WO2007003723A2

WO2007003723A2 - Multi-channel electron multiplier tube

Info

Publication number: WO2007003723A2
Application number: PCT/FR2005/050749
Authority: WO
Inventors: Philippe Bascle
Original assignee: Photonis
Priority date: 2005-06-29
Filing date: 2005-09-15
Publication date: 2007-01-11
Also published as: WO2007003723A3

Abstract

The invention relates to a multi-channel photomultiplier tube (1) comprising: a photon-transparent window (5) which is equipped with an inner face (7), and a light-emitting layer (2) which is disposed on the inner face (7) of the transparency window (5). The invention is characterised in that the transparency window (5) comprises an equal number of concavities (8) to the number of channels in the tube (1), said concavities (8) taking the form of parts (8) that are hollowed out from the inner face (7) of the transparency window (5), with each concavity corresponding to a channel. In this way, the transparency window (5) is equipped with hollow parts (8) and thick parts (23) corresponding to the non-hollow parts, the surfaces of said hollow parts (8) being covered with a light-emitting layer (2).

Description

MULTI-CHANNEL ELECTRON MULTIPLIER TUBE

DESCRIPTION

TECHNICAL FIELD The present invention relates to a multi-channel electron multiplication tube.

STATE OF THE PRIOR ART

A multi-channel photomultiplier tube generally comprises, inside a gas-tight vacuum envelope, a light-sensitive electrode, called a photocathode, an electronic distribution optic, an electron multiplier for multiplying the electrons emitted by the photocathode and a channel anode that collects the multiplied electrons in each of the pathways.

The patent application EP 0487 178 describes a multi-channel tube, in which each of the channels corresponds to part of a common photocathode. The separation between channels results from an input optics comprising a separator composed of a set of walls perpendicular to the plane of the common photocathode. Each lane has its own multiplier consisting of a succession of dynodes. Parts of electrodes that are electrically distinct at the rate of one part per channel make it possible to collect the signal specific to each channel. It is known that such multichannel planar cathode tubes have a significant dispersion of transit time between the photocathode and the first dynode. The multichannel tube described in application EP 0487 178 provides for a dynode gain adjustment, but this dynode does not allow an adjustment of the transit times. As a result, such multichannel tubes can not be used in applications for which the dispersion of the transit times is a penalizing factor. Monovoic tubes are known in which the dispersion of the transit times between the photocathode and the first dynode of the multiplier is reduced by the fact that the photocathode is mounted on a hemispherical surface. Because of this form the distance between the different points of the photocathode and a center is equal. This geometry helps to reduce the dispersion of the transit time.

DISCLOSURE OF THE INVENTION The subject of the invention is a multi-channel photomultiplier tube having an improved temporal resolution compared to the multi-way tubes known from the prior art. In the prior art cited above, the photocathode is disposed on the inner face of the transparent window wall. This inner face is flat. As a result, the electrons of a path emitted by the edge portions of the photocathode plane portion corresponding to this pathway have longer trajectories than the trajectories of the electrons emitted by the central portion of this same photocathode portion.

According to the invention, the internal face of the transparency window comprises a number of concavities, preferably hemispherical, equal to the number of channels of the tube. The photocathode is as in the prior art, deposited on the inner face of the wall forming a window of transparency. Each concavity corresponds to one way. Each concavity has a surface of revolution around a central axis. As a result, the distances between an electron concentration focal point located on the central axis, and each point of the part of the photocathode corresponding to this path, are substantially equal to each other. For each channel, the dispersion of the transit times between the part of the photocathode corresponding to this channel and the focal point results only from differences in the initial velocity of the electrons at the moment of emission and possibly of the forms of the equipotential surfaces. The shapes of these surfaces created by the shapes of the electrodes of the focusing optics can lead to slight differences in the distances traveled by an electron to cross these different equipotential surfaces.

In the embodiment which will be described in detail, the transparency window has a planar outer face and an inner face having planar portions where the concavities are not present. The flat portions of the internal face are located in a plane that is parallel to the plane of the outer face. The distance between these parallel planes is the thickness of the transparency window. The wall comprising the window of transparency thus has thick parts corresponding to non-hollow parts, whose thickness is what has been called the thickness of the window of transparency, and hollow portions thinner than these thick parts. The concavities of revolution thus appear as hollows from the plane of the internal face.

For all these purposes, the invention relates to a multi-channel photomultiplier tube comprising a sealed envelope, having a photon-transparent window wall, and other walls, the transparency window comprising a flat outer face and a face. internal, an axial direction of the tube being a direction perpendicular to the planar face, the tube having in the order in the direction of the axial direction, a photocathode in the form of a light emitting layer disposed on the inner face of the transparency window in order to receive light photons having passed through the transparency window, focusing optics distributing the electrons coming from the photocathode in the different channels, and directing them towards a first dynode specific to each channel, - a stack of multiplier stages , having in the direction of travel electrons, a first stage comprising the first dynodes, and a stack multiplier stages, including a penultimate stage and a last stage, an anode formed by conductors insulated from each other by an insulated conductor for each multiplication channel, said anode being downstream of the last stage multiplier or between the penultimate and the last multiplier stage, connecting means passing through the sealed envelope and having contacts of external connections to the envelope, themselves connected to internal electrical connection connections, for connecting the dynodes, the photocathode, the electrodes forming the focusing optics, and the different insulated conductors (51) forming the anode together, their respective operating voltage, characterized in that, the window of transparency comprises a number of concavities equal to the number of channels of the tube, each concavity corresponding to a channel, these concavities being in the form of parts hollowed from the internal face of the transparency window, the wall comprising the transparency window thus having hollow parts and thick parts corresponding to non-hollow parts, the surfaces of the hollow parts receiving the light-emitting layer forming the photocathode, each hollow surface thus forming a zone of photocathode. In one embodiment, one of the faces of the transparency window has ridges located in the thick parts of this window, these striations being filled by a reflective or absorbing photon product. In one embodiment, the tube further comprises immediately downstream of the photocathode a set of conductive walls, perpendicular to the flat face of the window of transparency. Preferably, these walls are in the form of cylinders at the rate of one cylinder per cubic meter. way of the tube. The word cylinder is used in its geometric sense. It can be circular based, or regular polygonal. The axes of regular polygons or circles coincide with the axes of the caps forming the photocathode portions.

