EP0186558B1 - Device for the irradiation of matter by an electron beam - Google Patents

Device for the irradiation of matter by an electron beam Download PDF

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Publication number
EP0186558B1
EP0186558B1 EP85402371A EP85402371A EP0186558B1 EP 0186558 B1 EP0186558 B1 EP 0186558B1 EP 85402371 A EP85402371 A EP 85402371A EP 85402371 A EP85402371 A EP 85402371A EP 0186558 B1 EP0186558 B1 EP 0186558B1
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EP
European Patent Office
Prior art keywords
window
slot
irradiated
axis
enclosure
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Expired
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EP85402371A
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German (de)
French (fr)
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EP0186558A1 (en
Inventor
Michel Roche
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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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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K5/00—Irradiation devices
    • G21K5/04—Irradiation devices with beam-forming means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J33/00—Discharge tubes with provision for emergence of electrons or ions from the vessel; Lenard tubes

Definitions

  • the present invention relates to a device for irradiating matter with an electron beam.
  • the gases are irradiated for chemical uses or for sterilization.
  • Liquids are also irradiated for chemical or food uses (sterilization of fruit juices, milk, water, etc.).
  • the solids are irradiated for chemical (polymerization), medical (sterilization), food (irradiation of seeds, fruits, potatoes, vegetables, etc.), genetic (irradiation of seeds, insects, etc.) uses.
  • Various devices are known for irradiating matter with an electron beam.
  • FR-A 2 428 913 provides an electron beam in a plane passing through an outlet window closed by a thin metal membrane. It belongs to an enclosure in which a vacuum has been created and in which is located an electron gun emitting a very flattened and very elongated beam; this window can have a length of 2 meters for a width of a few centimeters. The displacement of the electrons must be perpendicular to the surface of the window, in order to cross it in the best conditions.
  • electron accelerators have been designed enabling the electrons of a laminar beam to be directly accelerated by using either electron guns in which the electron source consists of a very elongated filament, or devices with plasma in which the electrons are obtained by secondary emission from ions coming from a filiform anode.
  • the invention aims to remedy these drawbacks and in particular to produce a device for irradiating material with an electron beam, in which it is possible to use an emissive filament of small dimension, which is easy to change, the beam being planar and propagating all around an axis, on 360 ° , thus facilitating the use of the device for industrial applications.
  • This very simple device is also inexpensive.
  • the subject of the invention is a device for irradiating material with an electron beam comprising an electron gun and guide means for placing the material on the path of the beam, characterized in that the electron gun comprises, in an enclosure watertight having a shape having a symmetry of revolution with respect to an axis, an electron-emitting filament situated in the axis of the enclosure and, coaxially, a Wehnelt electrode surrounding the filament having a symmetry of revolution with respect to said axis and comprising a first circular electron concentration slot in the vicinity of the plane perpendicular to the axis and passing through the first slot which is located opposite the filament, at least one electrode for accelerating the electrons surrounding the Wehnelt electrode, having a symmetry of revolution with respect to said axis and comprising a second circular slot situated opposite the first slot, the enclosure comprising a window c circular closed in a sealed and transparent manner to the electrons, this window being located opposite the two slots, the guide means placing the material to be irradiated around the window.
  • the Wehnelt electrode comprises two truncated cones each having a large base and a small circular base perpendicular to the axis, the respective small bases of the two truncated cones being located opposite one another and being spaced apart to constitute said first slot, the truncated cones comprising housings located opposite and in the vicinity of the first slot and containing said filament.
  • said window is closed by a metal sheet having a section in the form of a gutter, penetrating towards the interior of the enclosure.
  • the first slot is surrounded on the periphery of the small bases of each of the two cones, for a circular grid.
  • the guide means comprise an annular hollow sheath with two concentric walls surrounding said window, the material to be irradiated circulating in this sheath.
  • one of the walls of the sheath is partially formed by the external surface of the sealed enclosure and by the sheet closing the window.
  • the guide means comprise a hopper surrounding the barrel and in which the material to be irradiated circulates.
  • the guide means comprise an assembly for displacing the material to be irradiated in order to cause it to flow opposite said window.
  • the material to be irradiated being in the form of a strip wound to form a roll having the width of the ribbon
  • the guide means comprise means for unwinding this ribbon by making it circulate in the direction of its length and so that it forms a sheath around the window, folding it in the direction of its width.
  • Figure 1 shows schematically and in longitudinal section, an irradiation device according to the invention.
  • This device comprises an electron gun located in a sealed enclosure 1, and guide means for placing the material to be irradiated on the path of the electron beam. These guide means are not shown in this figure and will be described later in detail.
  • the enclosure 1 has a symmetry of revolution with respect to an axis X'X.
  • symmetry of revolution is understood to mean the surface obtained by rotation of a curve or of a straight line about an axis.
