US2768326A - High frequency electron tube - Google Patents

Description

Oct. 23, 1956 B. BROWN ET AL HIGH FREQUENCY ELECTRON TUBE 3 "Sheets-Sheet 1 Filed Feb. 27, 1953 N r p mw@ w 5m H mmm. M HH 7 wm. Uwm N BMM ,a H A :IL F WN E NN E VE N www, mw MN 0 my MMM WWMQMWLTMTMW JMIIII. WIIIIIMIIHLI mi m2, m m v Q LM W .|n n X J m50 Qm www /J uw, mNCm ,mwm m .n WANN QN \N \Q\. llmu www Oct. 23, 1956 B. B. BROWN rs1-AL 2,763,326

HIGH FREQUENCTELECTRON TUBE @ned Feb. 27, v1953 3 Sheets-Sheet 2 ORNE Y HIGH FREQUENCY ELECTRON TUBE lFiled Feb. 27, 195s 3 sheets-sheer 3 ILXVTOR. BARRE/waff 5. B/Pow/v LESL/E'KaVAc/f ND MoH/V .M4 Smc/#m7 TTOR NE Y United States Patent HIGH FREQUENCY ELECTRON TUBE Barremore B. Brown, Morristown, and Leslie Kovach, 'Whippany, N. J., and John W. Seachrist, Lancaster, Pa., assignors to Radio Corporation of America, acorporation of Delaware Application February 27, 1953, Serial No. 339,316 13 Claims. (c1. 3151-36) This invention relates .to high frequency electron -tubes in which elements in the tube form an -appreciable portion of a high frequency circuit. More particularly vthis invention relates to high frequencyelectron tubes wherein the electrode structure is completely enclosed in avacuum envelope,

v Heretofore such structures have proven extremelycom.- plexfrorn the standpoint of their manufacture and .have presen-ted serious problems in connection with providing adequate .adjustment and tuning, cooling of various parts, and a shock-proof structure while maintaining ,simplicity and ease of manufacture as well as an overall high degree .of precision, long life and low cost. In connection with such high frequency devices, the frequency at which the device is intended to operate determines the size of parts such as electrodes, tuning devices and the like. Thus, size may not readily be varied in accordance `with desired thermal dissipation.

vSerious problems have been encountered in the past in providing a structure having stability over along useful life. One specific problem relates to .providingcomposite lseals such as glass or ceramic to metal which are capable of withstanding the `high temperature ,bakeout process necessary to long useful ylife and stability. Thus, in the past an inordinate amount of time and cost went into providing an adequate support structure vand envelope which heretofore proved to be useful only ,with the particular device in hand and no others.

It is therefore a principal object of this invention .to

provide a structure for a high frequency electron 1tube particularly .adaptedfor enhanced merit .and long life.

Another object is the `provision .of `a stem and support structure for a high frequency device whereinall composite seals such as ceramic or the like to-.metal are relatively small and all are located at one part, of the device, which structure is adapted for .use ina .wide variety of high frequency electron tubes, and whichstructure is readily fabricated and tested outside the vacuum envelope of the device in which it is to be ,ultimatelyl utilized.

Another object .is .the .provision of such .a v.device wherein a stem andmount structure is provided inconjunction with a radio frequency ystructure kadapted yfor adjustment and tuning, vall being arranged to ensure enhanced life, lv.as well as ease in manufacture.

Still .another .object is the provision of a :magnetron structure wherein a stem andmount structure -is provided in lconjunction with a high frequency structure adapted for adjustment and tuning, all being arranged to ensure-enhanced life, efficient cooling, as WGH yas ease in manufacture.

In accordance with this invention a unitary stern and mount structure is provided suitable for supporting a tuning mechanism as well as the electrodes of a high frequency .electron tube such as a magnetron; -the mount structure ,including a goodV thermal path for cooling'an anode by conduction as well as means for adjusting the tuning of the device. The seals Yincorporated `in ICC the mount structure which form part of the vacuum envelope lend themselves to pre-.testing prior to sealing-in of the device. The mount is sealed to a simple glass envelope, the outline of which is unbroken by the passage therethrough vof other members.

