US2404212A

US2404212A - Magnetron

Info

Publication number: US2404212A
Application number: US470041A
Authority: US
Inventors: Ralph J Bondley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-12-24
Filing date: 1942-12-24
Publication date: 1946-07-16
Anticipated expiration: 1963-07-16

Description

July 16, 1946- R. J. BONDLEY MAGNETRON Filed Dec. 24, 1942 lll/1111111111111 Ill lll VIII/ Inventor: Ralph J. Bondley. by .if/w1? M Hi Attorney.

Patented July 16, 1946 MAGNETRON v Ralph J. BondIey, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application December 24, 1942, Serial No. 470,041

, l My invention relates to high frequency electric discharge devices and more particularly to ultra high frequency magnetronsof the space resonant type- In the development of ultra high frequency electric discharge devices, and particularly in the effort to increase the operating frequency of discharge devices of this nature, the incident decrease in the dimensions of the cooperating electrodes and associated structure has entailed certain limitations as to the magnitude of voltages which may be used in the higher frequency devices. In accordance with the teachings of my invention described hereinafter, I provide a new and improved structure for an electric discharge device of the magnetron type wherein the operating'frequency may be substantially increased, and wherein the structure is arranged and .positioned so that a reduction in the operating voltage of the device is not required. l

It is an object of my invention: to provide a new and improved ultra ,high frequency electric f* discharge device.

It is another object of my'invention to provide a new and improved ultra high frequency electric discharge device of the magnetron type.

It is a further object of `my invention to provide a new and improved ultra vhigh `frequency magnetron wherein the cathode structure may be supported centrally with respect to Va magnetic pole piece, and wherein the magnetic iield distortion is reduced or substantially eliminated.

It is a still further object of my invention to provide a new and improved structure for an ultra high frequency electric discharge device of the magnetron type wherein the relative dimensions of the cathode structure and the magnetic pole piece obtain a desired configuration of the magnetic lines of force within the space discharge region, thereby producing a focusing eiect upon the electrons constituting the space discharge or limiting the divergence of the electrons at the ends of the space discharge region.

Brieiiy stated, in the illustrated embodiment of my invention I provide a new and improved ultra high frequency magnetron wherein a cathode is supported centrally with respect to a longitudinal magnetic pole piece by means of cathode supporting structure extending through a longitudinal channel in the pole piece. Magnetic field distortion is reduced, or substantially eliminated, or controlled in configuration by the provision of a restricted opening in the channel. at the magnetic pole 1piece face. In this manner, the relative dimensions of the cathode and the magnetic pole piece may be employed to obtain a magnetic field in which the magnetic linesk of force are substantially parallel within the space discharge region, or the relative dimensions may be chosen to produce a barrelingg effect which tends `to 9 Claims. (Cl. Z50-27.5)

focus the `electrons of the space discharge at the For a better understanding of my invention,v

reference may be had tothe following description taken in connection with the accompanying v drawing, and its scope will be pointed out in the appended claims.

Fig. 1 illustrates in cross sectional View an ernbodiment of my invention as applied to an ultra high frequency magnetron of the type disclosed and broadly claimed in a copending patent application Serial No. 447,903 of Elmer D. McArthur, led June 22, 1942 and which is assigned to the assignee of the present application. Fig. 2 is a cross sectional plan view of the anode structure.

Referring now to Fig. 1 of VtheA accompanying drawing, I have there illustrated my invention as applied to an electric discharge device, such as an ultra high frequency magnetron, including an elongated cylindrical container the lateral wall structure of which is provided by a single metallic tube I which consists of a ferro-magnetic material suchas cold rolled steel, or the like. The ends of the container or tube I are closed by flanged v members 2 and 3 which are welded or otherwise hermetically sealed to the inner surface of tube l.

Within the container and approximately at its central portion there is provided an anode structure 4 shown in detail plan View in Fig. 2. The anode structure 4 is -preferab-ly of circular configuration provided with an enlarged central opening 5 and a plurality or series of smaller openings l arranged symmetrically about the central opening. The central opening 5 is joined to the openings 6 by means of radially extending slots 1.

The anode structure 4, which may preferably consist of copper, is supported by being brazed to the inner surface of tube l. Within the openv ing 5 of thevanode structurethere is provided a thermionic cylindrical cathode which may be of the indirectly heated type comprising a metallic sleeve or cylinder 8 of nickel or molybdenum which is coated externally with a suitable activating `material, such as barium oxide. Within the cylinder v there is provided a filamentary cathode heating element 9 by which the lcathode is maintained at an emissive temperature.

