RU2379711C1 - Method of determining coordinates of charged particles - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to methods for determining spatial position and energy of relativistic particles, streams of ionising radiation and optical radiation. The method of determining coordinates of charged particles involves placing a recording matrix made from N-N regularly arranged elements on the path of charged particles. Each element is made from three types of luminophors which are distinguished by wavelength of radiation maximum, where each i^th element (where i=1, 2, 3…N) with coordinates x_i, y_i corresponds to a single concentration ratio a/b/c of three luminophors, corresponding to coordinates of the i^th element in the matrix and recorded in the memory of the recording device. Luminescent emission arising from charged particles falling onto the matrix is directed to three photodetectors with selective coefficients of spectral response n_a n_b, n_c, matched with wavelength of radiation maximum of corresponding luminophors and recorded in the memory of the recording device. Output signals S₁ S₂, S₃ of the photodetectors are transmitted to the recording device where they are summed up, normalised to the value of the obtained sum, and values S_1norm, S_2norm, S_3norm are obtained, and values k₁=S_1norm/n_a k₂=S_2norm/n_b, k₃=S_3norm/n_c are determined in the recording device. The ratio of obtained values k₁/k₂/k₃ is compared with concentration ratios of three luminophors ai/bi/ci recorded in the recording device. Coordinates of the charged particles x, y are determined from the coordinate of that i^th element the concentration ratio ai/bi/ci of which coincides with ratio of the obtained values k₁/k₂/k₃.

EFFECT: new method of determining coordinates of charged particles.

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Description

The invention relates to methods for determining the spatial position and energy of relativistic particles, flows of ionizing radiation and light radiation. The invention can be used to create low-channel position-sensitive sensors designed for use in high energy physics, astronomy, astrophysics, nuclear particle spectroscopy, as well as in threshold single-photon detection systems for special purposes.

A number of known methods for determining the spatial position and energy of relativistic particles and electromagnetic radiation.

There is a method of determining the spatial position of the ionizing radiation source (see application KR No. 20070101458, IPC G01T 7/60, published October 17, 2007), in which the detector field is sequentially scanned element by element using space charge-coupled arrays (CCD matrices). During the scanning process, the two-dimensional coordinates of the particles are represented as a time sequence of pulses from the CCD of the matrix.

However, sequential scanning of the entire sensor field inevitably leads to sufficiently large read times (≥10 ^-5 s) of the signal and does not allow efficient registration of fast processes, i.e. work in real time.

In order to be able to work in real time, various versions of the method for determining the coordinates of charged particles from projections of the signal of a recorded event on the orthogonal axes X and Y are used. This method for determining the spatial position of relativistic particles is based on radiation detection using a two-dimensional pixel matrix composed of receiving elements, despite the fact that the electrical output from each element is connected to peripheral electronic devices using buses parallel to each other vuyuschim coordinate axes X and Y.

So there is a known method for measuring the coordinates of gamma rays (see application US No. 820050006589, IPC G01T 1/00, published January 13, 2005), in accordance with which the quantum is sent to a pixel matrix formed from strips of scintillation crystals. In this case, each scintillation pixel is associated with photosensors parallel to the X and Y coordinate axes. As a result of the interaction of the gamma quantum with the corresponding pixel of the scintillator matrix, secondary radiation arises, which is detected by the corresponding photosensors and thus determines the signal coordinates.

The disadvantage of this method is the formation of a scintillation matrix of single crystals, the characteristic dimensions of which cannot provide the small size of a single pixel and, accordingly, high resolution. In addition, the connection of each pixel in the described method with photosensors determines the inevitable multichannel method.

