EP0319378B1 - Manufacturing process of a radiation detector - Google Patents

Manufacturing process of a radiation detector Download PDF

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Publication number
EP0319378B1
EP0319378B1 EP88402958A EP88402958A EP0319378B1 EP 0319378 B1 EP0319378 B1 EP 0319378B1 EP 88402958 A EP88402958 A EP 88402958A EP 88402958 A EP88402958 A EP 88402958A EP 0319378 B1 EP0319378 B1 EP 0319378B1
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EP
European Patent Office
Prior art keywords
sheet
detector
enclosure
fixing
window
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EP88402958A
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German (de)
French (fr)
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EP0319378A1 (en
Inventor
Joseph Bost
Jean-Jaques Gagelin
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/001—Details
    • H01J47/002—Vessels or containers
    • H01J47/004—Windows permeable to X-rays, gamma-rays, or particles

Definitions

  • the invention relates to a method of manufacturing a radiation detector such as an ionization detector, that is to say an ionization chamber, and more particularly, the entry window of such a detector.
  • a radiation detector such as an ionization detector, that is to say an ionization chamber, and more particularly, the entry window of such a detector.
  • This type of detector is used in particular in dosimetry, medical tomography, radiology and for non-destructive testing, where the detection of radiation intended for imaging such as X-rays is used.
  • a method according to the first part of claim 1 is known from EP-A-0 127 074.
  • An ionization detector has an entry window, through which the incident rays penetrate, to be detected inside a sealed enclosure of the detector containing an ionizable fluid under pressure.
  • This window must be as thin as possible to have good transparency to radiation, nevertheless taking into account the fact that it is a question of closing the sealed enclosure under pressure.
  • the window must also be very homogeneous, to ensure a good uniformity of the response of the detector.
  • a first type of detector comprises a sealed enclosure 2, inside which is placed a detection assembly made up of conductive plates 4, delimiting one, or as in FIG. 1 , several detector cells.
  • the technique used here to obtain an entry window is to cut it in the mass from an ingot 6.
  • the main drawback of this type of window is due to the lack of homogeneity of the base material. Indeed, it is risky to cut, by milling for example, a thin window for example less than 3 mm for aluminum and its alloys, under penalty of having to reject the part due to leakage or crack.
  • a second disadvantage is that after machining of this type, the internal constraints of the ingot can be released, which affects the precision of a window intended for a gas-tight assembly.
  • US-A-4 622 466 describes another type of X-ray detector, comprising a sealed enclosure under pressure.
  • This detector uses an entrance window with a multilayer structure, associating a metal sheet with a carbon fiber sheet, as well as an elastic insulation sheet which can be made of polyaramide.
  • This technique is more complex than the previous one, and is more expensive by the diversity of the materials involved and their assembly.
  • the detector having to be used under very variable conditions, temperature differences give rise to constraints in the multilayer structure. These constraints affect the homogeneity and efficiency of the entry window.
  • the object of the invention is to avoid the abovementioned drawbacks, by proposing a method of manufacturing a detector provided with a simple entry window and of lower production cost.
  • the main object of the invention is a method of manufacturing a radiation detector according to claim 1, the detector comprising a sealed enclosure containing a fluid under determined operating pressure and in which is disposed a set of detection, an entrance window of the sealed enclosure through which the radiation enters the sealed enclosure, and means for fixing the entrance window on the sealed enclosure.
  • This detector comprises an entry window formed by a preformed sheet, with a deformation greater than or equal to the deformation obtained by the same non-preformed sheet and subjected to the operating pressure of the detector. In this way, the stress field exerted by the operating pressure of the detector on the preformed sheet remains in the elastic range, which guarantees the geometric stability of this sheet.
  • the preformed sheet is made of a ductile material chosen as a function of the energy and the dose of the radiation to be detected and the operating pressure of the detector, such as a metal (aluminum and its alloys, stainless steel, ...) or a plastic and / or composite material (epoxy glass, polycarbonate, ).
  • a ductile material chosen as a function of the energy and the dose of the radiation to be detected and the operating pressure of the detector, such as a metal (aluminum and its alloys, stainless steel, ...) or a plastic and / or composite material (epoxy glass, polycarbonate, ).
  • Operating pressure (of the detector) means the pressure under which the fluid is in the sealed enclosure, even when the detector is not operational.
  • the entrance window will preferably be made of a metal sheet, the metal having better resistance to radiation than plastics and / or composites.
  • the sheet is preformed allows it to undergo, during the pressure operation of the detector, less stress than if it were not preformed.
  • the use of a single material avoids giving rise to stresses during the temperature variations which the detector undergoes.
  • the means for fixing such a sheet may comprise a flange and elements for clamping the flange on the sealed enclosure, the sheet being clamped between the flange and the sealed enclosure.
  • These means of fixing the sheet to the sealed enclosure can also consist of a weld bead or glue.
  • a seal placed between the sealed enclosure and the sheet to seal the detector.
  • This seal is, for example, O-shaped.