Depending on the electrical connection of the conductive walls, these walls may have a deflection function or a first focusing optical electrode. If these walls are at the same potential as the cathode, then it is a deflector. If these walls are at an algebraic potential greater than that of the cathode, then it is an accelerating focusing gate, forming part of an input optics in the form of a triode or possibly a tetrode. The advantage of such optics is their ability to reduce the transit time of electrons between the cathode and the multiplier.

In one embodiment, each concavity of the inner face of the window of transparency of the tube is a hemispherical cap, each of circles determined by the intersection between a plane parallel to the plane plane plane and said caps being tangent or very close two more of these circles if it is a corner portion of the transparency window, three other circles if it is a peripheral portion of the transparency window other than the corner portions and four other circles if it is a circle not occupying a peripheral position. In one embodiment, the focusing optics comprises an accelerating and focusing electrode per channel, at least one or each of these electrodes comprising: a cylindrical conducting wall having an axis perpendicular to the flat face of the transparency window; , this cylindrical wall having in the axial direction two ends, a first close to the photocathode and a second remote from the photocathode, the first end being defined by the intersection of the cylindrical wall with a plane not parallel to the flat face of the window of transparency and secant to all generatrices of the cylindrical wall and the second end being defined by an intersection with a plane parallel to the flat face of the transparency window, the cylindrical wall thus having in the axial direction, a length generator maximum and a generatrix of minimum length diametrically opposed to each other and a planar wall parallel to the outer face of the window of transparency, and internally connected to the cylindrical conductive wall at its second end, this planar wall having a zone for the passage of electrons, this passage zone being closer to the generator of maximum length of the cylindrical wall of the generatrix of minimum length of said cylindrical wall.

In the preferred embodiment all the accelerating and focusing electrodes are identical to each other. In one embodiment, each cylindrical wall of a focusing electrode is polygonal in base and has a plurality of wall portions, one part per side of the polygon forming the base of the cylindrical wall. Parts of each of the cylindrical walls are integral parts of a first plate of cylindrical wall portions, which portions are connected to said first plate by a fold. In one embodiment, cylindrical wall portions of the focusing accelerator electrodes are integral parts of a second plate of cylindrical wall portions different from the first plate, which portions are connected to said second plate by a fold.

In one embodiment of the cylindrical wall portions of the focusing accelerator electrodes have a first sub-portion connected by a fold with a cylindrical wall portion integral with said first plate, and a second sub-portion connected by a fold with a cylindrical wall portion integral with said second plate.

In one embodiment, the planar walls having the electron passage areas of each of the individual focusing electrodes are integrally formed in a bottom plate having as many passage areas as channels. In one embodiment, a first dynode of at least one of the channels has in the axial direction a first end close to the cathode and a second far end, each first dynode having a face in a direction defined by the perpendicular to the outer face of the transparency window, under the electron passage zone through the accelerator and focusing electrode.

In one embodiment, an electron reception face of each of the first dynodes of the first dynode stage, said electron receiving face being located in a direction defined by the perpendicular to the outer face of the transparency window. , under a zone of passage of electrons through the accelerating and focusing electrode, is formed in one piece in a plate of first dynodes, each electron receiving face being connected by a fold to the continuum of said plate first dynodes. Embodiments in which cylindrical wall portions or the bottom wall of the focusing accelerating electrodes or else the electron receiving faces of the first dynodes are made from cut and folded conductive plates have the facility of realization since all the walls can be made by collective cutting and folding operations. In addition, the relative positioning of the electrode walls and their manipulation are very easy since they are in one piece. •

In one embodiment, a first dynode of each channel is constituted by a set of conductive walls together forming a box without a lid having an opening on the side of its first end, the set of walls having first to third planar walls perpendicular to the outer face of the transparency window, the first and second walls being parallel to each other and perpendicular to the ends of the third wall, these first and second walls; having in a direction perpendicular to the third wall a greater length at the first end of the box than at the second end, a fourth wall facing the third wall having its first end perpendicular to the outer face of the window of transparency and having a concavity facing the photocathode this fourth wall being perpendicular to the first and second walls. In one embodiment, the anode or gain control stage comprises an assembled cassette having a plurality of electrically insulated conductive portions of each other, each conductive portion being further provided with a connection connection of its own. in one piece with the conductive part to which the connection is connected,

first and second insulating spacers, at least one of the spacers having apertures through which each of the conductive parts is exposed, each of the conductive parts and at least a part of the connecting connection which corresponds to it being housed between the first and the second spacer. In one embodiment of the cassette, the conductive parts of the anode or the gain control stage and their connecting links have parts having a small thickness and parts having a greater thickness greater than that of the parts. of small thickness, at least a portion of the thick parts constituting part of first positioning means of the electrically insulated parts of each other, a complementary part of these first positioning means being constituted by openings or niches of the one or the other of the spacers housing thick parts.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with the aid of the accompanying drawings in which:

FIG. 1 represents a longitudinal section along the plane AA of FIG. 2 of a photomultiplier tube according to the invention. FIG. 2 represents a view from above of the window of transparency of a tube according to the invention. FIG. 3 represents an exploded perspective view of a portion of an exemplary embodiment of a tube according to the invention, the part shown comprising a deflector, focusing optics, a first dynode and a stack of multiplier stages.

FIG. 4 represents an exploded perspective view of a set of four cut and folded plates whose first three plates are intended after assembly to form together a set of focusing electrodes at a rate of one per channel and the last of which is intended to form at least a portion of a set of first dynodes one by one, FIG. 5 is a perspective view of the first three plates shown FIG. 4, folded and assembled to form the set of focusing electrodes,

Figure 6 shows a perspective view of a portion of a four-way tube according to the invention, a portion of the tube casing being cut to reveal the inside of the tube.

