US2581612A - Electron discharge device of the beam deflection type - Google Patents

Description

Jan. 8, 1952 H. c. THOMPSON 2,581,612

ELECTRON DISCHARGE DEVICE OF THE BEAM DEFLECTION TYPE Filed on. 20, 1948 3 Sheets-Sheet l INVENTOR fihzzy 5 7%0/7/10/2 4 4; a l AT RNEY 2 H. c. THOMPSON 2,581,612

ELECTRON DISCHARGE DEVICE OF'THE BEAM DEFLECTION TYPE Filed Oct. 20, 1948 3 Sheets-Sheet 2 f 7 INVENTOIR TORNEY Jan. 8, 1952 ELECTRON Filed Oct. 20, 1948 N E I Q k H. c. THOMPSON 2,581,612

DISCHARGE DEVICE OF THE BEAM DEFLECTION TYPE 3 Sheets-Sheet I 3 all/var p/wai r4474};

INVENTOR TORNEY him; I)

Patented Jan. 8, 1952 UNITED .LSTATZES gRATENT OFF ICE IELECTRON "DISCHARGE DEVICE OF'THE BEAMDEFLECTION .TYPE

i-Harry C. Thompson, Chester, vt mssignor lto ltadio 'Gorporation :of America, a corporation of. Delaware Applicationflctdber 20,1948;Serial No;-55;502

(GLBIS- -IZ) ..-;21-:Glaims. 1

-My invention-relates to electron discharge dewices' and associated circuits, particularly to such devices utilizing =a beam or electrons directed toward an output electrode system,-=sa'id beam and =system having'relative-transversemovement' with respect to each other.

In prev iousdevices involving the transfer or -switching of an electron beam from inc'idenceon I one electrode to :incidence on another, the trans- I conductance -or ratio' oi-'-current change to-magnitudeofthe defiecting voltage is dependent-upon the concentration of current inthe "beam-at "the target'irom which the beamwas being deflected. -Hitherto it has been necessary-toiocus thebeam as narrowly =as possible on the target 'and to I "align the edge of the targetprecisely with respect to the mid-plane of=the beam. 'In one type of device of this kind'a two hundred m-icroampere beam has been focusedon a five *thousandths inch diameter intercepting wire from which it is "dehosted on to another'electrode. Tubes of this kind have hitherto-required high current concentrations in the beam, precise focusingthereof, and precise mechanical alignments in 'order to obtain high transoonductance. High transconductance characteristics require a deflecting -device in which precise mechanical alignments-have been required.

'In the present invention bringing the beam to a focus is not essential'to obtain maximum "possible transconductance. A parallel beam is pre- :ferred and it may'have a considerable crosssection at the region of rejection instead =0: being 'extremely'narrow as heretofore. I'he -beam is notz'divided by an aligned edge during its transfer butis .rejected as a-whole from thesurface of a target ;at :a region remote fromiin-edges. The mechanism of the rejection is entirely-novel in :principle since it occurs :abecause the component 505 electron velocity mormal'to the target surface is reduced .tozero :at the criticalxtarget potential by the previous passage :ofithe electron-through a retarding field, thereby :making :itimpossibleim the -.electron to reach "the .target surfaceat :or slightly-below-such critical potential .ot the :target.

It is known that :an :anode toward =whic'he'lectrons are normally 1directed nuts :off or :rejects theselectron flow when theraznode :isnear :zero ;or cathode potential. JIn the, present deviceasimiiar type of cut oii ;-:or::1:eiec.tion zofaelectron -iiow is made 1191066111 rat-an anode .or target q at' any desired-positive potential. To do "this the elecstron beam is made -:to approach atarge't 1 whose surface tacntely ;,inclined :to the initial beam directiomthrongh :a.retarding.zelectric rield-zwhose equipotential zsurfaces:zare parallel to theEtar-get.

"It is an 'bbiectio'f my invention 'to'zprovide an improved electron discharge device and associated circuitsp more particularly an improved device employing a beam ofelectrons which is deflected relative to an output'electrode system.

