Патент USA US2404343код для вставки
vJuly 16, 1946.A 2,404,343. J. E. HENDERSON ETAL PHoToTUBE's AND METHOD 0F MANUFACTUBE Filed Oct. 14, 1945 4, . lNvl-:NïoRs JosEPH EHENDsnsoN B ¿ROBERT BJQNES ` W ß?/ ATTORNEY 2,404,343 " Patented July 16, 1946 UNITED STATES ÈATENT ÍoFFlCE Joseph E. Henderson, Seattle, Wash., and Robert B. Janes, Verona, N. J.; saifd Henderson as signor to the United States of America, as represented by the Secretary of Navy and said .lanes assigner to Radio Corporation of America, a corporation of Delaware l Application October 14, 1943, Serial No. 506,274 10 Claims. - ' (Cl. Z50-_465) 2 , 1 Figure 4 is a longitudinal sectional View of apparatus suitable for performing one of the Our invention relates to photo-electric tubes and their-’method of manufacture, and particu larly to tubes incorporating dual cathodes having principal operations involved in the manufacture of the phototube hereinafter described. coatings of elements such as antimony, arsenic and~ bismuth sensitized with an alkali metal. In co-applicant Janes’ copending application, Serial No. 434,681 filed March 14, 1942, there was described a phototube of a very rugged type ca pable of withdrawing high values of acceleration both longitudinally of the tube and when the tube 10 ' is subjected to an'angular acceleration, or cen tripetal acceleration such' as exists when a whirl In thel following description we will refer spe ciñcally to antimony as a cathode> coating and it will be appreciated that arsenic and bismuth are the full equivalents of antimonyy and may be substituted in whole >orin part for the antimony without departing from the scope _ofour inven tion. f V' > i -In accordance ‘ with our invention’ we have found that a tube comprising a tubular section or sections of insulating material and closed at opposite ends by metal closure caps may be as ing motion about‘its'longitudinal axis is'given to the tube. In this prior tube it was substantially impossible to obtain a very close spacing between the anode and cathode While still retaining its rugged character and'v high sensitivity. For ex semb'led> with an additional -cathode' intermediate the closure caps if certain precautions are taken in the order of assembly and in the application ample, co-applicant .Janes found that it was nec essary to separate the anode and cathode by a ofthe antimony coatings on the cathode founda distance of at least three-quarters ofan inch. 20 tions, such as on one of the closure caps and the l Certain applications require _closer spacing than ’intermediatecathode foundation. More particu larly we -»have found that a tube of the type de this and, furthermore, such lapplications require scribedin co-applicant Janes’ above-mentioned the use of a second cathode which preferably application may be constructed with an addi- , serves as an anode to the ñrst cathode, tional photo-cathode intermediate opposltely dis It is an object of our invention to provide a posed envelope closure caps serving as anode and very rugged phototube of the dual cathode anti mony, arsenic >or bismuth coated type; It is an cathode respectively with the two cathodes ex without distortion or mechanical failure of the parts or variation in the operating characteris tics of the tube while providing >a structure which cordance with our invention, the tube comprises two end closure caps _land 2, each of which is ceedingly close together, provided the cathode other object toprovide a dual cathode photo tube of the alkali metal treated antimony, arsenic 30 foundations are provided with their antimony coatings following the sealing of the foundations or bismuth type, wherein the cathodes may be >or foundation supports inthe tubular envelope. placed very close together. It is a further object Referring to Figure 1 whereinv we have shown to provide .a phototube of the dual cathode type ka phototube having dual cathodes made in ac which will withstand high forces of acceleration sealed to Vpre.determined lengths o_f glass tubing 3 and 3e. The minimum axial length of the tubing 3 is not critical andmay be considerably less may be easily processed .and having high photo sensitivity. It is a further object to provide an improved method of