EP1615254B1 - Dispositif et procédé pour minimiser le flux de verre dans la fabrication d'une plaque à microcanaux - Google Patents

Dispositif et procédé pour minimiser le flux de verre dans la fabrication d'une plaque à microcanaux Download PDF

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Publication number
EP1615254B1
EP1615254B1 EP20040400034 EP04400034A EP1615254B1 EP 1615254 B1 EP1615254 B1 EP 1615254B1 EP 20040400034 EP20040400034 EP 20040400034 EP 04400034 A EP04400034 A EP 04400034A EP 1615254 B1 EP1615254 B1 EP 1615254B1
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EP
European Patent Office
Prior art keywords
boule
packing tube
inner surfaces
dimension
glass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
EP20040400034
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German (de)
English (en)
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EP1615254A1 (fr
Inventor
Thomas T. Mabry
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ITT Manufacturing Enterprises LLC
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ITT Manufacturing Enterprises LLC
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Publication date
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Priority to EP20040400034 priority Critical patent/EP1615254B1/fr
Publication of EP1615254A1 publication Critical patent/EP1615254A1/fr
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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
    • H01J43/246—Microchannel plates [MCP]
    • 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

Definitions

  • the present invention relates to a fused boule for use in fabricating microchannel plates, a method of forming a fused boule, and microchannel plates for use with image intensifiers, and more specifically, to an arrangement for reducing glass flow during the manufacture of the plates, according to the preambles of claims 1 and 8.
  • Microchannel plates are used as electron multipliers in image intensifies. They are thin glass plates having an array of channels extending therethough and are located between a photocathode and a phosphor screen. An incoming electron from the photocathode enters the input side of the microchannel plate and strikes a channel wall. When voltage is applied across the microchannel plate these incoming or primary electrons are amplified, generating secondary electrons. The secondary electrons then exit the channel at the back end of the microchannel plate and are used to generate an image on the phosphor screen.
  • fabricating a microchannel plate starts with a fiber draw processes.
  • An etchable core rod is drawn within a non-etchable silicate tube to form a round fiber comprised of a core rod and cladding layer.
  • These fibers are then bundled and drawn into an equilateral hexagonal shaped pre-form known as a multi-fiber bundle.
  • Each multi-fiber bundle can contain over 10,000 core rod sites.
  • These hex-shaped multi-fiber bundles are packed into a glass packing tube and non-etchable hexagonally shaped support rods are packed between the bundles and the cylindrical wall to form a boule that is fused together in a heating process to produce a solid boule of rim glass and fiber optics.
  • Subsequent process steps entail slicing, beveling, and polishing the glass boule into plates. Afterwards, the plates are etched to remove the core rods within the plates to thus form the channels, each of which is defined by the cladding layer. The channels are then activated and metallized.
  • Movement of the fibers closer together can lead to missing channel walls after the etch process because there will not be enough cladding glass to form a wall between the channels. These missing channel walls can lead to any number of defects such as ion barrier or film emission points, reduced structural integrity and ruptures.
  • the initial fiber rods have been bundled to form fibers bundles which are drawn, and of course, fused during the drawing process to form fiber bundles which are combined to form fiber bundles which are drawn and, of course, fused during the drawing process, to form fiber bundles.
  • the bundles are placed in the jig, they have already been fused.
  • the present invention is concerned with a fused boule having the features of claim 1.
  • This boule includes a hollow packing tube formed of generally non-etchable glass for use in fabricating a microchannel plate.
  • the packing tube has a plurality of flat inner surfaces. Each surface is generally planar and extends generally parallel to the longitudinal axis of the tube.
  • the invention in another aspect, includes a boule having a plurality of optical fibers, each of which has a core formed of etchable material and a cladding layer formed of a non-etchable material and a plurality of support rods formed of a non-etchable material.
