EP3044804B1

EP3044804B1 - Device to detect particles and corresponding detection method

Info

Publication number: EP3044804B1
Application number: EP14790331.4A
Authority: EP
Inventors: Giuseppe CAUTERO; Paolo PITTANA; Rudi SERGO
Original assignee: Elettra Sincrotrone Trieste Consortile Per Azioni Soc
Current assignee: Elettra Sincrotrone Trieste Consortile Per Azioni Soc
Priority date: 2013-09-11
Filing date: 2014-09-10
Publication date: 2017-11-08
Anticipated expiration: 2034-09-10
Also published as: WO2015036918A1; ITUD20130118A1; ES2659339T3; PL3044804T3; EP3044804A1

Description

FIELD OF THE INVENTION

The present invention concerns a device to detect particles installable in a detection apparatus, such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer (TOF), or ARTOF, or other apparatus used to guide, deflect, or focus particles and used to study matter in its various aggregated states: solid, liquid and gas.
Here and hereafter in the description, the term particles shall comprise electrons, ions or other electrically neutral or charged particles, or photons.
The present invention also concerns the method to detect particles.

BACKGROUND OF THE INVENTION

Apparatuses are known for detecting particles, for example but not only electronic electrostatic deflection analyzers such as apparatuses for the production of synchrotron light.
In particular, such detection apparatuses generally comprise a chamber put in a condition of ultra high vacuum, also known as UHV, in which a bundle of particles is generated, the behavior of which is analyzed by detection devices.
The detection devices are generally associated with one of the walls of the chamber using flanges, generating an interface between the inside of the chamber and the outside.
It is also known to associate to the detection devices, in the internal side of the chamber, electron amplification devices or charge multipliers, configured to amplify the particle signal.
Electron amplification devices are able to produce, for each individual particle, impulses of 10³ - 10⁸ electrons temporally comprised in fractions or in a few nanoseconds, through avalanche multiplication processes.
Among amplification devices, Microchannel Plates (MCP) are known, which comprise a set of miniaturized electron amplifiers disposed parallel to each other.
The impulses produced by the amplification devices are exploited by the detection devices to count, decode the position and possibly the arrival time of the particles that are to be detected in different ways.
Different ways are known in this field for detecting the impulses produced by amplification devices.
A multi-channel detection mode is known, for example, by means of which the impulses are transferred by one or more anodes, taken into air from vacuum through suitable feedthroughs and then amplified and discriminated before being digitally processed. The position where the particle arrives is indicated by the position of the anode itself and the resolution depends on the sizes of the anodes. The number of connectors for carrying the information from vacuum to air is equal to the number of anodes that make up the detector and is technologically limited to a couple of dozens.
An optical type detection mode is also known, for example described in document US-A-2011/095177 , based on Charge-Coupled Devices, also known as CCD, which consist of an integrated circuit formed by a line or a grid of semiconductor elements able to accumulate an electric charge proportional to the intensity of the electromagnetic radiation striking them. In this case the amplification device or MCP is mounted on a window attached to the chamber in a UHV seal.
On the window, on the side of the chamber, a layer of phosphorus is deposited, kept at very high positive tension (some kVolts) with respect to the MCP. In this way, when the impulses produced are accelerated toward the phosphorus, they produce an illumination proportional to the charge emitted by the MCP.
A CCD camera, disposed outside the chamber, translates this illumination into information on the quantity of electrons that have arrived, also supplying information on their position (two-dimensional acquisition). The spatial resolution is determined by the resolution of the CCD camera and by how much the phosphorus "spreads" the charge following the arrival of the impulse (blurring effect).
A layer of conductive material, for example aluminum, is deposited on the layer of phosphorus, in any case having a resistance of less than 1Ω/sq, and which allows to discharge the charge generated following the impact against the layer of phosphorus.
Detection devices are also known, based on the so-called "centroid finding" systems, among which one of the best known methods is the one based on "cross delay anodes". A solution based on this type of detection is described for example in WO-A-2011/109311 .
In this case the charge exiting from the MCP amplification devices induces electromagnetic impulses that are propagated on one or two (in this case one orthogonal to the other) delay lines made of conductive material - located at a few millimeters from the MCPs and deposited directly on ceramic material or in the form of wires, and disposed during use inside the analysis chamber.