Figure 7 shows a top view of a machined plate having a plurality of conductive parts, each provided with a connecting connection, and a temporary holding part.

FIG. 8 represents an exploded perspective view of insulating spacers, of the machined plate, and means of tight assembly of the two spacers.

FIG. 9 represents a perspective view of an assembled cassette suitable for producing a gain control dynode or an anode of a multi-channel tube according to the invention. In the different figures of the same reference numbers designate elements of the same nature or having the same function. In this way an already described element of a previous figure will not necessarily be described in a following figure. DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 represents a partial longitudinal section of a nine-channel photomultiplier tube 1 according to the invention. This section is along line AA of FIG. 2. FIG. 6 represents a perspective view of a portion of another four-way tube 1 according to the invention, a part of the envelope of the tube being cut to leave appear inside the tube. Only the original part of the tubes 1 shown in FIGS. 1 and 6 will be described in detail. This is the transparency window 5, a means 40, channel separation, a linear focusing optics 9, and a first dynode of each of the channels. In an optional mode of realization the tube

1 according to the invention further comprises an anode comprising as many isolated conductors as channels, simpler to manufacture than those of the prior art. The photomultiplier tube 1 comprises a sealed envelope 4, formed by a set of walls assembled together. In the example shown, a first wall 3 has a cylindrical sleeve shape of axis AA ', for example with a rectangular or square base. The cylindrical sleeve 3 is preferably made of an insulating material, for example glass. The sleeve is completed at one end by a wall 5 forming a photon transparency window. It is completed, in a known manner, at the other end, by a bottom wall 10. Connecting pins 20 of the different electrodes located at the inside of the sealed envelope 4 pass sealingly, and so in itself known also through this bottom wall. When the tube 1 is in operation these pins 20 are coupled to voltage sources, applying operating voltages to the different electrodes of the tube 1.

The wall 5 forming the window of transparency of the tube comprises a plane outer face 6 and an inner face 7 having as many concavities 8 as channels, that is to say nine in the example shown in FIG. 1 and four in FIG. 6. Each of the concavities 8 is turned towards the interior of the tube 1. Each of the concavities 8 is, in the examples shown, a spherical cap 8. Each cap center 8 is located on an axis perpendicular to the flat face 6 outside the tube 1. A cathode 2 emitting photo is disposed on the inner face 7 of the wall 5 forming the window 5 of transparency, so as to receive light photons having passed through the transparency window 5. In the example shown in FIG. 1, the photocathode 2 is deposited only on the inner surface of the concavities 8. In the example shown in FIG. 6, the photocathode 2 is deposited on the entire inner face 7. In a manner known per se, the photocat hode 2 is constituted by a layer of a light-emitting material, for example a layer of a multi-alkaline material or silver-oxygen-cesium, or cesium-antimony. It may also be another light emitting material. The material is chosen according to its spectral characteristics of photo emission and wavelengths of the photons to which the photomultiplier tube will be applied.

FIG. 2 represents a view from above of the transparency window 5 of the nine-way tube represented in FIG. 1. The nine spherical caps 8 are represented in dashed lines by circles 12 representing the intersection of a cap 8 with a parallel plane in the plane of the outer face 6, and located at a distance from this outer face equal to the largest thickness of the transparency window 5. This fictitious plane will be called the inner plane of the transparency window 5. The circles 12 intersection of the caps 8 with the internal plane are arranged in a matrix manner in three rows and three columns. There are thus nine caps 8 including a central cap 8, four corner caps 8 and four caps 8 peripheral devices, each located between two corner caps 8 in the nine-way example here commented. In the example shown in FIG. 6, there are four corner caps 8. The tubes 1 according to the invention may comprise arrangements of channels in different rows and columns, for example two rows and three columns leading to a six-way tube, or two rows and four columns leading to an eight-way tube, these examples cited for illustrative purposes only.

Thus, the internal face of the transparency window comprises a number of concavities 8 in the form of caps, nine in the example shown in Figure 1, equal to the number of channels of the tube. Each concavity 8 corresponds to a channel. The wall forming 5 the transparency window has thick portions 23 corresponding to non-hollow portions and portions 8 thinner than the thick portions 23. The thick portions 23 are portions between the flat face 6 of the transparency window 5, and portions planes 24 of the inner face 7, located between the cavities 8.

In summary, each concavity 8 of the inner face 7 of the transparency window 5 is a hemispherical cap 8. Each of the circles 12 determined by the intersection between a plane parallel to the plane of the outer plane face 6 and said caps 8 is tangent to two other of these circles 12 if it is a corner portion of the transparency window 5, to three other circles 12 if it is a peripheral peripheral portion of the transparency window 5 other than the corner portions and four other circles if it is a circle not occupying a peripheral edge position. Optionally and in order to improve the separation of the channels, the transparency window 5 may include grooves 21 on its inner surface, or as shown in Figure 1 on its outer surface. These grooves 21 are drawn at the thick portions 23. In the example shown in Figures 1 and 2, these grooves 21 are in the form of rectilinear grooves. A projection of a central longitudinal line of each of the grooves 21 on the inner plane is tangent to circles 12 of intersection of the caps 8 with this inner plane, whose centers are aligned. In the example represented in FIG. 1, there are two first grooves 21 parallel to each other tangential to the central circles 12 aligned in a first direction, at diametrically opposite points of each of these central circles. There are also two second grooves parallel to each other and perpendicular to the first, aligned in a second direction, at diametrically opposite points of each of the central circles 12. The grooves are filled by a reflective material or absorbing photons. This embodiment provides a better separation of the channels because the photons striking the transparency window 5 at a portion of its surface located above a cap 8, are prevented either by reflection or by absorption to reach a part photocathode 2 does not correspond to the path defined by this cap 8.

Advantageously to further improve the separation of the tracks, the flat portions 24 of internal or external surfaces are coated with a reflective coating 22.