  • the fibers and rods are disposed in the glass packing tube with the rods located between the fibers and the flat inner surfaces of the packing tube.
  • the invention includes a method of forming a fused boule having the features of claim 8.
  • the method includes the steps of providing a bundle of fibers having an etchable core surrounded by a non-etchable cladding, packing the fibers into a glass packing tube having a plurality of flat inner surfaces, positioning a plurality of support rods between the fibers and the flat inner surfaces of the packing tube to form a packed boule and fusing the packed boule into a solid boule.
  • the present invention relates to a glass packing tube 550 used to form boules and which tube is configured to reduce the amount of glass flow when fusing the boule during manufacture of microchannel plates.
  • the packing tube 550 according to the present invention is made of non-etchable glass and has multiple flat interior surfaces 501 through 512. These flat surfaces are planar surfaces and allow the packing of fiber bundles 16 and support rods 24 within the glass packing tube 550 while maintaining minimal open space (as compared to a round internal surface) between the outermost support rods and the interior surface of the packing tube. This minimization of open space is advantageous because it reduces the flow of glass during the fusion process that forms a fused boule.
  • FIG. 3 shows a starting fiber 10 used to manufacture a microchannel plate for use as an electron multiplier.
  • the fiber 10 includes a glass core 12 and a glass cladding 14 surrounding the core.
  • the core 12 is made of a material that is etchable in an appropriate etching solution such that the core can be subsequently removed.
  • the glass cladding 14 is made from a glass which has softening temperature substantially the same as the glass core 12.
  • the glass material of the cladding 14 is different from that of the core 12 in that it has a higher lead content which renders it non-etchable under the conditions used for etching the core material.
  • the cladding 14 remains after the etching of the glass core 12 and becomes a boundary for the channel 32 which is left.
  • the optical fibers 10 may be formed in the following manner.
  • An etchable glass rod and a cladding tube coaxially surrounding the rod are suspended vertically in a draw machine which incorporates a zone furnace.
  • the temperature of the furnace is elevated to the softening temperature of the glass.
  • the rod and tube fuse together and are drawn into the single fiber 10.
  • the fiber 10 is fed into a traction mechanism where the speed is adjusted until the desired fiber diameter is achieved.
  • the fiber 10 is then cut into shorter lengths.
  • the multi-fiber or bundle 16 includes several thousand single fibers 10 each having the core 12 and the cladding 14 discussed above. This bundle 16 is then suspended vertically in a draw machine and drawn to again decrease the fiber diameter while still maintaining the hexagonal configuration of the individual fibers. The bundle 16 may then cut into shorter lengths.
  • the packing tube 550 is made of glass material which is similar to the glass cladding 14 and it too is non-etchable when etching away the glass core 12.
  • the glass packing tube 550 has a coefficient of expansion which is approximately the same as that of the fibers 10.
  • the lead glass packing tube 550 will eventually become the solid rim border of the microchannel plate as shown in Fig. 2 .
  • a plurality of support structures are positioned in the glass packing tube 550 between the bundles 16 and flat interior surfaces 501 through 512 of the tube.
  • the support structures may take the form of hexagonal rods of any material which is not etchable under the etching conditions used later to etch the core 12 and which has the necessary strength and the capability to fuse with the glass fibers.
  • Such support structures are shown as support rods 24.
  • the support rods may be one optical fiber or preferably a bundle of any number of fibers up to several hundred.
  • the final geometric configuration and outside dimensions of one support rod is substantially the same as one bundle 16.
  • the assembly thus formed by the fibers 10, support rods 24 and packing tube 550 is a packed boule 500 as shown in Fig. 5 .
  • the boule 500 is then suspended in a furnace and is connected to a vacuum system.
  • the temperature of the furnace is elevated to the softening point of the material of the bundles 16 and the support rods 24.
  • the bundles 16 fuse together, and the support rods 24 fuse to its adjacent bundles 16 and to the inner surface of the packing tube 550.