manufacturing a very rugged phototube o-f the dual cathode antimony, arsenic and bismuth coated types; It is a still further obj ect Ito provide a method of manufacture allow ing the production of dual antimony coated cath odes withoutdeterioration of the antimo-ny coat- t ing or coatings during processing.' l yThe foregoing and'other objectsyfeatures and advantages of our invention will 'be apparent when considered in view’of the following descrip tion and the accompanying drawing wherein, ` Figure 1 is a View in longitudinal section of ' a than AVone-'half inch although the minimumlength 40 of .thevtubingggëa must not `be less than'one-half inch Vand‘is _preferably not less than three-quar tersï’of an inch. ‘Preferably one of the caps; such ' - as' "rl-he#A cap I, is apertured‘as shown at 4 and is provided with aglass’ftubulation 5 sealed around the'aperture `for evacuation and sothat »following evacuation the tubulat'ion'> maybe closed Vsuchwa's ‘by a V»tippirig-off operation. ‘The opposite closure cap 2 Aisnon-apertured- and suppórts‘asource 6 ofV 'alkali metal> such as a caesium compound re v'ducible ‘toY _caesium upon vthe application> of >hea/t phototube made in accordancewith our invention, ` - ' to the central outer area of the capl. ' " In addition 4and in ' accordance with our ï-inven Figure 2 is a cross sectional view of the photo tube shown in Figure 1 taken along the lines 2-2,‘ 'i 4tionwe provide intermediate the closure caps vI and >2 `a secondcathode foundation] at a distance, i Figure 3 is a sectional view of -a modified elec 55 :preferably desertores .Closure cap l 'than théhlö trode for use in the tube of Figure Ñl., and " 2,404,343 3 , Y sureccap 2. The foundation 'I serves both as an the tubing 3 and 3a. A chrome-iron which we anode for the iirst cathode and, when further have found satisfactory for such use with lime processed, as a cathode with respect to the cap 2. glass contains as the principal constituents-k Further, inv accordancewith 'our invention the closurecapl supports a closely adjacent coating Percent Chromium _________________________ _ _ of antimony oran equivalent >element facing in the general direction of the cap 2 but shieldedA _, Nickel therefrom by the second cathode foundationl. ' As shown in Figure 1, the‘reasons for which ap-L ' pear more fully hereinafter, the secondcathode 10 26-30 ____ 0.5 Manganese ________________________ __ 0.5 Silicon _____________________________ __ 0.5 Iron __ _____________________________ __ Balance Following formation of a closure cap I to a satis factory form, onecap for each tube is apertured foundation 'I is supportedat aV relatively'short distance from the end cap'I land at a larger dis tance from the end cap 2 -by vsupporting means t as shown at 4 andwhere a foundation member other than the cap for the first cathode is desired, such as a ring~shaped or annular support mem ber 8. It has been found that the foundation'l 15 such as the disc IB shown in Figure 3, the disc vII?) is attached to the cap I, such as by welding. The cannot be photo-electrically sensitized with an alkali metal treated antimony, arsenic or bis-` ‘ " material of the disc I0 as well as of the founda-f tion 1 is preferably of high chromium content alloy such as chrome-nickel, the content of chro minimum, such as> less than one-half inch al 20 mium ranging from 5 to 30% by weight, the alloy being oxidized to a greenish color as disclosed in though this distance is preferably not less than muth coating if the distance between the end cap 2 and the coating is less than a predetermined Janes" copending application,- vSerial No. 481,246 three-_quarters of an inch. y However, in accord filed March 31, 1943. Thetubulation 5 is then sealed around the aperture '4 and the cap I oxi very close spacings ,less'than the minimum dis tance-,of one-_half inch by following oury improved 25 dized to provide'a film of oxide which forms a good bond` between the'cap I and thev glass tubing 3 method- _of. manufacture. Since the cathode ance with our invention/We are able to provide during the next operation' of sealing these two parts together. Such oxidation may occursimul foundation 'I serves as a cathode with respect to . thefcapßÍ-and'as ¿an