EP0249547A2 - Method for making an X-ray image intensifier, and image intensifier so obtained - Google Patents
Method for making an X-ray image intensifier, and image intensifier so obtained Download PDFInfo
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- EP0249547A2 EP0249547A2 EP87401281A EP87401281A EP0249547A2 EP 0249547 A2 EP0249547 A2 EP 0249547A2 EP 87401281 A EP87401281 A EP 87401281A EP 87401281 A EP87401281 A EP 87401281A EP 0249547 A2 EP0249547 A2 EP 0249547A2
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- intensifier
- photocathode
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- alkali metals
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/32—Secondary emission electrodes
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- 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 of manufacturing a radiological image intensifier. It also relates to the radiological image intensifiers thus obtained.
- 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.
- an IIR which is represented schematically, seen in longitudinal section in FIG. 1, consists of 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, of formula for example Sb Cs3, Sb K3, Sb K2 Cs .
- the conductive undercoat can consist, for example, of indium oxide of formula In2 03.
- 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. It is therefore created in the tube an electric field E, directed along the longitudinal axis of the tube, towards the photocathode.
- the electrons from the photocathode go up this field and strike the observation screen 4, made of a cathodoluminescent material such as zinc sulphide for example, which makes it possible to obtain a visible image.
- the problem which arises and which the present invention seeks to solve is that one observes in the IIR, even in the absence of X-ray, a disturbing parasitic lighting of the observation screen.
- This stray light is due to the alkali metals involuntarily deposited on the IIR electrodes 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.
- FIG. 2 represents a partial section view of the grid G3 and of the anode A of the IIR in FIG. 1.
- the reference to the layer of alkali metals deposited on the grid G3 denotes the reference 7 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.
- photocathodes of the alkaline antimonide type are done in the vacuum chamber of the IIR because the 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.
- an antimony generator which is constituted by a usual crucible containing antimony, which is caused to evaporate by heating the crucible, by Joule effect for example.
- the antimony generator 5 is generally placed close to the photocathode and on the electron path as shown in FIG. 1, which explains why it is generally removed from the enclosure, once the photocathode is finished.
- Metals alkalines are evaporated from alkaline generators 6 generally located on the electrode G3, which is closest to the anode A, as shown in FIG. 1.
- the alkaline generators are generally left in the vacuum enclosure once the photocathode is finished. We know of IIR manufacturing processes in which the alkaline generators are not carried by the electrode G3 and are removed from the vacuum enclosure, once the photocathode is finished.
- 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 Joule heating 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 6. It does, however, have the disadvantage of causing the deposition of alkali metals on all parts of the IIR tube, and in particular on the electrodes G1, G2 and G3 which leads to the problem of stray lighting of the observation screen.
- a solution used by the Applicant is to cover with an oxide layer the electrode G3, generally made of aluminum.
- This solution eliminates stray lighting from the observation screen, but introduces discharges through this oxide layer.
- the IIR When the IIR receives X-radiation, part of the electrons from the photocathode falls on the G3 electrode. As the G3 electrode is covered with an oxide layer, these electrons do not flow and there are discharges through the layer oxide.
- the present invention provides a solution to the problem mentioned which does not have the drawbacks of the known solution.
- the subject of the present invention is a method of manufacturing a radiological image intensifier, comprising in particular a photocathode consisting of an alkaline antimonide, several grids and an anode, characterized in that a layer of a conductive material of the electricity and having the property of oxidizing the alkali metals which enter into the composition of the photocathode is deposited at least on a part of the grid which is closest to the anode before introducing it into the intensifier.
- FIG. 3 represents a view in partial section of the grid G3 and of the anode A of the IIR of FIG. 1, illustrating the solution provided by the invention to the problem of the parasitic 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 oxidizing them and 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 invention proposes to use to cover the G3 electrode of the IIR, before introducing it into the IIR, preferably, one of the following elements: selenium, tellurium, sulfur, arsenic, phosphorus, antimony. ..
