Mu track detector design and performance evaluation method thereof

Abstract

The invention discloses a muon track detector design and performance evaluation method, and relates to the field of detector structure design. Two scintillator array layout schemes used for muon track detector structure design are provided, one scheme is a muon track detector structure based on right-angle triangular prism staggered layout, better position resolution performance can be embodied, and especially after muon energy screening is combined, the position resolution performance of the muon detector can be remarkably improved. The position resolution performance of the muon track detector structure based on the staggered arrangement of the rhombic columns is better in comprehensive performance when broad-spectrum energy muons are incident, the detection area is larger, the number of reading channels can be reduced, and the cost can be reduced. According to the invention, the comprehensive performance of the muon track detector is improved, the detection area is increased, the position resolution error is reduced, the channel number is reduced, and the cost is reduced. According to the invention, the scheme and the performance evaluation method can be widely applied to detector design and performance evaluation in the fields of muon imaging and muon track detection.

Description

Technical Field

[0001] The invention relates to the technical field of muon track detectors, and in particular to a muon track detector structure and an evaluation method. Background Art

[0002] Muon track detectors based on plastic scintillators are widely used in the fields of muon detectors and muon imaging. Muon detectors are composed of multi-layer scintillator array planes, each of which is composed of multiple scintillator strips. When muons pass through the scintillator array of the muon detector, the muons interact with the scintillator units to deposit energy and generate scintillation photons. The muon track is further obtained by detecting the photon signals in different scintillator units. For example, the utility model patent cosmic ray muon imaging device (CN 220671641 U). Reasonable structural layout design allows muons to pass through two or more adjacent scintillator units at the same time when incident on the detector layer, and the center of gravity method can be used to obtain a more accurate position of the muon incident. The most common are triangular prism structure scintillator units and staggered scintillator arrays, such as the invention patent muon detector, three-dimensional photography imaging method, device and storage medium (CN 116953770 A), but the above research also has its own limitations and shortcomings. 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 methods to evaluate the comprehensive performance of muon detectors; in addition, it is necessary to propose a scintillator array layout with better performance for the structural design of muon track detectors. Summary of the invention

[0003] (I) Purpose of the invention

[0004] The purpose of the present invention is to provide a scintillator array layout for muon track detector structural design and a comprehensive evaluation method for muon track detector, which is used to solve the problems of low position resolution and small detection area of ​​muon track detector based on plastic scintillator and difficulty in unified evaluation of overall comprehensive performance.

[0005] (II) Technical solution

[0006] In order to achieve the above objectives and solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A muon track detector design method is used to improve the position resolution and detection area of ​​the muon track detector, comprising the following steps:

[0008] Step 1: Construct the 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 must be constructed first. First, the plastic scintillator is processed into a plastic scintillator strip of rhombus and right-angled 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 detector area; when the length of the plastic scintillator strip is greater than 30cm, it is necessary to make a groove on its surface to bury the wave-shifting fiber, the groove width is slightly larger than the diameter of the wave-shifting fiber, and the groove depth is twice the diameter of the wave-shifting fiber; bury the wave-shifting fiber in the groove and fill it with optical glue to fix it; then the reflective layer and the light-shielding layer are encapsulated on the plastic scintillator; a light outlet is left on one end face of the plastic scintillator strip, the size of the light outlet matches the size of the SiPM, and the SiPM is used to collect scintillation photons.

