US2452077A

US2452077A - Electric discharge device

Info

Publication number: US2452077A
Application number: US519077A
Authority: US
Inventors: Percy L Spencer
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1944-01-19
Filing date: 1944-01-19
Publication date: 1948-10-26
Anticipated expiration: 1965-10-26

Description

Oct 2-6, 1948. P. L.. SPENCER 2,452,077

A ELECTRIC DISCHARGE DEVICE lFiled Jan. 19, 1944 l 2 sheets-sne'et 1 A v .al

N l L yml;

Oct. 26, 1948. F L. SPENCER ELECTRIC DISCHARGE DEVICE Filed Jan. ,19, 1944 2 Sheets-Sheet 2 Patented ct. 26, i948 ELECTRIC DISCHARGE DEVC Percy L.' Spencer, West Newton, Mass., assigner to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware f Application January 19, 1944, Serial No. 519,077

This invention relates to a magnetron oscillator Vwhich is adapted to generate oscillations of hyper frequency and having Wave lengths of the order of a few centimeters or less. Heretoiore such oscillators have required a relatively complex anode configuration which was difficult to construct accurately and which tended to produce spurious oscillations, thus decreasing the eiliciency of the oscillator.

An object of this invention is to devise a magnetron having an anode of simple construction wherein the frequency of oscillationfis xed by a simple and easily constructed configuration.

Another object is to provide a magnetron of the above type in which the oscillations are proguide;

Fig. 2 is a cross-section taken along line 2-2 of Fig. 1;

Iig. 3 is a diagrammatic perspective View broken away to show an alternative mode of coupling the tube of Fig. 1 to a wave guide;

Fig. 4 is a cross-section of another embodiment of the invention wherein a plurality of oscillating slots are utilized;

Fig. 5 is a cross-section taken along 5-5 of Fig. 4; and f Fig. 6 is a fragmentary section similar to Fig. 4 showing an alternative mode of coupling to awave guide.

v A The magnetron illustrated in Figs. 1 and 2` comprises a cylindrical anode I of suitable conducting material, such as copper, and a centrally located lamentary cathode 2 of the thermionic type. 'Ihe anode and cathode are contained within a highly evacuated glass envelope 3 containing a reentrant stem V4. The anode I is supported by a conducting standard 5 sealedin the stem 4 and provided with a lead-in conductor E which is sealed through said stem and provides an external electrical connection for the anode.

.The cathode 2 is supported Iby a pair of con- 40mm. (o1. 25o-27.5)

ducting standards l, likewise sealed in the stem Il and each provided with a lead-in conductor 8 sealed through said stem in order to provide external electrical connections to the cathode. The cathode 2 may be provided with heating current through leads 8 so as to raise it to a temperature of thermionie emission. Light metal shields 9 may be provided at opposite ends of the electrode structure so as to prevent electrons from being projected throughA the lends of the anode I toward the glass walls of the envelope 3. These shields may be conveniently supported from the cathode standards 1. Magnet poles I0 and I I are provided in order to create a magnetic eld extending axially along the anode cylinder l and substantially parallel with the lamentary cathode 2. The anode I is provided with anv elongated slot I2 cut through the wall of said anode in a direction substantially parallel with the axis of the anode cylinder. The slot I2 is narrow as compared with its length. Also its length is selected so as to be substantially onehalf the Wave length of the oscillations which the magnetron is adapted to generate.

When in the arrangement as described above the cathode is heated to temperature of thermionic emission, a suitable Voltage is impressed between the cathode and the anode, and the magnetic field is of the proper value, oscillations will be generated in the anode cylinder I around the slot I2. These oscillations will have a wave length which is substantially twice the length of the slot I2.

I believe that the operation of the device is substantially as follows. The magnetic iield set up about the cathode 2 causes the electrons, which are emitted from said cathode and accelerated by the anode voltage, to travel in orbital paths around the cathode 2. Thus in the vicinity of the slot l-2 electrons tend to travel past said slot in a direction normal to its length and induce varying electric charges on opposite sides of said slot. This tends to set up oscillations around the slot at a frequency at which the slot is resonant. The voltages set up across the slot react on the electrons passing the slot and tend to bunch these electrons in such a way that pulses of electrons periodically pass theV slot with such periodicity and phase as to reinforce the abovementioned oscillations. As a result strong oscillations are generated. which tend to radiate hlyper frequency energy from the vicinity of said s ot. I

The energy radiated from the slot I2 may be guided in a desired manner by inserting that portion of the anode containing said slot into a wave guide I3. For example, the wave guide I3 may be provided with an opening M in one side thereof, and the upper end of the envelope 3 may loe inserted through said opening I4 so that the slot I2 lies transverse to the wave guide I3. Under these conditions I believe that the energy com ing' from ithe slot. i 2 tends to .exciterthe zwave guide I-3in also-cal1edtransverse magnetic mode in which the magnetic vectors are transverse to the wave guide and the electric Vectors within the Wave guide are substantially paralleLtothedirection in which energy is propagatedthrough the Wave guide. The wave guideet redesigned, to have proper dimensions fompropagatingzzthercscillations generated by the magnetron and `is closed at one end by a conducting. surface .I5

`mayoccur. 'iPoles 23 ,.andiZd, 1 of: a 4lsuitably enerspaced the proper distancefrom the 'slot`i2 all in accordance with well known wave guideprin'-y ciples. Under these conditions the energy gen- ,eratedwby. the -magnetron willi loe .propagated @through thewave .guide i.3;in .the,-directicn of :thearrow P assshowninf-Fig; 2.

