US2160796A

US2160796A - Electron discharge apparatus

Info

Publication number: US2160796A
Application number: US111808A
Authority: US
Inventors: Gordon K Teal
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1936-11-20
Filing date: 1936-11-20
Publication date: 1939-05-30
Anticipated expiration: 1956-05-30
Also published as: US2160798A; GB521077A; GB500447A; FR49655E; FR824648A; FR49980E; DE886343C; GB500448A; US2236041A; US2245605A; CH214485A; NL49799C; GB500170A; US2160797A; CH208067A; GB505663A; US2134718A; US2160799A; BE431298A; GB502528A

Description

May 30, 1939. T 2,160,796

ELECTRON D1 5 CHARGE APPARATUS Filed Nov. 20, 1956 3 Sheets-Sheet 1 gym/70R By TEAL 0 m 6.14mi

A TTORNEY May 30, 1939. TEAL 2,160,796

ELECTRON DISCHARGE APPARATUS Filed Nov. 20, 1936 3 Sheets-Sheet'Z FIG 7 W225?" INVENTOR By GK TEAL ATTORNEY May 30, 1939. G. KJTEAL ELECTRON DISCHARGE APPARATUS Filed Nov. 20, 1936 5 Sheets-Sheet 3 lNVENTOR GK TEAL v A TTORNEV Patented May 30, 1939 UNITED STATES PATENT OFFICE Bell Telephone Laboratories,

Incorporated,

New York,"N. Y.,. acorporation of New York Application November 20, 1936, .Serial .No.. 111,808

' 11 claims. (01150-166 in the 'device,.are directed to and impinge upon This-invention relates to; electron discharge apparatus and more particularly tosuchtapparatus adapted to amplify high. frequency impulsesaand including electron. discharge devices having secondary electron emitting electrodes.

Oneobject of this invention is torenable. the economic, efficient and facile attainment: oflarge and high .fi'delity amplificationof high frequency impulses.

Another object of this invention is to enable the accurate determinationoi the characteristics of amplifiersutilizing electron discharge devices.

Another object of this invention is to obtain) a high. signal to "noise ratio in electronie'amplifiers.

Still anotherobject of this; invention is to simplify the structure of multi-stage electron discharge apparatus and to reduce the number-of component parts thereof requisite to produces; high degree of amplification. I

Aiurther object of this invention is to expedite the fabrication of electron discharge devicesthaving; a. multiplicity of electrodes;

In one illustrative embodiment of? this invention, electron discharge apparatus comprises anv electron discharge device including a primary cathode, a collector electrode or anode, and a plurality of auxiliary or secondary cathodes disposed between the primary cathode and'the'collector electrode. The variouscathodes may be channel shaped, disposed-edge to edge and in alignment andhave one, preferably the inner, surface, or both surfaces, thereoi'coat'ed-with a material capable of producing copious emission of electrones:

Each rof the 'secondary cathodes is operated at emitting surface thereof, the electrons emitted,

thereby are directed. to and impinge upon the first of the. secondary cathodes, under the influence of the magnetic field and the potential. upon this secondary cathode. As a result, secondary electrons are releasedfrom the first secondary cathode and these electrons under the influence of the magnetic and'electro-staticfields: extant the next secondary cathode to cause the release of secondary electrons therefrom. This action is. repeated. to the: last secondary cathode, that is, the one furthest removed from the primary cathode, and the electrons:releasedtherefrom are attracted to the collector electrode or anode and constitute an available output current for a utilization circuit connected, for example, to the pri-- mary cathode and the collector electrode.

Inasmuch as the several secondary cathodes have suriaces'coated witha material having good secondary electron emitting properties, each primary or secondary electron impinging thereon will cause the. release of a plurality of secondary electrons. Hence, alargc electron multiplication occurs between the primary cathode and the collector electrode so that in: effect: the signal corresponding to the activating source for the primary-cathode is greatly amplified as represented by the. electron flow to. the collector electrode-or anode. Variations in the intensity of the activating source will result in corresponding variations-in-theelectron current to the collector electrode. or anodeandhence in the output current of the device.