- the electrode G3 is covered with a layer 8, tellurium for example, before being introduced into the IIR. It is possible to cover the whole of the electrode G3 with tellurium or, as is the case in FIG. 3, only the zones of the electrode G3 which are most likely to cause the phenomenon of stray 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 phenomenon of parasitic lighting 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 Figure 3, we see that we have covered with layer 8 the periphery of the orifice of the grid G permet which allows the passage of electrons.
- layer 8 which is sufficiently conductive, there is no problem of discharge.
- this layer 8 there are also compounds of this layer and alkali metals, but whether these compounds are conductive or not, does not change the fact that layer 8 is sufficiently conductive so that there is no discharge and breakdown problem.
- the layer 8 of electrically conductive material and having the property of oxidizing the alkalis is deposited at least on the electrode G3, which generally carries the alkaline generators and, which is closest to the anode.
- this layer 8 is also deposited on the grid G2.
- this layer 8 the grid G1, as well as more generally any part of the IIR which must be electrically connected to an electrode of the IIR, that is to say at one of the grids or at the anode.
- One of these methods consists in depositing layer 8 by evaporation by heating by Joule effect a crucible containing the product to be deposited and causing condensation of the vapors coming from the crucible on the surfaces to be covered with layer 8.
- Another method consists in dipping the parts to be covered with layer 8 in a reactive chemical bath which contains the product to be deposited.
- Another process is electrolysis.
- the part to covering is an electrode immersed in an electrolysis bath.
- the deposition of layer 8 can also be carried out by sputtering or by using a plasma.
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Abstract
L'invention concerne un procédé de fabrication d'un intensificateur d'images radiologiques.Avant de l'introduire dans l'intensificateur, on recouvre la grille (G₃) qui est la plus proche de l'anode (A) d'une couche d'un matériau, conducteur de l'électricité, et ayant la propriété d'oxyder les métaux alcalins. On supprime ainsi l'éclairage parasite de l'écran dobservation (4) dû aux métaux alcalins déposés involontairement sur cette grille (G₃) lors de l'élaboration de la photocathode (3).The invention relates to a method for manufacturing a radiological image intensifier. Before introducing it into the intensifier, the grid (G₃) which is closest to the anode (A) is covered with a layer of a material that conducts electricity and has the property of oxidizing alkali metals. This eliminates the parasitic lighting of the observation screen (4) due to the alkali metals unintentionally deposited on this grid (G₃) during the development of the photocathode (3).
Description
La présente invention concerne un procédé de fabrication d'un intensificateur d'images radiologiques. Elle concerne également les intensificateurs d'images radiologiques ainsi obtenus.The present invention relates to a method of manufacturing a radiological image intensifier. It also relates to the radiological image intensifiers thus obtained.
Les tubes intensificateurs d'images radiologiques ou I.I.R. sont bien connus de l'Art Antérieur. Ils transforment une image radiologique en image visible, par exemple pour assurer l'observation médicale.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.
On rappelle qu'un IIR, qui est représenté de façon schématique, vu en coupe longitudinale sur la figure 1, est constitué par un écran d'entrée, un système d'optique électronique et un écran d'observation contenus dans une enceinte à vide 1.It will be recalled that an IIR, which is represented schematically, seen in longitudinal section in FIG. 1, consists of an input screen, an electronic optical system and an observation screen contained in a vacuum enclosure 1.
