EP0013235B1 - Electron multiplying apparatus with axial magnetic field - Google Patents

Electron multiplying apparatus with axial magnetic field Download PDF

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Publication number
EP0013235B1
EP0013235B1 EP79401057A EP79401057A EP0013235B1 EP 0013235 B1 EP0013235 B1 EP 0013235B1 EP 79401057 A EP79401057 A EP 79401057A EP 79401057 A EP79401057 A EP 79401057A EP 0013235 B1 EP0013235 B1 EP 0013235B1
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EP
European Patent Office
Prior art keywords
dynode
electron
fact
principal axis
electron multiplier
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EP79401057A
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German (de)
French (fr)
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EP0013235A1 (en
Inventor
Kei-Ichi Kuroda
Daniel Sillou
Fujio Takeuchi
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Bpifrance Financement SA
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Agence National de Valorisation de la Recherche ANVAR
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Priority to AT79401057T priority Critical patent/ATE6711T1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/18—Electrode arrangements using essentially more than one dynode
    • H01J43/22—Dynodes consisting of electron-permeable material, e.g. foil, grid, tube, venetian blind
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/06—Electrode arrangements
    • H01J43/14—Control of electron beam by magnetic field

Definitions

  • the present invention relates to electron multipliers, and more particularly to photomultiplier tubes.
  • electron multiplier devices conventionally comprise, in a tubular vacuum enclosure, first one or more electrodes forming a cathode and directed source of electrons, then a series of electrodes capable of secondary emission of electrons, or dynodes, and finally an anode forming an electron collector. These different electrodes are arranged along the main axis of the tube; in operation, they are brought to potentials capable of creating an electric field accelerating the electrons along this same axis.
  • the electron source made of photosensitive material, is called photocathode.
  • dynodes In a type of electron multiplier ("box-type"), the dynodes each comprise a single element, and the dynodes together define a sort of box channeling the electrons, each dynode facing partly the previous one and partly to the next one.
  • box-type type of electron multiplier
  • each dynode is of distributed structure comprising several active elements (ensuring secondary emission), which extend transversely to the main axis of the tube.
  • each dynode is made up of rectangular strips parallel to each other, the long side of which extends perpendicular to the main axis of the tube, while their short side is inclined on this same axis.
  • such dynodes are said to be “Venetian”, or of the "Persian” type.
  • two consecutive dynodes have an alternating and symmetrical inclination relative to the main axis of the tube.
  • U.S. Patent 2,305,179 describes an electron multiplier apparatus, comprising a vacuum tube which contains multiple stages of distributed structure dynodes capable of secondary reflex electronic emission when struck by charged particles and electron receiving means, means producing an electron accelerating electric field directed substantially along a main axis which passes through the stages of dynodes and going towards the electron receiving means, and means producing a directed magnetic field substantially along the main axis.
  • dynode with a distributed structure capable of secondary reflex electronic emission
  • each dynode consists of a thin grid; the image intensifier described comprises four grids of this kind, and satisfies certain focusing conditions. allowing the device to work despite the presence of a magnetic field. Indeed, magnetic fields are generally considered to be harmful to the proper functioning of high gain electron multipliers.
  • the object of the present invention is to provide an improved electron multiplier, where, in the presence of a magnetic field, a high gain is retained, with improved properties in terms of the rise time (better temporal resolution) and linearity of the output signal.
  • the paths of the secondary electrons form a node at the height of the second level of dynode elements.
  • the dynode stages comprise grids of parallel bars, each grid being substantially perpendicular to the main axis.
  • the small dimension of the bars in the plane perpendicular to the main axis is less than about 1 mm, and the distance between two adjacent bars is at least equal to their small dimension. This jointly improves the spatial resolution and the gain. It is then desirable, although not absolutely necessary, for the electric field to be greater than 200 V / cm, and for the magnetic field to be greater than 0.005 Tesla. In the preferred embodiments of the invention, the small size of the bars is 0.5 mm approximately and the electric field and the magnetic field are chosen correlatively with one another between approximately 400 and 1000 V / cm, and between approximately 0.01 and 0.05 Tesla, respectively.
  • each dynode comprises two grids of bars spaced along the main axis; in each grid the bars are spaced a distance equal to their small dimension; the two grids are offset from each other by a distance equal to their small dimension; and the electric and magnetic fields are correlatively chosen so that a secondary electron emitted by a bar of the first grid always passes statistically between the bars of the second grid (the word statistically means here that a secondary electron nevertheless retains a certain probability - very weak - to reach the bars of the second grid).
  • each dynode comprises n grids of bars spaced along the main axis; in each grid the bars are spaced n times their small dimension; the n grids are successively offset in the same direction by a distance equal to their small dimension each with respect to the previous one; and the electric and magnetic fields are correlatively chosen so that a secondary electron emitted by a bar of a grid on a parallel to the main axis passes statistically on the same parallel substantially at the levels of the following grid and the n-th wire rack.
  • the bars it is also advantageous for the bars to have a cross section symmetrical with respect to a plane parallel to the main axis of the tube and passing through the axis of their largest dimension. This provides better homogeneity of the electric field, and improves spatial resolution.
  • the cross section of the bars is of the isosceles right triangle triangle of hypotenuse directed downstream of the electronic trajectories, of the circylar kind, or of the flat rectangle kind of predetermined inclination on the main axis, the bars then being slats.
  • other types of cross section can be envisaged.
  • the main application studied was that of photo-multipliers, but the invention generally applies to any type of electron multiplier tube whose dynodes, with distributed structure, are capable of secondary reflex emission.
  • the electron emitting and receiving surfaces which surround these dynodes can take different forms.
  • the electron-emitting surface can be an electron-emitting electrode, cathode or photocathode, or a surface transparent to electrons of external origin.
  • the electron receiving surface can be a divided anode with multiple connections, an electroluminescent surface or a mosaic surface which can be analyzed by electron beam, as will be seen below.
  • FIG. 1 is a schematic sectional view of a conventional photomultiplier tube with Venetian dynodes.
  • a photocathode 2 is arranged to receive a light beam L.
  • this cathode reacts to each photon by emitting a primary electron, channeled by an electrode 3.
  • the primary electrons are directed towards a series of 10 dynodes, referenced 4 to 13, and followed by an anode 14.
  • the electrodes are brought to potentials capable of creating an electric field, accelerating the electrons from the cathode towards the anode, that is to say in the direction of the axis of the tube.
  • Each dynode, of distributed structure comprises a plurality of parallel lamellae and inclined which extend perpendicular to the plane of Figure 1, and extend vertically in the plane of Figure 1.
  • the slats are rectangular, 30 mm long and 3 mm wide; their short side is inclined at 45 ° to the main axis of the tube, the direction of inclination being alternated from one dynode to another.
  • the surface of the dynodes is made of material capable of secondary electronic emission, that is to say that, struck by an electron, each dynode will emit several secondary electrons on the side where the primary electron arrived. And the secondary electrons are in turn accelerated and led by the electric field to the next dynode.
  • Figure 2 very schematically illustrates this process, and shows how, for a photon arriving at A on the photo-cathode, the anode receives electrons on a rather large surface denoted D.
  • a dark enclosure 30 has an internal partition 31 x 10 supporting a converging lens 32. and on the other side thereof are housed in the enclosure a photodiode 35 (point source of 0.5 mm) and a photomultiplier tube 36.
  • the photodiode is movable in a plane which is the conjugate with respect to the lens of the plane of the photocathode 37 of the tube 36.
  • the tube comprises several stages of dynodes 34 and an anode 33.
  • the tube 36 is for example the EMI 6262 model, conventionally polarized with a high voltage of 1500 Volts.
  • a coil 39 produces a magnetic field oriented along the main axis 38 of the tube, for example downwards (the direction of the magnetic field has proven to be of little importance so far).
  • FIG. 4 illustrates on the ordinate the output signal of the tube on a logarithmic scale, as a function of the magnetic field applied, plotted linearly on the abscissa.
  • the photodiode was placed in two positions corresponding to the two edges of one of the strips constituting the dynodes.
  • the points marked »+ « and » 0 correspond respectively to the lower and upper edges of the coverslip.
  • the gain is G o ;
  • the gain decreases, and the two points »+ « and »O « separate more and more.
  • the inventors estimated that the value of 0.003 Tesla corresponds to a radius of curvature of the electronic trajectories in the magnetic field of the order of magnitude of the width of the lamellae (3 mm).
  • the B field exceeds 0.003 Tesla, the radius of curvature of the trajectory of a secondary electron emitted by a dynode is small, and the electron is likely to be recaptured by the coverslip, hence the rapid decrease in gain with the magnetic field.
  • the B field is less than 0.003 Tesla, the electron has the greatest chance of gaining the next dynode, hence the substantially constant gain.
  • FIG. 5 illustrates, for a magnetic field of 0.012 Tesla, the output signal of the tube plotted on the ordinate and on a logarithmic scale, as a function of the position of the light point on the cathode, plotted linearly on the abscissa.
  • This figure shows that the gain varies as a function of the position of the light source, and that the shape of the gain reflects the lamellar structure of the dynodes.
  • the inventors have also observed a channeling of the electronic trajectories autor of the axis of the field B. If we return to FIG. 3, the domain D becomes all the smaller as the field B is higher. Again, this is due to the radius of curvature imposed on the electronic trajectories by the magnetic field. This results in the possibility of locating at the level of the anode the origin A of the primary electron, by using for example a fractional or multi-anode anode.
  • the localization effect of the magnetic field is acquired using the electron multiplier tube arranged according to FIG. 3, which retains real multiplying properties, despite a gain much less than the value G o at null field. However, the tube is then unusable in practice, because of its very low gain.
  • the simulation took into account the geometrical configuration of the tube, the value of the potentials between electrodes, the experimental data on the secondary emission of the dynodes, as well as the accessory effects. such as edge loss and space charge.
  • each dynode here comprises two levels.
  • the dynode D n - 1 comprises the levels 61 and 62.
  • the level 61 comprises a series of strips or rather of elongated bars whose section is an isosceles right triangle with a basic 0.5 mm.
  • the base is perpendicular to the main axis of the tube, and exposed to the next dynode.
  • the free space between the vertices of the bases of two adjacent bars is also 0.5 mm.
  • the second level 62 placed 2.5 mm from the first, is constituted in the same way, but its bars are aligned on the free spaces between those of the previous floor, so that seen from above the whole of the dynode constitutes a structure without free space.
  • the second dynode D n is similar to the first, its first level 63 being offset by 10 mm from level 61.
  • the surfaces active on the plane of the secondary electronic emission are at each level the two surfaces inclined at 45 °, defined by the sides of the right angle of the isosceles right triangle.
  • a voltage of 150 volts is established between the levels 61 and 62, a voltage of 600 volts between the stages 61 and 63, and again a voltage of 150 volts between the stages 63 and 64, the polarization being thus repeated periodically for the set of dynodes.
  • FIG. 7 Another structure, mechanically more complex, is illustrated in FIG. 7.
  • the concept of separate dynodes is diluted in this structure, because the set of dynodes consists of a large number of equidistant levels, such as 71 to 76 which represent them. a part.
  • Each level includes bars identical to those in Figure 6, but separated by a free space of 2.0 mm.
  • the bars of a given level are 0.5 mm apart from those of the previous level, to the left for example.
  • the second level 76 bar is located vertically from the first level 71 bar, from the left.
  • the set of levels 71 to 75 forms an opaque system for an electron beam parallel to the z axis.
  • a dynode stage corresponds to 5 consecutive grids or levels, such as 71 to 75.
  • the pitch between stages is 12.5 mm.
  • a magnetic field of 0.041 Tesla and an increasing potential of 400 Volts per stage, (i.e. an electric field of approximately 400 Volts / cm) such an electron multiplier is likely to reach a spatial resolution (at mid-height of the impact distribution on the anode) of ⁇ 1.5 mm, for a gain of the order of 10 7 .
  • the inventors have observed that the structures of dynodes whose bars have a section symmetrical with respect to the z axis are advantageous, as providing a better homogeneity of the electric field, and thereby a better spatial resolution.
  • FIG. 8 Another structure of dynodes is illustrated in FIG. 8. Like that of FIG. 7, it has levels 81 to 86 of active elements regularly distributed along the axis Oz, and offset successively by a value equal to the small dimension. of these active elements, projected onto the x axis (0.5 mm); here again, the free space between two active elements is 2.0 mm, so that the active elements of level 86 are vertical to those of level 81. But, this time, instead of the bars with triangular section , the active elements are Venetian lamellae, inclined at 45 ° all on the same side, and of which only the face facing upwards is capable of secondary emission. A stage is again made up of 5 adjacent levels of lamellas, and the pitch between stages is 5 mm.
  • the secondary electrons thus produced must pass between the bars of the grid 62 to reach one or the other of the grids 63 and 64, and so on, taking into account the dimensions of the structure geometry. We will then say that the trajectories of the electrons coming from the grid 61 form a knot between the bars of the grid 62.
  • the two nodes are substantially aligned with emission point in the z direction, and the electrons then have the greatest chance of touching the grid 76 or another of the consecutive grids forming the next stage, avoiding the grids 72 to 75.
  • the trajectories are more complex, due to the poorer homogeneity of the electric field, due to the asymmetry of the lamellae with respect to the z axis.
  • the spatial resolution can be all the better as the active elements of the grids are made finer, the electric and magnetic fields then being increased accordingly.
  • the electron multipliers according to the invention have better temporal resolution, than the photo-multipliers of the louver type, their rise time being able to drop to less than 2 nanoseconds (10 to 90% of the current peak ) against about 10 nanoseconds for most conventional Venetian dynode photomultipliers.
  • the invention essentially provides an electron multiplier tube capable of localization, that is to say in which there is a fine correspondence between the points of departure of the electrons on the entry surface of the tube and the points of arrival. electrons on the exit surface of the tube.
  • the finesse of this correspondence is defined by the spatial resolution.
  • the currently preferred application is that of photomultipliers, the input surface then being a photocathode.
  • the invention can however be applied with all kinds of cathodes selectively emitting electrons on their surface (divided cathode for example). It is also possible to inject electrons produced by another source through the entry surface of the tube (electron accelerator for example).
  • the term "electron emitting surface” here covers all of these situations.
  • the exit surface of the tube, or “electron receiving surface” should of course allow selective detection of the electrons according to their point of arrival.
  • the resolution is independent of the statistical fluctuation due to the quantum yield of the photoca thode, since the photoelectron source is common for all adjacent anode fragments.
  • the resolution is therefore practically independent of the light intensity of the source analyzed.
  • the electroluminescent screen analogous to cathode ray tube screens, which allows visual and / or photographic examination.
  • the electron receiving surface can also be produced as in television picture tubes, and include a mosaic of small elements which are charged under the effect of the received electrons, while a beam of analyzer electrons comes to sweep this surface to read the charge of each element of the mosaic. A sequential signal is thus obtained which, linked to the scanning, defines the spatial distribution of the electrons received. Due to the sequential scanning, this type of receiving surface does not make it possible to fully benefit from the temporal resolution of the tube according to the invention.
  • a photomultiplier according to the invention with a diameter of 100 mm could replace 50 to 100 small conventional photomultipliers with Venetian dynodes by offering excellent spatial resolution ( ⁇ 1.5 mm), a gain that is practically as good, more homogeneous and more linear, and higher time resolution.
  • each dynode stage is made up of several levels, offset between them so as to constitute together a practically opaque structure for the incident electrons.