  • Such a manufacturing method is simpler than mass machining and than making a multilayer window and allows, for a given material, to have a thinner window thickness than with these methods and therefore better transparency. to radiation.
  • its cost is reduced compared to the two techniques of the prior art mentioned above.
  • such a force field can be applied to the sheet hydraulically, the sheet being directly in contact with a pressurized liquid.
  • the force field can also be applied mechanically to the sheet by means of a matrix whose shape corresponds to the desired deformation of the sheet.
  • the material constituting the sheet may be advantageous to bring the material constituting it to a temperature sufficient to allow the deformation of the sheet both mechanically and hydraulically.
  • an insulating film is deposited, at least on the part of the window facing this assembly.
  • the detector manufactured according to the invention comprises a sealed enclosure 2 comprising metallic sheets 4 placed inside of it and forming a detection assembly. They delimit between them one, or as in the case of the figure, several detector cells.
  • the entry window consists of a sheet 10 such as a laminated metal sheet. This is preformed using specialized tools reproducing the systems for fixing the sheet 10 to the sealed enclosure 2. The purpose of such preforming is to establish a stress field in the deformed material, during the operation, of lesser importance compared to that which would exist in a plate, flat or of regular shape. To obtain this result, the sheet 10 must be preformed, so that its deformation is greater than or equal to that obtained by a non-preformed sheet and subjected to the operating pressure of the detector. When the detector is pressurized, the deformations of a window produced with such a sheet 10 remain in the elastic range. The positioning stability of the window relative to the internal parts is ensured.
  • the means for fixing the metal sheet 10 may comprise a flange 12 and clamping elements 14 for the flange on the sealed enclosure 2, the sheet 10 being clamped between the flange and the sealed enclosure.
  • These fixing means can be screws, the sealed enclosure 2 being provided with tapped holes.
  • the sheet fixing means can also consist of a simple weld bead or glue (not shown) thereof on the sealed enclosure.
  • a seal 8 for example an O-ring, placed on the sealed enclosure, relatively close to the cavity comprising the detection assembly 4. It seals the enclosure during operation.
  • the detection assembly can therefore consist of several conductive plates 4 delimiting detector cells.
  • the detector shown in this figure is of the multicell and ionization type.
  • drawings represent a periphery of the window and a periphery of the planar sheet, this is because the invention applies of course to such a detector, but it also applies to detectors whose window opening is curved or curved, that is to say whose shape is that of a portion of cylindrical surface. Such detectors are operational on corresponding angular openings.
  • the window can be curved, it can also have a shape different from the elongated rectangle shown in Figure 3. It can be more square in shape or be oval. In general, the initial shape of the sheet constituting the window depends on the application which is made of the detector.
  • the preformed sheet 10 intended to serve as an entry window for the detector, is shown seen from above.
  • a peripheral zone 22 of this sheet may be intended to receive a sandblasting treatment to promote the attachment of this sheet 10 to the sealed enclosure 2 of the detector.
  • the dashed line of a seal is shown in phantom 24.
  • FIG. 4 To obtain the preforming of the sheet, recourse may be had according to the invention to a first method, shown in FIG. 4.
  • the non-preformed sheet is fixed, using a specialized fixing tool and reproducing the clamping conditions of the fixing means 12 and 14 of FIG. 2.
  • a force field is applied to one of its faces, using a pressurized fluid 16. This force field must be at least equal to that of the detector's operation and may be greater or equal to 1.5 times this.
  • the sheet is then deformed by the pressure exerted by the fluid 16. This deformation depends on the material of the sheet, its proportions and the pressure exerted. It is therefore done freely under the sole effect of a uniformly distributed pressure.
  • the metal sheet is positioned in the same way, the force field being obtained mechanically, by means of a matrix 18 actuated for example by a press (not shown).
  • the shape of the matrix corresponds to the desired deformation of the sheet, this shape corresponding to the natural deformation obtained by the means described with regard to FIG. 4.
  • an aluminum sheet that must withstand a pressure of 14 bar (approximately 1,400,000 Pa) of operating pressure should have a thickness of 1 mm and a width of 40 mm.
  • a pressure of 40 bars (approximately 4,000,000 Pa) should have a thickness of 1.5 mm for a width reduced to 18 mm.
  • the sanding of the sheet is done on the plate, when the material of the latter is harder than that of the sealed enclosure of the detector. Otherwise, the sandblasting is performed on the detector enclosure.
  • the sealed enclosure can for example be made of forged aluminum.
  • the detector material has therefore undergone a heat treatment allowing the internal stresses of the material to be released.
  • the material used to make the entrance window must be a material which is easily deformable, that is to say ductile and malleable, while being transparent to the radiation to be detected.
  • the sheet can therefore be laminated aluminum, for example from the duralumin family. If the metal sheet is made of stainless steel, its thickness can be significantly less than an aluminum sheet.
  • plastic and / or composite materials can also be used. Furthermore, adequate heat treatment can improve the ductility of certain materials.
  • This manufacturing process makes it possible to lower the manufacturing cost of a window compared to the processes according to the prior art.