The invention and the. various: featuresthereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawings, in which Fig. 1 is a view in; perspective of electron dis charge apparatus illustrative.- of. one embodiment of this invention, a portion of the enclosing vessel of the electron discharge device being broken away to show the. internal structure more clearly;

Fig. 2 is a top view, partly"incross-section, of the apparatus shown in Fig. 1, the magnet being modified to show another formthereof;

Fig. 3 is anenlarged, partly exploded detail View in perspective illustrating. structuraldet'ails of the electron discharge device shown in Fig..l; Fig.4 is an elevational View in perspective of an electron discharge device illustrative oi another embodiment of this invention;

Fig. 5 is a view'in cross-section of the cathode structure of the device'shown in Fig. 4;

Fig. 6'is' an enlarged; detail View in perspective and partly exploded illustrating the association of the cathodes and the supports therefor in the device shown in Fig. 4; and:

Fig. 7 isa circuit diagram of space discharge apparatus constructed in accordance with this invention.

Referring. now to the drawings, the apparatus shown in Fig. 1 includes an electron discharge device comprising an elongated cylindrical enclosing vessel 10 having a stem II at one end provided with an intermediate, integral annular flange l2. A unitary electrode assembly is mounted upon the stem H and includes a primary cathode [3, a collector electrode or anode [4, a screen or shield electrode l5 and a plurality of auxiliary or secondary cathodes IE to I6 inclusive.

The several electrodes are mounted upon a supporting structure comprising a split metallic band or collar I! clamped about the stem II, a plurality, for example four, of rigid supports 18 extending from the band or collar l1, and a pair of grooved or channel shaped cross-pieces l9 afiixed to the supports I8. Each of the crosspieces [9 clamps and securely holds an elongated insulating member or upright 20, for example a strip of mica, having a plurality of fingers 2|. The insulating members 20 preferably are mounted parallel to each other and are maintained in proper spaced relation by cross-members or braces 22, which also may be strips of mica, having slots in which the insulating members are frictionally fitted.

As shown more clearly in Figs. 2 and 3, each of the cathodes is channel shaped, for example in the form of a rectangulated U, and the sides or arms 23 thereof are bent about and grasp corresponding of the fingers 2| on the insulating uprights 23. The arms 23 may be indented as indicated at 24 to lock the cathodes to the uprights 20. Each cathode has secured thereto a metallic clip 25, which serves as a terminal lug to which a leading-in conductor may be afiixed. As indicated at 2'6, the clips 25 may be indented to lock them to the arms 23 of the cathodes. The primary and secondary or auxiliary cathodes are mounted in alignment with corresponding surfaces thereof in common planes. The spacing between juxtaposed edges of the cathodes may be of the order of inch.

The several cathodes may be formed of strips of silver or copper having portions thereof, preferably only the surface .of the portion between the arms 23, treated to render them capable of copious electron emission. For example, these portions may be oxidized, as by a high potential discharge, and treated with caesium to provide a coating or surface containing caesium oxide, silver and some free caesium.

The anode or collector electrode I 4, as shown clearly in Fig. 3, is of the same form as the cathodes and has its arms 21 bent around and locked to the insulating uprights 20, one of the arms having afiixed thereto a terminal clip 28 similar to the clips 25. The base of the anode preferably is disposed parallel to the bases of the cathodes and slightly displaced from the common plane thereof.

The shield or screen electrode I 5 includes a fiat relatively coarse mesh portion supported by metallic clips 29 grasping the uprights 20 and locked thereto by indentations 30. Preferably the mesh portion is of substantially the same area as the base of the anode or collector electrode l4 and is disposed substantially coplanar with the bases of the primary and secondary cathodes.

Disposed about the stem end of the enclosing vessel and frictionally mounted thereon is an insulating base 3| which carries a plurality of terminal members 32, one for each of the electrodes of the device. Leading-in conductors 33 are connected to the terminal members 32, extend inwardly of the stem II, and are sealed in uniform space relation in the annular flange l2. Suitable conductors 34 are affixed at one end to the projecting ends of the leading-in conductors 33 and at the other end to the

clips

25, 28 and 29 on the cathodes, anode and screen electrode, respectively. Preferably all but the ends of the conductors 34 are encased in insulating material, such for example, as glass sleeves 35.