Still other objects as well as advantages of this in,- vention will be apparent from the following description when read in conjunction with `theaccompanying drawing in which:

Figure 1 is Ia sectional View taken on line 1--1 `of Figure 2 of a ,tunable magnetron constructed in laccordance with kthis invention:

Figure 2. is a sectional View thereof taken on the line 2-2 of Figure l;

Figures 3 and 4 are transverse sectional views taken on lines 3 3 and 4 4, respectively, of Figure l; and

FigureV 5 is vaV plan View of the magnetron partially broken away for convenience.

One ltype of high frequency electron tube in which this invention is advantageously used is the magnetron. rIIherefore, while this invention will now be described in .detail in connection with such a device, it is -to be understood that this invention is not to be limited to magnetrons but is also useful in other high frequency tubes.

Referring now to the drawings tin ydetail, .electron de.- vice 10, in this instance a tunable multi-cavity magnetron, comprises a hermetically sealed vacuum tight composite glass and metal envelope which, Vas shown, -includes .tubular dielectric bulb 11 of glass. Envelope bulb 11 is unbroken in outline except at one end where it is sealed to .a dielectric vdisc or button-like stem member 11 of glass which is sealed at 13 to a member 12 of relatively thin cross-sectional thickness .and which is generally tubular. Member 12 is metallic and is constituted of such `metals Ias will readily seal to glass such as 4the rwell known `glass 'sealing alloys. Tubular vmember 12 .extends into envelope bulb 11 and at its externalend has an inwardly turned flange brazed vacuum tight at its periphery 14 to an elongated ,tubular vmemberlS intermediate kthe ends thereof. Thus, the member 12 serves las a means for joining the glass 4disk 1,1 and the ,tubular metal .member A15 ,in air or lvacuum ,tight relation. As clearly shown, tubular member 15 .has a thick wall .and is substantially thicker in .cross A.section than tubular member 12. Furthermore, tubular ,member 15 has :one end extending .through tubular member 12 into bulb 11. The composition .of tubular -memberlS is particularlychosen to provide a high conductive thermal path and may be copper or Vthe like. Tubular member 15 `is Iconnected adjacent its other end to a massive copper mounting disc 16 by means of which electron deviceltl may be rigidly mounted in suitable apparatus.

Coaxiallyfmrounted with respect to tubular member-15 and extending through the .same is elongated tubular member `17 which, as will be Vmore fully pointed out hereinbelow, functions as a Ytuning rod and also as .an exhaust tubulation. Tubular member -17 is in snug .sliding engagement with a metallic disc 18 through which it extends; disc-,18 being connected to tubular member 1S, as indicated, .at the end 19 thereof. vOne end of tubular member 17 extends inwardly into bulb 11 beyond .the inner end of tubular member 15. The `otheror outer end of tubular member 1-7 extends outwardly beyond inner end thereof formed by a plunger'21 rigidly vcon-Y nected thereto as shown. Adjacent the inner en d of tubular member 17 an annulardisc 22'is mounted thereon and sealed thereto vacuum tight at 23 as by brazing or the like. The periphery of disc 22 is connected in a vacuum tight manner to a thin walled tlexible member 24 which functions as a bellows and which is in turn sealed to the inner end of tubular member 15. As will be more clearly pointed out, the foregoing arrangement permits mechanical adjustment to be made between the centrally located tubular member 17 and the remainder of the thus far enumerated component parts of electron device 10. This follows from the fact that bellows 24 is formed by the thin flexible wall having a plurality of folds as shown which renders the same -axially extensible and retractable.

To intermediate tubular member 15 which extends in the region between outer member 12 and innermost member 17, a massive highly thermally conductive support member 25 is connected and as shown bridges bellows 24. Specifically, support member 25 is a U shaped yoke having a centrally located aperture in its base through which tubular member 15 passes and is joined thereto. Support member 25, as was pointed out in connection with tubular member 15 and mounting disc 16, is of good thermal conductive material and is joined to member 15 so as to reduce heat isolation to a minimum.