To reduce the size of a single pixel of the recording matrix and increase its resolution, various modifications of the method for determining the coordinates of charged particles from the projections of the signal of the recorded event on the orthogonal axes X and Y are proposed. Thus, the method is currently widely used (see Z. U, Novel silicon stripixel detector : concept, simulation, design, and fabrication. - Nuclear instruments and Methods in Physics Research. - A 518, 2004, pp738-753), in which a stripping matrix made in the form of a network of photodetectors (diodes, transistors) is mounted on the path of a charged particle. etc.). The coordinates of the charged particle are determined by registering the interaction of the charged particle with the strip pixel, which is preliminarily formed in the form of a grid of photodetectors (diodes, transistors, etc.). In this case, the photodetectors are placed on 2 perpendicular strips that have independent contact leads to signal lines parallel to the respective strips, i.e. coordinate axes X and Y.

However, this method also retains a fundamental drawback of the method of determining the coordinates of the event by projecting the signal onto the orthogonal X and Y axes: the multichannel system of output and processing of electrical signals is preserved, which necessitates the formation of a contact grid and a multichannel system of secondary electronic devices with a high integration density designed information retrieval. Currently, the number of output channels of detectors using this method of determining coordinates varies from 32 to several thousand. For example, a 70 × 53 mm ² strip-type detector manufactured by Hamamtsu, used in the PAMELA international program, has 1024 + 1024 channels (see P. Picozza, AMGaiper, G. Castellini et al. - Astroparticie Physics. - 27 , 2007, pp296-315). A large degree of multichannelism requires the creation of large-sized peripheral devices and increases the necessary volume of recording systems, which is a serious limiting factor in space experiments. Especially serious limitations this problem imposes on the use of position-sensitive PMTs as on-board special-purpose devices. In addition, the high density of the contact grid and the large total length of the contact tracks causes an increase in the operating temperature of the detector, causing a sharp increase in the noise level. The requirement to reduce the noise level when operating detectors with small pixel sizes leads to the need for their operation at low temperatures, which also dramatically reduces their use.

A known method for determining the two-dimensional coordinates of an event on a plane (see patent US 7175095, IPC G06K 19/06, published 13.02.2007), based on the establishment of a one-to-one correspondence between the position on the plane of a single element of the recording matrix and the introduced individual attribute of this element. In this method, the recording plane is divided into many individual elements containing several pixels. Inside each element, pixels are formed, characterized by a different combination of two parameters, such as the location of the pixels inside a single element and their size, or their location and color, or their location and shape, etc. Images of all individual elements are optically reduced to a scanning CCD matrix, a signal with which analyze using the appropriate decoding program.

In the known method, the scanning field of the CCD matrix is reduced to the size of a single element containing several pixels. In addition, when implementing this method, the determination of two-dimensional coordinates on the plane does not require a multi-channel detection system. However, the need to scan the image using a CCD matrix still reduces the speed of the method and does not allow working in real time.

The closest in purpose and combination of essential features to the claimed technical solution is a method for determining the coordinates of particles (see application US No. 2008017805, IPC G01T 1/18, published January 24, 2008), adopted as a prototype in which two-dimensional coordinates of particles on a plane are determined in real time by introducing a one-to-one correspondence between the coordinate of the event on the target plane and the pre-set numbers of the electrodes of the local and global networks of the information output system.

каналов, где N равно числу всех локальных электродов. В регистрирующем устройстве сравнивают электрические сигналы с записанными в регистрирующем устройстве номерами локальных и глобальных электродов. В результате сопоставления комбинации номеров локального и глобального электродов определяют пространственное положение локального электрода, на котором возник сигнал, и тем самым определяются координаты события.The position of the particles on the plane in the prototype is determined as follows. On the path of the charged particles, a recording matrix is placed, made of unit cells that are sensitive to the detection of the detected particle, formed from position-sensitive electrodes having a two-level organization, where the first level is composed of local electrodes to determine the local position of the particles, and the second level is composed of global electrodes for determining the global position of the particles, and each unit element with coordinates x _i , y _i corresponds to the numbers of local and global th electrodes corresponding to the coordinates of a single element in the matrix and recorded in the memory of the recording device; direct electrons and ions arising from the hit of a charged particle into the matrix to local and global position-sensitive electrodes. As a result, electrical signals appear at the local and global electrodes closest to this point. In the recording device receive output from

channels, where N is equal to the number of all local electrodes. In the recording device, electrical signals are compared with the numbers of local and global electrodes recorded in the recording device. By comparing the combination of numbers of the local and global electrodes, the spatial position of the local electrode on which the signal appeared is determined, and thereby the coordinates of the event are determined.

