A muon track detector design and a method for evaluating performance thereof

Abstract

The application discloses a kind of muon track detector design and performance evaluation method, it is related to the field of detector structure design;Two kinds of scintillator array layout scheme for muon track detector structure design are presented, one is based on the staggered layout of right triangular prism μ The track detector structure of son, can reflect better position resolution performance, especially after combining μ Son energy screening, can significantly improve the position resolution performance of μ Son detector.And the position resolution performance of the μ The track detector structure based on the staggered layout of diamond column is better when the comprehensive performance of broad spectrum energy μ Son is incident, the detection area is larger, and the number of readout channels can be reduced to reduce cost.The present application is conducive to improving the comprehensive performance of μ Son track detector, increasing the detection area, reducing the position resolution error, reducing the number of channels, reducing the cost and the like.Through the present application, this scheme and performance evaluation method can be widely applied to the detector design and performance evaluation in the field of μ Son imaging, μ Son track detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of muon track detector, and particularly relates to a muon track detector structure and an evaluation method. BACKGROUND

[0002] The muon track detector based on plastic scintillator is widely used in the field of muon detector and muon imaging. The muon detector is composed of multiple scintillator array planes, and each scintillator array plane is composed of multiple scintillator strips. When a muon passes through the scintillator array of the muon detector, the muon interacts with the scintillator unit to deposit energy and generate scintillation photons. By detecting the photon signals in different scintillator units, the muon track can be further obtained. For example, the utility model patent cosmic ray muon imaging device (CN 220671641 U). The reasonable structure layout design makes the muon pass through two or more adjacent scintillator units when it enters the detector layer, and the center of gravity method can obtain a more accurate position of the muon. The most common is the three-prism structure scintillator unit and the staggered arrangement layout of the scintillator array, such as the invention patent muon detector, three-dimensional photographic imaging method, device and storage medium (CN 116953770 A). However, the above research has its own limitations and deficiencies. First, the light collection efficiency of the scintillator unit is not considered in the current muon detector structure design, and the detection area is small and the position resolution is low. Secondly, there is a lack of comprehensive performance evaluation method for the muon detector. In addition, a scintillator array layout with better performance needs to be proposed for the structure design of the muon track detector. SUMMARY

[0003] (I) Invention purposes

[0004] The purpose of the present application is to provide a scintillator array layout for the structure design of a muon track detector and a comprehensive evaluation method for the muon track detector, to solve the problems of low position resolution, small detection area and difficult overall comprehensive performance evaluation of the muon track detector based on plastic scintillator.

[0005] (II) Technical solutions

[0006] In order to achieve the above purpose and solve the above technical problems, the technical scheme of the present application is as follows:

[0007] A muon track detector design method for improving the position resolution and detection area of the muon track detector, comprising the following steps:

[0008] Step 1: Constructing a plastic scintillator detection unit

[0009] The muon track detector based on plastic scintillator is a scintillator array composed of multiple plastic scintillator detection units, so the plastic scintillator unit needs to be constructed first. First, the plastic scintillator is processed into plastic scintillator strips in the shape of rhombic column and right triangular prism, the length of which is determined according to the area of the muon track detector, and the width is determined according to the number of readout channels and the area of the detector; when the length of the plastic scintillator strip is greater than 30 cm, a groove needs to be opened on the surface of the plastic scintillator strip to bury the shift wave optical fiber, the groove width is slightly larger than the diameter of the shift wave optical fiber, and the groove depth is twice the diameter of the shift wave optical fiber; the shift wave optical fiber is buried in the groove and fixed with optical glue; then the plastic scintillator is packaged with a reflective layer and a light-proof layer; a light outlet is left on one side of the end face of the plastic scintillator strip, and the size of the light outlet is matched with the size of the SiPM, and the SiPM is used to collect scintillation photons.