Once they have arrived at the 4 heads of the two delay lines, the impulses are taken to air by means of feedthroughs, amplified and discriminated. From the measurement of the time that passes between the arrival of one impulse on one head and one impulse on the other head (of each of the two lines) the temporal information is extracted, as well as the spatial information, concerning the arrival of the particle.
The more precise the measurement of the arrival time, the more accurate the decoding of the position. In these cases it is important to preserve the form of the starting impulse since it is by identifying its centroid that the precise information on its position is derived, whereas on the contrary the size of the anodes is somewhat less relevant. The number of connectors (air - vacuum) needed for this three-dimensional information (2D plus time) is equal to 4.
WO-A-2011/109311 also describes a form of embodiment in which the particles are detected by means of a detection device of the delay-line type, located outside the analysis chamber.
The device consists of a layer of resistive material deposited on the external side of a substrate, made of glass or ceramic, which is attached to a wall of the analysis chamber and which replaces the layer of phosphorus normally used.
The layer of resistive material constitutes the anodes for detecting the particles. However, this solution does not allow to effect alternatively both optical and electronic acquisitions.
For all the reasons set forth above, it is obvious that the detection modes described above have little in common with each other, so that passing from one detection mode to another is extremely costly, not only in temporal terms but also due to the necessary mechanical workings of adaptation and the need to "break" the vacuum in the chamber. Interrupting the vacuum condition in the chamber is practically unacceptable in the framework of an experiment.
Moreover, the limit of using a single detector is connected to the purchase of the particular electronic analyzer or other instrument.
A device to detect particles is also known from US-A-5.969.361 , which allows both optical and electronic acquisition. In this detection device, a substrate which constitutes the interposition element between the analysis chamber and the outside is attached to the wall of the analysis chamber.
On the interposition element, made of transparent material, and on the side that faces the inside of the analysis chamber during use, a layer of conductive material is first deposited, which constitutes one or more anodes for detecting particles; above this, a layer of luminescent material is deposited. A plurality of feedthroughs from the analysis chamber toward the outside is provided to connect the anodes with an electronic system to detect the particles. This makes the device particularly complex since the feedthroughs must be suitably designed to guarantee the vacuum condition in the analysis chamber.
An optical acquisition device is attached outside the analysis chamber to detect the particles that impact on the luminescent layer.
The particle, impacting on the luminescent layer and the layer of conductive material, determines both a luminous emission that is detected by the optical acquisition device and also a charge impulse that is detected by the electronic detection system connected to the anode.
This solution is not reliable, however, and does not allow to make accurate and precise detections, since it does not allow to maximize the performances of the two types of acquisition, but is a compromise between the two.
Furthermore, due to the fact that the anodes are located inside the analysis chamber, it is particularly complicated to replace this type of anodes with others, for example to pass from a resistive anode detection to a multi-anode detection. In this case, the analysis chamber should be put in ambient conditions, the detection device dismantled, replaced by another and the analysis chamber should be returned to a vacuum condition.
Furthermore, this solution cannot be used for the implementation of cross delay anode detections, which in the field of anode detection is the most effective in terms of performance. The presence of the layer of conductive material, in fact, would make the charge generated by the impact of the particles degenerate very quickly, so much so that they would not then be able to be detected by cross delay anode systems.
From an experimental point of view, the problem is even bigger because each of the methods described for acquisition has advantages and disadvantages, which make it necessary to adopt one type of detection or the other within the framework of the same experiment.
One purpose of the present invention is to obtain a detection device of particles which allows, on the same detection apparatus (analyzer, TOF, ARTOF etc.) to adopt different detection modes without needing to put the chamber in atmospheric conditions or to perform complex mechanical workings under vacuum.
Another purpose of the present invention is to obtain a detection device that allows to simplify and reduce the operations needed to adopt one detection method rather than another.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.
In accordance with the above purposes, a device to detect particles comprises a support body attachable in correspondence to an aperture provided in a wall of an analysis chamber for a detection apparatus, such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer. The support body is configured to support at least an interposition element made of an electrically insulating material and transparent to visible light, and configured to close the analysis chamber.