The electron discharge device heretofore described may be mounted on a carrier which includes a rigid L-shaped support 36 and resilient bowed arms 31 mounted on the support 36 and adapted to grasp the enclosing vessel Ill. The lower arm of the support 36 is fitted slidably in a track or groove 38 in a suitable base 39 and has afiixed thereto a finger piece or bracket 49, which is pivoted at one end on the base 39 as by a screw 4|.

Mounted upon the base 39, as by bolts 42, is a permanent magnet structure which may be composed of a plurality of strongly magnetized horseshoe magnets 43. The several magnets may be clamped together between brackets 44 drawn toward each other by a wing nut 45 and spring 46 mounted on a bolt 41 extending from the base 39.

The magnet structure produces an intense magnetic field at substantially right angles to the longitudinal axis of the electron discharge device and substantially parallel to the bases of the cathodes l3 and I6 and immediately adjacent the electron emitting surfaces thereof. The position of the device relative to the magnet may be adjusted by means of the finger piece 40 so that the emitting surfaces of the cathodes are in the strongest or most intense portion of the magnetic field. In order to obtain sharper focussing of the electron streams, the magnet may have its poles so related that a curved magnetic field is produced adjacent the electrodes. For example, the poles may have chamfered faces as shown in Fig. 2. Also, as described more fully in the copending application of William A. Knoop, Serial No. 111,796, filed November 20, 1936, the magnet may be so constructed that the magnetic field is of greatest intensity in the vicinity of the primary cathode and decreases uniformly in intensity to in the vicinity of the collector electrode. As shown in Fig. 1, the magnet preferably extends somewhat above the anode !4 and slightly beyond the primary cathode I3.

During operation of the apparatus, the secondary cathodes T6 are operated at positive potentials with respect to the primary cathode, the potential upon each secondary cathode being higher than that upon the next preceding one with reference to the primary cathode. For example, the first secondary cathode I6 may be operated at of the order of 135 volts positive with respect to the primary cathode l3, the secondary cathode 16 at of the order of 270 volts positive, and each succeeding secondary cathode at of the order of 135 volts positive higher than the next preceding one so that the secondary cathode I6 is of the order of 1080 volts positive with respect to the cathode l3. The shield or screen electrode l5 may be operated at a potential of the order of 135 volts positive with respect to the secondary cathode Hi and the collector electrode or anode I4 may be operated at a potential of the order of 250 volts positive with respect to the secondary cathode I6 As shown in Fig. 7, the potentials for a number of the secondary cathodes l6 may be obtained from a potentiometer 41, which may be supplied from a suitable source such as a rectiher 48. Because of the heavycurrent drain, the potentials: for r the secondary cathodes, for' exam:- pied-G and 16 and'for the; screen; 15 andi-vanode or: collector: electrode k4: preferably are obtained fromseparate-sources such-as-batteries 50 cone nectedin series as shown.

The-primary cathode l=3-may-beenergized by a beam of:lightrfoc.ussed:upon the activated portion' thereof through a lens. 51: andv emanating fromwa=suitable= source, such as-a lamp '52, the intensity 4 of: the light beam being variable" as by a suitable film 60. Under the-=influence of-such awlight: beam,: the primarycathode I 3 emitsielectrons-"and-theseelectrons, underzthe influence of the: magnetic-field. in: the vicinity of the cathode I 3 and the electrostatic fields obtainingbecause of the positive potentials upon-the other electrodes oh the device, areattracted to: and: impinge upon. the secondary :or auxiliary cathode I 6 The velocity of these impinging electrons is relatively high.- so that: secondary electrons: are .released :from %the activated or coated portion: of the-cathode Hi Theintensity of 'thissecondary electron :emission will 'be dependent primarily upon the character of the coating ,upo-n. the'cathode 1'6 and. the potentiakof this cathode with respectto theprimary cathode. For example, if the emitting surface be of: caesium treated silver oxide, 'as :heretofore described, and the cathode I6 be operated at a potential of the order of 135 volts'positive withrespect to'thecathode .Ii3, the secondary GIGGETOI'L': stream from the cathode IE willbe approximately 3 to 7 times as great 'as the, primary 'electronsemanating from the primary cathode 1 3-.v Ineffect, therefore, the'primaryrelectron stream is multipliedand as aresult an amplification! of the signal: corresponding to the light beam energizing theiprimary -cathode obtains.

