US2899604A - Magnetrons - Google Patents

Magnetrons Download PDF

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Publication number
US2899604A
US2899604A US2899604DA US2899604A US 2899604 A US2899604 A US 2899604A US 2899604D A US2899604D A US 2899604DA US 2899604 A US2899604 A US 2899604A
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pole
anode
magnetron
pieces
magnet
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/10—Magnet systems for directing or deflecting the discharge along a desired path, e.g. a spiral path

Definitions

  • This invention relates to magnetrons of the type having a cylindrical metal anode chamber within which is supported an anode system comprising a plurality of cavity resonators spaced round the anode axis, the latter being substantially parallel to, and usually coincident with, the axis of the anode chamber, in which a cylindrical cathode is supported so as to lie coaxially within the anode system, and in which each end of the anode chamber is closed by the sealing thereto of a pole-piece of magnetic material designed to co-operate with an external magnet for producing within the anode system the axial magnetic field required for the operation of the magnetron.
  • a magnetron of the type specified is often required to co-operate with a permanent magnet in the form of an incomplete ring, the pole-pieces of the magnetron forming a continuation of the two ends of the magnet so that the anode system of the magnetron lies in the path of the magnetic flux between these two ends.
  • the ring magnet required is usually very bulky and heavy, but for many purposes, such as for airborne use of the magnetron, it is very desirable that the bulk and weight of the apparatus should be as small. as possible.
  • the pole-pieces used hitherto in magnetrons of the type specified have usually been of generally cylindrical shape, in some cases with the inner ends, that is to say the ends nearer the anode system, tapered for concentrating the magnetic field within the anode system.
  • each pole-piece in a magnetron of the type specified is bevelled so that the outer end face of each pole-piece is inclined to a plane perpendicular to the axis of the anode with the longer sides of the two pole-pieces lying on the same side of the anode.
  • the effect of the bevelling is that the pole-pieces form more nearly a continuation within the magnetron of the surface curvature of the ring magnet, and this results in much less stray magnetic flux being present at these ends than is obtained when the ends of the pole-pieces are perpendicular to the anode axis, as has been the case in magnetrons of the type specified used hitherto.
  • the reduction of stray flux means that more of the magnetic flux'is usefully employed for forming the operating axial magnetic field within the anode system, and this in turn means that a smaller magnet can be used for obtaining a given axial 2,899,604 Patented Aug. 11, 1959 field, with consequent reduction in the size and weight of the apparatus as a whole.
  • the bevelling of the ends of the pole-pieces can conveniently be effected by forming the end faces of the pole-pieces as plane bevels, preferably equally inclined to a central plane passing through the center of the anode system perpendicularly to the axis of the anode.
  • plane bevels preferably equally inclined to a central plane passing through the center of the anode system perpendicularly to the axis of the anode.
  • curved bevels could be used that cause the pole-pieces to form more nearly continuations of the surface curvature of an approximately toroidal ring magnet with which the magnetron is intended to be used.
  • the pole-pieces are preferably mirror images of each other, at least as regards their magnetic properties, in the said central plane.
  • the invention includes within its scope combinations of magnetrons in accordance with the invention as aforesaid with gapped-ring magnets, which may be either permanent magnets or electro-magnets.
  • the advantage obtained with the invention in the latter case is either that the size of the magnet core can be reduced, 01' that the magnetising current required in the windings of the magnet, for obtaining a given axial magnetic field for the operation of the magnetron, can be reduced.
  • the thickness of the magnet in the direction perpendicular to the axis of the anode is greater than the diameter of the pole-pieces in this direction, and the two ends of the magnet are formed with recesses, extending parallel to the said axis, which fit closely round the parts of the pole-pieces of the magnetron about their longer sidesrwhen the pole-pieces are inserted into the recesses.
  • pole-pieces of a magnetron in accordnace with the invention need not necessarily consist of a single piece of magnetic material.
  • one or both of the pole-pieces might be pierced by a hole, coaxial with the anode axis, along which passes a tube providing a support and lead for the cathode, and within it a further tube or a rod providing a support and lead for the cathode heater.
  • the pole-piece might then be formed with one or more annular inserts of magnetic material between the various parts, which inserts are spaced apart for electrically insulating parts of the magnetron from each other.
  • the bevelled end of the pole-piece is then to be regarded as applied to the surface enveloping all the parts of the pole-piece.
  • Figure 1 shows a section along the axis of a magnetron in accordance with the invention, in operative combination with an approximately toroidal gapped-ring permanent magnet
  • Figure 2 shows a section along the line X'-X in Figure 1, looking from the right.