It is another object of my invention to :provide such a device whichiiis capable of "using larger currents at low voltages' than now possible with similar 'devices.

'A still further "object of my invention is to provide such a device which gives high titransconductance.

-A still fur ther object of my invention is to :provide -such-a device in whichthe 'need for --precise alignment of the electrodes-is obviated.

The novel features-which I believe to be characteri'stic of my invention-are set forth with-pardiagram showing the vprinciples .of my invention;

Fig. 3 is. amodificationofthe deviceand circuit .shown Fig. .1; .Figs. 4 t0..8, inclusive; are still ..further modifications of the electron discharge .deviceand associated circuits shown in Fig. 1; .and. Figs. .9 and .10 are graphs showing the :operating characteristics of the device undercertain conditions.

Fig. 1 shows my inventionembod-ied ina simple form inwhich the primary beam isgcollected in mart bythe-meta-llic envelopeand theou-tput is taken from the anode (or dynode). The tube @comprisesanaelongated :metallic ienvelope I in which are mounted,;,-in order, :from left to right :;:along;':thef longitudinal. :axis, :"a conventional electron gun structure composed :of :a cathode 2 iiheatedrby a heater and connected to :an aperturedzcathodezshieldi4,zan apertured accelerating and beam-clefiningzelectrode' de pair-of deflectmg-platesr on opposite sides o'f 'the'beam path,

'xand-vanoutput :electrode system comprising-an :aaperturedifield --electrode 1 andga target -or -collector electrode 78.

In accordance with my invention, the two-parallel electrodes 1 an'd ii a-re mounted in the envelope at an "acute angle to the beam path. "For zoptim-um' results, this angle is approximately the=operation-of the embodiment of Fig. 1,

the accelerating electrode 5 and electrode E are connected to a source of high potential, for example, about 300 volts, preferably by grounding the electrodes internally to the metallic envelope l and connecting the envelope to the potential source, and the target or collector 8 is connected through a tunedcircuit 9 to alower potential source, the cathode 2 being at zero potential, as shown. The deflecting plates 6 are connected to a biasing potential as shown, to provide means for adjusting the angle between the beamv and the surfaces of electrodes 1 and 8. I The operation of the device may be better understood by reference to Fig. 2 which shows on a larger scale the parallel electrodes 1 and 8 with the parallel equipotential surfaces therebetween indicated by dash lines I0. Several pathsof the electron beam B corresponding to diiferent po tentials applied to the target 8, with the field electrode 1 maintained at a constant potential, are shown by dotted lines. In its travel between the aperture of electrode 7 and the-target Beach electron has its component of velocity normal'to the target 8 reduced while its component of velocity parallel to the target surface remains un-' diminished. When the potential of the target 8 is nearly equal to that of the electrode 1, the beam is entirely collected by the target. As the target potential is reduced, the beam is deflected more and more until a critical potential is reached, for'a particular angle of inclination, electrode spacing, beam velocity and potential of electrode I, at which the beam fails entirely to reach the target, but instead, grazes the target and continues along a new beam path to a separate collector which in Fig. 1 is the tube envelope. For one tube with electrode 1 at 300 volts this critical potential was found to be about 180 volts.

At this critical or grazing target potential the current to the target is extremely sensitive to:

1. Change of initial direction of the beam by the voltage between the deflection plates (electrodes 6 in Fig 1) 2. Change of initial direction of the beam by a transverse magnetic field;

3. Change of target potential; 4. Change of potential of electrode 1; 5. Change of inclination of the target and .its

associated retarding field by mechanical means.

' changes in the target itself, as illustrated in Fig.

1; and

B. Applications which utilize the current changes of another electrode which receives the beam deflected away from the target, illustrated in Figs. 3-8, inclusive.

