Патент USA US2074829код для вставки
March 23, 1937. 2,074,829 Y J. M. CAGE ELECTRON BEAM TUBE Filed June 21, 1955 b UH, .Jwm WMnCmc?r m FM.9.a Patented Mar. 23, 17937 UNITED STATES PATENT OFFICE 2,074,829 ELECTRON BEAM TUBE ' John M. Cage, Schenectady, N. Y., assignor to General Electric Company, a corporation of . New York Application June 21, 1933, Serial No. 676,875 13 Claims. (Cl. 250-27 ) The present invention relates to electron dis ance with my invention, it becomes possible en charge devices, more particularly to those de tirely to eliminate the usual focusing member vices which utilize a beam of electrons de?ected surrounding the cathode and to rely entirely upon electrostatically within the tube. the focusing effect offered by the de?ecting mem 5. Tubes of this character usually employ a source of electrons together with a focusing arrange ment, an anode for receiving the electrons which is charged positively with respect to the electron source, and an intermediately positioned elec w trode for moving the electron beam over the face of the anode or other electron-receiving member. The focusing device may take the form of a hol low cylinder surrounding the source of electrons and is provided with a cutaway portion or slit 1;, through which the electrons move on their way to the anode. In the design of these prior art tubes, it was considered necessary to perform all of the focus ing action at a position as close to the cathode as possible rather than at any other position on the _ 20 theory that, if the electrons are once focused or constrained to a beam of proper shape, they will remain in this constrained condition throughout their travel toward the anode. However, it was subsequently found that notwithstanding their 25 initial focussed condition, the electrons tend to spread or disperse when the beam is electrostat bers, thus permitting the elimination of a mem ber heretofore considered essential, although it > is preferred to employ the usual form of focusing electrode in addition to the combined focusing and deflecting members. An object of the present invention is to improve the operation of/beam tubes and, in particular, to improve the focus of the beam so that the latter will maintain a highly concentrated form as it sweeps across the electron receiving surface. The manner in which this object is carried out and the invention, itself, will be apparent from the following description when perused in con nection with the accompanying drawing in which Fig. 1 is an elevational view of anelectron beam tube improved in accordance with the present in- . vention; Fig. 2 is a diagrammatic view of the tube shown in Fig. 1 and connected in an elec trical system for ampli?cation purposes; while Fig. 3 shows in diagram, a modi?ed form of elec tron beam tube utilizing a ?uorescent screen and 25 connected in suitable circuits. . Referring more particularly to Fig. 1, numeral ically de?ected across the tube and a considerable I designates an envelope which may be either‘ distortion is introduced into the translating prop highly evacuated or contain a small amount of erties of the tube. According to the prior art gas, the envelope terminating at the bottom, as 30 teachings, the cylindrical member, which sur shown, in a reentrant stem 2 and a four-pillar rounds the cathode, was vested solely with the ' press 3. The envelope is of the “tipless” type, focusing function and, for this purpose, was hence, an evacuating tubulation 4, which commu charged negatively with respect to the cathode. nicates with the interior of the envelope, is pro In these tubes, the remaining electrodes, includ vided within the stem 2. As will be seen from the 35 ing the de?ecting members, were either so biased drawing, the entire electrode structure is sup with respect to the cathode or else were entirely ported in a symmetrical manner entirely from disconnected therefrom so as to preclude‘ any the press 3. This structure includes an indirectly concentrating e?ect on the moving electrons. heated cathode 5, seen morev clearly in Figs. 2 Contrary to the accepted principles of design of and 3, containing a ?lamentary heater 6, prefer 40 40 the prior art tubes, I have discovered that, when ably of tungsten. The cathode conveniently the de?ecting members are connect-ed to the takes a form of an elongated cylinder and is pref cathode through a biasing battery of suitable erabiy coated with electron-emitting material, polarity and potential, they perform not only such as alkaline earth oxide. concentrically their usual function of sweeping the electron surrounding the cathode, there is a cylindrical beam across the tube but, in addition, effectively member ‘I, also of elongated form which is pro serve to ,focus the electrons and thus assist in maintaining the original concentrated shape of the beam during its transverse excursions. Thus, an additional focusing effect is introduced into the tube at a position intermediate the cathode and anode, which is exercised simultaneously with vided with a narrow slit 8 for the egress of elec trons on their way to electron-receiving members described ‘hereinafter. There is an electrode 9 positioned