EP0064913A2 - X-rays multidetector - Google Patents

X-rays multidetector Download PDF

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Publication number
EP0064913A2
EP0064913A2 EP82400769A EP82400769A EP0064913A2 EP 0064913 A2 EP0064913 A2 EP 0064913A2 EP 82400769 A EP82400769 A EP 82400769A EP 82400769 A EP82400769 A EP 82400769A EP 0064913 A2 EP0064913 A2 EP 0064913A2
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EP
European Patent Office
Prior art keywords
electrodes
multidetector
enclosure
plate
main
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EP82400769A
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German (de)
French (fr)
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EP0064913B1 (en
EP0064913A3 (en
Inventor
Robert Allemand
Jean-Jacques Gagelin
Edmond Tournier
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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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Publication of EP0064913A3 publication Critical patent/EP0064913A3/en
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Publication of EP0064913B1 publication Critical patent/EP0064913B1/en
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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
    • H01J47/02—Ionisation chambers

Definitions

  • the present invention relates to a method of manufacturing an X-ray multidetector, and in particular of X-rays which have passed through an object or an organ after having been emitted by a source emitting towards the object or the organ, these X-rays in the form of a planar beam having a wide angular opening and a small thickness.
  • This invention applies more particularly to the manufacture of multidetectors intended for tomography or radiography of organs, but also to industrial control, such as baggage control for example.
  • the X-ray multidetectors make it possible to measure the absorption of an X-ray beam passing through an object or an organ, this absorption being linked to the density of the tissues of the organ examined or to the density of the materials constituting the object studied.
  • a first type of ionization X-ray multidetector used in radiography and tomography is multicellular and comprises cells delimited by conductive plates perpendicular to the plane of the X-ray beam and brought alternately to positive and negative potentials. These cells are located in a sealed enclosure containing an ionizing gas.
  • the advantages of this type of multidetector are as follows: it provides good collimation of X-rays when the plates used in the detection cells are made of a very absorbent material; the collection time of the charges resulting from the ionization of the gas by X-rays is very short because of the small spacing of the conductive plates and the good separation between the detection cells.
  • this type of multidetector has significant drawbacks: it is very difficult to manufacture and therefore expensive. In addition, if it is desired to reduce the thickness of the plates in order to increase the quantity of X-rays detected, there is a reduction in collimation due to the small thickness of the plates; this small thickness of the plates also causes a very large microphone. Finally, multidetectors of this type, as indicated above, have a great complexity of production which involves a high manufacturing cost; they require mounting in a dust-free room, because any dust on one of the plates, can cause priming or deterioration of the leakage current between two consecutive plates. It is added to these drawbacks that the numerous electrodes used require very numerous electrical connections, inside the sealed chamber, which poses problems. my difficult reliability of soldering connections on the electrodes.
  • a second type of multidetector which has a much simpler structure, but which is not perfect.
  • This other type of multidetector comprises a sealed chamber containing a gas ionizable by rays from the organ or object and, in this chamber, a plate for collecting the electrons resulting from the ionization of the gas; this plate is parallel to the plane of the beam of incident rays and it is brought to a positive high voltage.
  • a series of electrodes for collecting the ions resulting from the ionization of the gas by the X-rays coming from the object is arranged in parallel and facing the preceding plate; these ion collection electrodes are brought to a potential close to 0 and are directed towards the source which emits the X-rays, in the direction of the object. They are located in a plane parallel to the plane of the beam of the incident rays and respectively provide a function measurement current. of the quantity of ions obtained by the ionization of the gas opposite each electrode, under the effect of the rays coming from the object or the organ, in a direction corresponding to that of the incident rays.
  • This type of multidetector has certain advantages: there are no longer, as in the previously mentioned multidetector, separation plates; this eliminates any annoying phenomenon of microphony. Due to the removal of these separation plates, the quantity of X-rays detected is maximum; the realization of this type of multidetector is simpler and it is very little sensitive to dust. Finally, it is possible, without connection inside the sealed chamber, to re pick up, inside the chamber, the signals available on each of the electrodes brought to a potential close to 0.
  • this type of multidetector still presents a serious manufacturing difficulty because the electrodes are connected to measurement points outside the enclosure, by connections which require soldering on these electrodes, inside the enclosure. These welds are very difficult to perform and the passage of these connections through the enclosure poses problems of sealing and electrical insulation, very difficult and very costly to solve.
  • the object of the present invention is to remedy this drawback and in particular to manufacture a multidetector of this second type, in a simple and inexpensive manner, without welding on the electrodes inside the enclosure to connect them, by connections, at points outside the enclosure.
  • the invention relates to uri method of manufacturing an X-ray multidetector adapted to commission- including X rays having passed through an object or organ, these radii being provided by a source emitting a beam of plane Q of low X-ray thickness, this multidetector comprising a sealed enclosure filled with an ionizable gas, and in this enclosure, at least one main multidetector assembly comprising a flat conductive plate, electrically isolated from the enclosure, parallel to the X-ray beam and brought to a first potential level, and a plurality of planar electrodes parallel to the plate, electrically isolated from this plate, these electrodes being isolated from each other, brought to a second potential level and extending in the direction of the rays supplied by the source, method characterized in that it consists in producing the electrodes as well as main connections between these electrodes and measurement points outside the enclosure making it possible to take the currents flowing respectively in these electrodes, on a main face of an electrically insulating plate, these main connections being electrically isolated from
  • At least one other secondary multidetector assembly is produced, with a structure identical to that of the main multidetector assembly, the plate of this secondary multidetector being brought to a third potential level and the electrodes being brought to a second potential level, the electrodes of this secondary multidetector as well as respective connections between these electrodes and secondary points external to the enclosure being made on a secondary face of the electrically insulating plate, opposite to the main face, these secondary connections being electrically isolated from the enclosure and passing through it in a sealed manner opposite to the X-ray source, the process then consisting in connecting the main and secondary connections respectively.
  • the electrodes and the connections are made in the form of conductive deposits on the insulating plate.
  • these conductive deposits are etched metallized deposits.
  • the invention also relates to a method for manufacturing multiple X-ray detectors providing a flat beam, characterized in that the sealed enclosure is constituted by at least one electrically insulating plate carrying the electrodes and the connections between these electrodes and the external measurement points, at least one conductive plate, and at least one spacer electrically insulated, the hollow interior of which forms said enclosure and separating the two plates, insulating and conducting.
  • This manufacturing process obviously still makes it possible to produce a structure with a main multidetector and a secondary multidetector, the two enclosures defined by two plates and a spacer being superimposed and filled with an ionizable gas; it also makes it possible to produce a superimposition of multidetectors, either with a simple structure or with a double structure (main multidetector and secondary multidetector), making it possible to analyze several parallel planar beams juxtaposed simultaneously.
  • the subject of the invention is an X-ray multidetector obtained according to the method described above.
  • FIG. 1 shows schematically and in perspective, a multidetector that it is possible to manufacture according to the method of the invention.
  • This. multidetector comprises a plate 1 brought to a first potential level (high positive voltage + HV) and, opposite, a series of electrodes 2 brought to a second potential level (close to 0 volts).
  • This plate and these electrodes are located in a sealed main chamber 3, shown diagrammatically and which contains at least one ionizable gas, such as xenon for example.
  • This multidetector makes it possible to detect the X-rays which have passed through an object or an organ 0, these rays being supplied by a point or linear source S which emits in the direction of the object or the organ, a plane beam F of X-rays incidents.
  • This beam has a wide angular opening and a small thickness.
  • the plate 1 is parallel to the plane of the beam of incident rays, while the plane electrodes 2 are located in a plane parallel to the plane of the beam of incident rays, opposite the plate 1.
  • the plate 1 which is brought to a positive potential neighbor of a few kilovolts, is an electron collection plate, while the electrodes 2 are ion collection electrodes. These electrodes are generally carried by an insulating plate (not shown in this figure) and are electrically isolated from each other.
  • the pressure of the xenon inside the sealed chamber has a value which is a function of the energy of the X-ray to be detected (from 1 to 40 bars approximately); this gas can also be added to other gases intended to improve detection.
  • the electrodes 2 form converging bands in the direction of the source S.
  • FIG. 2 schematically represents a front view of the preceding multidetector.
  • This figure shows the plate 1 brought to a positive potential + HT as well as the electrodes 2 brought to a potential close to 0 volts; these electrodes are supported by an electrically insulating plate 4 and each of them is connected to an amplifier 5 which makes it possible to draw the current flowing in each of the electrodes; these currents are applied to a processing (not shown) and visualization system, which makes it possible to visualize the body or object 0 traversed by the X-rays emitted by the source S.
  • dotted lines vertical, field lines.
  • Xe + represents the positive xenon ions which go towards the electrodes 2 and by e - the electrons which go towards the plate 1; these ions and these electrons resulting from the ionization of xenon by X-rays from the object or organ 0.
  • the electrons are replaced by the negative ions, formed from additional gas.
  • the method of manufacturing this multidetector consists in carrying out the electrodes 2 as well as main connections between these electrodes and points outside the enclosure, making it possible to take the currents flowing respectively in these electrodes, on a main face of an electrically insulating plate 4. These connections are shown more fully in Figures 5 and 6. These main connections are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source.
  • FIG. 3 shows schematically and in perspective, another multidetector obtained according to the method of the invention.
  • This multidetector comprises a sealed metal chamber 6 for example containing at least one ionizable gas such as xenon for example this chamber is subdivided into two ionization chambers: a main ionization chamber 3 and a secondary ionization chamber 7.
  • the main ionization chamber 3 contains, like the multidetector of FIG. 1, a plate 1 brought to a first potential level (high positive voltage + HT) and a series of electrodes 2 brought to a second potential level (close to 0 volts).
  • the plate 1 and the electrodes 2 in the main ionization chamber 3 form a main multidetector assembly.
  • these electrodes are planar and are carried by an electrically insulating plate 4; the plate 1 and the electrodes 2 are located in a plane parallel to the plane of the X-ray beam from the object 0 (this beam being incompletely shown in the figure).
  • the electrodes 2 converge in the direction of the source S.
  • Each of the electrodes 2 of the main ionization chamber 3 is connected to an amplifier 5 which makes it possible to take samples. for treatment, the current flowing in each of these electrodes.
  • the secondary ionization chamber 7 is attached to the main chamber to compensate for the diffusion current coming from the X-rays scattered by the member 0.