`(Instead Aof. coi 1.1: ling A.th-e.magnetron tor-a wave vz; guidesas described .aboveg various other coupling :arrangements ymay ,be devised. @For-example, ,las :,sllownfin 3, Lthe; magnetron may be inserted r netonnet, end of. afrectangular waveguide l. IY3 with the, axisof .the anode Ac :ylind-er,l i substantially par allel-'withxthelonga' dimensionof :the cross-section L ofsrsaidwavagude. .Like-wise the,lslot-l2 lwill he .'parallelttotsaidz'longt dimension. f Underthese con- ',ditions energyiradiatedffrom the=slot l'-lwillbe ,l propagated-.along l the wave jguideni 3. I believe -thatzin thiscase thelenergy .isf propagated in a so- ;l

.-called.transversefelectricv mode `linzwhich .theelectrickvectorsextendk across .the narrow vdimension I "',Qffzthe rectangular-,wave guide A 13..'.andethe -magnetic :vectors :extend substantially i parallel -to f the direction ogpropagatlcn tofwthe energy. through Y:th'ewaye guide.

@In tmest i instances it; mayI be tdesired .-.tozutilze L. a plurality ,ofioscillatingi slots instead: of:.asingle slot, as shownrin Figa-1113. Such; ayplural :slot :arrangement mayi taker-the `form aeg-shown; in Figs. .4 fand-1A 5 .Thisiemhodiment comprises aghollow :cathode: :sleevefil r,within :which-uis rrcontairreel.7 a :heater lament I-'Ln Surroundingithexcathcdepl y is an; anode gcylindernl iormedepf.isuitably,con

ducting, material, kSui-1h as, copper. *,TI-helanodacyl- `findemS;,Dr,ovided with-aiplurality'pf slots dit each similar-atoth'eeslotf` |22 ,tassdescribedlin;connection with Figs. l and 2. As indicated, :leach: ofzithe :slots .I 9; should., halles .atlengthlzsubstantallyaequal -.t c onehaifmf ',thefwave length ofitheioscillations `to,virrey.generated. Y--Plllhenf aimagnetic ield fis :set Mllpvlarallel .tok .ftheK axis: ofrfthe *.pcathoderl E as will beedescribed- :be-low, oscillations are generated :aboutteach .of atheislots 19. .Slrrorderto teedrtliese toscillations.;intoyascomrnonlzoutput, Aaa.; common i a fpair sof poleepieces :2 Mandi 22 'aref'.hermeticall-y gized electromagnet or of. a ypermanent magnet,

are placed in contact with the pole pieces 2| and respectively.

. 4Thecathode cylinder I6 comprises 4a tubular conducting sleeve coated with the usual electron emittingzoxides.z.0ne end of the heater I1 within .fsaidzsleeveis;electrically connected to the top 'closed,end thereof, The sleeve I6 is formed with a ,lower reduced tubular end 25 which passes through an opening 26 formed in the pole piece 2|. The. lower end of the reduced tubular section 25 fits into a recess in the upper end of a con- Nducting rod- 21 provided-.With-.a.borefaZBi' through which `an ,insulated ,wire 29 connected ,to-fthe lowerrend-.of the heater II passes. `A'Ihelowerj end of said insulated .wire 29 passes out throughva lglass `seal l30 carried from the lower end .Oi-lthe yrod 21 byian'zintermediate-sealingvsfleeveI. Surrounding the rod 21T-isa tubular ;metal.1shell,.32, the upper'fend of lwhich isfinserteddntoffanenlarged end of the openingsl.:ofthepolejpiece vI and hermeticallyljoined;therewithasfbyfbrazing. Tothe .lower endet .the-fshell-w32 lisfisealed .a glass tube-3,3,vthe lower,endfof-which is in turn sealed to arnetalfsealingqup hermeticalglyifastened to theextelior.- oith'eirod 21. .'Theconductor A2.11 serves lasy an externalfelectr-ical; .connectionto the heater l'Lwhile the cup .34: serves asian external electrical connection to .zthef-cathode s1eeve,as,well .as to theupperrendof saidzheater. Suitable electricalfconnectionfcan-,be made tothe anode cylinder f. I8.at anyypointontthe ring f 2'0sor at any of the conductingeeiements.i-connected thereto.

