US2853641A

US2853641A - Electron beam and wave energy interaction device

Info

Publication number: US2853641A
Application number: US482921A
Authority: US
Inventors: Stanley E Webber
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-01-20
Filing date: 1955-01-20
Publication date: 1958-09-23
Anticipated expiration: 1975-09-23
Also published as: GB817283A

Description

Sept. 23, 1958 s. E. wr-:BBER

ELECTRON BEAM AND WAVE ENERGY INTERACTION DEvIcE Filed Jan. 2o, 1955 l l I f f f ELECTRON BEAM AND WAVE ENERGY INTERACTION DEVICE Stanley E. Webber, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application January 20, 1955, Serial No. 482,921

18 Claims. (Cl. S15-3.5)

This invention relates to electron collecting methods and collector structures for collecting electrons in electron discharge devices. While this invention may be utilized in combination with a wide variety of electron discharge devices, it is ideally suited for utilization in electron beam-type interaction devices and Will be particularly described in that connection.

Devices of this type include velocity and density modulated tubes, such as klystrons and continuous interaction devices which are often described as traveling wave tube structures and, by way of example, the collector structures and methods of this invention will be described in connection with traveling wave tubes.

Electron disch-arge Continous interaction devices of the traveling wave tube variety include a slow wave structure for propagating an electromagnetic wave along the structure at reduced velocity. The slow wave structure defines an interaction region through which an electron beam passes to interact with the electromagnetic wave. The electrons in the beam are accelerated to an average velocity somewhat in excess of the 4velocity of Vpropagation of the electromagnetic wave along the helix axis. This results in energy from the electron beam being absorbed by the electromagnetc wave and an increased output from the output end of the slow wave structure. The resulting extraction of energy from the electron beam results in a reduction in the average velocity of the electrons in the beam; however, even after having passed through the interaction region, the electrons in the beam still have a relatively high velocity and must be collected by a collector structure.

Collector structures are often water-cooled or p-rovided with cooling ns in order to dissipate the large amount of heat generated by the electron bombardment of the collector. Thus, the electron beam energy is, in part, converted to heat which is lost to cooling medium. Therefore, methods and apparatus have been devised to increase the eiciency of the interaction device by recovering as large a portion as possible of the energy in the electron beam after the electrons have passed through the interaction region and before collection.

One apparent method is to maintain the collector struc-k ture at a potential lower than the potential of the helical structure so that the electrons in the beam after passing through the slow wave structure are rapidly decelerated andy strike the collector structure at relatively low veloci-y ty, the energy from deceleration being returned to the power supply and the eiciency of the interaction device accordingly enhanced.

The electron velocities thus far discussed have been average velocities, i. e., there is a distribution of electron velocities in the beam so that no matter what decelerating voltageis utlized, there is a tendency for` some of the electrons to return to the interaction region. The electrons returned to the interaction-region are those electrons having a lower energy than the deceleratingpo-` tentialy so that they are effectively acceleratedintothe "hired States arent ice interaction region and in addition those secondary electrons from the collector which result when electrons having a considerably higher energy than the decelerating potential strike the collector. These secondary electrons or backward traveling electrons are accelerated by the higher potential of the helical structure and therefore travel back through the interaction region at high velocity. These returning electrons result in instability and reduced eiciency of the interaction device. The returned electron current can then be considered to be a form of feedback tending to cause the interaction device to oscillate.

In view of the foregoing, it is therefore apparent that it is desirable to provide a method and apparatus for enhancing the efficiency of the interaction device by slowing the electrons in the electron beam to substantially zero average velocity before collection while at the same time preventing the return of low velocity primary electrons and secondary electrons to the interaction region. This desirable combined result of increased eciency and stability is achieved by the method and apparatus of this invention.

Therefore, it is an important object of this invention to provide an improved electron collector structure and method of collecting electrons which enhances the efficiency and stability of an electro-n discharge device.

