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NOV» 12, w46» D. E. KENYON ZAÈQZZ HIGH FREQUENCY ELECTRON DISCHARGE APPARATUS Filed Jan. 3, 1942 2 Sheets-Sheet 1 DAVE D E. KENYON À@ AQPLNEY Nav. 12, 1945. D. E. KENYON 2,419,822 HIGH FREQUENCYELECTRON DISCHARGE APPARATUS Filed Jan. 3, 1942 .a 3 as’ ze' 9' 2 Sheets-Sheet 2 2|' s' m34 , 7' ‘ ‘l l ,\ z__'H’" ' ‘ Y ß «M 25' ‘f l i | x ‘ la l| | _ . ' i 5 "1» \\ i I INVENTOR DAVID E. KENYON . Y ’i vf ? ¿ma,ßATÍ'ORNEY. Patented Nov. 12, 1946 2,410,822 UNITED sTATEs PATENT oFT-’icE 2,410,822 HIGH FREQUENCY ELECTRON DISCHARGE APPARATUS David E. Kenyon, Smithtown, N. Y., assigner to Sperry Gyroscope Company, Inc., a corporation of New York l Application January 3, 1942, Serial No. 425,491 13 Claims. (Cl. Z50-27.5) This invention relates, generally, to vacuum tube structures and the invention has reference, more particularly, to a cathode structure designed for the production of high current density elec 2 used in starting emission does so in only a lim ited area of the emitter surface, the emission being spread from the original hot spot after the current through said heater element is turned tron beams. In prior art cathodes for such pur oil’. poses, great difficulty has been experienced in Other objects and advantages will become ap producing heater coils having very low magnetic parent from the speciñcation, taken in connec fields, Said magnetic fields having an undesirable tion with the accompanying drawings wherein tendency to modulate the electron beam unless the invention is embodied in concrete form. special shielding precautions are resorted to. It 10 In the drawings: has also generally been necessary to use oxide Fig. 1 is a fragmentary perspective longitudi coated emitting surfaces in order to produce nal cross-sectional view and wiring diagram of usa-ble emission currents, the temperature of the a form of the invention. emitting surface being usually limited by the Fig. 2 is a longitudinal cross-sectional view, maximum temperature at which the cathode partly in elevation, showing an application of the heater element can be operated and still give the cathode disclosed in Fig. 1. device a reasonable life of operation. The pres Fig. 3 is a cross-sectional view of a modified ent invention discloses a cathode structure rela form of a portion of Fig. 1. tively free of magnetic fields and whose emitting Fig. 4 is a fragmentary longitudinal cross-sec surface may be operated at elevated temperatures. 20 tional view of another modiñed form of the pres The principal object of the present invention is ent invention. to provide a cathode having an emitting surface p Fig. 5 is a plan view on a reduced scale of the portion that is heated by electron bombardment, structure shown in Fig. 4, taken along the line the electrons for effecting such bombardment 5_5 of Fig. 4. being supplied from a second surface. Fig. 6 is a fragmentary longitudinal cross-sec 25 Another object is to provide means for heating tional view of a further modification of the pres said second surface to a predetermined initial ' ent invention. temperature, and switching mechanism for then Similar characters of reference are used in all stopping said heater means and causing the ñrst of the above figures to indicate corresponding and second emitter surfaces to heat each other 30 parts. by means of a high voltage alternating current Referring now to Fig. 1, there is shown a pre acting from electrons emitted on the adjacent ferred form of the present invention. lSpiral surfaces of the two emitters. heater element I, supported by leads 2 and 3 An object is to provide a cathode emission sur which may pass through the conventional type face’relatively free of warping due to thermal 35 ' glass press (not shown) usually used in vacuum effects. tube structures to provide current lead and sup Yet another object is to provide such a cathode port means, is positioned preferably centrally structure for the production of cylindrical elec within a heat shield inner wall 4, leads 2 and 3 tron beams. Still another object is the provision of such a 40 passing through holes 5 and 6 in end wall 1 of the heat shield.~ 'I‘his heat shield has a folded cathode structure for the production of radially back portion in the form of a cylindrical Wall 8 projected electron beams. spaced outwardly from and concentric to wall 4, Yet another object is to provide such a cathode to provide more effective heat shielding by the in which all elements in use in other than start ing operations are heated by means of high volt 45 well vknown double-wall eiïect. Wall 8 extends below end wall 7 of said heat shield, and pressed age, low current electron beams, thus minimiz into the inner diameter of wall 8 is a second end ing undesirable effects due to magnetic ñelds. wall 9 for the heat shield, leads 2 and 3 passing An object is to provide a cathode structure in through holes I 0 and II in wall II. which heating ñlaments are operated only in centrally above spiral heater element starting emission, thus allowing said emitting sur 