According to one feature of the present invention, on the interposition element, on the side that during use faces inside the analysis chamber, a luminescent layer is disposed, configured to illuminate when in contact with a particle and, above the luminescent layer, a resistive layer is disposed with an ohmic resistance comprised between 1kΩ/sq and 50MΩ/sq.
Here and hereafter in the description and the claims, the term luminescent shall be taken to mean a layer that illuminates when a charge impulse arrives. Merely by way of example, the luminescent layer can illuminate due to the effect of fluorescence and phosphorescence, although other methods of illumination on the arrival of a charge impulse are not excluded.
The application on the interposition element of a luminescent layer and a resistive layer having the above properties allows to carry out both optical acquisitions, detecting the luminous emission emitted by the luminescent layer, and also anode acquisitions, detecting an electromagnetic impulse generated by the particles, and possibly first amplified by a charge amplifier element.
Passing through the interposition element, the luminous emission can be detected by an image acquisition device which is located outside the analysis chamber.
On the contrary the charge impulse generated by the impact of the particle against the resistive layer is transferred, due to a capacitive effect, through the interposition element. A detector associated outside the analysis chamber, and in direct contact with the interposition element, allows to detect the charge impulse arriving through the latter.
The choice of the particular resistive layer, with the values of ohmic resistance shown above, allows the charge generated on the luminescent layer not to disperse rapidly on its surface, and to remain confined at the point of impact of the particle for the time needed for detection, for example by cross delay lines. In this way the charge impulse is transferred, without distortions or attenuations of the signal, through the interposition element so as to be able to be easily detected by the detectors. The interposition element also guarantees the seal of the vacuum inside the analysis chamber, and allows direct optical acquisition by acquisition devices that can be disposed outside the analysis chamber.
With the device according to the present invention it is therefore possible to carry out detections of particles with different methods without requiring to replace the detection device or to interrupt the vacuum in the analysis chamber. With regard to anode detections, for example, it is enough to replace one detector with one of another type, simply by replacing the detector itself and disposing the other in direct contact with the interposition element on the external side of the analysis chamber. It is no longer required to take the analysis chamber to ambient conditions. If a detection of images is required, on the contrary, it will be sufficient to remove the detector and dispose, outside the analysis chamber and facing the interposition element, an image acquisition device to detect the luminous emissions that pass through the interposition element.
Some forms of embodiment of the present invention also concern a method to detect particles in a detection apparatus, such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer, which provides to accelerate the particles against an interposition element made of an electrically insulating material, transparent to visible light and associated to a support body. The support body is attached in correspondence to an aperture provided in a wall of an analysis chamber of the detection apparatus.
In some solutions of the method according to the present invention, the particles accelerated against the interposition element impact first on a resistive layer having an ohmic resistance comprised between 1kΩ/sq and 50MΩ/sq and then on a luminescent layer, polarized and deposited on the interposition element, producing a luminous emission and an impulse of an electromagnetic character. The luminous emission and, by capacitive effect, the impulse, pass through the interposition element. At least one of either the luminous emission or the impulse are detected outside the analysis chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some forms of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

fig. 1 is a schematic representation of a particle detection device according to one form of embodiment of the present invention;
fig. 2 is an enlarged detail of a part of the device according to the present invention according to a possible form of embodiment;
fig. 3 is an exploded view of a detection device according to the present invention according to another form of embodiment of the present invention;
fig. 4 is a schematic representation of a detection device associated to an optical acquisition device according to some forms of embodiment of the invention;
fig. 5 is a schematic representation of the functioning principle of the detection device in fig. 4;
figs. 6 and 7 are schematic representations of a detection device according to the present invention according to possible forms of embodiment.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF SOME FORMS OF EMBODIMENT

According to some forms of embodiment, shown merely by way of example in figs. 1-3, a detection device 10 according to the present invention can be installed in a detection apparatus 11, only partly shown in the drawings, to detect particles such as electrons, ions or photons.
In some forms of embodiment of the present invention, the detection apparatus 11 can be an electronic electrostatic deflection analyzer or a time-of-flight analyzer (TOF), or ARTOF, or other apparatus used to guide, deflect, or focus particles.
The detection apparatus 11 comprises an analysis chamber 13 which during use is put in a vacuum condition, and in which the particles, indicated in fig. 1 by the arrow C, are made to transit, and possibly accelerated against the detection device 10 to be detected.