  • the electrodes 2 of the main ionization 3 respectively provide a current I which is the sum of a part, of a measurement current I M proportional to the quantity of ions obtained by the ionization of the gas opposite each electrode of the chamber main ionization under the effect of the rays from the object, in directions corresponding to that of the incident rays 9, and of a diffusion current i D resulting from the ionization of the gas by the rays 8 diffused, in particular by l object, in directions other than that of the incident rays.
  • the secondary ionization chamber 7 contains, like the main ionization chamber, a plate 10 parallel to the plane of the incident X-ray beam, is brought to a third potential level (negative high voltage -HT), as well as a series of planar electrodes 11, parallel to the plane of the incident X-ray beam, and situated on another face of the insulating plate 4 which carries the electrodes 2 of the main ionization chamber 3.
  • the plate 10 and the electrodes 11 in the secondary chamber 7 form a secondary multidetector assembly.
  • the electrodes 11 are brought, like the electrodes 2 of the main ionization chamber, to a potential close to 0. They are respectively connected by connections 12, to the corresponding electrodes of the main ionization chamber 3.
  • the electrodes 11 of the secondary ionization chamber and the electrodes 2 of the main ionization chamber are, preferably identical and located opposite one another.
  • the secondary ionization chamber 7 makes it possible, as will be seen below in detail, to compensate, for the subsequent treatment of the currents originating from the amplifiers 5, the diffused currents which circulate in each electrode of the main ionization chamber and which originate X-rays scattered by the object or organ 0.
  • the electrodes 11 of the secondary ionization chamber 7 are electrodes for collecting electrons e - or negative ions, while the plate 10 is a plate for collecting the Xe + ions from the ionization of the xenon contained in the secondary chamber 7, by the X-rays scattered by the object or the organ 0.
  • the electrodes of the secondary ionization chamber are located opposite the electrodes of the main ionization chamber and the high positive and negative voltages have the same absolute value.
  • Reference 50 designates a diaphragm.
  • Figure 4 schematically shows a side view of the previous multidetector.
  • the source S the object or the organ 0
  • one of the rays 9 emitted by the source S and, at the output of the object 0, the direct ray 13 coming from the object 0 , in the same direction as the incident ray 9; we also distinguish in this figure 1! one of the scattered rays 8, coming from the object 0, in a direction different from the direction of the incident ray 9.
  • one of the electrodes 2 of the chamber d is shown.
  • main ionization which is connected to an amplifier 5 and which is brought to a potential close to 0, and one of the electrodes 11 of the secondary ionization chamber 7, which is located opposite the electrode 2 and which is separated from this electrode by the insulating plate 4.
  • connection 12 between the electrodes of the main and secondary ionization chambers has also been shown.
  • plates 1 and 10 of the main and secondary ionization chambers brought respectively to positive and negative potentials + HT and -HT.
  • the sealed chamber 6 which contains the ionizable gas has not been shown in detail; the insulating plates 42, 14 support the conductive plates 1, 10 of the main and secondary ionization chambers.
  • This ionization is represented diagrammatically in the figure by Xe + ions which are attracted by the electrodes 2, and by electrons e - or negative ions which are attracted by the positive plate 1.
  • An ionization thus occurs opposite each of the electrodes from the main ionization chamber using X-rays from the object, in the direction of the incident rays.
  • a current I which is the sum of a current I m resulting from the ionization of the gas opposite each of the electrodes, under the effect of X-rays from the object. (rays represented at 13 in the figure), in a direction corresponding to that of the incident rays, and of a diffusion current I D , which results from the ionization of the gas, opposite each of the electrodes, from the rays scattered by the object, in directions which do not correspond to those of the incident X-rays.
  • the method of manufacturing this multidetector consists, as for the multidetector of FIG. 3, in producing on a main face 16 of the electrically insulating plate 4, the electrodes 2 as well as the main connections 15 between these electrodes and the measurement points 19 outside the enclosure; these measurement points make it possible to take the currents flowing respectively in these electrodes; the main connections 15 are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source.
  • the method then consists in making at least the other secondary multidetector assembly, with a structure identical to that of the main multidetector assembly; the plate 10 of this secondary multidetector is brought, as indicated above, to a negative high voltage and the electrodes 11 are brought to a neighboring potential from 0.
  • the electrodes 11 of this secondary multidetector, as well as respective connections 17 between these electrodes 11 and secondary points 20, external to the enclosure, are produced on a secondary face 18 of the electrically insulating plate 4; this secondary face 18 is opposite to the main face 4; the secondary connections 17 are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source S; the method then consists in connecting the measurement point 19 and the secondary points 20 respectively.
  • the electrodes and connections are made in the form of conductive deposits on the insulating plate; preferably, these conductive deposits are metallized deposits etched on the insulating plate.
  • the conductive plates 1 and 7 are brought respectively to a positive voltage + HT and to a negative high voltage -HT, by making a connection between each of these plates and a high voltage source external to the enclosure; this connection is electrically isolated from the enclosure and crosses it in a sealed manner.
  • Figure 5 is a schematic side sectional view of a multicut multidetector, the operation of which is comparable to that of the multidetector of Figure 3; this multidetector is manufactured according to the method of the invention, by stacking a plurality of main and secondary multidetector assemblies as described in FIG. 3.
  • the multidetector of FIG. 5 is a stack of main and secondary multidetectors, as described in FIG. 3.
  • This stack Lement comprises a first main multidetector assembly comprising a flat conductive plate 1 intended to be brought to a positive high voltage + HT, electrically isolated from the enclosure, (the latter may be constituted for example by epoxy resin).
  • This flat conductive plate is parallel to the beam F 'of X-rays coming from the object or the organ to be analyzed (not shown in this figure).
  • This first multidetector assembly also includes a plurality of planar electrodes 2 parallel to the plate 1 and extending in the direction of the X-rays of the beam F '.
  • Electrodes are isolated from each other as will be seen below in detail, and are brought to a potential close to 0.
  • These electrodes as well as main connections 15 between these electrodes and measurement points 19 outside the enclosure making it possible to take the currents flowing respectively in these electrodes are produced on one face 16 of the electrically insulating plate 4.
  • These main connections 15 are electrically isolated from the enclosure and pass through the latter in leaktight manner, opposite the source which emits the beam F ′ of X-rays.
  • the enclosure containing an ionizable gas is here constituted by l insulating spacer 21, of epoxy resin for example, the hollow interior of which forms a chamber; this spacer makes it possible to separate the electrodes 2 and the plate 1 and the chamber can contain xenon for example.
  • the covers 33 and 34 are provided in aluminum alloy, but the plates 10 and 31 are identical to the plates 1, 15 and 10, 14 of FIG. 4.
  • the covers 33, 34 could possibly rest in a sealed manner on the plate 1 and on the insulating plate 4, to form with the electrodes 2, an elementary multidetector the front face of which would be provided with a sealed window 38.
  • At least one other secondary multidetector assembly is produced, with a structure identical to that of the main multidetector assembly which has just been described.
  • the plate 10 of this secondary multidetector is brought to a negative high voltage -HT, while the electrodes 11 of this multidetector, whose structure is identical to that of the electrodes 2 of the main multidetector, are brought to a potential close to 0.
  • the electrodes 11 as well as the respective connections 17 between these electrodes and secondary points external to the enclosure formed by the spacers 21, 22, are formed on the other face 18 of the electrically insulating plate 4.
  • the secondary connections 17 are electrically insulated of the enclosure, the latter consisting of epoxy resin for example; these connections pass through the enclosure formed by the spacers 21, 22 in a sealed manner, opposite to the source emitting the beam F ′ of X-rays.
  • the method then consists in connecting the main 15 and secondary 17 connections to the measurement points 19, for each of the electrodes, by a connector 40, shown schematically in the figure. If the hollow spacers 21, 22 are closed by covers 33, 34 pressing in leaktight manner on the plates 1 and 10, a multidetector with a structure comparable to that of FIG. 3 is obtained; this multidetector making it possible to compensate, thanks to the secondary assembly, as mentioned above, the diffusion current present in the current taken from each of the electrodes.
  • This other stack includes a main multidetector pal formed by the plate 1 brought to the high positive voltage and electrodes 23 of ion collections, brought to a potential close to 0, connected to measurement points 24, by main connections 25; the electrodes 23 and the main connections 25 are made, as before, on a face 26 of an electrically insulating plate 27.
  • the electrodes 23 and the plate 1 are separated by a hollow insulating spacer 28.
  • a secondary multidetector is formed on the other side of the insulating plate 27. This secondary multidetector comprises electrodes 29 brought to a potential close to 0.
  • This secondary multidetector assembly also includes a plate 31 brought to a negative high voltage -HT and separated from the electrodes 29 by an insulating spacer 32; the various spacers, electrodes and plates of this stack are made integral by covers 33, 34 and provided with fixing means 35; the covers, the spacers, the plates and connections, as well as the plates supporting your electrodes, are made integral so that the assembly forms a hollow hollow volume 36, containing xenon for example.
  • the different chambers formed in this hollow volume can be brought into communication by openings such as 37 made in the plates supporting the electrodes and in the plate 1 brought to high positive voltage + HT.
  • the electrodes 29 and the plate 31 of the secondary chamber of the second stack form a compensation chamber for the currents of diffusion which disturb the currents measured on the electrodes 23 of the main chamber of this second stack.
  • the connector 41 makes it possible to connect respectively to the measurement points 24 of the electrodes 23 and 29 of this second stack.
  • a watertight window 38 maintained by a flange 39, is arranged on the front face of the multidetector.
  • the detector shown in this figure comprises two stacks which make it possible to make two parallel sections of an organ or an object to be analyzed; this multidetector could comprise a single stack or more than two stacks. It is also obvious that each multidetector may not include the diffusion current compensation chamber; the invention relates in fact to the production of the electrodes and their connections with external points, these electrodes and these connections being produced in the form of conductive deposits on an insulating plate. These deposits are metallized and engraved on the insulating plate.
  • the invention also relates, and above all, to the manufacture of a multidetector by stacking such insulating plates equipped with conductive deposits and insulating spacers, this stack producing the insulating enclosure filled with detector gas.
  • Figure 6 is a top view of the detector of Figure 5, according to a section taken at the plate 4 for example.
  • the electrodes 2 directed in the direction of the rays of the beam F 'of X-rays and the main connections 15 between these electrodes and measurement points 19 outside the multidetector. It is also better to distinguish that the electrodes 2 and the connections 15 are made in the form of conductive deposits on the insulating plate 4. It is obvious that the electrodes 11, 23 and 29 are made in the same way.
  • the plates and electrodes of the main and secondary ionization chambers of each stack are preferably produced in the form of a copper deposit on an insulating support.
  • the number of cells in each chamber can be greater than 500, for an opening angle of the X-ray beam greater than 40 °; in this case, the pitch between each of the electrodes of each chamber is approximately 1 mm.
  • the insulating plate which supports the electrodes of the main and secondary chambers is located midway between the plates which are respectively brought to positive and negative potential. The distance between these plates is approximately 14 mm and the ion collection time is close to 10 ms.