  • the electron gun comprises, in the sealed enclosure 1, an emissive filament 2 connected by plug-in connectors 3, 4, and by conductive wires 5, 6, to a negative high voltage -V '.
  • This emissive filament has the shape of a coil whose axis corresponds to the X'X axis of the enclosure.
  • the barrel also comprises, coaxially, a Wehnelt electrode in two parts 7, 8, which surround the filament 2, and which has a symmetry of revolution with respect to the axis X'X.
  • This Whenelt electrode has a first circular slot 9, which allows the electrons to be concentrated in the vicinity of a plane P perpendicular to the axis X'X and passing through the slot 9.
  • This slot is located opposite the filament 2; the concentration of the electrons is produced by the electric field appearing in the slit when the Wehnelt electrode 7 is supplied by a negative high voltage -V; the absolute value of the voltage -V is slightly higher than the absolute value of the voltage -V 'supplying the filament.
  • the device also comprises an electrode 10 for accelerating the electrons; this electrode surrounds the Wehnelt electrode 7, 8 and it also has a symmetry of revolution with respect to the axis X'X of the enclosure. The potential of this electrode can be equal to that of the enclosure; in practice, this potential is that of a reference electrical ground.
  • the acceleration electrode 10 has a second circular slot 11, located opposite the first slot 9. The electron beam emitted by the filament, in the vicinity of the plane P, is shown at 12.
  • the two parts 7, 8 of the Wehnelt electrode are connected, for example by a conductive threaded rod 13, integral with part 8 of the Wehnelt.
  • the enclosure 1 is provided with a circular window 14, closed in a sealed manner by a metal sheet having a section in the form of a gutter, penetrating towards the interior of the enclosure.
  • This window is located opposite the slots 9, 11; it is transparent to electrons.
  • the guide means which are not shown in this figure, place the material to be irradiated around the window.
  • the two parts 7, 8 of the Wehnelt electrode form two truncated cones which each have a large base and a small base.
  • the large bases of these truncated cones are respectively referenced 16, 7, while the small bases are respectively referenced 18, 19 in the figure.
  • the small bases 18, 19 of the two truncated cones are located opposite one another and they are spaced so as to constitute the first slot 9.
  • These two truncated cones respectively comprise housings 20, 21 which are located facing each other, in the vicinity of the first slot 9.
  • These housings contain the emissive filament 2.
  • the first slot 9 can be surrounded on the periphery of the small bases 18, 19 of each of the two cones, by a circular grid 22.
  • the two parts 7, 8 of the Wehnelt are connected by the threaded rod 13 and by a rod 23, to the voltage source -V, through elements such as 24, 25, of an insulator.
  • the connection wires 5, 6 of the filament pass through a bore 26 of the rod 23 then the element 25 of the insulator, to be connected to the voltage source -V '.
  • the vacuum prevailing inside the enclosure 1 the crossings of the conductors 5, 6 and 27 are sealed.
  • the elements 24 of the insulator are separated by conductive washers 28, connected by resistors 29 making it possible to make the various elements of the insulator equipotential.
  • the sealed enclosure 1 can be closed by a sealed cover 30. This removable cover provides access to the interior of the enclosure, so as, for example, to replace the filament 2 in the event of destruction thereof.
  • FIGS. 2 to 5 represent different embodiments which make it possible to place the material to be irradiated on the path of the electron beam produced in a plane P, passing through the window 14.
  • the cannon has been designated by the reference C electrons.
  • the enclosure containing the various elements of the barrel is represented by the reference 1, and the window by the reference 14.
  • these means comprise a hollow annular sheath 31 with two concentric walls 31 a, 32b.
  • the material to be irradiated circulates between these two walls, as indicated by the arrows in the figure.
  • This material can be a liquid or a gas, or even a powdered solid.
  • the internal wall 31 of the sheath can be constituted at least partially by the external surface of the sealed enclosure 1, and by the metal sheet which closes the window 14. Under these conditions, the materials to be irradiated directly receive the electron beam emitted in plan P.
  • the electron gun C is placed in a hopper 33, the upper part of which, for example, has a flared shape, favoring the reception of the materials to be irradiated. These materials are in direct contact with the metal sheet which closes the window 14 of the enclosure 1.
  • the pressure P of the material to be irradiated is of the order of a few bars, and if the window is formed from a titanium sheet 20 microns thick, the radius of curvature p of this window does not exceed a few centimeters.
  • FIG. 4 represents a third embodiment of the means for guiding the material to be irradiated.
  • these guide means consist of an assembly 34 which makes it possible to move the irradiated material, so as to cause it to circulate opposite the window 14.
  • these guide means are constituted for example by a conveyor belt or a chain.
  • FIG. 5 represents a fourth embodiment of the means for guiding the material to be irradiated.
  • the material to be irradiated is in the form of a strip 36, wound to form a roll 37 having the width of the ribbon.
  • the guide means here comprise a motor 37 driving an axis 38 on which the ribbon 36 is wound after being irradiated by the electron gun C.
  • the ribbon circulates lengthwise, as indicated by the arrows; the guide means comprise guides 39, 40, 41, 42 which allow the tape to form a sheath around the window 14 and the enclosure 1, by folding it around this enclosure, in the direction of the width of the tape .
  • the ribbon is thus unwound around the axis 42 and wound around the axis 38.
  • the part 43 is used to hold the device.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Apparatus For Disinfection Or Sterilisation (AREA)

Description

La présente invention concerne un dispositif d'irradiation de matière par un faisceau électronique.The present invention relates to a device for irradiating matter with an electron beam.