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Abstract

Electron multiplier tube, comprising along the principal axis an electron-emitting surface, several dynode stages with distributed structure, capable of reflux secondary electron emission, and an electron-receiving surface, as well as means producing an electron-accelerating electric field generally oriented along the principal axis, from the electron-emitting surface to the electron-receiving surface. With it is associated coil means producing a magnetic field generally oriented along the principal axis of the tube. Particular example is a photomultiplier with high spatial resolution.

Description

La présente invention concerne les multiplicateurs d'électrons, et plus particulièrement les tubes photomultiplicateurs.The present invention relates to electron multipliers, and more particularly to photomultiplier tubes.

On sait que les appareils multiplicateurs d'électrons comportent classiquement, dans une enceinte tubulaire sous vide, d'abord une ou plusieurs électrodes formant cathode et source dirigée d'électrons, puis une série d'électrodes capables d'émission secondaire d'électrons, ou dynodes, et enfin une anode formant collecteur d'électrons. Ces différentes électrodes sont disposées le long de l'axe principal du tube; en fonctionnement, elles sont portées à des potentiels propres à créer un champ électrique accélérant les électrons le long de ce même axe. Pour les photomultiplicateurs, la source d'électrons, en matériau photosensible, est dénommée photocathode.It is known that electron multiplier devices conventionally comprise, in a tubular vacuum enclosure, first one or more electrodes forming a cathode and directed source of electrons, then a series of electrodes capable of secondary emission of electrons, or dynodes, and finally an anode forming an electron collector. These different electrodes are arranged along the main axis of the tube; in operation, they are brought to potentials capable of creating an electric field accelerating the electrons along this same axis. For photomultipliers, the electron source, made of photosensitive material, is called photocathode.

On connaît plusieurs structures de dynodes. Dans un type de multiplicateurs d'électrons (»box-type«), les dynodes comprennent chacune un seul élément, et les dynodes définissent ensemble une sorte de boîte canalisant les électrons, chaque dynode faisant face pour partie à la précédente et pour partie à la suivante.Several structures of dynodes are known. In a type of electron multiplier ("box-type"), the dynodes each comprise a single element, and the dynodes together define a sort of box channeling the electrons, each dynode facing partly the previous one and partly to the next one.

Dans d'autres multiplicateurs d'électrons (brevet US 2 249 016), chaque dynode est à structure distribuée comprenant plusieurs éléments actifs (assurant l'émission secondaire), qui s'étendent transversalement à l'axe principal du tube. Par exemple, chaque dynode est constituée de lamelles rectangulaires parallèles entre elles dont le grand côté s'étend perpendiculairement à l'axe principal du tube, tandis que leur petit côté est incliné sur ce même axe. Par analogie, de telles dynodes sont dites »vénitiennes«, ou encore du type »persienne«. Souvent, deux dynodes consécutives présentent une inclinaison alternée et symétrique par rapport à l'axe principal du tube.In other electron multipliers (US Pat. No. 2,249,016), each dynode is of distributed structure comprising several active elements (ensuring secondary emission), which extend transversely to the main axis of the tube. For example, each dynode is made up of rectangular strips parallel to each other, the long side of which extends perpendicular to the main axis of the tube, while their short side is inclined on this same axis. By analogy, such dynodes are said to be "Venetian", or of the "Persian" type. Often, two consecutive dynodes have an alternating and symmetrical inclination relative to the main axis of the tube.