in proximity to the slit 8 for the pur pose of accelerating the electrons. This electron the de?ecting action, serving to eliminate the‘ accelerating member is preferably constituted of two angular pieces of elongated'form which are normal tendency of the electrons to disperse or 55 spread before they reachthe anode. In accord joined together only at their ends by metal straps It so that the longer legs of the angular pieces are 2 - ' - ' 2,074,829 '_ in the same planes, and leaving a rectangular slit lliinlinewiththeslit?. - . On the opposite side of the electron-accelerat ing electrode 9 from the cathode 5, there are a pair of parallelly disposed metal plates 12 of a ?at rectangular con?guration, arranged sym metrically with respect to the slits 8 and H, the purpose of which is to de?ect the electron beam in a controllable manner, also to focus the elec 10 trons during de?ection, as will be described here inafter. For receiving the electrons, ‘there may be provided a pair of physically separate auxil iary anodes l3 which are also conveniently made of angular pieces spaced apart to leave a slit It 15 in line with the slits of the other electrodes. Di rectly in back of the slit l4, there may be .pro vided the main electrode or anode l 5 for receiving the electrons under certain conditions. The elec trode l5 conveniently takes the form of an elon 20 gated hollow cylinder provided with a slit 16 which faces the slit M in the auxiliary anodes l3. 3 through a conductor 23, which is connected, to one end of the heater. The other end of the heater conveniently makes contact with the cathode cylinder 5 so that a return for the heater ' energy is provided through the cathode ‘wire 22. The extreme positive terminal of the battery 20 is connected to the electron-accelerating elec-, trade 9. > ‘ The combined electron-de?ecting and electron focusing members l2 are- bridged by a high re 10 sistance 24 and the mid-tap on this resistance is connected by means of a conductor 25 to an in termediate terminal on the battery, as shown. Separate conductors 26'are taken from both ends of the resistance 24 so that these conductors are 15 connected directly to the respective electrodes I2. The physically separate auxiliary anodes l8 are likewise bridged by a high resistance 21 and a the arrangements of the supporting members are conductor 28 taken from the mid-tap on the re sistance back to a terminal on the battery which 20 is less positive than the terminal connected to the electrode 9. A conductor 29 is also provided between the battery 20 and the main anode l5, theterminal on the battery towhich the conduc tor 29 is connected being preferably more positive 25 than the terminal to which the conductor 28 is multifarious and will readily occur to those skilled connected. in the tube manufacturing’ art. A source of controlling voltage is applied across the conductors 26 which may conveniently be The manner in which these electrodes are sup ported from the four-pillar stem is clearly shown in Fig. 1, and a detailed description of the elec 25 trode supports is believed to be unnecessary since Furthermore, the manner in which these electrodes are sup 30 ported within the tube does not constitute a part of the present invention. It is suf?cient to state that the electrodes and their supports are mount ed in a symmetrical and rigid manner-within the tube, utilizing rods of glass H, where neces 35 sary, to insulatingly support one electrode from another. Each electrode is preferably supported at two places so as to lend rigidity to the struc ' considered the input circuit, and a current indi 30 cating or measuring device connected across the conductors 30 which may be considered the out put circuit of the device. The operation of‘ the tube is clear from the circuit relations shown in Fig. 2. The ?lament 6 serves to heat the cathode 5 which, on account of being electronically active, emits a profuse ture as a whole and suitable leading-in conduc tors are taken through the stem to the exterior. stream of electrons which move through the slits 40 A getter cup l8 containing magnesium or similar depending upon the amount of de?ection given material is conveniently secured to one of the support rods in a position as to be heated, by a high frequency coil placed around the envelope during evacuation so that the magnesium may be 45 ?ashed and the envelope relieved of deleterious remnant gases. The electrodes are given the usual gas-denud ing and eat treatments prior to placing within the envelope and the tube evacuated to a high 50 degree, for example, less than a few microns of mercury, by attaching a vacuum pump to the tube 4. When the proper degree of vacuum has been obtained, the tube 4 may be sealed OE With in the stem 2, as is well known in the art. It will 55 be understood that, if desired, instead of being operated as a high vacuum tube, the envelope may contain one or more inert gases, such as argon or neon, at reduced pressure. A base, not shown, of the usual construction is usually pro 60 vided about the lower end of the tube. A number of contact plugs may be molded in the base and connected to the various leading-in