Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
  • G01T1/2914—Measurement of spatial distribution of radiation
  • G01T1/2921—Static instruments for imaging the distribution of radioactivity in one or two dimensions; Radio-isotope cameras
  • G01T1/2928—Static instruments for imaging the distribution of radioactivity in one or two dimensions; Radio-isotope cameras using solid state detectors

Definitions

• the present invention relates to a device for detecting a radiation of particles or electromagnetic waves.
• a device for detecting a radiation of particles or electromagnetic waves is commonly implemented, first of all, for the primary purpose of detecting this type of wave or particle, for scientific purposes in particular, and then for forming images of certain parts of an object to be from rays transmitted through or diffracted or reflected by this object after irradiation, for example to analyze the chemical composition of this object.
• a two-dimensional detection device generally of the matrix type.
• the detection device or detector is conventionally registered or contained in a plan.
• the actual detection is carried out by means of juxtaposed elementary sensors contained in said plane and interacting with the radiation to be detected.
• detectors for digitizing the formed images, i.e. encoding them into a sequence of computer bits.
• Each elementary sensor of such a detector has traditionally the shape of a parallelepiped.
• Each elementary sensor is made of a semiconductor material.
• each elementary sensor is provided with an anode attached to one of its faces and a cathode attached to the face opposite to that carrying the anode. This anode and this cathode are brought to a suitable potential to collect the electrical signals generated by the elementary sensor as a result of its interaction with an electromagnetic wave or a particle.
• this type of detector is often referred to as a matrix detector.
• the elementary sensor can also be defined spatially only by the geometry of its anode and / or its cathode. In this case, all the sensors assembled to form a matrix detector have a common detector material constituting a single block of the size of the detector.
• Each elementary sensor of the matrix detector converts the incident ray, electromagnetic waves, or particles into electrical signals of intensity - a function of the energy of the incident ray. In known manner, these signals are transmitted to the electrodes, anodes and cathodes of the elementary sensor. These electrodes are connected to anode and cathode channels, which collect these elementary electrical signals and transmit them to an electronic processing loop of these signals.
• this electronic processing loop processes this electrical signal in one or more steps, such as, for example, an amplification, a filtering and a coding in computer bits, intended to make it exploitable by a means of operation such as a computer or visualization, such as a screen.
• steps such as, for example, an amplification, a filtering and a coding in computer bits, intended to make it exploitable by a means of operation such as a computer or visualization, such as a screen.
• FIG. 1 of this document shows that the anode associated with each of the elementary sensors is connected to its own anodic measurement channel, which comprises an electronic processing loop intended to digitize the signal emitted by this elementary sensor. All the cathodes of the elementary sensors are interconnected with each other and connected to a single cathode measurement channel. It is therefore necessary to provide a number of anode channels of measurement equal to the number of elementary sensors, and corollary as many electronic processing loops.
• the number of elementary sensors can reach 10,000, for example for a square matrix of 100 x 100 elementary sensors, or even 4,000,000 for a matrix of 2,000 x 2,000 elementary sensors. This corresponds to a total of 10,001 or 4,000,001 measurement channels, anodic and cathodic.
• the multiplication of the anode channels causes significant difficulties in making connections, and leads to a corollary increase in costs for their realization, especially in the context of the growing miniaturization of detectors, and therefore elementary sensors.
• the size of the detector increases in particular according to the number of measurement channels and their electronic processing loops that are often associated with them.
• Each subset of sensors thus defined thus forms a row or a column of the elementary sensor matrix, respectively according to one or other of the principal directions of this matrix.
• Each elementary sensor is thus connected to two anode channels, which respectively form the line and the column of the matrix at the intersection of which is located this sensor.
• the number of anode measurement channels necessary for detection is then reduced and becomes equal to the sum of the number of rows and the number of columns of the matrix constituting the detector, for example 200 for a matrix of 100 x 100 sensors.
• each elementary sensor emitting signals To reconstitute a digital image representative of the observed object or scene, it is necessary to precisely locate each elementary sensor emitting signals. To locate this sensor in such a configuration of anode channels, it is known to read and process the electrical signals that this sensor has emitted on the two channels, and by extension on the two anodic measurement channels to which it is connected, that is, its line and its column in the matrix. Thus, each sensor of the matrix is associated with a coordinate respectively in each of the two main directions of the matrix. These two coordinates thus make it possible to unambiguously identify the elementary sensor that has received the incident ray.
• anodes (3) each associated with an elementary sensor (10), made of a semiconductor material (2), are respectively interconnected by similar anode subsystems, in which species constituted by rectilinear anode channels (7, 8), and in each of the two main directions (D1, D2) of the matrix.
• Each anode channel (7, 8) is connected to a single anode measurement channel (11, 12), which comprises an elementary signal electronic processing loop (not shown).
