Classifications

• • 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
  • H01J43/18—Electrode arrangements using essentially more than one dynode
  • H01J43/24—Dynodes having potential gradient along their surfaces
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making

Definitions

• This invention relates to electron multiplier and image intensifier devices. More particularly the invention relates to channel intensifier devices (referred to also more briefly as channel plates) and to electronic tubes employing such devices.
• Such devices are secondary-emissive electron-multiplier devices comprising a matrix in the form of a plate having a large number of elongate channels passing through its thickness, said plate having a first conductive layer on its input face and a separate second conductive layer on its output face to act respectively as input and output electrodes.
• a potcntial difference is applied between the two electrode layers of the matrix so as to set up an electric field to accelerate the electrons, which field establishes a potential gradient created by current flowing through resistive surfaces formed inside the channels or (if such channel surfaces are absent) through the bulk material of the matrix.
• Secondary-emissive multiplication takes place in the channels and the output electrons may be acted upon by a further accelerating field which may be set up between the output electrode and a suitable target, for example a luminescent display screen.
• the distribution and crosssections of the channels and the resistivity of the matrix are such that the resolution and electron multiplication characteristic of any one unit area of the device is sufficiently similar to that of any other unit area for the purposes envisaged, the greatest uniformity being usually required for imaging.
• an imaging tube or system such a channel plate is used in an imaging tube or system
• the latter will be referred to for convenience as an image intensifier? tube or system rather than as an image converter" tube or system even in applications vwhere the primary purpose is a change in the wavelength of the radiation of the image.
• the invention provides a method of manufacturing a channel plate including in addition a membrane obturating an end of each channel or a channel plate wherein such membranes are formed as extensions of the input electrode of the plate so that said electrode and membranes form, together, a continuous layer, which method includes the steps of:
• the liquid may for example be a simple liquid or it may be dispersion or emulsion.
• various chemical and physical processes can be used and these include freezing (in the case ofa simple liquid) and breaking an emulsion.
• some of said processes e.g. heating
• a method of evaporating metals on to a frozen liquid is known and can be a very clean method. However, it is difficult to retain the meniscus at the mouth of the channels because the liquid contracts into the channels on freezing. It is also difficult to remove the liquid without breaking the aluminium film.
• a film forming material with suitable properties such as strength and good adhesion to nichrome and/or glass.
• Emulsion Lacquers Dispersions of very fine particles (e.g. 0.111.) of or ganic polymers in water are available as emulsions and referred to as emulsion lacquers.
• the emulsion has very low viscosity like water, so that it will readily fill the smallest channels normally used.
• the particles can be quickly caused to come out of the water (breaking the emulsion) and form a film on the meniscus by a wide range of physical and chemical means.
• the physical means include the use of heat, ultrasonics and electrical means.
• the chemical methods include the addition of electrolytes or surfactants and changing the pH value.
• the plate can be supported above the floor of a dish with the input side uppermost.
• the emulsion lacquer is poured into the dish until it reaches the bottom of the plate.
• the emulsion lacquer then rises by capillary attraction in the channels and forms meniscus surfaces at the input side.
• the emulsion is then broken by one of the methods referred to above.
• the lacquer layer formed on the meniscus surface also adheres at the edge of the meniscus to the nichrome or glass at the mouth of each channel. This layer is hardened (and also the water under the lacquer is removed) by warming the channel plate in an oven.
• the film oflacquer of meniscus shape remains across the mouth of each channel.
• the aluminium is then evaporated and the lacquer removed by baking.
• the aluminium film produced is, of course, of meniscus shape across each channel.
• Emulsions of various film forming polymers can be used, but methacrylates appear to be the most suitable at present. They can be readily removed after use by baking as is known from their use as temporary support films in the aluminising of T.V. tubes.
• the emulsion is poured slowly into the dish containing the channel plate which is supported off the floor of the dish. When the emulsion level reaches the bottom of the channel plate it rises in the channels and can be observed when it reaches the top of the channels. In order to break the emulsion the dish and channel plate are warmed to 50C and this temperature maintained for ten minutes. The lacquer film will then have formed on the meniscus surface. The channel plate is then transferred to an oven at C for 2 hours in order to harden the film and remove the water under the lacquer film.
