US3383551A

US3383551A - Coaxial magnetron with improved thermal dissipation

Info

Publication number: US3383551A
Application number: US431028A
Authority: US
Inventors: William A Gerard
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1965-02-08
Filing date: 1965-02-08
Publication date: 1968-05-14
Anticipated expiration: 1985-05-14

Description

y 1968 w. A. GERARD 3,383,551

COAXIAL MAGNETRON WITH IMPROVED THERMAL DISSIPA'IION Filed Feb. 8, 1965 BERYLLIA 2 36 38 BERYLLIA WITNESSES BERYLL'A F165 INVENTOR William A. Gerard ATTORNEY Unite 3,383,551 COAXIAL MAGNETRON WITH IMHRQVED THERMAL DISSlPATiON William A. Gerard, Horseheads, N.Y., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa, :1 corporation of Pennsyivania Filed Feb. 8, 1965, Ser. No. 431,028 '7 (llaims. ((Il. 315-39.77)

ABSTRAT OF THE DISCLOSURE This invention relates to electron discharge devices and more particularly to coaxial magnetron type devices.

In the R. I. Collier and I. Feinstein US. Patent 2,854,- 603, issued Sept. 30, 1958, there is disclosed a coaxial magnetron structure which comprises an inner and outer resonant system. The inner resonant system includes a cylindrical anode together with a plurality of anode vanes radially extending inwardly therefrom. These vanes define a circumferential array of inner, or anode cavity resonators surrounding a cathode. An outer cavity resonator is defined between an outer wall and the cylindrical anode. The two systems are coupled by a circumferential array of uniformly spaced slots through the cylindrical anode which connect the outer resonant system with the anode cavity resonators. The inner resonant system is designed to oscillate in the 1r mode, while the outer system is designed to oscillate in tl.e TE mode. The two systems are effectively locked together by means of the coupling slots.

Such a structural arrangement overcomes many disadvantages inherent in magnetrons of prior design. The conventional magnetron does have one advantage in that the anode vanes are connected directly to an external wall on which exterior radiating heat fins may be positioned. The prior conventional magnetron provided a short thermal path from the anode vane tips to the heat radiating fins.

The coaxial magnetron, on the other hand, has a longer path for conduction of the heat from the anode vane tips to the outer or external wall where radiating fins may be provided. This means in most coaxial magnetrons that the heat must flow through the thin anode vanes, axially along the thin anode cylinder and then along the end plate of the outer cavity resonator to the outer cylindrical wall of the cavity resonator where exterior radiating fins are provided and cooled by suitable means such as air flow.

The main thermal rise in the coaxial magnetron occurs in the thin anode cylinder and in the vanes themselves where the cross section is relatively small. In a coaxial TE mode cavity, circulating currents in the cylindrical anode drive the coupling slots in phase. The vanes act as quarter wave transformers which provide a high voltage between the anode and cathode for interaction with electrons. For maximum voltage, the anode wall must be thin or short in an electrical sense. This is due to the fact that it is desirable to have all the anode vane pairs of the same length, both the ones including the coupling slot and the ones between the slots. The slots and. the cylindrical anode effectively lengthen the alternate slot vane pairs States Patent making the voltage stepup nonuniform from vane to vane. This departure from uniformity is not serious providing the anode wall is thin compared to the quarter wave length of the vanes. It is found that a thickness of onesixteenth of the operating wave length is a tolerable thickness. This is about .060 inch in the case of an X-band (9,000 megacycles) coaxial magnetron. This electrical requirement provides a severe limitation on removal of heat.

It is accordingly an object of this invention to provide an improved coaxial magnetron structure. It is another object of this invention to provide an improved means of conducting heat from the hot spots in a coaxial magnetron to the external wall thereof.

It is another object to provide additional cooling for a coaxial magnetron without sacrificing electrical performance.

Briefly, the present invention provides improved heat removal means in a coaxial magnetron wherein high heat conductivity and electrically insulating material is provided in contact with the anode whereby heat fiow may be conducted through these high heat conductivity materials to the pole pieces and auxiliary heat conductors may be positioned within regions within the magnetron and do not affect the electrical characteristics of the magnetron.

Furthcr'objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of the specification.

For a better understanding of the invention, reference may be had to the accompanying drawings, in which:

FIGURE 1 is a view of a coaxial magnetron partly in section incorporating the teachings of this invention;

FIG. 2 is a schematic view of the device shown in FIG. 1, illustrating the magnetic circuit; and

FIG. 3 is a partial sectional view of a portion of FIG. l taken along line III-Ill.

With reference now to the drawings, there is shown a coaxial magnetron embodying the present invention. The magnetron is comprised of a body or shell member 10 which is substantially cup-shaped. The body 10 includes an outer wall member 12 forming the outer wall of cavity resonator 30 and a bottom wall member 14 forming the lower wall of the cavity resonator 30. The body member 10 is of a suitable electrically conductive material such as copper. An upper end cover 16, also of copper, provides the upper wall of the cavity resonator 30.