Another object is to provide improved electron collecting methods and collector structures.

It is also an object of this invention to provide an apparatus and method for collecting electrons in an electron discharge interaction device, including an interaction region, whereby the likelihood of the return of primary and secondary electrons to the interaction region is minimized.

A further object of this invention is to provide a meth- 0d and apparatus for minimizing the emission of secondary electrons from beam-type collector structures.

In accordance with an aspect of this invention there is provided an interaction device including an interaction region and means for establishing a beam of electrons` within the region. A collector structure is provided for collecting the electrons in the beam, after they have passed through the interaction region, which includes a suppressor electrode and a collector electrode oriented along said beam. The collector electrode is oriented relative to the suppressor electrode so as to increase the eiiciency of the interaction device and to minimize the number of electrons returned to the interaction region from the collector structure.

The other objects and important features of this invention will become apparent from the following specilication and claims when read in connection with the figures of the drawing in which Fig. l illustrates a traveling wave tube utilizing a helical slow wave structure and incorporating this invention. Figs. 2, 3 and 4 illustrate modiiied collector structures which may be utilized in the practice of this invention.

It should be understood that the collector structures and methods of this invention, while being particularly suited for utilization in electron beam continuous interaction devices, such as traveling wave tubes, are also suited for utilization in other interaction devices, such as klystrons. It will also be readily apparent that the use of a helical slow Wave structure is given merely by way of example, since the apparatus and method of this invention are also ideally suited for utilization in continuous interaction devices utilizing other forms of slow wave structures.

Fig. l illustrates an electron gun lt) consisting of electron emitting cathode 11, heater 12 and accelerating anode 13. The electron gun produces a stream of electrons 14 which ow through interaction region 15, suppressor` electrode 16 andare collected on metallic electron collector electrode 17. A helical slow wave structure 18 is provided in the interaction region and has input lead 19 andoutput lead 20 penetrating enclosure 21.--Enclosure 21, whichmay for example be ofglas's orcerarnic, encloses 'electron gun 10,;interaction region A15v and fsuppresser electrode1'6. A glass-to-meta-lfseal:is formed b'etween enclosure 21 -and collector electrode'17 "and itlii's electrode 'may be provided with [cooling ns "and/or water cooling apparatus ofconventional `design whichfextracts heat energy conducted to the outer'surfac'e offthe metallic collector.

A 'heater powerfsupply 22 provides heatercurr'er'itf'for the electron gun 'and one side of the 'circuit r'riakesfel'e'ctrical connection to the electron gun at 23. Power supply 2'4"-provid'es 'tlre "necessary accelerating and decelerating potentials for the various components of the 'interaction device. Lead 25 provides an "adjustable potential for accelerating 'anode '13, lead 26 provides an ladjustable potential for 'the `slow wave structure `18, V'lead '27 provides a small accelerating potential for suppressor electrode 16 and lead 28 provides a decelerating potential to 'the collector'electrode 17.

'A 'solenoid 29"surrounds the interaction regio-n and a portion o -f the suppressor electrode to provide a substanti'ally uniform magnetic Vti'elrl 'in vthe 7direction findicated by-th'earrows This is 'the conventional collimating and beam focusing hel'd used intrave'ling 'wave tube structures 'of this type. in accordance 'with 'an aspect o'f thisinventio'n, airnagne'ticishield or, for"example, a bucking coil 30 is provi'dfedto "shieldatdeast a portion "of l the :collector structure,"wliieh 'includes suppresser-"16 "an'dj collector V17, from the* uniform magnetic beam focusing held. Solenoid"3`0 l'prtnduces Ia magnetic eld'sub'stantfially opposing Ithe uniform magnetic eld as indicated-'bythelarrowsH.

