US3128531A - Dynodes for electron discharge tubes and methods of making same - Google Patents

Dynodes for electron discharge tubes and methods of making same Download PDF

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Publication number
US3128531A
US3128531A US60643A US6064360A US3128531A US 3128531 A US3128531 A US 3128531A US 60643 A US60643 A US 60643A US 6064360 A US6064360 A US 6064360A US 3128531 A US3128531 A US 3128531A
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United States
Prior art keywords
film
frame
supporting
coating
dynodes
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Expired - Lifetime
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US60643A
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English (en)
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Wilcock William Leslie
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National Research Development Corp UK
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National Research Development Corp UK
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/023—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof secondary-electron emitting electrode arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/10—Dynodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
    • H01J9/125—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes of secondary emission electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/32—Secondary emission electrodes

Definitions

  • This invention relates to improvements in or relating to certain types of electron discharge tubes, and is especially applicable to image intensifier tubes.
  • dynodes which promote electron multiplication without loss of the relative spatial distribution of the electrons representing the image to be intensified.
  • Each dynode is in the form of a thin film which consists of one or more layers one of which is of a substance which is a good emitter of secondary electrons and is positioned in the tube in a plane parallel to the plane of the photocathode.
  • An electron lens is provided so arranged as to focus the electron image radiated from the photocathode or from a previous dynode on to the dynode so that a new electron image will be generated in the form of a transmitted secondary electron emission from the dynode.
  • the essential requirements of such a dynode are that it should have good secondary emission properties and that it should have adequate conductivity so that it may be maintained at a potential appropriate to its position in the tube and it is also desirable that it should have sufiicient mechanical strength to be selfsupporting. It Imust also be capable of withstanding the baking temperatures of the order of 300-400 C. to which it is normally subjected during evacuation of the tube.
  • a method of making dynodes for incorporation in electron discharge tubes said dynodes consisting of an outer frame and a composite film supported by said outer frame, said composite film including an electron-permeable supporting layer and a layer of secondary emission material said method comprising the steps of producing on the supporting frame a slack, thin, supporting film, forming on one surface thereof a coating of secondary emission material, said coating of secondary emission material being of smaller dimensions than the area enice closed within the frame and being so situated Within the frame that a margin is left between the outer edge of the secondary emission material and the inner edge of the frame so that, on subsequent baking, at least some of the slack in the supporting film is taken up by shrinkage of said electron emission material.
  • the film should be conducting and therefore it will be understood that, where either the electron-permeable supporting layer or the secondary emission material is not itself sufficiently conductive, an extra layer of conductive material must be added to render the film conducting. Where a layer of conductive material is provided, it must be in direct contact with the layer of secondary emission material.
  • the step of producing said slack, thin supporting film on said supporting frame comprises mounting said film taut on said frame and then stretching said lm so that it acquires a permanent slackness.
  • this is carried out by choosing the materials of the film and the frame so that the thermal co-efiicient of expansion of the material of said thin, supporting film is less than the thermal co-eflicient of expansion of said supporting frame and then stretching said film so that it acquires a permanent slackness by heating said film and supporting frame to a temperature such that the expansion of said frame relative to said thin, supporting film stretches said film past the yield point thereof and then cooling said film and said frame.
  • the frame across which the film is supported may be of any material suitable for use in high vacuum equipment and capable of withstanding the temperatures encountered in the baking of the tube.
  • a soda glass ring as the supporting frame along with a material chosen from the group consisting of aluminium oxide and magnesium oxide as the thin supporting film.
  • Aluminum oxide has been found to be especially suited.
  • a slack film of aluminium oxide can be provided by suitable heat treatment.
  • a metal such as aluminium could be used as the thin, supporting layer in which case it would be necessary to select a material, preferably a metal, for the supporting frame which has a larger thermal co-eiiicient of expansion than the metalused as the supporting layer.
  • the best known and most suitable are the alkali metal halides and the alkaline earth metal halides, especially potassium chloride.
  • the method of making dynodes comprises the steps of producing on a soda glass ring, a slack, thin supporting film of aluminium oxide, forming on the surface of said film a coating of aluminium'and thereon a coating of potassium chloride, said coating of potassium chloride being concentrically disposed and of smaller dimensions than the area enclosed within the soda glass ring to provide a margin between the outer edge of said potassium chloride and the inner edge of said lsoda glass ring whereby, on subsequent baking, at least some of the slack in said supporting film is taken up by shrinkage of said potassium chloride.