  • the support rods 24 act as a cushion between the interior surface of the glass packing tube 550 and the bundles 16. This cushioning provides structural support so that the individual fibers 10 do not distort during the heat treatment. In addition, the cushioning effect of the support fibers 24 makes it possible to use a higher heat during fusion without causing distortion of the fibers 10.
  • the fused boule is then sliced into thin cross-sectional plates.
  • the planar end surfaces are ground and polished.
  • the cores 12 of the fibers 10 are removed by etching with dilute hydrochloric acid. After etching, the high lead content glass claddings 14 will remain and form the channels 32.
  • the support rods 24 will also remain solid and thus provide a good transition from the solid rim of the glass packing tube 550 to the microchannels 32.
  • the plates After etching, the plates are placed in an atmosphere of hydrogen gas whereby the lead oxide of the non-etched lead glass is reduced to render the cladding electron emissive.
  • a semiconducting layer is formed in each of the glass claddings 14 and this layer extends inwardly from the surface which bounds each microcharmel 32.
  • Thin metal layers are applied as electrical contacts to each of the planar end surfaces of the microchannel plate which provide entrance and exit paths for electrons when an electric field is established across the microchannel plate by means of the metallized contacts.
  • FIG. 5 shows a cross-sectional view of the packed boule 500 having a packing tube 550 formed with a plurality of flat or planar, inner surfaces 501-512 (in the case of Fig. 5 , the number of flat surfaces is twelve).
  • planar it is meant that each surface forms a plane and each plane, i.e., each surface extends longitudinally and parallel to the central axis of the tube 550 and is generally perpendicular to the radius of the outer wall of the tube.
  • These inner surfaces can be provided by either machining or mandrel shrinking (over a shaped mandrel) the inside surface of the glass packing tube. Such techniques for forming such glass tubes are known to those skilled in the art.
  • the number of sides can vary and is dependant on the size and shape of the fused boule. In the embodiment disclosed herein where the boule has a generally circular cross-section, it is preferred that the tube 550 has at least 8 flat surfaces and preferably, 12 such surfaces.
  • the support rods 24 can be pushed into the tube 550 in either bearing contact with the inner surfaces or in very close proximity thereto.
  • the rods 24 have a hexagonal cross-section
  • a flat surface of at least some of the rods bears on some of the flat inner surfaces 501 through 512 of the packing tube 550 and a vertex of some of the other rods bears on the flat surfaces.
  • the open spaces between the rods 24 and tube 550 are primarily in the vicinity of the vertices between the flat inner surfaces 501 through 512.
  • the facets or surfaces of the multi-sided glass packing tube have different widths (the dimension transverse to the longitudinal axis of the tube 550).
  • FIG. 5 shows this feature.
  • the variation in the width of the flat surfaces depends on the size and shape of the boule to be formed. In the embodiment disclosed herein, 2 different widths are disclosed.
  • the widths surfaces 501, 503, 505, 507, 509 and 511 are the same dimension and are smaller than the widths of surfaces 502, 504, 506, 508, 510 and 512 and all of this latter group are the same dimension. For other desired boule shapes, different variations could be used.
  • a comparison between the open spaces 300 of the prior art boule shown in FIC.1 and open spaces seen in FIG. 5 shows a large reduction of open area. This reduction can easily exceed 50% when compared to the prior art boule.
  • Such reduction of open space is important because it reduces the flow of glass during the fusion process. Any level of glass flow can cause the core rods within each bundle of fibers within the boule to move. This movement of the core rods, as discussed above, has the potential to reduce the cladding dimension between each core site. If the clad glass thickness between two sites is reduced too much then there is a potential during the etching step for the clad glass to disappear completely. The absence of any clad glass between two core sites causes a missing channel wall within the plate which damages the performance of the plate.
  • the reduction in glass flow which is concomitant with the reduction in open space increases the uniformity of the cores within each hex-shaped fiber bundle within the boule. This increase in uniformity produces a superior plate as compared to prior art packing tubes formed with round interior walls.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Electron Tubes For Measurement (AREA)