Abstract

L'invention concerne un procédé de fabrication d'un multidétecteur de rayons X formant un faisceau plan (F). Ce multidétecteur comprend une enceinte étanche remplie d'un gaz ionisable et, dans cette enceinte, au moins un ensemble multidétecteur principal comportant une plaque plane conductrice (1), électriquement isolée de l'enceinte et une pluralite d'électrodes planes (2) parallèles à la plaque (1), isolées de cette plaque. Ce procédé est caractérisé en ce qu'il consiste à réaliser les électrodes (2) ainsi que des connexions principales (15) entre ces électrodes et des points de mesure (19) extérieurs à l'enceinte permettant de prélever les courants circulant respectivement dans ces électrodes, sur une face principale (16) d'une plaque électriquement isolante (4), ces connexions principales etant electriquement isolées de l'enceinte et traversant celle-ci de manière étanche, à l'opposé de la source qui émet les rayons X. Application à la fabrication de multidétecteurs de rayons X destinés à la tomographie ou à la radiographie d'organes, ou au contrôle de bagages.The invention relates to a method for manufacturing an X-ray multidetector forming a planar beam (F). This multidetector comprises a sealed enclosure filled with an ionizable gas and, in this enclosure, at least one main multidetector assembly comprising a flat conductive plate (1), electrically isolated from the enclosure and a plurality of parallel planar electrodes (2) to the plate (1), isolated from this plate. This process is characterized in that it consists in producing the electrodes (2) as well as the main connections (15) between these electrodes and measurement points (19) outside the enclosure making it possible to take the currents flowing respectively in these electrodes, on a main face (16) of an electrically insulating plate (4), these main connections being electrically isolated from the enclosure and passing through it in leaktight manner, opposite to the source which emits X-rays Application to the manufacture of X-ray multidetectors intended for tomography or radiography of organs, or for checking baggage.

Description

La présente invention concerne un procédé de fabrication d'un multidétecteur de rayons X, et notamment de rayons X qui ont traversé un objet ou un organe après avoir été émis par une source émettant en direction de l'objet ou de l'organe, ces rayons X se présentant sous la forme d'un faisceau plan présentant une large ouverture angulaire et une faible épaisseur. Cette invention s'applique plus particulièrement à la fabrication de multidétecteurs destinés à la tomographie ou radiographie d'organes, mais également au contrôle industriel, tel que le contrôle de bagages par exemple.The present invention relates to a method of manufacturing an X-ray multidetector, and in particular of X-rays which have passed through an object or an organ after having been emitted by a source emitting towards the object or the organ, these X-rays in the form of a planar beam having a wide angular opening and a small thickness. This invention applies more particularly to the manufacture of multidetectors intended for tomography or radiography of organs, but also to industrial control, such as baggage control for example.

On sait que dans ces applications les multidétecteurs de rayons X permettent de mesurer l'absorption d'un faisceau de rayons X traversant un objet ou un organe, cette absorption étant liée à la densité des tissus de l'organe examiné ou à la densité des matériaux constituant l'objet étudié.We know that in these applications the X-ray multidetectors make it possible to measure the absorption of an X-ray beam passing through an object or an organ, this absorption being linked to the density of the tissues of the organ examined or to the density of the materials constituting the object studied.

Si l'on veut établir la carte de densité d'un organe ou d'un objet, il est possible et connu d'envoyer un faisceau plan de rayons X incidents sur cet objet ou cet organe, ce faisceau présentant une large ouverture angulaire et une faible épaisseur et d'observer pour chaque position des faisceaux de rayons X incidents par rapport à l'objet ou l'organe, l'absorption correspondante. Une multiplicité de balayages dans des directions croisées, permet de connaître grâce au multidétecteur de rayons X, après un traitement numérique approprié des signaux recueillis sur les cellules du détecteur, la valeur de l'absorption des rayons X en un point du plan de coupe considéré, et ainsi de connaître la densité des tissus de l'organe ou la densité des matériaux constituant l'objet.If it is wished to establish the density map of an organ or an object, it is possible and known to send a plane beam of X-rays incident on this object or this organ, this beam having a wide angular opening and a small thickness and observe for each position of the incident X-ray beams with respect to the object or the organ, the corresponding absorption. A multiplicity of scans in crossed directions, makes it possible to know thanks to the X-ray multidetector, after an appropriate digital processing of the signals collected on the cells of the detector, the value of the absorption of X-rays at a point of the section plane considered , and thus to know the density of the tissues of the organ or the density of the materials constituting the object.

Un premier type de multidétecteurs de rayons X à ionisation utilisé en radiographie et en tomographie est multicellulaire et comporte des cellules délimitées par des plaques conductrices perpendiculaires au plan du faisceau de rayons X et portées alternativement à des potentiels positif et négatif. Ces cellules sont situées dans une enceinte étanche contenant un gaz ionisant. Les avantages de ce type de multidétecteur sont les suivants : il procure une bonne collimation des rayons X lorsque les plaques utilisées dans les cellules de détection sont constituées dans un matériau très absorbant ; le temps de collection des charges résultant de l'ionisation du gaz par les rayons X est très faible à cause du faible espacement des plaques conductrices et de la bonne séparation entre les cellules de détection. Cependant, ce type de multidétecteur présente des inconvénients importants : il est très difficile à fabriquer et par conséquent, coûteux. De plus, si l'on désire diminuer l'épaisseur des plaques afin d'augmenter la quantité de rayons X détectés, il y a diminution de la collimation du fait de la faible épaisseur des plaques ; cette faible épaisseur des plaques provoque en outre une microphonie très importante. Enfin, les multidétecteurs de ce type, comme indiqué plus haut, présentent une grande complexité de réalisation qui entraîne un coût de fabrication élevé ils nécessitent un montage en salle dépoussiérée, car toute poussière sur l'une des plaques,,peut provoquer un amorçage ou une détérioration du courant de fuite entre deux plaques consécutives. Il s'ajoute à ces inconvénients que les nombreuses électrodes utilisées nécessitent des connexions électriques très nombreuses, à l'intérieur de la chambre étanche., ce qui pose des problèmes difficiles de fiabilité des soudures des connexions sur les électrodes.A first type of ionization X-ray multidetector used in radiography and tomography is multicellular and comprises cells delimited by conductive plates perpendicular to the plane of the X-ray beam and brought alternately to positive and negative potentials. These cells are located in a sealed enclosure containing an ionizing gas. The advantages of this type of multidetector are as follows: it provides good collimation of X-rays when the plates used in the detection cells are made of a very absorbent material; the collection time of the charges resulting from the ionization of the gas by X-rays is very short because of the small spacing of the conductive plates and the good separation between the detection cells. However, this type of multidetector has significant drawbacks: it is very difficult to manufacture and therefore expensive. In addition, if it is desired to reduce the thickness of the plates in order to increase the quantity of X-rays detected, there is a reduction in collimation due to the small thickness of the plates; this small thickness of the plates also causes a very large microphone. Finally, multidetectors of this type, as indicated above, have a great complexity of production which involves a high manufacturing cost; they require mounting in a dust-free room, because any dust on one of the plates, can cause priming or deterioration of the leakage current between two consecutive plates. It is added to these drawbacks that the numerous electrodes used require very numerous electrical connections, inside the sealed chamber, which poses problems. my difficult reliability of soldering connections on the electrodes.

On connaît un second type de multidétecteur qui présente une structure beaucoup plus simple, mais qui n'est pas parfait. Cet autre type de multidétecteur comprend une chambre étanche contenant un gaz ionisable par des rayons issus de l'organe ou de l'objet et, dans cette chambre, une plaque de collection des électrons résultant de l'ionisation du gaz ; cette plaque est parallèle au plan du faisceau de rayons incidents et elle est portée à une haute tension positive. Une série d'électrodes de collection des ions résultant de l'ionisation du gaz par les rayons X issus de l'objet, est disposée parallèlement et en regard de la plaque précédente ; ces électrodes de collection des ions sont portées à un potentiel voisin de 0 et sont dirigées vers la source qui émet les rayons X, en direction de l'objet. Elles sont situées dans un plan parallèle au plan du faisceau des rayons incidents et fournissent respectivement un courant de mesure fonction. de la quantité d'ions obtenus par l'ionisation du gaz en regard de chaque électrode, sous l'effet des rayons issus de l'objet ou de l'organe, dans une direction correspondant à celle des rayons incidents.A second type of multidetector is known which has a much simpler structure, but which is not perfect. This other type of multidetector comprises a sealed chamber containing a gas ionizable by rays from the organ or object and, in this chamber, a plate for collecting the electrons resulting from the ionization of the gas; this plate is parallel to the plane of the beam of incident rays and it is brought to a positive high voltage. A series of electrodes for collecting the ions resulting from the ionization of the gas by the X-rays coming from the object, is arranged in parallel and facing the preceding plate; these ion collection electrodes are brought to a potential close to 0 and are directed towards the source which emits the X-rays, in the direction of the object. They are located in a plane parallel to the plane of the beam of the incident rays and respectively provide a function measurement current. of the quantity of ions obtained by the ionization of the gas opposite each electrode, under the effect of the rays coming from the object or the organ, in a direction corresponding to that of the incident rays.

Ce type de multidétecteur présente certains avantages : il n'y a plus, comme dans le multidétecteur mentionné précédemment, de plaques de séparation ; ceci élimine tout phénomène gênant de microphonie. Du fait de la suppression de ces plaques de séparation, la quantité de rayons X détectés est maximale ; la réalisation de ce type de multidétecteur est plus simple et il est très peu sensible aux poussières. Enfin, il est possible, sans connexion à l'intérieur de la chambre étanche, de recueillir, à l'intérieur de la chambre les signaux disponibles sur chacune des électrodes portées à un potentiel voisin de 0.This type of multidetector has certain advantages: there are no longer, as in the previously mentioned multidetector, separation plates; this eliminates any annoying phenomenon of microphony. Due to the removal of these separation plates, the quantity of X-rays detected is maximum; the realization of this type of multidetector is simpler and it is very little sensitive to dust. Finally, it is possible, without connection inside the sealed chamber, to re pick up, inside the chamber, the signals available on each of the electrodes brought to a potential close to 0.