  • the anode chamber is formed as a circular cylindrical hole within a square metal block 1, the ends of which hole are closed by metal plates 2, 3 carrying pole-pieces 4, 5, which are of generally circular cylindrical cross section at their inner ends and will be further described later.
  • the central part of the block 1 is shaped to provide an even plurality of inwardly projecting anode segments 6, which define between them the cavity resonators of the anode system and bound at their inner ends a circular cylindrical electron orbit space within which lies the cathode 7 of the magnetron.
  • the cathode consists of a hollow metal tube of circular cross-section coated externally with electron emissive material (not shown) and is spigoted into one end of a hole pierced through a generally cylindrical inner part 8 of the pole-piece 4, which part is carried by one end of a cathode support tube 9 which extends away from the anode chamber coaxially with the anode axis.
  • tube 9 is insulatingly supported from the outer end of a metal tube 10, which coaxially surrounds it, by means of a glass thimble seal 11, and the tube 10 is in turn supported .by the spigoting of its inner end into the general: 1y cylindrical outer part 12 of the pole-piece'4.
  • the cathode 7 contains a heater 13 which is attached at one end to a metal disc 14 closing the free end of the cathode and at the other to a stout support wire 15.
  • the outer end of the wire 15 is coiled round, and welded to, the reduced diameter end of a heater support rod 16, the coiling providing resilience for the mounting and thermal expansion of the heater.
  • the heater rod 16 is insulatingly supported from, and coaxially within, the cathode support tube 9 by means of a glass button seal 17 at its outer end, and an insulating spacer 18 at an intermediate point along its length.
  • the outer end of the rod 16 projects beyond the glass button 17 to provide a heater lead terminal, and the outer end of the tube 9 projects beyond the thimble 11 and is outwardly flanged, with the attachment of a metal reinforcing annulus 19, to provide the cathode lead terminal.
  • the pole-piece 4 made up of the two parts 8 and 12 has the general form of a circular cylinder, the outer part of which has been cut away by a plane inclined to a plane perpendicular to the anode axis to provide a plane bevelled outer end 20.
  • the pole-piece 5 is formed in one piece with its end face 21 similarly plane-bevelled, so that the longer sides 22. and 23 of the two pole-pieces lie on the same side of the anode, and is provided on its inner face with an annular recess 24 which magnetically simulates the effect of the spacing between the parts 8 and 12 of the polepiece 4 for increasing the uniformity of the axial magnetic field.
  • the pole-piece 5 is also pierced axially by a central hole into the outer end of which is spigotted a metal tube 25 which serves as a pumping stem and is closed by a cold-weld cut-01f in the manufacture of the magnetron.
  • the tube 25 is covered by a protective metal cap 26 attached to the bevelled outer end of the polepiece 5.
  • the anode system of the magnetron formed by the segments 6 is provided on each side with concentric pairs of metal mode-spacing rings 27, and an output coupling loop 28 is connected on each side of the anode to one of these rings.
  • the two arms of the loop 28 pass through holes formed in the side of the anode block 1 and the centre of the loop is supported by a rod 29, set into the outer wall of the block, so as to lie within the space bounded by a tube 30 spigoted into an apertured metal plate 31 attached to the side of the block, the tube 30 being closed by a glass dome seal 32.
  • the block 1 is provided with channels 33 for the passage of water for cooling the anode in operation of the magnetron.
  • the metal parts of the magnetron referred to are all non-magnetic except for the pole-pieces 4 and S.
  • the magnetron described is designed for co-operation with an approximately toroidal ring permanent magnet 34 and is shown in the drawing in operative combination with the magnet.
  • the magnet is of approximately rectangular crosssection reducing in area towards the ends, the faces of which ends lie parallel to each other and are separated by a space just sutficient to permit the anode block 1 to be inserted between them, as shown in the drawing.
  • the ends of the magnet are formed with cylindrical transverse recesses 35 designed to receive the longer sides 22 and 23 of the pole-pieces 4. and 5 and to be a snug fit round approximatly half the circumference of the polepieces.
  • the axial length of each of the recesses 35 is such that the longer sides 22, 23 of the magnet polepieces just extend to the outer surface of the magnet, and the bevelled end faces 20, 21 of the pole-pieces form approximate continuations of the curvature of the outer part of the surface of the ring magnet that reduce the stray flux from the magnet toa low value.
  • a magnetron having a cylindrical metal anode chamber, a plurality of anode segments extending inmounted coaxially within the electron orbit space, and
  • each pole-piece having its outer end face bevelled and the bevels being oppositely directed so that the longer sides of the two pole-pieces lie on the same side of the anode.
  • a magnetron according to claim 1 wherein at least one pole-piece is built up by a plurality of coaxial pieces of magnetic material sealed between, and spaced apart by, the anode chamber and the cathode assembly support and supply leads, and wherein the surface enveloping all the said pole-piece parts has a bevelled outer end face as aforesaid.