  • the step of producing said slack, thin film of aluminium oxide on said soda glass ring comprises mounting said thin, supporting film of aluminium oxide taut on said soda glass ring and then stretching said aluminium oxide film so that it acquires a permanent slackness.
  • the step of stretching said aluminium oxide film so that it acquires a permanent slackness comprises heating said aluminium oxide lm and said Soda glass ring to a temperature such that said aluminium oxide film is stretched past the yield point thereof.
  • the temperature to which the aluminium oxide film and soda glass ring are heated in order to effect the stretching is preferably in the range of about 300 C. to 500 C.
  • any contraction in the secondary emission layer of the film due to heating of the dynode is accommodated by the slack in the thin, supporting layer and thus no undue stresses are set up in other layers of the film.
  • a dynode suitable for incorporation in electron discharge tubes comprising a supporting frame, a slack thin supporting film securely attached across said frame, said supporting film being of an electron permeable material, and a coating of secondary emission material on one surface of said film, said secondary emission material being marginally spaced from said supporting frame, whereby when the dynode is subjected to high temperatures during its incorporation in an electron tube at least some of the slack in said supporting film is taken up by shrinkage of the coating of said secondary emission material.
  • the supporting frame is conveniently circular in shape.
  • the thermal co-efficient of expansion of said film is less than that of the metal of said supporting frame.
  • said dynode comprises a supporting frame, a slack, thin supporting film attached across said supporting frame, said fiim consisting of material chosen from the group of aluminium oxide and magnesium oxide, and a coating of secondary emission material on said film, said secondary emission material being selected from the group consisting of alkali metal halides and alkaline earth metal halides, said secondary emission material in area being of smaller dimensions than the area enclosed by said frame to leave a margin between it and the frame.
  • said dynode comprises a soda glass circular ring supporting frame, a slack thin supporting film attached across said frame, said film being comprised of a layer of aluminium oxide, a layer of conductive material and on said layer of conductive material a coating of potassium chloride said potassium chloride coating being concentrically disposed within said frame and of smaller dimensions to provide an annular margin between its outer edge and the inner edge of said frame.
  • said conductive material is aluminium.
  • said dynode comprises a circular ring supporting frame, a slack thin supporting lm securely attached across said frame, said lm being comprised of aluminium oxide having a coating of aluminium thereon, and a coating of a secondary emission material on said film, said secondary emission material being disposed concentrically within said ring frame and of smaller diameter to leave a margin between it and the frame, whereby on subsequent baking during incorporation in an electron tube at least some of the slack in said supporting film is taken up by shrinkage of the coating of said secondary emission material.
  • an electron discharge tube having incorporated therein at least one film type dynode said method comprising the steps of attaching across a supporting frame a slack, thin supporting film, forming on one surface thereof a coating of secondary emission material, said coating of secondary emission material being of smaller dimensions than the area enclosed within the frame and being so situated within the frame that a margin is left between the outer edge of the secondary emission material and the inner edge of the frame, mounting said structure Within an electron discharge tube, and baking the tube to outgas it and at the same time to take up at least some of the slack in said supporting iilm by shrinkage of the coating of secondary emission material, and sealing said tube.
  • said method comprises the steps of attaching across a soda glass circular ring supporting frame a thin film of aluminium oxide, coating said aluminium oxide with aluminium, providing .slack in said composite film by heating the same beyond 1ts yield point and then permitting the same to cool, thereafter forming on one surface of said composite film a coating of potassium chloride, and spacing said coating from said frame to provide annular margin between its outer edge and the inner edge of said frame, mounting said structure within an electron tube, and baking said tube while evacuating the same, whereby the tube is outgassed and the potassium chloride coating layer is shrunk so that at least some of the slack in said composite film is taken up, and sealing said tube.
  • FIGURES 1 4 show cross-sectional views of a dynode in the various stages of preparation as hereinafter described.
  • FIGURE 5 shows a plan view of the completed dynode.
  • FIGURE 6 shows a plan View of an electron discharge tube having incorporated therein a number of film type dynodes at a stage during the manufacture thereof.
  • the ring and film were then baked in an oven at 460 for a few minutes and then allowed to cool.
  • the resultant film was slack and appeared puckered in form as illustrated in FIGURE 2.
  • a thin film of aluminium 3 was then evaporated on to the surface of the aluminium oxide, and on to the composite film so formed was deposited, again by means of vacuum evaporation, a coating of potassium chloride 4.
  • a marginal region of the aluminium oxide film was masked during this second evaporation so as to restrict the area covered by the potassium chloride coating and leave a margin between the inner circumference of the soda glass ring and the outer circumference of the potassium chloride layer. Both the aluminium coating and the potassium chloride coating followed the contours of the aluminium oxide as illustrated in FIGURE 3.
