EP0350359B1 - Verfahren zur Herstellung einer Röntgenbildverstärkerröhre und nach diesem Verfahren hergestellte Bildverstärkerröhre - Google Patents

Verfahren zur Herstellung einer Röntgenbildverstärkerröhre und nach diesem Verfahren hergestellte Bildverstärkerröhre Download PDF

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Publication number
EP0350359B1
EP0350359B1 EP89401743A EP89401743A EP0350359B1 EP 0350359 B1 EP0350359 B1 EP 0350359B1 EP 89401743 A EP89401743 A EP 89401743A EP 89401743 A EP89401743 A EP 89401743A EP 0350359 B1 EP0350359 B1 EP 0350359B1
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EP
European Patent Office
Prior art keywords
electrode
anode
photocathode
alkali metals
tube
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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 - Lifetime
Application number
EP89401743A
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English (en)
French (fr)
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EP0350359A1 (de
Inventor
Gérard Vieux
Francis Diaz
Paul De Groot
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
    • H01J31/501—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output with an electrostatic electron optic system
    • 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
    • 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
    • H01J9/14—Manufacture of electrodes or electrode systems of non-emitting 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/34—Photoemissive electrodes
    • H01J2201/342—Cathodes
    • H01J2201/3421—Composition of the emitting surface
    • H01J2201/3426—Alkaline metal compounds, e.g. Na-K-Sb