The etect of the bucking eld set up by"solerioid 30 is'to createfamgnetic'field:having a radial component, i. e., a" co-rn'ponefnt`in a` direction transverse to the path of the'lect'rtmjsV in` the electro-n beam 14. 'This transverse componet'of'the field is generally indicatedl by arrows l plied to Vtheinteraction'device from powersupply 24 are'given merely by' way of eX- amp le"an d"sho' uld be 'considered to be variable'in accordance wit'l 1 fthe"'pa`r'tici`ilar interaction device'utilized, the' load and electronjbeam-cur'rent density.

T he"` nte'raetion devicefillus'trated in Fig. l'operates substantially 'in the 'ffollowingdmanner: electrons'in'the electron` beamfa're accelerated bythe accelerating anode 1 3` andthe slOWW/e helical structure lo" to avelocity in the order lof 5,000 volts. An inputelectroinagnetic wave is applied to the input lead 19 andpina well-known manner, interaction takes place between the electro-ns in the electron beamand thefelectromagnetic wave on theslo-w wavestructu're to result in an amplied output at lead 20 of theslow wave structure.

For example, Aitis assumed that the average velocity ofl theelectrons 4theelectron beam are slowed to a minimum energy in theorder of 3,000 volts at the instant they pass thelast turnof the helical slow'wave structure and start to enter `the suppressor electrode cylinder `16. The welectrons are then accelerated to an increased potentialof approximately 1 ,000 volts as a result of the approximately 1 ,000fvolt'potentialdierence between the helix `which is maintained at 5,000 vo-lts and the suppressor whichis maintained at 6,000 volts.

It is well known that electrons 4having'a component of velocity transverse to Va magnetic field`will"tend to deviate from the direction of'this transverse velocityin a spiral path. Therefore, the electrons travelingthrough the suppresso-r electrode 16, which is formed of nonmagnetic material, tend to spiral toward the inner surface of' electrode116 asaresult of the'transversemagnetic iield indicated by arrows 31. A number of electrous tendfto be collected on the suppressor electrode; however, a major portion tend to spread out as indicated by arrows 32 so as to strike the inner surface of collector 17. Electrons leaving the suppressor cylinder 16 are rapidly decelerated since the collector 17 is, in this example, maintained at a voltage of approximately 2,000 volts. It will be noted that the differing diameters of the suppresso'rlfand collectorrespectively and the potential dierence between the two electrodes results in an electric lens action therebetween `which increases Y the tendency of electrons in the lbeam to -deviaterfrom the original beam path and strike the sides of the elongated collec-tor.

It will be noted that the-collector consists of an elongated cylinder several times as long as the diameter thereof and ending in an elongated conical end portion. Thus, the electrons 32 which strike the side walls of collector 17 with suthcientenergy to cause theemission of a secondary -ele'ctr'onor electrons will necessarily 'result in a secondary *electron which vfollows Y a path, such as'p'ath 33. Thus, the secondary electron is reected 'a numberof times in the cylinder land in the conical end portion andtherefore'may bey absorbed-without ever being able to return to the entranceli ofthe collector.

The collectorelectrode l"17, ineffecLacts as a Faraday cage wherein it is'difcult for `electronsimpinging at'an angle-on the collector electrode I'walls to return to the entrahceof the cage. That is, the-secondary electron or electrons leaving the walllof collector 17 have a cosine density distributionfabout `an' angle of" reflection which is substantially equal to Ithe angle 'of lin'cidence of the primary Yelectron from theifb'eam.

*Electrons-which leave the collector 17 tend to be deflected-fromthebeam path by the fringing' electric eld between suppressor electrode 16 'and' collector 'electrode 17 Iand`will therefore tend to 'be collected on suppressor cl'ectrodef16. These lowvelocity"electrons areifurther trns'have'a'n initial lowL energygany that are not' collected bythe'suppressor electrodes are further 'decelera-ted'by the 'decelerat-in'g' potential between :the'suppressor electrode 16 Iand the helix 18 so that 'in'g'en'e'ralthe'se electrons are' returned to the'sup'pressor andcollcted. Prima'ryelectrons from the electrontbeam'which have such low energies as to have their direction'rever'sed lby the delerating field between `thesuppre'ssor- 16 and collector-17 are affected in a similanmanner" as'the previously describ'edseconda'ry electronso 'that' there' is little lkelihood of the primary electrons being returned to theinteraction region.