[0010] Step 2: Construct the Plastic Scintillator Array Layout

[0011] In the plastic scintillator array, each plastic scintillator detection unit is coupled to the SiPM end face for a separate signal readout, and different scintillator units are isolated by a light-shielding layer to avoid optical crosstalk between different units. When muons pass through different detection units, the signal sizes generated are different due to the different track lengths. After calculation and measurement, under the same conditions, the signal amplitude is linearly proportional to the track length. Therefore, when constructing a 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. In addition, it is necessary 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 invention constructs an isosceles triangle staggered layout, a rhombus staggered layout, a right triangle staggered layout, a hexagonal staggered layout, a rectangular stacked layout, and a rectangular tiled layout, a total of 6 plastic scintillator array layouts. Through Geant4 simulation, the position resolution performance and detection area of ​​the muon track detector based on 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 15mm, the right-angled triangle staggered layout has the best position resolution performance and is the optimal solution. When the average width of the plastic scintillator detection unit is greater than 15mm, the diamond staggered layout has the best comprehensive performance in position resolution performance, detection area and number of channels and is the optimal solution. Therefore, these 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 were constructed, see Figure 4 and Figure 5 . Figure 4It is a muon track detector structure based on a staggered layout of rhombus columns, wherein the cross-sectional shape of the scintillator unit is rhombus, with a height (Z direction) of 10 mm and a width (X direction) of 5-30 mm. Figure 5 It is a muon track detector structure based on a staggered layout of right-angled triangular prisms, in which the cross-sectional shape of the scintillator unit is a right triangle, with a height (Z direction) of 10 mm and a width (X direction) of 5-30 mm. In both structural layouts, the length of the scintillator unit (Y direction) can be set according to the size of the detector. When the length is greater than 30 cm, an embedded wave-shifting optical fiber is required to enhance the light collection efficiency and muon detection efficiency. In addition, in the staggered layout of rhombus columns and the staggered layout of right-angled triangular prisms, the width of the scintillator unit in the X direction can be modified to different sizes as needed; the height in the Z direction and the length in the Y direction of the scintillator unit can also be appropriately modified as needed.

[0014] The two schemes have different applicable situations. When the average width of the scintillator unit is less than 15mm, the muon track detector structure based on the staggered layout of right-angled triangular prisms has the best position resolution performance. If the cost increase caused by the increase in the number of readout channels is taken into account, the muon track detector structure based on the staggered layout of diamond columns can be used, sacrificing some position resolution performance. In addition, when the muon energy is broad spectrum, the muon track detector structure based on the staggered layout of diamond columns is the best. If the muon track detector has a muon energy measurement design or the muon source is a monoenergetic muon source, the muon track detector structure based on the staggered layout of right-angled triangular prisms is the best solution.

[0015] The invention also provides a method for evaluating the performance of a muon track detector.

[0016] When a muon enters the scintillator array, it deposits energy in the plastic scintillator to generate scintillation photons, and then the silicon photomultiplier (SiPM) or photomultiplier converts the optical signal into an electrical signal. The spatial coordinates of the muon incident are located by reading the signal size of the channel. When a muon passes through two or more adjacent scintillator 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:

[0017]

[0018] Where P m ′ uon 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.

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

[0020] ΔP=P′ muon -P muon (2)

[0021] The comprehensive performance of the muon track detector requires comprehensive evaluation using multiple indicators. A good muon track detector requires 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 a smaller position resolution error to improve the imaging quality. This means that the size of the scintillator detection unit should be as large as possible and the position error of the muon track detector should be as small as possible. Therefore, the present invention defines a position resolution index PRI to evaluate the position resolution performance of the muon track detector. The calculation formula is shown in formula (3), where 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, number of channels and position resolution error of the muon track detector, so it can be used for the comprehensive performance evaluation of muon track detectors with different structures.

[0024] (III) Effective income

[0025] 1. The muon track detector structure based on the staggered layout of right-angled triangular prisms in the present invention has better position resolution performance than the existing muon track detector structure. Especially when an artificial monoenergetic 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. Compared with the existing muon track detector structure, the muon track detector structure based on the staggered layout of diamond columns in the present invention has better comprehensive performance advantages, mainly including large detection area, fewer readout channels, and small position resolution error. At the same time, it is more suitable for the position detection of cosmic ray muon sources, without the need for other special devices, and has better comprehensive performance and economy.

[0027] 3. The comprehensive performance evaluation method of muon track detectors based on the PRI index proposed in the present invention takes into account factors such as position error, detector area, number of readout channels, and economic cost, and provides a unified evaluation index for plastic scintillator muon track detectors of different structural types. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The side dimensions of the rhombus column scintillator in the embodiment of the present invention;

[0029] Figure 2 The side dimensions of the right-angled triangular prism scintillator in the embodiment of the present invention;

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

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

[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 drawings and embodiments.

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

[0038] Customized plastic scintillator cross-sectional dimensions such as Figure 1 , Figure 2 . Figure 1 The size of the medium diamond is 20mm×10mm. Figure 3 The size of the right triangle is 10mm×10mm. The depth of the fiber groove is 2mm, the width of the groove is 1mm, and the remaining space is filled with optical glue after the fiber is embedded. The size of the end light outlet is 3mm×3mm, and then coupled with a 3mm×3mm SiPM. When the length of the plastic scintillator is less than 30cm, the fiber can be embedded without slotting, and the SiPM can be directly coupled to the side of the scintillator.