Description

L'invention concerne un procédé de fabrication d'un détecteur de rayonnements tel qu'un détecteur à ionisation, c'est-à-dire une chambre d'ionisation, et plus particulièrement, la fenêtre d'entrée d'un tel détecteur. Ce type de détecteur est utilisé en particulier en dosimétrie, en tomographie médicale, en radiologie et pour des contrôles non destructifs, où l'on utilise la détection de rayonnements destinés à l'imagerie tels que les rayonnements X.The invention relates to a method of manufacturing a radiation detector such as an ionization detector, that is to say an ionization chamber, and more particularly, the entry window of such a detector. This type of detector is used in particular in dosimetry, medical tomography, radiology and for non-destructive testing, where the detection of radiation intended for imaging such as X-rays is used.

Un procédé selon la première part de la revendication 1 est connu de EP-A-0 127 074.A method according to the first part of claim 1 is known from EP-A-0 127 074.

Un détecteur d'ionisation comporte une fenêtre d'entrée, au travers de laquelle pénètrent les rayons incidents, pour être détectés à l'intérieur d'une enceinte étanche du détecteur contenant un fluide ionisable sous pression. Cette fenêtre doit être d'une épaisseur aussi mince que possible pour avoir une bonne transparence aux rayonnements, compte tenu néanmoins du fait qu'il s'agit de fermer l'enceinte étanche sous pression. La fenêtre doit être également très homogène, pour assurer une bonne uniformité de la réponse du détecteur.An ionization detector has an entry window, through which the incident rays penetrate, to be detected inside a sealed enclosure of the detector containing an ionizable fluid under pressure. This window must be as thin as possible to have good transparency to radiation, nevertheless taking into account the fact that it is a question of closing the sealed enclosure under pressure. The window must also be very homogeneous, to ensure a good uniformity of the response of the detector.

En référence à la figure 1, un premier type de détecteur selon l'art antérieur comporte une enceinte étanche 2, à l'intérieur de laquelle est placé un ensemble de détection constitué de plaques conductrices 4, délimitant une, ou comme dans la figure 1, plusieurs cellules détectrices. La technique utilisée ici pour obtenir une fenêtre d'entrée est de tailler celle-ci dans la masse à partir d'un lingot 6. Le principal inconvénient de ce type de fenêtre est dû au manque d'homogénéité du matériau de base. En effet, il est risqué de tailler, par fraisage par exemple, une fenêtre de faible épaisseur par exemple inférieure à 3 mm pour l'aluminium et ses alliages, sous peine de devoir rejeter la pièce pour cause de fuite ou de fissure. Un deuxième inconvénient est, qu'après un usinage de ce type, les contraintes internes du lingot peuvent être libérées, ce qui nuit à la précision d'une fenêtre destinée à un ensemble étanche au gaz.With reference to FIG. 1, a first type of detector according to the prior art comprises a sealed enclosure 2, inside which is placed a detection assembly made up of conductive plates 4, delimiting one, or as in FIG. 1 , several detector cells. The technique used here to obtain an entry window is to cut it in the mass from an ingot 6. The main drawback of this type of window is due to the lack of homogeneity of the base material. Indeed, it is risky to cut, by milling for example, a thin window for example less than 3 mm for aluminum and its alloys, under penalty of having to reject the part due to leakage or crack. A second disadvantage is that after machining of this type, the internal constraints of the ingot can be released, which affects the precision of a window intended for a gas-tight assembly.

US-A-4 622 466 décrit un autre type de détecteur de rayonnements X, comportant une enceinte étanche sous pression. Ce détecteur utilise une fenêtre d'entrée à structure multicouche, associant une feuille de métal avec une feuille en fibre de carbone, ainsi qu'une feuille élastique d'isolement qui peut être en polyaramide. Cette technique est plus complexe que la précédente, et est plus coûteuse par la diversité des matériaux mis en jeu et leur assemblage. D'autre part, le détecteur devant être utilisé dans des conditions très variables, des différences de températures font naître des contraintes dans la structure multicouche. Ces contraintes nuisent à l'homogénéité et à l'efficacité de la fenêtre d'entrée.US-A-4 622 466 describes another type of X-ray detector, comprising a sealed enclosure under pressure. This detector uses an entrance window with a multilayer structure, associating a metal sheet with a carbon fiber sheet, as well as an elastic insulation sheet which can be made of polyaramide. This technique is more complex than the previous one, and is more expensive by the diversity of the materials involved and their assembly. On the other hand, the detector having to be used under very variable conditions, temperature differences give rise to constraints in the multilayer structure. These constraints affect the homogeneity and efficiency of the entry window.

