US2512859A

US2512859A - Electron discharge power amplifier

Info

Publication number: US2512859A
Application number: US35756A
Authority: US
Inventors: Philip T Smith
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1948-06-29
Filing date: 1948-06-29
Publication date: 1950-06-27
Anticipated expiration: 1967-06-27

Description

June 27, 1950 P. T. SMITH ELECTRON DISCHARGE POWER AMPLIFIER 7 Sheets-Sheet l Filed June 29, 1948 l .INVENTOR BY www gaag ATTORNEY June 27, 1950 P, T SMH-H 2,512,859

ELECTRON DISCHARGE POWER AMPLIFIER Filed June 29, 1948 '7 Sheets-Sheet 2 I 'HH ll EIL- w. e /57 I l VENT 2211'12517 faz/L ATTORNEY June 27, 1950 P. T. sMn-H ELECTRON DISCHARGE POWER AMPLIFIER 7 Sheets-Shea?I 3 Filed June 29, 1948 www e. gaa@ June 27, 1950 P. T. SMITH ELECTRON DISCHARGE POWER AMPLIFIER '7 Sheets-Sheet 4 Filed June 29, 1948 1 w' Y- 4.2M

June 27, V1950 P. T. SMITH 2,512,859

ELECTRON DISCHARGE POWER AMPLIFIER Filed. June 29, 1948 '7 Shee'ts-Sheet 5 INVENTOR I l lATTO EY June 27, 1950 P. T. SMITH ELECTRON DISCHARGE POWER AMPLIFIER '7 Sheets-Sheet 6 ill (fi,

Filed June 29, 1948 ma@ aw June 27, 1950 P. T. SMITH ELEcTRoN DISCHARGE POWER AMPLIFIER '7 Sheets-Sheet 7 Filed June 29 1948 aplasta An additional object of my invention is to provide a push-pull device which Ais suitable for amplifying high power of high frequency being especially useful in balanced push-pull ampliers or modulators where freedom from self-oscillation is essential.

The electron discharge device of my invention is to be used as a modulated amplifier and a further object of my invention is to provide such a device for grid modulation wherein very high cathode emission densities are obtained and high percentage grid modulation may be carried out without causing noticeable amounts of grid current to flow on-the positive cycle of the modulation currents. This improves the operating characteristics and reduces the electrode cooling problem.

Manufacture of an electron discharge device .with compact closely related electrode structure is diflicultand an additional object of my invention is to provide a device having precision parts which can beaccurately constructed andeasily assembled and lined up and in which alignment and spacing are rigidly maintained during operation thus minimizing change of electrical characteristics.

In describing my invention in detail, reference will be made to the attached drawings wherein .Figure l illustrates symbolically the tube elements and connections of an electron discharge device arranged in accordance with my invention and included in a basic repeater circuit; Figures 2, 2a and 3 illustrate symbolically the electron emitting electrodes, electron control electrodes, screen grid electrode and anode and also illustrate the beam forming electrodesv and the 5 manner in which they concentrate the emitted electrons and guide them toward the anode and .prevent them from reaching the control grid or screen grid in material amounts to be absorbed. z thereby; Figure 4 is a view transverse to the 5 longitudinal axis of my electron discharge device partly in section to expose the general electrode structure and details of the anode electrodes and `mounting and electrode cooling systems; Figure `5 is a view similar to that of Figure 4 but taken 55 about at right angles thereto; Figure 6 is a plan .view of the end of my electron discharge device showing the main header and the uid cooling conductors and .electrical conductors passingtherethrough; Figure 7 is a sectional View trans- 50 verse to the electron discharge device axis of vFigure 5; Figure. 8 isa perspective view of the cathode elements, beam focusing elements and control grid elements and supportsfor the same;

Figure 8a illustrates details of the cathode sup- 65 port as Viewed from the opposite side; Figure 9 is an enlarged elevation taken along the lines .9 9 of Figure 7. It shows details of the cathode mounting blocks, cooling circuits and electrical circuits therefore andthe control grids and their mounts and cooling fluid and electrical circuits; Figure l0 is an exploded perspective view of the screen grids and the manner of mounting the same. This figure also shows details of a heat shield for the cathode and supporting means for 'the control grid; Figure 11 is a perspective View showing the manner of mounting the neutralizing capacitors built into my improved electron discharge device structure for cross coupling the anodes and control grids; Figure 12 is an enlarged view of the relationship of the electrodes of my device. This view is taken along the lines |'2-l2 of Figure 7; Figure 13 is asection taken along the line l3-I3 of Figure 5. This gure shows details of the cathode support structure; and Figure 14 shows in detail a support member between the cathode support structure and the control grid support to prevent movement of the control grid transverse to the longitudinal axis of 15 my novel device.

Briefly, an electron discharge device made in accordance with my invention includes an evacuated envelope containing an electrode assembly comprising a two section cathode, two first or control grids, two second or screen grids, two anodes, beam focussing elements arranged adjacent the cathode elements of each cathode section with screen grid to screen grid, screen grid to cathode, and cathode section to cathode section coupling capacitors and neutralizing elements all combined and disposed within said envelope to form an internally neutralized device of the screen grid type with low impedance between the cathode sections and between the screen grids.