[0010] Step 2: Constructing the layout of the plastic scintillator array

[0011] In the plastic scintillator array, the end face of each plastic scintillator detection unit is coupled with a SiPM for individual readout of signals, and the light-proof layer is used to isolate different scintillator units to prevent light crosstalk between different units. When a muon passes through different detection units, the size of the generated signal is different due to the different track lengths, and the signal amplitude is linearly proportional to the track length under the same conditions. Therefore, when constructing the plastic scintillator array, it is necessary to increase the contact area between different plastic scintillator detection units as much as possible to improve the position resolution, and to increase the width of the plastic scintillator unit without affecting the position resolution performance to increase the detector area. Based on this design concept, the present application constructs an isosceles triangular staggered layout, a rhombic staggered layout, a right triangular staggered layout, a hexagonal staggered layout, a rectangular stacked layout and a rectangular tiled layout, a total of 6 plastic scintillator array layout methods. Through Geant4 simulation, the position resolution performance and detection area of the muon track detector based on the 6 different plastic scintillator array layouts are calculated. The final calculation results show that: when the average width of the plastic scintillator detection unit is less than 15 mm, the right triangular staggered layout has the best position resolution performance, which is the optimal scheme, and when the average width of the plastic scintillator detection unit is greater than 15 mm, the rhombic staggered layout has the best comprehensive performance of position resolution performance, detection area and channel number, which is the optimal scheme, so the two scintillator array layout schemes are selected to form the next step of the muon track detector.

[0012] Step 3: Forming the muon track detector

[0013] After Geant4 simulation and position resolution index PRI calculation, two muon track detector structure schemes with good comprehensive performance are constructed, which are shown in Figure 4 and Figure 5 . Figure 4A muon track detector structure based on rhombic column staggered layout, wherein the cross-sectional shape of the scintillator unit is rhombic, the height (Z direction) is 10 mm, and the width (X direction) is 5-30 mm. Figure 5 A muon track detector structure based on right triangular prism staggered layout, wherein the cross-sectional shape of the scintillator unit is right triangular, the height (Z direction) is 10 mm, and the width (X direction) is 5-30 mm. In both structure layouts, the length (Y direction) of the scintillator unit can be set according to the size of the detector, and when the length is greater than 30 cm, an embedded wave-shifting fiber is needed to enhance the light collection efficiency and muon detection efficiency. In addition, in the rhombic column staggered layout and the right triangular prism staggered layout, the X direction width of the scintillator unit can be modified to different sizes as needed; the Z direction height and Y direction length of the scintillator unit can also be appropriately modified as needed.

[0014] The two schemes have different application cases. When the average width of the scintillator unit is less than 15 mm, the muon track detector structure based on right triangular prism staggered layout has the best position resolution performance, and if the cost increase caused by the increase in the number of readout channels is considered, the muon track detector structure based on rhombic column staggered layout can be used, sacrificing part of the position resolution performance. In addition, when the muon energy is broad spectrum, the muon track detector structure based on rhombic column staggered layout is optimal, and when the muon track detector has a muon energy measurement design or the muon source is a single-energy muon source, the muon track detector structure based on right triangular prism staggered layout is the optimal scheme.

[0015] The application also provides a muon track detector performance evaluation method.

[0016] When a muon enters the scintillator array, it will deposit energy in the plastic scintillator to generate scintillation photons, and then a silicon photomultiplier (SiPM) or a photomultiplier will convert the light signal into an electrical signal. The spatial coordinates of the muon incidence are located by the signal size of the readout channel, and when the muon simultaneously passes through two or more adjacent scintillator units, the barycenter method is used to accurately calculate the position of the muon incidence, and the barycenter method calculation formula is:

[0017]

[0018] In the formula, P m ′ uon P is the position of the muon calculated by the barycenter method, Q i is the signal size corresponding to the i-th plastic scintillator, P i is the position of the plastic scintillator.

[0019] The position error ΔP is calculated by formula (2), P muon is the true position of the incident muon.

[0020] Delta P = P' muon -P muon (2)

[0021] The comprehensive performance of a muon track detector needs to be evaluated by multiple indexes.A good muon track detector needs a larger detection area to capture as many muon events as possible, fewer scintillator units to reduce the cost of the readout electronic system, and smaller position resolution error to improve imaging quality.This means that the size of the scintillator detection unit is as large as possible, and the position error of the muon track detector is as small as possible, so the present application defines a position resolution index PRI to evaluate the position resolution performance of the muon track detector, and the calculation formula is shown in formula (3), wherein L represents the total length of the scintillator array, N is the number of scintillator units, and W is the average width of the scintillator unit, W = L / N.