It may be well to point out at this time that the structure thus far described constitutes a highly useful support and lead-in subassernbly. During the manufacture of electron device 10, bulb 11 and disc 11' are initially two separate and distinct parts. As most clearly shown in Figures 2 and 3, disc 11 has a plurality of lead-in pins 26 sealed therethrough and arranged in an annular array having a relatively large diameter. As previously indicated disc 11 is sealed to member 12 and only after the assembly of electron device is otherwise complete is disc 11 joined to bulb 11 by well known glass to glass sealing techniques. One extremely important advantage of the present construction resides in that only one composite glass to metal seal is involved while the usually troublesome metal to metal seals are not only maintained small in area but now may be tested to determine the efficiency thereof before being incorporated in a nished electron device. Thus, all the vacuum tight joints of the completed device except the pinch-off of member 17 and the seal joining disc 11' to bulb 11 are readily tested. Only such subassemblies free of defects are utilized to complete the assembly of device 10, thereby making possible a substantial reduction in the cost thereof.

One type of device in which our invention has proven particularly advantageous is electron device 10 shown by way of illustration and which further includes a cavity resonator 27 which forms a tuning cavity closely coupled through an iris to a multicavity magnetron anode 28. Cavity resonator 27 has two sets of side walls 29, 29 and an end wall 30 having an H-shaped iris opening 31 formed therein. The pair of opposed side walls 29 have extensions 29 (Figure l) which are rigidly bolted to the free ends of support member 25 and have large areas in contact to form a good heat exchange connection. A pair of opposed spaced apart elongated metallic plates 32 are each connected at one end thereof to end wall 30; iris 31 being located with the bar portion of its H shape extending centrally through the portion of end wall 30 between plates 32 and parallel to the latter. A second pair of metallic plates 33, each connected to end wall 30, the corresponding one of opposed side walls 29 and one of the plates 32, serve to maintain the latter in parallel spaced relation. As described, cavity resonator 27 when excited has an electric field distribution therein having maximum intensity or concentration in the region between parallel plates 32. It is to be understood that the walls and plates of resonator 27 are of conductive metal or the like such as copper.

Each of the opposed side walls 29 has an aperture,

the apertures being in opposed relation with a cupshaped member or shield 34 extending through each of the apertures into the cavity of resonator 27. Cupshaped members or shields 34 are each connected to and supported from one of the walls 29' and each has a slot 35 formed in the base thereof. As most clearly shown in Figure 2, shields 34 form wells or recesses in walls 29 in each of which an electron gun structure 36 is suspended from a sheet of insulative material such as mica 37 each of which is securely connected to one of the side walls 29. Leads 38 extend in spaced relation` to one lof the electrodes of the guns 36 and at their other ends are each connected to a leadin pin 26. The leads 38 for each gun 36 are sandwiched between one of the mica sheets 37 and a second mica sheet 39 also supported from side walls 29 as shown in Figures 2, 3 and 4. Magnetic pole pieces 40 are mounted one behind each of the guns 36 and connected to walls 29.

Each gun 36 comprises three spaced electrodes including a cathode 36', an apertured control grid 36" and an apertured accelerating electrode 36". The shield 34 of each gun 36 acts as the electron collector for the other n depending on which gun is being operated.

' wave guide As most clearly shown in Figure l, tuning plunger 21 is slidably inserted between parallel plates 32 and has the same width as the plates. Movement of central tubular member 17 is transmitted to plunger 21, axial movement of which allows tuning over the frequency range of the device which may, for example, be from approximately 6575 to 6875 megacycles.

Magnetron anode 28 is a conventional multiple vane double strapped structure comprising an anode block 41 having a cylindrical chamber in which are mounted a central cathode 46 and an annular array of radial vanes 41 forming cavity resonators 41" therebetween, as clearly shown in Fig. l. Anode block 41 is connected to end wall 30, as well as plates 32 and 33, in good heat exchange relationship and is provided with an aperture 41 which opens into one of the resonators 41" and communicates with iris 31. Thus magnetron anode 28 is closely coupled to cavity resonator 27. Anode block 41 is provided with a second H-shaped iris 42 by means of which the magnetron is closely coupled to an output not shown. The output wave guide is readily mounted adjacent the outside of the end of bulb 11 and closely coupled through the glass wall to the magnetron anode 28. An annular disc 43 connected to anode block 41 carries an annular disc-shaped mica 44 and snubbers 45. The snubbers 45 engage the interior surface of bulb 11 and serve to firmly position the free end of the structure centrally therein. Magnetron anode 23 additionally comprises the usual magnetic pole pieces 47. The leads j for the magnetron electrodes such as the anode, cathode and heater leads are also joined to lead-in pins 26. This is most clearly shown in Figure 5 where lead 4S is shown extending from one end of cathode 46 to one of the lead-in pins 26.