50 I Positioned is disk I2 which may be somewhat dished, in faces to be operated at very elevated tempera which case the convex side of disk I2 faces heater tures. I. Somewhat spaced from disk I2 on the side A further object of the invention is the provi sion 0f a cylindrical, radial or other beam pro thereof away from heater I is a second disk I3 . which may also be dished similarly to disk I2. ducing cathode in which the heating filament 55 Heater _I may be of tungsten and disks I2 and I3 2,410,822 4 of tantalum, columbium, nickel, or other metal 0f low electron work function; or heater I and disks causes electrons emitted from heater I to strike disk I2 with high velocity, thus heating disk I2 ` vI2 and ,I3may be oxide-coated with any of the to a temperature such that its upper side also begins to emit electrons. At this time, time ac well' known barium, strontium, etc., emission ma terials. On the side of disk |3 away from disk I2 is a focussing element with a central aperture nearly as large in diameter as the diameter of disk I3 and consisting of an inclined annular portion I4, a flat annular surface I5 `substan- " tially perpendicular to the axis of symmetry of the structure, l and aV cylindrical y-wall surface“ |6 extending- fromsurface I5 vconcentric to heat shield wall 8 and of somewhat greater diameter. tuated relay 43 has been set to open its associated » circuits, and time delay relay 4I closes, thus plac ing a moderately high alternating current volt age between disks I2 and I3. By energizing the disks I2 and I3 through symmetrically disposed leads 26 and 24 respectively, the magnetic fields i produced by the flow of alternating current into ther disks neutralize one another- and inhibit a1 ternating current modulation of the electron Focussing shield I4, I5, I6 may be supported by( ' stream. Electrons being emitted from disk I2 three leads I1, I8, -I'S spaced 120°„apartand exf .are accelerated toward disk I3 during alternate tending into the glass press of the vacuum kenve half cycles and impinge upon said disk I3 with lope surrounding the cathode. Focussing shield I4, I5, I6, supports, in turn, disk I3 by means of high velocity, thus heating it to incandescence. LAt the time disk I3 is raised to a sufilcient tem angularly spaced wires 20, preferably-symmetri- ' perature, it begins to emit electrons from -both cally disposed about the axis of the disk, e. g., 20 surfaces.` Those emitted from its under surface at 120° intervals in the manner shown in Fig. 3 are accelerated toward disk I 2 striking the latter. spot welded to the inner surfaces of shield por The alternating current voltage between disks I2 tion I4 and disk I3. Heat shield 4, 8 may be` and I3 thus maintains both at a proper tempera supported by three angularly spaced leads 2|, ture. also extending into the aforementioned glass Time delay relay 42 is set to close `its asso ciated circuit at the time when the upper surface Disk I2 may be supported by three angularly of disk I3 has reached a sufficient temperature to spaced leads 24 projecting radially'through holes emit electrons. Relay 42 then applies a high di 29 and 30 in Walls 4 and 8 of the heat shield. rect accelerating voltage between emission sur Leads 24 ,are supported by and are equally spaced face I3 and electrode 3|. _about a current distributor >such as a ring 25 Electrode 3| and its contained aperture 33 and concentric toY wall I6, which ring in turn is sup grids 32, and focussing shield I4, I5, I6 are so ported from theglass press by three leads 26, 21, designed that there is projected an electron beam press.y , f l 28, which may be mutually spaced at 120°. ~ The cathode structure may be positioned at a proper distance froman accelerating electrode 3 I, which may contain a central aperture 33 concentric to the axis of symmetry vof the cathode, containing therein grid bars 32, whose function is to further improve the shape of the electron beamto'be vprojected through aperture 33. In use, there is preferably applied to spiral heater I aI relatively low alternating voltage by means of leads 2, 3 from the connected second ary 34 of transformer 35. A moderate alternat ing voltage isv also applied between lead 2 and >diskr|2 from the secondary 36 of transformer 35 via lead 26, ring 25 and lead 24. Preferably a relatively high alternating voltage is applied be of uniform round cross-section into the space on the side of electrode 3| away from emitter I3. Thus, it is seen that when the cathode is in its final state of operation the heating and acceler ating currents involved are high voltage, low cur 40 rent ones, and that the only alternating heating voltage involved is well shielded inside of mem bers 4, 8, I2, I3, I4, I5, I6. Further, the final temperatures of emission sources I2 and I3 are not determined by a resistance heater unit -such as the spiral heater I, and since this spiral heater lI is in use only in starting the cathode, its life time is greatly increased. In fact, disks I2 and I3 may even be operated at temperatures much higher than those at which oxide-coated emitters tween disks I2 and I3 from a transformer 31 by 50 are usable, so that pure metal emitters of tan talum, columbium and similar metals may be way of lead I1, focussing shield I6, I5, I4, and used. It is evident to one skilled in the art that wires 20 on theone side and lead 26,' ring 25 and a variety of starting devices are usable to give lead 24` on` the other. ' A moderately high direct the desired starting cycle, so that the system of current voltage is applied between emitter I3 and electrode 3| from power supply 39 via lead I1, focussing shield |6,'»|5, I4, and wires 20 on the shown is intended to lbe purely illustrative. 