Le brevet des Etats-Unis 2 305 179 décrit un appareil multiplicateur d'électrons, comprenant un tube à vide qui contient plusieurs étages de dynodes à structure distribuée, capables d'émission électronique secondaire réflexe lorsqu'elles sont frappées par des particules chargées et des moyens récepteurs d'électrons, des moyens produisant un champ électrique accélérateur d'électrons dirigé sensiblement le long d'un axe principal qui passe par les étages de dynodes et va vers les moyens récepteurs d'électrons, et des moyens produisant un champ magnétique dirigé sensiblement le long de l'axe principal.U.S. Patent 2,305,179 describes an electron multiplier apparatus, comprising a vacuum tube which contains multiple stages of distributed structure dynodes capable of secondary reflex electronic emission when struck by charged particles and electron receiving means, means producing an electron accelerating electric field directed substantially along a main axis which passes through the stages of dynodes and going towards the electron receiving means, and means producing a directed magnetic field substantially along the main axis.

Par dynode à structure distribuée, capable d'émission électronique secondaire réflexe, on entend une dynode dont la surface capable d'émission secondaire est discontinue, et disposée pour renvoyer les électrons secondaires du côté où est arrivé l'électron primaire. Dans le brevet US cité, chaque dynode est constituée d'une grille mince; l'intensificateur d'image décrit comporte quatre grilles de ce genre, et satisfait certaines conditions de focaiisatiot. permettant le travail de l'appareil malgré la présence d'un champ magnétique. En effet, les champs magnétiques sont génétalement considérés comme néfastes au bon fonctionnement des multiplicateurs d'électrons à fort gain.By dynode with a distributed structure, capable of secondary reflex electronic emission, is meant a dynode whose surface capable of secondary emission is discontinuous, and arranged to return the secondary electrons to the side where the primary electron arrived. In the cited US patent, each dynode consists of a thin grid; the image intensifier described comprises four grids of this kind, and satisfies certain focusing conditions. allowing the device to work despite the presence of a magnetic field. Indeed, magnetic fields are generally considered to be harmful to the proper functioning of high gain electron multipliers.

Dans ces conditions, la présente invention a pour but de fournir un multiplicateur d'électrons perfectionné, où en présence d'un champ magnétique, on conserve un fort gain, assorti de propriétés améliorées au niveau du temps de montée (résolution temporelle meilleure) et de la linéarité du signal de sortie.Under these conditions, the object of the present invention is to provide an improved electron multiplier, where, in the presence of a magnetic field, a high gain is retained, with improved properties in terms of the rise time (better temporal resolution) and linearity of the output signal.

Selon l'invention:

  • a) chaque étage de dynode comprend au moins deux niveaux d'éléments de dynode distribués,
  • b) ces niveaux d'éléments de dynode sont espacés le long de l'axe principal et sont décalés entre eux dans chaque étage de dynode de façon à définir une surface sensiblement étanche pour un mouvement électronique sensiblement rectiligne parallèlement à l'axe principal,
  • c) les éléments de dynode de chaque niveau possèdent, dans le sens transversal à l'axe principal, une dimension choisie en relation avec le champ magnétique de sorte que le rayon de courbure moyen des projections orthogonales des trajectoires des électrons secondaires sur un plan perpendiculaire à l'axe du tube soit au moins égal à la dimension transversale des éléments de dynode, et
  • d) les niveaux d'éléments de dynode sont ainsi espacés que pratiquement aucun électron secondaire émis par le premier niveau d'éléments de dynode d'un étage de dynode ne frappe le second niveau d'éléments de dynode du même étage, tandis que pratiquement tous ces électrons secondaires frappent un niveau d'éléments de dynode de l'étage de dynode suivant.
According to the invention:
  • a) each dynode stage comprises at least two levels of distributed dynode elements,
  • b) these levels of dynode elements are spaced along the main axis and are offset from each other in each dynode stage so as to define a substantially sealed surface for a substantially rectilinear electronic movement parallel to the main axis,
  • c) the dynode elements of each level have, in the direction transverse to the main axis, a dimension chosen in relation to the magnetic field so that the mean radius of curvature of the orthogonal projections of the trajectories of the secondary electrons on a perpendicular plane the axis of the tube is at least equal to the transverse dimension of the dynode elements, and
  • d) the levels of dynode elements are spaced so that practically no secondary electron emitted by the first level of dynode elements of a dynode stage hits the second level of dynode elements of the same stage, while practically all of these secondary electrons strike a level of dynode elements in the next dynode stage.

De préférence, les trajets des électrons secondaires forment un noeud à hauteur du second niveau d'éléments de dynode.Preferably, the paths of the secondary electrons form a node at the height of the second level of dynode elements.

Avantageusement, les étages de dynode comprennent des grilles de barreaux parallèles, chaque grille étant sensiblement perpendiculaire à l'axe principal.Advantageously, the dynode stages comprise grids of parallel bars, each grid being substantially perpendicular to the main axis.

Ces caractéristiques sont apparues à la suite de recherches menées sur un photomultiplicateur à fort gain du type à dynodes vénitiennes. Comme on le verra plus loin, ces recherches ont montré que la résolution spatiale, les caractéristiques de gain, et la résolution temporelle s'améliorent lorsqu'on diminue la taille des éléments actifs sur le plan de l'émission secondaire qui constituent les dynodes, tout en augmentant les champs électrique et magnétique.These characteristics appeared as a result of research carried out on a high gain photomultiplier of the Venetian dynode type. As will be seen below, this research has shown that the spatial resolution, the gain characteristics, and the temporal resolution improve when the size of the active elements on the plane of the secondary emission which constitute the dynodes, while increasing the electric and magnetic fields.

De préférence, la petite dimension des barreaux dans le plan perpendiculaire à l'axe principal, est inférieure à 1 mm environ, et l'écart entre deux barreaux adjacents est au moins égal à leur petite dimension. Ceci améliore conjointement la résolution spatiale et le gain. Il est alors souhaitable, quoique non absolument nécessaire, que le champ électrique soit supérieur à 200 V/cm, et que le champ magnétique soit supérieur à 0,005 Tesla Dans les réalisations préférentielles de l'invention, la petite dimension des barreaux est 0,5 mm environ et le champ électrique et le champ magnétique sont choisis corrélativement l'un à l'autre entre 400 et 1000 V/cm environ, et entre 0,01 et 0,05 Tesla environ, respectivement.Preferably, the small dimension of the bars in the plane perpendicular to the main axis is less than about 1 mm, and the distance between two adjacent bars is at least equal to their small dimension. This jointly improves the spatial resolution and the gain. It is then desirable, although not absolutely necessary, for the electric field to be greater than 200 V / cm, and for the magnetic field to be greater than 0.005 Tesla. In the preferred embodiments of the invention, the small size of the bars is 0.5 mm approximately and the electric field and the magnetic field are chosen correlatively with one another between approximately 400 and 1000 V / cm, and between approximately 0.01 and 0.05 Tesla, respectively.

Dans un premier mode de réalisation particulier, chaque dynode comprend deux grilles de barreaux espacées le long de l'axe principal; dans chaque grille les barreaux sont espacés d'une distance égale à leur petite dimension; les deux grilles sont décalées l'une par rapport à l'autre d'une distance égale à leur petite dimension; et les champs électrique et magnétique sont corrélativement choisis pour qu'un électron secondaire émis par un barreau de la première grille passe statistiquement toujours entre les barreaux de la seconde grille (le mot statistiquement signifie ici qu'un électron secondaire conserve néanmoins une certaine probabilité - très faible - d'atteindre les barreaux de la seconde grille).In a first particular embodiment, each dynode comprises two grids of bars spaced along the main axis; in each grid the bars are spaced a distance equal to their small dimension; the two grids are offset from each other by a distance equal to their small dimension; and the electric and magnetic fields are correlatively chosen so that a secondary electron emitted by a bar of the first grid always passes statistically between the bars of the second grid (the word statistically means here that a secondary electron nevertheless retains a certain probability - very weak - to reach the bars of the second grid).

Dans un autre de réalisation particulier, chaque dynode comprend n grilles de barreaux espacées le long de l'axe principal; dans chaque grille les barreaux sont espacés de n fois leur petite dimension; les n grilles sont successivement décalées dans le même sens d'une distance égale à leur petite dimension chacune par rapport à la précédente; et les champs électrique et magnétique sont corrélativement choisis pour qu'un électron secondaire émis par un barreau d'une grille sur une parallèle à l'axe principal repasse statistiquement sur la même parallèle sensiblement aux niveaux de la grille suivante et de la n-ième grille.In another particular embodiment, each dynode comprises n grids of bars spaced along the main axis; in each grid the bars are spaced n times their small dimension; the n grids are successively offset in the same direction by a distance equal to their small dimension each with respect to the previous one; and the electric and magnetic fields are correlatively chosen so that a secondary electron emitted by a bar of a grid on a parallel to the main axis passes statistically on the same parallel substantially at the levels of the following grid and the n-th wire rack.