Itis therefore apparent that the apparatus4 and method o f'this invention provide for 'the deceleration of electrons in the electronV beam tofrelatively low velocitiesso that they substantially drift into`the collcctor'tand. produce relatively little heat'while, 'at the same time, providing for the suppression of low energy' primary electrons and the secondary electrons' produced 'by high energy primary electrons.

Insomeapplications of this invention, it is desirableto limitthe amount 'of' electrons collected by'the suppressor, particularly thel relatively'high-l energy primary electrons. This is because it is often more desirable to rstgdecelerate the primary electrons and collect them'on a cooled collector electrode. In these instances, the uniform magnetic field'fprovided by; solenoid 29 is' extended; beyond the deceleration' gap formed between suppressor' electrode 16 and colljc'torwelectrodev 17 and a magnetic shield or'a bucking1 coil,such"`-as solenoid'SO, "is` provided at an inter`4 mediate regionof the'elongated portion-of collector 'electrode'117. 1FThis res'ltsiin a"'sl'ibstanti'ally'uniformV magneticfeldthroughout the regioni of thesuppresso1i-clecv A trode and the collection ofsubstantially all of the primary electrons and the major portion of any secondary electrons on the collector structure land a resulting decrease in the amount of power which must be dissipated by the suppressor electrode.

It should be noted that with this alternative mode of operation and alternative structure, it is increasingly important that non-magnetic materials be used for the suppressor electrode 16 and collector electrode 17 in o-rder to prevent undesired distortion of the magnetic fields. This mode of operation results in electrons traveling a long distance before being collected at the right hand end f elongated collector electrode 17. Thus, relatively few electrons are collected on the suppressor and substantially all are captured by the long collector and are not returned to the helix. With the resulting transverse magnetic field component at an intermediate portion of the elongated collector the same electron spiraling will be observed for both primary and secondary electrons as was previously described in connection with the discussion of Fig. 1 except that the spiraling tends to occur subsequent to deceleration and therefore beyond the suppressor electrode 16 for forward traveling electrons.

Fig. 2 illustrates a modified form of the collector structure illustrated in Fig. l wherein only the collector structure is shown. Like portions of this illustration are designated by the same reference numerals as were used in describing Fig. 1. It will be noted that this ligure illustrates a slow wave spiral structure 18 and suppressor electrode cylinder'16 which is maintained at a higher potential than the spiral by means of power supply 35 and a cooled cylindrical collector electrode 17 of slightly larger diameter than the suppressor 16 which is maintained by power supply 36 at a lower potential than the suppressor and spiral.

An important feature to be noted in the illustration of Fig. 2 is the metal post 37 in the center of the collector 17 which extends a short distance into the suppressor cylinder. This metal post provides an additional fringing electric field 38 between the post and suppressor electrode 16 which tends to deflect electrons in the beam 14 away from the path of the beam and towards the inner wall of the suppressor electrode and the collector electrode. The post therefore enhances the lens action effected between the suppressor electrode and the collector electrode and decreases the likelihood of any electrons irnpinging on the suppressor or collector electrodes at such an angle as to result in secondary electrons being returned toward the interaction region.

It is further noted that the fringing electric field tends to deflect any secondary electrons or slow primary electrons from the beam toward the inner wall of the cylinder. Fig. 2 also illustrates diagrammatically a a cross-magnetic field having flux lines 38. This cross-magnetic field is provided in addition to the small transverse field which is set up bya magnetic shield or a bucking coil, such as that illustrated in Fig. 1.