Output energy from the magnetron is derived from the cavity resonator 30 by means of suitable coupling means 13. A plurality of heat radiating fins 13 are provided on the outer wall 12 of the cavity resonator 30 and onto which a suitable cooling medium such as air may be directed for cooling of the magnetron. An anode 20 is provided within the body member 10. The anode 20 includes a cylindrical member 23 which defines the inner wall of the cavity resonator 30. The cylindrical anode portion 23 is secured to the lower plate 14. The cylindrical anode portion 23 is secured to a flexible annular member 15. The outer periphery of the member 15 is secured to the end plate 16. In this manner the member 16 which is of good thermal conductivity material such as copper permits heat conduction from anode 2t? while still permitting expansion of the anode 20. The anode cylinder 20 includes a plurality of vanes 24 which extend radially inwardly from the cylindrical portion 23. Centrally disposed and extending through apertures in the end plate 16 and the bottom plate 14- is a cathode sleeve 26 which is provided with an electron emissive coating 28 of a suitable material such as barium oxide.

The magnetic circuit of the magnetron includes an. exhaust pole piece 31 extending through the aperture provided in the upper plate 16. A cathode pole piece 32 extends through the bottom plate 14. Two substantally horseshoe magnets 34 are secured to the

pole pieces

31 and 32.

The anode cylinder 23 includes a plurality of slots 21 arranged parallel to the axis of the tube and to the cathode sleeve 26 which extends from substantially adjacent the end cover 16 to the bottom plate 14.

Tie pole pieces

31 and 32 which have apertures adapted to encompass the cathode sleeve 26 have their end portions adjacent the anode vanes 24. Thermal conductive means illustrated as a ceramic ring 36 is postioned between the pole face of the exhaust pole piece 31 and the vanes 24. In addition, a thermal conductive means in the form of ring 38 is also provided between the pole face of the cathode pole piece 32 and the vanes 24. The

annular ring members

36 and 38 are of a suitable electrically insulating and thermally conducting material such as beryllia.

It is necessary in the coaxial magnetron that an annular space be provided between the pole pieces 31. and 32 and the anode cylinder 23. This annular spacing is necessary to provide proper coupling and current flow through the axial slots 21 provided in the cylinder 23 to the cavity resonator 30. This has been found experimentally to be about three times the width of the slots 21. By providing annular cylindrical members 39 and 41 of ceramic in this space and due to its dielectric constant, a narrower annular spacing can be utilized over that utilizing simply an evacuated region in this portion. If the space is filled with a suitable material such as beryllia, the space may be reduced to about equal to the width of the slots 21. In this manner,

auxiliary cylinders

40 and 43 of copper may be added between the ceramic cylinders 39 and 41 and the

pole pieces

31 and 32 to provide additional thermal conductivity from the anode vanes 24 to the bottom plate .14 and the top plate 16. The heat is then conducted through the external wall portion 12 to the radiating fins 13.

In this manner, the heat generated at the tips of the anode vanes 24 may also flow through the

spacers

36 and 38 to the

cylinders

43 and 40 respectively then to the top plate 16 and the bottom plate 14 respectively and then to the radiating fins 13.

In this manner, multiple paths are provided for conducting the heat from the vane tips to the exterior of the envelope. By providing the ceramic members 39 and 41 and the

copper members

40 and 43, the temperature rise in the anode cylinder 23 and, in turn, the anode vane tips may be reduced. The

spacers

36 and 38 provide an alternate path for heat which has flowed through the vanes 24. The

members

36, 38, 39 and 41 may be placed in good thermal contact by metallizing the surfaces and brazing the metallized surfaces to the contacting

copper members

24 and 20.

While there have been shown and described What are at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention be limited to the specific arrangement shown and described and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. A magnetron comprising a tubular wall member, a plurality of anode vanes positioned on the inner surface of said wall member and defining a circular array of anode cavity resonators, a cathode positioned within said circular array of resonators, an external cavity resonator including said wall member, said wall member having slots for coupling energy from selected ones of said anode cavity resonators to said external cavity resonator, end plates and an external cylindrical wall having radiating heat fins provided thereon, magnetic pole pieces positioned at opposite ends of said anode vanes and adjacent thereto, a first means of electrically insulative and thermally conductive material in thermal contact with said anode vanes and positioned between said anode vanes and one of said pole pieces, said first means being in thermal contact with a second means of thermally conductive and electrically conductive material provided between said one of said pole pieces and said tubular wall member, said second means in thermal contact with one of said end plates of said external cavity resonator.

2. A magnetron comprising a cylindrical anode member of thermal and electrical conduction material, a plurality of radially extending anode vanes of thermal and electrical conductive material secured to said cylindrical anode member and defining a plurality of anode cavity resonators, a cathode positioned coaxially within said cylindrical anode member, means including said cylindrical anode member defining an external cavity resonator, said wall member having slots for coupling energy irom selected ones of said anode cavity resonators to said external cavity resonator, said external cavity resonator having end plates and an external cylindrical wall having heat radiating fins provided thereon, said external cavity resonator of thermally and electrically conductive material, magnetic pole pieces positioned at opposite ends of said anode vanes and adjacent thereto, an auxiliary cylinder of a thermally and electrically conductive material provided between one of said pole pieces and said cylindrical anode member and means positioned between said cylindrical anode member and said auxiliary cylinder of a thermally conductive and electrically insulative material.