conductors; these plugs register with terminals in a socket for conveniently making electrical connection 65 with the electrodes within the tube. Fig. 2 shows one form of circuit which may 8, H, and either strike the auxiliary anodes I3, the‘electron beam en route, or else pass through the slit it between the auxiliary anodes and through the slit it into the anode l5. Due to the elongated con?guration of the various slits through which the electrons pass, the electrons take the shape of a beam in relatively thin sheet form. . It is apparent that the electrode ‘I, being con nected to the negative end of the battery 20, in troducesa ?eldwhich acts symmetrically along the 50 length of the cathode and on all of the electrons because the cathode is of an equipotential char acter. This electrode therefore serves to focus the electrons, i. e. to constrain them to a desired shape, depending upon the shape of the slit 8. 55 It is also evident that the electrode 9, being con nected to the positive end of the battery 20, pro duces a positive ?eld in the region of the cathode which serves to give to the electron beam, as it emerges from the slit 8, an extremely high veloc 60 ity. Thus, it may properly be said that the cathode 5, the negatively-charged focusing mem ber 'l, and the positively-charged accelerating electrode 9, together constitute an “electron gun" which causes a fast-moving and highly concen trated beam of electrons to emerge from the be employed with the improved tube. As shown slit ll. therein, there is a source of electromotiveforce'20 This electron beam, after leaving the slit II, is electrostatically deflected by the electrodes l2, of direct current voltage which may comprise a 70 battery, and various taps taken from the source to the electrodes. The negative terminal of the battery is connected by a conductor 2| to the focusing member ‘I and an intermediate terminal is taken to the cathode 5 by a conductor 22. The 75 battery 20 may also provide energy for the heater . i. e. given' a transverse or sweeping movement 70 across the tube, depending upon the magnitude of the control voltage applied to the conductors 26. As the beam moves across the tube in response to the electrostatic ?eld exercised by the elec trodes l2, variable portions of the beam strike the 75 3 2,074,829 electrodes I 3 and I5. Thus, in the arrangement shown in Fig, 2, when the beam is de?ected to ward the left-hand electrode l2, practically all of the beam strikes the left-hand auxiliary anode I3 and little, if any, of the beam will pass through the slit l4 and reach the anode I5, and practically none of the beam will strike the right-hand anode l3. When the beam is de?ected the other way, i. e toward the right-hand electrode l2, it traverses the slit H, at which time all of the beam temporarily passes into the anode l5 and, upon further de?ection, the beam strikes the stant magnitude which acts symmetrically along the length of the cathode and on all of the elec trons in the beam because the cathode is of an equipotential character and has no potential drop therein which might interfere with the focusing ?eld. The manner in which this improved connec tion operates to introduce an added focusing effect will be at once clear when the equipoten tial lines, suggested by the dotted lines, are con 10 sidered. The positively-charged electron-accel erating electrode 9 produces a ?eld within the right~hand auxiliary anode I3. It is obvious space con?ned by the electrodes I2 which may that, as the beam impinges on either the left- ‘ take the form of a series of loops 3|, symmetri cally arranged about the slit l I andextending for ; hand anode I3, the main anode [5 or on right hand anode I3, depending upon the amount and a substantial distance within the said space. direction of de?ection given the beam by the elec This distance is determined by the difference in trodes l2; the respective electrodes I 3 become potential between the electrodes l2 and 9. There variably charged, both in magnitude and polarity. are similar equipotential lines which take the These variations of electrical charge can be de form of inverted loops 32 and also extend down 20 tected or measured by suitable devices and instru ments connected to the conductors 30 or to the wardly from the auxiliary anodes l3 for a con siderable distance into the space between the de conductor 29. ?ecting electrodes I2. As in the case of the loops It is apparent that, due to the manner in which - 3|, the distance that the loops 32. extend into the thev electrodes are disposed with respect to one another and, consequently, the manner in which the tube operates, the variations of the output current not only represent a satisfactory repro duction of the voltage variations applied to the 3 O de?ecting electrodes l2 but also amplify these voltage variations to an extremely large degree. Thus, the device has application as a radio fre quency and audio frequency amplifier in radio and other intelligence communication circuits and, in addition, can be designed to detect radio signals efficiently. Electron beam tubes employing intermediately positioned de?ecting electrodes are, of course, well