anode withrespect to the >taneo'usly with thesealing of ~the tubulation 5 to end_‘capï I ,A andlthe end cap _I is made'photo-sen sitive, the relatively close spacingV betweenthe .30 foundation'l~ and end cap I provides characteris ticsïwhich were unobtainable in tubes of the types described _using antimony coatings.l Conse- , _the cap I',f.although alternatively'the formed caps may beuoxidizeîdV in moist vhydrogenV as described byHull, vBurger and Navis _in an‘article entitled, “_Gïlassfto-metal seals,” part 2, "J curnal of lApplied quently, in_accordance with our invention wek pro Physics, volume 12, No; 9,' September 1941', pages toltheïuglasstubingf» land of the support ring 8 toboth the glass tubing sections 3 and 3a, a coat ing-` ofna’ntimony 9on-l the inner surfaceY of the with the surface of the capV land the disc I0, if such vdisc isÍused as 'the cathode foundation. If ' vide,¿follo¿wing the assembly of the end capl 35 698-707. ' Such Íiiring produces a relatively> thick coating of greenish'colored chromic oxide integral the moist hydrogen' oxidation step is used we end_,cap I as shown in Figure 1, or on a founda tion», _I_û supported by the end cap I as shown in 40 prefer to bake the end‘ caps for a sufficient length Figure-_5.A> AQnly then is the foundation ‘I sup ported within the tube on the support ring 8, Vsuch las by welding ¿metaltabs I I between the founda tioni ,and the support ring 8 or other mechanical >of- time," such as in a non-oxidizing atmosphere » _coating I2 o_f an element such as antimony either before‘ïor‘after its attachment to the support î'ri'pgßiby the maar tabs, l l. , -More particularly we have found Ythat it is not _of Vfires heating" the rim of the cap and the lower end of the tubing 3. 'vWe use a similar sealing step to attach the support ring 8 to the upper end of .the glasstubing 3 and to the' lower en_d ofthe glass tubing'Sa.' All 'of these steps are performed at atemperatureof 500° C. forabout twelve hours to removeany occludedhydrogen. 'l'he seal be attachment. ’ The foundationA 1 is provided with a 45 lonlylydesirable but necessary to provide the an timony coatings 9 ,and I2 at a definite time dur ing'rtheï sequential manufacturing steps to pre ¿vent Vinjury to these coatings during subsequent steps of theßmanufacturing processes. For eX ample, .if thel coatings 9y and I2 _are subjected to relatively high temperatures, >such as occur when 50 1n accordance with our invention before the ap plicationof theantimonycoatings S and' I2, the cap I'and the foundation ‘I only then being ready for the application ofthe antimony coatings 9 and >Il which are applied in separate steps; f Referring toFigure 4 and prior to’attachinent of the foundation 'I toïthe ring member 8,' ‘we insert the glass tubing 3"and ßa'ove'r a tubular or- the closure cap I is sealed to the glass tubing 3 _orwhen the support rings is sealed between the _tubularglass portions 3 _and 3d, permanent injury _occurs‘mto the coatings.’ The sealing operations tweenthe end capV ’IV and the glass tubing 3^may be. made'byrotatin'g the parts 'in the presence 60 cylindricalopen endedlshieldV I5, _theÍshield ex tending'ltowithin close proximity of the endcap f musthecessarily Vbe performed in the presence nI' or the disc I 0,' if such disc is "used, anden-which _ofïnorrnal atmosphericïconditions *and- our se the' antimonyf vis to loe-deposited. Í l The .shield AI5 4is preferably.supportedrwithin a'chamber or bell jquence ogprocessingsteps avoids or substantially>> l tesV material oxidationof the antimony . jar lßcapable'of being '.evacuated."y We"alsofsup"- , _cpatir,lgsl on the foundations. g Furthermore, the 65 Vport, opposite theï'cap I> a? _source ofantimcny to ,closure _cap I and the support ring 8 must be sub- . be vapòrizle'd - and " condensed ~'thereonJ- ' Such a source ofÍanti'inony may- comprisea refractory ¿je ,_ ed¿to¿ce_rtain»processing steps to provide good glproperti'es at the time the seals are‘made >`.hetwee,nr-_lthesemembers and the glass tubings 3 Vand 3d, such¿steps-fbeing_incompatible with pre viouslyapplied antimony coatings. Y ,- ,The `»closure _caps ;I- and 2, as well as the ring metal; 9011y l1 supportingy a quantity 4Vof 'antimgny ¿I8 onotherelement such/asV arsenic or,` .bismuth 70 and whichvmay _belvaporizedrby passing> an elec Ktric current through the. connecting leads i9. 