Claims (13)

  1. Préforme fondue (500) destinée à être utilisée lors de la fabrication de galettes de micro-canaux, la préforme fondue (500) comportant :
    un tube d'habillage (550) formé de verre inattaquable chimiquement, ledit tube d'habillage (550) ayant une pluralité de surfaces intérieures plates (501 - 512), chacune desdites surfaces intérieures (501 - 512) étant généralement plane et s'étendant généralement parallèlement à l'axe longitudinal dudit tube d'habillage (550), et
    une pluralité de fibres optiques (10) situées à l'intérieur dudit tube d'habillage (550) formant des faisceaux multifibres (16), chacune desdites fibres optiques (10) ayant une couche de gainage (14) formée de matériau inattaquable chimiquement et une âme (12) formée de matériau attaquable chimiquement,
    ladite préforme fondue (500) incluant, en outre, une pluralité de tiges supports (24) formées de matériau inattaquable chimiquement situées entre l'intérieur dudit tube d'habillage (550) et lesdites fibres optiques (10), caractérisée en ce que lesdits faisceaux multifibres (16) et lesdites fibres optiques (10) ont une configuration hexagonale et en ce que lesdites tiges supports (24) ont sensiblement la même configuration géométrique et les mêmes dimensions extérieures que lesdits faisceaux multifibres (16), les tiges supports (24) et le tube d'habillage (550) étant fondus ensemble pour former la préforme fondue (500).
  2. Préforme (500) selon la revendication 1, caractérisée en ce que le tube d'habillage (550) et la couche de gainage (14) sont composés d'un matériau de verre dont le coefficient de dilatation est similaire.
  3. Préforme (500) selon les revendications 1 ou 2 caractérisée en ce que le matériau de verre de la couche de gainage (14) a une teneur en plomb supérieure à celle de l'âme (12).
  4. Préforme (500) selon l'une des revendications précédentes, caractérisée en ce que le tube d'habillage (550) a au moins 8 et de préférence 12 surfaces intérieures plates (501 - 512).
  5. Préforme (500) selon l'une des revendications précédentes, caractérisée en ce que la largeur des surfaces intérieures plates (501 - 512) varie.
  6. Préforme (500) selon l'une des revendications précédentes, caractérisée en ce que la largeur de chacune d'une première pluralité de surfaces intérieures plates a une première dimension et en ce que la largeur de chacune d'une seconde pluralité de surfaces intérieures plates a une seconde dimension différente de la première dimension.
  7. Préforme (500) selon la revendication 6, caractérisée en ce que la première dimension est inférieure à la seconde dimension.
  8. Procédé de formage d'une préforme fondue (500) destinée à être utilisée dans la fabrication de galettes de micro-canaux, ledit procédé comprend les étapes consistant à :
    - fournir un faisceau multifibre (16) de fibres optiques (10), chaque fibre optique (10) ayant une âme attaquable chimiquement (12) entourée d'une couche de gainage (14) inattaquable chimiquement, habiller une pluralité desdits faisceaux multifibres (16) dans un tube d'habillage (550) composé de matériau de verre qui est similaire au verre de la couche de gainage (14),
    - ledit tube d'habillage (550) ayant une pluralité de surfaces intérieures plates (501 - 512), chacune desdites surfaces intérieures (501 - 512) étant généralement plane et s'étendant généralement parallèlement à l'axe longitudinal dudit tube d'habillage (550),
    - positionner une pluralité de tiges support (24) composées de matériau inattaquable chimiquement entre lesdits faisceaux multifibres (16) et l'intérieur dudit tube d'habillage (550), et
    - lesdits faisceaux multifibres (16) de fibres optiques (10) ayant une configuration hexagonale et lesdites tiges supports (24) ayant sensiblement la même configuration géométrique que lesdits faisceaux multifibres (16),
    - fusionner lesdites fibres optiques (10), les tiges supports (24) et le tube d'habillage (550) ensemble.
  9. Procédé selon la revendication 8, caractérisé par le fait de munir le tube d'habillage (550) d'au moins 8 et de préférence 12 surfaces intérieures plates (501 - 512).
  10. Procédé selon les revendications 8 ou 9, caractérisé en ce que la largeur des surfaces intérieures plates (501 - 512) varie.
  11. Procédé selon l'une des revendications 8 à 10, caractérisé par le fait de doter la largeur de chacune de la première pluralité de surfaces intérieures plates d'une première dimension, et la largeur de chacune de la seconde pluralité de surfaces intérieures plates d'une seconde dimension différente de la première dimension.
  12. Procédé selon la revendication 11, caractérisé par le fait de sélectionner la première dimension plus petite que la seconde dimension.
  13. Galette de micro-canaux formée à partir de la préforme (500) selon l'une des revendications 1 à 7 et/ou grâce au procédé selon l'une des revendications 8 à 12.
EP20040400034 2004-07-05 2004-07-05 Dispositif et procédé pour minimiser le flux de verre dans la fabrication d'une plaque à microcanaux Expired - Fee Related EP1615254B1 (fr)

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EP20040400034 EP1615254B1 (fr) 2004-07-05 2004-07-05 Dispositif et procédé pour minimiser le flux de verre dans la fabrication d'une plaque à microcanaux

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EP20040400034 EP1615254B1 (fr) 2004-07-05 2004-07-05 Dispositif et procédé pour minimiser le flux de verre dans la fabrication d'une plaque à microcanaux

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EP1615254A1 EP1615254A1 (fr) 2006-01-11
EP1615254B1 true EP1615254B1 (fr) 2008-12-24

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Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5378955A (en) * 1971-11-08 1995-01-03 Intevac, Inc. Method for fabrication of a microchannel electron multiplier
NL7309384A (nl) * 1973-07-05 1975-01-07 Philips Nv Vezelplaat met een regelmatige stapeling van rechthoekige vezels.
NL8503053A (nl) * 1985-11-07 1987-06-01 Philips Nv Beeldvormende inrichting met vezeloptiekplaat.

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