In class A the target musthave a secondary emission ratio greater than unity sin'cethe performance is dependent upon the existence of a reversed current from the target, that is, upon a net loss of electrons therefrom. In class B' the secondary emissivity of the targetma'y have any value without altering the performance substantially. l g

In the embodiment shown in Fig. 1, the initial direction of the beam is adjusted by the voltage on the deflecting plates 6, the inclination of electrodes 1 and 8 and the potential of electrode 1 are fixed, and the potential of the target, 8 isperiodically varied by the tuned circuit 9, producing a variable target current.

The target 8 is a good secondary emitter, or is coated with a good secondary emitting material, whereby its voltampere characteristic has a negative resistance in the cut-off region. I have observed that the negative resistanceis as low as much higher frequencies than the ordinary secfrom the target 8.

ondary emission dynatron. Electrode 1 serves as a field electrode and as a collector of secondaries The negative conductance property of thetarget at its critical potential causes circuit 9 to oscillate, which periodically varies the target potential and causes the primary beam to be deflected to and fro between the envelope and the target. Power is taken directly from the target by means of output circuit l2 coupled to circuit9.

Fig. 3 shows a modification of the device-of Fig. 1 which combines the features of classes A and B discussed above. The inclined electrode is carried by an apertured plate 13 at right angles to the beam path. The inclined target 8 parallel to electrode 1 is connected to a tuned circuit 9, as in Fig. 1. In this form, however, the output is taken from a separate electrode system positioned in the path of the deflected primary beam and including a screen grid l4 connected to electrode 1, a suppressor grid l5 connected to cathode 2 and a collector electrode l 6 connected to altuned circuit I1 coupled to an output circuit [8; The other circuit connections are the same as in Fig. 1.

In the operation of the oscillator of Fig. 3, with the target at the-critical potential, the oscillatory target potential deflects the beam toward and away from the output electrode system I4-'IB, producing a corresponding oscillatory current to the collector l6 and the output circuit. An advantage of this form over that of Fig. 1 is that the frequency of frequency-determining circuit 9 is only slightly aifected by the character of the load on the output circuit l8.

Fig. 4 shows. a means of utilizing a diverging electron beam from a cathode 2' by causing it to enter a retarding field with curved equipotential surfaces between equidistant (i. e. parallel) curved electrodes 1' and 8'. The curvature of the electrodes is such that each successive element thereof makes the same acute angle with each corresponding element of the divergent beam, so that each component of the diverging beam is retarded equally and rejected at the same potential of electrode 8. An output electrode system is shown wherein an anode I6 is surrounded by a suppressor grid l 5 and a screen grid 14.

Fig. 5 shows the tube of Fig. 3 used as an am- The potential of the target 8 is maintained at its critical potential for zero deflection of the beam, and the beam is deflected laterally by means of an alternating signal voltage applied and delivered to the output electrode I6.

to' input transformer 19 connected with deflection plates 6. Thus, the angle between the beam and the target is varied, producing'a corresponding variation in the current rejected by the target 7 In Fig. 6 the beam is deflected by a transverse magnetic field produced by a coil 20 mounted adjacent the tube in the region of the plates's,

which are here used only for adjusting the-initial .5 heamdirectiomes infigsl and Themag- .field rgmay beygenerated by a thermocouple woltage source 21,; and this arrangement is advantageous, in general foramplif ying-sources, hav- ,low impedance, because of the inherentlylow impedanceof the-input coil.

.7'.shows:a modification of Fig. employing :ae'adial beam. A cylindricalvitreous envelope ;is provided withxa-reentrant end portion or .baseifibnnwh-ich all'of theelectrodes are mountted. ..-Allof: the electrodes have-surfaces of revolution coaxial to the axis of the envelope. .An elongated ;central cathode 30,.carrying spaced cathode shields 3|, is surrounded by a pair of tubulanaccelerating electrodes. 32 and 33 spaced apart tojform. an annular slot to pass the radial .heamffromthe cathode. Twoapertured-disc deflecting plates .34 are located on each .side .of thebeam outside theaccelerating electrodes. The