Elle s'applique à l'irradiation de gaz, de liquides ou de solides. Les gaz sont irradiés pour des utilisations chimiques ou pour la stérilisation. Les liquides sont eux aussi irradiés pour des utilisations chimiques ou alimentaires (stérilisation des jus de fruits, du lait, de l'eau, etc.). Les solides sont irradiés pour des utilisations chimiques (polymérisation), médicales (stérilisation), alimentaires (irradiation de graines, fruits, pommes de terre, légumes, etc.), génétiques (irradiation de semences, insectes, etc.).It applies to the irradiation of gases, liquids or solids. The gases are irradiated for chemical uses or for sterilization. Liquids are also irradiated for chemical or food uses (sterilization of fruit juices, milk, water, etc.). The solids are irradiated for chemical (polymerization), medical (sterilization), food (irradiation of seeds, fruits, potatoes, vegetables, etc.), genetic (irradiation of seeds, insects, etc.) uses.

On connaît divers dispositifs d'irradiation de matière par un faisceau électronique. Parmi ces dispositifs, l'un d'eux (FR-A 2 428 913) fournit un faisceau électronique dans un plan passant par une fenêtre de sortie fermée par une membrane métallique mince. Elle appartient à une enceinte dans laquelle on a réalisé le vide et dans laquelle est situé un canon à électrons émettant un faisceau très aplati et très allongé; cette fenêtre peut présenter une longueur de 2 mètres pour une largeur de quelques centimètres. Le déplacement des électrons doit être perpendiculaire à la surface de la fenêtre, afin de la traverser dans les meilleures conditions.Various devices are known for irradiating matter with an electron beam. Among these devices, one of them (FR-A 2 428 913) provides an electron beam in a plane passing through an outlet window closed by a thin metal membrane. It belongs to an enclosure in which a vacuum has been created and in which is located an electron gun emitting a very flattened and very elongated beam; this window can have a length of 2 meters for a width of a few centimeters. The displacement of the electrons must be perpendicular to the surface of the window, in order to cross it in the best conditions.

Il est possible de produire un faisceau électronique plan à partir d'un faisceau électronique ponctuel qui est animé, grâce à un système de balayage, d'un mouvement linéaire alternatif devant la fenêtre. Un dispositif de ce type a pour principal inconvénient de nécessiter l'utilisation d'un système de balayage et de limiter l'utilisation des électrons dans une zone linéaire voisine de la fenêtre.It is possible to produce a plane electron beam from a point electron beam which is animated, by means of a scanning system, with an alternating linear movement in front of the window. The main drawback of a device of this type is that it requires the use of a scanning system and limits the use of electrons in a linear region close to the window.

Plus récemment, ont été conçus des accélérateurs d'électrons permettant d'accélérer directement les électrons d'un faisceau laminaire en utilisant, soit des canons à électrons dans lesquels la source d'électrons est constituée par un filament très allongé, soit des dispositifs à plasma dans lesquels les électrons sont obtenus par émission secondaire à partir d'ions issus d'une anode filiforme.More recently, electron accelerators have been designed enabling the electrons of a laminar beam to be directly accelerated by using either electron guns in which the electron source consists of a very elongated filament, or devices with plasma in which the electrons are obtained by secondary emission from ions coming from a filiform anode.

Ces différents dispositifs qui permettent d'obtenir un faisceau plan d'électrons, présentent de nombreux inconvénients: dans le dispositif à balayage, il est nécessaire, pour limiter l'incidence des électrons aux extrémités de la fenêtre, de construire des dispositifs présentant un encombrement prohibitif. Dans les dispositifs qui utilisent des canons à électrons ayant un filament très allongé, il est difficile de remplacer ces filaments émissifs, lorsqu'ils sont détériorés. Dans le dispositif à plasma, il est difficile d'obtenir un faisceau uniforme et, par conséquent, une irradiation uniforme. Ces dispositifs sont d'autre part complexes et coûteux.These various devices which make it possible to obtain a plane beam of electrons, have numerous drawbacks: in the scanning device, it is necessary, in order to limit the incidence of electrons at the ends of the window, to build devices having a bulk prohibitive. In devices that use electron guns with a very elongated filament, it is difficult to replace these emissive filaments when they are damaged. In the plasma device, it is difficult to obtain a uniform beam and, therefore, uniform irradiation. These devices are also complex and expensive.