[0022]

[0023] The position resolution index PRI can comprehensively consider the detection area, channel number and position resolution error of the muon track detector, and therefore can be used for comprehensive performance evaluation of muon track detectors of different structures.

[0024] (Three) effective benefits

[0025] 1. The muon track detector structure based on the right-angle triangular prism staggered layout in the present application has better position resolution performance compared with the existing muon track detector structure.Especially when a single-energy muon source or a muon energy screening device is installed, the structure can significantly improve the position resolution performance of the plastic scintillator muon detector.

[0026] 2. The muon track detector structure based on the rhombic column staggered layout in the present application has better comprehensive performance advantages compared with the existing muon track detector structure, mainly including a large detection area, fewer readout channels, and smaller position resolution error.Meanwhile, it is more suitable for position detection of cosmic ray muon sources without other extra devices, and has better comprehensive performance and economy.

[0027] 3. The muon track detector comprehensive performance evaluation method based on the PRI index provided in the present application considers position error, detector area, readout channel number, economic cost and other factors, and provides a unified evaluation index for plastic scintillator muon track detectors of different structural types. DETAILED DESCRIPTION

[0028] Figure 1 The side size of the rhombic column scintillator in the embodiment of the present application is shown in the following table:

[0029] Figure 2 The side size of the right-angle triangular prism scintillator in the embodiment of the present application is shown in the following table:

[0030] Figure 3 The diamond-shaped columns of the embodiment of the present invention are arranged in a staggered manner;

[0031] Figure 4 The embodiment of the present invention has a right-angled triangular prism arrangement layout;

[0032] Figure 5 Schematic diagram of the effect of scintillator unit length on light collection efficiency;

[0033] Figure 6 Schematic diagram of the effect of optical fiber shape and size on light collection efficiency;

[0034] Figure 7 A diagram showing the position resolution performance of different scintillator array layouts;

[0035] Figure 8 Schematic diagram of the effect of incident muon energy on the position resolution performance of the scintillator array. Specific implementation plan

[0036] The present invention will be further explained and illustrated below based on the accompanying drawings and embodiments.

[0037] The present invention designs a plastic scintillator array layout design scheme for muon track detectors.

[0038] Customized plastic scintillator cross-sectional dimensions such as Figure 1 、 Figure 2 . Figure 1 The size of the middle diamond is 20mm×10mm. Figure 3 The right triangle measures 10 mm x 10 mm. The fiber groove is 2 mm deep and 1 mm wide. After the fiber is embedded, the remaining space is filled with optical adhesive. The end-face light outlet measures 3 mm x 3 mm, and is then coupled to a 3 mm x 3 mm SiPM. If the plastic scintillator is less than 30 cm long, the SiPM can be coupled directly to the side of the scintillator without slotting the fiber.

[0039] Construct a plastic scintillator array layout, wrap aluminum foil or ESR film outside the scintillator unit as a reflective layer, and when constructing the scintillator array, use black light-proof tape to encapsulate the outside of the scintillator unit as a light-proof layer to prevent light crosstalk between different scintillator units. Figure 3 、 Figure 4 .

[0040] The muon measurement and detector performance evaluation are carried out: the scintillator array is packaged, and then the corresponding readout electronics system is connected for signal readout and data processing, and muon track measurement is carried out. In terms of performance evaluation, the total width L of the scintillator array is first calculated, and the average width W of the scintillator unit is L / N, where N is the number of scintillator units. Then the center of gravity method is used to calculate the muon position P m ′ uon , and the position error ΔP = P muon is obtained by comparing the real position P m ′ uon -P muon . Finally, the position resolution performance of the muon track detector is evaluated by the position resolution index (PRI), where PRI = W / ΔP.

[0041] Figure 5 is the influence of the length of the scintillator unit on the light collection efficiency, when the length of the scintillator is less than 30 cm, there is no need to embed the shift wave optical fiber, and when the length of the scintillator is greater than 30 cm, the shift wave optical fiber needs to be embedded to enhance the light collection efficiency.

[0042] Figure 6 is the influence of the shape and size of the optical fiber on the light collection efficiency, the larger the diameter of the optical fiber, the better the light collection efficiency, and in addition, the light collection efficiency of the square shift wave optical fiber is better than that of the circular shift wave optical fiber.