While the electronic operation of such devices as electron device 10 is described in considerable detail in an article entitled A 7000 megacycle developmental magnetron for frequency modulation by H. K. Jenny, appearing at page 202 of the RCA Review, volume XII, No. 2, dated June 1952, it is not believed necessary to treat the subject at such great length herein. However, it will be well to point out that during operation of such a device the heat generated in anode block 41 is conducted to cavity resonator 27 and in turn conducted to support member 25 by way of extensions 29". Similar ly, the heat generated during operation of one or the other of the modulating guns 36 is conducted to support member 25. As was pointed out, support member 25 affords a highly conductive thermal path and, together with intermediate tubular member 15, conducts the heat generated within the envelope of electron device 10 to the exterior thereof. The arrangement of lead-in pins' 26 about circle having a relatively large diameter affords a highly desirable electrical isolation between Ithe various leads.

From the foregoing, it is apparent that there is provided a vhighly compact rigid structure `which lends itself to the high degree of precision required in the lmanufacture `of such devices. The structure shown may be readily mounted in the .apparatus with which it coacts Without requiring any complicated manipulations to be performed. While this invention has been described in great ldetail in connection with a tunable multiple cavity magnetron, it .is believed apparent that applicants invention is also suitable lfor use with other high Afrequency electron devices wherein the internal structure of the device constitutes appreciable portions of the electrical circuit, thereby prec'luding employment of the usual practice of increasing the size of such elements, as for example kthe anode, in order to improve the thermal dissip-ation characteristic thereof. By arranging the various leads and the tuning at one end of the envelope, as well as `providing the required heat dissipation or cooling through the same end, the other end .of the device is available for coupling to an output circuit such as a wave guide in an extremely simple manner. Therefore, it is not intended that this invention be limited to the exact construction set forth but to claim all modications thereof that come within the scope of the appended claims.

In the claims, the term electrode assembly refers to the electrodes supported bythe stem structure (11, 12, 1S, 17 and 25). As shown in t-he drawing, this assembly would include one or more of the magnetron anode block 2S, cathode 46, tuning .resonator 27 .and plunger 2i, and modulating guns 36.

What we claim is:

ll. A high frequency electron tube comprising ,a vacuum envelope including a hollow dielectric body, an electrode assembly .and a stem structure .supporting said electrode assembly in said hollow dielectric body, said stem structure comprising a dielectric member, an elongated metallic tubular member sealed Athrough vsaid ldielectric member, said .dielectric member being sealed to said hollow dielectric body and closing the same, means including an exhaust tubulationclosing said tubular member tothe external atmosphere, an array of .lead-in members surrounding said tubular member and sealed through said dielectric member, and -a yoke connected to said tubular member and to said electrode assembly, all the members sealed through said envelope being located at the .end portion of said envelope which includes vsaid stem structure, said electrode assembly being .supported substantially solely by said tubular member and ,said yoke.

2. A high frequency electron tube comprising :an electrode assembly, a vacuum envelope including a stem structure yand a hollow `dielectric body enclosing said electrode assembly, said stem structure comprising a pair of coaxial metallic tubular members, one of said tubular members being open tothe interior of said envelope and `sealed to the atmosphere, means joining said tubular members together in vacuum tight relation, a support member connected to the other of said tubular members and to said electrode assembly and forming substantially the sole support for said electrode assembly, va dielectric member sea-led in vacuum tight relation with said other tubular member and sealed to said dielectric body and closing the same, an array of lead-ins sealed through said dielectric member and connected to said electrode assembly, said lead-ins and tubular members forming the sole direct current connection through said envelope to said electrode assembly.

i3.. A high frequency electron tube, comprising an electrode assembly, ya vacuum envelope. including -a stem structure and ahollow dielectric body `open at one lend .and enclosing said yelectrode assembly, Asaid'stem structure `comprising a pair of coaxial metallic tubular meinber-s, Vthe Ainner one of .said members being open :to the interior of said envelope vand sealed to the atmosphere, flexible means joining said tubular members -in vacuum tight relation, said -inner .tubular member being movable with respect to said outer tubular member, the outer one of said tubular members being highly thermally conductive, a dielectric member sealed vacuum tight to said hollow dielectric body and closing the latter, .means joining said dielectric member vacuum tight to fsaid router tubular member, an array of lead-ins sealed through said dielectric member and spaced around said outer tubular member, a massive metallic support member connected to said outer tubular member and to said electrode assembly and 'forming substantially the -sole -support lfor said lelectrode assembly, and -said lead-ins and said tubular members `forming the `sole direct current lconcluctors into -said envelope.