L'invention a pour but de remédier à ces inconvénients et notamment de réaliser un dispositif d'irradiation de matière par un faisceau électronique, dans lequel il est possible d'utiliser un filament émissif de faible dimension, qui est facile à changer, le faisceau étant plan et se propageant tout autour d'un axe, sur 360°, facilitant ainsi l'utilisation du dispositif pour des applications industrielles. Ce dispositif qui est très simple est aussi peu coûteux.The invention aims to remedy these drawbacks and in particular to produce a device for irradiating material with an electron beam, in which it is possible to use an emissive filament of small dimension, which is easy to change, the beam being planar and propagating all around an axis, on 360 ° , thus facilitating the use of the device for industrial applications. This very simple device is also inexpensive.

L'invention a pour objet un dispositif d'irradiation de matière par un faisceau électronique comprenant un canon à électrons et des moyens de guidage pour placer la matière sur le parcours du faisceau, caractérisé en ce que le canon à électrons comprend, dans une enceinte étanche ayant une forme présentant une symétrie de révolution par rapport à un axe, un filament émissif d'électrons situé dans l'axe de l'enceinte et, coaxialement, une électrode de Wehnelt entourant le filament présentant une symétrie de révolution par rapport audit axe et comprenant une première fente circulaire de concentration des électrons au voisinage du plan perpendiculaire à l'axe et passant par la première fente qui est située en regard du filament, au moins une électrode d'accélération des électrons entourant l'électrode de Wehnelt, présentant une symétrie de révolution par rapport audit axe et comprenant une deuxième fente circulaire située en regard de la première fente, l'enceinte comprenant une fenêtre circulaire fermée de façon étanche et transparente aux électrons, cette fenêtre étant située en regard des deux fentes, les moyens de guidage plaçant la matière à irradier autour de la fenêtre.The subject of the invention is a device for irradiating material with an electron beam comprising an electron gun and guide means for placing the material on the path of the beam, characterized in that the electron gun comprises, in an enclosure watertight having a shape having a symmetry of revolution with respect to an axis, an electron-emitting filament situated in the axis of the enclosure and, coaxially, a Wehnelt electrode surrounding the filament having a symmetry of revolution with respect to said axis and comprising a first circular electron concentration slot in the vicinity of the plane perpendicular to the axis and passing through the first slot which is located opposite the filament, at least one electrode for accelerating the electrons surrounding the Wehnelt electrode, having a symmetry of revolution with respect to said axis and comprising a second circular slot situated opposite the first slot, the enclosure comprising a window c circular closed in a sealed and transparent manner to the electrons, this window being located opposite the two slots, the guide means placing the material to be irradiated around the window.

Selon une autre caractéristique, l'électrode Wehnelt comprend deux troncs de cône présentant chacun une grande base et une petite base circulaires perpendiculaires à l'axe, les petites bases respectives des deux troncs de cône étant situées en regard l'une de l'autre et étant espacées pour constituer ladite première fente, les troncs de cône comprenant des logements situés en regard et au voisinage de la première fente et contenant ledit filament.According to another characteristic, the Wehnelt electrode comprises two truncated cones each having a large base and a small circular base perpendicular to the axis, the respective small bases of the two truncated cones being located opposite one another and being spaced apart to constitute said first slot, the truncated cones comprising housings located opposite and in the vicinity of the first slot and containing said filament.

Selon une autre caractéristique, ladite fenêtre est fermée par une feuille métallique présentant une section en forme de gouttière, pénétrant vers l'intérieur de l'enceinte.According to another characteristic, said window is closed by a metal sheet having a section in the form of a gutter, penetrating towards the interior of the enclosure.

Selon une autre caractéristique, la première fente est entourée sur le pourtour des petites bases de chacun des deux cônes, pour une grille circulaire.According to another characteristic, the first slot is surrounded on the periphery of the small bases of each of the two cones, for a circular grid.

Selon une autre caractéristique, les moyens de guidage comprennent une gaine creuse annulaire à deux parois concentriques entourant ladite fenêtre, la matière à irradier circulant dans cette gaine.According to another characteristic, the guide means comprise an annular hollow sheath with two concentric walls surrounding said window, the material to be irradiated circulating in this sheath.

Selon une autre caractéristique, l'une des parois de la gaine est constituée partiellement par la surface externe de l'enceinte étanche et par la feuille fermant la fenêtre.According to another characteristic, one of the walls of the sheath is partially formed by the external surface of the sealed enclosure and by the sheet closing the window.

Selon une autre caractéristique, les moyens de guidage comprennent une trémie entourant le canon et dans laquelle circule la matière à irradier.According to another characteristic, the guide means comprise a hopper surrounding the barrel and in which the material to be irradiated circulates.