Definitions

  • the present invention relates to a method for manufacturing an improved radiological image intensifier tube (I.I.R.). It also relates to the high vacuum tubes intensifiers of radiological images thus obtained.
  • I.I.R. improved radiological image intensifier tube
  • Radiological image intensifier tubes or I.I.R. are well known in the prior art. They transform a radiological image into a visible image, for example to ensure medical observation.
  • the problem which arises and which the present invention seeks to solve is that one observes in the I.I.R. even in the absence of X-rays, annoying parasitic lighting of the observation screen.
  • This stray light is due to the alkali metals involuntarily deposited on the electrodes of the I.I.R. during the development of the photocathode.
  • the intense electric field which reigns in the tube manages to tear electrons from these alkali metals which are very electro-positive, and therefore very easily ionizable. These electrons go up the electric field, strike the observation screen and create parasitic lighting.
  • photocathodes of the alkaline antimonide type are done in the vacuum enclosure of the I.I.R. because alkali metals are very reactive and must be created under vacuum to be stable.
  • These photocathodes can be produced by successive evaporations of their constituent elements, in the tube, using a conventional crucible containing antimony, which is caused to evaporate by heating the crucible, by Joule effect for example.
  • the alkali metals are evaporated from generators usually located on the electrode closest to the anode.
  • the evaporation of alkali metals is the result of a silicothermia or an aluminothermy of the chromates of the metals that one seeks to evaporate.
  • Silicothermia or aluminothermia are triggered by heating by Joule effect of alkaline generators.
  • Alkaline generators are much less directive than antimony generators. This is due to the fact that it is necessary for silicothermia or aluminothermia to occur under good conditions to use special crucibles in which the chromates are confined. This type of crucible has poor directivity which has the advantage of ensuring a very uniform deposition of alkali metals over the entire surface of the photocathode which is distant from these crucibles. On the other hand, it has the drawback of causing the deposition of alkali metals on all the parts of the I.I.R. tube, and in particular on the electrodes, which causes the problem of stray lighting of the observation screen.
  • a solution used by the Applicant is to cover with a layer of aluminum oxide Al2O3, the electrode closest to the anode, generally made of aluminum itself.
  • This solution eliminates stray lighting from the observation screen, but introduces electrical discharges through this oxide layer, which is an electrical insulator.
  • EP-A-249 547 Another known solution to the problem mentioned, which does not have the drawbacks of the known solution, is described in EP-A-249 547 and consists in that, before introducing it into the intensifier, it is deposited, at least on a part of one or more electrodes, a layer of an electrically conductive material and having the property of oxidizing the alkali metals which enter into the composition of the photocathode.
  • This material can be chosen from the following bodies: Te, Se, S, P.
  • the present invention intends to propose a variant of this second solution which preserves the advantages of a conductive layer of electrons from the alkali metals while making its application and its implementation simpler.
  • the first object of the invention is a method of manufacturing an improved tube intensifier of radiological images, with in particular a photocathode comprising an alkaline antimonide, several electrodes and an anode, according to which, prior to the manufacture of the cathode by means of a vaporization of antimony and alkali metals, a layer of conductive material is deposited, before introducing it into the tube, on at least part of the electrode closest to the anode having the property of reacting with the above-mentioned alkali metals.
  • the conductive material is chosen from organic polymers that conduct electricity electronically.
  • a second object of the invention is an improved radiological image intensifier tube, in particular with a photocathode comprising an alkaline antimonide, several electrodes and an anode in which at least a part of at least one electrode and parts electrically connected to a electrode or at the anode of the intensifier carries a layer of organic polymer electronically conductive of electricity having the property of reacting chemically with the alkali metals which enter into the composition of the photocathode.
  • An intensifier of radiological images represented diagrammatically, seen in longitudinal section in FIG. 1, is constituted by an input screen, an electronic optical system and an observation screen contained in a vacuum enclosure 1.
  • the input screen includes a scintillator 2 which converts the incident X photons into visible photons, a photocathode 3 which converts the visible photons into electrons. Between the scintillator and the photocathode, an electrically conductive sublayer is generally inserted, the role of which is to re-supply the photocathode with electrical charges while it emits its electrons. This sublayer is not shown in FIG. 1.
  • the scintillator may consist, for example, of cesium iodide doped with sodium or with thallium.
  • the photocathode can consist of an alkaline antimonide.
  • the conductive sublayer may consist, for example, of indium oxide of formula In2O3.
  • the electronic optical system generally consists of three electrodes G1, G2, G3 and an anode A which carries the observation screen 4.
  • Photocathode 3 is generally connected to the ground of the tube.
  • the electrodes G1, G2, G3 and the anode A are brought to electrical potentials increasing up to 30 kV for example;
  • An electric field E is therefore created in the tube, directed along the longitudinal axis of the tube, towards the photocathode. Electrons from the photocathode go up this field and strike the observation screen 4, made of a cathodoluminescent material such as zinc sulfide, for example, which makes it possible to obtain a visible image.
  • the reference 7 denotes the layer of alkali metals deposited on the grid G3 during the manufacture of the cathode and which, under the action of the electric field E, prevailing between the grid G3 and the anode A and directed towards the grid G3, releases electrons which go up the electric field and come to strike the observation screen 4.
  • FIG. 3 represents a view in partial section of the electrode G3 and of the anode A of the I.I.R. of Figure 1, illustrating the solution provided by the invention to the problem of stray lighting previously mentioned.
  • the problem of stray lighting is due to the metallic nature of the parasitic alkalies.
  • the solution proposed by the invention is to chemically react these alkali metals with a material capable of transforming them into ionic or covalent compounds.
  • the alkali metals are fixed and do not release any more electrons creating the parasitic lighting which one seeks to suppress.
  • the deposit used must also conduct electricity so as to avoid the discharge phenomena encountered in the prior art when an oxide layer covers the G3 electrode.
  • the present invention it is proposed to cover one or all of the electrodes G1, G2, and G3 as well as any internal part of the tube capable of receiving alkali metals with an organic polymer that conducts electricity.
  • This conductive organic polymer may cover all or only part of the electrode or part concerned.
  • the conductive organic polymer may - by way of non-exhaustive examples - be polypyrrole, polythiophene, polyaniline, polyvinylferrocene (PVF), polythiazil, polyacethylene, polyparaphenylene, or any other electronic conductive organic polymer.
  • FIG. 3 it is shown that the electrode G rec is covered with a layer 8 of polymer before being introduced into the I.I.R. It is possible to cover the whole of the electrode G3 with polymer as is the case in FIG. 3, or only the zones of the electrode G3 which are most likely to cause the phenomenon of parasitic lighting. These areas can be determined experimentally. They can also be determined by calculation using computer programs. The zones which are most likely to cause the parasitic lighting phenomenon are generally very curved zones whose radius of curvature is small and whose electric field is strong. These areas are located near the alkaline generators and the observation screen. In FIG. 3, it can be seen that the periphery of the orifice of the electrode G3 which has allowed the passage of electrons has been covered with layer 8.
  • oxidized form is conductive
  • reduced form is insulating
  • the second method of obtaining is electrochemical oxidation in which oxidation and polymerization are carried out on the electrode connected to the positive terminal of the electric generator, the bath being composed of the basic monomer - for example pyrrole - diluted in an organic or aqueous solvent.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Electroluminescent Light Sources (AREA)

Claims (7)