Any magnetic field having a transverse component, such as a circular or elliptically polarized magnetic field, is desirable in the practice of this invention to act as an aid in causing electrons entering the collector structure to be deviated from their initial path and strike the side walls of the collector at such an angle as to reduce the likelihood of any resulting secondary electrons being returned to the interaction region. It is noted that this cross-magnetic field may be used in connection with a bucking coil, such as illustrated in Fig. 1, or alone, or alternatively, where the electrons in the electron beam are decelerated in a uniform magnetic field before being electrostatically and/ o-r electromagnetically deflected.

In general, electrons in the beam tend to be defiected away from the post due to the fringing electric field and therefore the tendency to heat the post due to direct bombardment is minimal; however, a hollow or annular electron beam canbe used so that any possibility of electron bombardment of the'center post is substantially eliminated. l y I The transverse magnetic fieldillustrated in Fig. 2 tends to deflect returning secondary electrons in the opposite direction to the primaryl electron because of the different direction of electron motion relative to the magnetic field. This opposite direction of deflection is not materiall since the suppressorelectrode and the collector electrode are cylindrical in shape and any direction of spiral defiection from the axial path of the beam tends to result in collection of electrons by the cylinder. v

A particularly desirable way to remove secondaries and/ or prevent the return of backward traveling electrons is to deflect the whole electron beam through a large angle, for example, 45 by utilizing a cross-magnetic field and then decelerating the electrons and collecting them in a substantially magnetic field-free region.

An apparatus in accordance with this invention incorporating this last-mentioned manner of collecting electrons and preventing the return of backward traveling electrons is diagrammatically illustrated in Fig. 3 of the drawing which shows a collector structure enclosed by glass wall 39. A suppressor electrode 16 is maintained at a potential above the helix 18 potential by a power supply 40. A collector 41 for the primary electrons is maintained at a potential lower than the helix and suppressor by power supply 42. A secondary electron collector 43 is maintained at apotential above the potential of the suppressor electrode by power supply 44. AA magnetic field 45, by way of example, is illustrated as directed into the drawing. A decelerating gap 46 is provided by the gap between collector electrode 40 and electrode 47 which is maintained at, or substantially at, the suppressor potential. Y v

Electrons inthe electron beam 14 are deflected at an approximate angle of 45 so as to impinge on the collector 40. The magnetic field 45 is of sufficient strength and maintained over a large enough region s o that substantially all of the electrons in the electron beam are deflected. These electrons are then decelerated as a result of the potential difference between electrode 47 and collector 41 so as to drift into the collector electrode.v The magnetic field effectively sorts the electrons due to the inherent electron velocity distribution so that all electrons are not deflected by the same angle and the probability of collection of electrons in the side walls of parts of the collector structure, due to spreading of the beam, is enhanced. It is noted that Where desired a plurality of collectors can be utilized. These collectors may bemaintained at different potentials and/ or positions so as to selectively receive electrons of given velocities which have been effectively sorted by being passed throughv a transverse magnetic field. The lens effect of the decelerating gap 46 also causes the electrons to tend to deviate` fro-m a direct path into the collector electrode and to be received on the side walls of the collector electrode.

This effect may be further enhanced by utilizing a center post, such as that shown in Fig. 2 of the drawing. Any slow moving primaries which are effectively slowed down and turned around by thekpotential differences at the decelerating gap, as well as any secondaries which can escape from the elongated primary collector 41, are deflected in the opposite direction by the magnetic field 45 as indicated by the dashed arrows and are collected by vhigh potential secondary collector 43. Thus, it is readily apparent that once the electrons in the beam are deflected in a direction to strike collector 41, there is substantially no possibility of any of the electrons, either decelerated primaries and/or secondary electro-ns which escape from collector 41, ever reaching the interaction region or the helix. n

The power supply 40 is an additional safeguard against any stray slow moving electrons returning to the interaction region or the helix and, in general, it is not neces- 7 saryffon .the proper operation of this particular .embodif ment.