In Figure 1, I have shown by simplified basic wiring diagram using electrode and circuit element symbols, my novel tube in a push-pull repeater or amplifying circuit with an input transformer T and an output transformer T. Reference will be made to this figure in the description which follows to explain the novel features of my invention. In Figure 1, the reference numerals or characters applied to the electrodes correspond to those used in the detailed description which follows in so far as possible. In this figure, it will be noted that coupling capacitors Csg are shown between both screen grids and the cathode structure. Coupling capacitors CK are also supplied between the cathode sections and neutralizing capacitors NC are supplied between the plates and control grids. The capacitors CK and Csg in series are between the two screen grids. All capacitors are built into the tube structure. Furthermore, the screen grids are directly connected together by lead 1 so that they are at the same In order to provide an electron beam having high current densities and to permit the close spacing of the control and screen grids which is necessary for eiiicient high power operation, the electric eld and 4electron configuration becomes important. In the practice of my invention, the electron field configuration .at and near the cathode is as illustrated in Figures 2 and 2a of the drawings. The electric eld'is such as to form the electrons, leaving thev cathode, into concentrated beams which are directed toward the anode. The electric field configuration is obtained by use of beam forming elements adjacent the cathodes operating at the cathode potential or if desired a potential negative with re- 30 are thefocussing elements. In the tube structure there are a large number of cathode elements 2i) in groups there being three ormoreigroupsia's desired. "Thecathodelelements.ofFigure 2;haye at emitting surfaces, those .of FigurelZacare curved `slightly vas shown. The .dash 'lines .indie catev the electron :pa-tbs. The electricleldqnearthe electron emitting surface is .such .that .the electrons :leaving .this surface `are .subject .to .a force which Ihas acomponent directed .towarda plane through the center oftheemittingsurface and perpendicular toit, this force .component being .greatest in the region .of .the edges of the electronemittingelement. I prefer .to utilize *.an arrangement .as shown :in Figure `3. .In .thisarrangement, shownschematically, the .cathode ele-l ments 2l) comprise .at emitting .surfaces inter. posed :between .the focussing elements.. 3B .of `similar shape .parallel withandspaced. from .thecathodes. i'lhesurfaceslof. the focussing elementsextend vbeyond thesurfaces of .the emitting cathodes. 'Bhe first grids or :control electrodes .'22 .are in line withA the focussing elements as .are .the screen grid electrodes 25. The anode structure., not shown in this figureis `disposed beyond the screen .grids .and the Aelectrons from theemitting surface follow .parallel paths .between .the control and screenelectrodesto reach the anodes. .Similar 'but .opposed electrode and .beam guiding elements are alsoused `in/rny push-.fpull .electrondischarge device. vAn .embodiment Lof my .device .is .illustrated in the `remaining guresof thedrawings. .Thiedevice comprises an .electron discharge vdevice clo sure .member .includingas shownin Figures 4, 5 and 6., headers :lll and .lll separated.lyacylin-A drical `portion l2 as will be .developed later. The envelope .enclosesadouble cathode K, as shown in Figures '1, .8 and `8a., emitting electrons in opposite directions, electron beam focussingelements 3c associated with the cathodes,.control grid elements 22 and 2:2 facing the cathodes and v.beam focussing elements, screen .grid elements 2.5 and facing the control v.grid elements and anodes 26andf2' facing the screen grid elements.

The cathode K comprises three sections as shown in. Figures 1, .8. 8a and 9 each of which sections .areas shown in detail in Figures 8 and 8a with U-shaped cathode elements 2c ,spaced as. shown. The control grid .structure Cg and Cg, Figures 7, .8 .and 9 comprises control grid elements 22and22' mounted close to the respective cathode sections. The novel screen grid structure Sg and Sg, vFigures 7 and 10, .comprising elements v25 and `25 are mounted close to the control grids. The anodes 2K5 yand '25', Figures 4 and '7, are mounted facing the screen grid structures. Beam yfocussing elements 3c and 33' are carried by the cathodesupport being mounted` between the cathode elements 2i) which are U- shaped. The relationship of the elements is shown in Figure 12 which is an enlarged View on the vlines |2-i2of Figure '7. The ends of all of the U-.shaped cathodes are .spot Welded to a strip 32 cna main support 35, Figures 7, 8, 8a and 9. The ends 4of the remaining legs orgroups (here 3 groups) of the U -shaped cathodes are spot welded to three strips 3.3, 33' and 33"., Figure 8a, on

secondary cathode blocks

34, 34 and 323. Note that in the sake of clearness, Views of opposite sides of the-cathode supports are shown in Figures 8 and 8a. The main support 35 is bolted to a lug Lon the header I0 as shown in Figures 4 and 5. The electron focussing elements 3i) and 33 and screen :grid structure are .also carried by this-main support. This `main support'is also used to prevent transverse movement ofthe grid electro delstructure as -descrbedhereinatern The control' gridsareseparate and :theiristructuresare each-.supported by its cooling :fluid :pipes .CP and CP as shown in Figures 5, 6 and '7. rllhese pipes are sealed into glass inserts in :the header Ml. Thus all of 4the lelectrodes, except .the-.anodea are. supported .by thermain header .L0 andall-.o-f. the electrodes supported bythe main iheader .ml are provided'. with .cooling fluid i conductorswhich are sealed .intheheader .t0 and, '.withthe exceptioneof one.coolingconductorior thecathodestructures, are :insulated-theretrom so .that :the cooling .fluid conductors also serve ,as electrical connectors.

y The-anode .electrodes 26 .and .25' .are .mounted on .their-.cocling.fluid l-pipes Whicharefsealed into the header vleas shownin Figures Sand-6. `'The headerl l .is adjustable .as is .the header .110-50 that 'theancde .electrodes .may .be moved .relative to the .other electrodes. to establish mechanical andelectrical symmetry between -theanodesand screen grids.' v

The cathodefstructnrepand .beamiocussingielements, -control :grids Aand .screen .grids .andthe supports. or .the .saone willnow gbedescrbed. in detail. The .cathode is lin :three sections .and the. sections .being zsimilar, Aone .only .will be described fully. Anexplcded .View oftheicathode andbeam focussing- .elements and .support A.and .control vgrid arelshown vin Figure .8. .'Ihese. .elements .are mounted withinothe screen jgrid .elementsshown in :detail .in .Figure .10..

The .cathode comprises, .as illustrated in .Eig-

ures 1.8, 8a and :9, Aapluralityof aU fshaped wire .or strap-.like relements .2D lwhichmaybe of tantalum or .thesame coatedwith thoria `.ora .matrix of tungsten-thoria. -Onefleg-.o each Aof theelements port members 311, .3.4 :and .34 and .the Astrip .32, lis

bolted. to, the vliquid .cooled main .support .member-.35. The threemembers 3.4.3.4' .an.d.-3.4f. :are shown dotted in Figures aand, 5 ,and in .detail in Figures 7, 8 and 8a. The main Isupport mem-` ber. 3,55 andsupport members 35, 3.4. and .34.` are separated and insulated from .each `other` .by .a strip of mica. Thus members 34, .34' and 3.47 are insulated Vfrom each, other andmember 35` exceptgfer theconnectionsormed therebetween by the U-Sheped cathodes.` .The `capacitors formed between .members 34., 34C. 34" and Slllermit the. cathode I.sections to operate at the same A. C. potentialfsince the impedance between -the cathode sections has been reduced substantially to zero. The ,impedance between the individual cathode elements and between the sameand the focussing elements and between focussing elements isextremely low `because of` thenovel mounting used. The double structurer operates as onestructure with respect to alternating currents `of .high `frequency. The vadvantage of .such an ,arrangement in amplifiers is apparent.