55 .relays A cathode producing such an electron beam has» Transformer many uses, such as in beam power tubes, cathode v 44 is closed, time delay relays IIIA` and 42 being open so that no current flows to transformer 31 or power supply 39. Time actuated relay 43 is of In Fig. 2“, a cathode of the type described in Fig. 1 is shown mounted in a reflex-type electron one si'de and wire 38 on the other. ray tubes, in electron beam velocity modulating 35l is shownsupplied through a time actuated tubes such as those disclosed in patents, No. relay43, »transformer 31 through a time delay relay 4I, and powervsupply39 through a time 60 2,242,275 ventitled “Electrical translating system and method,” issued May 20, 1941, to Russell H. delay relay 42, all fromany; suitable alternating Varian and No. 2,259,690 entitled “High frequency current supply to which connection is made by radio apparatus," issued October 21, 1941, to John leads 40, 4t’.y . ~ ' R. Woodyard, William W. Hansen, and Russell H. W'hen it is desired to put the cathode into oper ation, the following procedure is used. >Switch 65 Varian and in other types of electron tubes. the well known commercial type which closes its beam velocity modulating device of the type dis closedin Patent No. 2,250,511 of Russell H. Varian circuit immediately „when switch 44. is closed, 70 and William W. Hansen. As therein described, being, set toppenl such circuit after any desired predetermined time> interval. With .-switchf44 an electron beam is projected through aperture 33 offth'eaccelerating grid electrode 3|, passes on closed, currentëfromtransform'er secondary 34 through field-free-space tufbe 45, and is velocity heats ñlament- I, and! the alternating 'current modulated by an ultra high frequency alternating voltagevappearing between heater I‘and ’disk'I2 76 electric ñeld appearing ‘between grids 46 and 41, andere 5 trons from spiral I is to heat an approximately circular area of emitter I2' just below and con centric to spiral I. Emission from s, correspond ing circular area on the lower surface of emitter I2.' then startaand if a moderately high alter nating current voltage is imposed between an nular emitters I2' and I3', a corresponding cir cular area on emitter I3' becomes heated. As quency characteristic of resonator 43. The ve locity modulated electron beam passes on through grid 41 and is reflected in the region near reflec tor plate 43, said plate `43 being at or near the potential o1' emitter surface I3. During the time required for the electrons to nrst pass through grid 43, becomerefiected by plate 43, and return - 6 emitter I 2'. The bombarding action or the elec# said alternating ileid being generated by a high frequency electromagnetic field of natural fre through grid 46, the velocity modulation has re 10 time passes, the two heated areas on I2' and I3' spread around _these annular members, and the sulted in density modulation, the electron groups thus produced returning energy to the electric entire surfaces of ‘emitters I2' and'l3' 4become neld between grids 46 and 41, thus maintaining hot enough to emit, the voltages betweenl leads the electromagnetic ñeid in resonator 43. Ultra 2 and 3 and between leads 3 and 23’ having been high frequency energy may then be removed from removed at the proper time as in the above pre viously described sequence ofevents. At approx resonator 48 by means of well known types of coupling devices (not shown). It is evident to imately 'the time when the entire lower surface ‘ one skilled in the art that beams of various de of cathode emitter I3' has become hot enough grees- of convergence or ,divergence may be ob . to emit electrons, a high direct voltage is placed tained from such a cathode structure, depending 20 between cathode I3' and electrode 3l", thus pro chiefiyupon the design of _the focussing element jecting a cylindrical electron beam through an I4, I5, I6, or upon the use of cooperating mag ‘nuiar aperture 33' and into the space below ac celerating electrode 3 I '. Fig. 6 illustrates a cathode producing an out are slightly concave. The degree of concavity 25 wardly radially projected electron beam. Emitter is such that the percentage distortion of the disk , I2", concentric to spiral filament 54, is illus netic focussing means. \ ' As shown in Fig. l, emitter elements I2 and I3 is very much less for a given temperature change than that obtaining in the case of a flat emitter surface. The structure shown in Fig. 3 may ibe used in place of the disks I2 and I3 in Fig. 1. 