Miniaturized neutron and gamma detector

Abstract

The utility model provides a miniaturized neutron and gamma detector, and overcomes the defects that the existing neutron and gamma detector based on Li-based potassium cryolite crystals is not compact in structure and large in size, quality and power consumption. The detector comprises a detector outer shell, a crystal fixing inner shell, a crystal reflective layer, a detection crystal, a silicon photomultiplier and a data lead-out module, the detection crystal converts absorbed neutrons and gamma signals into visible light signals, the crystal reflective layer reflects and transmits the visible light signals to the silicon photomultiplier, the silicon photomultiplier converts the visible light signals into electric signals, and the data extraction module exports the electric signals to obtain the neutrons and gamma signals.

Description

Technical Field

[0001] This invention belongs to the field of radiation detection technology, specifically relating to a miniaturized neutron and gamma detector. Background Technology

[0002] Neutron and gamma-ray detection have important and wide-ranging applications in many fields related to national defense and people's livelihoods, such as border security, nuclear power facility monitoring, oil well logging, and high-energy physics. Currently, widely used neutron and gamma-ray detectors mainly consist of scintillators for detecting gamma rays and neutron detectors for detecting neutrons. 3 The system consists of two proportional counters, each generating a signal that is acquired and analyzed by its own signal processing and discrimination system to ultimately obtain valid neutron and gamma signals independently. 3 The main consumables in a proportional counter 3 Helium gas is in short supply and expensive, posing a risk of supply disruption. In addition, the back-end circuitry of the two detectors is complex and consumes a lot of power, resulting in inconvenience in use and large size.

[0003] Li-based potassium cryolite crystals are high-performance neutron and gamma-ray dual-readout materials, and there are currently related neutron and gamma detectors using Li-based potassium cryolite crystals, such as CLYC crystals. However, current neutron and gamma detectors based on Li-based potassium cryolite crystals mainly use photomultiplier tubes (PMTs) as light-collecting devices, which are large in size and power consumption. In addition, the structure of the crystal and photodetector is not compact, resulting in a large overall size and mass of the neutron and gamma detector, making miniaturization and portability impossible.

[0004] Therefore, in order to address the above problems, this invention provides a miniaturized neutron and gamma detector. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of current neutron and gamma detectors based on Li-based potassium cryolite crystals, which have a non-compact structure, large size, weight, and power consumption, and to provide a miniaturized neutron and gamma detector device.

[0006] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0007] A miniaturized neutron and gamma detector, characterized in that it includes a detector shell, a crystal-fixed inner shell, a crystal reflective layer, a detector crystal, a silicon photomultiplier tube, and a data extraction module.

[0008] The detector housing has a split structure, with its interior divided into two spaces by a partition: a signal acquisition space and a signal transmission space; the partition is provided with signal line guide grooves.

[0009] The crystal fixing inner shell has an upper and lower split structure, which is set in the signal acquisition space and fits against the detector outer shell; the lower split of the crystal fixing inner shell has a mounting position corresponding to the position of the signal line guide groove.

[0010] The crystal reflective layer has an upper and lower split structure, which is fitted inside the crystal fixing inner shell; the lower split of the crystal reflective layer has a notch corresponding to the mounting position;

[0011] The detection crystal is attached to the crystal reflective layer, with its light-emitting surface facing the notch. That is, there is no crystal reflective layer at the light-emitting surface of the detection crystal, while the rest of the crystal is tightly attached to the crystal reflective layer. The material of the detection crystal is Li-based potassium cryolite crystal (i.e., a potassium cryolite structure single crystal with Li as one of the main elements).

[0012] The silicon photomultiplier tube is installed at the mounting position of the crystal fixed inner shell, and its light receiving surface is optically coupled to the light emitting surface of the detector crystal.

[0013] The data extraction module is located in the signal transmission space and is connected to the silicon photomultiplier tube via a signal line;

[0014] As can be seen, the aforementioned crystal fixing inner shell is used to fix and protect the detector crystal, the crystal reflective layer, and the silicon photomultiplier tube, and it is in close contact with the crystal reflective layer that wraps the detector crystal; the detector outer shell is in close contact with the crystal fixing inner shell, and is used to further fix and protect the crystal fixing shell, the silicon photomultiplier tube, and the data output module.

[0015] The detector crystal absorbs neutron and gamma signals (neutron and gamma signals have extremely strong penetrating power and can penetrate the detector shell, the crystal fixing inner shell, and the crystal reflective layer in one go before being absorbed by the detector crystal) and converts them into visible light signals. The crystal reflective layer reflects the visible light signals and transmits them to the silicon photomultiplier tube. The silicon photomultiplier tube converts the visible light signals into electrical signals, and the data extraction module outputs the electrical signals to obtain the neutron and gamma signals.

[0016] Furthermore, the detector housing is rectangular in shape and includes an upper detector housing and a lower detector housing that are mechanically sealed together.