Ce type de multidétecteur présente cependant encore une grave difficulté de fabrication car les électrodes sont reliées à des points de mesure extérieurs à l'enceinte, par des connexions qui nécessitent des soudures sur ces électrodes, à l'intérieur de l'enceinte. Ces soudures sont très difficiles à réaliser et le passage de ces connexions à travers l'enceinte pose des problèmes d'étanchéité et d'isolation électrique, très difficiles et très coûteux à résoudre.However, this type of multidetector still presents a serious manufacturing difficulty because the electrodes are connected to measurement points outside the enclosure, by connections which require soldering on these electrodes, inside the enclosure. These welds are very difficult to perform and the passage of these connections through the enclosure poses problems of sealing and electrical insulation, very difficult and very costly to solve.

La présente invention a pour but de remédier à cet inconvénient et notamment de fabriquer un multidétecteur de ce second type, de manière simple et peu coûteuse, sans soudure sur les électrodes à l'intérieur de l'enceinte pour relier celles-ci, par des connexions, à des points extérieurs à l'enceinte.The object of the present invention is to remedy this drawback and in particular to manufacture a multidetector of this second type, in a simple and inexpensive manner, without welding on the electrodes inside the enclosure to connect them, by connections, at points outside the enclosure.

L'invention se rapporte à uri procédé de fabrication d'un multidétecteur de rayons X apte à détecter- notamment les rayons X ayant traversé un objet ou un organe, ces rayons étant fournis par une source émettant un faisceau plan dQ rayons X de faible épaisseur, ce multidétecteur comprenant une enceinte étanche remplie d'un gaz ionisable, et dans cette enceinte, au moins un ensemble multidétecteur principal comportant une plaque plane conductrice, électriquement isolée de l'enceinte, parallèle au faisceau de rayons X et portée à un premier niveau de potentiel, et une pluralité d'électrodes planes parallèles à la plaque, électriquement isolées de cette plaque, ces électrodes étant isolées entre elles, portées à un deuxième niveau de potentiel et s'étendant dans la direction des rayons fournis par la source, procédé caractérisé en ce qu'il consiste à réaliser les électrodes ainsi que des connexions principales entre ces électrodes et des points de mesure extérieurs à l'enceinte permettant de prélever les courants circulant respectivement dans ces électrodes, sur une face principale d'une plaque électriquement isolante, ces connexions principales étant électriquement isolées de l'enceinte et traversant celle-ci de manière étanche, à l'opposé de la source de rayons X à détecter.The invention relates to uri method of manufacturing an X-ray multidetector adapted to détecter- including X rays having passed through an object or organ, these radii being provided by a source emitting a beam of plane Q of low X-ray thickness, this multidetector comprising a sealed enclosure filled with an ionizable gas, and in this enclosure, at least one main multidetector assembly comprising a flat conductive plate, electrically isolated from the enclosure, parallel to the X-ray beam and brought to a first potential level, and a plurality of planar electrodes parallel to the plate, electrically isolated from this plate, these electrodes being isolated from each other, brought to a second potential level and extending in the direction of the rays supplied by the source, method characterized in that it consists in producing the electrodes as well as main connections between these electrodes and measurement points outside the enclosure making it possible to take the currents flowing respectively in these electrodes, on a main face of an electrically insulating plate, these main connections being electrically isolated from the enclosure and passing through it in sealed manner, opposite the source of X-rays to be detected.

Selon une autre caractéristique du procédé, on réalise au moins un autre ensemble multidétecteur secondaire, de structure identique à celle de l'ensemble multidétecteur principal, la plaque de ce multidétecteur secondaire étant portée à un troisième niveau de potentiel et les électrodes étant portées à un deuxième niveau de potentiel, les électrodes de ce multidétecteur secondaire ainsi que des connexions respectives entre ces électrodes et des points secondaires extérieurs à l'enceinte étant réalisées sur une face secondaire de la plaque électriquement isolante, opposée à la face principale, ces connexions secondaires étant électriquement isolées de l'enceinte et traversant celle-ci de manière -étanche à l'opposé de la source de rayons X, le procédé-consistant ensuite à relier respectivement les connexions principales et secondaires.According to another characteristic of the method, at least one other secondary multidetector assembly is produced, with a structure identical to that of the main multidetector assembly, the plate of this secondary multidetector being brought to a third potential level and the electrodes being brought to a second potential level, the electrodes of this secondary multidetector as well as respective connections between these electrodes and secondary points external to the enclosure being made on a secondary face of the electrically insulating plate, opposite to the main face, these secondary connections being electrically isolated from the enclosure and passing through it in a sealed manner opposite to the X-ray source, the process then consisting in connecting the main and secondary connections respectively.

Selon une autre caractéristique, les électrodes et les connexions sont réalisées sous forme de dépôts conducteurs sur la plaque isolante. De préférence, ces dépôts conducteurs sont des dépôts métallisés gravés.According to another characteristic, the electrodes and the connections are made in the form of conductive deposits on the insulating plate. Preferably, these conductive deposits are etched metallized deposits.

L'invention concerne aussi un procédé de fabrication de multidétecteurs de rayons X appartenant à un faisceau plan, caractérisé en ce que l'enceinte étanche est constituée par au moins une plaque électriquement isolante portant les électrodes et les connexions entre ces électrodes et les points de mesure extérieurs, au moins une plaque conductrice, et au moins une entretoise électriquement isolée dont l'intérieur creux forme ladite enceinte et séparant les deux plaques, isolante et conductrice.The invention also relates to a method for manufacturing multiple X-ray detectors providing a flat beam, characterized in that the sealed enclosure is constituted by at least one electrically insulating plate carrying the electrodes and the connections between these electrodes and the external measurement points, at least one conductive plate, and at least one spacer electrically insulated, the hollow interior of which forms said enclosure and separating the two plates, insulating and conducting.

Ce procédé de fabrication permet évidemment encore de réaliser une structure à multidétecteur principal et multidétecteur secondaire, les deux enceintes définies par deux plaques et une entretoise étant superposées et remplies d'un gaz ionisable ; il permet aussi de réaliser une superposition de multidétecteurs, soit à structure simple, soit à structure double (multidétecteur principal et multidétecteur secondaire), permettant d'analyser simultanément plusieurs faisceaux plans parallèles juxtaposés.This manufacturing process obviously still makes it possible to produce a structure with a main multidetector and a secondary multidetector, the two enclosures defined by two plates and a spacer being superimposed and filled with an ionizable gas; it also makes it possible to produce a superimposition of multidetectors, either with a simple structure or with a double structure (main multidetector and secondary multidetector), making it possible to analyze several parallel planar beams juxtaposed simultaneously.

Enfin, l'invention a pour objet un multidétecteur de rayons X obtenu selon le procédé décrit plus haut.Finally, the subject of the invention is an X-ray multidetector obtained according to the method described above.

D'autres caractéristiques et avantages de l'invention ressortiront mieux de la description qui va suivre, donnée en référence aux dessins annexés dans lesquels :

  • - la figure 1 représente schématiquement un multidétecteur de type connu, qu'il est possible de fabriquer selon le procédé de l'invention,
  • - la figure 2 est une vue de face du multidétecteur de la figure 1,
  • - la figure 3 représente schématiquement un multidétecteur d'un autre type connu, qu'il est possible de fabriquer selon le procédé de l'invention,
  • - la figure 4 est une vue latérale du multidétecteur de la figure 3,
  • - la figure 5 est une vue schématique en coupe latérale d'un multidétecteur multicoupe, de fonctionnement comparable à celui du multidétecteur de la figure 3, et qu'il est possible de fabriquer selon le procédé de l'invention,
  • - la figure 6 est une vue de dessus schématique d'une partie des électrodes du multidétecteur de la figure 5.
Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings in which:
  • FIG. 1 schematically represents a multidetector of known type, which it is possible to manufacture according to the method of the invention,
  • FIG. 2 is a front view of the multidetector of FIG. 1,
  • FIG. 3 schematically represents a multidetector of another known type, which it is possible to manufacture according to the method of the invention,
  • FIG. 4 is a side view of the multidetector of FIG. 3,
  • FIG. 5 is a schematic side sectional view of a multicut multidetector, of operation comparable to that of the multidetector of FIG. 3, and which it is possible to manufacture according to the method of the invention,
  • FIG. 6 is a schematic top view of part of the electrodes of the multidetector of FIG. 5.

La figure 1 représente schématiquement et en perspective, un multidétecteur qu'il est possible de fabriquer selon le procédé de l'invention. Ce . multidétecteur comprend une plaque 1 portée à un premier niveau de potentiel (haute tension positive +HT) et, en regard, une série d'électrodes 2 portées à un deuxième niveau de potentiel (voisin de 0 volt). Cette plaque et ces électrodes sont situées dans une chambre principale 3 étanche, représentée schématiquement et qui contient au moins un gaz ionisable, tel que le xénon par exemple. Ce multidétecteur permet de détecter les rayons X qui ont traversé un objet ou un organe 0, ces rayons étant fournis par une source S ponctuelle ou linéaire qui émet en direction de l'objet ou de l'organe, un faisceau F plan de rayons X incidents. Ce faisceau présente une large ouverture angulaire et une faible épaisseur. La plaque 1 est parallèle au plan du faisceau de rayons incidents, tandis que les électrodes planes 2 sont situées dans un plan parallèle au plan du faisceau de rayons incidents, en regard de la plaque 1. La plaque 1 qui est portée à un potentiel positif voisin de quelques kilovolts, est une plaque de collection des électrons, tandis que les électrodes 2 sont des électrodes de collection des ions. Ces électrodes sont généralement portées par une plaque isolante (non représentée sur cette figure) et sont isolées électriquement entre elles. La pression du xénon à l'intérieur de la chambre étanche a une valeur qui est fonction de l'énergie du rayonnement X à détecter (de 1 à 40 bars environ) ; ce gaz peut d'ailleurs être additionné à d'autres gaz destinés à améliorer la détection. Les électrodes 2 forment des bandes convergentes en direction de la source S.Figure 1 shows schematically and in perspective, a multidetector that it is possible to manufacture according to the method of the invention. This. multidetector comprises a plate 1 brought to a first potential level (high positive voltage + HV) and, opposite, a series of electrodes 2 brought to a second potential level (close to 0 volts). This plate and these electrodes are located in a sealed main chamber 3, shown diagrammatically and which contains at least one ionizable gas, such as xenon for example. This multidetector makes it possible to detect the X-rays which have passed through an object or an organ 0, these rays being supplied by a point or linear source S which emits in the direction of the object or the organ, a plane beam F of X-rays incidents. This beam has a wide angular opening and a small thickness. The plate 1 is parallel to the plane of the beam of incident rays, while the plane electrodes 2 are located in a plane parallel to the plane of the beam of incident rays, opposite the plate 1. The plate 1 which is brought to a positive potential neighbor of a few kilovolts, is an electron collection plate, while the electrodes 2 are ion collection electrodes. These electrodes are generally carried by an insulating plate (not shown in this figure) and are electrically isolated from each other. The pressure of the xenon inside the sealed chamber has a value which is a function of the energy of the X-ray to be detected (from 1 to 40 bars approximately); this gas can also be added to other gases intended to improve detection. The electrodes 2 form converging bands in the direction of the source S.