Cette seconde structure fonctionne bien pour n=5.This second structure works well for n = 5.

Il est également avantageux que les barreaux aient une section droite symétrique par rapport à un plan parallèle à l'axe principal du tube et passant par l'axe de leur plus grande dimension. Ceci procure une meilleure homogénéité du champ électrique, et améliore la résolution spatiale.It is also advantageous for the bars to have a cross section symmetrical with respect to a plane parallel to the main axis of the tube and passing through the axis of their largest dimension. This provides better homogeneity of the electric field, and improves spatial resolution.

En pratique, la section droite des barreaux est du genre triangle rectangle isocèle d'hypoténuse dirigée vers l'aval des trajectoires électroniques, du genre circylaire, ou du genre rectangle plat d'inclinaison prédéterminée sur l'axe principal, les barreaux étant alors des lamelles. Mais d'autres types de section droite peuvent être envisagés.In practice, the cross section of the bars is of the isosceles right triangle triangle of hypotenuse directed downstream of the electronic trajectories, of the circylar kind, or of the flat rectangle kind of predetermined inclination on the main axis, the bars then being slats. However, other types of cross section can be envisaged.

L'application principale étudiée a été celle des photo-multiplicateurs, mais l'invention s'applique généralement à tout type de tube multiplicateur d'électrons dont les dynodes, à structure distribuée, sont capables d'émission secondaire réflexe. Les surfaces émettrice et réceptrice d'électrons qui encadrent ces dynodes peuvent prendre différentes formes.The main application studied was that of photo-multipliers, but the invention generally applies to any type of electron multiplier tube whose dynodes, with distributed structure, are capable of secondary reflex emission. The electron emitting and receiving surfaces which surround these dynodes can take different forms.

Ainsi, la surface émettrice d'électrons peut être une électrode émissive d'électrons, cathode ou photocathode, ou une surface transparente à des électrons d'origine externe. De son côté, la surface réceptrice d'électrons peut être une anode divisée à connexions multiples, une surface électroluminescente ou une surface mosaïque analysable par faiseau d'électrons, comme on le verra plus loin.Thus, the electron-emitting surface can be an electron-emitting electrode, cathode or photocathode, or a surface transparent to electrons of external origin. For its part, the electron receiving surface can be a divided anode with multiple connections, an electroluminescent surface or a mosaic surface which can be analyzed by electron beam, as will be seen below.

D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture de la description détaillée qui va suivre, faite en référence, aux dessins annexés, sur lesquels:

  • - la figure 1 est une coupe simplifiée d'un photomultiplicateur classique à dynodes vénitiennes,
  • - la figure 2 est une coupe très schématique illustrant les trajectoires électroniques dans un photomultiplicateur classique,
  • - la figure 3 est une vue en coupe d'un dispositif expérimental incluant un tube photomultiplicateur soumis à un champ magnétique axial,
  • - les figures 4 et 5 sont des diagrammes relatifs au dispositif expérimental de la figure 3, et
  • - les figures 6 à 8 sont des schémas en perspective cavalière illustrant différentes géométries de dynodes utilisables selon la présente invention.
Other characteristics and advantages of the invention will appear on reading the detailed description which follows, given with reference to the appended drawings, in which:
  • FIG. 1 is a simplified section of a conventional photomultiplier with Venetian dynodes,
  • FIG. 2 is a very schematic section illustrating the electronic trajectories in a conventional photomultiplier,
  • FIG. 3 is a sectional view of an experimental device including a photomultiplier tube subjected to an axial magnetic field,
  • FIGS. 4 and 5 are diagrams relating to the experimental device of FIG. 3, and
  • - Figures 6 to 8 are diagrams in perspective showing different geometries of dynodes used according to the present invention.

Bien que le dispositif expérimental qu1 sera décrit ci-après intéresse un photomultiplicateur, ses caractéristiques sont applicables à tout type de tube multiplicateur d'électrons, le comportement de ceux-ci étant sensiblement le même quelle que soit leur origine.Although the experimental device which will be described below concerns a photomultiplier, its characteristics are applicable to any type of electron multiplier tube, the behavior of these being substantially the same whatever their origin.

La figure 1 est une vue schématique en coupe d'un tube photomultiplicateur classique à dynodes vénitiennes. Dans une ampoule de verre sous vide 1, une photocathode 2 est disposée pour recevoir un faisceau lumineux L. En matériau photoélectrique, cette cathode réagit à chaque photon en émettant un électron primaire, canalisé par une électrode 3. Les électrons primaires se dirigent vers une série de 10 dynodes, référencées 4 à 13, et suivies d'une anode 14. Les électrodes sont portées à des potentiels propres à créer un champ électrique, accélérant les électrons de la cathode vers l'anode, c'est-à-dire dans la direction de l'axe du tube.Figure 1 is a schematic sectional view of a conventional photomultiplier tube with Venetian dynodes. In a vacuum glass bulb 1, a photocathode 2 is arranged to receive a light beam L. Made of photoelectric material, this cathode reacts to each photon by emitting a primary electron, channeled by an electrode 3. The primary electrons are directed towards a series of 10 dynodes, referenced 4 to 13, and followed by an anode 14. The electrodes are brought to potentials capable of creating an electric field, accelerating the electrons from the cathode towards the anode, that is to say in the direction of the axis of the tube.

Chaque dynode, de structure distribuée, comporte une pluralité de lamelles parallèles et inclinées qui s'étendent perpendiculairement au plan de la figure 1, et s'échelonnent verticalement dans le plan de la figure 1. Par exemple, dans un mode de réalisation, les lamelles sont rectangulaires, de longueur 30 mm et de largeur 3 mm; leur petit côté est incliné à 45° sur l'axe principal du tube, le sens d'inclinaison étant alterné d'une dynode à l'autre.Each dynode, of distributed structure, comprises a plurality of parallel lamellae and inclined which extend perpendicular to the plane of Figure 1, and extend vertically in the plane of Figure 1. For example, in one embodiment, the slats are rectangular, 30 mm long and 3 mm wide; their short side is inclined at 45 ° to the main axis of the tube, the direction of inclination being alternated from one dynode to another.

La surface des dynodes est réalisée en matériau capable d'émission électronique secondaire, c'est-à-dire que, frappée par un électron, chaque dynode va émettre plusieurs électrons secondaires du côté où est arrivé l'électron primaire. Et les électrons secondaires sont à leur tour accélérés et conduits par le champ électrique vers la dynode suivante.The surface of the dynodes is made of material capable of secondary electronic emission, that is to say that, struck by an electron, each dynode will emit several secondary electrons on the side where the primary electron arrived. And the secondary electrons are in turn accelerated and led by the electric field to the next dynode.

La figure 2 illustre très schématiquement ce processus, et montre comment, pour un photon arrivant en A sur la photo-cathode, l'anode reçoit des électrons sur une assez large surface notée D.Figure 2 very schematically illustrates this process, and shows how, for a photon arriving at A on the photo-cathode, the anode receives electrons on a rather large surface denoted D.

Jusqu'à présent, les champs magnétiques étaient considérés comme très néfastes aux qualités essentielles d'un tube photomultiplicateur, qui sont le gain (facteur multiplicateur d'électrons), avec sa linéarité et son homogénéité, ainsi que la résolution temporelle, c'est-à-dire l'intervalle de temps minimum requis entre deux électrons primaires pour que l'anode du tube offre des signaux distincts. En particulier, les tubes sont très souvent protégés soigneusement des champs magnétiques à l'aide d'un blindage en mu-métal.Until now, magnetic fields were considered to be very harmful to the essential qualities of a photomultiplier tube, which are the gain (electron multiplier factor), with its linearity and its homogeneity, as well as the temporal resolution, it is ie the minimum time interval required between two primary electrons for the anode of the tube to offer distinct signals. In particular, the tubes are very often carefully protected from magnetic fields using mu-metal shielding.

Les inventeurs ont néanmoins eu l'idée d'étudier plus précisément les effets des champs magnétiques, à l'aide du dispositif expérimental de la figure 3. Une enceinte obscure 30 comporte une cloison interne 31 x 10 supportant une lentille convergente 32. De part et d'autre de celle-ci sont logées dans l'enceinte une photodiode 35 (source ponctuelle de 0,5 mm) et un tube photomultiplicateur 36. La photodiode est mobile dans un plan qui est le conjuqué par rapport à la lentille du plan de la photocathode 37 du tube 36. Ainsi l'image ponctuelle de la photodiode va pouvoir balayer toute la surface de la photocathode. Le tube comporte plusieurs étages de dynodes 34 et une anode 33.The inventors nevertheless had the idea of studying more precisely the effects of magnetic fields, using the experimental device of FIG. 3. A dark enclosure 30 has an internal partition 31 x 10 supporting a converging lens 32. and on the other side thereof are housed in the enclosure a photodiode 35 (point source of 0.5 mm) and a photomultiplier tube 36. The photodiode is movable in a plane which is the conjugate with respect to the lens of the plane of the photocathode 37 of the tube 36. Thus the point image of the photodiode will be able to scan the entire surface of the photocathode. The tube comprises several stages of dynodes 34 and an anode 33.