[0017] The partition is disposed inside the lower detector housing;

[0018] The lower detector housing has mounting holes for installing the data output module interface on the side near the signal transmission space.

[0019] Furthermore, the data extraction module is embedded within the signal transmission space and connected to the silicon photomultiplier tube via a signal line, with its interface located within a mounting hole. The data extraction module includes, but is not limited to, BNC data interfaces, USB data interfaces, and Type-C data interfaces. The data extraction module is fixed to the lower detector housing using mechanical mechanisms and water- and oxygen-resistant structural adhesive. The data extraction module can then be connected to different data processing systems according to actual usage requirements, including, but not limited to, energy spectrum testing systems and pulse waveform discrimination (PSD) systems, capable of simultaneously detecting and distinguishing neutron and gamma signals.

[0020] Furthermore, the outer shape of the crystal fixing inner shell is the same as that of the signal capture space, and the inner cavity is cylindrical, which includes an upper crystal fixing inner shell and a lower crystal fixing inner shell that are sealed and connected by a fastening assembly.

[0021] The top of the lower crystal fixing inner shell is provided with an annular groove, and the bottom of the upper crystal fixing inner shell is provided with a matching convex ring.

[0022] The mounting position is provided on the lower crystal fixing inner shell.

[0023] Furthermore, the crystal reflective layer is cylindrical in shape and includes an upper reflective layer and a lower reflective layer.

[0024] The reflective layers on the upper and lower parts of the crystal have uniform thicknesses of 0.5-2 mm.

[0025] The notch is located on the lower reflective layer of the crystal.

[0026] Furthermore, the detector crystal is cylindrical in shape, with a flat surface cut out on its side as the light-emitting surface. The thickness of the detector crystal is 6-10 mm, and the diameter is 25-75 mm. Because the thickness affects the absorption of slow neutrons, the thickness of the crystal needs to be greater than or equal to 6 mm to absorb 85-90% of the slow neutrons (that is, 85-90% of the slow neutrons transmitted through the crystal can be absorbed by the crystal). However, the thickness is not necessarily better the higher it is. In order to meet the requirements of product miniaturization and portability, the maximum thickness of the crystal is 10 mm.

[0027] The length of the light-emitting surface is 1.5-3 times the thickness of the detector crystal;

[0028] When using the above-mentioned detection crystal, each surface needs to be polished with sandpaper, with a grit of 1000-10000.

[0029] Furthermore, the light-receiving surface of the silicon photomultiplier tube is the same size as the light-emitting surface of the detector crystal, and the silicon photomultiplier tube is optically coupled to the light-emitting surface of the detector crystal through silicone oil or silicone.

[0030] Furthermore, the upper detector housing and the lower detector housing are reinforced and connected by an adhesive that can isolate water and oxygen;

[0031] The upper crystal fixing inner shell, the lower crystal fixing inner shell, and the fastening assembly are bonded together by an adhesive (such as epoxy adhesive) that can isolate water and oxygen.

[0032] Furthermore, the Li element in the Li-based potassium cryolite crystal... 6 The enrichment of Li isotopes is 93-98%.

[0033] Furthermore, the Li-based potassium cryolite crystals are Cs₂LiYCl₆:Ce(CLYC), Cs₂LiLaBr₆:Ce(CLLB), and Cs₂LiLaCl₆. x Br (6-x) :Ce(CLLBC).

[0034] Furthermore, the material of the crystal reflective layer is polytetrafluoroethylene;

[0035] The material of the crystal fixing inner shell is polyethylene;

[0036] The detector housing is made of aluminum alloy, stainless steel, titanium alloy, or hard plastic (such as ABS).

[0037] Because visible light has high reflectivity in the 250-450nm range; gamma transmittance is density-dependent, with higher density resulting in lower transmittance; therefore, materials with lower density should be used to maximize gamma transmittance. Neutrons require more hydrogen atoms to moderate, necessitating more organic materials for neutron moderation. Since plastics have lower density than metals, this design allows for the use of high-density polytetrafluoroethylene (PTFE) for the crystal reflective layer, which offers high visible light reflectivity at an acceptable density. Polyethylene is chosen for the crystal mounting shell due to its relatively high hydrogen content among common plastics. The detector housing is selected based on the requirements of corrosion resistance and good processability.

