US2406276A - Electric discharge device - Google Patents

Description

All@b 20,1946.v

G. M. wHlTE ELECTRIC DISCHARGE DEVICE 'F'uedom 13, 1942 n l W v u: r

Y Ivm/en' George M u? H is Attorney.

Patented Aug. zo, 1946 George M. White, Schenectady, N. Yi, assignor' to General Electric' Company, a corporation of New York Application November 13, 1942, Serial No. 465,401 Y My invention relates to electric discharge devices, and more particularly to the construction.

' gization of associated space resonant regions, or

cavities, Without sacrificing the power output of the device by a construction which lcauses the establishment of inordinately high voltage gradients across insulating parts of thestructure which would require a reduction in the nominal power output, or cause damage to the elements, or electrodes, of the discharge device, thereby necessitating its withdrawal from use.

It is an object of my invention to provide a new and improved electric discharge device;

It is another object of my invention to provide a new and improved electric discharge de'- vice of the magnetron type.

I t is another object of my invention to provide new and improved structure for supporting the elements of a magnetron of the space resonant type which permits operation of the device at relatively high voltages, and which does not disturb the desired symmetry ofthe electrostatic and magnetic fields required for-satisfactory operation.

It is a still further object of my invention to provide new and improved cathode supporting structure for ultra high frequency magnetrons wherein shielding means are provided to prevent the deposition of conductive material on associated insulating structure,

Briefly stated, in the illustrated embodiment of my invention, I provide a new and improved ultra high frequency electric discharge device-of the magnetron type comprising a space resonant region, orregions, energized in accordance with l the oscillations, or motion, of the electrons constituting the space charge between an anode and a cathode, and in which the cathode is main- -tained in spaced relation with respect to the anode structure by means of an improved rigid cableconstruction, which affords rigid positioning of the cathode without entailing the establishment of excessively high voltage gradients across the insulating parts and which, by virtue of its symmetry, does not materially disturb the magnetic or electrostatic elds required for the most effective operation of the device, or system. In addition, shielding means are positioned relative to the cathode and the insulating structure to prevent the establishmentof aconductive layer s claims. f (o1. 25o-27.5) ,Y

of metalfor material thereonfandan appropriately `positioned and designedY insulator having a long leakage path is employed to eliminateor reduce the probability of an arc-over between the electrode structure and the associated magnetic pole pieces.` Y. Y Y For a better understanding ofmy invention, reference may be had to the followingy description takenin connection with the accompanying draw-ing, and its scope will be pointed out in the appended claims. Fig. 1 diagrammaticallyl illustrates` an embodiment of my invention as applied to: an ultra high frequency magnetron of, the

type employing a metallic envelope or vcontaining member and which includes a pair of permanent- Y ly magnetized eld members.V Fig.,2 is a detailed View of the-anode structure, *andFigB is a de- -netic field pieces oppositely disposed relative to a centrally located anode structure including a space resonant cavity, orcavities; andFig.' 2 'is a detailed view of the anode structure.

Referringparticularly to 1, there is shown anelongated cylindrical containerthelateral wall structure of which is'provided `by a single metal envelope or containing member` I, preferably Ao f tubular form, constructedjof a ferro-magnetic material such as cold rolled steel,` or,the 1 ike,

The ends Voff-the containerare enclosed byfl'anged members 2 and 3 which are welded or otherwise herrmeticallyy joined to the containing member II. The outersurface ofthe envelope orf-member l may be'providewith. a plurality of heat dissipatingmeans such as fins (not shown),

Within the containing member l and approximately at its central region there is provided an anode structure 4 `shown in plan view in Fig. 2. The anodestructure comprises a circular member`which has a relatively large central opening 5 Vand a series of smaller openings r6 Varranged symmetrically about the central opening 5. The central opening ris joined tothe openingsjs Aby means of, a plurality ,of radiallyextendingslots 1.