The members .34, 3d .and 3.4 and-.3.5 are bolted together by bolts 36. This structure is vshown'in detail in `section in Figure 13 taken on the lines I3.-l'3 of Figure 9. In the embodiment described there are three cathode assemblies each compris-v ing a group of .cathode elements support'as described. There may :be more groups oriewer groups of cathode elements depending .on the number of phases of filament current to `be used. Straps '33, 33 .and '33 are boltedto secondary

cathode support members

34,34 and 34.. There isa memberi34f34 and.34;fcrreach cathode secsA tion and these

members

34, 34' and 34" are as described above bolted to the member 35 which is the main cathode and beam concentrating element support.

The

members

32 and 33, 33 and 33" also carry integral therewith or spot welded thereto the beam forming and focussing

electrodes

30 and 30 of Vappropriate metal such as tantalum. These electrodes are run at the cathode potential and neither emit nor collect electrons. The focussing electrodes 30 and 30' are integral with the cathode blocks and are therefore cooled by the cathode support cooling fluid. They merely serve to direct the electrons and guide them toward the anode and away from the grid and screen grid as shown in Figures 2 and 3.

The main cathode support 35 extends beyond the

members

34, 34 and 34 as is shown clearly in Figures 4 and 5 and is fastened by bolts 38 to the main header support I0. The main support flange-like header IU also seals the end of the electron discharge device. The envelope includes the metallic cylindrical member l2 with a flange 44 on the outer periphery thereof which is drilled and threaded for bolts 46 which cooperate with the ring 48 shouldered at 4l to bolt the main header lll and member I2 together. To make a vacuumtight joint, a copper ring 50 is put between the bearing surfaces of the main heater I and cylindrical member I2. A cylindrical member 49 is used as a spacer between the outer peripheries of ring member 44 and member 48. The other end of the electron discharge device is closed in a somewhat similar manner. A ring 44 is welded or otherwise fastened to the outer periphery of member |2 and the ring member 44 is threaded to receive bolts 46' passed through a ring member 48 shouldered at 4l' to engage the other main header I0'. To make a vacuumtight joint a copper ring 50 is inserted between the members I0' and |2. It will be noted that a very rugged tube structure has been provided and further that, as will be developed as the description progresses, the tube structure is easily built up and assembled.

Returning now to the cathode structure, it will be seen by reference to Figures 8a, 9 and 13 the cathode is in three sections and three phases of heating current are supplied thereto. The three cathode support blocks 34, 34' and 34" each have nuid channels FC therein through which the cooling fluid may be circulated. The channels partly shown in said figure may be formed by drilling or otherwise and are connected by uid

conductors

60, 60 and 60" (Figures 5 and 6), each including inlet and outlet pipes, to a source of cooling fluid not shown. The iiuid conductors pass through three

seals

62, 62 and 62", Figures 4, 5 and 6, in the main base plate l0. In order to expose the member 35, lug L andbolts 38 and the metallic shield between the control grid and anode leads, described hereinafter, the

fluid conductors

60, 60' and 60" are shown in part only in Figure 4. The fluid conductors 6U, 60' and 60 also serve as electrical conductors of heating currents for the cathode member 2|) and are insulated each from the other and from the member 35. The three

seals

62, 62' and 62" are similar and details of seal 62 are shown in Figure 4. A steel cup 64 is welded into a circular opening in the header l0 and a Kovar cylinder 66 is welded to the cup 64 and/or header lll. A glass bead 68 is bonded to the Kovar member 66 and a Kovar end pipe l0 is bonded to the glass bead 68. The fluid conductors 60" are then passed through a metal plug 1| (Figure 6) which is welded into the end member 10. The mica sheet 31 insulates the filament support blocks 34, 34 and 34" from the single filament support blocks 35. The bolts 36 pass through ceramic or glass rings 36', Figures 9 and 13, and washers 36" of ceramic or the like material to prevent conductive coupling between

members

34, 34', 34" and 35 by way of bolts 36.

The main cathode support member S5 is also cooled by :duid in conductors 'l2 one of which is the fluid inlet, the other the fluid outlet. These fluid conductors shown in Figures 5, 6, '1, 9 and l0 are sealed in and conductively connected at 14, Figure 5, to the main base plate l) and serve as the common cathode ground connection. In the embodiment illustrated, three phase heating currents are used and phases No. 1, No. 2 and No. 3 may be supplied from a source not shown, to leads 60, 60 and 60", respectively. The use of three phase heating current reduces power supply hum.

It will be noted that the main support 35 is conductively connected to the main shell |2 of the tube, etc. and is at ground R. F. and D. C. heating current potential as illustrated in Figure l. The

members

34, 34 and 34 and 33, 33 and 33 and the ends of the cathode members 20 welded thereto are coupled to the member 35 and ground by the very large parallel by-pass capacitors formed between

members

34, 34' and 34", respectively, and the main support member 35. The capacitors found by these elements are shown by dotted lines in Figure l. Thus the entire cathode structure is at ground radio frequency potential. This reduction of impedance between the cathode sections adds materially to the stability of operation of the tube structure in high frequency push-pull amplifying circuits.

The structure described above and hereinafter provides electronic circuit and mechanical advantages that are of particular significance when these structures are incorporated in amplifier tubes. I have provided liquid cooling of the mounting, supporting and lead in structures thereby reducing the thermal expansion enough to maintain the electrode alignment in normal operation substantially as established during assembly. The accurate alignment that can be obtained during assembly and retained during normal operation along with mechanical symmetry makes possible a grid to cathode and grid to screen grid capacitance balance between the two tetrode sections.