L'écran d'entrée comporte un scintillateur 2 qui convertit les photons X incidents en photons visibles, une photocathode 3 qui convertit les photons visibles en électrons. Entre le scintillateur et la photocathode, est généralement intercalée une sous-couche conductrice de l'électricité dont le rôle est de ré-approvisionner la photocathode en charges électriques pendant qu'elle émet ses électrons. Cette sous-couche n'est pas représentée sur la figure 1.The input screen includes a
Le scintillateur peut être constitué, par exemple, d'iodure de césium dopé au sodium ou au thallium. La photocathode peut être constituée d'un antimoniure alcalin, de formule par exemple Sb Cs₃, Sb K₃, Sb K₂ Cs .....La sous-couche conductrice peut être constituée, par exemple, d'oxyde d'indium de formule In₂ 0₃.The scintillator may consist, for example, of cesium iodide doped with sodium or with thallium. The photocathode can consist of an alkaline antimonide, of formula for example Sb Cs₃, Sb K₃, Sb K₂ Cs ..... The conductive undercoat can consist, for example, of indium oxide of formula In₂ 0₃.
Le système d'optique électronique est constitué généralement de trois électrodes G₁, G₂, G₃ et d'une anode A qui porte l'écran d'observation 4.The electronic optical system generally consists of three electrodes G₁, G₂, G₃ and an anode A which carries the
La photocathode 3 est généralement reliée à la masse du tube. Les électrodes G₁, G₂, G₃ et l'anode A sont portées à des potentiels électriques croissant jusqu'à de 30 KV par exemple. Il se crée donc dans le tube un champ électrique E, dirigé selon l'axe longitudinal du tube, vers la photocathode. Les électrons issus de la photocathode remontent ce champ et viennent frapper l'écran d'observation 4, constitué d'un matériau cathodoluminescent tel que du sulfure de zinc par exemple, ce qui permet d'obtenir une image visible.
Le problème qui se pose et que la présente invention cherche à résoudre est qu'on l'on observe dans les IIR, même en l'absence de rayonnement X, un éclairage parasite gênant de l'écran d'observation. Cet éclairage parasite est dû aux métaux alcalins déposés involontairement sur les électrodes de l'IIR lors de l'élaboration de la photocathode. Le champ électrique intense qui règne dans le tube parvient à arracher des électrons à ces métaux alcalins qui sont très électro-positifs, et donc très facilement ionisables. Ces électrons remontent le champ électrique, viennent percuter l'écran d'observation et créent un éclairage parasite.The problem which arises and which the present invention seeks to solve is that one observes in the IIR, even in the absence of X-ray, a disturbing parasitic lighting of the observation screen. This stray light is due to the alkali metals involuntarily deposited on the IIR electrodes 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.
Ce phénomène est illustré sur la figure 2 qui représente une vue en coupe partielle de la grille G₃ et de l'anode A de l'IIR de la figure 1. On désigne par la référence 7 la couche de métaux alcalins déposée sur la grille G₃ et qui, sous l'action du champ électrique E, règnant entre la grille G₃ et l'anode A et dirigé vers la grille G₃, libère des électrons qui remontent le champ électrique et viennent percuter l'écran d'observation 4.This phenomenon is illustrated in FIG. 2 which represents a partial section view of the grid G₃ and of the anode A of the IIR in FIG. 1. The reference to the layer of alkali metals deposited on the grid G₃ denotes the
Il faut savoir que la fabrication des photocathodes du type antimoniure alcalin se fait dans l'enceinte à vide de l'IIR car les métaux alcalins sont très réactifs et doivent être créés sous vide pour être stables. Ces photocathodes peuvent être réalisées par évaporations successives de leurs éléments constitutifs. A cet effet, on dispose dans le tube, un générateur d'antimoine qui est constitué par un creuset usuel contenant de l'antimoine, dont on provoque l'évaporation en chauffant le creuset, par effet Joule par exemple. Le générateur d'antimoine 5 est généralement placé à proximité de la photocathode et sur le trajet des électrons comme cela est représenté sur la figure 1, ce qui explique qu'on l'enlève généralement de l'enceinte, une fois la photocathode terminée. Les métaux alcalins sont évaporés à partir de générateurs alcalins 6 situés généralement sur l'électrode G₃, qui est la plus proche de l'anode A, comme cela est représenté sur la figure 1.You should know that the manufacture of photocathodes of the alkaline antimonide type is done in the vacuum chamber of the IIR because the 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. For this purpose, there is in the tube, an antimony generator which is constituted by a usual crucible containing antimony, which is caused to evaporate by heating the crucible, by Joule effect for example. The antimony generator 5 is generally placed close to the photocathode and on the electron path as shown in FIG. 1, which explains why it is generally removed from the enclosure, once the photocathode is finished. Metals alkalines are evaporated from alkaline generators 6 generally located on the electrode G₃, which is closest to the anode A, as shown in FIG. 1.