The anode structure 4, which preferably conmaterial applied before the anode structure is y ,K inserted within the containing member I. A relatively-large circumferentially extending channel-Y material, havingfan'gesj I and l2 at the ends,`

thereof. This sleeve, which may be coated externally with a suitable activating material such energy factor. One of the materials which may f beY used for this purpose is that class of 'alloys including aluminum, nickel and'cobalt. Alloys of this type are described, for example,Y in thev Mishima Patents No. 2,027,994 to No. 2,028,060.

As a means for providing a low reluctance connection between the base endsof the `magnetic as barium oxide, contains a lamentary heating Y element I3 by which the sleeve Il] may be main tained at an electron emissive temperature. One end of the cathode sleeve lil is closed by a/netal disc I4 and the'other end of the sleeve is closed by an apertured disc I5.

I VThe discs I4 and I5.have diameters Vof suicientdimension to substantially shield insulating struc'- ture, to be Ydescribed presently, to prevent. the

deposition of an appreciable conductive layer on ythe surf ace of the insulators; which would`V tend to reduce the operating voltage` of the discharge device, or the systemes a whole, since the condu'ctive layer would-tend to` establish relatively low resistance leakage paths between elements at substantially great .differences of potential. In ther operation "of the .electric discharge device a spacecharge is developed inthe space between the cathode sleeve II) and 'the surrounding anode, Y

structure I by the'application'of a lsuitable potentialimpressed between'the cathode structure andthe containing member I. The containing member I, to which the anode structured is dij rectly connected, may have-impressed thereon a unidirectional potential, such as'apositive potential and the other terminal for the unidirectional circuit' is connected to the cathode structure .by apparatus tol be described presently. I

' The electrons which constitute the space charg are given a spiral'or orbital motion by a magnetic field which is providedby electromagnetic structure, or by permanentlymagnetized eld pieces to be describedv presently. The resultant gyrationsor oscillations of theelectrons constituting the space charge produce excitation of the anode of Yone of theV slots 1. Assuming this point of view,

it will be seen that the operating frequency is in a large measure determined by the dimensions of the openings 6.

In order to provide a magnetic field of sufcient pieces pole pieces I6 and I'I, the pole pieces may be respectively seated upon relatively 'thick disc-like members I8Y and I9 constructed of ferro-magnetic material, such as steel. For the purpose of securingthe pole pieces rigidly to the discs I8 and I9, I may employ clamping rings 2i? and ZI slippedfover the pole pieces and welded to the discVV members.

The desired precise placement of pole pieces I6 and Il with V,reference to the anode structure 4 may AIce obtained by the use of spacing rings 22 and 23'.v As will be observed from Fig.,1, each of these rings is interposed between one surface of the anode 'structure ZI and ytheV surface ofthe apertured discs'24, 25, each disc in Vturn being in abutment with a properly positioned and formed shoulder on the adjacent pole piece as indicated at 2S and Z'I. The spacing 'rings 22.and 23 may be welded in place before vthe pole pieces are inse'rted within the containing member I.

Pole pieces I6 and I I, inasmuch asethese ele,- ments are positioned within the containing'mem- 'ber I, may be employed eis-supporting means for the cathode structure. example, by constructing `the pole pieces I6 and I'I to have alined central openings `cr- centering channels 28 and 29,Y respectively, preferably` Yof circular cross-section and which extend along the axial or'longitudinal dimension of the pole and afford communicating channels through which elements to be described-presently extend or are positioned, and which presentV 36 and 3l in the respective pole i ductor construction for supporting the cathode j tween vthe anode and theY cathode.

intensity to permit the apparatus to function in its intendedrmanner, there are provided Within thecontaining member I tapered magnetic pole pieces I6 and II which are directedaxiallyrof the containing memberl andmay extend in 'close proximity to the upper and lower surfaces Yof the anode structure 4. For presentl purposes, Ythese pole pieces maybe assumed to be permanently magnetized in such a sense that the north pole of one faces the south pole of the other.