Le but de l'invention est d'éviter les inconvénients précédemment cités, en proposant un procédé de fabrication d'un détecteur muni d'une fenêtre d'entrée simple et de coût de réalisation moins élevé.The object of the invention is to avoid the abovementioned drawbacks, by proposing a method of manufacturing a detector provided with a simple entry window and of lower production cost.

A cet effet, l'objet principal de l'invention est un procédé de fabrication d'un détecteur de rayonnements selon la revendication 1, le détecteur comprenant une enceinte étanche contenant un fluide sous pression de fonctionnement déterminée et dans laquelle est disposé un ensemble de détection, une fenêtre d'entrée de l'enceinte étanche au travers de laquelle les rayonnements pénètrent dans l'enceinte étanche, et des moyens de fixation de la fenêtre d'entrée sur l'enceinte étanche. Ce détecteur comprend une fenêtre d'entrée formée par une feuille préformée, avec une déformation supérieure ou égale à la déformation obtenue par la même feuille non préformée et soumise à la pression de fonctionnement du détecteur. De cette façon, le champ de contraintes exercé par la pression de fonctionnement du détecteur sur la feuille préformée reste dans le domaine élastique, ce qui garantit la stabilité géométrique de cette feuille.To this end, the main object of the invention is a method of manufacturing a radiation detector according to claim 1, the detector comprising a sealed enclosure containing a fluid under determined operating pressure and in which is disposed a set of detection, an entrance window of the sealed enclosure through which the radiation enters the sealed enclosure, and means for fixing the entrance window on the sealed enclosure. This detector comprises an entry window formed by a preformed sheet, with a deformation greater than or equal to the deformation obtained by the same non-preformed sheet and subjected to the operating pressure of the detector. In this way, the stress field exerted by the operating pressure of the detector on the preformed sheet remains in the elastic range, which guarantees the geometric stability of this sheet.

La feuille préformée est constituée par un matériau ductile choisi en fonction de l'énergie et de la dose des rayonnements à détecter et de la pression de fonctionnement du détecteur, tel qu'un métal (aluminium et ses alliages, acier inoxydable, ...) ou un matériau plastique et/ou composite (verre époxyde, polycarbonate,...).The preformed sheet is made of a ductile material chosen as a function of the energy and the dose of the radiation to be detected and the operating pressure of the detector, such as a metal (aluminum and its alloys, stainless steel, ...) or a plastic and / or composite material (epoxy glass, polycarbonate, ...).

On entend par "pression de fonctionnement (du détecteur)" la pression sous laquelle le fluide se trouve dans l'enceinte étanche, même quand le détecteur n'est pas opérationnel."Operating pressure (of the detector)" means the pressure under which the fluid is in the sealed enclosure, even when the detector is not operational.

Dans le cas de détecteurs prévus pour être exposés à de fortes doses d'irradiation, la fenêtre d'entrée sera de préférence constituée d'une feuille métallique, le métal ayant une meilleure tenue aux rayonnements que les matières plastiques et/ou composites. Le fait que la feuille soit préformée lui permet de subir, lors du fonctionnement sous pression du détecteur, des contraintes moindres que si elle n'était pas préformée. De plus, l'utilisation d'un seul matériau évite de faire naître des contraintes au cours des variations de températures que subit le détecteur.In the case of detectors intended to be exposed to high doses of irradiation, the entrance window will preferably be made of a metal sheet, the metal having better resistance to radiation than plastics and / or composites. The fact that the sheet is preformed allows it to undergo, during the pressure operation of the detector, less stress than if it were not preformed. In addition, the use of a single material avoids giving rise to stresses during the temperature variations which the detector undergoes.

Les moyens de fixation d'une telle feuille peuvent comprendre une bride et des éléments de serrage de la bride sur l'enceinte étanche, la feuille étant serrée entre la bride et l'enceinte étanche.The means for fixing such a sheet may comprise a flange and elements for clamping the flange on the sealed enclosure, the sheet being clamped between the flange and the sealed enclosure.

Ces moyens de fixation de la feuille sur l'enceinte étanche peuvent également être constitués d'un cordon de soudure ou de colle.These means of fixing the sheet to the sealed enclosure can also consist of a weld bead or glue.

Selon l'invention, il est préférable d'utiliser un joint d'étanchéité placé entre l'enceinte étanche et la feuille pour assurer l'étanchéité du détecteur. Ce joint est par exemple de forme torique.According to the invention, it is preferable to use a seal placed between the sealed enclosure and the sheet to seal the detector. This seal is, for example, O-shaped.