"plates341are in turn surrounded by apair of :Spaced frusto-conical rings .35 and .36 --and a frustoeconical target electrode 31. The opposed .curvedsuriaces of the frusto-conical rings-35 and '35 the target 37 are equi-distant and par- :allel, :as in the other forms of :my invention. Adjacent :the upper-sides of the conical. electrodes 335 and 31 are mounted .a screen electrode :38, a

suppressor electrode 39 and a collector anode 40, .pin the form of centrally apertured planar memhers. ,Thescreen {electrode 38 is carried by a tubular member whichalso serves asa shieldfor tthe target.3l. :As shown,'the electrodes 30, 33,34

'(lower),;31, AI, 39 and are mounted directly on thebase 26, while-the electrodes .32, 34 (up- :per), and 35 are :insulatedly'mounted on the anode 40. Where necessary, the electrode sup- :porting rods -are;sealed through the .baseflt to serve .as lead-in terminals. The :circuit and method of operation .in Fig. .7 is the same as that .of E'Fig.-i5.

Fig.8 illustrates:amodification of the device of Fig.1 in which the anglelbetween the beam and the target-roan be changed, to vary the cutofi characteristic, by mechanical means accessible externally of the envelope. target ll and aperturedelectrode l are mounted in spaced parallel relation-0n an insulating block which is pivotally mounted in theenvelope on .an :axis 51 atright angles to the-plane of Fig.8. "To provide means for slightl rotating ,themov- .able assembly aboutdts pivot from outside the tube,sarod or link Elattachedto the assembly is .flexiblysealed through the envelope by-means of a tubular hellows memberill, as-shown. :Thus,

mechanical displacements'of the bellows:54 and 1 link 52 produce corresponding changes in the current tothe anode It which are :amplifiedxfor any purpose desired. The link 52-ama serve-as the potential lead for electrode "1. :Afiexibleconductor .55 is provided in "the target voltage lead.

Fig.1) shows the output currents obtained .for a :particular tube, :as-shown in 1 having a secondary emiss'ivetarget or dynode 8, asthe dynode-potential was varied from about 5.6 volts to 350 -:volts, with the potential of electrode '5 at'300Jvo'lts. The four :curves A,1-B, Cand 1D represent the resultsobtained at'four different values of deflecting :plate bias, as indicated in the legend. "Each of the largeloops of the curves represents-the net .-loss .ofsecondaries from :the I dynode 8. The-abrupt fall of current as the potential of the'dynode is decreased rtoward 1200 volts in -curve D is caused by the turning away of the primary electron beam from the 'dynode until it is no longer incidentthereon :and no In this .tube the x;

lon er produces secondaries thereirom. At 300 volts the prima y urren is about equa "t th reverse gsecondaryrcurrent, producing a --zero current in the dynode lead.

Fig. 1-0 shows the variation in 'dynode current when'the deflecting plate biaswas varied-with 250 volts-on-the dynode 8;and v300 voltson electrode 1. The points A, B, C and D correspond to the -four curves of Fig. ,9.

.As stated above. the best results are produced when :theangle between the surfaces of electrodes l and 8 and the beam axis isabout 30. Thisangle is, not critical andmay be'madegsomewhat-greater or less than 30. However, if the angle ,is made more acute (smaller), the useful operating range of potentials of the target is decrease :;because of the efi'ectiveness of a given change in target potential is greater. If the angle is made less acute (larger), the concentration of current at the region of impact is higheigand the emission of secondaries is smaller, in the case of a secondary emission target and thersensitivity of the device to changes in target potentialor inclination is reduced.

In my co-pending application entitled fElectron Discharge Devices of the Beam Deflection Type, Serial No. 55,501, filed concurrently herewith, now U. S..P,atent -No. 2,559,524, granted July'3, '1951, 'I-have disclosed and claimed an electrode mount assembly for a beam deflection tube with an electron multiplier output system, which assembly may be used in the discharge .deyices illustrated schematically in Figures 1 through 6and8 of the instant application.

While I have indicated several specific-embodiments of myinventiom-it will be understood that my invention is by no means limited to the exact .formsillustrated or useindicated, :but that many variations may be made in the particular structure used andithepurposes for which it is'employed'Wit-hout departing from the scope of the invention as set forth in the appended claims.