Le tube 36 est par exemple le modèle EMI 6262, polarisé de manière classique avec une haute tension de 1500 Volts. Enfin, une bobine 39 produit un champ magnétique orienté suivant l'axe principal 38 du tube, par exemple vers le bas (le sens du champ magnétique s'est avéré avoir peu d'importance jusqu'à présent).The tube 36 is for example the EMI 6262 model, conventionally polarized with a high voltage of 1500 Volts. Finally, a coil 39 produces a magnetic field oriented along the main axis 38 of the tube, for example downwards (the direction of the magnetic field has proven to be of little importance so far).

La figure 4 illustre en ordonnée le signal de sortie du tube en échelle logarithmique, en fonction du champ magnétique appliqué, porté linéairement en abscisse. Pour chaque valeur du champ, la photodiode a été placée en deux positions correspondant aux deux bords d'une des lamelles constituant les dynodes. Les points marqués » + « et » 0 correspondent respectivement aux bords inférieur et supérieur de la lamelle.FIG. 4 illustrates on the ordinate the output signal of the tube on a logarithmic scale, as a function of the magnetic field applied, plotted linearly on the abscissa. For each value of the field, the photodiode was placed in two positions corresponding to the two edges of one of the strips constituting the dynodes. The points marked »+« and » 0 correspond respectively to the lower and upper edges of the coverslip.

A champ magnétique nul, les deux points se confondent, et le gain est Go; Au fur et à mesure qu'augmente le champ magnétique, le gain décroît, et les deux points »+« et »O« se séparent de plus en plus. On constante la chute rapide du gain au dessus de B=0,003 Tesla tandis qu'au dessous de cette valeur, le gain reste sensiblement constant. Les inventeurs ont estimé que la valeur de 0,003 Tesla correspond à un rayon de courbure des trajectoires électroniques dans le champ magnétique de l'ordre de grandeur de la largeur des lamelles (3 mm). Lorsque le champ B dépasse 0,003 Tesla, le rayon de courbure de la trajectoire d'un électron secondaire émis par unedynode est faible, et l'électron a de grandes chances d'être recapturé par la lamelle, d'où la diminution rapide du gain avec le champ magnétique. Au contraire, lorsque le champ B est inférieur à 0,003 Tesla, l'électron a les plus grandes chances de gagner la dynode suivante d'où le gain sensiblement constant.At zero magnetic field, the two points merge, and the gain is G o ; As the magnetic field increases, the gain decreases, and the two points »+« and »O« separate more and more. The rapid fall in gain is constant above B = 0.003 Tesla while below this value, the gain remains substantially constant. The inventors estimated that the value of 0.003 Tesla corresponds to a radius of curvature of the electronic trajectories in the magnetic field of the order of magnitude of the width of the lamellae (3 mm). When the B field exceeds 0.003 Tesla, the radius of curvature of the trajectory of a secondary electron emitted by a dynode is small, and the electron is likely to be recaptured by the coverslip, hence the rapid decrease in gain with the magnetic field. On the contrary, when the B field is less than 0.003 Tesla, the electron has the greatest chance of gaining the next dynode, hence the substantially constant gain.

La figure 5 illustre, pour un champ magnétique de 0,012 Tesla, le signal de sortie du tube porté en ordonnée et en échelle logarithmique, en fonction de la position du point lumineux sur la cathode, porté linéairement en abscisse. Cette figure montre que le gain varie en fonction de la position de la source lumineuse, et que l'allure du gain reflète la structure en lamelles des dynodes.FIG. 5 illustrates, for a magnetic field of 0.012 Tesla, the output signal of the tube plotted on the ordinate and on a logarithmic scale, as a function of the position of the light point on the cathode, plotted linearly on the abscissa. This figure shows that the gain varies as a function of the position of the light source, and that the shape of the gain reflects the lamellar structure of the dynodes.

Ceci confirme le rôle du rayon de courbure des trajectoires électroniques, car un électron secondaire émis près du bord supérieur d'une lamelle a plus de chances d'être recapturé par celle-ci que l'électron secondaire émis près du bord inférieur.This confirms the role of the radius of curvature of the electronic trajectories, because a secondary electron emitted near the upper edge of a lamella is more likely to be recaptured by it than the secondary electron emitted near the lower edge.

Les inventeurs ont observé aussi une canalisation des trajectoires électroniques autor de l'axe du champ B. Si l'on revient à la figure 3, le domaine D devient d'autant plus petit que le champ B est plus élevé. Là encore, cela est du au rayon de courbure imposé aux trajectoires électroniques par le champ magnétique. Il en résulte la possibilité de localiser au niveau de l'anode l'origine A de l'électron primaire, en utilisant par exemple une anode fractionnée ou multi-anode. Aux forts champs magnétiques, l'effet de localisation du au champ magnétique est acquis à l'aide du tube multiplicateur d'électrons agencé selon la figure 3, qui conserve des propriétés multiplicatrices réelles, malgré un gain très inférieur à la valeur Go à champ nul. Cependant, le tube est alors inutilisable en pratique, à cause de son très faible gain.The inventors have also observed a channeling of the electronic trajectories autor of the axis of the field B. If we return to FIG. 3, the domain D becomes all the smaller as the field B is higher. Again, this is due to the radius of curvature imposed on the electronic trajectories by the magnetic field. This results in the possibility of locating at the level of the anode the origin A of the primary electron, by using for example a fractional or multi-anode anode. At strong magnetic fields, the localization effect of the magnetic field is acquired using the electron multiplier tube arranged according to FIG. 3, which retains real multiplying properties, despite a gain much less than the value G o at null field. However, the tube is then unusable in practice, because of its very low gain.

Les résultats expérimentaux portés aux figures 4 et 5 montrent que l'on peut améliorer le gain en réduisant la largeur des lamelles d'après le rayon de courbure imposé aux trajectoires électroniques par le champ magnétique.The experimental results given in FIGS. 4 and 5 show that the gain can be improved by reducing the width of the lamellae according to the radius of curvature imposed on the electronic trajectories by the magnetic field.

Des recherches plus poussées ont été faites en ce sens, à l'aide notamment d'une simulation des phénomènes intervenant dans un tube photomultiplicateur à dynodes vénitiennes tel que celui de la figure 1.Further research has been done in this direction, using in particular a simulation of the phenomena occurring in a photomultiplier tube with Venetian dynodes such than the one in figure 1.

Effectuée sur ordinateur à l'aide d'un programme de Monte Carlo, la simulation a pris en compte la configuration géométrique du tube, la valeur des potentiels entre électrodes, les données expérimentales sur l'émission secondaire des dynodes, ainsi que les effets accessoires tels que perte sur les bords et charge d'espace.Performed on a computer using a Monte Carlo program, the simulation took into account the geometrical configuration of the tube, the value of the potentials between electrodes, the experimental data on the secondary emission of the dynodes, as well as the accessory effects. such as edge loss and space charge.

Le champ électrique étant ainsi bien établi, de même que l'émission secondaire, les effets du champ magnétique sur les trajectoires électroniques ont pu être étudiés.The electric field being thus well established, as well as the secondary emission, the effects of the magnetic field on the electronic trajectories could be studied.

La simulation et ses vérifications expérimentales ont permis d'aboutir à plusieurs structures particulières de dynodes qui procurent une bonne localisation, ainsi qu'un gain amélioré, et font l'objet de la présente invention.The simulation and its experimental verifications made it possible to arrive at several particular structures of dynodes which provide good localization, as well as improved gain, and are the subject of the present invention.

La figure 6 illustre la première de ces structures, considérée actuellement comme préférable. Chaque dynode comprend ici deux niveaux. Ainsi la dynode Dn-1 comprend les niveaux 61 et 62. Le niveau 61 comprend une série de lamelles ou plutôt de barreaux allongés dont la section est un triangle rectangle isocèle de base 0,5 mm. La base est perpendiculaire à l'axe principal du tube, et exposée à la dynode suivante. L'intervalle libre entre les sommets des bases de deux barreaux adjacents est également de 0,5 mm. Le second niveau 62, placé à 2,5 mm du premier, est constitué de la même manière, mais ses barreaux sont alignés sur les espaces libres entre ceux de l'étage précédent, de sorte que vu de dessus l'ensemble de la dynode constitue une structure sans espace libre. La seconde dynode Dn est semblable à la première, son premier niveau 63 étant décalé de 10 mm par rapport au niveau 61. Enfin, les surfaces actives sur le plan de l'émission électronique secondaire sont à chaque niveau les deux surfaces inclinées à 45°, définies par les côtés de l'angle droit du triangle rectangle isocèle. Une tension de 150 Volts est établie entre les niveaux 61 et 62, une tension de 600 Volts entre les étages 61 et 63, et à nouveau une tension de 150 Volts entre les étages 63 et 64, la polarisation se répétant ainsi périodiquement pour l'ensemble des dynodes.Figure 6 illustrates the first of these structures, currently considered preferable. Each dynode here comprises two levels. Thus the dynode D n - 1 comprises the levels 61 and 62. The level 61 comprises a series of strips or rather of elongated bars whose section is an isosceles right triangle with a basic 0.5 mm. The base is perpendicular to the main axis of the tube, and exposed to the next dynode. The free space between the vertices of the bases of two adjacent bars is also 0.5 mm. The second level 62, placed 2.5 mm from the first, is constituted in the same way, but its bars are aligned on the free spaces between those of the previous floor, so that seen from above the whole of the dynode constitutes a structure without free space. The second dynode D n is similar to the first, its first level 63 being offset by 10 mm from level 61. Finally, the surfaces active on the plane of the secondary electronic emission are at each level the two surfaces inclined at 45 °, defined by the sides of the right angle of the isosceles right triangle. A voltage of 150 volts is established between the levels 61 and 62, a voltage of 600 volts between the stages 61 and 63, and again a voltage of 150 volts between the stages 63 and 64, the polarization being thus repeated periodically for the set of dynodes.