Selon une autre caractéristique, les moyens de guidage comprennent un ensemble de déplacement de la matière à irradier pour l'amener à circuler en regard de ladite fenêtre.According to another characteristic, the guide means comprise an assembly for displacing the material to be irradiated in order to cause it to flow opposite said window.

Selon une autre caractéristique, la matière à irradier se présentant sous la forme d'une bande enroulée pour former un rouleau ayant la largeur du ruban, les moyens de guidage comprennent des moyens pour dérouler ce ruban en le faisant circuler dans la direction de sa longueur et pour qu'il forme un fourreau autour de la fenêtre, en le repliant dans la direction de sa largeur.According to another characteristic, the material to be irradiated being in the form of a strip wound to form a roll having the width of the ribbon, the guide means comprise means for unwinding this ribbon by making it circulate in the direction of its length and so that it forms a sheath around the window, folding it in the direction of its width.

Les 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 et en coupe longitudinale, un dispositif d'irradiation conforme à l'invention,
  • - la figure 2 représente schématiquement un premier mode de réalisation des moyens de guidage de la matière à irradier,
  • - la figure 3 représente schématiquement un deuxième mode de réalisation de ces moyens de guidage,
  • - la figure 4 représente schématiquement un troisième mode de réalisation des moyens de guidage de la matière à irradier,
  • - la figure 5 représente schématiquement un quatrième mode de réalisation des moyens de guidage.
The 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 shows schematically and in longitudinal section, an irradiation device according to the invention,
  • FIG. 2 schematically represents a first embodiment of the means for guiding the material to be irradiated,
  • FIG. 3 schematically represents a second embodiment of these guide means,
  • FIG. 4 schematically represents a third embodiment of the means for guiding the material to be irradiated,
  • - Figure 5 shows schematically a fourth embodiment of the guide means.

La figure 1 représente schématiquement et en coupe longitudinale, un dispositif d'irradiation conforme l'invention. Ce dispositif comprend un canon à électrons situé dans une enceinte étanche 1, et des moyens de guidage pour placer la matière à irradier sur le parcours du faisceau électronique. Ces moyens de guidage ne sont pas représentés sur cette figure et seront décrits plus loin en détail. L'enceinte 1 présente une symétrie de révolution par rapport à un axe X'X. Dans la suite de la description, on entend par symétrie de révolution, la surface obtenue par rotation d'une courbe ou d'une droite autour d'un axe.Figure 1 shows schematically and in longitudinal section, an irradiation device according to the invention. This device comprises an electron gun located in a sealed enclosure 1, and guide means for placing the material to be irradiated on the path of the electron beam. These guide means are not shown in this figure and will be described later in detail. The enclosure 1 has a symmetry of revolution with respect to an axis X'X. In the following description, the expression “symmetry of revolution” is understood to mean the surface obtained by rotation of a curve or of a straight line about an axis.

Le canon à électrons comprend, dans l'enceinte étanche 1, un filament émissif 2 relié par des connecteurs enfichables 3, 4, et par des fils conducteurs 5, 6, à une haute tension négative -V'. Ce filament émissif a la forme d'une bobine dont l'axe correspond à l'axe X'X de l'enceinte. Le canon comprend aussi, coaxialement, une électrode de Wehnelt en deux parties 7, 8, qui entourent le filament 2, et qui présente une symétrie de révolution par rapport à l'axe X'X. Cette électrode de Whenelt comporte une première fente 9 circulaire, qui permet de concentrer les électrons au voisinage d'un plan P perpendiculaire à l'axe X'X et passant par la fente 9. Cette fente est située en regard du filament 2; la concentration des électrons est produite par le champ électrique apparaissant dans la fente lorsque l'électrode de Wehnelt 7 est alimentée par une haute tension négative -V; la valeur absolue de la tension -V est légèrement supérieure à la valeur absolue de la tension -V' alimentant le filament. Le dispositif comprend aussi une électrode 10 d'accélération des électrons; cette électrode entoure l'électrode de Wehnelt 7, 8 et elle présente aussi une symétrie de révolution par rapport à l'axe X'X de l'enceinte. Le potentiel de cette électrode peut être égal à celui de l'enceinte; dans la pratique, ce potentiel est celui d'une masse électrique de référence. L'électrode d'accélération 10 présente une deuxième fente circulaire 11, située en regard de la première fente 9. Le faisceau d'électrons émis par le filament, au voisinage du plan P, est représenté en 12. Les deux parties 7, 8 de l'électrode de Wehnelt sont reliées, par exemple par une tige filetée conductrice 13, solidaire de la partie 8 du Wehnelt.The electron gun comprises, in the sealed enclosure 1, an emissive filament 2 connected by plug-in connectors 3, 4, and by conductive wires 5, 6, to a negative high voltage -V '. This emissive filament has the shape of a coil whose axis corresponds to the X'X axis of the enclosure. The barrel also comprises, coaxially, a Wehnelt electrode in two parts 7, 8, which surround the filament 2, and which has a symmetry of revolution with respect to the axis X'X. This Whenelt electrode has a first circular slot 9, which allows the electrons to be concentrated in the vicinity of a plane P perpendicular to the axis X'X and passing through the slot 9. This slot is located opposite the filament 2; the concentration of the electrons is produced by the electric field appearing in the slit when the Wehnelt electrode 7 is supplied by a negative high voltage -V; the absolute value of the voltage -V is slightly higher than the absolute value of the voltage -V 'supplying the filament. The device also comprises an electrode 10 for accelerating the electrons; this electrode surrounds the Wehnelt electrode 7, 8 and it also has a symmetry of revolution with respect to the axis X'X of the enclosure. The potential of this electrode can be equal to that of the enclosure; in practice, this potential is that of a reference electrical ground. The acceleration electrode 10 has a second circular slot 11, located opposite the first slot 9. The electron beam emitted by the filament, in the vicinity of the plane P, is shown at 12. The two parts 7, 8 of the Wehnelt electrode are connected, for example by a conductive threaded rod 13, integral with part 8 of the Wehnelt.