, a N - число локальных электродов. Однако такое сокращение числа выходных каналов оставляет этот метод в рамках многоканальных способов съема информации. Кроме того, в этом случае на поверхности детектора остается контактная сетка, необходимая для подсоединения локальных электродов к локальным шинам и глобальным электродам, а также контактная сетка вывода информации с локальных и глобальных электродов. В результате даже при достижении описанной в патенте плотности контактов разрешающая способность (фактический размер пикселя) достигает 400 мкм.The separation of the information retrieval system at the local and global levels allows you to set the coordinate of the event in real time while reducing the number of output channels by n times, where

, a N is the number of local electrodes. However, such a reduction in the number of output channels leaves this method as part of multichannel information retrieval methods. In addition, in this case, on the surface of the detector, there remains a contact grid necessary for connecting local electrodes to local buses and global electrodes, as well as a contact grid for outputting information from local and global electrodes. As a result, even when the contact density described in the patent is achieved, the resolution (actual pixel size) reaches 400 microns.

The problem to which the invention is directed is the development of such a method for determining the coordinates of charged particles, which would reduce the number of communication channels to three channels, regardless of the number of pixels of the recording matrix, and also eliminate the reading electrodes on the surface of the recording target and thereby increase the coefficient filling the target area with sensitive elements while maintaining the ability to work in real time.

The problem is solved in that the method for determining the coordinates of charged particles involves placing on the path of the charged particles a recording matrix composed of N · N regularly arranged elements, each of which is made of three types of phosphors that differ in wavelength of maximum radiation. Each element i (where i = 1, 2, 3 ... N) with coordinates x _i , y _i corresponds to a unique concentration ratio a _i / b _i / с _{i of} three phosphors,

Where

and _i is the concentration of the first phosphor in the i-th element;

b _i is the concentration of the second phosphor in the i-th element;

с _i - concentration of the third phosphor in the i-th element;

corresponding to the coordinates of the element i in the matrix and recorded in the memory of the recording device. Each of the phosphors emits light in its spectral region with an intensity proportional to its concentration at a given point. The luminescent radiation of phosphors arising from a charged particle entering the matrix is directed to three photodetectors having selective spectral sensitivity coefficients n _a , n _b , n _c matched to the wavelength of the maximum radiation of the corresponding phosphors and recorded in the memory of the recording device. The output signals S ₁ , S ₂ , S _{3 of the} photodetectors are fed to a recording device, in which these signals are summed and normalized to the value of the sum obtained and the values of S _1norm , S _2norm , S _{3norm are obtained} . The values k ₁ = S _1norm / n _a , k ₂ = S _2norm / n _b , k ₃ = S _3norm / n _{s are} determined in a recording device. The ratio of the obtained values of k ₁ / k ₂ / k _{3 is} compared with the concentration ratios of the three phosphors a _i / b _i / c _i recorded in the recording device, with which the coordinates of the charged particle x, y are determined by the coordinate of that i-th element, the concentration ratio a _i / b _i / c _i which coincides with the ratio of the obtained values of k ₁ / k ₂ / k ₃ .