From the photocathode 2 to the bottom wall 10, the tube comprises in the order and in a manner known per se, a focusing optic 9, a first stage 90 of the first dynodes 31, an electron multiplier assembly and signal collection anode shown generally in the form of block 30, constituted in itself known manner of flat plates pierced with a multitude of holes and assembled in a compact parallel structure. The tube 1 further comprises a set 40 formed of as many walls conductive than paths. Each wall of the assembly 40 is in the example shown in Figure 3 of cylindrical form with a regular base centered on the axis of the spherical caps forming the photocathodes. According to its electrical connection mode, this assembly can, as explained above, form a deflector constituting a means for separating the channels or a first focusing accelerating electrode at the rate of one per channel. The assembly 40 is disposed immediately downstream of the photocathode 2. In the example shown in Figure 6, the deflector 40 is formed of two conductive walls 41 perpendicular to each other at the center of the tube and perpendicular to the internal plane. The deflector 40 is formed of conductive walls 41, for example metal, perpendicular to the inner plane preferably electrically interconnected. In this way the assembly 40 delimits an electronic corridor for each channel. This corridor ensures that the electrons from the photocathode portion deposited on one of the caps 8 will not be diverted to an adjacent channel corresponding to an adjacent cap when these walls form a deflector. It allows a strong acceleration of the photoelectrons when the walls are at a potential algebraically higher than that of the photocathode. This results in a lower transit time as well as smaller transit time gaps between photoelectrons from different points of the photocathode or having different initial velocity vectors from each other. The set of walls 40, the focusing optics 9 and the first stage 90 of dynodes 31 will now be described in more detail in relation with FIG. 3. The positions of the cylindrical walls 41, with respect to the window of transparency, correspond substantially to the thick parts 23 of the transparency window. These walls 41 have a first end 46 close to the photocathode 2 and a remote end 47. The end 46 near the photocathode 2 is sufficiently close to the inner face 7 of the transparency window 5 to delimit the photocathode areas 2 allocated to each channel.

Optics 9 will now be described. The optics 9 comprises as many individual optics 13 identical to each other as to channels, that is to say nine in the example shown in FIGS. 1 to 3 and four in the example shown in FIG.

Each individual optics 13 is constituted by an accelerating and focusing electrode 13. The references corresponding to the detailed description of one of the individual optics 13 are concentrated in FIG. 3 and distributed over different optics 13 so as not to overload the FIG. 3.

Each accelerating and focusing electrode 13 is constituted by a cylindrical conducting wall 91 with an axis perpendicular to the outer plane face 6 of the transparency window and by a wall 94 parallel to this outer face 6 of the transparency window 5. The wall 94 is internal and delimited by the cylindrical wall 91. Preferably and as shown in FIG. 1, the axis of the cylindrical wall 91 of the accelerating and focusing electrode 13 coincides with the axis of revolution of the cap 8, to which this electrode 13 corresponds . This cylindrical wall 91 has in the axial direction two ends, a first 92 close to the photocathode 2 and a second 93 remote from the photocathode 2. The first end 91 is defined by the intersection of the cylindrical wall 91 with a non-fictional plane. parallel to the plane face 6 of the transparency window 5 and secant to all the generatrices of the cylindrical wall 91. Thus, the first end 92 of the cylindrical wall 91 is in the form of an ellipse-shaped contour 92 when, as in the case represented in FIG. 3, the base of the cylinder forming the cylindrical wall is circular. It should be noted, however, that in this description the word "cylindrical" applied to the wall 91 is used in the mathematical sense of the term. This means in particular that the base of the cylinder could also be polygonal, for example square or hexagonal or octagonal. In these cases the cylindrical wall 91 is presented as a set of plane faces, two consecutive planar faces forming a dihedron. Each ellipse or more generally each line of intersection of the cylindrical wall with the imaginary plane not parallel to the flat face 6 of the window 5 has a major axis 96, in said fictitious plane. This major axis 96 shown in Figure 1, joins a point A of larger dimension in the axial direction of the cylindrical wall 91 to a point B of smaller size of this wall. The second end 93 is delimited by the intersection of the cylindrical wall 91 with a plane parallel to the flat face 6 of the transparency window 5. Thus, the second end 93 of the cylindrical wall 91 is in the form of a contour 93 in the form of circle.

The wall 94 parallel to the outer face of the transparency window is located at the second end 93 of the cylindrical wall 91. It is a plane wall 94 internal to the cylindrical wall 91. This flat wall 94 comprises a zone 95 of passage of electrons. In the example shown, this electron passage zone is a simple through hole. It could also be a large mesh grid composed for example of one or more fine threads. The electron passage zone 95 is closer to the large portion of the cylindrical wall 91 than to the small portion of said wall. In the example shown it is a hole 95 in the form of a circle having its center on an axis which is the projection, in a direction parallel to a direction perpendicular to the internal plane, of the major axis 96 of the ellipse forming the contour of the first end 92 of the cylindrical wall 91 on the plane of the plane wall 94. The circle delimiting the passage zone 95 is tangent or passes close to the generatrix of the cylindrical wall 91 passing through the point A corresponding to the largest dimension of the cylindrical wall 91. Its diameter is smaller than the diameter of the flat wall 94. The shape of each of the first dynodes 31 of the electron multiplier 30 of a multi-channel tube 1 according to the invention will now be described. What is said about the first dynodes 31 of the nine-way tube is applicable to the four-way tube shown in Figure 6 and generally to any multi-channel tube according to the invention.