4,lî’ollotv'ing ¿therinrsertion of théÍOpen >endeVdjvv'aiis '‘ mberß, are-_preferablyof material such as Lof- 'theV tubeshown in »Figurellß’ ~the bell` `J „chrome-iron having a, cov-efficient _of- expansion:A is evacuatedftoîaghigh .Vacuums A.the .residuallair A`substantially matched with that ofthe glass of 7 pressure preferablymbeiná less than 40.5 "microns » _ I ar'IIìí @#04343 6 and sufficient antimony is yvaporized froml the source I8 and condensedon the inner surface of the cap I to 'provide the'antimony coating 9.- The ~ thickness `of this antimony coating Amay Arange fromva thickness'corresponding to 0.1 to 0‘.'16»mi1- ligram per square centimeterywhichis sufficient to provide good sensitivity when such a-- coating is treated with alkali metal. The rate of vaporiza . minutes to one-half hour, we vapor-ize alquantitv of alkali metal such as caesium from the- source 6 to sensitize both of the >coatings -9 and I-2-._ îTo allow -access of the alkali metal to the antimony coating 9 the foundation 1 is provided with 'an aperture 4a although sufficient spacing `may be ` provided about the periphery of the foundation. Following the vaporization of the alkali `metal the tube is baked, preferably at a temperature `of 160°» tion and condensation is preferably'low,_being less than 0.2 milligram per'square centimeter of the 10 C., for thirty minutes and during this baking the alkali :metal apparently combines with Athe anti surface to be vcoated per second, since higher rates mony'coatings to provide photocathode surfaces of condensation may beA detrimental, forming a having very high sensitivity to light. Following non-uniformcoating.- The entire :bell jar assem the baking the tubulation 5 may be tipped-off and bly With the exception of the coil I1 and the heated antimony source I8 is preferably maintained at 15 the tube removed from thel pump and preferably rebaked at a'temperature of 160°>C. fora period room- temperature during the evaporationand of twenty minutes, following which'the tubeis` condensation steps, except for `such slight heating aged to further stabilize the photoelectric emission of the cap- I as may occur by radiation fromthe from the cathode. ' " In operation the cap I serves as a cathode con The Yantimony coating I2 on the ,foundation 1 20 nection and is operated at a negative potentialV may be applied to a similar thickness in a simi with respect to the ring member 8 which sup lar manner either in the bell jar- I6 following Aat ports and is electrically connected to the cathode tachment of the foundation 1 to the yring member foundation 1, this member likewise being main 8 by the metal strips I I, in> which >event'the shield I5 is made somewhat'shorte'r terminating 'adja 25 tained at a negative potential with respect to the .anode cap 2. The'electrons liberated from the cent the upper surface of the foundation 1,l `alcoating 9 are ldirectly proportional to theïlight though the antimony coating I2 may be applied incident thereon through the glass tubing 3 and prior >to its attachment while separately sup similarly electrons liberated from the coating I-2 ported in vacuum with-exposure to a heated an timony source. If this latter method is used the '30 and collected by ‘the anode cap 2 are directly proportional to the light incident on the coating foundation 1 is affixed to the ring member 8 fol lowing the application of the antimony coating I2. “I_n accordance with our invention and following theapplication'andiassembly steps referred to above, the envelope formed by the tubular glass ‘sections 3 and 3a. is closed by sealingjthe vcap_2 to the upper end of the tubing Salat a sufficient distance, such as three-quarters of an inchv from I2 through theglass tubing 3a. Consequently the disclosed structure isv ideally adapted to -inulti-V directional use wherein either one or more light sources. or a broad source such as the sky are fusedv since the' cathode'smay be illuminated from all azimuths' on» sides facing theA respective fanodes, I ' » . i ' the surface of the nearest adjacent antimony coati -- While »we have `described