• Each anode channel (7, 8) therefore forms a row or column of the elementary sensor array.
• Each elementary sensor (10) is connected to two anode channels (7, 8), which respectively form the line and the column of the matrix at the intersection of which this sensor is positioned.
• the number of measurement channels (7, 8) necessary for the detection is therefore equal to the sum of the number of lines, here ten, and the number of columns, here fourteen, ie in total twenty-four, in addition to the cathode channel (6) necessary to loop the measuring circuit.
• the operating circuit can unambiguously locate the elementary sensor that has received the incident ray and, by accumulating incident rays having interacted with several elementary sensors (10), reconstitute a digital image representative of the scene observed.
• the present invention is part of this research, and proposes a detector substantially reducing the importance of the technical and economic disadvantages mentioned above. Indeed, it makes it possible to reduce the number of measuring channels required in a detection device of the type in question.
• the object of the invention is therefore to provide a device for detecting particles or electromagnetic waves, whose structural characteristics make it possible to perform an effective detection at an affordable manufacturing cost.
• the invention relates to a device for detecting radiation, particles or electromagnetic waves, comprising at least one set of two-dimensional elementary sensors.
• Each elementary sensor of semiconductor nature, is intended to transform the energy of the radiation to be detected into electrical signals.
• each of the elementary sensors is provided with an anode on one of its faces and a cathode on the opposite face. The anode and the cathode are intended to be electrically connected to a circuit for reading and operating these signals.
• the anodes are electrically interconnected so as to form a plurality of anode subsets, which are electrically connected at least in pairs to an anodic measurement channel, which is intended to be connected to the read and write circuit; operation, - each anode is connected to two separate anode channels, the cathodes are electrically interconnected so as to constitute contiguous cathodic subsets, which are each electrically connected to a cathode measurement channel, the anodes belonging to two anode subsets connected to the same anode channel are associated with elementary sensors, whose cathodes associated with them belong to distinct cathodic subsets.
• the detector object of the invention consists of parallel anode subsets connected at least in pairs to the same anode measurement channel.
• all the cathodes are interconnected in groups to form contiguous and distinct cathode subsets, each of which is connected to a cathode measurement channel.
• Each anode is connected to two separate anode channels respectively according to one and the other of the two main directions of the two-dimensional set.
• each anode channel connects at least two anode subsets extending in the same direction, for example two rows or two columns, it is impossible for the operating circuit to precisely locate, in the matrix assembly, the elementary sensor having interacted with the incident ray and thereby formed a representative image of the observed scene.
• the elementary sensor having interacted with the incident ray and thereby formed a representative image of the observed scene.
• the electrical signals received on these two anode channels come from only one of these four sensors.
• the binding on an anodic measurement path common to several anode subsets extending in the same direction of the matrix set generates ambiguity or uncertainty of location or degeneracy, according to the term used by the man. of career.
• the cathodes of the detector object of the invention are not connected to the same cathode measurement channel. Indeed, the set of cathodes is segmented into several distinct cathode subassemblies thus having no cathode in common with each other. In addition, each cathode belongs to one and only one cathode subassembly. Finally, the detector is thus designed so that the anode subsets of the same anode measurement path necessarily depend on distinct cathode subassemblies.
• the cathode signal emitted by the cathode of the elementary sensor is received on a single cathode reading channel.
• the anodes belonging to two anode subsets connected to the same anode channel are associated with sensors whose cathodes belong to distinct cathode subsets. It is therefore possible to determine, according to each principal direction of the matrix assembly, the two anode subsets to which the signal-emitting sensor belongs, and thus, locate precisely this sensor, at the intersection of these two anode subsets.
• a detector according to the invention requires fewer anode measurement channels than the detectors of the prior art, since several anode subsets are grouped together on the same anode channel measurement. And even by adding to these anode channels the measurement cathode channels necessary for the removal of the uncertainty of location, the total number of measurement channels is smaller than that of a detector of the prior art.
• the number of cathode subassemblies is equal to the product of the number of anode subsets connected to the same anodic measurement channel according to one of the main directions of the invention. matrix assembly, by the number of anode subsets connected to the same anodic measurement channel according to the other main direction of the matrix assembly.
• the total number V of measurement channels required is then determined by the following expression:
• V N / n + M / m + n. m
• N is the number of anode subsets according to the first principal direction of the matrix, and therefore the number of rows of said matrix
• M is the number of anode subsets according to the second main direction of the matrix and therefore the number of columns of said matrix
• n is the number of anode subsets connected to the same anodic path according to the first principal direction of the matrix
• m is the number of anode subsets connected to the same anodic path according to the second principal direction of the matrix.