In operating the device, a space discharge is assumed to be developed in the region defined between the cathode cylinder 8 and the surrounding anode structure i by application of a suitable potential between the anode structure and the cathode. rlhe electrons which compose this space charge are given a spiral or orbital motion by a magnetic field produced by means 4to be described presently,. and the resultant electron oscillation, or oscillations, about the cathode produce excitation of the anode structure at its resonantl frequency or Vharmonics thereof,V The anode structure may be considered as consisting of a plurality of mutually coupled units in each of which the inductance is provided bythe wall sur- Vface of openings 6 andthe capacitance is pro-` of the magnetized pole pieces,these members may be constructed of a suitable metal or alloy having high coercive force anda high energy factonsuch i as alloys, or groups of alloys,'of aluminum, nickel and cobalt.

In order to provide relatively low reluctance g connections betweenv the base extremities of the respective pole pieces It) and Il, the pole pieces may be seated upon relatively thick disk-like members l2 and 1 3 constructed of a ferromagnetic material, such as steel. VThese members are l providedwith slots I 4 and l5 in order to afford suitable passages for the evacuation of the discharge device. Passage I5 is in communication with an opening. I3 inanged part 3, 'and a suitableY tubulation l1 may be employed for sealing the discharge device structure after'evacuation:

To secure the pole pieces IU and l l rmly t0 the base members, use may be made of clamping rings' I3 andlV which are slipped overthe pole pieces and welded to the base members. Accurate spacing of pole pieces vIt'l and l l with reference to the anodeY structure may be obtained by the use of spacing rings and 2l used in the manner illustrated. As shown in Fig. 1, each of` these rings is interposed between one surface ofj anode structure 4 anda surface of apertured disks 22 and `23,'each disk in turn being in abutment, with anrappropriately formed shoulder provide by the adjacent pole pieces.

As a means for supporting the cathode struc-` ture centrally with respect to the anode structure* 4, Imay'employ a concentric cable construction broadly disclosed and claimed in my copending` patent application rSerial No. 465,424, led No- V vember ,13, 1942, and which is assigned to theassignee of the 'present'application Referringv morespecically to Fig.'l of 'the drawing, I provide a concentric cable construction which ex-V tends ;through a longitudinal channel 24 in the magnetic pole piece l0. This channel is prefer` ably circular in cross section and is provided with,`

a restricted section 25 in the vicinity of the pole face 26. The diameter of the channel Vopening in the vicinity of section 25 is preferably equal to or 8 and the opposite or cooperating face of the anode structure 4. l For example, by choosing the relative dimensions cf the restricted opening at 25 and the cathode diameter, thefmagnetic eld may be con;` trolledso that the magnetic lines of force within y thespace'dlscharge region are substantially parallel. Furthermore, the relative dimensions may be chosen so that the magnetic lines Of fOrCe al less than the diameter of the cathode cylinder 8. By the choice of the relative dimensions of the` having a pole face substantially parallel to an Within the space discharge region tend to barrel outwardly, thereby exerting afocusing effect on A l the electrons constituting the space discharge and minimizing the divergence of the electrons at the top and bottom of the space discharge'region, In either instance, that is by maintaining the magnetic field lines of force substantially parallel or by producing the outward barreling effect, the divergence of the electrons at the ends of the space discharge region is minimized.

Considering more particularly the cathode supporting structure, I provide a concentric cable construction including an outer tubular metallic conductor 21, an inner conductor 28 and an interspaced tubular insulator 23,

conductors

21 and 2 8 being connectedto externally accessible lead-inv wires 3i) and 3l Whichare sealed by means of any suitable sealing structure, such as a anged me-Y ductor 21 so that the device may be operatedY at substantially high voltages. y .f

The cathode structure is supported by the concentric cable construction through a'anged and apertured collar 36 which is attached to a metallic disk 31, the vlatter of which is kprovided with a il' plurality of metallic tabs `.which are welded or soldered to cathode cylinder 8. One terminal of f the lamentarycathode heating element 9 is connected to the inner conductor 28, and the other terminal is connected to the outer conductor 21 by being connected to the cathode cylinder 8. `Of course, it is to be appreciated that the upper ter'- minal of the cathode heating element 9 which is connected to the inner conductor 28 is displaced from and electrically insulated'from the collar 35 and disk 31.Y Y

Energy may be extracted from the discharge device by employing a suitable output electrode means, such as a loop 38 which extends into one of the openings 6 and which constitutes an extension of an inner conductor 3B comprising one part of a concentric cable construction comprise ing conductor 39 and an outer tubular conduce tor'40.1