[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] Conduct muon measurement and detector performance evaluation: package the scintillator array, then connect the corresponding readout electronics system for signal readout and data processing, and perform muon track measurement. For performance evaluation, first calculate the total width L of the scintillator array, and the average width W of the scintillator unit = L / N, where N is the number of scintillator units. Then calculate the muon position P by the centroid method m ′ uon , and is the real position P of the incident muon muon Compare and find the position error ΔP = 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 The length of the scintillator unit affects the light collection efficiency. When the scintillator length is less than 30 cm, there is no need to embed the wave-shifting fiber. When the scintillator length is greater than 30 cm, it is necessary to embed the wave-shifting fiber to enhance the light collection efficiency.

[0042] Figure 6 It 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. In addition, the light collection efficiency of the square wave-shifted optical fiber is better than that of the circular wave-shifted optical fiber.

[0043] Figure 7 is the position resolution performance of different scintillator array layouts, where Rhombic is a staggered layout of rhombic columns, and Triangle2 is a staggered layout of right-angled triangular prisms. The position resolution performance of the muon track detector decreases as the average width of the detector unit increases. After comparison, the staggered layout of right-angled triangular prisms and the staggered layout of rhombic columns were finally selected.

[0044] Figure 8 The effect of incident muon energy on the position resolution performance of the scintillator array, where Rhombic is a staggered arrangement of rhombic columns, and Triangle2 is a staggered arrangement of right-angled triangular prisms. The results show that the staggered arrangement of right-angled triangular prisms has better position resolution performance when monoenergetic muons are incident, while the staggered arrangement of rhombic columns has better position resolution performance when broad-spectrum muons are incident.

[0045] The above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

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: Construct the Plastic Scintillator Detection Unit Processing the plastic scintillator into a rhombus-shaped column and a right-angled triangular prism-shaped plastic scintillator strip, the length of which is determined according to the area of ​​the muon track detector, and the width of which 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, it is necessary to make a groove on its surface to bury the wave-shifting fiber. The groove width is slightly larger than the diameter of the wave-shifting fiber, and the groove depth is twice the diameter of the wave-shifting fiber. The wave-shifting optical fiber is buried in the groove and fixed with optical glue; then the plastic scintillator is encapsulated with a reflective layer and a light-shielding layer; A light outlet is left on one end face of the plastic scintillator strip, the size of which matches the size of the SiPM, and the SiPM is used to collect scintillation photons; Step 2: Build the Plastic Scintillator Array The plastic scintillator array was constructed according to the following conditions: When constructing a plastic scintillator array, the contact area between different plastic scintillator detection units is increased to improve the position resolution; In addition, the width of the plastic scintillator detection unit is increased to increase the detector area without affecting the position resolution performance; Step 3: Forming the Muon Track Detector After Geant4 simulation and position resolution index PRI calculation, two muon track detector structure schemes were constructed; A muon track detector structure based on a staggered layout of rhombus columns, wherein the cross-sectional shape of the scintillator detection unit is rhombus-shaped, 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, in which 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 optical 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 rhombus staggered arrangement layout and the right-angled triangular prism staggered arrangement layout, the width of the scintillator detection unit in the X direction can be modified to different sizes as needed.

3. A muon track detector design method according to claim 1, characterized in that: The height in the Z direction and the length in the Y direction of the scintillator detection unit can be modified as needed.

4. 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 any device capable of performing photoelectric conversion.

5. A muon track detector design method according to claim 4, characterized in that: In the step 1, the plastic scintillator detection unit can be replaced by a photomultiplier tube or a photoelectric conversion element.

6. A muon track detector performance evaluation method, which can be used for the performance evaluation of the detector designed in any one of claims 1 to 5, 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 (3): Where L represents the total length of the scintillator array, N is the number of scintillator detection units, 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 real 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 the 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.

7. The performance evaluation method of a muon track detector according to claim 6, characterized in that: The comprehensive performance evaluation method based on the position resolution index can also be used for performance evaluation of other position sensitive detectors.

8. The performance evaluation method of a muon track detector according to claim 7, characterized in that: The comprehensive performance evaluation method based on position resolution index can be used for gas detectors, semiconductor detectors and scintillator detectors.

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