• nxm gives the number of cathode subassemblies necessary to remove the uncertainty of location mentioned above.
• the anode subsets are connected in pairs to said anode measurement channels and the cathodes are grouped into four distinct and adjacent cathode subsets.
• the detector also comprises anode subsets connected at least in pairs to an anode measurement channel, and whose set of cathodes associated with the elementary sensors is segmented into several cathodic subassemblies.
• the anodes are electrically interconnected so as to constitute a plurality of anode subsets, which are electrically connected at least in pairs to an anode measurement channel, which is intended to be connected to the circuit reading and operating, - each anode is connected to a single anode channel, the cathodes are interconnected electrically to form contiguous cathodic subassemblies, each of which is electrically connected to a measurement cathode channel, the anodes belonging to two anode subsets connected to the same anode channel are associated with elementary sensors, whose cathodes belong to distinct cathodic subsets.
• each anode is connected to a single anode measurement channel, and no longer two as in the first mode described, and this, according to one either of the two main directions of the two-dimensional set.
• an anode signal and a cathode signal are available to locate the elementary sensor, while the elementary sensor connected according to the first embodiment of the invention emits two anode signals and a cathode signal.
• This second embodiment of the invention implements the following physical phenomenon: during the interaction of a ray, particle or electromagnetic wave, with a semiconductor material, an electron cloud is created with a certain mobility.
• this cloud and of its induction zone created by its migration in the material, generally exceed those of an elementary sensor, so that the interaction in question is also likely to be detected by an elementary sensor adjacent to the sensor closest to the interaction site, thus capable of being taken into account by an anode subset that does not necessarily interconnect the anode of the elementary sensor in question, but generating at least one electrical signal secondary anodic.
• This secondary signal is received by an anode channel different from that receiving the main signal.
• the intensity of the secondary electrical signal is different from that of the main signal emitted by the elementary sensor.
• each anode of this detector requires only a number of measurement channels that are further reduced compared to a detector conforming to FIG. prior art exposed, but also with respect to a detector according to the first embodiment of the invention, each anode requires the connection to two measurement channels.
• the respective anode sub-assemblies interconnect the anodes of two lines and two adjacent columns along a broken line, the interconnected anodes belonging alternately to one then to the other of the two lines or two columns.
• first anode subassemblies extend parallel to the first main direction of the two-dimensional matrix assembly, and in particular parallel to the columns, and interconnect an anode on two belonging to the same column, the number of said first subsets corresponding to the number of elementary sensors present in the second direction of the matrix assembly; second anode sub-assemblies interconnecting all the anodes present in said second direction, and in particular along the same line and not interconnected by said first subsets.
• the elementary sensors are organized in a matrix form, the two dimensions of which define perpendicular directions. This embodiment has the advantage of simplifying the exploitation of the images obtained by the detector. The number of rows and columns of these matrices can be the same or different.
• the constituent semiconductor material of the elementary sensors is an alloy of cadmium, zinc and tellurium (CdZnTe).
• CdZnTe cadmium, zinc and tellurium
• other materials can be envisaged, such as for example CdTe: Cl, CdTe, CdHgTe, Si, Ge and generally any high resistivity semiconductor material.
• such a detection device thus substantially reduces the number of measurement channels required compared with the detectors of the prior art described above. It therefore reduces the importance of the mentioned drawbacks, especially in terms of cost and size of these detectors, especially given the significant reduction in connectivity.
• Figure 1 is a schematic representation of a detector of the prior art.
• Figure 2 is a schematic representation of a detection device according to a first embodiment of the invention.
• Figure 3 is a view similar to Figure 2, a second embodiment of the invention.
• Figure 4 is a view similar to Figure 2 of a third embodiment of the invention.
• Figure 5 is a view similar to Figure 2, a variant of the first embodiment of the invention.
• FIG. 2 illustrates a first embodiment of the invention.
• a detection device (101) consists of a substrate of semiconductor nature (102), for example an alloy of cadmium, zinc and tellurium (CdZnTe).
• this device (101) is divided into a set of two dimensions (D100, D200), and in particular a matrix of elementary sensors juxtaposed.
• One of the faces of each of the elementary sensors is associated with an anode (103), and the opposite face is associated with a cathode (104).
• Each anode and each cathode are respectively electrically connected to a read and operate signal circuit (109) connected to a computer not shown here.
• the anodes of the same line, in the direction (D100) respectively of the same column, in the direction (D200), of the matrix are electrically interconnected so as to constitute an anode subset (107, 108), here assimilable to a rectilinear channel.
• the anode subsets (107, 108) are electrically connected to the respective anodic measurement channels (111, 112) by one anodic measurement pair (111, 112).
• cathodes (104) of the same subset of elementary sensors are interconnected so as to constitute cathode subassemblies (104a, 104b, 104c, 104d).