La figure 2 représente schématiquement une vue de face du multidétecteur précédent. On a représenté sur cette figure, la plaque 1 portée à un potentiel positif +HT ainsi que les électrodes 2 portées à un potentiel voisin de 0 volt ; ces électrodes sont supportées par une plaque électriquement isolante 4 et chacune d'elles est reliée à un amplificateur 5 qui permet de prélever le courant circulant dans chacune des électrodes ; ces courants sont appliqués à un système de traitement (non représenté) et de visualisation, qui permet de visualiser le corps ou l'objet 0 traversé par les rayons X émis par la source S. Sur cette figure, on a représenté par des lignes pointillées verticales, les lignes de champ. Dans la chambre 3 contenant au moins du xénon, on a représenté par Xe+ les ions positifs de xénon qui se dirigent vers les électrodes 2 et par e- les électrons qui se dirigent vers la plaque 1 ; ces ions et ces électrons résultant de l'ionisation du xénon par les rayons X issus de l'objet ou de l'organe 0. Dans le cas de l'adjonction d'un gaz électronégatif les électrons sont remplacés par les ions négatifs, formés à partir du gaz additionnel.FIG. 2 schematically represents a front view of the preceding multidetector. This figure shows the plate 1 brought to a positive potential + HT as well as the electrodes 2 brought to a potential close to 0 volts; these electrodes are supported by an electrically insulating plate 4 and each of them is connected to an amplifier 5 which makes it possible to draw the current flowing in each of the electrodes; these currents are applied to a processing (not shown) and visualization system, which makes it possible to visualize the body or object 0 traversed by the X-rays emitted by the source S. In this figure, there are shown by dotted lines vertical, field lines. In chamber 3 containing at least xenon, Xe + represents the positive xenon ions which go towards the electrodes 2 and by e - the electrons which go towards the plate 1; these ions and these electrons resulting from the ionization of xenon by X-rays from the object or organ 0. In the case of the addition of an electronegative gas the electrons are replaced by the negative ions, formed from additional gas.

Selon l'invention, le procédé de fabrication de ce multidétecteur consiste à réaliser les électrodes 2 ainsi que des connexions principales entre ces électrodes et des points extérieurs à l'enceinte, permettant de prélever les courants circulant respectivement dans ces électrodes, sur une face principale d'une plaque 4 électriquement isolante. Ces connexions sont représentées de manière plus complète sur les figures 5 et 6. Ces connexions principales sont électriquement isolées de l'enceinte et traversent celles-ci de manière étanche, à l'opposé de la source.According to the invention, the method of manufacturing this multidetector consists in carrying out the electrodes 2 as well as main connections between these electrodes and points outside the enclosure, making it possible to take the currents flowing respectively in these electrodes, on a main face of an electrically insulating plate 4. These connections are shown more fully in Figures 5 and 6. These main connections are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source.

La figure 3 représente schématiquement et en perspective, un autre multidétecteur obtenu selon le procédé de l'invention. Ce multidétecteur comprend une chambre étanche 6 métallique par exemple contenant au moins un gaz ionisable tel que le xénon par exemple cette chambre se subdivise en deux chambres d'ionisation : une chambre d'ionisation principale 3 et une chambre d'ionisation secondaire 7. La chambre d'ionisation principale 3 contient, comme le multidétecteur de la figure 1, une plaque 1 portée à un premier niveau de potentiel (haute tension positive +HT) et une série d'électrodes 2 portées à un deuxième niveau de potentiel (voisin de 0 volt). La plaque 1 et les électrodes 2 dans la chambre d'ionisation principales 3 forment un ensemble multidétecteur principal. Comme précédemment, ces électrodes sont planes et sont portées par une plaque 4 électriquement isolante ; la plaque 1 ainsi que les électrodes 2 sont situées dans un plan parallèle au plan du faisceau de rayons X issus de l'objet 0 (ce faisceau étant incomplètement représenté sur la figure). Les électrodes 2 convergent dans la direction de la source S. Chacune des électrodes 2 de la chambre d'ionisation principale 3 est reliée à un amplificateur 5 qui permet de prélever., en vue du traitement, le courant circulant dans chacune de ces électrodes. La chambre d'ionisation secondaire 7 est accolée à la chambre principale pour compenser le courant de diffusion provenant des rayons X diffusés par l'organe 0. En effet, comme on le verra plus loin en détail, les électrodes 2 de la chambre d'ionisation principale 3, fournissent respectivement un courant I qui est la somme d'une part, d'un courant de mesure IM proportionnel à la quantité d'ions obtenus par l'ionisation du gaz en regard de chaque électrode de la chambre d'ionisation principale sous l'effet des rayons issus de l'objet, dans des directions correspondant à celle des rayons incidents 9, et d'un courant de diffusion iD résultant de l'ionisation du gaz par les rayons 8 diffusés, notamment par l'objet, dans d'autres directions que celle des rayons incidents. La chambre d'ionisation secondaire 7 contient, comme la chambre d'ionisation principale, une plaque 10 parallèle au plan du faisceau de rayons X incidents, est portée à un troisième niveau de potentiel (haute tension négative -HT), ainsi qu'une série d'électrodes 11 planes, parallèles au plan du faisceau de rayons X in- .cidents, et situées sur une autre face de la plaque isolante 4 qui porte les électrodes 2 de la chambre d'ionisation principale 3. La plaque 10 et les électrodes 11 dans la chambre secondaire 7 forment un ensemble multidétecteur secondaire. Les électrodes 11 sont portées, comme les électrodes 2 de la chambre d'ionisation principale, à un potentiel voisin de 0. Elles sont respectivement reliées par des connexions 12, aux électrodes correspondantes de la chambre d'ionisation principale 3. Les électrodes 11 de la chambre d'ionisation secondaire et les électrodes 2 de la chambre d'ionisation principale sont, de préférence, identiques et situées en regard les unes des autres. La chambre d'ionisation secondaire 7 permet, comme on le verra plus loin en détail, de compenser, pour le traitement ultérieur des courants issus des amplificateurs 5, les courants diffusés qui circulent dans chaque électrode de la chambre d'ionisation principale et qui proviennent des rayons X diffusés par l'objet ou l'organe 0. Les électrodes 11 de la chambre d'ionisation secondaire 7 sont des électrodes de collection des électrons e- ou des ions négatifs, tandis que la plaque 10 est une plaque de collection des ions Xe+ provenant de l'ionisation du xénon contenu dans la chambre secondaire 7, par les rayons X diffusés par l'objet ou l'organe 0. De préférence, les électrodes de la chambre d'ionisation secondaire sont situées en regard des électrodes de la chambre d'ionisation principale et les hautes tensions positive et négative ont la même valeur absolue. La référence 50 désigne un diaphragme.Figure 3 shows schematically and in perspective, another multidetector obtained according to the method of the invention. This multidetector comprises a sealed metal chamber 6 for example containing at least one ionizable gas such as xenon for example this chamber is subdivided into two ionization chambers: a main ionization chamber 3 and a secondary ionization chamber 7. The main ionization chamber 3 contains, like the multidetector of FIG. 1, a plate 1 brought to a first potential level (high positive voltage + HT) and a series of electrodes 2 brought to a second potential level (close to 0 volts). The plate 1 and the electrodes 2 in the main ionization chamber 3 form a main multidetector assembly. As before, these electrodes are planar and are carried by an electrically insulating plate 4; the plate 1 and the electrodes 2 are located in a plane parallel to the plane of the X-ray beam from the object 0 (this beam being incompletely shown in the figure). The electrodes 2 converge in the direction of the source S. Each of the electrodes 2 of the main ionization chamber 3 is connected to an amplifier 5 which makes it possible to take samples. for treatment, the current flowing in each of these electrodes. The secondary ionization chamber 7 is attached to the main chamber to compensate for the diffusion current coming from the X-rays scattered by the member 0. In fact, as will be seen below in detail, the electrodes 2 of the main ionization 3, respectively provide a current I which is the sum of a part, of a measurement current I M proportional to the quantity of ions obtained by the ionization of the gas opposite each electrode of the chamber main ionization under the effect of the rays from the object, in directions corresponding to that of the incident rays 9, and of a diffusion current i D resulting from the ionization of the gas by the rays 8 diffused, in particular by l object, in directions other than that of the incident rays. The secondary ionization chamber 7 contains, like the main ionization chamber, a plate 10 parallel to the plane of the incident X-ray beam, is brought to a third potential level (negative high voltage -HT), as well as a series of planar electrodes 11, parallel to the plane of the incident X-ray beam, and situated on another face of the insulating plate 4 which carries the electrodes 2 of the main ionization chamber 3. The plate 10 and the electrodes 11 in the secondary chamber 7 form a secondary multidetector assembly. The electrodes 11 are brought, like the electrodes 2 of the main ionization chamber, to a potential close to 0. They are respectively connected by connections 12, to the corresponding electrodes of the main ionization chamber 3. The electrodes 11 of the secondary ionization chamber and the electrodes 2 of the main ionization chamber are, preferably identical and located opposite one another. The secondary ionization chamber 7 makes it possible, as will be seen below in detail, to compensate, for the subsequent treatment of the currents originating from the amplifiers 5, the diffused currents which circulate in each electrode of the main ionization chamber and which originate X-rays scattered by the object or organ 0. The electrodes 11 of the secondary ionization chamber 7 are electrodes for collecting electrons e - or negative ions, while the plate 10 is a plate for collecting the Xe + ions from the ionization of the xenon contained in the secondary chamber 7, by the X-rays scattered by the object or the organ 0. Preferably, the electrodes of the secondary ionization chamber are located opposite the electrodes of the main ionization chamber and the high positive and negative voltages have the same absolute value. Reference 50 designates a diaphragm.