Avec 14 dynodes (à deux niveaux chacune), un champ électrique de 600 Volts/cm et un champ magnétique de 0,04 Tesla Gauss, un tel multiplicateur d'électrons est susceptible d'atteindre une résolution spatiale (à mi-hauteur) de ± 1,5 mm pour un gain de l'ordre de 107. Une autre structure, mécaniquement plus complexe, est illustrée sur la figure 7. La notion de dynodes séparées est diluée dans cette structure, car l'ensemble des dynodes est constitué d'un grand nombre de niveaux équidistants, tels 71 à 76 qui en représentent une partie. Chaque niveau comprend des barreaux identiques à ceux de la figure 6, mais séparés par un espace libre de 2,0 mm. Les barreaux d'un niveau donné sont aécalés de 0,5 mm par rapport à ceux du niveau précédent, vers la gauche par exemple. Ainsi, le second barreau du niveau 76 se trouve à la verticale du premier barreau du niveau 71, à partir de la gauche. L'ensemble des niveaux 71 à 75 forme un système opaque pour un faisceau d'électrons parallèles à l'axe z. Bien que la structure soit régulière selon l'axe Oz, on peut donc considérer qu'un étage de dynode correspond à 5 grilles ou niveaux consécutifs, tels 71 à 75. Le pas entre étages est de 12,5 mm. Avec 14 étages, un champ magnétique de 0,041 Tesla et un potentiel augmentant de 400 Volts par étage, (soit un champ électrique d'environ 400 Volts/ cm), un tel multiplicateur d'électrons est susceptible d'atteindre une résolution spatiale (à mi-hauteur de la distribution des impacts sur l'anode) de ± 1,5 mm, pour un gain de l'ordre de 107.With 14 dynodes (at two levels each), an electric field of 600 Volts / cm and a magnetic field of 0.04 Tesla Gauss, such an electron multiplier is likely to reach a spatial resolution (at mid-height) of ± 1.5 mm for a gain of the order of 10 7 . Another structure, mechanically more complex, is illustrated in FIG. 7. The concept of separate dynodes is diluted in this structure, because the set of dynodes consists of a large number of equidistant levels, such as 71 to 76 which represent them. a part. Each level includes bars identical to those in Figure 6, but separated by a free space of 2.0 mm. The bars of a given level are 0.5 mm apart from those of the previous level, to the left for example. Thus, the second level 76 bar is located vertically from the first level 71 bar, from the left. The set of levels 71 to 75 forms an opaque system for an electron beam parallel to the z axis. Although the structure is regular along the Oz axis, we can therefore consider that a dynode stage corresponds to 5 consecutive grids or levels, such as 71 to 75. The pitch between stages is 12.5 mm. With 14 stages, a magnetic field of 0.041 Tesla and an increasing potential of 400 Volts per stage, (i.e. an electric field of approximately 400 Volts / cm), such an electron multiplier is likely to reach a spatial resolution (at mid-height of the impact distribution on the anode) of ± 1.5 mm, for a gain of the order of 10 7 .

Généralement, les inventeurs ont observé que les structures de dynodes dont les barreaux ont une section symétrique par rapport à l'axe z sont avantageuses, comme procurant une meilleure homogénéité du champ électrique, et par là une meilleure résolution spatiale. A cet égard, on peut bien entendu remplacer les barreaux à section droite en triangle rectangle isocèle par des barreaux équivalents, par exemple à section circulaire et de diamètre voisin de la dimension de la base ou hypoténuse du triangle isocèle, rendus capables d'émission secondaire au moins sur leur partie supérieure.Generally, the inventors have observed that the structures of dynodes whose bars have a section symmetrical with respect to the z axis are advantageous, as providing a better homogeneity of the electric field, and thereby a better spatial resolution. In this respect, it is of course possible to replace the bars with a straight section in an isosceles right triangle with equivalent bars, for example with a circular section and a diameter close to the dimension of the base or hypotenuse of the isosceles triangle, made capable of secondary emission. at least on their upper part.

Une autre structure de dynodes est illustrée sur la figure 8. Comme celle de la figure 7, elle présente des niveaux 81 à 86 d'éléments actifs régulièrement répartis selon l'axe Oz, et décalés successivement d'une valeur égale à la petite dimension de ces éléments actifs, projetée sur l'axe x (0,5 mm); là encore, l'espace libre entre deux éléments actifs est de 2,0 mm, si bien que les éléments actifs du niveau 86 se trouvent à la verticale de ceux du niveau 81. Mais, cette fois, au lieu des barreaux à section triangulaire, les éléments actifs sont des lamelles vénitiennes, inclinées à 45° toutes du même côté, et dont seule la face orientée vers le haut est capable d'émission secondaire. Un étage est ici encore constitué de 5 niveaux adjacents de lamelles, et le pas entre étages est de 5 mm. Avec 14 étages, une tension entre étages de 300 Volts (soit un champ électrique de 600 Volts/cm et un champ magnétique de 0,023 Tesla, la résolution spatiale à mi-hauteur est de ±2 mm, et le gain de l'ordre de 108.Another structure of dynodes is illustrated in FIG. 8. Like that of FIG. 7, it has levels 81 to 86 of active elements regularly distributed along the axis Oz, and offset successively by a value equal to the small dimension. of these active elements, projected onto the x axis (0.5 mm); here again, the free space between two active elements is 2.0 mm, so that the active elements of level 86 are vertical to those of level 81. But, this time, instead of the bars with triangular section , the active elements are Venetian lamellae, inclined at 45 ° all on the same side, and of which only the face facing upwards is capable of secondary emission. A stage is again made up of 5 adjacent levels of lamellas, and the pitch between stages is 5 mm. With 14 stages, a voltage between stages of 300 Volts (i.e. an electric field of 600 Volts / cm and a magnetic field of 0.023 Tesla, the spatial resolution at half height is ± 2 mm, and the gain of the order of 1 08 .

La remarque faite quant au rôle de la symétrie des éléments actifs par rapport à l'axe z se trouve donc confirmée, puisque la résolution spatiale est moins bonne que dans le cas des figures 6 et 7. En revanche, le gain est meilleur.The remark made as to the role of the symmetry of the active elements with respect to the z axis is therefore confirmed, since the spatial resolution is less good than in the case of FIGS. 6 and 7. On the other hand, the gain is better.

Une autre observation importante et surprenante a été faite. Les structures proposées sont distribuées selon l'axe x, mais continues suivant l'axe y. On pourrait donc s'attendre à n'avoir aucune localisation des électrons dans la direction de l'axe y. En réalité, on obtient dans la direction y une résolution spatiale pratiquement équivalente à celle de la direction x; par voie de conséquence, il en est de même dans toutes les directions du plan de la photocathode. Il est estimé que cette propriété remarquable est due à la courbure des trajectoires électroniques du fait du champ magnétique appliqué.Another important and surprising observation was made. The proposed structures are distributed along the x axis, but continuous along the y axis. We could therefore expect to have no localization of the electrons in the direction of the y axis. In reality, we obtain in the y direction a spatial resolution practically equivalent to that of the x direction; as a consequence, it is the same in all directions of the photocathode plane. It is estimated that this remarkable property is due to the curvature of the electronic trajectories due to the applied magnetic field.

Les explications suivantes ont été développées à propos du fonctionnement des structures des figures 6 à 8:The following explanations have been developed concerning the operation of the structures of FIGS. 6 to 8:

Figure 6Figure 6

Si un électron primaire frappe la grille 61, les électrons secondaires ainsi produits doivent passer entre les barreaux de la grille 62 pour aller atteindre l'une ou l'autre des grilles 63 et 64, et ainsi de suite, compte tenu des dimensions de la géométrie de la structure. On dira alors que les trajectoires des électrons issus de la grille 61 forment un noeud entre les barreaux de la grille 62.If a primary electron hits the grid 61, the secondary electrons thus produced must pass between the bars of the grid 62 to reach one or the other of the grids 63 and 64, and so on, taking into account the dimensions of the structure geometry. We will then say that the trajectories of the electrons coming from the grid 61 form a knot between the bars of the grid 62.

Figure 7Figure 7

Les trajectoires des électrons secondaires issus de la grille 71 forment un premier noeud au niveau de la grille 72 (z=2,5 mm), entre ses barreaux. Elles forment un second noeud pour z=10,5 mm soit légèrement en dessous de la grille 75. Les deux noeuds sont sensiblement alignés avec point d'émission dans la direction z, et les électrons ont alors les plus grandes chances de toucher la grille 76 ou une autre des grilles consécutives formant l'étage suivant, en évitant les grilles 72 à 75.The trajectories of the secondary electrons from the grid 71 form a first node at the level of the grid 72 (z = 2.5 mm), between its bars. They form a second node for z = 10.5 mm, slightly below the grid 75. The two nodes are substantially aligned with emission point in the z direction, and the electrons then have the greatest chance of touching the grid 76 or another of the consecutive grids forming the next stage, avoiding the grids 72 to 75.