L'objet principal de l'invention est un procédé de fabrication d'un détecteur selon la revendication 1, lequel détecteur est décrit dans les paragraphes précédents, et consistant à former la fenêtre d'entrée à partir d'une feuille par les étapes suivantes :

  • fixation de la feuille non préformée, à l'aide d'un outillage de fixation spécialisé, constitué de mors de serrage serrant la feuille non préformée à sa périphérie, et reproduisant le moyen de fixation de la feuille sur l'enceinte étanche,
  • application à la feuille pour la déformer d'un champ de forces de même type que celui appliqué à la feuille par la pression de fonctionnement du détecteur et d'amplitude au moins égal à l'amplitude de celui-ci.
The main object of the invention is a method of manufacturing a detector according to claim 1, which detector is described in the preceding paragraphs, and consisting in forming the entry window from a sheet by the following steps :
  • fixing of the non-preformed sheet, using a specialized fixing tool, consisting of clamping jaws clamping the non-preformed sheet at its periphery, and reproducing the means of fixing the sheet to the sealed enclosure,
  • application to the sheet to deform it from a force field of the same type as that applied to the sheet by the operating pressure of the detector and of amplitude at least equal to the amplitude of the latter.

Un tel procédé de fabrication est plus simple qu'un usinage dans la masse et qu'une réalisation de fenêtre multicouche et permet, pour un matériau donné, d'avoir une épaisseur de fenêtre plus mince qu'avec ces procédés et donc une meilleure transparence aux rayonnements. De plus, son coût est réduit par rapport aux deux techniques de l'art antérieur citées précédemment.Such a manufacturing method is simpler than mass machining and than making a multilayer window and allows, for a given material, to have a thinner window thickness than with these methods and therefore better transparency. to radiation. In addition, its cost is reduced compared to the two techniques of the prior art mentioned above.

Selon l'invention, un tel champ de forces peut être appliqué à la feuille de façon hydraulique, la feuille étant directement en contact avec un liquide sous pression.According to the invention, such a force field can be applied to the sheet hydraulically, the sheet being directly in contact with a pressurized liquid.

Le champ de forces peut également être appliqué de façon mécanique à la feuille au moyen d'une matrice dont la forme correspond à la déformation désirée de la feuille.The force field can also be applied mechanically to the sheet by means of a matrix whose shape corresponds to the desired deformation of the sheet.

Suivant la ductilité du matériau constituant la feuille, il peut être avantageux d'amener le matériau la constituant à une température suffisante pour permettre la déformation de la feuille aussi bien de façon mécanique qu'hydraulique.Depending on the ductility of the material constituting the sheet, it may be advantageous to bring the material constituting it to a temperature sufficient to allow the deformation of the sheet both mechanically and hydraulically.

Selon une caractéristique supplémentaire de l'invention, on prévoit que le matériau le plus dur constituant la feuille ou l'enceinte soit sablé sur une zone périphérique, pour favoriser la fixation de la feuille sur l'enceinte étanche.According to an additional characteristic of the invention, provision is made for the hardest material constituting the sheet or the enclosure to be sanded on a peripheral zone, to promote the fixing of the sheet to the sealed enclosure.

Dans certaines applications, pour éviter des perturbations électriques, il est avantageux d'isoler électriquement la face interne de la fenêtre par rapport à l'ensemble de détection. Pour cela on dépose, au moins sur la partie de la fenêtre en regard de cet ensemble, un film isolant.In certain applications, in order to avoid electrical disturbances, it is advantageous to electrically isolate the internal face of the window from the detection assembly. For this, an insulating film is deposited, at least on the part of the window facing this assembly.

L'invention et ses caractéristiques seront mieux comprises à la lecture de la description qui suit, et qui est accompagnée des figures suivantes :

  • la figure 1, déjà décrite précédemment, représente un détecteur d'un type selon l'art antérieur,
  • la figure 2 représente schématiquement un détecteur fabriqué selon l'invention,
  • la figure 3 représente schématiquement une fenêtre d'entrée d'un détecteur fabriqué selon l'invention,
  • la figure 4 représente le procédé de fabrication du détecteur selon l'invention, selon une première version,
  • la figure 5 représente le procédé de fabrication d'un détecteur selon l'invention, d'après une deuxième version.
The invention and its characteristics will be better understood on reading the description which follows, and which is accompanied by the following figures:
  • FIG. 1, already described previously, represents a detector of a type according to the prior art,
  • FIG. 2 schematically represents a detector manufactured according to the invention,
  • FIG. 3 schematically represents an entry window of a detector manufactured according to the invention,
  • FIG. 4 represents the method of manufacturing the detector according to the invention, according to a first version,
  • FIG. 5 represents the method of manufacturing a detector according to the invention, according to a second version.