The inventive method is based on the fact that the two-dimensional coordinates of particles on a plane are determined by introducing a one-to-one correspondence between the predetermined concentration ratio of the three different scintillators a _i / b _i / c _i in each ith unit element and the coordinates of this element on the target plane. Thus, the need for forming sensing electrodes on the surface of the recording matrix is eliminated. In addition, for any number N · N of regularly arranged elements of the recording matrix, the use of 3 phosphors is necessary and sufficient to obtain unambiguous information about the coordinates of the event, it is invariant to the energy of the incident radiation. As a result, the number of output channels for any number of elements of the recording matrix is three. The set of output signals S ₁ , S ₂ , S ₃ corresponds to a single point of the target x _i , y _i and a single energy value S. At the same time, it is possible to register the coordinates of events in real time.

The inventive method for determining the coordinates of charged particles is illustrated in the drawing, where

figure 1 shows a diagram of a device that implements the inventive method;

figure 2 shows on an enlarged scale a plot of the recording matrix.

The device includes: a recording matrix 1 composed of N · N elements 2, a focusing device 3, three photodetectors 4, 5, 6, respectively, and a recording device 7.

The method is as follows (see figure 1, figure 2). A recording matrix 1 composed of N · N elements 2 is placed in the path of the particle flow, which is formed by applying three phosphors with different wavelengths at the maximum radiation, high luminescence efficiency and low luminescence time of all three phosphors, which allows the detector to work in real time . The application of phosphors can be carried out, for example, by sequential vacuum deposition through a mask in such a way that the concentration a _{i is} proportional to the X coordinate, the concentration b _i is proportional to the Y coordinate, and the concentration c _i changes according to the law with _i = х _i ² + у _i ² . As a result, in matrix 1, each i-th element 2 (where i = 1, 2, 3 ... 10) with coordinates x _i , y _i corresponds to a unique concentration ratio a _i / b _i / с _{i of} three phosphors. The luminescent radiation of the phosphors arising from a charged particle entering the matrix 1 through a focusing device 3 is directed to three standard photodetectors 4, 5, 6 having selective spectral sensitivity coefficients n _a , n _b , n _c respectively, consistent with the wavelength of the maximum radiation of the corresponding phosphors and recorded in the memory of the recording device 7. The signals S ₁ , S ₂ , S _{3 that} occur at the output of the photodetectors 4, 5, 6 are supplied to the recording device 7, in which these signals are summed and normalized I am on the value of the amount received. Normalization is performed to exclude the dependence of the output signal on the energy of the detected particle. As a result, the values of S _1norm , S _2norm , S _{3norm are obtained} and k ₁ = S _1norm / n _a , k ₂ = S _2norm / n _b , k ₃ = S _3norm / n _{c are} determined in the recording device 7. The ratio of the obtained values of k ₁ / k ₂ / k _{3 is} compared with the concentration ratios of the three phosphors a _i / b _i / c _i recorded in the recording device 7, by which the coordinates of the charged particle x, y are determined by the coordinate of that i-th element 2, the concentration ratio a _i / b _i / c _i which coincides with the ratio of the obtained values k ₁ / k ₂ / k ₃ . Thus, the need for forming sensing electrodes on the surface of the recording matrix is eliminated. In addition, for any number N · N of regularly arranged elements 2 of the recording matrix 1, the use of 3 phosphors is necessary and sufficient to obtain unambiguous information about the coordinates of the event, it is invariant to the energy of the incident radiation. As a result, the number of output channels for any number of elements 2 of the recording matrix 1 is three. The set of output signals S ₁ , S ₂ , S ₃ corresponds to a single point of the recording matrix 1 and a single energy value. At the same time, it remains possible to register event coordinates in real time.