I claim:

1. An electron discharge device comprising electronv gun means for supplying and directing abeam of electrons along a beam path, and elecacute angle to'thebeam path and at least apart of -.saidb.eam is deflected by said'field away from said first collector electrode, and a second col- ;.1B.C.t01 electrode insulated fromthe other electrodes-and located beyond said first collector and field'electrodes inposition to receive-electrons of said beam deflected from said first collector electrode.

2. An electron discharge device according to claim ,1, including means for adjusting the poten- ;.t-ia=ls;applied to-said first collectorand-fieldelectrodes to causesaid beam to graze the surface of said first collector electrode.

.3.,;A-n [electron discharge "device cflmprising ielectronagun .smeans for supplying-and directing beam of. electrons salons: aikbeamr path, and electrode means including a first collectorcelectrode having a surface extending across said beam path at an acute angle thereto, a field electrode positioned adjacent said first collector electrode and having a surface facing and parallel to said surface of said first collector electrode, means for applying a positive potential to said field electrode, means for applying a substantially lower positive potential to said first collector electrode, whereby during operation of said device said beam traverses a retarding electric field having parallel equipotential surfaces extending at said acute angle to the beam path and at least a part of said beam is deflected by said field away from said first collector electrode, a second collector electrode insulated from the other electrodes and located beyond said first collector andfield electrodes in position to receive electrons of said beam deflected from said first collector electrode, and means for periodically varying the potential of one of said first collector and field electrodes to cause said beam to be periodically shifted between said two collector electrodes.

4. An electron discharge device comprising electron gun means for supplying and directing a beam of electrons along a beam path, and electrode means including a first collector electrode having a surface extending across said beam path at an acute angle thereto, a field electrode positioned adjacent said first collector electrode and having a surface facing and parallel to said surface of said first collector electrode, means for applying a positive potential to said field electrode, means for applying a substantially lower positive potential to said first collector electrode, whereby during operation of said device said beam traverses a retarding electric field having parallel equipotential surfaces extending at said acute angle to the beam path and at least a part of said beam is deflected by said field away from said first collector electrode, a second collector electrode insulated from the other electrodes and located beyond said first collector and field electrodes in position to receive electrons of said beam deflected from said first collector electrode, and means for adjusting the acute angle between said beam path and said first collector electrode to cause said beam to graze the surface of said electrode.

5. An electron discharge device comprising electron gun means for supplying and directing a beam of electrons along a beam path, and electrode means including a first collector electrode having a surface extending across said beam path at an acute angle thereto, a field electrode positioned adjacent said first collector electrode and having a surface facing and parallel to said surface of said first collector electrode, means for applying a positive potential to said field electrode, means for applying a substantially lower positive potential to said first collector electrode, whereby during operation of said device said beam traverses a retarding electric field having parallel equipotential surfaces extending at said acute angle to the beam path and at least a part of said beam is deflected by said field away from said first collector electrode, a second collector electrode insulated from the other electrodes and located beyond said first collector and field electrodes in position to receive electrons of said beam deflected from said first collector electrode, and means for periodically varying the acute angle between said beam path and said first collector electrode to cause said beam to be periodically shifted between said two collector electrodes.

6. An electron discharge device having electron gun means for supplying and directing an electron beam along a beam path, a first deflector electrode having a surface extending across said beam path at an acute angle thereto, a second electrode adjacent said first electrode and having a surface facing and parallel to said surface of the first electrode, a collector electrode insulated from the other electrodes and located beyond said first and second electrodes in position to receive electrons deflected from said first electrode, and other deflecting electrodes positioned on opposite sides of the beam path and between said electron gun means and said first and second electrodes.