On laisse généralement les générateurs d'alcalins dans l'enceinte à vide une fois la photocathode terminé. On connait des procédés de fabrication d'IIR dans lesquels les générateurs d'alcalins ne sont pas portés par l'électrode G₃ et sont enlevés de l'enceinte à vide, une fois la photocathode terminés.The alkaline generators are generally left in the vacuum enclosure once the photocathode is finished. We know of IIR manufacturing processes in which the alkaline generators are not carried by the electrode G₃ and are removed from the vacuum enclosure, once the photocathode is finished.
L'évaporation des métaux alcalins est le résultat d'une silicothermie ou d'une aluminothermie des chromates des métaux que l'on cherche à évaporer. La silicothermie ou l'aluminothermie sont déclenchées par le chauffage par effet Joule des générateurs alcalins.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 Joule heating of alkaline generators.
Les générateur alcalins sont beaucoup moins directifs que les générateurs d'antimoine. Cela est dû au fait qu'il est nécessaire pour que la silicothermie ou l'aluminothermie se produisent dans de bonnes conditions d'utiliser des creusets particuliers dans lesquels les chromates sont confinés. Ce type de creuset présente une mauvaise directivité qui a l'avantage d'assurer un dépôt bien uniforme des métaux alcalins sur toute la surface de la photocathode qui est éloignée de ces creusets 6. Il a par contre l'inconvénient de provoquer le dépôt de métaux alcalins sur toutes les pièces du tube IIR, et notamment sur les électrodes G₁, G₂ et G₃ ce qui entraîne le problème de l'éclairage parasite de l'écran d'observation.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 6. It does, however, have the disadvantage of causing the deposition of alkali metals on all parts of the IIR tube, and in particular on the electrodes G₁, G₂ and G₃ which leads to the problem of stray lighting of the observation screen.
Pour résoudre ce problème, une solution utilisée par la Demanderesse est de recouvrir d'une couche d'oxyde l'électrode G₃, généralement en aluminium.To solve this problem, a solution used by the Applicant is to cover with an oxide layer the electrode G₃, generally made of aluminum.
Cette solution permet de supprimer l'éclairage parasite de l'écran d'observation, mais introduit des décharges à travers cette couche d'oxyde.This solution eliminates stray lighting from the observation screen, but introduces discharges through this oxide layer.
Lorsque l'IIR reçoit un rayonnement X, une partie des électrons issus de la photocathode tombe sur l'électrode G₃. Comme l'électrode G₃ est recouverte d'une couche d'oxyde, ces électrons ne s'écoulent pas et il se produit des décharges à travers la couche d'oxyde.When the IIR receives X-radiation, part of the electrons from the photocathode falls on the G₃ electrode. As the G₃ electrode is covered with an oxide layer, these electrons do not flow and there are discharges through the layer oxide.
La présente invention propose une solution au problème évoqué qui ne présente pas les inconvénients de la solution connue.The present invention provides a solution to the problem mentioned which does not have the drawbacks of the known solution.