The

control grid elements

22 and 22 are fastened to or made integral With their respective supports 2| and 2|' as shown in Figure 8. These grids are rod-like elements of like length which t tig-htly into holes of like depths drilled into the edges of supports 2| and 2|. It is to be remembered that with respect to electron emission from the cathode, the

control electrode elements

22 and 22 are in line with the beam forming and guiding

elements

30 and 36 to outline passageways for the electrons to pass from the cathode elements in concentrated sheets to the anodes. The grid members may be molybdenum and may be silver soldered or otherwise fastened to the edge of the supports 2| and 2|'. The control grid base members 2| and 2 are supported by the concentric cooling fluid conductors CP and CP to which they are fastened by soldering or otherwise as shown in Figures 7, 8 and 9. The fluid conductors CP and CP' in addition to acting as the inlet and outlet for the cooling fluid also serve as electrical connections to the controlfgrid electrodesI and .supports fory thesegrids electrodes. The grid support and cooling iiuid conductors Cl? and CP are sealed'into the header Il) `as Shown in fFigures and 6. This seal is quite like the seal 624- described above and willbe described briey. A cylindrical-.like Kovar mem-ber i8 is welded to or otherwisefastened by. a vacuurntight joint to the header I0. A glass member 8.0 is sealed to cylinder 18 anda K ovar member 8,2 is bonded to.- the glass member 80,. The pipes CP and CP pass through a vacuumtight plug like member in the end of member 89,. Itmay be noted here that the grid electrodes are supported rigidly byv the members CP, C?" andmaintained in fixed closely spaced relation. to. the cathodes. In operation there may be. some longitudinal movement ofthe gridsand such is permitted.v However, there is to be no ltransverse twisting or swaying of the gridsl andadditional means to fix the grids in this respect. will bedescribed later.

The, grid structure disclosed provides a sturdy mechanical support with Iaccurate alignment and spacingv of theeleinents is maintained duringthe nOrmaLoDeratiQn of the device in which the grid is, mounted, This., isobtained by the effective cooling oi the grid supporting pipes I provide andv cooling ofthe. attached glassseals which eliminates. misalignment. of. the electrodes bv thermal expansion dueto energy absorbed at the control elements or power dissipated in the lead in, and support. pipes. The. effective cooling of the. sunnortingpipes.provides a means of cooling the grid elements and thus prevents excessive electron emission from thesel elements. The element. length is. chosen relative to the. element cross section so as to permit practically allof the. power dissipated in the elements to be conducted to a coolant circulated in the supporting pipe.`

The duplex screen electrodes. and z5' are mounted with good` thermal and electricalV contacts in rigid frame. members. shown. in. detail. in Figures. 'l and 1.0.r These frame membersv comprise rigid.

strong side pieces

21,21 and 2 9. and 29' fastenedtogetherlou end piec.es.85.,.85' (at header mend). and 3.7. and 31' at the. other end. The two framelike members.. are held in parallel relation by. strong end memberseaand 89', which run the iull4 length. of. the screengrids and hold. the screen grid structures.y in, parallel planes and. prevent relative movement. thereof in any, direction-` The side. nieces4 21.', 2J and 1.9, ze: are shown. in Figules '7, leand- 113.. The support 2 1, 21 and 29, 2.8. with end. pieces. 8.3,. 89 is made as strong as reasonably possible to keep the electrode spacing xed. The. screen grid supports 2l and 2l', are bolted. to the. main support member Baby bolts all.. (Fgurel) passing, through ceramic o r the like sleeves... 9c which insulates the. bolts from the members 314', 34", 34" and 35.'. The members 2.7" and are. insulated from the members 34, 3d', 34" anden. by mica. sheets. St. and S5...

The screen. grid supports 2l and 2l' and 29 and 28' have fastened thereto cooling fluid conductors, 9G and` ill which extract heat fromthe screen grid supports. These fluid conductors take nart, iny supporting the screengrid structure and this support taken. with the framemembersand supports described above include the screen grids in str-ong closed rectangular frame. members with transverse spacer pieces S9 and 89, running the `full. length of the framemembers to keepr the exact spacing between the screen grid electrodes. The grid-like rods 25.- and 25.' are two. sections and are silver soldered in holes inthe inner edges 10 ofsupoorts 2.1, 2.1.! and. 29-and.. 2.9!. The. screen grid rods 2.5 and25.' extend from the said inner edges of the sides. ofthe. frame toward each. other but do notmeet. This. structure. is used to intere rupt circuits at which undesired oscillations V ture.y The canacitors thus formed are snpwnaby.

dotted lines in Rigore. 1.-. 'Ilius the screen.. grids operate. at substantially ground.. 1.1;. without usine. external br-nass. capacitors. and the. stability ofv the device in high. frequency circuits is. en.- hanced.

The. screen. eridsare. cooled by lluid circulated in conductors. 9,5 andSl' which assliown uros 5. and. 6., .iced into common conductors .8.8 and SBI as shown .inlieures 5 and 6.. These conductors 9.8- and 98' are sealed into a plus a metal. ring 9.9. such as Kovar which in. turnissealed. intoa elassmember lutin turnsealed into amstel, such as. Kovanring. |112. welded or otherwise iastened into the mainiheader l0.' seal. issiinilar to the. seal 6.2" described above.` These fluid con.- ductorsalso serve asconductors for theel-G. and Di-C.. connections... between the. circuits. and.v the screen grid electrodes,4 and. are.. in .lated from the main header lbvthe alassio rt., Thus the screen grid, control grid and cat-.. dc and beam forming electro-des.. are. all rigidly with. respect to each other and even.. though. the dis: tancesbetween these. electrodes are. small, short circuits therebetween .cannot take piace..

Becauseof. the novel. construction of the. screen grids and the arrangement and cooling.v thereof, It have iorovidedcircuit,y thermal and mechanical advantages not. known licretof..oreV Several; cire cuit advantages. accruefrorntlie comnactness and low. impedanceconnections between elements. and electrodes.v Such. low impedance paths arey nrovided between the screen. grid. elementsbetween thetwo screen grid. sections of. a double screen grid tube. and betweentlic. screen grid. structure and cathode. Oi equal` importance in ultra-high frequency ampliers is the very short length of neutralizer element (described hereinafter). that is ncrmittcdwhen. mv structure is usedl of these ieatures combine to provide. excellent elecmeal, stability in. anultraehieh ireouencv duplex grid amnliiier- '.Ine. screen gridstructure Provides. rrccisionA mounting. and aliennlentoi the elements which. is. unalected bv the. processing temperatures andlby normal ooeratinaconditlons.