In the form of embodiment shown in fig. 1, the detection device 10 comprises a support body 14 installed in correspondence with a through aperture 15 made in a wall 12 of the detection apparatus 11.
The wall 12 defines at least part of the analysis chamber 13 which, during use, is put in a vacuum condition.
Merely by way of example, the analysis chamber 13 is put at about 10^-5 - 10^-12 mbar, although higher pressure values are not excluded, in the range of 10^-3 mbar, using inert gases for example. The vacuum condition in the analysis chamber 13 is necessary both for experimental reasons and also for the charge multiplication instruments, or MCPs, which cannot function for pressures above 10^-5 mbar.
The support body 14 is attachable to the wall 12 of the analysis chamber 13 by substantially known connection means, not shown in the drawings.
Possible implementations of the present invention can provide that the connection means are chosen from a group comprising threaded connections, snap-in connections, same-shape coupling connections, geometric coupling connections, or similar or comparable means suitable for the purpose.
The support body 14 is configured to support at least an interposition element 16 made of an electrically insulating material and transparent to visible light. The interposition element 16 functions as an intermediate mean between the analysis chamber 13, in which the particles C transit, and means to detect/acquire the particles C located outside the analysis chamber 13.
The interposition element 16 is configured to close the analysis chamber 13 and guarantee inside it a sealed vacuum condition.
According to some forms of embodiment of the present invention, the interposition element 16 is made of quartz.
According to one possible form of embodiment, the interposition element 16 is made of BK07 type quartz.
Possible solutions of the present invention provide that the interposition element 16 has a thickness S (fig. 2) comprised between 1mm and 5mm, preferably between 2.5mm and 4mm, even more preferably about 3mm.
Possible forms of embodiment can provide that the interposition element 16 has a diameter of about 100mm and a thickness of about 3mm.
It is clear, however, that in other forms of embodiment, the thickness of the interposition element 16 can be chosen so as to guarantee the seal of the ultra high vacuum and is as thin as the material of which it is made allows.
In possible forms of embodiment the interposition element 16 is substantially flat and comprises a first surface 17, internal during use, and a second surface 18, external during use with respect to the analysis chamber 13.
According to some forms of embodiment of the present invention, on the first surface 17 of the interposition element 16 a luminescent layer 20 is disposed, configured to illuminate, for example due to the effect of fluorescence, if particles C impact against it.
According to possible solutions, the luminescent layer 20 is made of materials such as standard phosphorus, also known as "Standard Phosphor Type".
According to one form of embodiment, the luminescent layer 20 is chosen from a group comprising P43 (Gd2O2S:Tb), P46 (Y3Al5O12:Ce), P47 (Y2SiO5:Ce,Tb), P20 (Zn, Cd,S:Ag), P11 (ZnS:Ag).
According to a possible solution, the luminescent layer 20 is determined by several depositions of material until a maximum thickness of 500 micron is obtained.
According to a possible solution, possibly combinable with the forms of embodiment described here, the luminescent layer 20 comprises a mixture of phosphorus and glue configured to keep the mixture of phosphorus adherent to the interposition element 16, compatibly with the condition of high vacuum that is generated in the analysis chamber 13.
According to possible solutions, the luminescent layer 20 is connected to electronic devices, not shown in the drawings, which are electrically powered to polarize the luminescent layer 20 and attract the particles C against it.
According to one possible form of embodiment of the present invention, on the luminescent layer 20, on the side that during use faces toward the inside of the analysis chamber 13, a resistive layer 21 is disposed, with an ohmic resistance comprised between 1kΩ/sq and 50MΩ/sq, preferably between 10kΩ/sq and 10MΩ/sq.
According to a possible form of embodiment of the present invention, the resistive layer has an ohmic resistance comprised between 5MΩ/sq and 6MΩ/sq. In fact, Applicant has verified that this range of values allows to obtain optimum reliability and accuracy of the acquisitions/detections.
The resistance values indicated above refer to the unit of surface considered.
Adopting this ohmic resistance value allows to use the detection device 10 according to the present invention not only for the direct acquisition of images, for example by means of an optical acquisition device based on CCD technology, but also for detections of the electronic type such as the application of anode detectors such as a cross delay line detector, a multi-anode detector or a resistive anode detector.