4. An elect-ron tube, `comprising an envelope including at least two coaxial-metallic tubular members Yone within the other, the inner vone of said .tubular members having iends extending beyond the outer tubular member, means connecting inner end portions of said tubular members in vacuum tight manner, the other end of said inner member being sealed vacuum tight, said envelope including'a hollow Ydielectric body :port-ion through which said 'tubular members extend, means joining said dielectric bod-y portion vacuum tight to said outer tubular member intermediate the ends thereof, a cathode, an anode including a cavity resonator adjacent `said cathode, a second cavity resonator `electrically and thermal-ly closely coupled 'to said anode, and means connected --to said second cavity resonator and to said outer tubular member supporting the former from the latter, said means forming a highly conduct-ive thermal -path and closely thermally coupled with saidsecond cavity resonator and said outer Itubular member.

5. An electron tube, comprising an lenvelope including a dielectric portion forming an enclosure, -a cathode and an anode including a Atirstkcavity resonator adjacent said cathode in vsaid enclosure, means `for tuning sai-d -first cavity resonator Iinclud-ing a second cavity resonator closely electrically coupled to -the first cavity resonator and Vclosely 'thermally coupled 'to said anode, coaxial concentric tubular members forming a reentrant portion of said envelope, the inner of said tubular members being open to the interior of said envelope vand sealed to the atmosphere, means joining said tubular members in air tight relation, and a highly thermally conductive support member connected to said secon-d cavity resonator and to one of said tubular members, said one tubular member being highly thermally conductive and having a portion extending outwardly of said envelope.

6. An electron tube,vcompr.ising an envelope including a dielectric portion forming anenclosure, a cathode and an 4anode block including a first cavity resonator adjacent said cathode in -said enclosure, means for tuning said first lcavity resonator and `cooling said anode block including a second cavity resonator connected to said anode block in Agoed 'heat exchange relationship therewith 'and closelyfelectrically coupled to Asaid first cavity resonator, said last mentioned means further including coaxial concentric `tubular members forming a portion of said 'fenvelope and a highly thermally conductive member connected to one of the tubular members and to said second cavity resonator in good heat exchange relationship therewith, the inner .one of said tubular members being open to the interior 'of said envelope and closed ito the atmosphere, said one'tubular member also being highlythermally conductive and having Ya portion extending outwardly of said envelope, and means joining said tubular members in air tight relation. n

v7. An electron tube, comprising an envelope including a dielectric portionforming an enclosure, a Vcathode and an anode-block in ysaid enclosure, saidanodetblock in .cluding a first cavity resonator adjacent said cathode,

means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and coaxial concentric tubular members, said second cavity resonator being connected to said anode block in good heat exchange relationship therewith and closely electrically coupled with said first cavity resonator, the inner one of said tubular members extending axially through another one of said tubular members and having one end portion `thereof open to the inside of said enclosure, means sealing the other end of said inner tubular member to the atmosphere, fiexible means connected to said inner tubular member and said other tubular member and joining them in air tight relation with the inner tubular member movable with respect to the other tubular member, a tuning plunger connected to said inner tubular member and movable therewith and extending into said second cavity resonator for tuning the same, and a highly thermally conductive member rigidly connecting said other tubular member to said second cavity resonator and supporting the latter in good heat exchange relationship with said other tubular member, said other tubular member being highly thermally conductive and having a portion extending outwardly of said envelope.

8. An electron tube, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and at least one highly thermally conductive tubular member, said second cavity resonator being connected to said anode block in good heat exchange relationship and closely electrically coupled to said first cavity resonator, means connecting said second cavity resonator to said tubular member in good heat exchange relationship within said envelope and supporting said second cavity resonator, said tubular member having a portion extending outwardly of said envelope, and means including an exhaust tubulation sealing said tubular member.