  1. Verfahren zum Herstellen einer verbesserten Röntgenbildverstärkerröhre (1) mit insbesondere einer Photokathode (3), die ein Alkaliantimonid enthält, mehreren Elektroden (G₁, G₂, G₃) und einer Anode (4), bei welchem vor der Herstellung der Photokathode (3) durch Verdampfen von Antimon und von Alkalimetallen vor dem Einführen in die Röhre auf wenigstens einem Teil der Elektrode (G₃), die der Anode am nächsten liegt, eine Schicht aus einem elektronischen Stromleitermaterial (8) aufgebracht wird, das die Eigenschaft hat, mit den vorgenannten Alkalimetallen(7) zu reagieren, dadurch gekennzeichnet, daß das Leitermaterial unter den organischen Polymeren ausgewählt wird.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Polymer unter einem der folgenden ausgewählt wird: Polypyrrol, Polythiophen, Polyanilin, Polyacethylen, Polylvinylferrocen, Polythiazil, Polyparaphenylen.
  3. Verfahren nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß das Aufbringen dadurch verwirklicht wird, daß die Elektrode oder der zu überziehende Teil der Elektrode in einem Reaktionsbad angebracht wird, das eine Mischung des Basismonomers mit einem chemischen Oxidations- und Polymerisationsmittel enthält.
  4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß das chemische Oxidationsmittel als Eisenperchlorat, Eisenchlorid oder Jod gewählt wird.
  5. Verfahren nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, daß das Aufbringen durch eine elektrochemische Oxidation der Elektrode oder des zu überziehenden Teils der Elektrode verwirklicht wird, wobei letztere die Anode des elektrolytischen Reaktors bildet, in dem der Elektrolyt eine wäßrige oder organische Lösung des Basismonomers ist.
  6. Verbesserte Röntgenbildverstärkerröhre mit insbesondere einer Photokathode (3), die ein Alkaliantimonid enthält, mehreren Elektroden (G₁, G₂, G₃) und einer Anode (4), in welcher wenigstens ein Teil einer Elektrode und elektrisch mit einer Elektrode oder der Anode der Verstärkerröhre verbundene Teile eine Schicht (8) aus einem elektronischen Stromleitermaterial tragen, das die Eigenschaft hat, chemisch mit den Alkalimetallen (7) zu reagieren, die in die Verbindung der Photokathode eintreten, dadurch gekennzeichnet, daß das Leitermaterial ein organisches Polymer ist.
  7. Verbesserte Röhre nach Anspruch 6, dadurch gekennzeichnet, daß dieses organische Polymer unter den folgenden Polymeren gewählt ist: Polypyrrol, Polythiophen, Polyanilin, Polyacethylen, Polyvinylferrocen, Polythiazil, Polyparaphenylen.
EP89401743A 1988-07-08 1989-06-20 Verfahren zur Herstellung einer Röntgenbildverstärkerröhre und nach diesem Verfahren hergestellte Bildverstärkerröhre Expired - Lifetime EP0350359B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8809310 1988-07-08
FR8809310A FR2634057B1 (fr) 1988-07-08 1988-07-08 Procede de fabrication d'un tube perfectionne intensificateur d'images radiologiques, tube intensificateur ainsi obtenu

Publications (2)

Publication Number Publication Date
EP0350359A1 EP0350359A1 (de) 1990-01-10
EP0350359B1 true EP0350359B1 (de) 1993-08-25

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EP89401743A Expired - Lifetime EP0350359B1 (de) 1988-07-08 1989-06-20 Verfahren zur Herstellung einer Röntgenbildverstärkerröhre und nach diesem Verfahren hergestellte Bildverstärkerröhre

Country Status (5)

Country Link
US (1) US4943254A (de)
EP (1) EP0350359B1 (de)
JP (1) JPH0268832A (de)
DE (1) DE68908637T2 (de)
FR (1) FR2634057B1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02152143A (ja) * 1988-12-02 1990-06-12 Toshiba Corp Ｘ線イメージ管及びその製造方法
FR2688343A1 (fr) * 1992-03-06 1993-09-10 Thomson Tubes Electroniques Tube intensificateur d'image notamment radiologique, du type a galette de microcanaux.
FR2698482B1 (fr) * 1992-11-20 1994-12-23 Thomson Tubes Electroniques Dispositif générateur d'images par effet de luminescence.
FR2700889B1 (fr) * 1993-01-22 1995-02-24 Thomson Tubes Electroniques Tube convertisseur d'images, et procédé de suppression des lueurs parasites dans ce tube.
GB9603197D0 (en) * 1996-02-15 1996-04-17 Gen Electric Electrodeless discharge lamp
FR2777112B1 (fr) 1998-04-07 2000-06-16 Thomson Tubes Electroniques Dispositif de conversion d'une image
FR2782388B1 (fr) 1998-08-11 2000-11-03 Trixell Sas Detecteur de rayonnement a l'etat solide a duree de vie accrue

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2212579A1 (de) * 1972-03-15 1973-09-27 Siemens Ag Vakuum-bildwandler
JPS5736758A (en) * 1980-08-14 1982-02-27 Nec Corp Image tube
FR2600177B1 (fr) * 1986-06-13 1988-08-19 Thomson Csf Procede de fabrication d'un intensificateur d'images radiologiques et intensificateur d'images radiologiques ainsi obtenu

Also Published As

Publication number Publication date
FR2634057B1 (fr) 1991-04-19
US4943254A (en) 1990-07-24
EP0350359A1 (de) 1990-01-10
JPH0268832A (ja) 1990-03-08
DE68908637D1 (de) 1993-09-30
FR2634057A1 (fr) 1990-01-12
DE68908637T2 (de) 1993-12-23

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