This choice of the ohmic resistance indicated above guarantees that the electromagnetic impulse that is generated by a particle does not spread instantaneously over the whole surface as would happen if the layer were made of an electrically conductive material, for example a metal material; an instantaneous propagation of the impulse would render the detection device 10 unusable with a decoding mode based on delay lines.
The value of ohmic resistance of the resistive layer 21, moreover, must be such as to allow to discharge the accumulated charges, otherwise the layer would become electrically charged and the subsequent charge impulses would find an increasingly defecting field. At the same time the resistivity of the resistive layer 21 must be high enough to guarantee that the charge arriving is not immediately propagated over the whole luminescent layer 20, which would prejudice the impulsive nature thereof and render the detection impossible through capacitive coupling.
According to possible forms of embodiment of the present invention, the resistive layer 21 also has reflecting optical properties to improve the efficiency of the material that illuminates when the particles impact against it.
Some solutions of the present invention provide that the resistive layer 21 can be polarized at least up to 2 kVolts without any discharges occurring to mass, that is, through the support body 14.
According to possible solutions, the resistive layer 21 is made of a semi-conductive material.
According to possible forms of embodiment, the resistive layer 21 is made of a material chosen from a group consisting of germanium and graphite.
However, it cannot be excluded that in other forms of embodiment, other materials can be adopted which meet the requirements indicated above.
Possible implementations of the invention can provide that the resistive layer 21 has a thickness comprised between 30µm and 200nm. In particular, the thickness of the resistive layer 21 is chosen as a function of the material used and to reach a value of resistivity as indicated above.
The electrically insulating material that the interposition element 16 is made of allows to electrically insulate the high voltage present on the luminescent layer 20 on the side of the interposition element 16 located in air.
According to possible forms of embodiment of the present invention a charge amplification element 22 is associated with the support body 14, and is disposed adjacent to the luminescent layer 20 and configured to amplify the signal of the particles.
According to possible solutions of the present invention, the charge amplification element 22 can be a Micro Channel Plate (MCP), although it is not excluded that in other forms of embodiment it may be a different device suitable for the purpose such as a Gas Electron Multiplier (GEM), or a Micro Compteur à Trous (MicroCAT), or analogous devices generally indicated as gas micropattern avalanche detectors, which use gas to effect multiplication and are able to produce a charge impulse detectable following the arrival of a single particle.
Between the luminescent layer 20 and the charge amplification element 22 an interspace 23 can be provided, with distance D. By way of example, the distance D can vary from 1mm to 15mm.
In a possible solution, the charge amplification element 22 can be distanced from the interposition element 16 by means of a spacer 24.
The spacer 24 can be the fixed type, for example a ring, or the adjustable type so as to be able to vary the distance D as a function of the acquisitions to be made.
Possible forms of embodiment can provide that the charge amplification element 22 is mounted on the support body 14 by means of a holding element 25 such as a threaded ring, attachment brackets, threaded elements.
With reference to fig. 1, the holding element 25 comprises a ring nut even though other types of holding are not excluded, such as a glued attachment.
When the detection apparatus 11 is functioning (see figs. 4 and 5), the luminescent layer 20 is polarized to accelerate the impulses produced by the charge amplification element 22. The charge amplification element 22 emits charge impulses P containing from 10³ to about 10⁸ electrons for every particle C that hits them.
The amplified charge impulse determined by amplification, also thanks to the high polarization to which the latter is subjected during use, which increases the kinetic energy, hitting against the luminescent layer 20 produces a luminous emission L.
If an image acquisition is to be performed, on the external side of the interposition element 16, transparent for visible light, that is, facing its second surface 18, an image acquisition device 26 can be provided, configured to acquire images of the luminous emission L and to evaluate at least its degree of illumination and the position of impact of the particle C.
In possible forms of embodiment, the image acquisition device 26 can be the type based on Charge-Coupled Device (CCD) technology.
The detection device 10 according to the present invention can also be adopted with other methods for detecting particles, without modifying the architecture or main structure of the detection device 10, or without requiring the interruption of the vacuum in the analysis chamber 13.
