is provided with a central chamber into which extend radial flat fin-like elements, the spaces between forming the cavity resonators and alternate anode segments are connected by ring-like conducting straps. The cathode is supported in grooves and openings in one of the inserts to which one cathode lead is welded. In another modification, the anode block is made up of a number of stacked thin sheets of conducting material provided with punchedout portions which form passageways communicating with tubular members sealed into the header member so as to allow cooling fluid to circulate. The header member'and envelope are of stainless steel having non-magnetic properties. The Specification as open to inspection under Sect. 91 also comprises a magnetron in which the magnetic inserts are replaced by sheet metal plates of non-magnetic material extending parallel to and on opposite sides of the anode block and insulatingly supported from the latter. This subject-matter does not appear in the Specification as accepted.