La présente invention a pour objet un procédé de fabrication d'un intensificateur d'images radiologiques, comportant notamment une photocathode constituée d'un antimoniure alcalin, plusieurs grilles et une anode, caractérisé en ce qu'une couche d'un matériau conducteur de l'électricité et ayant la propriété d'oxyder les métaux alcalins qui entrent dans la composition de la photocathode est déposée au moins sur une partie de la grille qui est la plus proche de l'anode avant de l'introduire dans l'intensificateur.The subject of the present invention is a method of manufacturing a radiological image intensifier, comprising in particular a photocathode consisting of an alkaline antimonide, several grids and an anode, characterized in that a layer of a conductive material of the electricity and having the property of oxidizing the alkali metals which enter into the composition of the photocathode is deposited at least on a part of the grid which is closest to the anode before introducing it into the intensifier.
D'autres objets, caractéristiques et résultats de l'invention ressortiront de la description suivante, donnée à titre d'exemple non limitatif et illustrée par les figures annexées qui représentent :
- - la figure 1, une vue en coupe longitudinale d'un IIR ;
- - les figures 2 et 3, des vues en coupe de la grille G₃ et de l'anode A de l'IIR de la figure 1 illustrant la solution connue selon l'Art Antérieur et la solution apportée par l'invention.
- - Figure 1, a longitudinal sectional view of an IIR;
- - Figures 2 and 3, sectional views of the grid G₃ and the anode A of the IIR of Figure 1 illustrating the known solution according to the prior art and the solution provided by the invention.
Sur les différentes figures, les mêmes repères désignent les mêmes éléments, mais, pour des raisons de clarté, les cotes et proportions des divers éléments ne sont pas respectées.In the different figures, the same references designate the same elements, but, for reasons of clarity, the dimensions and proportions of the various elements are not observed.
Les figures 1 et 2 ont été décrites dans l'introduction à la description.Figures 1 and 2 have been described in the introduction to the description.
La figure 3 représente une vue en coupe partielle de la grille G₃ et de l'anode A de l'IIR de la figure 1, illustrant la solution apportée par l'invention au problème de l'éclairage parasite précédemment évoqué.FIG. 3 represents a view in partial section of the grid G₃ and of the anode A of the IIR of FIG. 1, illustrating the solution provided by the invention to the problem of the parasitic lighting previously mentioned.
Selon l'invention, avant de l'introduire dans l'enceinte à vide de l'IIR, on dépose sur la grille G₃ sur laquelle sont généralement fixés les générateurs d'antimoine, une couche d'un matériau conducteur de l'électricité ayant la propriété d'oxyder les métaux alcalins.According to the invention, before introducing it into the IIR vacuum enclosure, a layer of an electrically conductive material having a layer of electrically conductive material deposited on the grid G₃ on which the antimony generators are generally fixed the property of oxidizing alkali metals.
Le problème de l'éclairage parasite est dû à la nature métallique des alcalins parasitaires. La solution proposée par l'invention est de faire réagir chimiquement ces métaux alcalins avec un matériau capable de les oxyder et de les transformer en composés ioniques ou covalents. Ainsi les métaux alcalins sont fixés et ne libèrent plus d'électrons créant l'éclairage parasite que l'on cherche à supprimer. Le dépôt utilisé doit être de plus conducteur de l'électricité de façon à éviter les phénomènes de décharge rencontrés dans l'Art Antérieur lorsqu'une couche d'oxyde recouvre l'électrode G₃.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 oxidizing them and transforming them into ionic or covalent compounds. Thus 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.
L'invention propose d'utiliser pour recouvrir l'électrode G₃ de l'IIR, avant de l'introduire dans l'IIR, de préférence, l'un des éléments suivants :sélénium, tellure, soufre, arsenic, phosphore, antimoine...The invention proposes to use to cover the G₃ electrode of the IIR, before introducing it into the IIR, preferably, one of the following elements: selenium, tellurium, sulfur, arsenic, phosphorus, antimony. ..