30 trated as the figure of revolution of an arc of a circle about the axis of the heater 54. Emitter I3”, is also similar in shape and concentric to emitter I2". Above and below emitters I2", I3" are positioned two short cylindrical boxes 51 and 58, whose walls 4" and 8" act as heat shields. In Fig. ,3, the convex disks :50, 53 have cylindrical walls o‘rskirts 5I, 52 of equal diameter attached to their respective peripherles, extending inward l Concentric toand attached to emitter I3” is a ly so that said walls areseparated lby a small gap. focussing element consisting of annular inclined Such a construction _improves freedom from warp- ' 35 portions I t", cylindrical wall I5", and apertured ing due to- temperature changes, and forms a morecompletely closed chamber so that electrons accelerated back and forth between disks 50 and 53 have less chance to migrate »out of the space wall I6". Heater 54 is positioned and has its power-supplied by leads 55 and 58, lead 56 may also support heat shield 53; Heat shield 51' may be supported by lead 2i". Emitter I3" and` defined between said disks. 40 focussing shield I4", I5",` I6" may be supported ~ ` Electron beams of annular, radialv or other character may be produced by the rotation ofthe cross-section surface of the device shown in Fig. from leads I1", I3", in the conventional manner. The method of operation of the cathode of Fig. = -` 1 about an axis external thereto, in any'desired projected electron beam resulting. It is obvious manner. Two ofthe possible resultant configura tions are disclosed in Figs. 4, 5 and 6. Referring to Figs. 4 and 5, there is shown a 6 is exactly similar to .that of Fig. 1, a radially ' -to one skilled in the art that beams of ring shaped cross-section, diverging or converging, can b_e made by placing the axis about which the cathode for the production of an annular beam, ~of a. type which may be used in an electron ve cross-section of Fig.'1 is rotated at various angles between the two used to produce the structures locity modulating device such as the high power 50A of Figs.«4 and 6, such cathodes being useful in oscillator shown in Fig. 'I of the aforementioned producing beams ofthe type shown in Figs. 13 Patent No; 2,259,690. Enclosed in an annular and 15 of the aforementioned prior Patent No. heat shield composed of annular walls 4', 1', 8' and 9" are two coopera-ting annular emitters I2', As many changes could be made in the above . I3’. The electron beam -from emitter I3'.is im 55 constructionl and many apparently widely dif proved in form by annular focussing member I 4', ferent embodiments of this invention could be I5', I5",and projected toward electrode 3 I ', which may contain annular grid structure 32' in aper- ‘ made without departing from the scope thereof, 2,259,690. _ ' , it is intended that all matter contained _in the ture 33', if desired. Focussing ring I4', I5', I6' and emitter I3' are supported by leads I1', I8', 60 above description or shown in the accompanying drawings shall be interpreted as illustrative and . I3', heat shield 4', 8', 1', 9', by leads 2l', and emitter I2' by ring 25' and leads 25', 21', 28' all not in a limiting sense. of said leads being supported in turn from the glass press Vof the vacuum tube envelope or by other suitable well known methods. ' Starting filament I and cooperating leads 2 and 3 may be exactly similar to the starting nia ment shown in Fig. 1, as is seen in Figs. 4 and 5, or may actually be a ngure of revo tion as a What is claimed is: - 1. Electron discharge apparatus comprising a 65 substantially planar iliamentary element adapted to serve as a source of electrons when heated, ay ßrst emitter presenting a, relatively large surface area. to said element, means connected to said eie ment and said emitter for providing a difference ribbonîa wire, or any other suitable form. In 70 of potential between said element and said emitter whereby electrons leaving said element are caused to bombard said emitter with high is similar to that of Fig. 1. A proper current is velocity, a second emitter adlacently spaced from vallowed to ñow through lead 2, spiral I, and out said ñrst emitter, and means connected to said lead 3, heating the illament, and a proper alter operation, the simple spiral cathode I of Fig. 4 nating voltage is imposed between niament I and 76 emitters for providing an alternating voltage be 2,410,822 . tween said emitters whereby said emitters heat emitters for rendering said heating means in operable after a predetermined period of- opera each other by mutual electron bombardment. 