known to the prior art. My speci?c im 40 provement in a tube of this sort consists in em ploying the de?ecting electrodes not only for the usual de?ecting function, but also for assisting the focusing member 1 in maintaining the orig inal shape of the electron beam as it passes 45 through the tube on its way to the anodes l3, l5. It will be understood that, in order for the tube space and their con?guration depend to some ex trodes l2. The electrical charges on the de?ect lng electrodes, due to the current ?owing from the battery through the conductor 25, produce equi potential loops 33 which extend toward one another in the manner roughly suggested by the dotted lines. - Now supposing an electron beam is moving to ward theanode and is temporarily in the space between the de?ecting electrodes. The individ ual electrons will tend to cross the respective equipotential lines at right angles thereto and in a direction from the lower potential line to the higher potential line. By noting the posi tion of the arrows 344, which are drawn at right angles to the dotted lines, it will be seen that there is a constant force acting on the electrons which continually urges them toward the center of the space and away from the de?ecting elec . trodes themselves. This continual urge tends to to provide a satisfactory reproduction of the volt age variations applied to the conductors 26 in terms of current variations at the conductors 30, keep the electrons in the beam packed together 50 it is necessary that the electrons maintain the quently, that portion of the beam which strikes same position within vthe electron beam as it moves through the tube until it ?nally reaches either one of the electrodes l3 or the main anode l5 represents an accurate proportion of the en the electron-receiving surfaces. Whereas heretofore, the de?ecting electrodes tirebeam determinable by the magnitude and polarity of the voltages applied to the de?ecting had a tendency to diverge or spread the beam away from its original shape due to the electro static ?elds'introduced between de?ecting mem bers, in accordance with my invention, I have found that it is entirely feasible to so modify the 60 de?ecting members and their electrical circuits as to prevent this divergence or spreading out, and actually to provide an added focusing action at the position of the de?ecting electrodes. This desirable effect is brought about by the use of a potential which may be either positive or negative with respect to the cathode, depending upon the distance between the plates, and which is applied in the same polarity and magnitude to each of the de?ecting electrodes. For this purpose, the 70 de?ecting electrodes are electrically connected by a high resistance 24 and a conductor taken from the mid-tap of the resistance back to a suitable positive or negative terminal on the battery 20. As in the case of the focusing electrode 1', the de 75 ?ecting electrodes also introduce a ?eld of con 25 tent upon the relative potentials existing between the auxiliary anodes i3 and the de?ecting elec and’ to maintain the original shape of the beam as it moves through the de?ection zone. electrodes. Conse Therefore, the tube as a whole tends to amplify without distortion, and the current available at the output circuit conductors 3!] rep resents a faithful reproduction of the voltage variations applied to the conductors 26. It will be understood that the above-stated theory, 60 based upon the position of equipotential lines, is offered purely for explanatory purposes and .I do not desire to be limited thereto. It is a fact, confirmed by many tests and regardless of theory, that, when the de?ecting members are main tained at a'?xed average potential with respect to the equipotential cathode and different from the potential of the anode in accordance with my invention, the output current variations fol low with much more faithfulness the changes 70 in potential applied to the de?ecting members than when the latter are not so connected. While I have shown the combined de?ecting and focusing electrodes ll being used in con nection with a focusing member _1, it is obvious 75 2,074,829 that the latter may be dispensed with, if desired, as su?icient focusing effect for ordinary pur poses may ordinarily be obtained from the de ?ecting electrodes. However, it is considered preferable to utilize the focusing member ‘I in addition to the improved de?ecting electrodes. Fig. 3 shows the application -of the invention to a cathode beam tube which utilizes a ?uo rescent screen 36. In this figure, the anodes I 3 10 and i5 have, of course, been omitted since the electrons now impinge upon the screen to form a light image, for visual or photographic pur poses, of the voltage'variations applied to the conductors 26. In this ?gure, elements, which 15 correspond to the elements shown in Fig., 2, have been given the same reference'characters. Thus, the de?ecting electrodes II are bridged by a re sistance 24, and a conductor 25 taken preferably from the mid-tap of the resistance to the battery 20. As in the case of Fig. 2, there is present in the space between the electrodes l2 equipotential