The anode-electrodes .26 and. 2.6! are-similar and aremountecl opposite. sides of. the. cathode ele..- ments 20, with collector surfacesn, Eieuresfi and @..very'closeto the screen. gridelectrodes. These electrodesshown inFigures 1,l 5, 'l and ll.- are` made up of. twoblocks, 104. and lllaof metal..` Tlccbloclss of Inetal are silver soldered to form, vacuurntight joints. The blocks |04 and IQE have slots or Channels or grooves in the face of one or both thereof. toform 'fluidpassagewavs through which the cooling uid is forced. These passageways are carty of the device envelope and the joints thereof are` to. be. va.c uumtiglrlt,y One end of the anode. proper terminates in a hollow metallic block. L05 (Eieures'l. 5.,A 7 and 11.)A into which a fluid conductor |01 is coupled- This. block sup.

plies cooling fluid to the slots in the anode blocks |04 and |06. This fluid conductor and its continuation has several functions. In addition to being a fluid conductor, this conductor with continuations acts as a member of a tuning line connecting the anodes in a resonant circuit having low inductive reactance. The line |01 may be sealed into a glass insert |08 forming part of the wall of the electron discharge device. To facilitate bonding between the glass and line |01 the line may be of Kovar at |01" where it passes through the glass |08. The glass |08 is in turn sealed into a thimblelike member |09 of Kovar which is sealed into the header I' by welding or the like. The member |09 is recessed so that cooling fluid may be fed therethrough by pipes |09. The pipes 01 as constructed and sealed into the header I0 provide good strong supports for the anode electrodes. The members |01 also provide the electrical circuits for the anodes. The other end of the anode proper terminates in a hollow metallic block The hollow block has an opening therein into which an outlet pipe member 3 is coupled. This pipe is insulated from the electron collector block |04|06 throughout most of its length. The outlet pipe ||3 passes through the block |05, into which it is sealed byV a fluidtight joint, and extends within a metallic thermal insulating pipe ||5 (Figure 5). The insulating pipe I |5 extends within the outer conductor 01 and extensions thereof. The channel between the pipes ||3 and ||5 is closed at I1, i. e., about where this pipe enters the hollow block |05 and is terminated. Thus if cooling fluid enters between the pipes ||5 and 3 there can be no flow therein since the path is closed at one end. The cooling uid may be supplied as indicated by the arrows to the pipe 01 and taken from the pipe ||3. The thermal insulating pipe ||5 traps a liquid layer which acts to insulate the cooling fluid within the pipe ||3 from that within the tube |01 and exterior to tube 5. This thermal insulation is obt-ained since the liquid trapped between pipes ||3 and I5 has zero velocity with respect to the retaining pipe surfaces and there results a large temperature drop in the liquid-metal interfaces. The fluid inlet pipe |01 is continued through the wall of the tube forming part of a transmission line or anode tuning circuit. Member |01 forms one member 0f a parallel line and member |01 forms the other member of this line.

My anode as cooled permits anl electron bombardment power input per unit area of bombarded surface in excess of 800 Watts per square centimeter with a reasonable water flow and pressures not in excess of '70 pounds per square inch. By insulating nearly all of the return tube |3 from the anode block heat exchange between input and output coolant in the anode block is eliminated. Thevdoubled walled pipe arrangement wherein the coolant is trapped insulates the input coolant from the output coolant. The liquid cooled anode header glass |08 to metal seals permits use of separate anode header seals which are, per se, cooled. and are useful at high power levels and at high frequencies.

The electron discharge device electrodes as described supply considerable concentrated power in the form of electron beams originating at the U-shaped cathodes. The beams pass in concentrated sheets toward the anodes and considerable heat is generated. A shield |20, Figures 9 and 10, is interposed between the central portion of the U-shaped cathode elements 20 and the Control grid and screen grid supporting structures to prevent emission from the central portions of the cathode elements from reaching these supporting structures. Support members |22 and |22' are soldered to the main support 35 above and below, respectively, the

members

34 and 34". The member |22 (Figure 10) is reduced in size at |23 to form a shoulder that engages with the member 35 (Figure 9) to which it is soldered or other Wise fastened. A pin at |24 in the member |22 serves to locate the member properly during assembly of the electron discharge device. The member |22 (Figure 9) also has drilled therein a locating pin hole |24' and is fastened to the other end of the main cathode support member 35. The members |22 and |22' extend beyond the U-shaped cathode elements and are drilled at |25 and |25 as shown in Figures 9 and 10. The member |20 has end portions |20' and |20" bent at right angles to the V-shaped main portion and these end portions are drilled to receive bolts which are threaded into the holes |25 and |25' in supports |20 and |22 to fasten the shield |20 rigidly between the cathode elements 20 and the control grid and Screen grid supports including fluid conductors CP, CP', etc.

Since an object of my invention is to increase the power output of the electron discharge device, close electrode spacing is to be used. Thus the control grid and cathode are close together and precautions must be taken to prevent movement of these electrodes toward or from each other. The cathode and its support is so rugged that the chance of it moving out of alignment in operation is very slight. The same is true of the control grid support. However, the control grid support is not as rigid as the cathode support and pressure change in the fluid flowing in pipes CP, CP' might cause the grid structure :to sway. The control grid electrode is therefore further stabilized with respect to later movement but is permitted to move slightly in a direction normal to the surface of the base plate I0. This bracing of the grid electrode against lateral movement is accomplished as follows. A mica member |30, Figures 9, 11 and 14 is bolted at one end to the member |22. The bolts used to fasten the heat shield member |20 may serve to fasten the mica element |30 to member |22. The free end of the mica member |30 is split and one finger thereof is bolted to a support member |35 and the remaining finger is bolted in like manner to the support member |35'. Spacers |31 and |31 are placed between the mica member |30 and the members |35 and |35'. The ends of the control grid cooling pipes and supports CP and CP are capped (fluid flow reversed) and the members 35 and |35 are Welded, soldered or otherwise fastened to the ends of these pipes. This mica member as used insulates the control grids from the cathode support, yet prevents any lateral movement of the grids relative to each other or to the other electrodes of the device.

The electron discharge device of my invention includes built in neutralizing capacitors connected between the control grid of one of the device sections and the anode of the other section, and between the control grid of the said other section and the anode of said one section. These neutralizing capacitors are shown best in Figures 9 and 11. The control grid supporting pipes CP and CP' are terminated in caps at the ends remote from the main header |0 wherein the uid is turned around to ow out. Members |35 and 13r |35f'are solderedwelded Vor otherwise fastened tothe end 4caps of grid cooling pipe supports CP and 'CP'. The neutralizing capacitors |60 and |69 are fastened to these supports |35 and |35. The members |35 and |35' extend outwardly in adirection parallel to a'plane passed between the cathode emitting areas. The members |35 and |35' are drilled near the outer endsand the members Hill and |60 are bolted thereto. The membersl and |60 extend in -opposite directions from said aforesaid plane 'and then turn back and up at |G| and IBI' to face a considerable area of the respective anodes 26 and .26'. These elements .form the capacitors NC and NC' of' Figure 1 and are .dimensioned and. adjusted toA compensate and neutralize the capacity within the tube directly between the control grid and anodes. It will be noted that the beam focussing electrodes-have not been included in the circuit of Figure 1. omission thereof simplifies the circuitsand permits better Showing of the remaining elements and built in capacitors.A