• Each cathode subassembly (104a, 104b, 104c, 104d) is electrically connected to a cathode measurement channel (106a, 106b, 106c, 106d).
• the cathode subassemblies (104a, 104b, 104c, 104d) are contiguous and distinct, i.e. they have no cathode in common and their union forms a set including all cathodes (104) of elementary sensors (110).
• the number of cathode subassemblies (104 a, 104 b, 104 c, 104 d) is here equal to four, because there are two anodic channels (107) connected by anodic measurement (111) in the direction (D100 ), and two anode channels (108) anodically connected (112) according to the direction (D200).
• Each cathode subassembly thus combines the elementary sensors occupying a quarter of the surface of the matrix.
• an incident ray interacts with an elementary sensor
• a cloud of electrons is created within it, capable of transiting towards the anode (103) associated with this sensor, and thus of being collected, at any point in time. at least partly by this anode, brought to the proper potential.
• An electrical signal then travels the anode subsets (107, 108) including the anode (103) associated with this sensor, here a line and a column.
• This signal is then received by the anodic measurement channels (111, 112).
• These signals are processed by the electronic processing loops pertaining to each of these anodic measurement channels (111, 112).
• the operating circuit (109) can not precisely locate the sensor having emitted these signals, since each anodic measurement channel (111, 112) is respectively connected to two anode subsets (107, 108).
• the detector according to the invention is provided with cathode subassemblies (104a, 104b, 104c, 104d) contiguous and distinct, which therefore have no cathode in common.
• cathode subassemblies 104a, 104b, 104c, 104d
• the operating circuit 109) can remove the ambiguity and thus precisely locate the elementary sensor that has interacted.
• FIG. 3 represents a detector according to a second embodiment of the invention.
• the anode subassemblies (208) interconnect the anodes (203) of two adjacent rows and two columns along a broken line. In the example described, it is the interconnection of two columns.
• each anode subset (208) interconnects the anodes (203) belonging alternately to one and then to the other of the two columns.
• first anode subassemblies (308) extend substantially parallel to the second main direction (D400) of the matrix ( 301) and interconnect one anode (303) out of two.
• second anode subsets (307) interconnect all the anodes present in the second main direction (D400) of the matrix, and exclusively the anodes not connected by said first anode subsets (308).
• the uncertainty associated with this new reduction in the number of measurement channels, anodic in particular, is raised in the following manner: as already specified, the interaction of a ray, particle or electromagnetic wave, with the semiconductor material constituting the Elementary sensors induce the creation of an electron cloud, arising from the release of covalent electrons as a result of the energetic contribution of the radiation or the incident particle.
• This electronic cloud has a certain mobility.
• its dimensions may exceed those of the elementary sensor.
• the interaction in question is also detected by an elementary sensor adjacent to the sensor closest to the interaction site, and thus is collected by an anode subset different from the anode subset of the elementary sensor in question.
• FIG 5 illustrates a variant of the first embodiment of the invention. This differs from the form shown in Figure 2 in that to reduce the total number of measurement channels of the detector, it is sufficient to interconnect only two anode subsets on the same measurement path. In other words, it does not seem imperative to interconnect all the anode subsets or channels in the present case, on anode channels of common measurements.
• anode subsets (407 ', 407') are each connected in isolation to an anodic path of their own measurement (411 ', 411').
• the anodic measurement channels (411 ') and (41I') are each connected to a single anode subset, respectively (407 ') and (407') respectively.
• a detector which is in fact a hybrid detector, comprising anode subsets connected to the anode measurement channels, either in isolation (407 ', 407') as for the detectors of the prior art, such as that shown in Figure 1, is multiple (407, 408), as for a detector according to the invention shown in Figure 2.
• Figure 5 the location of an elementary sensor which has interacted with a ray, whatever the anode subset to which it belongs, presents no uncertainty.
• hybrid detectors require a number of measurement channels smaller than that of a detector of the prior art, but greater than that of a detector according to the invention, such as that represented in FIG. These hybrid detectors are therefore only of interest in certain particular cases.
• the main directions of the different sets of two dimensions (101, 201, 301, 401) shown in the figures are perpendicular to each other. They are matrices.
• a detector formed of a two-dimensional assembly, whose main directions are not perpendicular to each other, would obviously also be in accordance with the invention described here.
• FIG. 5 also illustrates a variant of the embodiment of the invention of FIG. 2, with the difference that the anode subassemblies are interconnected three by three (408) on each measurement channel (412) in one direction main matrix (columns), and two by two (407) according to the other main direction (lines) of said matrix.
• the detection device according to the invention significantly reduces the disadvantages of the prior art, particularly in terms of cost and efficiency. 'clutter detectors, besides connectivity.

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