3. A magnetron comprising a tubular anode of a material of high thermal and electrical conductiviiy, a plural: ity of anode vanes radially directed from the inner surface of said tubular anode and defining circularly disposed anode cavity resonators, a cathode positioned within said circular disposed anode cavity resonators, means including said tubular anode defining an external cavity resonator, said wall member having slots for coupling energy from selected ones of said anode cavity resonators to said external cavity resonator, said external cavity resonator having end plates and an external cylindrical wall having heat radiating fins provided thereon, magnetic pole pieces extending into opposite ends of said tubular anode and spaced from said anode vanes to form an annular region between the outer surface of one of said pole pieces and the inner surface of said tubular anode, a tubular member of a material of high thermal and electrical conductivity positioned Within said region and secured to one of said end plates and thermally conductive and electrically insulative means for electrically insulating said tubular member fnom said tubular anode and said anode vanes and providing thermal conductivity therebetween.

4. A magnetron comprising a tubular anode of a material of high thermal and electrical conductivity, a plurality of anode vanes radially directed from the inner surface of said tubular anode and defining circularly disposed anode cavity resonators, said tubular anode having means for coupling energy from selected ones of said anode cavity resonators, a cathode positioned Within said circular disposed anode cavity resonators, magnetic pole pieces extending into opposite ends of said tubular anode and spaced from said anode vanes to form an annular region between the outer surface of said pole piece and the inner surface of said tubular anode, a tubular member of a material of high thermal and electrical conductivity positioned with said region and spaced from said tubular anode by thermally conductive and electrically insulative means.

5. A coaxial magnetron comprising a tubular anode of a material of high thermal and electrical conductivity, a plurality of anode vanes radially directed from the inner surface of said anode and defining circularly disposed anode cavity resonators, a cathode positioned within said circular disposed anode cavity resonators, means including said tubular anode defining external cavity resonator, said wall member having slots for coupling energy from selected ones of said anode cavity resonators to said external cavity resonator, said ex'ernal ca ty resonator having an external cylindrical wall having heat radiating fins provided thereon, end plate of high thermal and electrical conducti 'ty connecting said tubular anode to said external cylindrical wall, magnetic pole pieces extending into opposite ends of said tubular anode and spaced from said anode vanes to form an annular region between the outer surface of one of said pole pieces and the inner surface of said tubular anode, a heat conductive member of a material of high thermal and electrical conductivity positioned with said region and in good thermal contact with said end plate means and means positioned between said tubular anode and said member for roviding good thermal conductivity and electrical insulation therebetween.

6. A magnetron comprising a cylindrical anode mem ber of thermal and electrical conduction material, a plurality of radially extending anode vanes of thermal and electrical conductive material secured to said cylindrical anode member and defining a plurality of anode cavity resonators, a cathode positioned coaxially within said cylindrical anode member, said cylindrical anode defining an inner Wall of an external cavity resonator, said wall member having slots for coupling energy from selected ones of said anode cavity resonators to said external cavity resonator, said external cavity resonator having end plates and an external cylindrical wall having heat radiating fins provided thereon, said external cavity resonator of thermal and electrical conductive material, magnetic pole pieces positioned at opposite ends of said anode vanes and adjacent thereto, an auxiliary cylinder of a thermally and electrically conductive material provided between one of said pole pieces and said cylindrical anode member,

means positioned between said cylindrical anode memher and said auxiliary cylinder of a thermal conductive and electrical insulating material and a flexible member of thermal and electrical conductivity securing one end of said cylindrical anode member to one of said end plates to permit expansion of said cylindrical anode member.

'7. A magnetron corn 'sing a thin walled cylindrl al anode member of good tl crrnal and electrical conductivity, a plurality of radially extending anode vanes secured to said cylindrical anode member and defining a plurality of anode cavity resonators, a cathode positioned coaxially within said anode, means including said anode defining an external cavity resonator, said Wall member having slots for coupling energy from selected ones of said anode cavity resonators to said external cavity resonator, said external cavity resonator having end plates and an external cylindrical wall having heat radiating fins provided thereon, said external cavity resonator of thermally and electrically conductive material, pole pieces positioned at opposite ends of said anode vanes and adjacent thereto, an auxiliary cylinder of good heat and electrical conductivity provided between one of said pole pieces and said cylindrical anode and means positioned between said cylindrical anode and said auxiliary cylinder of a thermally conductive and electrically insulating material to provide an auxiliary path for conducting heat from said anode without affecting the electrical properties of said magnetron.

References tilted UNlTED STATES PATENTS 2,850,672 9/1958 Briggs 313-47 X 3,169,211 2/1965 Drexler et al 315-395 3,222,557 12/1965 Meachnm et al. 31346 X HERMAN KARL SAALBACH, Primary Examiner.

SAXFlELD CHATMON, 1a., Assistant Examiner.