` The'electron discharge device of my invention is .further adapted. for stable `operation in high frequency circuits by provision of a novel shield arrangement between the control grids and con-A nectors CP, ACP andthe anode and screen grids and r.t'heirvconnectors.. This shield is shown in Figures .4 and Gand comprises sidemembers |70 and |18 .bolted to the respective screen grid frame members 85 and 85' (Figure 10). The side members extend in a direction parallel to a plane passed between the cathodes to a point beyond the control grid pipes CP. and CP'. An end plate |12 is fastened betweenthe

endsof side plates

85 and 85 to completely block coupling between the control grid and its leads CP and CP and the anode and screen grid and their connectors. The end plate |72 is trapezoidal'to form a trapezoidal frame open at one end.

To facilitate assembly and adjustment of the tubecharacteristics, the header .plates l0 and l0 are made adjustable. their supports, the control grids, their supports, the screen grids, their supports and the uid circuits .and electrical circuits may be assembled and mounted on header plate |ll. The anode electrodes and electrical andfluid circuits therefor may be assembled on the header I0. The tube envelope is then assembled and the holes -in the rings 48 and dd are machined oversize so that the header plates may be moved slightly as de.

sired toproperly relate and space the electrode structures fastened to the two plates.' The bolts 65 and 36' are then tightened tocompress the copper gaskets im and 50' to make a vacuum tight joint between the headers lil and l0' and the side walls'formed by cylinder I2. The ends of cylinder i2, are rounded off and the copper gaskets 50 and 5B' are each compressed between a fiat surface (on plates, 4|) and 40') and the rounded sur-` faces at ,the ends of. cylinder |2. The spacer rings '|39 and 49 prevent warping and deformation of the clamping rings 48 and 48 when pressure is applied. This noveladjustable header method of tube construction and assembly provides a practical method for the construction of evacuated devices requiring closely spaced elements. The double screen grid tube is such a device and the cathodes, grids, and screen grids may be conveniently aligned and spaced with the header plate it removed from the envelope. The anode structure on the header plate Ill may be handled in like manner. The adjustments provided. permit accurate balance in spacing and capacitance Then the cathode sections,`

14 between the anodes and screen grid structures. An electron discharge device assembled in ac-l cordance with my invention is conveniently disassembled for repairs. v Y l* In an embodiment which operated well ata frequency of ina/sec. lthe double cathode` structure has a length of about 6.00", the active parts lof the U-shaped cathodes are about 1" oneach leg. There were 13 U-shaped elements in each of the Vthree groups. The dimensions of each control grid, screen grid and anode are commensurate with the dimensions of the cathode structure. Each control grid is spaced about .050" yfrom its cathode section. Each screen grid` is spaced about .115 from its control grid and each anode is spaced about .167 from its screen grid l' j The planar electron emitting surfaces of thev cathode ystrips function to provide substantially l Where@ is the transit angle, J is the electron beam current density and (S)V is the effective spacing between the cathode and grid, this being the r'egion of interest for transit angle considerations. These fields and configurations permit increased current densities and decreased transit angles making possible high frequency,l high power outputs.` In the embodiment described, 'the tube operated Well at 100 megacycles and an output of 50 kw.

I claim:

1.1A cathode'for providing a plurality of .directed` concentrated `sheet-like beams comprising a plurality of elongated. emitting elements separated by spaces and an elongated non-emitting conducting element in each space, said non-emitting-elements being detached from and extending beyondthe emitting elements in the direction of said beams and a common conductive support connectingsaid emitting and' non-emitting elementsonly adjacent ends thereof. i

2; A cathode for providing a plurality ofoppositely directed elongated electron beams-along spaced paths comprising a beam focussing assembly having on oppositesides thereof parallel non-emitting conducting elements in a plane separated by 'spaces for receiving elongated electron emitting elements and an elongated electron emitting element disposed in each of said spaces said non-emitting elements being detached from said emitting elements, and conductive support means connecting said emitting and non-emitting elements only adjacent ends thereof.4

3. An electron emitting structure including a main support in the form of a metallic strap-'like member, a secondarysupport in the form of a metallic strap-like member insulated-from said rst member to formi'therewith a capacitor and elongated cathode elements fastened at one end to theqmaingsupport andgat theother end ,to thev Secondary supportt19A-cathode structure including a main sup. port in the form of a rectangular `metal bar, a secondary supportin the form of a rectangular metal bar adjacent said` main support and insulated therefrom to form therewith a capacitor, elongated cathode elements fastened at one end the main support and at the other end to the i secondary support, and fluid conducting channels cooperating' with said supports for extracting heat therefrom.

5. A cathode structure comprising a main support in the form of a rectangular metal bar, a plurality of secondarysupports in the form of similar bars of less length adjacent said main bar to'form therewith capacitors, elongated cathode elements each fastened at one end to said main support and at the other end to a secondary support, there being groups of. cathodes for each secondary support, and means for supplying multiphase currents to said cathode elements comprising a common connection to said main support andA separate connections to each vof said secondary supports.

6, A cathode structure comprising a main support in the form cf metallic strap, a secondary support in the form of a metallic strap insulated from said first strap to form therewith a capacitor, U-shaped cathode elements having one leg fastened to the main support and the other leg fastened to the other support, and beam focussing electrodes fastened to the main support and to the secondary support, said focussing electrodes being located between the legs of adjacent U-shaped cathode elements;

'7. An electron beam emitting and beam focussing structure including a main support in the form of an elongated rectangular metal bar, a secondary support in the form of a similar elon-V gated metal bar bolted to said first bar and insulated therefrom, a plurality of spaced cathode elements each having one leg fastened to said secondary support and the other leg fastened to said main support, focussing elements fastened to both supports in the spaces between the leg of said cathode members, and fluid conductors in said supports for extracting heat therefrom.

8. A cathode assembly comprising a pair of elongated oppositely disposed conductors, a plurality of U-shaped emitting elements in spaced registering relationship and having their ends secured to said conductors and elongated conductors positioned in the spaces between said U'- shaped elements and having one end connected to said conductors.

9. An electron discharge device having within an evacuated container cathode elements, electron beam focussing elements separating the cathode elements, a common support for said cathode and beam focussing elements and fluid conductors for said support for extracting hea therefrom.