La figure 4 représente schématiquement une vue latérale du multidétecteur précédent. Sur cette vue, on distingue la source S, l'objet ou l'organe 0, l'un des rayons 9 émis par la source S et, en sortie de l'objet 0, le rayon direct 13 issu de l'objet 0, dans la même direction que le rayon incident 9 ; on distingue aussi sur cette figure 1!un des rayons diffusés 8, issu de l'objet 0, dans une direction différente de la direction du rayon incident 9. Sur la figure, on a représenté l'une des électrodes 2 de la chambre d'ionisation principale qui est reliée à un amplificateur 5 et qui est portée à un potentiel voisin de 0, et l'une des électrodes 11 de la chambre d'ionisation secondaire 7, qui est située en regard de l'électrode 2 et qui est séparée de cette électrode par la plaque isolante 4. On a également représenté la connexion 12 entre les électrodes des chambres d'ionisation principale et secondaire. Enfin, on a représenté les plaques 1 et 10 des chambres d'ionisation principale et secondaire, portées respectivement à des potentiels positif et négatif +HT et -HT. Sur cette figure, on n'a pas représenté en détail la chambre étanche 6 qui contient le gaz ionisable ; les plaques isolantes 42, 14 supportent les plaques conductrices 1, 10 des chambres d'ionisation principale et secondaire. Lorsque le gaz ionisable est du xénon, les rayons X représentés en 13 et qui sont issus de l'objet, dans la direction des rayons incidents 9, parviennent entre les électrodes 2 et la plaque 1 de la chambre d'ionisation principale ; il se produit alors une ionisation du xénon entre ces électrodes et cette plaque. Cette ionisation est représentée schématiquement sur la figure par des ions Xe+ qui sont attirés par les électrodes 2, et par des électrons e- ou ions négatifs qui sont attirés par la plaque positive 1. Une ionisation se produit ainsi en regard de chacune des électrodes de la chambre d'ionisation principale grâce aux rayons X issus de l'objet, dans la direction des rayons incidents. Ces mouvements d'ions produisent respectivement dans chaque électrode, un courant I qui est la somme d'un courant Im résultant de l'ionisation du gaz en regard de chacune des électrodes, sous l'effet des rayons X issus de l'objet (rayons représentés en 13 sur la figure), dans une direction correspondant à celle des rayons incidents, et d'un courant ID de diffusion, qui résulte de l'ionisation du gaz, en regard de chacune des électrodes, à partir des rayons diffusés par l'objet, dans des directions qui ne correspondent pas à celles des rayons X incidents. La chambre d'ionisation 7 permet de compenser ce courant de diffusion, grâce à l'ionisation que produisent dans cette chambre, les rayons X diffusés 8 ; cette ionisation provoque la circulation, dans les électrodes 11 de la chambre secondaire, d'un courant ID qui vient se retrancher, grâce à la connexion 12, au courant de diffusion parasite pris en compte par les électrodes de la chambre d'ionisation principale. Ainsi, les amplificateurs 5 reliés à chacune des électrodes des chambres d'ionisation principale et secondaire, reçoivent un courant IM qui est effectivement le courant de mesure correspondant à l'ionisation du gaz, provoquée en regard de chacune des électrodes de la chambre d'ionisation principale, par les rayons 13 issus de l'objet ou de l'organe, dans les directions qui correspondent à celles des rayons incidents 9.Figure 4 schematically shows a side view of the previous multidetector. In this view, a distinction is made between the source S, the object or the organ 0, one of the rays 9 emitted by the source S and, at the output of the object 0, the direct ray 13 coming from the object 0 , in the same direction as the incident ray 9; we also distinguish in this figure 1! one of the scattered rays 8, coming from the object 0, in a direction different from the direction of the incident ray 9. In the figure, one of the electrodes 2 of the chamber d is shown. main ionization which is connected to an amplifier 5 and which is brought to a potential close to 0, and one of the electrodes 11 of the secondary ionization chamber 7, which is located opposite the electrode 2 and which is separated from this electrode by the insulating plate 4. The connection 12 between the electrodes of the main and secondary ionization chambers has also been shown. Finally, there are shown the plates 1 and 10 of the main and secondary ionization chambers, brought respectively to positive and negative potentials + HT and -HT. In this figure, the sealed chamber 6 which contains the ionizable gas has not been shown in detail; the insulating plates 42, 14 support the conductive plates 1, 10 of the main and secondary ionization chambers. When the ionizable gas is xenon, the X-rays represented at 13 and which emanate from the object, in the direction of the incident rays 9, reach between the electrodes 2 and the plate 1 of the main ionization chamber; there then occurs an ionization of the xenon between these electrodes and this plate. This ionization is represented diagrammatically in the figure by Xe + ions which are attracted by the electrodes 2, and by electrons e - or negative ions which are attracted by the positive plate 1. An ionization thus occurs opposite each of the electrodes from the main ionization chamber using X-rays from the object, in the direction of the incident rays. These ion movements produce respectively in each electrode, a current I which is the sum of a current I m resulting from the ionization of the gas opposite each of the electrodes, under the effect of X-rays from the object. (rays represented at 13 in the figure), in a direction corresponding to that of the incident rays, and of a diffusion current I D , which results from the ionization of the gas, opposite each of the electrodes, from the rays scattered by the object, in directions which do not correspond to those of the incident X-rays. Bedroom ionization 7 compensates for this diffusion current, thanks to the ionization produced in this chamber, the scattered X-rays 8; this ionization causes the circulation, in the electrodes 11 of the secondary chamber, of a current I D which is cut off, thanks to the connection 12, from the parasitic diffusion current taken into account by the electrodes of the main ionization chamber . Thus, the amplifiers 5 connected to each of the electrodes of the main and secondary ionization chambers, receive a current I M which is effectively the measurement current corresponding to the ionization of the gas, caused opposite each of the electrodes of the chamber d main ionization, by the rays 13 coming from the object or the organ, in the directions which correspond to those of the incident rays 9.

Selon l'invention, le procédé de fabrication de ce multidétecteur consiste, comme pour le multidétecteur de la figure 3, à réaliser sur une face principale 16 de la plaque électriquement isolante 4, les électrodes 2 ainsi que les connexions principales 15 entre ces électrodes et les points de mesure 19 extérieurs à l'enceinte ; ces points de mesure permettent de prélever les courants circulant respectivement dans ces électrodes ; les connexions princpales 15 sont électriquement isolées de l'enceinte et traversent celles-ci de manière étanche, à l'opposé de la source. Le procédé consiste ensuite à réaliser au moins l'autre ensemble multidétecteur secondaire, de structure identique à celle de l'ensemble multidétecteur principal ; la plaque 10 de ce multidétecteur secondaire est portée comme on l'a indiqué plus haut, à une haute tension négative et les électrodes 11 sont portées à un potentiel voisin de 0. Les électrodes 11 de ce multidétecteur secondaire, ainsi que des connexions 17 respectives entre ces électrodes 11 et des points secondaires 20, extérieurs à l'enceinte, sont réalisées sur une face secondaire 18 de la plaque électriquement isolante 4 ; cette face secondaire 18 est opposée à la face principale 4 ; les connexions secondaires 17 sont électriquement isolées de l'enceinte et traversent celles-ci de manière étanche, à l'opposé de la source S ; le procédé consiste ensuite à relier respectivement le point de mesure 19 et les points secondaires 20.According to the invention, the method of manufacturing this multidetector consists, as for the multidetector of FIG. 3, in producing on a main face 16 of the electrically insulating plate 4, the electrodes 2 as well as the main connections 15 between these electrodes and the measurement points 19 outside the enclosure; these measurement points make it possible to take the currents flowing respectively in these electrodes; the main connections 15 are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source. The method then consists in making at least the other secondary multidetector assembly, with a structure identical to that of the main multidetector assembly; the plate 10 of this secondary multidetector is brought, as indicated above, to a negative high voltage and the electrodes 11 are brought to a neighboring potential from 0. The electrodes 11 of this secondary multidetector, as well as respective connections 17 between these electrodes 11 and secondary points 20, external to the enclosure, are produced on a secondary face 18 of the electrically insulating plate 4; this secondary face 18 is opposite to the main face 4; the secondary connections 17 are electrically isolated from the enclosure and pass through them in leaktight manner, opposite the source S; the method then consists in connecting the measurement point 19 and the secondary points 20 respectively.

Les électrodes et les connexions sont réalisées sous forme de dépôts conducteurs sur la plaque isolante- ; de préférence, ces dépôts conducteurs sont des dépôts métallisés gravés sur la plaque isolante. Comme on le verra plus loin en détail, les plaques conductrices 1 et 7 sont portées respectivement à une tension positive +HT et à une haute tension négative -HT, en réalisant une connexion entre chacune de ces plaques et une source de haute tension extérieure à l'enceinte ; cette connexion est électriquement isolée de l'enceinte et la traverse de manière étanche.The electrodes and connections are made in the form of conductive deposits on the insulating plate; preferably, these conductive deposits are metallized deposits etched on the insulating plate. As will be seen below in detail, the conductive plates 1 and 7 are brought respectively to a positive voltage + HT and to a negative high voltage -HT, by making a connection between each of these plates and a high voltage source external to the enclosure; this connection is electrically isolated from the enclosure and crosses it in a sealed manner.

La figure 5 est une vue schématique en coupe latérale, d'un multidétecteur multicoupe, dont le fonctionnement est comparable à celui du multidétecteur de la figure 3 ; ce multidétecteur est fabriqué selon le procédé de l'invention, en empilant une pluralité d'ensembles multidétecteurs principaux et secondaires tels que décrits sur la figure 3.Figure 5 is a schematic side sectional view of a multicut multidetector, the operation of which is comparable to that of the multidetector of Figure 3; this multidetector is manufactured according to the method of the invention, by stacking a plurality of main and secondary multidetector assemblies as described in FIG. 3.