7. An electron discharge device including electron gun means for supplying and directing a beam of electrons along a beam path, a deflector electrode in the path of said beam and having a surface extending across said beam path at an acute angle thereto, a second electrode positioned adjacent said deflector electrode and having a surface facing and parallel to said surface of the deflector electrode and having an aperture registerlng with the beam path, and a collector electrode insulated from the other electrodes and located beyond said electrodes in position to receive electrons deflected from said deflector electrode.

8. An electron discharge device including electron gun means for supplying and directing a beam of electrons along a beam path, a pair of oppositely disposed electrodes on opposite sides of said beam path, a third electrode in the Path of said beam of electrons and having a surface extending across said path at an acute angle thereto, and a fourth electrode positioned adjacent said third electrode and having a surface facing and parallel to said surface of the third electrode and having an aperture registering with the beam path, and a collector electrode insulated from the other electrodes and located beyond said third and fourth electrodes in position to receive electrons deflected from said third electrode.

9. An electron discharge device having electron gun means for supplying and directing an electron beam along a beam path, a first electrode in the path of said beam having a surface extending across said beam path at an acute angle thereto, a second electrode adjacent said first electrode and having a surface facing and parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second electrodes in position to' receive electrons deflected from said first electrode and comprising, in order, a screen electrode, a suppressor electrode and a collector electrode.

10. An electron discharge device having elec tron gun means for supplying and directing an electron beam along a beam path, a first electrode in the path of said beam having a surface extending across said beam path at an acute angle thereto, a second electrode adjacent said firstelectrode and having an aperture through which the beam path lies, said second electrode having a surface facing and parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second electrodes in position to receive electrons deflected from said first electrode and comprising, in order, a screen electrode, a suppressor electrode and a collector electrode.

11. An electron discharge device having electron gun means for supplying and directing anthrough which the beam path lies, said secondelectrode having a surface facing and parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second elec trodes in position to receive electrons deflected from said first electrode and comprising, in order,

a screen electrode, a supp es or electrode and a collector electrode, and deflecting electrodes positioned on oppositesides of the'beam path and between said electron gun means and said first and second electrodes. v

12. An electron discharge device including electron gun means for supplying a' beam of elec=- trons along a beam path, a first electrode in.

the path of said beam of electrons and having a secondary-eniissiV surface extending across said beam path at an acute angle thereto, a second electrode positioned between said elec tron gun means and said-first electrode and having a surface facing and parallel to said secondary emissive surface and having an aperture registering with the beampath, a collector electrode insulated from the other electrodes and located beyond said electrodes in position toreceive deflected electrons of said beam upon the application of deflecting voltages to said first and second electrodes, means including an oscillating circuit for applying alternating voltages to said first electrode, output means connected to said collector electrode, and means for applying positive voltages to said collector electrode and said second electrode and a substantially lower positive voltage to said first electrode.

13. An electron discharge device having an electron gun means for supplying, forming and directing an electron beam consisting of diverging elements, a first electrode having a curved surface extending across said beam path so that each successive element of said curved surface makes the same acute angle with each corresponding element of said diverging beam directed thereat, a second electrode adjacent said first electrode and having a curved surface facing and parallel to said curved surface of said first electrode, and a collector electrode insulated from the other electrodes and located beyond said first and second electrodes in position to receive electrons deflected from said first electrode.

14. An electron discharge device having electron gun means for supplying and directing an electron beam along a beam path, a first electrode in the path of said beam having a plane surface extending-across said beam path at an acute angle thereto, a second electrode adjacent said first electrode and having an aperture through which the beam path lies, said second electrode having a surface parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second electrodes in position to receive electrons deflected from said first electrode and comprising, in order, a screen electrode, a suppressor electrode and a collector electrode, and means for deflecting said beam including means for generating a magnetic field transverse to the beam path.