En référence à la figure 2, le détecteur fabriqué selon l'invention comprend une enceinte étanche 2 comprenant des feuilles métalliques 4 placées à l'intérieur de celle-ci et formant un ensemble de détection. Elles délimitent entre elles une, ou comme dans le cas de la figure, plusieurs cellules détectrices. La fenêtre d'entrée est constituée, selon l'invention, d'une feuille 10 telle qu'une feuille métallique laminée. Celle-ci est préformée à l'aide d'un outillage spécialisé reproduisant les systèmes de fixation de la feuille 10 sur l'enceinte étanche 2. Un tel préformage a pour but d'établir dans le matériau déformé un champ de contraintes, pendant le fonctionnement, de moindre importance par rapport à celui qui existerait dans une plaque, plane ou de forme régulière. Pour obtenir ce résultat, la feuille 10 doit être préformée, de façon à ce que sa déformation soit supérieure ou égale à celle obtenue par une feuille non préformée et soumise à la pression de fonctionnement du détecteur. Au moment de la mise en pression du détecteur, les déformations d'une fenêtre réalisée avec une telle feuille 10, restent dans le domaine élastique. La stabilité de positionnement de la fenêtre par rapport aux pièces internes est assurée.With reference to FIG. 2, the detector manufactured according to the invention comprises a sealed enclosure 2 comprising metallic sheets 4 placed inside of it and forming a detection assembly. They delimit between them one, or as in the case of the figure, several detector cells. According to the invention, the entry window consists of a sheet 10 such as a laminated metal sheet. This is preformed using specialized tools reproducing the systems for fixing the sheet 10 to the sealed enclosure 2. The purpose of such preforming is to establish a stress field in the deformed material, during the operation, of lesser importance compared to that which would exist in a plate, flat or of regular shape. To obtain this result, the sheet 10 must be preformed, so that its deformation is greater than or equal to that obtained by a non-preformed sheet and subjected to the operating pressure of the detector. When the detector is pressurized, the deformations of a window produced with such a sheet 10 remain in the elastic range. The positioning stability of the window relative to the internal parts is ensured.

Les moyens de fixation de la feuille métallique 10 peuvent comprendre une bride 12 et des éléments de serrage 14 de la bride sur l'enceinte étanche 2, la feuille 10 étant serrée entre la bride et l'enceinte étanche. Ces moyens de fixation peuvent être des vis, l'enceinte étanche 2 étant munie de trous taraudés.The means for fixing the metal sheet 10 may comprise a flange 12 and clamping elements 14 for the flange on the sealed enclosure 2, the sheet 10 being clamped between the flange and the sealed enclosure. These fixing means can be screws, the sealed enclosure 2 being provided with tapped holes.

Les moyens de fixation de la feuille peuvent également être constitués d'un simple cordon de soudure ou de colle (non représenté) de celle-ci sur l'enceinte étanche. On prévoit également l'utilisation d'un joint 8, par exemple torique, placé sur l'enceinte étanche, relativement près de la cavité comportant l'ensemble de détection 4. Il assure l'étanchéité de l'enceinte pendant le fonctionnement.The sheet fixing means can also consist of a simple weld bead or glue (not shown) thereof on the sealed enclosure. There is also provision for the use of a seal 8, for example an O-ring, placed on the sealed enclosure, relatively close to the cavity comprising the detection assembly 4. It seals the enclosure during operation.

L'ensemble de détection peut donc être constitué de plusieurs plaques conductrices 4 délimitant des cellules détectrices. Le détecteur représenté sur cette figure est de type multicellulaire et à ionisation.The detection assembly can therefore consist of several conductive plates 4 delimiting detector cells. The detector shown in this figure is of the multicell and ionization type.

Si les dessins représentent une périphérie de la fenêtre et une périphérie de la feuille planes, c'est que l'invention s'applique bien sûr à un tel détecteur, mais elle s'applique également à des détecteurs dont l'ouverture des fenêtres est bombée ou incurvée, c'est-à-dire dont la forme est celle d'une portion de surface cylindrique. De tels détecteurs sont opérationnels sur des ouvertures angulaires correspondantes.If the drawings represent a periphery of the window and a periphery of the planar sheet, this is because the invention applies of course to such a detector, but it also applies to detectors whose window opening is curved or curved, that is to say whose shape is that of a portion of cylindrical surface. Such detectors are operational on corresponding angular openings.

Mis à part, le fait que la fenêtre peut être bombée, elle peut également avoir une forme différente du rectangle allongé représenté sur la figure 3. Elle peut être de forme plus carrée ou être ovale. De manière générale, la forme initiale de la feuille constituant la fenêtre dépend de l'application qui est faite du détecteur.Aside from the fact that the window can be curved, it can also have a shape different from the elongated rectangle shown in Figure 3. It can be more square in shape or be oval. In general, the initial shape of the sheet constituting the window depends on the application which is made of the detector.

Sur la figure 3, la feuille 10 préformée, destinée à servir de fenêtre d'entrée au détecteur, est représentée vue de dessus. Une zone périphérique 22, de cette feuille, peut être destinée à recevoir un traitement de sablage pour favoriser l'accrochage de cette feuille 10 sur l'enceinte étanche 2 du détecteur. Entre cette zone périphérique 22 et la zone préformée 26 se situant au centre, on a représenté en traits mixtes 24 la ligne d'appui d'un joint d'étanchéité.In FIG. 3, the preformed sheet 10, intended to serve as an entry window for the detector, is shown seen from above. A peripheral zone 22 of this sheet may be intended to receive a sandblasting treatment to promote the attachment of this sheet 10 to the sealed enclosure 2 of the detector. Between this peripheral zone 22 and the preformed zone 26 lying in the center, the dashed line of a seal is shown in phantom 24.