Le multidétecteur de la figure 5 est un empilement de multidétecteurs principaux et secondaires, tels que décrits sur la figure 3. Cet empilement comprend un premier ensemble multidétecteur principal comportant une plaque plane conductrice 1 destinée à être portée à une haute tension positive +HT, électriquement isolée de l'enceinte, (celle-ci pouvant être constituée par exemple par de la résine époxy). Cette plaque plane conductrice est parallèle au faisceau F' de rayons X issus de l'objet ou de l'organe à analyser (non représenté sur cette figure). Ce premier ensemble multidétecteur comprend aussi une pluralité d'électrodes planes 2 parallèles à la plaque 1 et s'étendant dans la direction des rayons X du faisceau F'. Ces électrodes sont isolées entre elles comme on le verra plus loin en détail, et sont portées à un potentiel voisin de 0. Ces électrodes ainsi que des connexions principales 15 entre ces électrodes et des points de mesure 19 extérieurs à l'enceinte permettant de prélever les courants circulant respectivement dans ces électrodes, sont réalisées sur une face 16 de la plaque 4 électriquement isolante. Ces connexions principales 15 sont électriquement isolées de l'enceinte et traversent celle-ci de manière étanche, à l'opposé de la source qui émet le faisceau F' de rayons X. L'enceinte contenant un gaz ionisable, est ici constituée par l'entretoise isolante 21, de résine époxy par exemple, dont l'intérieur creux forme une chambre ; cette entretoise permet de séparer les électrodes 2 et la plaque 1 et la chambre peut contenir du xénon par exemple. Les couvercles 33 et 34 sont prévus en alliage d'aluminium, mais les plaques 10 et 31 sont identiques aux plaques 1, 15 et 10, 14 de la figure 4. Les couvercles 33, 34 pourraient éventuellement s'appuyer de manière étanche sur la plaque 1 et sur la plaque isolante 4, pour former avec les électrodes 2, un multidétecteur élémentaire dont la face avant serait munie d'une fenêtre étanche 38.The multidetector of FIG. 5 is a stack of main and secondary multidetectors, as described in FIG. 3. This stack Lement comprises a first main multidetector assembly comprising a flat conductive plate 1 intended to be brought to a positive high voltage + HT, electrically isolated from the enclosure, (the latter may be constituted for example by epoxy resin). This flat conductive plate is parallel to the beam F 'of X-rays coming from the object or the organ to be analyzed (not shown in this figure). This first multidetector assembly also includes a plurality of planar electrodes 2 parallel to the plate 1 and extending in the direction of the X-rays of the beam F '. These electrodes are isolated from each other as will be seen below in detail, and are brought to a potential close to 0. These electrodes as well as main connections 15 between these electrodes and measurement points 19 outside the enclosure making it possible to take the currents flowing respectively in these electrodes are produced on one face 16 of the electrically insulating plate 4. These main connections 15 are electrically isolated from the enclosure and pass through the latter in leaktight manner, opposite the source which emits the beam F ′ of X-rays. The enclosure containing an ionizable gas is here constituted by l insulating spacer 21, of epoxy resin for example, the hollow interior of which forms a chamber; this spacer makes it possible to separate the electrodes 2 and the plate 1 and the chamber can contain xenon for example. The covers 33 and 34 are provided in aluminum alloy, but the plates 10 and 31 are identical to the plates 1, 15 and 10, 14 of FIG. 4. The covers 33, 34 could possibly rest in a sealed manner on the plate 1 and on the insulating plate 4, to form with the electrodes 2, an elementary multidetector the front face of which would be provided with a sealed window 38.

Selon l'invention, on réalise au moins un autre ensemble multidétecteur secondaire, de structure identique à celle de l'ensemble multidétecteur principal qui vient d'être décrit. La plaque 10 de ce multidétecteur secondaire est portée à une haute tension négative -HT, tandis que les électrodes 11 de ce multidétecteur, dont la structure est identique à celle des électrodes 2 du multidétecteur principal, sont portées à un potentiel voisin de 0. Les électrodes 11 ainsi que les connexions respectives 17 entre ces électrodes et des points secondaires extérieurs à l'enceinte formée par les entretoises 21, 22, sont réalisées sur l'autre face 18 de la plaque électriquement isolante 4. Les connexions secondaires 17 sont électriquement isolées de l'enceinte, celle-ci étant constituée de résine époxy par exemple ; ces connexions traversent l'enceinte formée par les entretoises 21, 22 de manière étanche, à l'opposé de la source émettant le faisceau F' de rayons X. Le procédé consiste ensuite à relier les connexions principales 15 et secondaires 17 aux points de mesure 19, pour chacune des électrodes, par un connecteur 40, représenté schématiquement sur la figure. Si on ferme les entretoises creuses 21, 22 par des couvercles 33, 34 s'appuyant de manière étanche sur les plaques 1 et 10, on obtient un multidétecteur de structure comparable à celui de la figure 3 ; ce multidétecteur permettant de compenser, grâce à l'ensemble secondaire, comme on l'a mentionné plus haut, le courant de diffusion présent dans le courant prélevé sur chacune des électrodes. On peut également afin de réaliser un multidétecteur multicoupes, fabriquer un autre empilement comparable à l'empilement qui vient d'être décrit. Cet autre empilement comprend un multidétecteur principal formé par la plaque 1 portée à la haute tension positive et des électrodes 23 de collections des ions, portées à un potentiel voisin de 0, reliées à des points de mesure 24, par des connexions principales 25 ; les électrodes 23 et les connexions principales 25 sont réalisées, comme précédemment, sur une face 26 d'une plaque électriquement isolante 27. Les électrodes 23 et la plaque 1 sont séparées par une entretoise isolante creuse 28. De la même manière que pour l'empilement précédent, un multidétecteur secondaire est formé de l'autre côté de la plaque isolante 27. Ce multidétecteur secondaire comprend des électrodes 29 portées à un potentiel voisin de 0. Ces électrodes sont isolées entre elles et dirigées dans la direction des rayons du faisceau F'. Elles sont reliées respectivement par des connexions secondaires 30, à des points extérieurs. Cet ensemble multidétecteur secondaire comprend aussi une plaque 31 portée à une haute tension négative -HT et séparée des électrodes 29 par une entretoise isolante 32 ; les différentes entretoises, électrodes et plaques de cet empilement sont rendues solidaires par des couvercles 33, 34 et munis de moyens de fixation 35 ; les couvercles, les entretoises, les plaques et connexions, ainsi que les plaques supportant tes électrodes, sont rendus solidaires de manière que l'ensemble forme un volume creux 36 étanche, contenant du xénon par exemple. Les différentes chambres formées dans ce volume creux peuvent être mises en communication par des ouvertures telles que 37 réalisées dans les plaques supportant les électrodes et dans la plaque 1 portée à la haute tension positive +HT. Les électrodes 29 et la plaque 31 de la chambre secondaire du second empilement, forment une chambre de compensation des courants de diffusion qui viennent perturber les courants mesurés sur les électrodes 23 de la chambre principale de ce second empilement. A cet effet, le connecteur 41 permet de relier respectivement aux points de mesure 24 des électrodes 23 et 29 de ce second empilement. Afin d'assurer la solidité et l'étanchéité du dispositif qui contient du xénon par exemple, à une pression supérieure à 10 atmosphères, une fenêtre étanche 38, maintenue par une bride 39, est disposée sur la face avant du multidétecteur.According to the invention, at least one other secondary multidetector assembly is produced, with a structure identical to that of the main multidetector assembly which has just been described. The plate 10 of this secondary multidetector is brought to a negative high voltage -HT, while the electrodes 11 of this multidetector, whose structure is identical to that of the electrodes 2 of the main multidetector, are brought to a potential close to 0. The electrodes 11 as well as the respective connections 17 between these electrodes and secondary points external to the enclosure formed by the spacers 21, 22, are formed on the other face 18 of the electrically insulating plate 4. The secondary connections 17 are electrically insulated of the enclosure, the latter consisting of epoxy resin for example; these connections pass through the enclosure formed by the spacers 21, 22 in a sealed manner, opposite to the source emitting the beam F ′ of X-rays. The method then consists in connecting the main 15 and secondary 17 connections to the measurement points 19, for each of the electrodes, by a connector 40, shown schematically in the figure. If the hollow spacers 21, 22 are closed by covers 33, 34 pressing in leaktight manner on the plates 1 and 10, a multidetector with a structure comparable to that of FIG. 3 is obtained; this multidetector making it possible to compensate, thanks to the secondary assembly, as mentioned above, the diffusion current present in the current taken from each of the electrodes. It is also possible, in order to produce a multi-cut multidetector, to manufacture another stack comparable to the stack which has just been described. This other stack includes a main multidetector pal formed by the plate 1 brought to the high positive voltage and electrodes 23 of ion collections, brought to a potential close to 0, connected to measurement points 24, by main connections 25; the electrodes 23 and the main connections 25 are made, as before, on a face 26 of an electrically insulating plate 27. The electrodes 23 and the plate 1 are separated by a hollow insulating spacer 28. In the same way as for the previous stack, a secondary multidetector is formed on the other side of the insulating plate 27. This secondary multidetector comprises electrodes 29 brought to a potential close to 0. These electrodes are isolated from each other and directed in the direction of the rays of the beam F '. They are connected respectively by secondary connections 30, to external points. This secondary multidetector assembly also includes a plate 31 brought to a negative high voltage -HT and separated from the electrodes 29 by an insulating spacer 32; the various spacers, electrodes and plates of this stack are made integral by covers 33, 34 and provided with fixing means 35; the covers, the spacers, the plates and connections, as well as the plates supporting your electrodes, are made integral so that the assembly forms a hollow hollow volume 36, containing xenon for example. The different chambers formed in this hollow volume can be brought into communication by openings such as 37 made in the plates supporting the electrodes and in the plate 1 brought to high positive voltage + HT. The electrodes 29 and the plate 31 of the secondary chamber of the second stack form a compensation chamber for the currents of diffusion which disturb the currents measured on the electrodes 23 of the main chamber of this second stack. To this end, the connector 41 makes it possible to connect respectively to the measurement points 24 of the electrodes 23 and 29 of this second stack. In order to ensure the solidity and the tightness of the device which contains xenon for example, at a pressure higher than 10 atmospheres, a watertight window 38, maintained by a flange 39, is arranged on the front face of the multidetector.

Il est bien évident que le détecteur représenté sur cette figure comprend deux empilements qui permettent de réaliser deux coupes parallèles d'un organe ou d'un objet à analyser ; ce multidétecteur pourrait comporter un seul empilement ou plus de deux empilements. Il est bien évident aussi que chaque multidétecteur pourrait ne pas comporter la chambre de compensation des courants de diffusion ; l'invention porte en effet sur la réalisation des électrodes et de leurs connexions avec des points extérieurs, ces électrodes et ces connexions étant réalisées sous forme de dépôts conducteurs sur une plaque isolante. Ces dépôts sont métallisés et gravés sur la plaque isolante.It is obvious that the detector shown in this figure comprises two stacks which make it possible to make two parallel sections of an organ or an object to be analyzed; this multidetector could comprise a single stack or more than two stacks. It is also obvious that each multidetector may not include the diffusion current compensation chamber; the invention relates in fact to the production of the electrodes and their connections with external points, these electrodes and these connections being produced in the form of conductive deposits on an insulating plate. These deposits are metallized and engraved on the insulating plate.