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  • Microwave Tubes (AREA)
US2899604D 1956-03-28 Magnetrons Expired - Lifetime US2899604A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9766/56A GB820372A (en) 1956-03-28 1956-03-28 Improvements in or relating to magnetrons

Publications (1)

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US2899604A true US2899604A (en) 1959-08-11

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US2899604D Expired - Lifetime US2899604A (en) 1956-03-28 Magnetrons

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US (1) US2899604A (de)
DE (1) DE1128568B (de)
FR (1) FR1169957A (de)
GB (1) GB820372A (de)
NL (1) NL215711A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3173048A (en) * 1961-03-06 1965-03-09 Varian Associates Ion vacuum pump for magnetrons controlled for leakage of magnetron magnet
EP0264127A2 (de) * 1986-10-16 1988-04-20 Matsushita Electric Industrial Co., Ltd. Magnetron

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5907012A (en) * 1996-04-08 1999-05-25 H.B. Fuller Licensing & Financing, Inc. Water-based polyurethane-urea laminating adhesives and primers
US5717025A (en) * 1996-09-16 1998-02-10 H. B. Fuller Licensing & Financing, Inc. Melamine-formaldehyde resin based adhesive compositions

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2232559A (en) * 1936-01-29 1941-02-18 Gen Electric Short wave radio transmitter
US2524252A (en) * 1948-02-05 1950-10-03 Raytheon Mfg Co Electron accelerator of the microwave type
US2716711A (en) * 1951-01-11 1955-08-30 English Electric Valve Co Ltd Magnetrons
US2777085A (en) * 1952-05-29 1957-01-08 Westinghouse Electric Corp Secondary electron suppressor
US2787728A (en) * 1954-03-24 1957-04-02 Litton Industries Inc Electron discharge device with toroidal permanent magnet

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2232559A (en) * 1936-01-29 1941-02-18 Gen Electric Short wave radio transmitter
US2524252A (en) * 1948-02-05 1950-10-03 Raytheon Mfg Co Electron accelerator of the microwave type
US2716711A (en) * 1951-01-11 1955-08-30 English Electric Valve Co Ltd Magnetrons
US2777085A (en) * 1952-05-29 1957-01-08 Westinghouse Electric Corp Secondary electron suppressor
US2787728A (en) * 1954-03-24 1957-04-02 Litton Industries Inc Electron discharge device with toroidal permanent magnet

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3173048A (en) * 1961-03-06 1965-03-09 Varian Associates Ion vacuum pump for magnetrons controlled for leakage of magnetron magnet
EP0264127A2 (de) * 1986-10-16 1988-04-20 Matsushita Electric Industrial Co., Ltd. Magnetron
EP0264127A3 (en) * 1986-10-16 1989-07-12 Matsushita Electric Industrial Co., Ltd. Magnetron device

Also Published As

Publication number Publication date
DE1128568B (de) 1962-04-26
NL215711A (de)
FR1169957A (fr) 1959-01-08
GB820372A (en) 1959-09-16

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