9. An electron tube, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an 'anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and at least one highly thermally conductive tubular member, said second cavity resonator being connected to said anode block in good heat exchange relationship and closely electrically coupled to said first cavity resonator, means connecting said second cavity resonator to said tubular member in good heat exchange relationship within said envelope and supporting said second cavity resonator, said tubular member having a portion extending outwardly of said envelope, means including an exhaust tubulation sealing said tubular member, and a plurality of lead-ins for supplying an input to said anode and cathode and connected thereto and extending through the wall of said envelope adjacent said tubular member.

10. An electron tube, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and at least one highly thermally conductive tubular member, said second cavity resonator being connected to said anode block in good heat exchange relationship and closely electrically coupled to said first cavity resonator, means connecting said second cavity resonator to `said tubular member in good heat exchange relationship within said envelope and sup-porting said second cavity resonator, said tubular member having a portion extending outwardly of said envelope, means including an exhaust tabulation sealing said tubular member, means for modu- 8 lating said second cavity including an electron gun, said electron gun including a plurality of electrodes mounted on said second cavity resonator, and a plurality of leadins for supplying an input to said anode and cathode and electrodes, said lead-ins all extending through the wall of said envelope adjacent said tubular member.

1l. An electron device, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and coaxial concentric tubular members, said second cavity resonator being connected to said anode block in good heat exchange relationship therewith and ciosely electrically coupled with said first cavity resonator, the inner one of said tubular members extending axially through another one of said tubular members and having one end portion thereof open to the inside of said enclosure, means sealing the other end of said inner tubular member to the atmosphere, liexible means connected to said inner tubular member and said other tubular member and joining them in air tight relation with the inner tubular member movable with respect to the other tubular member, a tuning plunger connected to said inner tubular member and movable therewith and extending into said second cavity resonator, and a highly thermally conductive member rigidly connecting said other tubular member to said second cavity resonator and supporting the latter in good heat exchange relationship with said other tubular member, said other tubular member being highly thermally conductive and having a portion extending outwardly of said envelope.

12. An electron tube, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and coaxial concentric tubular members, said second cavity resonator being connected to said anode block in good heat exchange relationship therewith and olosely electrically coupled with said rst cavity resonator, the inner one of said tubular members extending axially through another one of said tubular members and having one end portion thereof open to the inside of said enclosure, means sealing the other end of said inner tubular member to the atmosphere, liexible means connected to said inner tubular member and said other tubular member and joining them in air tight relation with the inner tubular member movable with respect to the other tubular member, a tuning plunger connected to said inner tubular member and movable therewith and extending into said second cavity resonator for tuning the same, a highly thermally conductive member rigidly connecting said other tubular member to said second cavity resonator and supporting the latter in good heat exchange relationship with said other tubular member, said other tubular member being highly thermally conductive and having a portion extending outwardly of said envelope, means for modulating said second cavity resonator including an electron gun, said electron gun including a plurality of electrodes mounted on said second cavity resonator, and a plurality of lead-ins connected to said anode, cathode and electrodes for supplying an input thereto, said lead-ins being sealed through said envelope wall adjacent said other tubular member.

13. An electron tube, comprising an envelope including a dielectric portion forming an enclosure, a cathode and an anode block in said enclosure, said anode block including a first cavity resonator adjacent said cathode, means for tuning said first cavity resonator and cooling said anode block including a second cavity resonator and at least one highly thermally conductive tubular member, said second cavity resonator being conected to said anode block in good heat exchange relationship and closely electrically coupled to said rst cavity resonator, a masincluding an exhaust tubulation sealing said tubular memsive highly thermally conductive yoke supporting said secber.

ond cavity resonator and connected thereto in good heat exchange relationship, said yoke having an aperture Refelenfes Cited in the me 0f this Patent formed therethrough, said tubular member extending 5 UNITED STATES PATENTS through said aperture and connected to said yoke in good heat exchange relationship, said tubular member Iilcln gli? having a portion extending outwardly of sald envelope, 616,038 Hansen Oct' 28, 1952 said envelope including a portion of relatively low thermal conductivity joined to said tubular member, and means l0

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