lines, indicated roughly by the loops 3| and 33, which tend to converge the individual electrons of the beam passing through the tube into a 25 packed condition, similar to the condition pro duced by the focusing action of the member ‘I. The arrows 34 represent the direction in which the electron-constraining forces act and it will be noted that this force is always exercised to ward the center axis of the tube. Unless the de ?ecting electrodes II are provided with a ?xed average potential negative or positive with re spect to the equipotential cathode and different from the anode, which potential is applied to both electrodes, of the same polarity and mag nitude, the electron beam tends to spread and to be attracted toward the electrodes while the beam is being de?ected so that the light image, as shown on the ?uorescent screen, does not rep 40 resent a faithful reproduction of the voltage variations applied to the conductors 26. However, in view of the focusing eifect pro vided by the de?ecting electrodes 12 in accord ance with my invention, the electron beam main tains its original focused condition as‘ it moves through the tube and, hence, the light image on the ?uorescent screen varies exactly in accord- - ance with the variations of voltage applied to the conductors 26. As was explained in connection 50 with Fig. 2, the focusing member ‘I may be en tirely‘ dispensed with and the focusing e?ect ob tained 'solely from the de?ecting members, but it isv considered preferable to utilize the electrode 7 in addition to the focusing effect offered by the electrodes i 2. While I have described and illustrated my in vention in connection with an electron beam tube in which the cathode rays are obtained initially from an equipotential source of electrons and the 60 beam takes on a more or less elongatecon?gura tidn, it is to be understood that the invention is not limited to this form of cathode or shape of beam. Obviously, the combined de?ecting and ditions as are provided in the case of the equi potential cathode. What I claim as-new and desire to secure by Letters Patent of the United States, is:1. An electron beam tube comprising an en velope containing an electron gun including an equipotential cathode for producing electrons in a fast-moving focused condition, and a common means for de?ecting the beam across the tube and for simultaneously maintaining the beam in 10 its focused condition, and means for receiving the electrons. 2. In combination, an electron beam tube com prising an envelope containing an equipotential source of electrons, an anode, a plurality of com 15 bined electron-de?ecting and electron-focusing electrodes positioned on opposite sides of the en velope between said source and said anode, a source of electromotive force, the negative termi nal of which is connected to said source of elec 20 trons, and connections from a positive terminal on said source of electromotive force to the elec tron-de?ecting electrodes, and a connection from a different terminal on said source to said anode. 3. An electron beam tube comprising an en velope containing an equipotential source of elec trons, an electron-receiving member, an electron accelerating electrode positioned between said source and said member, and a combined elec tron~de?ecting and electron-focusing electrode 30 interposed between said electron-accelerating electrode and said electron-receiving member. 4. An electron beam tube comprising an en velope containing a source of electrons includ ing an indirectly heated cathode, an electron-re ceiving member, an electron-accelerating elec trode positioned between said source and said member, combined means for sweeping the elec tron beam across the face of said member and for focusing said electrons, said means including 40 a pair of electrodes disposed on opposite sides of the envelope, a resistance connected between said electrodes, and a conductor between said resistance and said electron source, said com bined sweeping and focusing electrodes being 45 charged to a different potential from the poten tial of said electron-accelerating electrode and ?xed with respect to the average potential of said source of electrons. 5. In combination, an electron beam tube com prising an envelope containing an indirectly 50 heated cathode, an anode, a plurality of com b‘ned electron-de?ecting and electron-focusing electrodes respectively positioned on opposite sides of said envelope between said cathode and 55 anode, a resistance between said electron-de ?eeting electrodes, a source of electromotive force, said cathode, anode, and resistance being connected to different potential terminals on said source of electromotive force. ' 6. An electron beam tube comprising an en velope containing an electron gun including an 60 equipotential cathode for producing electrons in focusing function exercised by the .electrodes I2 a fast-moving focused condition and a com is equally applicable to beams of any and all shapes, depending upon the shape of the open mon means for de?ecting the beam across the tube and for simultaneously maintaining the .beam in its focused condition, and means for receiving the