On peut utiliser ces éléments seuls ou sous forme de composés ayant par exemple l'une des formules suivantes : Pb Te, Cd Te, Zn Te, In Te, Pb Se, Cd Se, Zn Se, In Se, Pb S, Cd S, Zn S, Zn₃ P₂...These elements can be used alone or in the form of compounds having for example one of the following formulas: Pb Te, Cd Te, Zn Te, In Te, Pb Se, Cd Se, Zn Se, In Se, Pb S, Cd S , Zn S, Zn₃ P₂ ...
Sur la figure 3 on montre que l'électrode G₃ est recouverte d'une couche 8, de tellure par exemple, avant d'être introduite dans l'IIR. On peut recouvrir la totalité de l'électrode G₃ de tellure ou, comme c'est le cas sur la figure 3, uniquement les zones de l'électrode G₃ qui sont les plus susceptibles de provoquer le phénomène d'éclairage parasite. Ces zones peuvent être déterminées expérimentalement. Elles peuvent aussi être déterminées par le calcul en utilisant des programmes d'ordinateurs. Les zones qui sont les plus susceptibles de provoquer le phénomène d'éclairage parasite sont généralement des zones très courbées dont le rayon de courbure est faible et dont le champ électrique est fort. Ces zones sont situées à proximité des générateurs d'alcalins et de l'écran d'observation. Sur la figure 3, on voit qu'on a recouvert de la couche 8 la périphérie de l'orifice de la grille G₃ qui permet le passage des électrons.In Figure 3 we show that the electrode G₃ is covered with a
L'arrivée d'alcalins parasitaires lors de la fabrication de la photocathode provoque la réaction suivante à la surface de la couche 8 de tellure dans le cas où du césium est évaporé :
2 Cs + Te → Cs₂ TeThe arrival of parasitic alkalis during the manufacture of the photocathode causes the following reaction on the surface of the
2 Cs + Te → Cs₂ Te
On ne retrouve donc pas sur la couche 8 de métaux alcalins mais des composés comportant ces alcalins.Thus, on
Du fait de ces composés, tel celui de formule Cs₂ Te, malgré le champ électrique existant entre la grille G₃ et la cathode, on n'observe plus d'émission d'électrons provoquant un éclairage parasite de l'écran d'observation.Because of these compounds, such as that of formula Cs₂ Te, despite the electric field existing between the gate G₃ and the cathode, no more emission of electrons is observed causing parasitic lighting of the observation screen.
De plus, du fait de la présence de la couche 8, qui est suffisament conductrice, il n'y a pas de problème de décharge. Dans cette couche 8, il y a aussi des composés de cette couche et des métaux alcalins, mais que ces composés soient conducteurs ou non, ne change pas le fait que la couche 8 soit suffisamment conductrice pour qu'il n'y ait pas de problème de décharge et de claquage.In addition, due to the presence of
A titre d'exemple, lorsqu'on évapore du césium et que la couche 8 est en tellure de plomb, la réaction est la suivante :
2Cs + Pb Te → Cs₂ Te + < <Pb> >Pb Te As an example, when cesium is evaporated and
2Cs + Pb Te → Cs₂ Te + <<Pb>> Pb Te
Il y a donc génération de plomb qui reste dissout dans la couche 8 en tellure de plomb.There is therefore generation of lead which remains dissolved in
On dépose la couche 8 de matériau conducteur de l'électricité et ayant la propriété d'oxyder les alcalins au moins sur l'électrode G₃, qui porte généralement les générateurs alcalins et, qui est la plus proche de l'anode.The
Pour supprimer plus complètement l'éclairement parasite de l'écran d'observation, on dépose aussi cette couche 8 sur la grille G₂.To more completely remove the stray light from the observation screen, this
On peut par mesure de précaution recouvrir également de cette couche 8 la grille G₁, ainsi que d'une façon plus générale toute pièce de l'IIR qui doit être reliée électriquement à une électrode de l'IIR, c'est-à-dire à l'une des grilles ou à l'anode.As a precaution, it is also possible to cover with this
Pour déposer la couche 8, divers procédés sont utilisables.To
L'un de ces procédés consiste à déposer la couche 8 par évaporation en chauffant par effet Joule un creuset contenant le produit à déposer et en provoquant la condensation des vapeurs issues du creuset sur les surfaces à recouvrir de la couche 8.One of these methods consists in depositing
Un autre procédé consiste à tremper les pièces à recouvrir de la couche 8 dans un bain chimique réactif qui comporte le produit à déposer.Another method consists in dipping the parts to be covered with
Un autre procédé est l'électrolyse. Dans ce cas la pièce à recouvrir constitue une électrode plongeant dans un bain d'électrolyse.Another process is electrolysis. In this case the part to covering is an electrode immersed in an electrolysis bath.