In fact, thanks to the properties described above of the interposition element 16, the impulses P generated by the charge amplification element 22 can be transmitted through the interposition element 16 by means of capacitive coupling, so as to allow them to be detected by electronic acquisition techniques located in air. To this purpose, the thickness of the interposition element 16 must also be chosen so as to guarantee that the impulse P as it propagates in the thickness S of the interposition element 16 arrives distributed over an area in the order of mm². This allows to use the usual decoding techniques for particle analysis, for example techniques based on "centroid finding".
In order to execute detection methods using anode techniques, an anode type detector 27 can be associated with the support body 14. In particular, the detector 27 is associated with the interposition element 16 on the opposite side with respect to that where there is the luminescent layer 20, and therefore outside the analysis chamber 13.
This condition allows to easily replace the anode type detector 27 with another, for example because it is required by the specific analysis requested, without needing to interrupt the vacuum condition inside the analysis chamber 13.
The detector 27 is provided with at least one detector element 28, in this case a plurality of detector elements 28, which during use are in direct contact with the second surface 18 of the interposition element 16. In this way the impulse P transmitted capacitively through the interposition element 16 is detected directly by the detector elements 28.
With reference to fig. 6, the detector elements 28 comprise an electrode of the cross delay line type, connected to a plurality of signal transmission wires 29. The wires are in turn connected to a general detection apparatus.
With reference to fig. 7, the detector elements 28 comprise a plurality of electrodes disposed in a multi-anode configuration, each of which is connected to respective signal transmission wires 29 which are in turn connected to a general detection apparatus.
Other forms of embodiment can provide that the detector elements 28 comprise one or more resistive anodes.
The detector elements 28 can be disposed on a support plate 30 through which the connections 31 for the wires 29 are then made.
The detector elements 28 can be disposed on the support plate 30 for example using cathode deposition techniques.
The support plate 30 is disposed in use with the detector elements 28 in contact against the second surface 18 of the interposition element 16.
The contact surfaces between the support plate 30 and the second surface 18 of the interposition element 16 are substantially flat so that they can couple reciprocally resting one against the other.
The support plate 30 can be mounted on a support element 32 attachable to the support body 14 for example by threaded connections or other types of coupling.
Thanks to this simple mechanism of the detector 27, removable and completely in-air, it is possible to replace one type for another, so as to change acquisition modes without needing complex interventions on the analysis chamber 13.
If an optical analysis is required, moreover, it is possible to remove the detector 27 quickly to position the image acquisition device 26.
In possible forms of embodiment, the support body 14 can be provided with vacuum - air feedthroughs 33 which extend from the support body 14 to the interposition element 16.
The vacuum - air feedthroughs 33 can be configured to take power to the luminescent layer 20 for example, guaranteeing the seal of the ultra high vacuum of the analysis chamber 13.
We shall now describe a method for making the detection device 10, and in particular the steps for making the luminescent layer 20 and the resistive layer 21.
To make the luminescent layer 20 a mixture of three elements is made: isopropyl alcohol, a glue compatible with vacuum or ultra high vacuum (depending on the requirements of the experiment) and luminescent material in powder. The alcohol and the glue, although not fundamental for the luminescence process, are useful for achieving the characteristics of adhesion and uniformity needed for the successful deposition. In the following example, P 47 (Y2SiO5:Ce,Tb) will be used as luminescent material, but the same process is also valid for other Phosphor Standard Types. The ratio between the three elements is 1:1:1.
The mixture is left to drip onto the first surface 17 of the interposition element 16 and, using a spinner for example, a uniform layer is generated with a thickness of some hundred microns.
Then the isopropyl alcohol is left to evaporate. Once it has dried, the luminescent layer 20 appears as a white and uniform film, electrically insulating. At this point the resistive layer 21 can be deposited.
We shall now describe making a resistive layer of graphite. We begin with graphite in a colloidal suspension (available on the market) mixed with isopropyl alcohol, and the mixture is poured on the luminescent layer 20. The thickness of the resistive layer 21 is made uniform by using a spinner, a spatula or other similar or comparable device. Although the alcohol is not necessary, it can be observed that, thanks to the presence of the alcohol, it is simpler to deposit a mixture that reaches (once the alcohol has evaporated) a surface resistance that comes within the values of ohmic resistance previously specified. The thickness of the resistive layer deposited is in the order of hundreds of nanometers, corresponding - in the case of graphite - to a few MΩ/sq. Other thicknesses and other values of resistivity can be obtained by using different deposition methods (alternative to the spinner, which usually give greater thicknesses) or different ratios in the alcohol-graphite mixture. Whatever the method, what counts is the ohmic resistance identified above.