L'invention porte aussi, et surtout, sur la fabrication d'un multidétecteur par empilement de telles plaques isolantes équipées de dépôts conducteurs et d'entretoises isolantes, cet empilement réalisant l'enceinte isolante remplie de gaz détecteur.The invention also relates, and above all, to the manufacture of a multidetector by stacking such insulating plates equipped with conductive deposits and insulating spacers, this stack producing the insulating enclosure filled with detector gas.

La figure 6 est une vue de dessus du détecteur de la figure 5, selon une coupe effectuée au niveau de la plaque 4 par exemple. On distingue sur cette figure, les électrodes 2 dirigées dans la direction des rayons du faisceau F' de rayons X et les connexions principales 15 entre ces électrodes et des points de mesure 19 extérieurs au multidétecteur. On distingue mieux également que les électrodes 2 et les connexions 15 sont réalisées sous forme de dépôts conducteurs sur la plaque isolante 4. Il est bien évident que les électrodes 11, 23 et 29 sont réalisées de la même manière.Figure 6 is a top view of the detector of Figure 5, according to a section taken at the plate 4 for example. We can see in this figure, the electrodes 2 directed in the direction of the rays of the beam F 'of X-rays and the main connections 15 between these electrodes and measurement points 19 outside the multidetector. It is also better to distinguish that the electrodes 2 and the connections 15 are made in the form of conductive deposits on the insulating plate 4. It is obvious that the electrodes 11, 23 and 29 are made in the same way.

Les plaques et électrodes des chambres d'ionisation principale et secondaire de chaque empilement sont réalisées, de préférence, sous forme d'un dépôt de cuivre sur un support isolant.The plates and electrodes of the main and secondary ionization chambers of each stack are preferably produced in the form of a copper deposit on an insulating support.

A titre indicatif, le nombre des cellules de chaque chambre peut être supérieur à 500, pour un angle d'ouverture du faisceau de rayons X supérieur à 40° ; dans ce cas, le pas entre chacune des électrodes de chaque chambre est de 1 mm environ. De préférence, la plaque isolante qui supporte les électrodes des chambres principale et secondaire est située à mi-distance entre les plaques qui sont respectivement portées au potentiel positif et négatif. La distance entre ces plaques est d'environ 14 mm et le temps de collection des ions est voisin de 10 ms.As an indication, the number of cells in each chamber can be greater than 500, for an opening angle of the X-ray beam greater than 40 °; in this case, the pitch between each of the electrodes of each chamber is approximately 1 mm. Preferably, the insulating plate which supports the electrodes of the main and secondary chambers is located midway between the plates which are respectively brought to positive and negative potential. The distance between these plates is approximately 14 mm and the ion collection time is close to 10 ms.

Claims (8)

1. Procédé de fabrication d'un multidétecteur de rayons X apte à détecter un faisceau (F) plan de rayons X de faible épaisseur, ce multidétecteur comprenant une enceinte étanche remplie d'un gaz ionisable et, dans cette enceinte, au moins un ensemble multidétecteur principal comportant une plaque plane conductrice (1), électriquement isolée de l'enceinte, parallèle au faisceau de rayons X et portée à un premier niveau de potentiel (+HT), et une pluralité d'électrodes planes (2) parallèles à la plaque (1), isolées de cette plaque, ces électrodes (2) étant isolées entre elles, portées à un deuxième niveau de potentiel et s'étendant dans la direction des rayons fournis par la source, procédé caractérisé en ce qu'il consiste à réaliser les électrodes (2) ainsi que des connexions principales (15) entre ces électrodes et des points de mesure (19) extérieurs à l'enceinte permettant de prélever les courants circulant respectivement dans ces électrodes, sur une face principale (16) d'une plaque électriquement isolante (4), ces connexions principales étant électriquement isolées de l'enceinte et traversant celle-ci de manière étanche, à l'opposé de la source qui émet les rayons X.1. Method of manufacturing an X-ray multidetector capable of detecting a plane beam (F) of thin X-rays, this multidetector comprising a sealed enclosure filled with an ionizable gas and, in this enclosure, at least one assembly main multidetector comprising a flat conductive plate (1), electrically isolated from the enclosure, parallel to the X-ray beam and brought to a first potential level (+ HT), and a plurality of planar electrodes (2) parallel to the plate (1), isolated from this plate, these electrodes (2) being isolated from each other, brought to a second level of potential and extending in the direction of the rays supplied by the source, method characterized in that it consists in make the electrodes (2) as well as the main connections (15) between these electrodes and measurement points (19) outside the enclosure making it possible to take the currents flowing respectively in these electrodes, on a main face (16) of a plate electrically insulating (4), these main connections being electrically isolated from the enclosure and passing through it in leaktight manner, opposite to the source which emits X-rays. 2. Procédé selon la revendication 1, caractérisé en ce qu'il consiste à réaliser au moins un autre ensemble multidétecteur secondaire, de structure identique à celle de l'ensemble multidétecteur principal, la plaque (10) de ce multidétecteur secondaire étant portée à un troisième niveau de potentiel (-HT) et les électrodes (11) étant portées à un deuxième niveau de potentiel, les électrodes (11) de ce multidétecteur secondaire ainsi que des connexions (17) respectives entre ces électrodes (11) et des points secondaires extérieurs à l'enceinte étant réalisées sur une face secondaire (18) de la plaque électriquement isolante (4), opposée à la face principale (16), ces connexions secondaires étant électriquement isolées de l'enceinte (21, 22, 34, 35, 38) et traversant celle-ci de manière étanche à l'opposé de la source de rayonx X, le procédé consistant ensuite à relier respectivement les connexions principales et secondaires.2. Method according to claim 1, characterized in that it consists in producing at least one other secondary multidetector assembly, of structure identical to that of the main multidetector assembly, the plate (10) of this secondary multidetector being brought to a third potential level (-HT) and the electrodes (11) being brought to a second potential level, the electrodes (11) of this secondary multidetector as well as respective connections (17) between these electrodes (11) and secondary points outside the in this enclosure being produced on a secondary face (18) of the electrically insulating plate (4), opposite to the main face (16), these secondary connections being electrically isolated from the enclosure (21, 22, 34, 35, 38) and passing through it in a sealed manner opposite the x-ray source, the method then consisting in connecting the main and secondary connections respectively. 3. Procédé selon l'une quelconque des revendications 1 et 2, caractérisé en ce que les électrodes et les connexions sont réalisées sous forme de dépôts conducteurs sur la plaque isolante.3. Method according to any one of claims 1 and 2, characterized in that the electrodes and the connections are made in the form of conductive deposits on the insulating plate. 4. Procédé selon la revendication 3, caractérisé en ce que les dépôts conducteurs sont des dépôts métallisés gravés sur la plaque isolante.4. Method according to claim 3, characterized in that the conductive deposits are metallized deposits etched on the insulating plate. 5. Procédé selon la revendication 4, caractérisé en ce qu'il consiste à porter chaque plaque conductrice à la haute tension en réalisant une connexion entre cette plaque et une source de haute tension extérieure à l'enceinte, cette connexion étant électriquement isolée de l'enceinte et la traversant de manière étanche.5. Method according to claim 4, characterized in that it consists in bringing each conductive plate to the high voltage by making a connection between this plate and a high voltage source external to the enclosure, this connection being electrically isolated from the enclosure and crossing it tightly. 6. Procédé selon la revendication 5, caractérisé en ce qu'il consiste à empiler une pluralité d'ensemble multidétecteurs principaux et secondaires.6. Method according to claim 5, characterized in that it consists in stacking a plurality of main and secondary multidetector assemblies. 7. Procédé de fabrication d'un multidétecteur de rayons X selon l'une au moins des revendications 1 à 6, caractérisé en ce que l'enceinte étanche est constituée par au moins une plaque électriquement isolante (4) portant les électrodes (2) et les connexions (15) entre ces électrodes et les points de mesure extérieurs, au moins une plaque conductrice (10), et au moins une entretoise isolante (22), électriquement isolée des électrodes et de la plaque conductrice et séparant les deux plaques isolante et conductrice, dont l'intérieur creux forme ladite enceinte.7. A method of manufacturing an X-ray multidetector according to at least one of claims 1 to 6, characterized in that the sealed enclosure is constituted by at least one electrically insulating plate (4) carrying the electrodes (2) and the connections (15) between these electrodes and the external measurement points, at least one conductive plate (10), and at least one insulating spacer (22), electrically isolated from the electrodes and of the conductive plate and separating the two insulating and conductive plates, the hollow interior of which forms said enclosure. 8. Multidétecteur de rayons X obtenu par le procédé selon l'une au moins des revendications 1 à 7.8. X-ray multi-detector obtained by the method according to at least one of claims 1 to 7.
EP82400769A 1981-05-06 1982-04-28 X-rays multidetector Expired EP0064913B1 (en)

Applications Claiming Priority (2)

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FR8109000A FR2505492B1 (en) 1981-05-06 1981-05-06
FR8109000 1981-05-06

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EP0064913A2 true EP0064913A2 (en) 1982-11-17
EP0064913A3 EP0064913A3 (en) 1983-08-03
EP0064913B1 EP0064913B1 (en) 1986-04-02

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US (1) US4481420A (en)
EP (1) EP0064913B1 (en)
JP (1) JPS57187679A (en)
DE (1) DE3270211D1 (en)
FR (1) FR2505492B1 (en)

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GB2187328A (en) * 1986-02-27 1987-09-03 Gen Electric Ionization detector
GB2189932A (en) * 1983-12-27 1987-11-04 Gen Electric Ionization detector
FR2626379A1 (en) * 1988-01-26 1989-07-28 Commissariat Energie Atomique DETECTOR FOR X-RAY TOMOGRAPHY

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EP0063705A2 (en) * 1981-04-24 1982-11-03 General Electric Company High pressure, high resolution xenon x-ray detector array
EP0063705A3 (en) * 1981-04-24 1985-01-30 General Electric Company High pressure, high resolution xenon x-ray detector array
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GB2187328B (en) * 1986-02-27 1990-07-18 Gen Electric Ionization detector
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Also Published As

Publication number Publication date
EP0064913B1 (en) 1986-04-02
US4481420A (en) 1984-11-06
FR2505492A1 (en) 1982-11-12
JPS57187679A (en) 1982-11-18
DE3270211D1 (en) 1986-05-07
EP0064913A3 (en) 1983-08-03
FR2505492B1 (en) 1985-11-08

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