Le dépôt de la couche 8 peut être aussi réalisé par pulvérisation cathodique ou en utilisant un plasma.The deposition of
Tous les procédés qui viennent d'être évoqués pour déposer la couche 8 sont bien connus et leur liste n'est pas limitative.All the processes which have just been mentioned for depositing
Comme cela a été expliqué précédemment, on peut sans inconvénient déposer la couche 8 sur la totalité des grilles G₁, G₂, G₃ et des pièces reliées électriquement à une électrode de l'IIR ou seulement sur une partie de ces grilles et de ces pièces.As has been explained previously, it is possible without depositing
Claims (12)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8608588 | 1986-06-13 | ||
| FR8608588A FR2600177B1 (en) | 1986-06-13 | 1986-06-13 | METHOD FOR MANUFACTURING A RADIOLOGICAL IMAGE INTENSIFIER AND RADIOLOGICAL IMAGE INTENSIFIER THUS OBTAINED |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0249547A2 true EP0249547A2 (en) | 1987-12-16 |
| EP0249547A3 EP0249547A3 (en) | 1988-01-13 |
| EP0249547B1 EP0249547B1 (en) | 1990-01-10 |
Family
ID=9336316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87401281A Expired - Lifetime EP0249547B1 (en) | 1986-06-13 | 1987-06-05 | Method for making an x-ray image intensifier, and image intensifier so obtained |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4862006A (en) |
| EP (1) | EP0249547B1 (en) |
| JP (1) | JPH0821335B2 (en) |
| DE (1) | DE3761405D1 (en) |
| FR (1) | FR2600177B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0350359A1 (en) * | 1988-07-08 | 1990-01-10 | Thomson-Csf | Method for making an X-ray image intensifier tube, image intensifier tube so obtained |
| FR2650438A1 (en) * | 1989-07-28 | 1991-02-01 | Thomson Tubes Electroniques | Method of manufacture of an improved image intensifier tube, image intensifier tube thus obtained |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5958920A (en) * | 1982-09-28 | 1984-04-04 | Fujitsu Ltd | Buffer circuit |
| US5306907A (en) * | 1991-07-11 | 1994-04-26 | The University Of Connecticut | X-ray and gamma ray electron beam imaging tube having a sensor-target layer composed of a lead mixture |
| FR2700889B1 (en) * | 1993-01-22 | 1995-02-24 | Thomson Tubes Electroniques | Image converter tube, and method for suppressing stray light in this tube. |
| FR2782388B1 (en) | 1998-08-11 | 2000-11-03 | Trixell Sas | SOLID STATE RADIATION DETECTOR WITH INCREASED LIFE |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2168553A3 (en) * | 1972-01-21 | 1973-08-31 | Varian Associates | |
| FR2176850A1 (en) * | 1972-03-20 | 1973-11-02 | Siemens Ag | |
| GB2149200A (en) * | 1983-09-06 | 1985-06-05 | Hamamatsu Photonics Kk | Imaging and streaking tubes |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1585625A (en) * | 1968-07-02 | 1970-01-30 | Thomson Csf | |
| FR2119203A5 (en) * | 1970-12-23 | 1972-08-04 | Thomson Csf | |