It is clear that modifications and/or additions of parts may be made to the particle detection device 10 and corresponding detection method as described heretofore, without departing from the field and scope of the present invention.
It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of particle detection device 10 and detection method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

Device to detect particles comprising a support body (14) attachable in correspondence to an aperture (15) provided in a wall (12) of an analysis chamber (13) for a detection apparatus (11), such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer, said support body (14) being configured to support at least an interposition element (16) made of an electrically insulating material and transparent to visible light, and configured to close said analysis chamber (13), wherein on said interposition element (16), on the side that during use faces inside said analysis chamber (13), a luminescent layer (20) is disposed configured to illuminate when in contact with a particle and, on top of said luminescent layer (20) a resistive layer (21) is deposited, said luminescent layer (20) being made of Standard Phosphor Type materials, characterized in that said resistive layer is deposited with an ohmic resistance comprised between 1kΩ/sq and 50MΩ/sq, and said resistive layer (21) being made of semi-conductive material.
Device as in claim 1, characterized in that said resistive layer (21) is made of a material chosen from a group consisting of germanium and graphite.
Device as in any claim hereinbefore, characterized in that said resistive layer (21) has a thickness comprised between 30µm and 200nm.
Device as in any claim hereinbefore, characterized in that said resistive layer (21) has reflecting optical properties.
Device as in any claim hereinbefore, characterized in that said interposition element (16) is made of quartz.
Device as in any claim hereinbefore, characterized in that said interposition element (16) has a thickness (S) comprised between 1mm and 5mm, preferably between 2.5mm and 4mm, even more preferably about 3mm.
Device as in any claim hereinbefore, characterized in that it comprises a charge amplification element (22) disposed facing said luminescent layer (20) and said resistive layer (21) and configured to amplify the signal of said particles (C) before their impact on the latter.
Device as in claim 7, characterized in that said charge amplification element (22) is chosen from a group comprising Microchannel Plates, a Gas Electron Multiplier or a Micro Compteur à Trous, or other devices suitable to produce a detectable charge impulse.
Device as in any claim hereinbefore, characterized in that if an electronic-type detection of said particles is carried out, it comprises a detector (27) of the anode type associated to said interposition element (16), on the opposite side with respect to that where there is the luminescent layer (20), outside said analysis chamber (13), and configured to detect impulses (P) of an electromagnetic character generated by said particles.
Device as in claim 9, characterized in that said detector (27) is provided with at least a detector element (28) put in direct contact with said interposition element (16).
Device as in claim 10, characterized in that said detector element (28) is chosen from a group consisting of cross delay line electrodes, multi-anode electrodes and resistive anodes.
Device as in any claim hereinbefore, characterized in that if an optical acquisition of said particles is carried out, it comprises an image acquisition device (26) provided on the side, external during use, of the interposition element (16).
Apparatus to detect particles such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer, comprising at least an analysis chamber (13) put, during use, in a vacuum condition and in which particles (C) are made to transit, and at least a detection device (10) as in any claim hereinbefore, said detection device (10) being attached to at least one wall (12) of said analysis chamber (13) in correspondence to a through aperture (15) thereof.
Method to detect particles in a detection apparatus (11), such as an electronic electrostatic deflection analyzer or a time-of-flight analyzer, which provides to accelerate said particles against an interposition element (16) made of an electrically insulating material, transparent to visible light and associated to a support body (14), said support body (14) being attached in correspondence to an aperture (15) provided in a wall (12) of an analysis chamber (13) of said detection apparatus (11), wherein said particles, accelerated against said interposition element (16), impact first on a resistive layer (21), made of semi-conductive material and having an ohmic resistance comprised between 1kΩ/sq and 50MΩ/sq, and then on a luminescent layer (20), polarized, deposited on said interposition element (16) and made of Standard Phosphor Type materials, in that said particles produce a luminous emission (L) and an impulse (P) of an electromagnetic character, in that said luminous emission (L) and, by capacitive effect, said impulse (P), pass through said interposition element (16), and in that at least one of either said luminous emission (L) or said impulse (P) are detected outside said analysis chamber (13).