Fig..4 illustrates. a, furtherfmodiiication of ths invention, wherein like. members from. previously described figures f of, the drawing ,aredesignated by. the same Vreference numerals. This. particular vcollector structure utilizes asuppressor electrode cylide111 6,and,l in addition, a secondary electron. collector electrode 48. in. combination Witlran'V elongated .air-cooled and/.or water-cooled, c ollec tor electrode 17 It will be noted that themetalpost. 37 which is similar to that,illustratedand,describediin connection with Fig. 2 of thedrawng, extends through the secondary electron collector electrode 4,8and .into the. suppressor electrode cylinder` 161so that .an `electric eldds. established between this, center post and thesuppressor. and secondary electron collector electrodes,-Y This results in the Vd ellecton Ofprimary electrons, from the, electron lbeam and secondaryelectrons` from` other por-,tions of the collector struc:-V

ture to' strikel portions'of thefcollector structure.

Power supply 49-is, in this-example, provided with av that there is a deceleration and diverging lens effect between the suppressor Velectrode 16' and the secondary collector electrode 48 which is maintained at a lower potential. than the suppressor electrode. Also collector electrode 17, is maintained at a lower potential` than electrode,

48v so that there is a'further. electron deceleration between secondary electron collector 48. and collectors .electrode 17.' VThe secondary collector electrode collectsanyslow secondary electrons returned from. the` main collector electrode 17 and iS `Operated slightly positive Withrespect to the main collector electrode, for. example, vlOOfyolts.

It will be readilyv apparent. that .the magnetiod'ields 'and/or combination-'ofimagnetic eldspreviously discussedin connection with. Eigs. l and 2 canreadily be adapted for utilization in connection` .with the structure illustrated in Fig. 4 andA thatiin'connection withall ofthe iigures herein illustrated? by .way of example, various combinations of deliectingelectroden electrostatic lenses,

andone or more combinations. Yof. magnetic fields can bel utilized to efect embodimentsof this.. invention.`

In viewof the foregoing, it,v will. be readilyV appar-.ent that only a few of the large number of modifications and variations of this inventionhave.beenjillustratedand described and that many. of those .not Aillustrated can, in view ofl the teachings herein, be readily adapted to other Velectron discharge structures. Therefore, ity is intended in the appended claims -tov cover .allmodiiications and variations coming withinthe true spirit. andrscope of this invention.

What I intend to Vclaim and protectyby Letters Patent of the United States is l. Inan electron beam, and wave energy interaction device including means for establishiiig` a beam of4 electrons in an interaction region Vand a magnetic field for focusing said beam, a' collector structure for. said electrons comprising a suppressor electrode and collector electrode loriented along said beam, means maintaining said collector electrode at a lower potential than said suppressor electrode to decelerate` electrons in -saidf beam andf'increase the eilliciencyfofthedevice and means providing a magnetic field having a component substantially transverse :to said beamzina region kprior'to deceleration ofthe electrons in said.` beam -to deilect electrons. from the-beam and shield at,- leasta portionof the collector from the-magnetic-focusingeld.

2. In an electron beam and wave energy interaction device includingmeans `for-establishing a beam ofV electrolls -Within anfinteractionregion and a magnetic focusing field, a collector structure lorgsaidV electrons. compris.

ing.a.Supnressorfelectrcde andcollector electrode. .oriented along ysaid beannmeans maintainingY said collectorV elec.- trodeata lower potential. than.l Saidf Suppressor; electrode. to fdeeelerate electronsinsaid heartland increase. .thee ciency of the device and magneticvmeansiproviding, a; magnetic iieldhavinaa component substantially trailsverseto, the beam finaregion subsequent to deceleration oithe electrons in thebeam to detiect electrons. Afromlthe beam4 and Shieldr at. least au portion cf the. Collector ,from the magneticiocusing ield. v