To assure Ythe existence of the magnetic Vfield o-f the required intensity, the pole pieces I6 and I 1 should be constructed of a magnetizable substance having a high coercive force and a high centrally within the enlarged opening 5 .of the anode structure-4, and which also is employed-,as a means or conduit for supplying energizing current to cathode heating element I3. Of course,

, one conductor of the cathode is also employed in connection with an externalcircuit'by virtue'of which Ya unidirectional potential isvapplied be- Considering more specifically the concentric cable-construction, I provide-a cable having an inner "conductor 32 and an vouter conductor, 33, preferablyconstructed of a metal such asY nickel or molybdenum, and which are'maintained'in spaced relation with respect to'each other by vacontinuous insulator,

such as a tubular insulator 34.' Conductors@ and 33 are connected ,to externallyaccessible lead-in wires 35 andA 36 which are sealed in yal suitable insulator, suchV asa vitreous insulator 31. In order to facilitate the attachment of the insulator 37 to the body of the dischargedevice, and

more particularly to the flange member 2, I may Y employ a cylindrical metallic member 38 which is welded or soldered to member 2 and sealed to conductor 31. v,

I provide within the channelV 23, an insulator 39, the details of which are shownin Fig3. In-` sulator 39 Vserves as a supporting and centering means for the concentric Acable comprising conductors 32 and V3.", andv closelylts thefchannel wavllrby virtue of the `part 39a thereof ,which closely vengages and is fitted to the 'channel wall.

This may-'be done, 'for Insulator 39 is located near the end of channel 28 in the vicinity of the cathode and is provided with a section 39h of restricted diameter and which extends beyond the pole face 40 of magnetic pole piece I6. In order to place and maintain the insulator 39 in the desired axial position, I provide a tubular spacing member 4I in abutment with the insulator 39 and extending therefrom to the base of magnetic pole piece I6 where it engages or abuts the disc I8. The member 4I is closely fitted to the surface of the chan- `nel wall and serves as a means for preventing undesired axial movement of the insulator 39 and the associated cathode construction. L Y The concentric conductor also serves as a means for supplying current to the cathode heatingr element I3, and the outer conductor 33 also serves as a means for impressing a potential, such as a negative potential, on the cathode. Conductor 33 may have a flanged part 42 at its lower end to engage firmly disc I5, and the inner conductor 32 may be bent over, as shown at 43, to prevent undesired axial movement or stress of the inner conductor relative to the insulating member 34 which is interposed between part 43 and the fianged part 42 of outer conductor 33. A spacing ring 44, preferably constructed of nickel, is placed between insulator 39 and the upper surface of disc I 5, Vall of these members being in close contact and engagement so that the heat transfer from the cathode to the insulators 39 and 45 is minimized.

It will be noted that therestri'cted part 39D of insulator 39 aiiords an appreciable annular space between its surface and the wall of channel 28, thereby providing a long leakage path between the cathode structure and the pole piece I6. In this manner, even though the conductive layer tends to be deposited on part 39h of insulator 39, there is nevertheless afforded a suiciently long leakage path to reduce or minimize the probability of arc-over between pole piece I6 and the cathode structure.

Within the channel 29 of magnetic pole piece I'I, I provide an insulator 45 which centers the lower end, and particularly disc I 4,'of cathode construction and supports a metallic pin 43 which is turned over at its upper end and to which the lower terminal 41 of cathode heating element I3 is welded or soldered. The upper terminal 48 of the cathode heating element is welded or soldered to the inner conductor 32. I also employ between disc I4 and insulator 45 a metallic ring, such as a nickel ring 49, for firmly maintaining the cathode construction and the insulator 45 in the desired ixed spaced relation and for minimizing heat transfer. Inasmuch as insulator 45 is iirmly positioned against the wall of channel 29, it will be appreciated that axialv as well as radial movement of the cathode construction is prevented.