2. The apparatus defined in claim 1, including time actuated relay means connected to said ele ment for automatically rendering .said element inoperable to bombard said ñrst emitter after a predetermined initial heating period. tion and for applying said alternating voltage be tweensaidy emitters, an electron beam-control - 3. Electron discharge apparatus comprising two substantially parallel electron emitter elements, , electrode mounted in spaced alignment with the non-bombarded electron emission surface of the other of said emitters. and time controlled means for applying a substantially unidirectional elec tron accelerating voltage between said other means in said apparatus supporting said ele 10 emitter and said electrode. ' ’ ments in adjacent relation, said supporting means 7. Electron discharge apparatus comprising a including. leads symmetrically», disposed with re heater element, a substantially cup-shaped heat spect to and extending from said elements, shield partially enclosing said heater element, and - means connected to said leads for applying an substantially parallel spaced emitter elements alternating voltage between said emitter elements 15 supported substantially across the-open end of so that they heat each other by mutual electron said shield, said emitter elements being non-con bombardment, said symmetrical disposition of ductively connected with said shield. leads tending to neutralize the magnetic effects 8. 'I'he apparatus deñned in claim 7, including produced by the flow of current through said / means conductively interconnecting said heater leads to said elements, an electron permeable 20 element and said shield. conductive member mounted in alignment with 9. The apparatus deiined in claim '1, compris ' said elements and adjacent the non-bombarded surface of one of said emitter elements, means connected to said one emitter element and said member for applying a substantially unidirec tional voltage between said one emitter element and said _member for accelerating electrons emitted by said non-bombarded surface, and an electron beam focusing means mounted inter mediate said one emitter element and said mem ing fixed support means electrically separated from said shield, and means on said support means mounting said emitter elements in said 25 spaced relation. 10. Electron discharge apparatus comprising two spaced electron emitter elements, means con necting said elements for producing an oscillating potential between said elements such that they 30 heat each other by mutual elec-tron bombard ber. ` ment, an electron focusing electrode disposed ad 4. The apparatus deñned in claims, including jacent a non-bombarded surface of one of said a iìlamentary heater member adjacent the other emitter elements, and means supporting said one of said emitter elements for initially heating said emitter element from said focusing electrode. other emitter element, and time controlled means 35 11. Electron discharge apparatus comprising a connected to said heater rendering said heater pair of electron emitter members adapted to be inoperable when the non-bombarded surface of energized by a stream of electrons and mounted said one emitter element becomes electron emis-` in closely spaced adjacent relation to be capable sive. of mutual electron bombardment of adjacent ’ 5. Electron discharge apparatus comprising two 40 surfaces, and skirt-like peripheral walls on each spaced emitter elements, electrical ‘means con nected to said elements in a predetermined sym ~metrical arrangement for applying a relatively high alternating voltage between said elements of said members extending toward each other providing a shield about the electron discharge between said surfaces. 12. Electron discharge apparatus comprising a so that they heat each other by mutual electron 4. cathode assembly comprising spaced emitters bombardment of adjacent surfaces, and beam~ adapted to heat each other by mutual electron forming electrode means mounted in alignment Ibombardment,'means connected to said emitters With‘said elements for forming the electrons leav for energizing said emitters, and means aligned ing the non-bombarded surface of one of said with said assembly and operable only after said emitter elements into an electron beam of sub energization has proceeded to a predetermined stantially uniform cross-section, said emitter ele condition for accelerating electrons from a non ment electrical arrangement shielding said beam v bombarded surface of one of said emitters. against undesired magnetic disturbances from 13. Electron discharge apparatus comprising a heating currents in said emitter elements. heater element, a substantially cup-shaped heat 6. Electron discharge apparatus comprising two spaced electron emitters, means in said appara tus adjacent one of said emitters for heating said one of said emitters by electron bombardment, electrical means connected to said emitters for providing an alternating voltage between said emitters such that they heat each other by mutual electron bombardment, time controlled »means connected to said heating means and said shield partially enclosing said heater element, an emitter element supported substantially across the open end of said shield and non-conductively connected therewith, and electrical means con necting said heater element and said emitter ele ment for supplying a difference of potential be tween said elements. DAVID E. KENYON.