Figure 8Figure 8

Les trajectoires sont plus complexes, en raison de la moins bonne homogénéité du champ électrique, due à l'asymétrie des lamelles par rapport à l'axe z.The trajectories are more complex, due to the poorer homogeneity of the electric field, due to the asymmetry of the lamellae with respect to the z axis.

Il semble néanmoins que les conditions quant aux noeuds des trajectoires soient comparables à celles de la structure illustrée figure 7.It nevertheless seems that the conditions with regard to the nodes of the trajectories are comparable to those of the structure illustrated in FIG. 7.

Dans tous les cas, la réalisation de ces conditions de noeuds de trajectoire, que l'on appelle ici »focalisation hélicoidale« tient au rapport entre les champs électrique et magnétique, compte tenu de la géométrie et de la structure et de ses dimensions. C'est cette focalisation hélicoïdale qui donne la propriété de localisation des trajectoires électroniques, c'est-à-dire la bonne résolution spatiale dans le plan xy. A cet égard, on observe que si l'on multiplie conjointement les champs électrique et magnétique par un facteur K, tout en divisant les dimensions de la structure et le temps par le même facteur K, l'équation du mouvement électronique reste vérifiée.In all cases, the achievement of these conditions of trajectory nodes, which we call here "helical focusing" is due to the relationship between the electric and magnetic fields, taking into account the geometry and the structure and its dimensions. It is this helical focusing which gives the property of localization of the electronic trajectories, that is to say the good spatial resolution in the xy plane. In this respect, we observe that if we jointly multiply the electric and magnetic fields by a factor K, while dividing the dimensions of the structure and time by the same factor K, the equation of electronic movement remains verified.

Bien entendu, la résolution spatiale pourra être d'autant meilleure que les éléments actifs des grilles seront rendus plus fins, les champs électrique et magnétique étant alors augmentés en conséquence.Of course, the spatial resolution can be all the better as the active elements of the grids are made finer, the electric and magnetic fields then being increased accordingly.

Il a également été observé que les multiplicateurs d'électrons selon l'invention possèdent une meilleure résolution temporelle, que les photo- multiplicateurs du type persienne, leur temps de montée pouvant descendre à moins de 2 nanosecondes (10 à 90% du pic de courant) contre environ 10 nanosecondes pour la plupart des photomultiplicateurs classiques à dynodes vénitiennes.It has also been observed that the electron multipliers according to the invention have better temporal resolution, than the photo-multipliers of the louver type, their rise time being able to drop to less than 2 nanoseconds (10 to 90% of the current peak ) against about 10 nanoseconds for most conventional Venetian dynode photomultipliers.

Il a encore été observé que les multiplicateurs d'électrons sont moins sujets à des problèmes de charge d'espace dans les derniers étages que ceux de la technique antérieure. En effet, ils présentent une meilleure linéarité du gain en fonction du courant d'électrons, par rapport aux photomultiplicateurs à dynodes vénitiennes, sinon à ceux dits »box-type«.It has also been observed that electron multipliers are less subject to space charge problems in the upper stages than those of the prior art. Indeed, they have a better linearity of the gain as a function of the current of electrons, compared to photomultipliers with Venetian dynodes, if not those called "box-type".

Ces retombées des structures décrites plus haut constituent elles aussi des avantages importants de la présente invention, que l'on peut utiliser indépendamment de la localisation.These fallout from the structures described above also constitute important advantages of the present invention, which can be used independently of the location.

L'invention fournit essentiellement un tube multiplicateur d'électrons capable de localisation, c'est-à-dire dans lequel il existe une correspondance fine entre les points de départ des électrons sur la surface d'entrée du tube et les points d'arrivée des électrons sur la surface de sortie du tube. La finesse de cette correspondance est défine par la résolution spatiale.The invention essentially provides an electron multiplier tube capable of localization, that is to say in which there is a fine correspondence between the points of departure of the electrons on the entry surface of the tube and the points of arrival. electrons on the exit surface of the tube. The finesse of this correspondence is defined by the spatial resolution.

L'application actuellement préférée est celle des photomultiplicateurs, la surface d'entrée étant alors une photocathode. On peut cependant appliquer l'invention avec toutes sortes de cathodes émettant sélectivement les électrons sur leur surface (cathode divisée par exemple). On peut encore injecter à travers la surface d'entrée du tube des électrons produits par une autre source (accélérateur d'électrons par exemple). Le terme »surface émettrice d'électrons« couvre ici l'ensemble de ces situations. La surface de sortie du tube, ou »surface réceptrice d'électrons«, devra bien entendu permettre une détection sélective des électrons suivant leur point d'arrivée. La réalisation la plus simple en est anode divisée en fragments, munis de connexions électriques individuelles. La résolution spatiale »brute« ainsi permise (par exemple Ax = ± mm) est naturellement limitée par les dimensions des fragments d'anode. Cette résolution spatiale brute peut être améliorée sensiblement si l'on traite les signaux provenant des différents fragments d'anode, le traitement comprenant l'analyse en amplitude des signaux issus de plusieurs fragments d'anode adjacente. A partir d'une résolution brute /lx= ±2 mm, et pour une dimension des fragments d'anode du même ordre de grandeur que cette résolution brute, on obtient après traitement une résolution de ±0,1 mm.The currently preferred application is that of photomultipliers, the input surface then being a photocathode. The invention can however be applied with all kinds of cathodes selectively emitting electrons on their surface (divided cathode for example). It is also possible to inject electrons produced by another source through the entry surface of the tube (electron accelerator for example). The term "electron emitting surface" here covers all of these situations. The exit surface of the tube, or "electron receiving surface", should of course allow selective detection of the electrons according to their point of arrival. The simplest embodiment is anode divided into fragments, provided with individual electrical connections. The "raw" spatial resolution thus allowed (for example Ax = ± mm) is naturally limited by the dimensions of the anode fragments. This raw spatial resolution can be improved considerably if the signals from the different anode fragments are processed, the processing comprising the amplitude analysis of the signals originating from several adjacent anode fragments. From a raw resolution / lx = ± 2 mm, and for a dimension of the anode fragments of the same order of magnitude as this raw resolution, a resolution of ± 0.1 mm is obtained after treatment.

De plus, et c'est une caractéristique très importante du dispositif proposé, la résolution est indépendante de la fluctuation statistique due au rendement quantique de la photocathode, puisque la source de photoélectrons est commune pour tous les fragments d'anode adjacents. La résolution est donc pratiquement indépendante de l'intensité lumineuse de la source analysée.In addition, and this is a very important characteristic of the proposed device, the resolution is independent of the statistical fluctuation due to the quantum yield of the photoca thode, since the photoelectron source is common for all adjacent anode fragments. The resolution is therefore practically independent of the light intensity of the source analyzed.

Un autre type de surface sensible applicable au lieu de fragments d'anode est l'écran électroluminescent, analogue aux écrans des tubes cathodiques, qui permet l'examen visuel et/ou photographique. La surface réceptrice d'électrons peut encore être réalisée comme dans les tubes de prise de vues de télévision, et comprendre une mosaïque de petits éléments qui se chargent sous l'effet des électrons reçus, tandis qu'un faisceau d'électrons analyseur vient balayer cette surface pour lire la charge de chaque élément de la mosaïque. On obtient ainsi un signal séquentiel qui, lié au balayage, définit la répartition spatiale des électrons reçus. Du fait du balayage séquentiel, ce type de surface réceptrice ne permet pas de bénéficier pleinement de la résolution temporelle du tube selon l'invention.Another type of sensitive surface applicable instead of anode fragments is the electroluminescent screen, analogous to cathode ray tube screens, which allows visual and / or photographic examination. The electron receiving surface can also be produced as in television picture tubes, and include a mosaic of small elements which are charged under the effect of the received electrons, while a beam of analyzer electrons comes to sweep this surface to read the charge of each element of the mosaic. A sequential signal is thus obtained which, linked to the scanning, defines the spatial distribution of the electrons received. Due to the sequential scanning, this type of receiving surface does not make it possible to fully benefit from the temporal resolution of the tube according to the invention.

Le multiplicateur d'électrons selon l'invention est susceptible de nombreuses applications:

  • détection directe d'électrons, de photons (multi-photomultiplicateur), amplificateur d'images à haut gain;
  • le domaine d'application est vaste et comprend notamment la détection de particules en physique nucléaire et physique des hautes énergies, la médecine, etc.
The electron multiplier according to the invention is capable of numerous applications:
  • direct detection of electrons, photons (multi-photomultiplier), high gain image amplifier;
  • the field of application is vast and includes in particular the detection of particles in nuclear physics and high energy physics, medicine, etc.