Enfin, l'enceinte 1 est munie d'une fenêtre circulaire 14, fermée de façon étanche par une feuille métallique présentant une section en forme de gouttière, pénétrant vers l'intérieur de l'enceinte. Cette fenêtre est située en regard des fentes 9, 11; elle est transparente aux électrons. Les moyens de guidage, qui ne sont pas représentés sur cette figure, placent la matière à irradier autour de la fenêtre.Finally, the enclosure 1 is provided with a circular window 14, closed in a sealed manner by a metal sheet having a section in the form of a gutter, penetrating towards the interior of the enclosure. This window is located opposite the slots 9, 11; it is transparent to electrons. The guide means, which are not shown in this figure, place the material to be irradiated around the window.

Les deux parties 7, 8 de l'électrode de Wehnelt forment deux troncs de cône qui présentent chacun une grande base et une petite base. Les grandes des bases de ces troncs de cône sont respectivement référencées 16, 7, tandis que les petites bases sont respectivement référencées 18, 19 sur la figure. Les petites bases 18, 19 des deux troncs de cône sont situées en regard l'une de l'autre et elles sont espacées de manière à constituer la première fente 9. Ces deux troncs de cône comprennent respectivement des logements 20, 21 qui sont situés en regard l'un de l'autre, au voisinage de la première fente 9. Ces logements contiennent le filament émissif 2. Dans un mode de réalisation du dispositif, la première fente 9 peut être entourée sur le pourtour des petites bases 18, 19 de chacun des deux cônes, par une grille circulaire 22.The two parts 7, 8 of the Wehnelt electrode form two truncated cones which each have a large base and a small base. The large bases of these truncated cones are respectively referenced 16, 7, while the small bases are respectively referenced 18, 19 in the figure. The small bases 18, 19 of the two truncated cones are located opposite one another and they are spaced so as to constitute the first slot 9. These two truncated cones respectively comprise housings 20, 21 which are located facing each other, in the vicinity of the first slot 9. These housings contain the emissive filament 2. In one embodiment of the device, the first slot 9 can be surrounded on the periphery of the small bases 18, 19 of each of the two cones, by a circular grid 22.

Les deux parties 7, 8 du Wehnelt sont reliées par la tige filetée 13 et par une tige 23, à la source de tension -V, à travers des éléments tels que 24, 25, d'un isolateur. Les fils de connexion 5, 6 du filament traversent un alésage 26 de la tige 23 puis l'élément 25 de l'isolateur, pour être reliés à la source de tension -V'. Il est bien évident que le vide régnant à l'intérieur de l'enceinte 1, les traversées des conducteurs 5, 6 et 27 sont étanches. De manière connue dans l'état de la technique, les éléments 24 de l'isolateur sont séparés par des rondelles conductrices 28, reliées par des résistances 29 permettant de rendre équipotentiels les différents éléments de l'isolateur. L'enceinte étanche 1 peut être fermée par un couvercle étanche 30. Ce couvercle amovible permet d'accéder à l'intérieur de l'enceinte, de manière par exemple, à remplacer le filament 2 en cas de destruction de celui-ci.The two parts 7, 8 of the Wehnelt are connected by the threaded rod 13 and by a rod 23, to the voltage source -V, through elements such as 24, 25, of an insulator. The connection wires 5, 6 of the filament pass through a bore 26 of the rod 23 then the element 25 of the insulator, to be connected to the voltage source -V '. It is obvious that the vacuum prevailing inside the enclosure 1, the crossings of the conductors 5, 6 and 27 are sealed. In a manner known in the state of the art, the elements 24 of the insulator are separated by conductive washers 28, connected by resistors 29 making it possible to make the various elements of the insulator equipotential. The sealed enclosure 1 can be closed by a sealed cover 30. This removable cover provides access to the interior of the enclosure, so as, for example, to replace the filament 2 in the event of destruction thereof.

