Патент USA US2123024код для вставки
Í July 5, 193s. - E. R. PloRE Er AL 2,123,024 ELECTRODE FOR ELECTRIC DISCHARGE _,DEEVIGEISk Filed May 29, Bu 193s . « ' t Louis Malter M Gttorneg \ 2,123,024 Í nieuwe .my s, yuns ` f UNITED STATES PA'ïrENT-v OFFICE' ` anaest ELECTRODE FOB EDECTRI‘C DISCHARGE ` DEVICES . 1 . Pa.. and Louis Emanuel lt. Piore, Philadelp )Kalten Oaklyn, N. J., asaignors to Radio Cor-. poration of America. a corporation of Delaware Application May zo, massaal No. n.452 _ ' . schaun.- wieso-#215) This invention relates to electric discharge de vices, particularly to electrodes therefor, and has - for its» principal object the provision of an elec » trode having improved photo-sensitive and sec ' with which it is treated. Thus, whereas the prior art dictates the treatment of silver (whose oxide has a>~heat of 4formation of the order of 5000 calories per mol.) with a single application of caesium (whose oxide hasla heat of formation l, g ondary-electron emissive characteristics. Other objects will be apparent and the inven ~ of substantially 88,000 calories per mol.) , the pres tion itself will be best understood by reference to ent invention involves a double application of caesii'im,y or the like ‘(with the- introduction of the'foliowing specification andto lthe accom oxygen between these applications), to a metal ‘ Fig. 1 is a diagrammatic view of an electron> whose oxide has a heat of formation of the same 10» order- o_f magnitude as that 0f caesium. multlplierf system wherein an electrode con Among the metals whoseì emissive character structed in accordance with -the invention may istics .may be enhanced by the improved method be utilized, . _ Fig. 2 is a partly diagrammatic cross-sectional of my invention are beryllium, zirconium, molyb 1s view'greatly‘ enlarged of a multiplying electrode denum. columbium and zinc. The heat of for- l5 mation of the oxides, per oxygen bond, of these constructed in accordance with the principle .of ` metals is of the order of 80,000 to 90,000 calories the invention. A . per mol. The alkali metals preferably employed In order to increase the photo and secondary electron emissive characteristics of certain metals, in treating the `above mentioned metals- are cae-v zo such for instance as silver, it has previously been sium, rubidium, and zpotassium. The heat of '20 proposed to oxidize the metal and to treat the l formation of the oxides of these metals are, re panying drawing, wherein: 1o oxidized surface with caesium, rubidium, sodium, spectively, 88,000, 88,500, and 86,800. Sodium> whose oxide has a heat of formation of substan electron emissive constant of 'l to 9 is obtainable f" tially~100,000 may be included in this group. yI_n carrying the _invention intoeil'ect the elec- 25 25 with caesium on oxidized-silver: rubidium on oxi trode to be treated is first pre-oxidized, either ' or other electro-positive metal. A secondary > dized silver will provide an emissive ratio of sub before it is mounted in the dis stantially 6.5 to 8.5 secondary electrons to each ‘ electrolytlcally charge tube, or by- an oxygen glow discharge impinging electron. , within the tube itself, or it may be oxidized within _ In constructing electrodes of the type described, or without the tube in any known manner. Pref- '3o 30 the preferred practice is to mount the clean erably this oxide coating is of a thickness of they metal electrode structure in the tube and. after order of, say. three hundred atomic layers. 'With evacuation, to introduce oxygen into the.y tube. ` the oxidized electrode surface or surfaces mount The oxygen is activated orionized, as by the ap plication of an externally applied high frequency ed within the tube, the tube is highly evacuated a substantiaiamount of caes'ium, or like al- 35 35 neld and, thus activated. combines readily with ‘and kali metal, is distilled into it. preferably in the the electrode metal. When oxidization has been manner previously described. The excess `caecompleted the tube is re-,evacuated- Caesium, slum or other vapor is removed as by baking at which may be contained Lin the form of pellets within an auxiliary container connecting with 'a temperature of 200° P. for about ten minutes 40 the tube contai the electrodes. is-vaporized as with the tube o'n the pump. by the applicationo heat and the resulting’vapor admitted and allowed to remain in the tube for. enters'into the main tube and combineswith the say three minutes, until it has reacted with- the A oxidized metal to render it emissive. ExcessiveJ caesium to form a layer of a _mixture constituted caesium is- removed or "taken-up," within the ß tube. The tube is baked, on the pump; and the l of an oxide of caesium 'and the oxide o! the metal ‘ _of which the base is formed.. The tubeis then re- 45 'I'he4 present invention contemplates and its exhausted, after- which the electrode is again bathed in the alkali metal vapor. This' second only been oxidized'and treated (as with caesium) the- alkali metal on the siirface of the "mixed _. sealing-in operation completed. ' practice provides a metal electrode which has not ` bath o! metal vapor forms a molecular layer of ` I. but also re-oxidised and retreated witlr the same nalkali metal. The metal whose surface is to be rendered emissive is selected from the group of oxide layer". The excess metal vapor isremoved i0 by baking and pumping, as before, and thetube ' is then sealed oil. I _ f Referring