10. An electron discharge device having within an evacuated container cathode elements, electron beam focussing elements separating the cathode elements, a common support for said cathode and beam focussing elements', an anode electrode, a support therefore, a grid electrode interposed between said anode electrode and cathode elements, a support for said grid electrode and fluid conductors cooperating with each of said supports for extracting heat therefrom.

11. A double cathode structure comprising two support members of considerable surface area facing l eachother thrquh. any insulating medium toformfa Ylarge capacitor, 'electron emitting ele- 412,., A4 double jcfathode structurev comprising two support membersl vof considerable area facing each other through an insulating medium to forma ,large capacitor providing low alternating current iinpedancesbetween these support members, `a plurality of `spaced electron emitting elementslsupported by Ieach ofhsaid support mein;- bers and Ia4 beam focussinglelectrode inv each of heSDaGCS, between, sasiiemitting elements-,

13-efd9ub1e cathode Structure comprising. two suimorhmembers of, ,considerable surface area facineeahther t0. form alarga capacitor, and a plurality ofI lll-shaped` members witheone leg df eah; l.1,'-Shap esi,membr fastened t0. one of. Said Subpart members: and. the other. les preach U- shap'e'd in e'mb'er fastened tothe other of saidA support members. 4 e Y Y 14. A doubley cathode structure comprisingtwo support, memberserf Considerable, area faccine @2191.1r other through, an. insulating medium to formaler@ Capacite. a plurality ,of .l1-Shaped electron emitting electrodes, said U-shaped meibrs having. 'one leafstenedto one 0f said supportsv and the lothenleg fastened to the other of said supports andbeing in spaced relation, and an electron foc'u ing electrode in each of the spaces zbetween said Li-shaped members.

145 An electron discharge device comprising two support members of Y considerabler surface rea ffwiie each other through Yan insulating medium to form a largeicapacitor, spacedelectron emitting elements supportedlby each of said support members toV emit two electron beams. beam guiding elements, in, the spaces between said emitting elementasupported by said supports, a control grid element adjacent each cathode structure, two other supports of considerable surface area facingA said first supports through insulating materialto form therewith large/,capacitors, and screen grid elements mounted on said two other supports.

16. A push-pull electron discharge device of the screen grid type having electrodes including two cathode sections, a support for each therefor, two screen grids, a support for each therefor, and means for maintaining said cathode sections and screen grids at substantially the same alternating current potential forming capacitance between said supports.

17. An electron discharge device electrode structure comprising a metallic support, a plurality of elongated electrode elements fastened at one end to said support, fluid conductors cooperating with said Support to extract heat therefrom, said elongated electrode elements being short enough so that the entire length of the elements is cooled by heat conduction along the element to the 2&0) A grid structure Vcomprising two rigidly spaced side members, and a plurality of elongated metallic elements extending from the side members toward each other-to nearly meet.

21. A grid structure comprising two rigidly spaced parallel metallic side members, and a plurality of rod-like elements extending in spaced relation from each side member toward the other side member to nearly meet.

22. A double grid member comprising a rst support comprising two rigidly spaced side members, a second support comprising two rigidly spaced side members, frame members for rigidly holding said supports yin parallel planes and a plurality of elongated members extending from each side member of each support toward the other side member of each support to nearly meet in the space therebetween.

23. In an electron discharge device, a grid structure comprising a metallic picture framelike member, a plurality of grid elements fastened to opposite inner peripheries of ysaid frame-like members and extending toward each other to nearly meet, an envelope enclosing said grid structure and a support in said envelope for said grid structure. Y

24. In an electron discharge device, a grid structure comprising ametallic frame member, a plurality of grid elements fastened to opposite peripheries of said frame and extending toward each other to nearly meet, a cathode structure, an envelope for said grid and cathode structures, a support in said envelope for the cathode structure and a capacitor built into said support, one plate of said capacitor serving as a support for said grid structure.

25. In an electron discharge device, a double grid structure comprising two metallic frame members in parallel planes, metallic side pieces fastening saidl frames in rigid relation in said parallel planes, a plurality of rod-like elements extending from'opposite inner peripheries of each of the frames toward each other to nearly meet, an envelope enclosing said structure and a support in said envelope for `said* double grid structure.

26. A cooled anode, structure comprising an active surface and a fluid path adjacent thereto comprising an inlet pipe coupled to one end of said path, an outlet pipe coupled to the other end of said path andgpassing within said inlet pipe, and a Iluid trap in the form of a second pipe surrounding said outletpipe within said inlet pipe. s A

27. An anode electrode for an electron discharge device comprising a member having a plurality of parallel passageways extending therethrough, a tubular member connected to and supporting said anode, one end of said parallel passageways communicating with said tubular memf ber and another tubular member within said `first tubular member and communicating with the other end of said passageways.

28. An anode electrode for an electron discharge device comprising a hollow member having passageways extending therethrough, a tubular member connected toand supporting said anode, one end of said passageways communicating with said tubular member, `and, tubular means within Y thereof which are in register to form fluid channels, a hollow member at one end ofsaid bars to completea cooling uid path to one end of saidchannels,`a hollow member at the other end of said bars to complete a ud path to the other ends of said channels, a fluid conductor coupled into said first hollow member and a fluid conductor'coupled into said second hollow member and passing through said first hollow member and within said first-named uid conductor.

30. An anode electrode comprising two rectangularr elongated metallic'bars having a plurality of longitudinal channels in one face of at least 'one thereof, said bars being joined together atsaid facesto form fluid channels which are vacuum-tight, a hollow member at one end of said bars to complete a cooling huid path to said channels, a first iiuid conductor coupled into said hollow member to complete a iluid path between the same and an external fluid source, a second hollow cap member at the other end of said bars to complete a fluid path to the other end of said channels, 'a second fluid conductor coupled into said last-named hollow member and passing through said first-named hollow member and within said first fluidvconductor to form a second nuid path to 'said external source and a dead end conductor enclosing said second conductor within' said first-.named conductor to provide thermal insulation for said second named con- 35': for said opening, at least one electrode mounted ,L'Otand'means for relatively adjusting the relative positions of said electrodes to establish symmetry of the device including means for adjusting the position of said closure member relative to the opening insaid hollow member.