Example. The method was implemented when registering the coordinates of the gamma radiation flux with an energy of 10-100 MeV on the recording matrix. A recording matrix composed of 32 · 32 elements was placed on the path of the electron flow, which was formed as a result of applying three phosphors: bismuth germanate (Bi ₄ Ge ₃ O ₁₂ , hereinafter BGO), lead tungstate (PbWO ₄ , hereinafter PWO) and zinc selenide with an isovalent admixture of tellurium (ZnSe (Te)). The emission maximum of each of these phosphors has a different wavelength with a sufficiently high luminescence efficiency: λ _{max BGO} = 320 nm (5 · 10 ⁴ photons / MeV), λ _{max PWO} = 450 nm (18 · 10 ⁴ photons / MeV) and λ _{max ZnSe (Te)} = 610 nm (8 · 10 ⁴ photon / MeV). The short emission time of all three phosphors (5ns, 6ns and 3ns, respectively) provides the detector with the possibility of real-time operation. The phosphors were applied by sequential vacuum deposition through a mask in such a way that the concentration of BGO (a _i ) is proportional to the X coordinate, the concentration of PWO (b _i ) is proportional to the Y coordinate, and the concentration of ZnSe (Te) (c _i ) changes according to the law with _i = х _i ² + at _i ² . As a result, in the matrix, each element i (where i = 1, 2, 3 ... 10) with coordinates x _i , y _i corresponds to a unique concentration ratio a _i / b _i / с _{i of} three phosphors. The luminescent radiation of phosphors arising from a charged particle entering the matrix was directed through a collecting lens to three standard photodetectors having selective spectral sensitivity coefficients n _a = 0.25 A / W, n _b = 0.3 A / W, n _s = 0.4 A / W, matched with the wavelength of the maximum radiation of the corresponding phosphors and recorded in the memory of the recording device. These photodetectors were Edmund Optics silicon photodiodes with Edmund Optics interference filters “Narrow bandpass IF” applied to them. The signals S ₁ , S ₂ , S ₃ arising at the output of the photodetectors were applied to a recording device, in which these signals were summed and normalized to the value of the sum obtained, obtaining the values of S _{1 normal} , S _{2 normal} , S _{3 normal} . As a result, in the recording device, the values k ₁ = S _1norm / n _a , k ₂ = S _2norm / n _b , k ₃ = S _3norm / n _{c were determined} and the ratio of the obtained values k ₁ / k ₂ / k _{3 was} compared with those recorded in a recording device with the concentration ratios of the three phosphors a _i / b _i / c _i with which the coordinates of the charged particle x, y are determined by the coordinate of that i-th element, the concentration ratio a _i / b _i / c _i , which coincides with the ratio of the obtained values of k ₁ / k ₂ / k ₃ .

Claims (1)

A method for determining the coordinates of charged particles, including placing on a path of charged particles a recording matrix composed of N · N regularly arranged elements, each of which is made of three types of phosphors that differ in wavelength of maximum radiation, and to each i-th element (where i = 1 , 2, 3 ... N) with coordinates x _i , y corresponds to a single concentration ratio a / b / c of three phosphors,
where a _i is the concentration of the first phosphor in the i-th element;
b _i is the concentration of the second phosphor in the i-th element;
c _i is the concentration of the third phosphor in the i-th element,
corresponding to the coordinates of the i-th element in the matrix and recorded in the memory of the recording device; direct the luminescent radiation of the phosphors arising from the hit of the charged particle into the matrix to three photodetectors having selective spectral sensitivity coefficients n _a , n _b , n _s matched with the wavelength of the maximum radiation of the respective phosphors and recorded in the memory of the recording device; the output signals S ₁ , S ₂ , S _{3 of the} photodetectors are fed to a recording device, in which these signals are added up, normalized to the value of the received sum, and S _{1 normal} values are obtained,
S _2norm ; S _3norm ; determine in the recording device the values of k ₁ = S _{1 normal} / n _a ,
k ₂ = S _2norm / n _b , k ₃ = S _3norm / n _s ; comparing the ratio of the obtained values of k ₁ / k ₂ / k ₃ with the ratios of the concentrations of three phosphors a _i / b _i / c _i recorded in the recording device, using which the coordinates of the charged particle x, y are determined from the coordinate of that i-th element, the concentration ratio a _i / b _i / c _i which coincides with the ratio of the obtained values of k ₁ / k ₂ / k ₃ .

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