now to Fig. l of the drawing in metals whose oxides have a `heat of formation',1 per oxygen bond, of .the 'same'or substantially which electrodes'formed in accordance with the Il the same order as that of the metallic element invention are utilised in an _electron multiplier ß 2 2,123,024 device of a' known type. The device comprises , Referring to Fig. 2, the base lupon which the a Y-shape evacuated container I, within which, mixed oxide layer and the alkali metal coating adjacent the closed ends of one of its arms, is is applied may be it mere sheetvof beryllium inti mounted a photosensitive cathode 3 and adjacent mately -iointed, as by evaporation, to a base of the‘closed end of the other of its arms is an out another and cheaper metal, such for instance as put ' electrode 5. A third electrode 1 is mounted nickel. Such construction is recommendedl where between `the input and output electrodes 3 and the metal to which the mixed oxide layer and al 5 in the angle or stem of the Y-shape container kali metal `coating is applied is not available in‘ l. Both electrodes 3 and ‘I are constituted in ac cordance with the invention of a metal base hav ing a mixed oxide coating and a layer of alkali metal superimposed on this coating. The out put electrode 5 may be of nickel or other suitable material. 15 . A_variable or a constant lightsource may be so disposed with respect to the container that light therefrom falls upon the photosensitive cathode. In the drawing, such light source is ex empliiled by a lamp 8 connected'in circuit with 2 O a battery 9 and a variable rheostat II, and a lens I3. . Under the influence of light from the source, electrons leave the surface of the photosensitive `cathode in random directions. Since it isde 25 sirable to focus all suchelectrons upon the multl-, plying electrode an electromagnetic coil I5 may be disposed around one arm of the container be tween the photo-,sensitive cathode and the multi A similar coil I 'I i»may be dis ‘ plying electrode. posed around the other ,arm of the container for the purpose of focusing secondary electrons upon ' the output electrode. The several focusing coils may beprovided with unidirectional potential from a battery I9 or the like. In the drawing these coils are exemplified sheet form. , As indicated in both Figs. 1 and 2, when the electrons constituting the primary beam from the cathode strike the composite electrode surface with sufficient energy, secondary-electrons are emitted. The electrons, so released are drawn to the collector electrode, or if desired to another similar surface for further multiplication by rea son of the electric field applied between the -emitter and the target electrode. While the invention has been described in con nection with a photo-actuated electron-multiplier tube, it is to be understood that its application is not to be limited tothe particular type of tube here described, as the disclosure, in this respect, is merely illustrative for purposes of explaining the inventive concept. What is claimed is: ' 1: An electrode comprising a metal base hav ing thereon a layer of a mixture of an oxide of said metal and an oxide of an alkali metal whose oxide has a heat of formation, per oxygen bond, of substantially the same order as that of the oxide of the metal constituting said base, and a coating of said alkali metal superimposed on said . layer. . . 2. An electrode comprising a base of a metal 35 as being connected in parallel to the battery,\ whose oxide has a heat of formation, per oxygen a potential divider 2| and a plurality of contact' devices 23 and 25 being'utilized for the purpose of individually controlling the magnitude of the several focusing field currents. - It is our under standing that the polarity of the coils is imma terial. A1ternative1y,`.` electrostatic focusing o'f the electrons may be resorted to, or a combination >of electrostatic and magnetic focusing. 45 In the operation of an electron multiplier of thetype under discussion the output electrode 5 may be connected to any suitable utilization cir cuit, such as a relay21. When utilizing a multi plier of the type shown, the photosensitive~cathode 60 may be connected tothe negative terminal of a potential divider 29 that connected across a bond, of the order of substantially 80,000 to 90,000 calories per mol., a layer on said base constituted - . -of an' oxide of said metal and an oxide of an alkali metal Whose oxide has a heat of formation, 40 per oxygen bond, of the order of substantially 80,000 to_100,000 calories per mol., and a surface coating of said alkali metal on said layer. 3. An electrode comprising a base of beryllium, a layer on said base constituted of beryllium and casesium oxides and a surface coating of caesium on said layer. 4. An electrode _comprising a base of beryllium, a layer on said base constituted of beryllium and rubidium oxides and a surface coating of rubidium on said layer. ì ' , 50 source of unidirectional potential 3l, the- output 5. An electrode comprising a base of beryllium, electrode 5 connected to the positive terminal of a layer on said base constituted of beryllium `and f the potential divider and thev multiplying electrode potassium oxides and asurface coating of potas 55 'I connected to an intermediate point thereon. f siumvon said layer. 55 The relative .potentials shown in rthe drawing EMANUEL' R. PIORE. are to be construed solely as illustrative. ' ' LOUIS MALTER.