AourA invention with a'small apertured container,- whereupon'the cap ode »phototubea’can -«be made both in the struc ture fandgin the method of manufacturing with ing, such as the coating I2. A source 6 of alkali 40 Äparticular reference to a dual-cathode phototube Vand'. have set forth our,A preferred method of metal such 'as a caesium bearing compound jis manufacturing such a tube,- it will be appreciated first valii-ized to the inner surface> of the end cap 2, that various modiiications'such as multiple cath such as by enclosing al compound of -caesium in 2, previously oxidized as ‘described above, is sealed to the upper end of the glass tubing 3a.. To pre-k vent'excessive heating of the antimony coatings out :departing ‘from the spirit of our invention orthe scope Vthereof as set forth in the appended during this ñnal sealing step, we prefer toV cool the ring member 8 as well as the yend cap I, such 1f. A phototube comprising a tubular >glass en vas by a blast» of air directed thereon during the 50 velope, a metal closure at each end of and form sealing -of the cap 2 to the upper »end of the glass ingï the -end~ walls of said envelope, -al cathode foundation extending transversely of said en The'only other,u precaution which need be fol velope intermediate said closures, a coating se lowed in the assembly of `our'dual cathode photo tube is the maintenance of the antimony coatings 55 lected from the group consisting of antimony, arsenic, and bismuth on the surface of said foun in the absence of high concentration of water va dation facing one of said metal closures, a simi por, especially during the time these coatings are lar coating on the other of said closures and subjected to temperatures above normal room tem alkali metal within said envelope to sensitize said perature. Consequently the relative humidity of . the atmosphere to which the coated cathode foun 60 coatings. 2. A phototube comprising a tubular glass en dations are subjected should be low and prefer velope, a metal cap sealed to each end of said ably less than 80% relative humidity at 25° C., envelope, a coating selected from the group con which corresponds to a water vapor-concentra sisting of antimony, arsenic, and bismuth on one tion equivalent to 8 grains of water vapor per cubic footvof air. The satisfactory results ob 65 of said metal caps as a cathode foundation, a second cathode foundation extending transverse tained are believed to be due to the fact that ly of said envelope between said caps, a coating antimony does not oxidize when subjected to nor selected from the group consisting of antimony, mal atmospheric conditions in the presence of low arsenic, and bismuth on the surface of said foun humidity. ' claims# l' ' We claim: ‘ l ` « ~ \ Following the assembly of the tube as shown in 70 dation facing the other of Said caps, and a quan tity of caesium within said envelope to sensitize Figure 1, the internal Volume thereof is exhausted said coatings. , through the tubulation 5 and the tube is baked at 3. yA phototube as claimed in claim 2 wherein a temperature of 275 to 310° C. to remove any said coatings are of antimony. occluded gases contained in the tube parts. Fol 4. A phototube comprising a tubular envelope lowing this baking which may be from `iìfteen 75 2,404,343 Y .7 , of ~transparent material, `a metal cap. sealed -. .to comprising sealing one or said caps toene end and'closing'each ofthe opposite ends of saidven velope, a cathode foundation extendingl >trans of said’ member, sealingafsuppo'rt'fora photo sensitive electrode intermediate the .ends of `said versely of said -envelope between saidmetalïcaps member, depositing an element selected _fromxthe and being spaced more closely to one of said caps ’ group consisting of antimony,.arsenic» and bis than the other cap, a coating selected fromrthe group of elements consisting of` antimony;_arsenic_ math-on a-surface in'electrical contact with the cap 'sealed to -oneend- of said'meníber, attaching andgbismuth 0n said one of-said4 caps andga sec an - electrode- foundation `'adapted to bel photoelec ondi Coating selected `from Asaid group of >elements tricallysensitized Vto said support and then seal on,` tlfiezsurface Vof , said