zIn- .order to;lead,.theenergyifromi(theswavegguide 281110 asuitableutilizationvdevice, .ag-coupling loop -35 t-isxinterposed :inuthe space: withinfsaiid :wave

guide with the axis of said loop interceptedabyithe :magnetici-eid '.'withinfsaidswave guide. .One -end Y,of i; the-.coupling 'loopc :fis-:electrically :connected -top-thetinnerendrofralpipesi hermeticallynsealed through a wall of the ring 20. The outer '.endiof said couplingdoopzf is..connested-3fty` a conductor 31 which passes through said pipe 36 and extends yithrlough;aaglass; sea1e38lcarried: at the outerfen y.of saidpipe. l

When :the-devicaas describedaboveissinioperation,=.ith'e .oscillation energy generated around each slot .i Suisifedlintoftherwaveguide 20twlierein it is propagated to the lcouplingloopf and con- ,ductecl 'romfsthecstructure'i'byrzthe concentric' line arrangement associated with said coup1ing`loop. In:order:forftheloperation tolproeeed wthmaxibe spaced from each other around the-anodecyl- Linder I8 loyaal-distance :substantiallylequal toone- Ahalf ofi-the i wave lengthl oi they oscillations lwithin Vythe;wavenguide 20. iilfbelievethatfunder-the above conditions the slots 21'91exciteJ-the-wave x guidef'lZfD @ther. means fofifcoupling the oscillator-y Lenergy within'thewave:guidef to anlexternalewaveguide may-be'; utilized. Y VFlorexample;- as shown inlFig-.l-, ai hollow iwan/el guideYSQ `runway-'be'- connectedtothe exterior of the ring 20 and coupled to the interior of said ring by a coupling iris opening 40. It is to be understood that the wave guide 39 is hermetically sealed 01T at its outer end in a, suitable manner, such as shown for example in the copending application of William C. Brown, Serial No. 506,608, led October 16, 1943.

I have found that devices constructed in accordance with the foregoing principles can be made accurately with a minimum of diiliculty. Further, such devices tend to oscillate at the desired output frequency and are remarkably free from tendencies to generate spurious oscillations which might tend to decrease the efciency thereof.

Of course it is to be understood that this invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art.

What is claimed is:

1. A magnetron comprising: a cathode; an an ode surrounding said cathode; and means adjacent said cathode and said anode for establishing a magnetic eld in a direction transverse to the path therebetween; said anode having a plurality of perimetrically closed slots formed therein and spaced from each other around said anode by a distance substantially equal to the length of a half-Wave at the frequency desired of the output of said magnetron; each of said slots being of a length substantially equal to a half-wave length in a direction parallel to that of said magnetic field.

2. A magnetron comprising: a cathode; an anode surrounding said cathodeiand means adjacent said cathode and said anode for establishing a magnetic iield in a direction transverse to the path therebetween; said anode including a toroidal cavity resonator, the inner wall of which is provided with a plurality of perimetrically closed slots spaced from each other around said wall by a distance substantially equal to the length of a half-wave at the frequency desired of the output of said magnetron; each of said slots being of a length substantially equal to a halfwave length in a direction parallel to that of said magnetic field.

3. A magnetron comprising: a cathode; an open-ended anode surrounding said cathode; and a pair of pole pieces sealed, respectively, to the open ends of said anode for establishing a mag- .netic field in a direction transverse to the path between said cathode and said anode; said anode having a plurality of perimetrcally closed slots formed therein and spaced from each other around said anode by a distance substantially equal to the length of a half-wave at the frequency desired of the output of said magnetron; each of said slots being of a length substantially equal to a half-wave length in a direction parallel to that of said magnetic eld.

4. A magnetron comprising: a cathode; an open-ended anode surrounding said cathode; and a pair of pole pieces sealed, respectively, to the open ends of said anode for establishing a magnetic eld in a direction transverse to the path between said cathode and said anode; said anode including a toroidal cavity resonator the inner wall of which is provided with a plurality of perimetrically close-d slots spaced from each other around said wall by a distance substantially equal to the length of a half-wave at the frequency `desired of the output of said magnetron; each of said slots being of a length substantially equal to a half-wave length in a -direction parallel to that of said magnetic field.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,523,776 Hull Jan. 20, 1925 2,063,342 Samuel Dec. 8, 1936 2,084,867 Prinz et al June 22, 1937 2,129,713 Southworth Sept. 13, 1938 2,154,758 Dallenbach Apr. 18, 1939 2,241,976 Blewett et al May 13, 1941 2,247,077 Blewett June 24, 1941 2,250,698 Berline July 29, 1941 2,284,751 Linder June 2, 1942 2,295,315 Wolff Sept, 8, 1942 2,348,986 Linder May 16, 1944 FOREIGN PATENTS Number Country Date 215,600 Switzerland Oct. 16, 1941