15. An electron discharge device having electron gun means for supplying and directing an electron-beam along a beam path, aflrs't electrode 111 the path or said 'beam hav-ing' spran surface extending across said beam path at an acute angle thereto,- a sec'ond electrode adjacent said first electrode and having an aperture through which the beam path lies, said s'econd elec'trode' having a surface facing and parallel 'to the sur: face of the-firstelectrode,and an electrode sy'sf teminsulated: from the other electrodes aricllo cate'd beyond said first and secondelectrodes in position to receive electrons deflected from said first electrode and comprising, in order,a scr"een electrode, a su pressor electrode and acollector electrode, deflecting electrodes positioned on: 015 pos'ite' sides of thebeam path and" between saidelectr'ongun means and said first and "second electrodes and nieans responsive totemperature conditions for deflecting said team including? means for generating a maghetic"field trans verse to the beam path in the 'region o'f said deflecting electrodes.

16'. An electron discharge device including a cathode, a first electrode surrounding said cathode and having a'n' annular aperture extending therethrough, oppositely disposed ring-like mem bers lying in parallel planes extending" tra'n's versely through said cathode adjacent the edges of said annular aperture, acone-shaped secondelectrode surrounding said first electrode and having anannular aperture registeringwith the annular aperture in said fir stelectrc'de, another cone shap'ed electrode surrounding" said "second: electrode, a flat platelike collector electrode ex tending tra sv rsely aid cathode and adj ace'iit said 'ccne -sh'aped electrodes, and plate like screen and suppressor electrodes positioned between said plate-like collector electrode and said coneshaped electrodes and disposed parallel to said collector electrode.

17. An electron discharge device having electron gun means for supplying and directing an electron beam along a beam path, a first electrode in the path of said beam having a plane surface extending across said beam path at an acute angle thereto, a second electrode closely adjacent said first electrode and having an aperture through which the beam path lies, said second electrode having a surface facing and parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second electrodes in position to receive electrons deflected from said first electrode and comprising, in order, a screen electrode, a suppressor electrode and a collector, said first and second electrodes being pivotally mounted, and means for rotating said first and second electrodes about said pivot to vary said acute angle.

18. An electron discharge device having an envelope containing electron gun means for supplying and directing an electron beam along a beam path, a first electrode in the path of said beam having a plane surface extending across said beam path at an acute angle thereto, a second electrode closely adjacent said first electrode and having an aperture through which the beam path lies, said second electrode having a surface facing and parallel to the surface of the first electrode, and an electrode system insulated from the other electrodes and located beyond said first and second electrodes and comprising, in order, a screen electrode in position to receive electrons deflected from said first electrode, a suppressor electrode and a collector, said first and second electrodes being pivotally mounted as a unit in said envelope, and externally-operable means for' rotating said unit about its pivot to vary said acute angle comprising a flexible member forming a portion of said envelope and a mechanical link within said envelope connecting said unit to said flexible portion.

19. An electron discharge device comprising electron gun means for supplying and directing a beam of electrons along a beam path, and electrode means including a first collector electrode having a surface extending across said beam path at an acute angle thereto, a field electrode positioned adjacent said first collector electrode and having a surface facing and parallel to said surface of said first collector electrode, means for applying a positive potentialto said field electrode, means for applying a substantially lower positive potential to said first collector electrode, whereby during operation of said device said beam traverses a retarding electric field having parallel equipotential surfaces extending at said acute angle to the beam path and at least a part of said beam is deflected by said field away from said first collector-electrode, a second collector electrode insulated from the other electrodes and located beyond said first collector and field electrodes in position to receive electrons of said beam deflected from said first collector electrode, and means for changing the acute angle between said beam path and said first collector electrode to change the proportion of said beam which is deflected away from said first collector electrode.

20. An electron discharge device including electron gun means for supplying and directing a 12 beam of electrons along a beam path, a, deflector electrode in the path of said beam and having a surface extending across said beam path at an acute angle thereto, a second electrode positioned adjacent said deflector electrode and having a surface facing and parallel to said surface of the deflector electrode, and a collector electrode insulated from the other electrodes andlocated beyond said electrodes in position to receive electrons deflected from said deflector electrode.

21. An electron discharge device according to claim 20, further including means located between said electron gun means and said deflector electrode for deflecting the beam relative to said deflector electrode.

HARRY C. THOMPSON.

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

UNITED STATES PATENTS

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