3 In an electrony beam and wave energy interactionv device including means Afor establishing a beam4 of. elec; trons within, an in teractionregion, a collector structure forsaidV electrons. Comprising a Suppressor. electrode.,v .a secondary electronl collector. and` a primary electroricol:

lector oriented alonssaidfbeam. and'rneans maintaining said secondary electron collector Lat a potential,...bmrvv1 the potentialv of4 the., .silmiressoi electrode and t means for maintainingY the primary electron collectorat apotential belowthe secondaryelectronV collector whereby the elliciency of the interaction device is enhanced andthe number of secondary electrons. returning tothe inter.-v `action region is minimized.

4. In an electron beam and wave energy interaction device .including means for establishing a beam of electronsinV an interaotionregion, a collector structurefor, saidelectrons,comprising a suppressor electrode and collector electrodo oriented along said beam and an electrically conductingmember coupled to the collector elec: trode 'and` extending into the suppressor electrode.

5,.,In anelectron beam, and, wave energy interaction device including rneansr, forwestablishing a' beam 0f; @lctrons. in, an interaction. .reg;iona collectorV` structure ,forl said electrons .corrierieine a suppressorl electrode and co1-t lector electrode oriented along said beam, meansmain.- taining said. collecter electrode at alower. potential than said` `suppressor electrode,to decelerate electrons-in said beamand` increase the, e'iency. ofV the device, and an electrically conducting member coupled to the collector, electrode, and. extendinginto. the suppressor electrode to provide adeflecting electric lieldto causeielectrons 'travel'- ing in a direction parallel tosaid beam to be detlected ina direction substantiallytransverse toV thedirection o f, the beam..

6. In an, electron beam;- andwaVeenergy. interaction device includingmeansfor establishing a beam o f electrons ,in an interaction region and. a magnetic focusing iield, acollector structure for saidelectrons comprising a suppressor electrodev` and collector electrode oriented along said beam,means maintaining said collectorelectrode at alower potential, ,than saidl suppressor electrode to decelerate electrons in `said beam and increase the eiciencyof the device, an` electrically conducting -,member coupled. to-the collector electrode and extending into the suppressor electrode .to provide ak deflecting electric, iield to cause electrons traveling in a direction substantially parallel to said beam to be deflected away vfrom thebeamandmagnetic means providinga magnetic'iield substantially transverse to the lelectron beam to deflect electrons from the beam path and shield atleast a por.- tionof thel collector structure from the magnetic focusing iield.

7. In an electron` beam and wave energy interaction device of the type definedl in, claim 6 wherein the magnetic iield, substantially` transverse to the electronhbeam is provided `in aregion Where electrons in the beam have not `been decelerated by the decelerating potentialon the .collector electrode.

8. A collectorstructurefoi the type kd elined by claim 6 wherein the masneticwfield iS providedV iria kregion.- whereelectrons in theelectron beamhave beenl decelerated; by the decelerating` potential onthe collector electrode.

9,. In an electron, beam andy wave energy interaction device including.. means .-fcr. establishing. aniaiiiiulanelesf.

tron beam within an interaction region, a collector structure for said electrons comprising a suppressor electrode and collector electrode orienied along said beam and an electrically conducting member coupled to the collector electrode and extending into the suppressor in a region of low electron density.

10. In an electron beam and wave energy interaction device including means for establishing a beam of electrons with an interaction region, a collector structure for said electrons comprising a suppressor electrode and collector electrode oriented along said beam, a magnetic eld including a circularly polarized component linking at least a portion of the collector structure to cause electrons traveling substantially parallel to said beam to have a Velocity component in a direction transverse to said beam to minimizethe number of secondary electrons returned to the interaction region and increase the eflciency of the device.