  • the discharge tube consisted of a cylindrical tube 5 at opposite ends of which were situated a photocathode plate 6 and a liuorescent screen 7.
  • the dynodes f5 were inserted at intervals along the tube, each dynode being xed in a position transverse to the axis of the tube by a mounting wire 9 sealed into the wall of the tube.
  • the tube was provided in the usual way with a number of electrodes 10 which, during the operation of the tube, are maintained at different potentials relative to each other so that a suitable potential gradient exists along the length of the tube.
  • a conventional electron lens such as the coil 11.
  • the tube was evacuated. During the evacuation, the tube was baked at 300 C. for 10 hours and, on cooling, it was found that the potassium chloride coating on the dynodes had shrunk, and the composite lm structure had taken on the form illustrated in FIGURE 4.
  • the central area carrying the potassium chloride layer was flat while the annular portion of the aluminium and aluminium oxide films between the ring and coating of potassium chloride could then be seen to be tightly puckered in close radial creases as shown in FIGURE 5 indicating a state of tension due to the contraction of the central area.
  • the tube 5 was sealed off at the outlet pipe 12.
  • a method of making dynodes for incorporation in electron discharge tubes said dynodes consisting of an outer frame and a composite film supported by said outer frame, said composite film including an electron-permeable supporting layer and a layer of secondary emission material, said method comprising the steps of producing on the supporting frame a slack, thin, supporting film, forming on one surface thereof a coating of secondary emission material, said coating of secondary emission material being of smaller dimensions than the area enclosed within the frame and being so situated within the frame that a margin is left between the outer edge of the secondary emission material and the inner edge of the frame so that, on subsequent baking, at least someA of the slack in the supporting film is taken up by shrinkage of said electron emission material.
  • a method of making dynodes according to claim 1 wherein the step of producing said slack, thin supporting film on said supporting frame comprises mounting said film taut on said frame and then stretching said film so that it acquires a permanent slackness.
  • a method of making dynodes according to claim 2 wherein the thermal co-eiicient of expansion of the material of said thin, supporting film is less than the thermal co-eticient of expansion of said supporting frame and the steps of stretching said film so that it acquires a permanent slackness comprises heating said film and supporting frame to a temperature such that the expansion of said frame relative to said thin, supporting film stretches said film past the yield point thereof and then cooling said film and said frame.
  • a method of making dynodes for incorporation in electron discharge tubes comprising the steps of producing on a soda glass ring, a slack, thin supporting film of aluminium oxide, forming on the surface of said film a coating of aluminium and thereon a coating of potassium chloride, said coating of potassium chloride being concentrically disposed and of smaller dimensions than the area enclosed within the soda glass ring to provide a margin between the outer edge of said potassium chloride and the inner edge of said soda glass ring whereby on subsequent baking, at least some of the slack in said supporting film is taken up by shrinkage of said potassium chloride.
  • a method of making dynodes according to claim 8 wherein the step of producing said slack, thin film of aluminium oxide on said soda glass ring comprises mounting said, thin, supporting film of aluminium oxide taut on said soda glass ring and then stretching said aluminium oxide film so that it acquires a permanent slackness.
  • a method of making dynodes according to claim 9 wherein the step of stretching said aluminium oxide film so that it acquires a permanent slackness comprises heating said aluminium oxide film and said soda glass ring to a temperature such that said aluminium oxide film is stretched past the yield point thereof.
  • a method of making dynodes according to claim 10 wherein said aluminium oxide film and said soda glass ring are heated to a temperature in the range of about 300 to 500 C.
  • a method of making an electron discharge tube having incorporated therein at least one film type dynode comprising the steps of attaching across a supporting frame a slack, thin, supporting film, forming on one surface thereof a coating of secondary emission material, said coating of secondary emission material being of smaller dimensions than the area enclosed within the frame and being so situated Within the frame that a margin is left between the outer edge of the secondary emission material and the inner edge of the frame, mounting said structure within an electron discharge tube, and baking the tube to outgas it and at the same time to take up at least some of the slack in said supporting film by shrinkage of the coating of secondary emission material, and sealing said tube.
  • a method of making an electron tube having at least one lm type dynode mounted therein comprising attaching across a soda glass circular ring supporting frame a thin film of aluminium oxide, coating said aluminium oxide with aluminium, providing slack in said composite film by heating the same beyond its yield point and then permitting the same to cool, thereafter forming on one surface of said composite film a coating of potassium chloride, and spacing said coating from said frame to provide annular margin between its outer edge and the inner edge of said frame, mounting said structure within an electron tube, and baking said tube while evacuating the same, whereby the tube is outgassed and the potassium chloride coating layer is shrunk so that at least some of the slack in said composite film is taken up, and sealing said tube.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
US60643A 1959-10-22 1960-10-05 Dynodes for electron discharge tubes and methods of making same Expired - Lifetime US3128531A (en)