Plus précisément, un photomultiplicateur selon l'invention de diamètre 100 mm pourrait remplacer 50 à 100 petits photomultiplicateurs classiques à dynodes vénitiennes en offrant une excellente résolution spatiale (±1,5 mm), un gain pratiquement aussi bon, plus homogène et plus linéaire, et une résolution temporelle supérieure.More precisely, a photomultiplier according to the invention with a diameter of 100 mm could replace 50 to 100 small conventional photomultipliers with Venetian dynodes by offering excellent spatial resolution (± 1.5 mm), a gain that is practically as good, more homogeneous and more linear, and higher time resolution.

Bien entendu, la présente invention n'est pas limitée aux modes de réalisation décrits, et s'étend à toute variante conforme à son esprit. Par exemple, on peut utiliser des lamelles avec la géométric de la figure 6, ou bien des barreaux cylindriques avec les géométries des figures 6 et 7. On peut encore imaginer des variantes simple de la section droite en triangle rectangle isocèle, par exemple en rendant leur hypoténuse curviligne et concave.Of course, the present invention is not limited to the embodiments described, and extends to any variant in accordance with its spirit. For example, we can use slats with the geometry of Figure 6, or cylindrical bars with the geometries of Figures 6 and 7. We can still imagine simple variants of the cross section in isosceles right triangle, for example by making their curvilinear and concave hypotenuse.

Il semble en revanche important de conserver une disposition où chaque étage de dynode est constitué de plusieurs niveaux, décalés entre eux de manière à constituer ensemble une structure pratiquement opaque pour les électrons incidents.On the other hand, it seems important to keep a layout where each dynode stage is made up of several levels, offset between them so as to constitute together a practically opaque structure for the incident electrons.

Claims (14)

1. Electron multiplier apparatus, comprising an evacuated tube which contains several stages of dynodes with a distributes structure, capable of secondary reflex electronic emission when-they are struck by charged particles and means for receiving electrons, means producing an electron accelerating field directed substantially along a principal axis which passes through the stages of the dynodes towards the electron receiving means, and means producing a magnetic field directed substantially along the principal axis, characterised by the fact that:
a) each dynode stage comprises at least two levels of distributed dynode elements (61, 62; 71 to 75; 81 to 85),
b) these levels of dynode elements being spaced along the principal axis and being staggered with each other in each dynode stage in such a manner as to define a surface substantially impervious to movement of electrons substantially rectilinearly parallel to the principal axis,
c) the dynode elements of each layer possessing, in the direction transverse to the principal axis, a dimension chosen in relation to the magnetic field such that the average radius of curvature of projections orthogonal to the trajectories of the secondary electrons in a plane perpendicular to the axis of the tube are at least equal to the transverse dimension of the dynode elements and
d) the levels of dynode elements being also spaced such that practically no secondarily emitted electron from the first level of dynode elements of the dynode stages strikes the second level of dynode elements of the same stage, whilst practically all these secondary electrons strike a level of dynode elements of the following dynode stage.
2. Electron multiplier apparatus according to Claim 1, characterised by the fact that the trajectories of the said secondary electrons form a node at the level of the second level of dynode elements.
3. Electron multiplier apparatus according to either of Claim 1 and 2, characterised by the fact that the dynode stages comprise grids of parallel rods, each grid being substantially perpendicular to the principal axis.
4. Electron multiplier apparatus according to Claim 3, characterised by the fact that the minor dimension of the rods in the plane perpendicular to the principal axis, is less than 1 mm, and that the gap between two adjacent rods is at least equal to their minor dimension.
5. Electron multiplier apparatus according to Claim 4, characterised by the fact that the electric field is stronger than 200 V/cm, and the magnetic field is stronger than 0.005 Tesla.
6. Electron multiplier apparatus according to Claim 5, characterised by the fact that the minor dimension of the rods is approximately 0.5 mm, and that the electric field and the magnetic field are chosen correlatively the one to the other between 400 and 1000 V/cm, and 0.01 and 0.05 Tesla, respectively.
7. Electron multiplier apparatus according to any one of Claims 3 to 6, characterised by the fact that each dynode stage comprises two grids of rods spaced along the principal axis (61, 62), that in each grid, the rod are spaced by a distance equal to their minor dimension, that the two grids are staggered the one with the other by a distance equal to their minor dimension, and that the electric and magnetic fields are correlatively chosen so that a secondary electron emitted by a rod of the first grid practically always passes between the rods of the second grid.
8. Electron multiplier apparatus according to any one of Claims 3 to 6, characterised by the fact that each dynode stage comprises n grids of bars spaced along the principal axis (71-75; 81-85), that in each grid the bars are spaced by n times their minor dimension, that the n grids are successively staggered in the same direction by a distance equal to their minor dimension, each with respect to the preceding, and that the electric and magnetic fields are correlatively chosen for a secondary electron emitted by a rod of one grid on a parallel to the principal axis to practically pass on substantially the same parallel to the levels of the following grid and the nth grid.
9. Electron multiplier apparatus according to Claim 8, characterised by the fact that n = 5.
10. Electron multiplier apparatus according to any one of Claims 3 to 9, characterised by the fact that the rods (71-75) have a cross-section which is symmetrical with respect to a plane passing through the principal axis of the tube and the axis of their major dimension.
11. Electron multiplier apparatus according to any one of claims 3 to 10, characterised by the fact that the crosssection of the rods is of the right angle isoceles triangle type (71-75) with the hypotenuse facing towards downstream side of the trajectories of the electrons of the circular type, or of flat rectangular type with a predetermined inclination to the principal axis, the rods then being laminae.
12. Electron multiplier apparatus according to any one of Claims 1 to 11, characterised by the fact that it comprises a cathode or photocathode emissive of primary electrons in the directions of the stage of dynodes.
13. Electron multiplier apparatus according to any one of Claim 1 to 11, characterised by the fact that it comprises means for allowing to pass charged particles in the direction of the stage of dynodes.
14. Electron multiplier apparatus according to any one of Claims 1 to 13 characterised by the fact that the means for receiving electrons comprises a divided anode with multiple connections, an electro-luminescent surface or a mosaic surface analysable by a beam of electrons.
EP79401057A 1978-12-22 1979-12-21 Electron multiplying apparatus with axial magnetic field Expired EP0013235B1 (en)

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AT79401057T ATE6711T1 (en) 1978-12-22 1979-12-21 AXIAL MAGNETIC FIELD ELECTRON MULTIPLIER DEVICE.

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FR7836148 1978-12-22
FR7836148A FR2445018A1 (en) 1978-12-22 1978-12-22 ELECTRON MULTIPLIER TUBE WITH AXIAL MAGNETIC FIELD

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FR2566175B1 (en) * 1984-05-09 1986-10-10 Anvar ELECTRON MULTIPLIER DEVICE, LOCATED BY THE ELECTRIC FIELD
DE3709298A1 (en) * 1987-03-20 1988-09-29 Kernforschungsz Karlsruhe MICRO SECONDARY ELECTRONIC MULTIPLIER AND METHOD FOR THE PRODUCTION THEREOF
US8048439B2 (en) 2003-11-17 2011-11-01 Btg International Ltd. Therapeutic foam
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR824648A (en) * 1936-11-20 1938-02-14 Electrical Res Products Electron Discharge Device
US2172738A (en) * 1936-02-03 1939-09-12 Cathode ray tube

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE413168A (en) * 1935-01-08
US2115155A (en) * 1936-10-21 1938-04-26 Rca Corp Electron multiplier
GB483575A (en) * 1936-10-21 1938-04-21 Marconi Wireless Telegraph Co Improvements in or relating to electron discharge device arrangements
US2196278A (en) * 1937-08-31 1940-04-09 Bell Telephone Labor Inc Electron discharge apparatus
GB504927A (en) * 1937-10-28 1939-04-28 James Dwyer Mcgee Improvements in or relating to electron permeable electrodes
GB508106A (en) * 1937-11-24 1939-06-26 Hans Gerhard Lubszynski Improved electron multiplying electrodes in electric discharge apparatus
US2305179A (en) * 1938-05-27 1942-12-15 Emi Ltd Electron multiplier
US2712738A (en) * 1952-01-10 1955-07-12 Linde S Eismaschinen Ag Method for fractionating air by liquefaction and rectification
GB902090A (en) * 1957-11-12 1962-07-25 Emi Ltd Improvements in or relating to electron discharge devices
NL262542A (en) * 1959-09-30
GB976619A (en) * 1960-03-05 1964-12-02 Emi Ltd Improvements in or relating to photo-emissive devices
US3197662A (en) * 1960-03-11 1965-07-27 Westinghouse Electric Corp Transmissive spongy secondary emitter
US3191086A (en) * 1960-11-23 1965-06-22 Radames K H Gebel Secondary emission multiplier intensifier image orthicon
GB1470162A (en) * 1973-02-27 1977-04-14 Emi Ltd Electron multiplying arrangements

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2172738A (en) * 1936-02-03 1939-09-12 Cathode ray tube
FR824648A (en) * 1936-11-20 1938-02-14 Electrical Res Products Electron Discharge Device

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JPS5590047A (en) 1980-07-08
US4339684A (en) 1982-07-13
FR2445018A1 (en) 1980-07-18
ATE6711T1 (en) 1984-03-15
JPH0413814B2 (en) 1992-03-10
JPH0231457B2 (en) 1990-07-13
FR2445018B1 (en) 1982-02-26
EP0013235A1 (en) 1980-07-09
DE2966814D1 (en) 1984-04-19

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