The first dynodes 31 are all identical to each other. Each of the first dynodes 31 has the shape of a box whose lid is replaced by an opening. The box is open in the direction facing the photocathode 2. It has a bottom grid 39 of electron passage on the opposite side to the opening. The bottom grid 39 occupies almost all of a bottom wall 48. The box thus has a lateral surface and said bottom wall 48 carrying the bottom grid 39. The lateral surface is formed by the juxtaposition of four walls 32. 35. Three walls 32-34 are plane walls perpendicular to the flat face 6 of the transparency window. The first and second walls 32 and

34 are each respectively perpendicular to one end of the third wall 33. The fourth wall

35 which faces the third wall 33 has three planar portions 36-38, joined two by two. Each of the wall portions 36-38 is perpendicular to the first and second faces 32, 34. A first flat portion 36 is closest to the photocathode 2. This first flat portion 36 is perpendicular to the flat face 6 of the transparency window 5. A second flat portion 37 is joined with the first and forms with it a dihedral angle greater than 90 °. The third flat portion 38 is contiguous with the second and forms with it a dihedral angle greater than 90 °. The third flat portion 38 joins the second flat portion 37 and the bottom wall 48 carrying the bottom grid 39 of the dynode 31. The bottom grid 39 is parallel to the flat face 6 of the transparency window 5, and in a first direction extends substantially in a portion located between an axial plane of the cap 8 corresponding to the path of this first dynode 31 this plane comprising the minor axis of the ellipse forming the contour 92, and the third side wall 33. In a second direction perpendicular to the first, the grid 39 extends substantially between the first and second walls 32, 34. The second end of the third flat portion 38 of the fourth wall 35 is made with the plane containing the bottom grid 39 a angle between 145 and 180 °. Optionally, the fourth wall may, as represented in FIG. 1, have a fourth wall portion 49 extending the third portion 38 of this wall 35. This portion 49 has a first end joined to the third portion 38 and a free end, closer to the photocathode 2 as the first end. A particularly advantageous mode of realizing, on the one hand, all the individual optics 13 and, on the other hand, at least a portion of the first dynodes 31 will be described hereinafter with reference to FIG. 4. In the example shown in FIG. the individual optics 13 have the general shape described with reference to FIG. bases of the cylindrical walls 91 are, in this example, regular polygonal and more particularly in the example shown hexagonal.

To form the individual optics 13, a set of three plates a first 100 of the cylindrical wall portion 91, a second 200 also said cylindrical wall portion 91, and a third 300 bottom slots is used. On the first plate 100, a set of cuts and bends has been made. Only one of these bends and cuts will be commented below. The other cuts and folds are identical to the one that will be commented. There are as many as individual optics 13 to achieve, 9 in the example commented. The plates 100 and 200 each comprise 9 zones 110, 210, respectively, regular polygonal, square in the example shown. Polygons 110 and 210 are stackable as a whole. By this, we mean that the polygons 110 have the same dimension and the same relative dispositions as the polygons 210.

On the first plate 100, cutouts have been made which then allow a 90 ° bend of a part of the plate 100 initially belonging to the surface of the polygon 110. In FIG. 4 the references have only been worn on a limited number of folded parts. One side of the polygon 110 is referenced 111. This side 111 has three parts, a central portion 114, and two side portions 112, 113 located on either side of the central portion 114. The side portions 112 and 113 have a cutting line. The plate 100 is folded along the part central 114 to 90 ° of the initial plane of the plate 100. There is thus formed a portion 108 to 90 ° of the plane of the plate 100. This part comprises three parts, a central portion 102 and two side portions 104, 106 of the part. other of the central portion 102. The side portions 104 and 106 are based on the cut portions 112 and 113, or at least a portion of these cutouts, respectively. The central portion 102 is based on the central portion 114. The central portion 102 has a cutting shape such that it forms, after folding at 90 ° around the central portion 114, a portion 102 of cylindrical wall 91. It is specified here only part of the cylindrical wall portion 91 denotes a portion of this wall which is based on one of the sides of the polygonal base of the wall 91. It is also specified that a wall portion 91 may be formed of sub-parties for example, as will be seen below, two sub-parts overlapping partially to ensure the continuity of the game. In order to form at least a sub-portion of each of the other walls adjacent to the wall portion 91, the lateral portions 104 and 106 are folded around a fold axis perpendicular to the plane of the plate 100. In the same way the plate 100 is still cut and folded to form, as shown in FIG. 3, a wall 109. The wall 109 has a central portion 103 connected by a fold 115 to the plate 100. The wall 109 also has two lateral portions 105 and 107 at each from its ends. The lateral parts 105 and 107 are folded around a fold axis perpendicular to the plane of the plate 100. Once folded they form at least portions of cylindrical wall portion 91. Parts 102 and 103 of cylindrical wall 91 are not adjacent to each other. The folds 115 and 114 are on sides of the polygon 110 not adjacent to each other. They are likewise on sides of the polygonal base of the wall 91 not adjacent to each other.

On the second plate 200, cutouts have been made which then allow a 90 ° bend of a portion of the plate 200 initially belonging to the surface of the polygon 210. One side of the polygon 210 is referenced 211. This side 211 comprises three parts, a central portion 214, and two side portions 212, 213 located on either side of the central portion 214. The side portions 212 and 213 comprise a cutting line. The plate 200 is folded along the central portion 214 at 90 ° of the initial plane of the plate 200. There is thus formed a wall 208 at 90 ° of the plane of the plate 200. This part comprises three parts, a central portion 202 and two side portions 204, 206 on either side of the central portion 202. The side portions 204 and 206 are based on the cut portions 212 and 213 or at least a portion of these cutouts, respectively. The central portion 202 is based on the central portion 214. The central portion 202 has a cutting shape such that it forms, after folding at 90 ° around the central portion 214, one 202 of the wall portions 91 of each 13. In order to form at least one sub-part of each of the other walls adjacent to the wall 202, the lateral portions 204 and 206 are folded about an axis of bending perpendicular to the plane of the plate 200. In the same way, not apparent in Fig 3, the plate 200 is still cut and folded to form a wall 209. The wall 209 has a central portion 203 connected by a fold 215 to the plate 200. The wall 209 also has two lateral portions 205 and 207 at each of its ends. The side portions 205 and 207 are folded about a fold axis perpendicular to the plane of the plate 200. Once folded they form sub-portions of cylindrical wall portion 91. The walls 202 and 203 are not adjacent to each other. The folds 215 and 214 are on sides of the polygon 210 not adjacent to each other. They are likewise on sides of the polygonal base of the cylindrical wall 91 not adjacent to each other.