electrons, said common means in cluding a plurality of metal members maintained at a ‘fixed average potential with respect to said 70 ings 8, ll, etc. Furthermore, it is also evident that instead of an indirectly heated cathode as shown and described, any suitable and well known form of directly heated cathode, for ex ample, a flat spiral ?lament may be employed, in which case the connection 22 is brought back to a point on the ?lament circuit which repre sents the average potential of the ?lament so 75 as to retain the same symmetrical electrical con electron gun but independently operable by a control deflecting voltage. ' 7. An electron beam tube comprising an elec tron gun including an indirectly heated cathode for producing electrons in a fast-moving f0- 76 £074,829 cused condition, a main anode, a plurality of auxiliary anodes positioned between said main anode and the electron gun, means including electrodes charged to a positive potential of ?xed value with respect to said electron gun for de ?eeting the electron beam across the face of the auxiliary anodes and for maintaining the focus of said electrons, said auxiliary anodes being maintained at a ?xed average potential with re 10 spect to said electron gun and different from the potential of the main anode. 8. An electron beam tube comprising an elec tron gun including an indirectly heated cathode for producing electrons in a fast-moving‘focused condition, an anode vfor receiving the electron beam, and intermediately positioned electrodes for de?ecting the beam across the anode and for simultaneously maintaining the beam in its fo cused condition, said anode comprising a plurality of physically separate members which are charged in a variable manner depending upon the extent of the beam portion which strikes the respective ' members. 9. In combination, an electron beam tube com H) Li prising an envelope containing a source of elec trons, a main anode, a plurality of auxiliary an odes, and a plurality of electron-de?ecting elec trodes positioned on opposite sides of the en velope between said source and said main anode, 30 resistances respectively between said auxiliary anodes and between said electron-de?ecting elec trodes, a source of electromotive force, the nega tive terminal of which is connected to the source of electrons, and connections between di?erent positive terminals on said source of electromotive force and each of said resistances. 10. An electron beam'tube comprising an en velope containing an equipotential source of elec trons, an electron-focusing electrode surrounding 40 said source, an electron-receiving member, an electron-accelerating electrode positioned between said source and said member, and a combined electron-de?ecting and electron-focusing elec trode interposed between said electron-accelerat 45 ing electrode and said electron-receiving member. 11. An electron beam tube comprising an elec tron gun including an indirectly heated cathode 5 for producing electrons in a fast-moving focused condition, an anode for receiving the electron beam and intermediately positioned electrodes for de?ecting the beam across said anode and for simultaneously maintaining the beam in its fo cused condition, said anode comprising a plurality of physically separate members which are charged in a variable manner depending upon the extent of the beam portion which strikes the respective members, said intermediate electrodes being 10 maintained at a ?xed average potential with re— spect to said electron gun. 12. An electron beam tube comprising an en velope containing a source of electrons including an indirectly heated cathode, an electron-focus ing electrode surrounding said source, an electron 15 receiving member, an electron-accelerating elec trode positioned between said source and said member, and a common means arranged on the’ opposite side of said electron-accelerating elec 20 trode from said electron-focusing electrode for simultaneously de?ecting and maintaining the focus of the electrons, said means including an electrode for providing an electric ?eld having a contour similar to the shape of the electron beam 25 as it leaves said electron-focusing electrode. 13. An electron beam tube comprising an en velope containing a source'of electrons including an indirectly heated cathode, means for con— straining said electrons to a beam of rectangular 30 cr0ss~section, an electron-receiving member, an electron-accelerating electrode positioned between said source and said member, and a pair of metal plates arranged on the opposite side of said elec tron-accelerating electrode from said electron— 35 constraining means, said plates being positioned in planes corresponding to opposite sides of said beam, said plates having such positions with re spect to the remaining elements of the tube and being adapted to be charged to such a ?xed av 40 erage potential with respect to said electron source that the electric ?eld set up by said plates serves to maintain the initial focus given to the beam by said electron-constraining means and permit a free movement of the focused beam when _ a de?ecting voltage is applied to said plates. JOHN M. CAGE.