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GB35850/59A GB884053A (en) 1959-10-22 1959-10-22 Improvements in or relating to dynodes for use in electron discharge tubes and methods of making same

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US3128531A true US3128531A (en) 1964-04-14

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US (1) US3128531A (US08124317-20120228-C00034.png)
DE (1) DE1173596B (US08124317-20120228-C00034.png)
GB (1) GB884053A (US08124317-20120228-C00034.png)
NL (2) NL123904C (US08124317-20120228-C00034.png)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3262007A (en) * 1963-07-26 1966-07-19 Hollingsworth R Lee Single gun compatible color reproduction tube
US3458913A (en) * 1966-04-19 1969-08-05 Siemens Ag Supply cathode for electrical discharge vessels and method for its production
US3755865A (en) * 1969-05-01 1973-09-04 Gen Electric Novel mesh-reinforced sec target for camera tubes

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1699597A (en) * 1924-03-27 1929-01-22 Westinghouse Lamp Co Evacuating audion tube
US2624024A (en) * 1949-10-26 1952-12-30 Hartford Nat Bank & Trust Co Cathode for use in electron discharge tubes
US2677873A (en) * 1946-01-10 1954-05-11 Us Navy Method of making nickel sponge cathodes
US2708788A (en) * 1947-06-03 1955-05-24 Emi Ltd Rendering metal meshes taut
US2721372A (en) * 1951-06-30 1955-10-25 Philips Corp Incandescible cathodes
US2746129A (en) * 1949-11-16 1956-05-22 Bell Telephone Labor Inc Method of producing a taut thin member
US2871086A (en) * 1956-02-10 1959-01-27 Westinghouse Electric Corp Method for baking and exhausting electron discharge devices
US2881343A (en) * 1957-04-16 1959-04-07 Rca Corp Electron multipliers
US2942133A (en) * 1953-06-05 1960-06-21 Electrical & Musical Ind Ltd Electron multipliers

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2871368A (en) * 1956-09-21 1959-01-27 Itt Image multiplier

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1699597A (en) * 1924-03-27 1929-01-22 Westinghouse Lamp Co Evacuating audion tube
US2677873A (en) * 1946-01-10 1954-05-11 Us Navy Method of making nickel sponge cathodes
US2708788A (en) * 1947-06-03 1955-05-24 Emi Ltd Rendering metal meshes taut
US2624024A (en) * 1949-10-26 1952-12-30 Hartford Nat Bank & Trust Co Cathode for use in electron discharge tubes
US2746129A (en) * 1949-11-16 1956-05-22 Bell Telephone Labor Inc Method of producing a taut thin member
US2721372A (en) * 1951-06-30 1955-10-25 Philips Corp Incandescible cathodes
US2942133A (en) * 1953-06-05 1960-06-21 Electrical & Musical Ind Ltd Electron multipliers
US2871086A (en) * 1956-02-10 1959-01-27 Westinghouse Electric Corp Method for baking and exhausting electron discharge devices
US2881343A (en) * 1957-04-16 1959-04-07 Rca Corp Electron multipliers

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3262007A (en) * 1963-07-26 1966-07-19 Hollingsworth R Lee Single gun compatible color reproduction tube
US3458913A (en) * 1966-04-19 1969-08-05 Siemens Ag Supply cathode for electrical discharge vessels and method for its production
US3755865A (en) * 1969-05-01 1973-09-04 Gen Electric Novel mesh-reinforced sec target for camera tubes

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DE1173596B (de) 1964-07-09
NL123904C (US08124317-20120228-C00034.png)
GB884053A (en) 1961-12-06
NL257110A (US08124317-20120228-C00034.png)

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