32. An electron discharge device comprising an envelope including a hollow member havingan opening therein, a closure member for said opening, an anode' electrodemountedin said envelope, electron discharge device electrodes including a screen grid mounted on said closure member and extending into the hollow member in electronically operative, relation to said anode electrode, and means fo1 ,relatively adjusting the,

relative position of `said anode and screen grid to adjust the coupling therebetween including an adjustable joint between said closure memberl velope to face eachother in lelectronically op-` erative relation, and means for adjusting the positions of at leastr ,one4 closure member relative to the opening closed thereby to adjust thek relation of said electrodes Vsaidmeans including an adjustable joint.

i 34. VInman electron discharge device, a hollow. envelope member having openings in opposed walls thereof, a yclosure member for each `open-l ing, at least ,onenelectrode' structure on each closure member and. leadspthereto extending, through the closure member, said electrode struc,-YV tures eachy including' an electrode extending 19 within the tube in electronically coupled relation to each other, and apparatus for fastening said closure members over said openings and adjusting the position thereof relative to the openings to change the electronic coupling between said electrodes.

35. An electron discharge device having an envelope including a header member, a cathode assembly supported from said header member, a screen electrode insulatingly supported from said cathode assembly and surrounding said cathode assembly, said header member having a plurality of apertures extending therethrough, and leads extending from said cathode assembly and through said header, and a lead extending from said screen electrode and through an aperture, and a control electrode positioned between said cathode assembly and screen electrode and having a lead supporting said control electrode from said header member and extending through another of said apertures, and a closure member for said header member for providing an envelope, an anode adjacent said screen electrode, and a lead extending through said closure member and supporting said anode.

36. An electron discharge device having an envelope including a header member, a cathode assembly and a screen electrode insulated from each other, said header member having a plurality of apertures therethrough, and a plurality of leads extending from said cathode, one of said leads extending through one of said apertures, and a lead extending from said screen electrode and through another of said apertures, and a control electrode positioned between said cathode assembly and screen electrode and having a lead supporting said control electrode from said header member and extending through another of said apertures, and a closure member for said header member providing an envelope, an anode, and a lead extending through said closure member and supporting said anode adjacent said screen electrode, said leads compiising tubular members and providing a transmission means for a coolant to and from said cathode assembly, electrodes and said anode.

37. In an electron discharge de'vice, an envelope enclosing electrodes including a control grid, a support for said control grid including a coolant conductor sealed into said envelope, said conductor also serving as an electrical connection to said control grid, other electrodes in said envelope, electrical connections from said other electrodes passing through the Wall of said envelope and a metallic shield supported by one of said other electrodes and extending between said grid support and said other electrodes and their electrical connections.

38. In a push-pull electron discharge device, an envelope having an opening therein to be closed by a header member, two anodes supported in said envelope, other electrodes including two control grids and two screen grids carried by said header and extending within said envelope in electronically coupled relation to said anodes, said header being adjustable relative to said opening to establish mechanical and electrical symmetry between said anodes and screen grids, and neutralizing capacitors within said envelope cross coupling said anodes and control grids.

39. An electron discharge device comprising an envelope enclosing electrodes including two anodes in the form of metal blocks with luid channels therein, and supports for said anodes comprising parallel coaxial iluid conductors for each 20 anode extending through the envelope of said device, said coaxial fluid conductors serving to supply cooling fluid to and take cooling fluid from the respective anode blocks, said parallel coaxial conductors also serving as a part at least of a resonant circuit for said anodes.

40. In an electron discharge device, an envelope including a metal wall, a cathode structure on a cathode support carried by said metal Wall and extending therefrom within said envelope, a grid structure on a grid support carried by said wall and extending therefrom to face said cathode in electronically operative relation, and a brace fastened between the ends of said supports remote from said wall to prevent relative movement of the grid and cathode structures.

41. In an electron discharge device, an envelope including a metal wall, a cathode structure on a cathode support carried by said metal wall and extending therefrom within said envelope, a grid structure on a grid support carried by said Wall and extending therefrom to face said cathode in electronically operative relation, said cathode support and said grid support including metallic uid conductors extending from the control grid through the envelope, said fluid conductors serving to extract heat from the cathode structure and grid structure and to form electrical Connections thereto, and a brace fastened between the ends of said supports remote from said wall to prevent relative movement of the grid and cathode structures.

42. An electron discharge device having an envelope including a conducting header member, a cathode assembly and a screen grid assembly insulated from said cathode assembly, said cathode and screen grid assemblies being supported from said header member, said header member having a plurality of apertures therethrough, and a plurality of leads extending from said cathode assembly, one of said leads extending through one of said apertures and insulated from said header member, and a lead extending from said screen grid assembly and through another of said apertures and insulatingly sealed therein, and a control electrode positioned between said cathode assembly and screen grid assembly and having a lead insulatingly supporting said control electrode solely from said header member and extending through another of said apertures and sealed therein, and a closure member for said header member providing an envelope, an anode adjacent said screen grid assembly and a lead for insulatingly supporting said anode from said closure member.

43. An electron discharge device having an en-` velope including a conducting header member, a cathode assembly supported from said header member, a screen electrode insulatingly supported from said cathode assembly and surrounding saidv cathode assembly, said header member having a plurality of apertures extending therethrough, andleads extending from said cathode assembly and through said header, and a lead extending from said screen electrode and through an aperture and insulatingly sealed therein, andl a control electrode positioned between said cathode assembly and screen electrode and having a lead insulatingly supporting said control electrode from said header member and extending through another of said apertures and sealed therein, and a closure member for said header member for providing an envelope, and an anode adjacent said screen electrode, andy a lead ex- 21 tending through and insulatingly sealed in said closure member and supporting said anode.

44. An electron discharge device having an envelope including a conducting header member, a cathode assembly and a screen electrode insulated from said cathode assembly and said cathode assembly and said screen electrode being supported from said header member, said header member having a plurality of apertures therethrough, and a plurality of leads extending from said cathode, one of said leads extending through one of said apertures and insulated from said header member, and a lead extending from said screen electrode and through another of said apertures and insulatingly sealed therein, and a control electrode positioned between said cathode assembly and screen electrode and having a lead insulatingly supporting said control electrode from said header member and extending through another of said apertures and sealed therein, and a closure member for said header member providing an envelope, an anode, and a lead extending through said closure member and supporting said anode adjacent said screen electrode, said leads comprising tubular members 25 and providing a transmission means for a coolant to and from said cathode assembly, electrodes and said anode'.

PHILIP T. SMITH.

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

UNITED STATES PATENTS