The assembly of the first and second plates 100 and 200 will now be commented on with reference to FIG. 5. The two plates 100, 200 are clipped to each other in a direction perpendicular to the plane of the plates. The assembly of the two plates 100 and 200 suddenly form all the wall portions 91 of each of the 9 focusing electrodes 13. Each vertical wall 91 is formed in the example here commented where the base of the cylindrical wall 91 is hexagonal, six parts of wall. The wall portions 102 and 103 are integrally formed from the first plate 100. The wall portions 202 and 203 are integrally formed from the second plate 200. Finally, the wall portions adjacent to one of the wall portions 102, 103, 202, 203 formed entirely from one of the Plates 100 or 200 only are formed of several sub-parts of walls. These sub-portions of walls 104, 205 which are adjacent respectively to the walls 102, 203 and sub-portions of walls 207, 105 which are adjacent respectively to the walls 203 and

103 formed entirely from one of the plates 200 or 100 only respectively. Specifically, wall portions of the polygonal cylindrical portion 91 located between two wall portions 91 formed from only one of the plates 100, 200 are formed of two sub-portions which preferably partially overlap each other. A first subpart is in one piece with one of the plates, a second subpart is integral with the other of these plates. For example, each wall portion 91 intermediate between the portions 102 and 203 of walls 91 is formed of a subpart 104 coming from the first plate 100.

104 is connected by a fold to the wall portion 91 entirely from the first plate 100, and a subpart 205 connected by a fold to the wall portion 203 entirely from second plate 200.

The third plate 300, said bottom plate, is housed under and in electrical contact with the cylindrical wall 91. It has cutouts 95 located so as to form the zones 95 for the passage of electrons. The uncut portions comprise on the one hand the portions 94 forming the bottom of the individual optics 13 and parts ensuring a continuum between the parts 94, so that the holes 95 and the funds 94 of the set of individual optics 13 are in one piece.

An advantageous embodiment of the stage 90 of first dynodes 31 will now be commented on with reference to FIG. 4. Each dynode 31 is obtained by cutting and folding a single conductive plate 400. In the example shown, the plate 400 is divided fictitiously into as many disjointed rectangular zones 410 as paths. Cutouts are made on three of the sides of each rectangular zone 410. It then becomes possible to bend a portion of the plate 400 within each rectangular zone 410 to form the wall 35 of each of the first dynodes. The walls 35 are thus each connected by a fold to the continuum of the plate 400.

After the first dynode, in the flow direction of the electrons, come the other dynodes of the electron multiplier. The multiplier 30 shown in FIG. 3 is formed by a stack of multiplier stages. Each stage of the stack of multiplier stages is formed by a focuser and a dynode. The focuser and the dynode are formed by conductive sheets parallel to the outer face 6 of the transparency window 5. The stack preferably comprises a gain control stage.

Reference can be made to the description of such a multiplier in the patent application FR 2 733 629. In the exemplary embodiment shown in FIG. 6, the multiplier is in the form of a focusing linear structure called Rajchman, with one structure per channel. Advantageously, this structure comprises a gain control stage.

In an optional embodiment which will now be commented on in connection with FIGS. 5 to 7, the anode or a gain control dynode is in the particularly advantageous form of a cassette 50 allowing simplified mounting of the tube 1. This The mounting is simplified by the fact that the conductive parts insulated relative to each other, are pre-assembled and held in position by insulating spacers. Moreover, it is thanks to this arrangement that the cassette can easily be inserted into the stage stack together forming the electron multiplier to form a gain control dynode. In addition, when the cassette is used as anode, it becomes easy to place said anode in the stack of stages multipliers between the penultimate floor and the last floor. This arrangement is advantageous because it makes it possible to obtain a high electric field between the last dynode and the anode and thus to reduce the effect of the space charge. It is often abandoned in the multi-channel tubes because of the mechanical difficulty to implant a large number of conductive parts electrically isolated from each other in the inter-synod space.

In the case of a gain adjustment dynode, this cassette is located between two multiplier stages or between a multiplier stage and the anode.

Figure 7 shows a top view of a machined plate 50 having a plurality of conductive portions 51, each provided with a connecting link 52, and a temporary holding member 53. The conductive parts 51 are intended to be inserted between two insulating spacers 61 and 62 shown in FIGS. 6 and 7, to form with them and means for assembling the spacers 61, 62 a cassette 60.