As a means for Vextracting energy from the discharge device, I may employ an output electrode means, such as a loop 50, extending into one of the openings 6 and which may constitute an extension of a center conductor 5I of a concentric transmission line comprising conductor 5I and an outerconductor 52 which aresealed Y which may be connected to the concentric trans'- mission line comprising conductors 5I and 52. 'I'he various space resonant regions, or cavities, are excited or energized in accordance with the oscillations or motions of the electrons constituting the space charge within the region defined by the cathode sleeve I0 and anode structure 4. The period of oscillation .of the electrons constituting the space charge, or a portion thereof, is correlated with respect4 to the natural-resonance frequency of the various space resonant regions comprising openings Ii and slots I to` maintain the regions in oscillation, and energy may be derived from all the regions through the loop 50 and conductors 5I and 52.

Discs I4 and I5 shield insulators 45 and 39, respectively, from the cathode and thereby prevent the electrons from striking the insulators, which would otherwise be the case due to the axial movement of those electrons which pass beyond the boundaries defined by the top and bottom surfaces of anode structure 4. Even though the sides of the insulators collect any conductive coating incident to the relatively high temperature of the cathode, the increased length of leakage path will prevent breakdown which would otherwise result from creepage along the surface of an improperly positioned and designed insulator.

Another advantage ofthe construction which I provide is that the insulating paths, particularly that of insulator 39, with respect to ground' are many times greater than that afforded by the prior arrangements, and consequentlyfor a given applied voltage it is possible to use materials having a somewhat smaller dielectric strength, Furthermore, by virtue of the above described construction, the tendency to produce short circuits in the cathode assembly,` is materially decreased since the two terminals or conductors for the cathode heating element I3 are well insulate'd from each other and are of strong mechanical construction.

Some of the other advantages incident to my above described construction for the electric discharge device include ease of mechanical assembly made possible by the simplicity of construction, particularly the single upper insulator and the rigid concentric cable.

Elmer D. McArthur, Serial No. 447,903, filed June 22, 1942, and which is assigned to, the assignee of the present application.` Other features relating to certain aspects of the rigid cable construction are disclosed and broadly claimed in copending patent application Serial No. 465,424 of Ralph J. Bondley, filed concurrently herewith and'which is also assigned to the assignee of this application.

While I have shown and described my invention as' applied to a device embodying various elements diagrammatically shown, it will be obvious to those skilled in the art; that changes and modifications may be made without departing In addition, the generally symmetrical configuration ofthe ele- What I claim as new and desire to secure by Letters Patent of the United States is:

l. An electric discharge device comprising a pluralityvoi enclosed co-operating electrodes including an anode structure having a centrally located opening therein and a cathode, a pair of magnetic pole pieces positioned on opposite sides lof said anode structure and each including a channel lying longitudinally of the pole'piece and v being alined With respect to each other vand with respect to said opening', a pair of insulating means each pcsitioned'in one of said channels andv each having a portion engaging 'the walls of the channel at a regionspaced from the pole face anda second portion extending from the channel beyond the pole face, Vsaid last mentioned portion having a smaller cross section than the channel, and means extending through said insulating means supporting and centering said cathode.

2. An electric discharge device comprising a plurality of enclosed (zo-operating electrodes including a, thermionic cathode including a heating element andan anode structure surrounding said cathode, a pair of magnetic pole pieces spaced on opposite sides of said. anode structure and each having therein a channel of circular cross section positioned longitudinally of the pole piece, means supporting said cathode and for supplying cur` rent to said heating element comprising a concentric -cable construction including an inner and outer conductor extending through the channel of one of said pole pieces, an insulator fitted in the channeloisaid one pole piece centering and 1 supporting said cable, and aY tubular spacing member extending from the vicinity of said insulator toward the base of said one pole piece.

3. An electric discharge device comprising a plurality of co-operating electrodes including 'a cylindrical cathode and an anode structure of annular form having ltherein a central opening within which said cathode is positioned, a pair of magnetic pole pieces spaced on opposite sides of said anode structure, said pole pieces each h'aving therein a channel positioned; longitudinally of the pole piece, a rigid cable construction lying within the channel of one of said pole pieces supporting said cathode, an insulator in said channel near the end thereof facing said anode structure supporting and centering said cable, a second insulator in the channel of the other pole piece and includinga member centering said cathode, and a pair of shielding members at the ends of the cylindrical-cathode to prevent the deposition of conductiveY material on said insulators.