[0043] Figure 7 is the position resolution performance of different scintillator array layouts, where Rhombic is a rhombic column staggered layout, and Triangle2 is a right triangular prism staggered layout. The position resolution performance of the muon track detector decreases with the increase of the average width of the detector unit, and finally the right triangular prism staggered layout and the rhombic column staggered layout are selected.

[0044] Figure 8 The influence of the incident muon energy on the position resolution performance of the scintillator array, where Rhombic is a rhombic column staggered layout, and Triangle2 is a right triangular prism staggered layout. The results show that the right triangular prism staggered layout has better position resolution performance when a single-energy muon is incident, and the rhombic column staggered layout has better position resolution performance when a broad-spectrum muon is incident.

[0045] The above is a further detailed description of the present application in combination with specific embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be regarded as falling within the protection scope of the present application.

Claims

1. A muon track detector design method for improving the position resolution and detection area of ​​the muon track detector, characterized in that: The specific steps include: Step 1: Build the Plastic Scintillator Detection Unit The plastic scintillator is processed into a rhombus-shaped plastic scintillator strip and a right-angled triangular prism plastic scintillator strip, the length of which is determined according to the area of ​​the muon track detector, and the width is determined according to the number of readout channels and the detector area; When the length of the plastic scintillator strip is greater than 30 cm, it is necessary to cut a groove on its surface to embed the wave-shifting fiber. The groove width should be slightly larger than the diameter of the wave-shifting fiber, and the groove depth should be twice the diameter of the wave-shifting fiber. The wave-shifted optical fiber is buried in the groove and fixed with optical glue; then the reflective layer and the light-shielding layer are encapsulated around the plastic scintillator; A light outlet is left on one end face of the plastic scintillator strip, the size of which matches that of the SiPM, and the SiPM is used to collect scintillation photons. Step 2: Build the Plastic Scintillator Array Construct a plastic scintillator array according to the following conditions: When constructing a plastic scintillator array, the contact area between different plastic scintillator detection units is increased to improve position resolution; Increase the width of the plastic scintillator detection unit to increase the detector area; Step 3: Forming the muon track detector After Geant4 simulation and position resolution index PRI calculation, two muon track detector structure schemes were constructed; The muon track detector structure is based on a staggered layout of diamond columns, where the cross-section of the scintillator detection unit is a diamond shape with a height of 10 mm in the Z direction and a width of 5-30 mm in the X direction; The muon track detector structure is based on a staggered layout of right-angled triangular prisms, where the cross-sectional shape of the scintillator detection unit is a right-angled triangle with a height of 10 mm in the Z direction and a width of 5-30 mm in the X direction; In the above two structural layouts, the length of the scintillator detection unit in the Y direction is set according to the size of the muon track detector. When the length in the Y direction is greater than 30 cm, an embedded wave-shifting fiber is required to enhance the light collection efficiency and muon detection efficiency.

2. A muon track detector design method according to claim 1, characterized in that: In the step 1, the plastic scintillator detection unit can be replaced by a photomultiplier tube or a photoelectric conversion element.

3. A muon track detector performance evaluation method, which can be used to evaluate the performance of the detector designed in any one of claims 1 or 2, characterized in that: The steps include: The position resolution index PRI is defined to evaluate the position resolution performance of the muon track detector. The calculation formula is shown in formula (1): Where L represents the total length of the scintillator array, N is the number of scintillator detection units, and W is the average width of the scintillator detection unit, W = L / N; ΔP is the position error; The position error ΔP is calculated by formula (2), P muon is the true position of the incident muon; ΔP=P′ muon -P muon (2) The spatial coordinates of the muon incident are located by reading out the signal size of the channel. When a muon passes through two or more adjacent scintillator detection units at the same time, the center of gravity method is used to accurately calculate the position of the muon incident. The calculation formula of the center of gravity method is: Where P′ muon is the muon position calculated by the center of gravity method, Q i is the signal size corresponding to the i-th plastic scintillator, P i is the position of the plastic scintillator.

4. The performance evaluation method of a muon track detector according to claim 3, characterized in that: Used in gas detectors, semiconductor detectors and scintillator detectors.

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