Pour obtenir le préformage de la feuille, on peut avoir recours selon l'invention, à un premier procédé, représenté sur la figure 4. La feuille non préformée est fixée, à l'aide d'un outillage de fixation spécialisé et reproduisant les conditions de serrage des moyens de fixation 12 et 14 de la figure 2. On peut utiliser comme moyen de fixation, des mors de serrage 20, serrant la feuille à sa périphérie. Une fois la feuille fermement fixée, on applique sur une de ses faces un champ de forces, à l'aide d'un fluide sous pression 16. Ce champ de forces doit être au moins égal à celui de fonctionnement du détecteur et peut être supérieur ou égal à 1,5 fois celui-ci. La feuille est alors déformée par la pression exercée par le fluide 16. Cette déformation est fonction du matériau de la feuille, de ses proportions et de la pression exercée. Elle se fait donc de manière libre sous le seul effet d'une pression uniformément répartie.To obtain the preforming of the sheet, recourse may be had according to the invention to a first method, shown in FIG. 4. The non-preformed sheet is fixed, using a specialized fixing tool and reproducing the clamping conditions of the fixing means 12 and 14 of FIG. 2. One can use as fixing means, clamping jaws 20, clamping the sheet at its periphery. Once the sheet is firmly fixed, a force field is applied to one of its faces, using a pressurized fluid 16. This force field must be at least equal to that of the detector's operation and may be greater or equal to 1.5 times this. The sheet is then deformed by the pressure exerted by the fluid 16. This deformation depends on the material of the sheet, its proportions and the pressure exerted. It is therefore done freely under the sole effect of a uniformly distributed pressure.

En référence à la figure 5, la feuille métallique est positionnée de la même manière, le champ de forces étant obtenu de manière mécanique, au moyen d'une matrice 18 actionnée par exemple par une presse (non représentée). La forme de la matrice correspond à la déformation désirée de la feuille, cette forme correspondant à la déformation naturelle obtenue par les moyens décrits en regard de la figure 4.With reference to FIG. 5, the metal sheet is positioned in the same way, the force field being obtained mechanically, by means of a matrix 18 actuated for example by a press (not shown). The shape of the matrix corresponds to the desired deformation of the sheet, this shape corresponding to the natural deformation obtained by the means described with regard to FIG. 4.

Le choix des dimensions et la nature du matériau utilisés sont dictés par les spécifications techniques du détecteur à fabriquer, et en particulier la pression de service, la transparence minimale aux rayonnements et la dose de rayonnements. L'épaisseur est adaptée à ces conditions, ainsi que le matériau choisi, pour rester dans les limites de sécurité habituelles. Par exemple, une feuille en aluminium devant supporter une pression de 14 bars (environ 1 400 000 Pa) de pression de fonctionnement, devrait avoir une épaisseur d'1 mm et une largeur de 40 mm. Pour une pression de 40 bars (environ 4 000 000 Pa), une tôle en aluminium devrait avoir une épaisseur d'1,5 mm pour une largeur réduite à 18 mm.The choice of dimensions and the nature of the material used are dictated by the technical specifications of the detector to be manufactured, and in particular the operating pressure, the minimum transparency to radiation and the dose of radiation. The thickness is adapted to these conditions, as well as the material chosen, to stay within the usual safety limits. For example, an aluminum sheet that must withstand a pressure of 14 bar (approximately 1,400,000 Pa) of operating pressure, should have a thickness of 1 mm and a width of 40 mm. For a pressure of 40 bars (approximately 4,000,000 Pa), an aluminum sheet should have a thickness of 1.5 mm for a width reduced to 18 mm.

Le sablage de la feuille se fait sur la plaque, lorsque le matériau de celle-ci est plus dur que celui de l'enceinte étanche du détecteur. Dans le cas contraire, le sablage est effectué sur l'enceinte du détecteur.The sanding of the sheet is done on the plate, when the material of the latter is harder than that of the sealed enclosure of the detector. Otherwise, the sandblasting is performed on the detector enclosure.

L'enceinte étanche peut être par exemple en aluminium forgé. Le matériau du détecteur a donc subi un traitement thermique permettant de libérer les contraintes internes du matériau.The sealed enclosure can for example be made of forged aluminum. The detector material has therefore undergone a heat treatment allowing the internal stresses of the material to be released.