The secondary electrons emanating from the cathode- $6 under theiinfiuence. of: the magnetic and the electrostaticfields extant adjacent this cathode, are directed towardandtimpinge upon the-secondary cathode 1 6 These electrons :are adsorbed bythe/cathode:tii 'and produce 'a'copious: emission-of other-secondary'electronsfrom' this cathode. Foreach; electron impinging upon the-cathode M6 aplurality-of secondary electrons-are released therefrom-so that effectively a The secondary electrons emanating from the cathode i are directed to and adsorbed by the anode or collector electrode l4 and constitute the output current of the device. This current may be employed in any suitable utilization circuit associated with the anode or collector as shown in Fig. 7.

The shield electrode l5 serves to screen the end cathode Hi from the anode or collector electrode l4 and thereby presents undesired reaction of variations in the anode or collector potential upon the cathode l6 and hence minimizes distortion in the output current of the device.

Itih-as been found-thatthe operating characteristics of the device, principally the relation between theoutput current and the-=intensity of the light beam energizing the cathode I3, are materially dependent uponv the design of thesecondary cathodesdit. For mostpurposesiit isdesirable that the output current-lightzbeam.intensitycharacteristic be substantiallylinear throughout the output current range correspondingto the'range of. intensitiesof'the light beam'played upon the primary cathode 13. This desirable relationship may be obtained by making the width of the secondarycathodes l-6 approximately 5 times-the depth thereof and the longer dimension approximately twice the shorter dimension. For example, it has been found that if the secondary cathodes are approximately 1.2 centimeters by approximately 0.6 centimeter and 0.25 centimeter deepwand are spaced-of the order of 0.1 25-rcentimeter, .the output current will: vary substantially linearly with .the intensity of the light beamover arrange f.rom.-substanti-ally zero toatleastldmilliamperes. If non-linear char acteristics-aredesired, they -.may be-obtained by increasing the depth of the secondary cathodes.

It maybe pointersloutalso that the channel shaped form-of the severalcathodes results in reduction of thelateral dispersion "of the pri mary andusecondary' electron. streams,,-so that concentrated electron beams obtain and a high operating. efficiency results.

This desirable concentration of the electron beams may beenhanced'by disposing the'secondary cathodes 16 anduthe primary cathode 1 i3 at asmall angle, for example of the order of. twenty degrees, to the-:longitudinal axis of the electrode structure-as shown'in'Figs. 4; 5 and 6-. The electronidischarge device shown in these figuresis substantiallythesame as that'show-n in Fig. 1', except that the cathodes-|=3 and 16- are tilted and-the fingersdl: on-the-insulating membersillare .provided with edges '53? sloping -at'the same angle as the cathodes. Thedevice 'may be mounted in. the samemanner as. the device shown in Fig. 1 and connected in a'circuitsuch as shown inEig. '7.

Although specificembodiments of this invention havebeensshown'and described, it will: be understood, of course, that these embodiments are merely-illustrative ofthis invention and'that various modifications, may be made'therein. For example, although eight secondary cathodesare shown in the-deviceof Fig. 1 and nine in=the device shown inrFig. 4, a greater or lesser number may be employed. Furthermore, although the primary cathodes i3 are disclosed as of the photoelectric type they may be of othertypes, for example, thermionic, directly or indirectly heatectand a separate grid or control electrode maybe utilized .for modulating the primaryelectron;str.eam1f-rom the primary cathode l3 to. the first secondary cathode'tfi in: accordance withva signal to be amplified. Moreover, in modifications of the embodiments heretofore described, the anode or collector electrode l4 may be disposed with its electron receiving surface at substantially right angles to the axis of alignment of the cathodes and both surfaces of the primary and secondary cathodes may be provided with a layer or coating of electron emitting materials. Similarly, the shield or screen electrode l5 may be disposed at right angles to the axis of alignment of the cathodes. Two screen electrodes may be provided adjacent opposite surfaces of the anode or collector electrode l4 when both surfaces of the cathodes are sensitized and the anode or collector electrode is substantially parallel to the cathodes. Other modifications may occur to those skilled in the art without, however, departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. Electron discharge apparatus comprising a primary cathode, a collector electrode, a plurality of secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having electron focussing flanges electrically connected thereto and forming channels constituting a path for the electron streams, and mounted end to end and in alignment with one another, and a coating of electron emissive material upon the inner surface of said channels.