11. In an electron beam and wave energy continuous interaction device including means for establishing a beam of electrons within an interaction region, a collector structure for said electrons comprising means for producing a magnetic field transverse to said beam to deiiect substantially all of the electrons in said beam and a collector electrode oriented to intercept the deliected electrons whereby substantially no electrons are returned to said interaction region from the collector.

12. In an electron beam and wave energy interaction device including means for establishing a beam of electrons within an interaction region, a collector structure for said electrons comprising a suppressor electrode, means for producing a magnetic field transverse to said beam to deflect substantially all of the electrons in the -beam which have passed the suppressor electrode and a collector electrode oriented to intercept the deflected electrons whereby the number of secondary electrons returned to the interaction region is minimized and the eiliciency of the device is enhanced.

13. In an electron beam and wave energy interaction device including means for establishing a beam of electrons within an interaction region, a collector structure for said electrons comprising a suppressor electrode, means for producing a magnetic iield transverse to the path of said beam to deect substantially all of the electrons in the beam which have passed said suppressor electrode, a first collector electrode oriented to intercept dellected electrons from said beam and a second collector electrode oriented to intercept secondary electrons emitted by said first collector.

14. In an electron beam and wave energy interaction device including means for establishing a beam of electrons along a path within an interaction region, a collector structure for said electrons comprising a suppressor electrode, means for producing a magnetic eld transverse to said beam path to deliect electrons in the beam from said path, a first collector electrode maintained at a potential lower than the potential of the suppressor electrode and oriented to intercept the deflected electrons and a second collector electrode maintained at a potential above the potential of the suppressor and oriented to collect secondary electrons from said lirst collector.

15. An electron beam and wave energy interaction dcvice including means for establishing an elongated electron beam, an electrically conductive structure for interacting withV the beam, an electrode and a collecting electrode arranged in the order` named along the electron beam path, means maintaining said iirst-named electrode at a positive direct current voltage with respect to said collector electrode and means producing a magnetic iield having a component transverse to the direction of the electron beam path at a region along said path following said electrically conductive structure to divert returning secondary electrons from the forward beam path and collect them on said first-named electrode.

16. An electron beam and wave energy interaction device including means for establishing an elongated electron beam, an electrically conductive structure surrounding the beam path for interacting with the beam, a sup pressor electrode having a dimension in the direction of said beam substantially greater than the transverse dimension of the beam and a hollow collecting electrode arranged in the order named along the electron beam path, means maintaining said suppressor electrode at a positive direct current voltage with respect to said colv lector electrode to decelerate electrons between said suppressor electrode and said collector electrode and co1- lect secondary electrons traveling from said collector electrode toward said interaction structure.

17. An electron beam and wave energy interaction device including means for establishing an elongated elec, tron beam, an electrically conductive structure for interacting with the beam, a suppressor electrode having a dimension in the direction of said beam substantially greater than the transverse dimension of said beam and a collector electrode arranged in the order named along the electron beam path, means maintaining said suppressor electrode at a positive direct current voltage with respect to said collector electrode to decelerate electrons during travel between said interaction structure and said collector electrode and means producing a magnetic lield having a component transverse to the direction of the electron beam path to aid in the collection of secondary electrons by said suppressor electrode and to minimize the number of secondaries returning along the beam path over the portion thereof adjacent said interaction structure.

18. An electron beam and wave energy interaction device including means for establishing an elongated electron beam, an electrically conductive structure for interacting with the beam, an electrode and a collecting electrode arranged in the order named along the electron beam path, means maintaining said rst-named electrode at a positive direct current voltage with respect to said collector electrode and means producing a magnetic field directed only to the beam path to focus the beam and means producing a magnetic lield having a component transverse to the direction of the electron beam path at a region along said path following said electrically conductive structure including means producing a magnetic iield substantially opposing said focusing field to divert returning secondary electrons from the forward beam path and collect them on said first-named electrode.

Llewellyn Aug. 19, 1947 Rigrod et al. Jan. 24, 1950