Les figures 2 à 5 représentent différents modes de réalisation qui permettent de placer la matière à irradier sur le parcours du faisceau électronique produit dans un plan P, passant par la fenêtre 14. Sur ces figures, on a désigné par la référence C le canon à électrons. L'enceinte contenant les divers éléments du canon est représentée par la référence 1, et la fenêtre par la référence 14.FIGS. 2 to 5 represent different embodiments which make it possible to place the material to be irradiated on the path of the electron beam produced in a plane P, passing through the window 14. In these figures, the cannon has been designated by the reference C electrons. The enclosure containing the various elements of the barrel is represented by the reference 1, and the window by the reference 14.

Dans le premier mode de réalisation des moyens de guidage, représenté sur la figure 2, ces moyens comprennent une gaine annulaire creuse 31 à deux parois concentriques 31 a, 32b. La matière à irradier circule entre ces deux parois, comme indiqué par les flèches sur la figure. Cette matière peut être un liquide ou un gaz, ou même un solide en poudre. La paroi interne 31 de la gaine peut être constituée au moins partiellement par la surface externe de l'enceinte étanche 1, et par la feuille métallique qui ferme la fenêtre 14. Dans ces conditions, les matières à irradier reçoivent directement le faisceau électronique émis dans le plan P.In the first embodiment of the guide means, shown in FIG. 2, these means comprise a hollow annular sheath 31 with two concentric walls 31 a, 32b. The material to be irradiated circulates between these two walls, as indicated by the arrows in the figure. This material can be a liquid or a gas, or even a powdered solid. The internal wall 31 of the sheath can be constituted at least partially by the external surface of the sealed enclosure 1, and by the metal sheet which closes the window 14. Under these conditions, the materials to be irradiated directly receive the electron beam emitted in plan P.

Dans le deuxième mode de réalisation représenté sur la figure 3, le canon à électrons C est placé dans une trémie 33 dont la partie supérieure présente par exemple une forme évasée, favorisant la réception des matières à irradier. Ces matières sont en contact direct avec la feuille métallique qui ferme la fenêtre 14 de l'enceinte 1.In the second embodiment shown in FIG. 3, the electron gun C is placed in a hopper 33, the upper part of which, for example, has a flared shape, favoring the reception of the materials to be irradiated. These materials are in direct contact with the metal sheet which closes the window 14 of the enclosure 1.

Dans ces deux modes de réalisation des moyens de guidage, la pression à l'extérieur de l'enceinte est généralement voisine de la pression atmosphérique. Si l'on désigne par A la pression atmosphérique, par p le rayon de courbure de la fenêtre et par P la pression de la matière circulant au voisinage de la fenêtre, il est possible d'écrire P=A/p, avec A=α.ε. Dans cette dernière relation, cr désigne la limite de rupture du métal constituant la fenêtre et ε l'épaisseur de la feuille métallique fermant la fenêtre.In these two embodiments of the guide means, the pressure outside the enclosure is generally close to atmospheric pressure. If we designate by A the atmospheric pressure, by p the radius of curvature of the window and by P the pressure of the material circulating in the vicinity of the window, it is possible to write P = A / p, with A = α.ε. In this last relation, cr denotes the breaking limit of the metal constituting the window and ε the thickness of the metal sheet closing the window.

Si la pression P de la matière à irradier est de l'ordre de quelques bars, et si la fenêtre est formée d'une feuille de titane d'épaisseur 20 microns, le rayon de courbure p de cette fenêtre ne dépasse pas quelques centimètres.If the pressure P of the material to be irradiated is of the order of a few bars, and if the window is formed from a titanium sheet 20 microns thick, the radius of curvature p of this window does not exceed a few centimeters.

La figure 4 représente un troisième mode de réalisation des moyens de guidage de la matière à irradier. Dans ce mode de réalisation, ces moyens de guidage sont constitués par un ensemble 34 qui permet de déplacer la matière irradier, de manière à l'amener à circuler en regard de la fenêtre 14. Dans le cas où des objets 35 sont à irradier, ces moyens de guidage sont constitués par exemple par un tapis roulant ou une chaîne.FIG. 4 represents a third embodiment of the means for guiding the material to be irradiated. In this embodiment, these guide means consist of an assembly 34 which makes it possible to move the irradiated material, so as to cause it to circulate opposite the window 14. In the case where objects 35 are to be irradiated, these guide means are constituted for example by a conveyor belt or a chain.