• the channel plate is then placed in a vacuum evaporation equipment, the pressure reduced to 10 torr and the aluminium layer (e.g., 1,000A. thick) deposited on the channel input side.
• the channel plate is then baked in air in an oven at 350C for 30 minutes to remove the lacquer.
• the emulsion used is Poly-2-ethoxyethyl methacrylate in water. lt has a solids content of 33 percent which is diluted to 0.6 percent solids before use.
• impurities consist of inorganic salts, emulsifying agents and unreacted monomer which are required for the preparation of the emulsion. Purification is carried out by ultra filtration.
• the channel plate is gently removed from the lacquer and the surplus drops of lacquer hanging from the lower surface and removed by wiping with a filter paper previously wet with water.
• the channel plate is then inverted and supported horizontally by a clamp on the sides of the channel plate so that both faces are accessible.
• a mesh having a diameter slightly smaller than that of the plate is then completely immersed in a dish of lacquer and then withdrawn when a layer of emulsion will be found over all the holes in the mesh.
• the mesh is placed on top of the channel plate. Additional lacquer is then run into the gap between the channel plate and the mesh until the gap is filled.
• the lower face of the channel plate is now heated in order to cause the emulsion particles to form a solid plastic film on the liquid meniscus surfaces on the lower ends of the channels.
• the heat is applied by an infra-red lamp from a distance cms below the channel plate for several minutes.
• the channel plate After the lamp is switched off the channel plate is allowed to stand until all the emulsion between the mesh and plate has disappeared. Emulsion then remains only in the channels above the solidified film at the bottom of the channels.
• the mesh is removed from the channel plate which is then transferred to an oven at 70C for 1 hour to dry out the liquid in the channels.
• the plate is put in the oven with the solidified film on the bottom side.
• the channel plate is then placed in a vacuum evaporation equipment.
• the channel plate is located on a rotating table (the centre of which is heated) cms above the aluminium source.
• the table surface is at an angle of 45 to the horizontal.
• the evaporating chamber is then pumped down below 10" Torr, and the table rotated at about rpm while a 500 A. layer of aluminium is deposited on the lacquer layer.
• the channel plate is then baked in air in an oven at 350C for minutes to remove the lacquer leaving an aluminium film in each channel in the shape of a meniscus.
• a non-reflecting black layer is required for some types of devices.
• This black layer can be provided on top of the first aluminium layer by evaporating aluminium through an inert gas such as nitrogen or argon at a pressu re above l0 Torr.
• This problem can be met by retaining the meniscus at the mouth of the channel which is being heated to secure film formation.
• a mesh located about 0.5-1 mm above the top surface of the channel plate and parallel to it.
• the channels are filled with water and the space between the channel plate and mesh is filled with water, the latter space acting as the reservoir.
• the capillary forces associated with the mesh are sufficiently strong to restrain the water while still allowing this excess liquid to act as a reservoir.
• the result of this method is to maintain the meniscus at the mouth of the channel during the period of heating so that a satisfactory solid film can be produced.
• the mesh has a further advantage in the'subsequent removal of the reservoir water since it can rapidly evaporate through the mesh.
• the mesh can be of woven wire or electroformed, made of nickel or stainless steel, and with a pitch about 0.8 mm.
• the mesh is at least 2 mm smaller in diameter than the channel plate it is used on. It can be supported 0.5 mm above the channel plate by bending down the edges of the mesh by that amount.
• Channel plates in accordance with the invention can be used in imaging tubes, for example an image intensifier tube of the proximity type or a tube of the electron-optical diode or inverter type.
• the invention may also be used for other imaging tubes, for example cathode-ray display tubes and camera tubes.
• a method of manufacturing a channel plate including in addition a membrane obturating an end of each channel or a channel plate wherein such membranes are formed as extensions of the input electrode of the plate so that said electrode and membranes form, together, a continuous layer, which method includes the steps of:
• a method as recited in claim 7 wherein a mesh is held close to the face of the channel plate remote from the desired supports, said mesh having such pitch and such spacing from the channel plate as to enable it to retain liquid between itself and the plate.
• emulsion is a dispersion of organic polymer particles in water.

Landscapes

• Printing Plates And Materials Therefor (AREA)
• Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
• Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=10472163

Family Applications (1)

Country Status (4)

Cited By (1)

Citations (10)

• 1970
  • 1970-11-18 GB GB5481770A patent/GB1319850A/en not_active Expired
• 1971
  • 1971-11-08 US US00196289A patent/US3781979A/en not_active Expired - Lifetime
  • 1971-11-15 DE DE19712156546 patent/DE2156546A1/de active Pending
  • 1971-11-16 FR FR7140941A patent/FR2114744A5/fr not_active Expired

Patent Citations (10)

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