foundation facing the ing theother cap to the other end of said mem ber, evacuating the envelope formed by said mem ber and said.A caps, land sensiti'zing said _deposited other ofi-said caps.;` and anv alkali-metal> deposited on- „each o_f- said- coatings' to render said coatings photo=emissive. ' v Y ._ -- - > I '- element and said foundation with an alkali metal. -Y '~„ 5, 1A: phototube-.comprising a Vcylindricalv glass envelope, af metal cap at each'end of said en 15 velope,._«;one' of said caps »being lapertured and closed by an lexhaust tubuiation, la-'cathode foun ing comprising sealing one of said closurefcaps to [one end ofv one of> said sections of glass tubing, dationafûxed-‘directly to oneY of; saidcaps 'and facing in the direction of the other-of said caps, ,ak second cathode foundation Vextending _trans versely across said envelope parallel to and be sealing a support for a photosensitive electrode 20 tothe opposite-end of said one-section,seali_ng one» end of ther-other section of glass ltubing to tween said caps a-nd closer to said iirst cathode foundation than to the other end cap, and a coating of alkali metal treated antimony on each of said, cathode foundations. Y . ‘ " 6. A phototube comprising a pair of coaxial, separated transparent envelope portions sealed 9. vThey method of manufacturing a Vphototube having an envelope of two metal closure caps sealed to and separated by sections of glass .tub said support coaxial with said one section, deposit- ,Y ing .a coating of an element which when sensi _tized with an alkali» metal is photo-sensitive on 25 a surface vadjacent said one closure cap, attach- ' ing a foundation which when sensitized ¿with an alkali..metal Vis photo-sensitive -orí'said support, at their adjacent ends to a metalsupport ring in sealing' the other closure cap >to the other end of a plane transverse to said envelope, a metal cap said-other glass tubing section to form an en sealed‘to each of the opposite ends of said envel 30 velope,fevacuating said envelope and sensitizing ope portions, a coating of alkali metal treated- an said coating and said foundation with an alkali ` timony _onrone of said metal caps and a photo metal.- , ` ' ' Y i' sensitive electrode extending transversely across . 10`. The method Vof 1 manufacturing a photo said envelope and supported by said metal supu tube having two closure caps separated by tubular y port ring between said coating and the other of 35 insulating material comprising sealing one of `" said metal caps and having a photo-sensitive surface facing said other metal caps. _ . 7. A phototube comprising a. pair of longitudi said .closure Vcaps to» one end of said tubular in sulating material, sealing an 'electrode support to said insulating material intermediate the opposite ends thereof, inserting an open-ended shield with-l nally spaced coaxial transparent envelope por tions sealed at their adjacent ends to an elec 40 in the Aopen end of said tubular insulating material trode support member, one of said portions hav beyondsaid electrode support and to within close ing anaxial length less than three-quarters of an proximity of said sealed'closure cap, evaporating inch, the other having a minimum length of ap and-condensingantimony on a surfaceadjacent proximately one-half to three-quarters of an inch, a Dhotocathode attached to and carried by said electrode support, a metal end cap closing the open end of each of said envelope portions and a coating of caesiated antimony on the cap-sealed to that envelope portion whose minimum length is approximately one-half tov three-quarters, of aninch. ' H » , 8. The method of manufacturing a phototube having two closure caps separated by a tubular insulating member and an intermediate electrode saidclosure cap while the inner walls of said in sulating material and said electrode support are vprotected from condensation rthereon by said open ended shield, removing said shield, attaching an antimonycoated electrode to said-electrode sup i port, sealingthe other closure cap to the open end `of said tubularinsulating- material to'form an envelope evacuating said envelopeand sensitiz ing said antimony with an alkali metal. _ JOSEPH E, HENDERSON. ROBERT B.' JANE'S.