The conductive parts 51 are intended after insertion into a tube 1 to be electrically isolated from each other. The conductive parts 51 may have different configurations. In one embodiment where the cassette is used as a gain control dynode, the conductive portions 51 may take the form of a grid formed by wires mechanically secured to a frame. It can also be a plate with holes for the passage of electrons. When it is an anode, the conductive parts 51 can take the position of the anode in a tube, the shape of a plate having holes for the passage of electrons or a solid plate so as to collate the maximum of electrons. Each connection link 52 is intended to form part of a connection of a conductive parts 51 isolated to an external connection means, for example a pin 20 of a tube 1. Owing to the electrical independence of the conductive parts 51, it is possible either to apply a potential of their own, which will generally be the case for a gain control dynode, or to collect the signals resulting from the photonic activity on each of the channels in the case of the anode of collation of the signals. The exemplary cassette shown in FIGS. 5 to 7 corresponds to the example discussed with reference to FIGS. 1 to 3. As a result, the commented tube 1 comprises 9 channels. There are therefore nine conductive parts 51, and nine connection links 52. Each connection link 52 is electrically connected to a part 51 and to one. The set of conductive parts 51 intended after insertion into a tube 1 to be isolated from each other, is represented in FIG. 7 at an intermediate manufacturing stage in which each of the connection links 52 has a first end 54 mechanically secured to the conductive part 51 which it has the function of connecting, and has a second end 55 secured to a temporary holding part 53. In the example shown in Figures 5 and 6, the temporary holding part 53 is presented form of a frame 53 surrounding externally the connecting links 52 and the conductive parts 51. Thanks to this frame 53, the various conductive parts 51 are held mechanically integral with the same mechanical assembly formed by the machined plate 50. The machined plate 50 including frame 53, connecting links 52 and the different conductive parts 51 can thus be handled in one piece. The positions of the conductive parts 51 and their connection links 52 are fixed in a frame constituted by the frame 53. The shape of the machined plate 50 is obtained for example by electrochemical etching or by laser machining of a solid plate, having the starting a uniform thickness e between 0.1 and 0.5 mm. Such machining methods are in themselves known. After machining, thick parts are obtained, that is to say having the initial thickness of the electrochemically unmachined plate and parts of small thickness of thickness smaller than the initial thickness e. The machined plate 50 is inserted between two spacers 61, 62, a first 61 and a second 62, each made in one piece in an insulating material, for example a ceramic. An exploded perspective view of the insulating spacers 61, 62 and the machined plate 50 is shown in FIG. 8. A perspective view of an assembled cassette 60 formed by the assembly of the two plates 61, 62 and electrically insulated conductive parts 51. 5, each of the insulated conductive portions 51 is housed and positioned accurately in an opening 63 of at least one of the spacers. , for example the first 61. These openings were obtained by cutting into a solid wafer of constant thickness. When each of the parties electrically insulated conductors 51 provided with its connecting link 52 is positioned and fixed in position between the two spacers 61 and 62, the frame 53 of the machined plate 50 is cut. After cutting the frame 53, the anode assembly or gain control dynode has the appearance shown in Figure 9. The insulated conductive parts 51 and a portion of their connecting connection 52 are housed between the spacers 61 and 62. In the In the example shown, a portion 56 of each of the connecting links 52 protrudes from the cassette formed by the assembly of the two spacers and conductors.

When it is said that the conductive portion 51 is a thick portion, this does not exclude that this conductive portion 51 is constituted by a grid or a perforated solid plate as explained above. In this case, it is clear that the hole portions or the portions between the grid wires have a thickness of zero or no thickness at all. The peripheral portions 75 are holding portions of the conductive portion 51 on the edges 64 of the openings 63 receiving the parts 51.

The precise positioning of the conductive parts 51 is obtained by the fact that each part 51, and the connecting connection 52 which is its own, comprises thick portions 51, 67, 78 represented in dashed surface FIG. 7, and parts of FIG. 75. The thick parts 51, 67, 78 cooperate with openings 63, 87, 88 spacers 61, 62 in which they penetrate to position the conductive parts 51 and their connecting links. The thin portions are clamped between solid portions of the spacers 61, 62, which contributes to their holding in position. In the mounted position in the tube 1, the cassette 60 is positioned and held by columns 83 of the tube 1 (FIG. 1). Each column 83 passes through aligned openings 77 of the spacer 61, 71 of the machined part portion 50 no longer including the frame 53, and 73 of the spacer 62.

Claims

A multi-path photomultiplier tube (1) having a sealed envelope (4), the sealed envelope (4) having a photon-transparent window wall (5) and other walls (3,

10), the transparency window (5) having a plane outer face (6) and an inner face (7), an axial direction of the tube being a direction perpendicular to the plane outer face (6), the tube (1) comprising in order in the direction of the axial direction, a photocathode (2) in the form of a light-emitting layer disposed on the inner face (7) of the transparency window (5) so as to receive light photons having passed through the transparency window (5), a focusing optics (9) comprising for each channel one or more electrodes (13) accelerating and focusing distributing the electrons from the photocathode (2) in the different channels, and directing them to a first dynode (31) proper to each channel,

a stack (30) of multiplying stages, comprising, in the direction of travel of the electrons, a first stage (90) comprising first dynodes (31), and a stack of subsequent multiplying stages, including a penultimate stage and a last stage, an anode (60) formed by conductors (51, 52) insulated from each other by an insulated conductor for each multiplication channel, said anode (60) being in the direction of travel of the electrons, downstream of the last multiplier stage, connection means (20) passing through the sealed envelope and having external connection contacts (14) to the envelope (4), even connected to internal connection electrical connections, for connecting the dynodes, the photocathode (2), the electrodes (13) of the focusing optics (9), and the individual insulated conductors (51, 52) together forming the anode (60) at their respective operating voltage, characterized in that the transparency window (5) has a number of concavities (8) equal to the number of channels of the tube (1) these concavities (8) being in the form of of hollow portions (8) from the internal face (7) of the transparency window (5), each concavity (8) corresponding to a path, the wall comprising the transparency window (5) thus having hollow portions ( 8) and thick portions (23) corresponding to non-hollow portions, the surfaces of the hollow portions (8) being covered by the light-emitting layer (2) forming the photocathode (2), each hollow surface thus forming a photocathode area (2).

2. multi-way photomultiplier tube (1) according to claim 1 wherein one of the faces (6, 7) of the transparency window has ridges (21) located in the thick parts (23) of this window, these streaks (21) being filled by a reflective or absorbing photon product.

3. multi-way photomultiplier tube (1) according to one of claims 1 or 2 further comprising a set (40) of conductive walls (41) of cylindrical shape, perpendicular to the planar outer face (6) of the window of transparency (5), projections of these walls (41-44) in the axial direction lying on the thick portions (23) of the transparency window (5), this assembly (40) being located immediately downstream of the photocathode (2).

4. photomultiplier tube (1) with multiple channels according to one of claims 1 to 3 wherein each concavity (8) of the inner face (7) of the transparency window (5) is a cap (8) hemispherical, each circles (12) determined by the intersection between a plane parallel to the plane of the plane outer face (6) and said caps (8) being very close to two other of these circles (12) if it is a question of a corner portion of the transparency window (5), three other circles (12) if it is a peripheral portion of the transparency window (5) other than the corner portions and four other circles (12) if it is a circle (12) not occupying a peripheral position.