Enfin, la figure 5 représente un quatrième mode de réalisation des moyens de guidage de la matière à irradier. Dans ce mode de réalisation, la matière à irradier se présente sous la forme d'une bande 36, enroulée pour former un rouleau 37 ayant la largeur du ruban. Les moyens de guidage comprennent ici un moteur 37 entraînant un axe 38 sur lequel vient s'enrouler le ruban 36 après son irradiation par le canon à électrons C. Le ruban circule dans le sens de la longueur, comme indiqué par les flèches; les moyens de guidage comprennent des guides 39, 40, 41, 42 qui permettent au ruban de former un fourreau autour de la fenêtre 14 et de l'enceinte 1, en le repliant autour de cette enceinte, dans la direction de la largeur du ruban. Le ruban est ainsi déroulé autour de l'axe 42 et enroulé autour de l'axe 38. La pièce 43 sert au maintien du dispositif.Finally, FIG. 5 represents a fourth embodiment of the means for guiding the material to be irradiated. In this embodiment, the material to be irradiated is in the form of a strip 36, wound to form a roll 37 having the width of the ribbon. The guide means here comprise a motor 37 driving an axis 38 on which the ribbon 36 is wound after being irradiated by the electron gun C. The ribbon circulates lengthwise, as indicated by the arrows; the guide means comprise guides 39, 40, 41, 42 which allow the tape to form a sheath around the window 14 and the enclosure 1, by folding it around this enclosure, in the direction of the width of the tape . The ribbon is thus unwound around the axis 42 and wound around the axis 38. The part 43 is used to hold the device.

Claims (10)

1. Apparatus for irradiating material by an electron beam incorporating an electron gun and guidance means for placing the material on the path of the beam, characterized in that the electron gun comprises, in a tight enclosure (1) having a shape with a symmetry of revolution relative to an axis (X'X), an emmissive electron filament (2) located in the axis of the enclosure (1) and coaxially a Wehnelt electrode (7, 8) surrounding the filament (2) and having a symmetry of revolution with respect to said axis (X'X) and having a first circular slot (9) for concentrating electrons in the vicinity of the plane (P) perpendicular to the axis and passing through the first slot (9) positioned facing the filament (2), at least one electron accelerating electrode (10) surrounding the Wehnelt electrode (7, 8) and having a symmetry of revolution relative to said axis and having a second circular slot (11) facing the first slot (9), the enclosure (1) having a circular window (14), which is tightly closed and transparent to electrons, said window facing the two slots (9, 11), the guidance means placing the material to be irradiated around the window (14).
2. Apparatus according to claim 1, characterized in that the Wehnelt electrode comprises two truncated cones (7, 8), each having a circular large base and a circular small base perpendicular to the axis (X'X), the respective small bases (18, 19) of the two truncated cones facing one another and being spaced to form the first slot (9), the truncated cones (7, 8) having recesses (20, 21) facing and in the vicinity of the first slot (9) and containing said filament (2).
3. Apparatus according to claim 2, characterized in that the said window (14) is closed by a metal sheet (15) having a trough-like section and penetrating towards the interior of the enclosure (1).
4. Apparatus according to claim 2, characterized in that the first slot (9) is surrounded by a circular grid (22) on the circumference of the small bases (18, 19) of each of the two cones (7, 8).
5. Apparatus according to any one of the claims 1 to 4, characterized in that the guidance means in- corporte an annular hollow sheath (31) with two concentric walls (32a, 32b) surrounding said window
(14), the material to be irradiated circulating in said sheath.
6. Apparatus according to claim 5, characterized in that one of the sheath walls is partly constituted by the outer surface of the tight enclosure (1) and by the sheet (15) closing the window.
7. Apparatus according to any one of the claims 1 to 4, characterized in that the guidance means incorporate a funnel (33) surrounding the gun (C) and in which the material to be irradiated circulates.
8. Apparatus according to one of the claims 1 to 4, characterized in that the guidance means incorporate a system (34) for displacing the material to be irradiated, so as to make it circulate in front of the window (14).
9. Apparatus according to any one of the claims 1 to 4, characterized in that the material to be irradiated is in the form of a belt or tape (36) wound to form a reel having the width of said belt or tape, the guidance means (39, 40, 41, 42) incorporating means for unwinding the tape by making it circulate in the direction of its length and so that it forms a sleeve round the window (14), by folding it in the direction of its width.
EP85402371A 1984-12-14 1985-12-02 Device for the irradiation of matter by an electron beam Expired EP0186558B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8419153A FR2574978B1 (en) 1984-12-14 1984-12-14 DEVICE FOR IRRADIATION OF MATERIAL BY AN ELECTRONIC BEAM
FR8419153 1984-12-14

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EP0186558A1 EP0186558A1 (en) 1986-07-02
EP0186558B1 true EP0186558B1 (en) 1989-05-10

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EP (1) EP0186558B1 (en)
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EP0186558A1 (en) 1986-07-02
FR2574978A1 (en) 1986-06-20
DE3570153D1 (en) 1989-06-15
FR2574978B1 (en) 1987-01-16
CA1236225A (en) 1988-05-03
US4663532A (en) 1987-05-05

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