| US4069121A (en) * | 1975-06-27 | 1978-01-17 | Thomson-Csf | Method for producing microscopic passages in a semiconductor body for electron-multiplication applications |
| FR2335056A1 (en) * | 1975-09-12 | 1977-07-08 | Thomson Csf | DEVICE FOR DISPLAYING INFORMATION GIVEN IN THE FORM OF RADIATED ENERGY |
| FR2345815A1 (en) * | 1976-01-30 | 1977-10-21 | Thomson Csf | NEW SOLID IONIZING RADIATION DETECTOR |
| FR2344132A1 (en) * | 1976-03-09 | 1977-10-07 | Thomson Csf | SEMICONDUCTOR IONIZING RADIATION DETECTOR |
| FR2351422A1 (en) * | 1976-05-14 | 1977-12-09 | Thomson Csf | DETECTOR DEVICE, SOLID LOCATOR OF IONIZING RADIATION IMPACTS |
| FR2352346A1 (en) * | 1976-05-18 | 1977-12-16 | Thomson Csf | NEW SCINTIGRAPHY SHOOTING SET |
| FR2361790A1 (en) * | 1976-08-10 | 1978-03-10 | Thomson Csf | DEVICE WITH SEMICONDUCTOR ELEMENTS FOR THE DISPLAY OF AN ELECTRIC SIGNAL |
| FR2502842A1 (en) * | 1981-03-27 | 1982-10-01 | Thomson Csf | IMAGE INTENSIFIER TUBE TARGET AND VIDEO OUTPUT INTENSIFICATION TUBE PROVIDED WITH SUCH TARGET |
| US4475059A (en) * | 1982-06-01 | 1984-10-02 | International Telephone And Telegraph Corporation | Image intensifier tube with reduced veiling glare and method of making same |
-
1986
- 1986-06-13 FR FR8608588A patent/FR2600177B1/en not_active Expired
-
1987
- 1987-06-05 DE DE8787401281T patent/DE3761405D1/en not_active Expired - Fee Related
- 1987-06-05 EP EP87401281A patent/EP0249547B1/en not_active Expired - Lifetime
- 1987-06-12 JP JP62146821A patent/JPH0821335B2/en not_active Expired - Lifetime
- 1987-06-15 US US07/061,980 patent/US4862006A/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2168553A3 (en) * | 1972-01-21 | 1973-08-31 | Varian Associates | |
| FR2176850A1 (en) * | 1972-03-20 | 1973-11-02 | Siemens Ag | |
| GB2149200A (en) * | 1983-09-06 | 1985-06-05 | Hamamatsu Photonics Kk | Imaging and streaking tubes |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0350359A1 (en) * | 1988-07-08 | 1990-01-10 | Thomson-Csf | Method for making an X-ray image intensifier tube, image intensifier tube so obtained |
| FR2634057A1 (en) * | 1988-07-08 | 1990-01-12 | Thomson Csf | METHOD FOR MANUFACTURING AN INTENSIFYING INTENSIFIER TUBE OF RADIOLOGICAL IMAGES, INTENSIFIER TUBE SO OBTAINED |
| US4943254A (en) * | 1988-07-08 | 1990-07-24 | Thomson-Csf | Method for the fabrication of an improved X-ray image intensifier tube, and intensifier tube, and intensifier tube obtained thereby |
| FR2650438A1 (en) * | 1989-07-28 | 1991-02-01 | Thomson Tubes Electroniques | Method of manufacture of an improved image intensifier tube, image intensifier tube thus obtained |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2600177A1 (en) | 1987-12-18 |
| FR2600177B1 (en) | 1988-08-19 |
| EP0249547B1 (en) | 1990-01-10 |
| JPH0821335B2 (en) | 1996-03-04 |
| EP0249547A3 (en) | 1988-01-13 |
| US4862006A (en) | 1989-08-29 |
| JPS63935A (en) | 1988-01-05 |
| DE3761405D1 (en) | 1990-02-15 |
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