While I have shown and described my inven tion as applied to a particular device andv as em-V bodying various elements,'it will be obvious to those skilled in the art that changes and mcdications may be v'made `without departing from` my invention, and I, therefore, aim in the ap pended claims to cover all such changesr and modications as fallV Within the true spirit and electrodes including a cathode and an anode structure lsubstantially surrounding Said cathode and having Vopposed end faces, means for estab- 'Y lishing a magnetic eld comprising a pole piece end face of said anodev structure, said pole piece having a longitudinal channel extending therethrough and terminate'din the plane of said pole face, cathode supporting structure extending netron type comprising a plurality of enclosed` electrodes including a cylindrical cathode and an anode structure substantially surrounding said cathode and having opposed end faces, means for establishing a magnetic field comprising a pole piece having a pole face substantially parallel to an end face of said anode structure, said pole piece having therein a longitudinal channel extending through said iield piece and terminated at the face thereof in a restricted portion the dimension of which is equal to or less than the diameter of said cathode, and means extending through said channel supporting said cathode.

3. An electric discharge device of the mag- `netron type comprising a plurality of enclosed electrodes including a Vcylindrical cathode and an annular anode structure substantially surrounding said cathode, means for establishing a magnetic field comprising a pole piece having a pole face positioned near said anode structure and having therein a longitudinally extending channel terminated at the face, said channel having a restricted section of a dimension substantially less than the transverse dimension of said cathode to minimize the magnetic field distribution, and means extending through said channel supporting said cathode.

4. An electric discharge device of the magnetron type comprising a plurality of enclosed electrodes including a cathode having an emitting surface and an anode structure substantially surrounding said cathode and having opposed end faces, means for establishing a magnetic eld comprising a pole piece yhaving a pole face substantially parallel to an end face of said anode structure, said pole piece having therein a longitudinally extending channel terminated at the face thereof in a restricted section, the dimension of said section being equal to or less than the transverse dimension of the emitting surface of said cathode so that the magnetic eld tends to focus the electrons constituting the space discharge between said cathode and said anode structure at the ends of the space discharge region, and means extending through said channel for supporting Isaid cathode.

5. An electric discharge device of the magnetron type comprising a plurality .or enclosed electrodes including a cylindrical cathode and an annular anode structure substantially surrounding said cathode, means for establishing a magnetic field comprising a pole piece having a pole face positioned near said anode structure and having therein a longitudinally extending channel terminated at said pole face, said channel having a restricted section of a diameter substantially less than the transverse dimension of said cathode thereby controlling the configuration of the magnetic field to limit the divergence of the electrons constituting the space discharge at the ends of the space discharge region defined by said cathode and a cooperating surface of said anode structure.

6. An electric discharge device of the magnetron type comprising a plurality of enclosed electrodes including a cathode having an emitting surface and an anode structure substantially surrounding said cathode and having opposed end faces, means for establishing a magnetic eld comprising a pole piece having a pole face substantially parallel to an end face of said anode structure, said pole piece having therein a longitudinal channel extending therethrough and terminating at the face thereof, and means extending through said channel supporting said cathode, said channel having a restricted section in the vicinity of said pole face, the diameter of said section being no greater than the diameter of said cathode to limit the magnetic ield distortion Within thespace discharge region dened by said cathode and said anode structure.

7. An electric discharge device of the magnetron type comprising a plurality of enclosed electrodes including a cathode having an emitting surface and an 'anode structure substantially surrounding said cathode and having vopposed end faces, means for establishing a magnetic field comprising a pole piece having a pole face substantially parallel to an end face of said anode structure, said poler piece having a longitudinal channel extending therethrough and terminated in the plane of said pole face, cathode supporting structure extending through said channel, said channel having a restricted section in the vicinity of said pole face, the diameter of said section being no greater than the diameter of said cathode to minimize the magnetic field distortion within the space discharge region dened between said cathode and said anode structure, and an insulator within said channel maintaining said cathode supporting structure in spaced relation thereto.

8. An electric discharge device of the magnetron type comprising a plurality of enclosed electrodes including a cathode having an emitting surface and an anode structure substantially surrounding said cathode, a permanently magnetized pole piece having a face thereof substantially parallel to the plane of said anode structure and having therein a longitudinal channel extending therethrough and terminated at said face, cathode supporting structure extending through said channel, said channel having a restricted section in the vicinity of said pole face,

9. An electric discharge device of the magnetron type comprising a plurality of enclosed electrodes including a cylindrical thermionic cathode having an emitting surface and an annular anode structure having a central opening within which said cathode risv located, said anode structure having opposed end faces, a permanently magnetized pole piece having a pole `face substantially parallel to an end face of said anode structure, a longitudinal channel extending through said pole piece and having a section in the vicinity of saidpole face, the diameter of said section being no greater than the diameter of said cathode to limit the magnetic eld distortion, cathode supporting structure extending through said channel and asupporting insulator f for said cathode supporting structure positioned within said channel and spaced from said restrcted section.

RALPH J. BONDLEY.