Comme on l'a vu précédemment, le matériau utilisé pour réaliser la fenêtre d'entrée doit être un matériau se déformant facilement, c'est-à-dire ductile et malléable, tout en étant transparent aux rayonnements à détecter. La feuille peut donc être de l'aluminium laminé, par exemple de la famille des duralumins. Si la feuille métallique est en acier inoxydable, son épaisseur peut être notablement inférieure à une feuille en aluminium.As we have seen above, the material used to make the entrance window must be a material which is easily deformable, that is to say ductile and malleable, while being transparent to the radiation to be detected. The sheet can therefore be laminated aluminum, for example from the duralumin family. If the metal sheet is made of stainless steel, its thickness can be significantly less than an aluminum sheet.

Bien entendu, comme on l'a vu précédemment, on peut utiliser également des matériaux plastiques et/ou composites. Par ailleurs, un traitement thermique adéquate peut permettre d'améliorer la ductilité de certains matériaux.Of course, as we have seen previously, plastic and / or composite materials can also be used. Furthermore, adequate heat treatment can improve the ductility of certain materials.

La diminution de l'épaisseur de la feuille permet une amélioration très sensible de la transparence de la fenêtre d'entrée aux rayonnements. Les problèmes dus aux variations de températures sont supprimés, du fait qu'un seul matériau constitue cette fenêtre d'entrée.The reduction in the thickness of the sheet allows a very significant improvement in the transparency of the entry window to radiation. The problems due to temperature variations are eliminated, since only one material constitutes this entry window.

Ce procédé de fabrication permet de descendre le coût de fabrication d'une fenêtre par rapport aux procédés selon l'art antérieur.This manufacturing process makes it possible to lower the manufacturing cost of a window compared to the processes according to the prior art.

Claims (5)

  1. Process for manufacturing a radiation detector comprising:
    - a leaktight enclosure (2) containing a fluid under a specified operating pressure and in which a detection assembly is arranged;
    - an entrance window of the leaktight enclosure (2) formed by a preformed sheet (10) and through which the rays to be detected penetrate into the leaktight enclosure (2); and
    - means for fixing the entrance window to the leaktight enclosure (2),
    characterised in that it consists in forming the entrance window from a sheet by the following steps:
    - fixing the non-preformed sheet with the aid of a specialised fixing tool (20), which consists of clamping jaws clamping the sheet on its periphery, and reproducing the clamping conditions of the means (12, 14) for fixing the sheet (10) to the leaktight enclosure (2); and
    - applying to the sheet, in order to deform it, a uniform force field of the same type as that applied to the sheet (10) by the operating pressure of the detector and of amplitude greater than or equal to that of the latter field.
  2. Process according to Claim 1, characterised in that the preformed sheet (10) is constituted by a ductile material chosen as a function of the energy and of the dose of the radiation to be detected and of the operating pressure of the detector.
  3. Process according to Claim 1 or 2, characterised in that the force field is applied to the sheet (10) in a hydraulic manner, the sheet (10) being in direct contact with a pressurised liquid (16).
  4. Process according to Claim 1 or 2, characterised in that the force field is applied to the sheet (10) in a mechanical manner by means of a die (18), the shape of which corresponds to the desired deformation of the sheet (10).
  5. Process according to any one of Claims 1 to 4, characterised in that the hardest material constituting the sheet (10) or the enclosure (2) is sandblasted on a peripheral zone (22), so as to facilitate the attachment of the sheet (10) to the leaktight enclosure (2).
EP88402958A 1987-11-27 1988-11-24 Manufacturing process of a radiation detector Expired - Lifetime EP0319378B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8716494 1987-11-27
FR8716494A FR2623940A1 (en) 1987-11-27 1987-11-27 RADIATION DETECTOR AND METHOD FOR MANUFACTURING ITS INPUT WINDOW

Publications (2)

Publication Number Publication Date
EP0319378A1 EP0319378A1 (en) 1989-06-07
EP0319378B1 true EP0319378B1 (en) 1993-04-07

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Application Number Title Priority Date Filing Date
EP88402958A Expired - Lifetime EP0319378B1 (en) 1987-11-27 1988-11-24 Manufacturing process of a radiation detector

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EP (1) EP0319378B1 (en)
DE (1) DE3880099T2 (en)
FR (1) FR2623940A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0147734A2 (en) * 1983-12-19 1985-07-10 Kabushiki Kaisha Toshiba A vacuum tube and a method for manufacturing the same
EP0240718A1 (en) * 1986-03-14 1987-10-14 General Electric Company High efficiency detector for energetic X-rays

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59216075A (en) * 1983-05-23 1984-12-06 Toshiba Corp Radiation detector

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0147734A2 (en) * 1983-12-19 1985-07-10 Kabushiki Kaisha Toshiba A vacuum tube and a method for manufacturing the same
EP0240718A1 (en) * 1986-03-14 1987-10-14 General Electric Company High efficiency detector for energetic X-rays

Also Published As

Publication number Publication date
DE3880099D1 (en) 1993-05-13
EP0319378A1 (en) 1989-06-07
FR2623940A1 (en) 1989-06-02
DE3880099T2 (en) 1993-10-07

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