4. An electric discharge device comprising a plurality of co-operating electrodes including a cathode having a cylindrical sleeve provided with an electron-v emissive surface and Y an annular anode, structure havingy therein a centrallopening within which said sleeve is positioned'. a pair of magnetic polepieces spaced on opposite sides of said anode structure, said polepieces each-havingtherein a channel vextending longitudinallyofthe pole piece, a rigid cable construction lying within the channel of one or" said pole pieces supporting said cathode andcomprising an inner member anda concentric tubulan outer member, afrcathodeheating element'substantially surrounded byv said sleeve and having `one lterminal conductively` @soneries tof Said-inner Conductor, aniinsnlator positioned within 'the channel Vof the other pole piece near'the region of the pole face, and a metallic pin positionedv bysaid insulator and connected to the other terminal of said cathode heating'element and said cathode.

5. An electric discharge device of the magnetron type comprising o, plurality of enclosed cooperating electrodes including a thermionicicathode including a cylindrical sleeve coatedowith an electron emissive material and a cathode heating element Within said sleeve, an anode structure of general circular coniiguration provided with a circularY center opening Within which said cathode is positioned and including a space reso'- nator to be energized in accordance with the motion of the electrons constituting the space charge between said cathode and said anode. structure', a pair of magnetic pole pieces respectively positioned on opposite sides of said anode structure for establishing a magnetic eld Within the space dened by said cathode and said anode structure and each having therein a channel positioned longitudinally of the pole piece, means supporting said cathode comprising a concentric` cable extending through the channel of one of said pole pieces and including an inner conductor, an' outer concentric tubular conductor and an insulating material therebetween, an insulator positioned in the channel of one of saidpole pieces and inl close engagement' therewith supporting and centering said cathode', means connecting one terminal of said cathode heatingelement to said outertubular conductor, means comprising a pin connecting the other terminal of said cathode heating element to said cathode structure and constituting a partof an energizing circuit for said cath'ode heating element, a' second insulator positioned Within the channel of the other pole piece and centering said pin, and a pair of shielding members closing the ends of the cathode sleeve and of dimensions suiicient to shield said insulators Yto prevent the deposition of conductive material thereon incident to the vaporization of electrons from the emissive surfaceof said cathode.

6. An electric discharge device comprising a plurality of enclosed co-operating electrodesV including a cathode and an anode structure surrounding said cathode, a pairof magnetic pole pieces spaced on opposite sides of said anode structure', said pole pieces each having therein a channel positioned longitudinally of the pole piece, means positioning said cathode comprising a'fconce'ntric cable construction attached to said cathode andextending through the channel of one of said pole pieces, an insulator supporting and centering said cable and' close-ly'v engaging the channel Wall of said pole piece, and a copper sleevein abutment with said insulator andl closely tted tothe channelwall and extending from said insulator to .the baseofsaid one polev piece. 7. An electric discharge device comprising a plurality of co-operating'electrodes including a cathodel and an anode structure surrounding said cathode, a pair of magnetic pole pieces' spaced onopposite sides of said yanode structure'and each having therein a channel of vcircular cross secing element and extending throughV the channel of one of said pole pieces; an insulator centering and supporting said cable located Withinv the challlieiwithin.; the; vicinity cisaidA cathode and structure and having pole faces of substantially circular cross section, said pole pieces each having therein a channel of circular cross section positioned longitudinally of the pole pieces and in alinement with each other, means supporting said cathode comprising a rigid concentric cable construction including spaced inner and outer conductors and extending through the channel of one of said pole pieces, an insulator in close engagement with the channel wall of said one pole piece and extending beyond the pole face thereof in the direction of said cathode,V a centering insulator in the channel of the other pole piece and supporting a metallic pin in electrical contact with said cathode, and a pair of shielding discs positioned between said cathode and said pole faces to prevent the deposition of conductive material on said insulators incident to the vaporization of electrons from the emissive surface of said cathode.

GEORGE M. WHITE.

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