2. Electron discharge apparatus comprising an enclosing vessel, a pair of insulating uprights mounted in said vessel, a primary cathode, a collector electrode, a plurality of secondary cathodes disposed between said primary cathode and said collector electrode and in alignment with one another, and having electron focussing flanges electrically connected thereto and forming channels constituting a path for the electron streams, said flanges bent about and grasping said uprights, and an electron emissive coating upon the inner surface of said channels.

3. Electron discharge apparatus comprising a primary cathode, a collector electrode and a plurality of aligned secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having electron focussing arms electrically connected thereto and parallel to the axis of alignment of said secondary cathodes forming channels of a depth less than the width thereof, the width being determined by the spacing of said arms, said channels constituting a path for the electron streams, and the inner surface of said channels having thereon a coating of electron emissive material.

4. Electron discharge apparatus comprising a primary cathode, a collector electrode, and a plurality of secondary cathodes disposed between said primary cathode and said collector electrode, and metallic means electrically integral with said secondary cathodes and at opposite sides thereof for laterally confining the electron streams from said primary and secondary cathodes.

5. Electron discharge apparatus comprising a primary cathode, a collector electrode, and a plurality of auxiliary electrodes between said cathode and said collector electrode, said auxiliary electrodes having secondary electron emitting portions in alignment with one another and said cathode. and having integral portions on opposite sides of the axis of alignment of said emitting portions for laterally confining the electron streams emanating from said primary cathode and said portions to aligned paths.

6. Electron discharge apparatus comprising a primary cathode having a plane emitting portion, a collector electrode, a plurality of secondary cathodes between said primary cathode and said collector electrode having electron emitting portions disposed edge to edge and substantially coplanar with said plane emitting portion and in alignment therewith, and members at opposite sides of said emitting portions and electrically integral therewith for laterally confining the electrons emanating from said emitting portions to restricted paths.

'7. An electron multiplier comprising a primary cathode, a collector electrode, and a plurality of similar, equally spaced, successively mounted secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having channel-shaped emissive portions, the inner surface of which is electron emissive.

8. Electron discharge apparatus comprising a primary cathode, a collector electrode, and a secondary cathode between said primary cathode and said collector electrode and in alignment therewith, said secondary cathode having electron focussing flanges electrically connected thereto forming a channel constituting a path for the electron stream, the inner surface of said channel being exposed and secondary electron emissive.

9. Electron discharge apparatus comprising a primary cathode, a collector electrode, a plurality of secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having channel-shaped portions disposed edge to edge and with corresponding surfaces thereof substantially coplanar, the inner surfaces of said portions being exposed, and a secondary electron emissive coating upon said inner surfaces.

10. Electron discharge apparatus comprising a primary cathode, a collector electrode, a plurality of secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having rectangulated U-shaped portions disposed edge to edge and with corresponding surfaces thereof in common planes, the inner surfaces of said portions being exposed, and

a secondary electron emissive coating upon said inner surfaces.

11. Electron discharge apparatus comprising a primary cathode, a collector electrode, and a plurality of substantially rectangulated U-shaped secondary cathodes between said primary cathode and said collector electrode, said secondary cathodes having their inner surfaces exposed and adapted to emit secondary electrons, and. the arms of each of said secondary cathodes being spaced from each other a distance greater than the dimension of said arms at right angles to the bases of said secondary cathodes.

GORDON K. TEAL.