Multi-channel photomultiplier tube (1) according to one of Claims 1 to 4, in which the focusing optics (9) comprise a set of accelerating and focusing electrodes (13) at the rate of one electrode per channel. at least one or each accelerator and focusing electrode (13) comprising a cylindrical conducting wall (91) with an axis perpendicular to the planar outer face (6) of the transparency window (5), this cylindrical wall (91) having in the axial direction two ends (92, 93), a first (92) close to the photocathode (2) and a second (93) remote from the photocathode (2), the first end (92) being delimited by the intersection of the cylindrical wall

(91) with a plane not parallel to the plane outer face (6) of the transparency window (5) and secant to all the generatrices of said cylindrical wall (91) and the second end (93) being delimited by an intersection with a plane parallel to the plane outer face (6) of the transparency window (5), the cylindrical wall (91) thus having in the axial direction, a generatrix of maximum length and a generatrix of minimum length diametrically opposite one to the other and a plane wall (94) parallel to the outer face (6) of the transparent window (5), and internally connected to the cylindrical conducting wall (91) at its second end (93), this wall plane (94) having a zone (95) for passing electrons, this passage zone (95) being closer to the generatrix of maximum length of the cylindrical wall (91) than to the generator of minimum length of said cylindrical wall ( 91).

6. Multi-channel photomultiplier tube (1) according to one of claims 1 to 5 wherein the electrodes (13) accelerating and focusing of each path are identical to each other.

Multi-channel photomultiplier tube (1) according to one of Claims 5 or 6, in which each cylindrical wall (91) of a focusing electrode (13) has a polygonal base and comprises a set of parts (102, 103, 203, 202), at a rate of one part per side of the polygon forming the base of the cylindrical wall (91) and wherein portions (102, 103, 203, 202) of each of the cylindrical walls (91) are integral portions of a first plate (100, 200) of cylindrical wall portions (91), said portions being connected to said first plate (100, 200) by a fold (114, 115, 214, 215) .

The multi-channel photomultiplier tube (1) according to claim 7 wherein cylindrical wall portions (91) are integral parts of a second plate (100, 200) of cylindrical wall portions (91). , different from the first plate, these portions being connected to said second plate (100, 200) by a fold (214, 215).

The multi-channel photomultiplier tube (1) of claim 8 wherein portions

Cylindrical wall (91) have a first subpart (104, 106, 105, 107) connected by a fold with a portion

(102, 103) of cylindrical wall (91) integral with said first plate (100), and a second subpart (205, 207, 204, 206) connected by a fold with a portion (202, 203) cylindrical wall integral with said second plate (200).

10. multi-channel photomultiplier tube (1) according to one of claims 5 to 9 wherein the planar walls (94) having the passage zones

(95) electrons of each of the individual focusing electrodes (13) are formed integrally in a bottom plate (300) having as many passage areas (95) as channels. Multi-channel photomultiplier tube (1) according to one of Claims 5 to 10, in which a first dynode (31) of at least one of the channels comprises, in the axial direction, a first end close to the cathode and a distant second end. , each first dynode (31) having a face (35) located in a direction defined by the perpendicular to the outer face (6) of the transparency window (5), under the zone (95) of passage of the electrons through the accelerating and focusing electrode (13).

11. Multi-channel photomultiplier tube (1) according to one of claims 1 to 10 wherein, an electron receiving face (35) of each of the first dynodes (31) of the stage (90) of first dynodes (31), said electron-receiving face (35) being located in a direction defined by the perpendicular to the outer face (6) of the transparency window (5), under a zone (95) of passage of electrons to through the accelerating and focusing electrode (13) is formed in one piece in a plate (400) of first dynodes (31), each face

(35) receiving electronically being foldably connected to the continuum of said first dynode plate (400).

The multi-way photomultiplier tube (1) according to claim 11, wherein a first dynode (31) of each channel is constituted by a set of conductive walls (32-35, 39) forming together a box without a lid whose lid is replaced by an opening on the side of its first end, the set of walls (32-35, 39) having first to third walls (32-34) planes perpendicular to the outer face (6) of the transparency window (5), the first and second walls (32, 34) being parallel to each other and perpendicular to ends of the third wall

(33), these first and second walls (32, 34) having in a direction perpendicular to the third wall (33) a greater length at the first end of the box than at the second end, a fourth wall (35) facing the third wall (33) having its first end (36) perpendicular to the outer face (6) of the transparency window (5) and having a concavity facing the photocathode (2) this fourth wall ( 35) being perpendicular to the first and second walls (32, 34).

Multi-channel photomultiplier tube (1) according to one of Claims 1 to 12, in which each stage of the stack (30) of multiplying stages, with the exception of the first stage, is formed by a focusser and a dynode. the focusing and the dynode being formed by conductive sheets parallel to the outer face (6) of the transparency window (5).

A multi-channel photomultiplier tube (1) according to one of claims 1 to 13 wherein the anode or a gain control stage comprises an assembled cassette (60) having a plurality of conductive, isolated portions (51). electrically from each other, each conductive portion (51) being further provided with a connection connection (52) integral therewith in one piece with the conductive portion (51) to which the link (52) is connected ,

first and second insulating spacers (61, 62), at least one of the spacers (61, 62) having apertures (63) through which each of the conductive portions (51) is exposed,

- Each of the conductive parts (51) and at least a portion of the connecting connection (52) corresponding thereto being housed between the first and the second spacer (61, 62).

The multichannel photomultiplier tube (1) according to claim 14, wherein the conductive portions (51) of the anode or the gain control stage and their connecting links (52) have portions having a small thickness. and portions (51, 67, 78) having a greater thickness greater than that of the thin portions, at least a portion of the thick portions (51, 67, 78) constituting part of the first positioning means of the parts (51) electrically isolated from each other, a complementary part of these first positioning means being constituted by openings (63, 87, 88) or niches (88) of one or the other of the spacers (61, 62) housing thick portions (51, 67, 78).