[0038] Advantages of this utility model:

[0039] 1. The detection crystal of this invention uses a Li-based potassium cryolite-type crystal capable of simultaneously detecting neutrons and gamma rays. It possesses excellent neutron and gamma ray discrimination capabilities and good spectral analysis capabilities, avoiding the need for large-size... 3The He gas detector ensures excellent energy spectrum testing and nuclide analysis capabilities. Simulations have shown that a 6-10 mm thick Li-based potassium cryolite-like crystal can effectively absorb axially incident neutron and gamma signals. Reducing the crystal thickness to 6-10 mm can decrease the detector's size and mass, significantly lowering its cost. Furthermore, using a silicon photomultiplier tube (SiPM) instead of a traditional photomultiplier tube (PMT) to convert the optical signal into an electrical signal saves on voltage amplification circuitry and reduces power consumption, further reducing the size and mass of the detection system. Additionally, traditional SiPMs are typically placed on the surface of the crystal to detect optical signals, following the usage path of traditional PMTs. The SiPM and its circuitry significantly increase the detector's size. This invention, however, demonstrates that placing the SiPM on the cut and polished sidewall of a sheet-like Li-based potassium cryolite crystal can also achieve effective detection, effectively reducing the detector's size.

[0040] 2. This utility model achieves the encapsulation of hygroscopic Li-based potassium cryolite crystals through the sealing of the detector itself, avoiding structural redundancy and volume increase caused by secondary encapsulation design.

[0041] 3. This invention achieves neutron and gamma detection functions using a single Li-based potassium cryolite crystal, and significantly reduces the size and weight of the detection system, thus meeting the requirements for miniaturization and portability of neutron and gamma detectors. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the detector's disassembled state in an embodiment of this utility model. Figure 1 ;

[0043] Figure 2 This is a schematic diagram of the detector's disassembled state in an embodiment of this utility model. Figure 2 ;

[0044] Figure 3 This is a schematic diagram of the detector assembly state in an embodiment of the present utility model;

[0045] Figure 4 The neutron and gamma energy spectra measured by the detector in this embodiment of the present invention are shown.

[0046] Figure 5 This is a PSD image of the neutron and gamma discrimination of the detector in the embodiment of this utility model;

[0047] The attached figures are labeled as follows:

[0048] 100 - Li-based potassium cryolite crystal; 200 - Silicon photomultiplier tube; 301 - Upper reflective layer of crystal; 302 - Lower reflective layer of crystal; 401 - Upper crystal fixing inner shell; 402 - Lower crystal fixing inner shell; 403 - Screw; 501 - Upper detector shell; 502 - Lower detector shell; 600 - Data output module. Detailed Implementation

[0049] The key to this invention's design of a miniaturized neutron and gamma detector device lies in:

[0050] 1. Selection 6 Li-based potassium cryolite crystals with Li isotope enrichment of 93-98%, including but not limited to Cs₂LiYCl₆:Ce(CLYC), Cs₂LiLaBr₆:Ce(CLLB), and Cs₂LiLaClxBr₆. (6-x) Ce (CLLBC) crystal. The crystal is cylindrical with a thickness of 6-10mm and a diameter of 25-75mm. A flat surface is cut out from the side of the crystal cylinder as the light-emitting surface, and the length of the light-emitting surface is 1.5-3 times the thickness of the crystal. All surfaces of the crystal are polished using 1000-10000 grit sandpaper.

[0051] 2. Except for the light-emitting surface, the rest of the crystal is tightly covered with a reflective layer made of polytetrafluoroethylene (PTFE) material, consisting of an upper reflective layer and a lower reflective layer. The reflective layer has a uniform thickness of 0.5-2mm in each part.

[0052] 3. The light-receiving surface of the silicon photomultiplier tube is the same size as the light-emitting surface of the crystal; silicone oil or silicone gel is used to couple the silicon photomultiplier tube to the light-emitting surface of the crystal.

[0053] 4. The crystal, which is wrapped with the reflective layer, is fixed by three parts: an upper crystal fixing shell, a lower crystal fixing shell, and screws, all made of polyethylene plastic. Epoxy glue is used to bond the upper crystal fixing shell, the lower crystal fixing shell, and the screws together to isolate water and oxygen.

[0054] 5. The upper and lower detector housings are used to fix the crystal fixing shell and the silicon photomultiplier tube. The signal line from the silicon photomultiplier tube is led out through the signal line guide groove of the lower detector housing partition. The upper and lower detector housings are connected by a mechanical structure and reinforced with structural adhesive that can isolate water and oxygen.

[0055] 6. Embed the data extraction module on the lower detector housing, near the silicon photomultiplier tube, and connect it to the silicon photomultiplier tube via a signal line; the data extraction module includes, but is not limited to: BNC data interface, USB data interface, and Type-C data interface; the data extraction module is fixed to the lower detector housing using a mechanical mechanism and water- and oxygen-isolated structural adhesive.

[0056] 7. After the data extraction module is connected, different data processing systems can be connected according to actual usage requirements, including but not limited to energy spectrum testing systems and pulse waveform discrimination (PSD) systems, which can simultaneously detect and distinguish neutron and gamma signals.

[0057] The embodiments of this utility model are described in detail below. These embodiments are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0058] like Figures 1-3 As shown, a miniaturized neutron and gamma detector device has actual dimensions of only 70*67*15mm. 3 This enables the miniaturization and portability of the detection equipment; its specific structure includes a detector shell, a crystal fixing inner shell, a crystal reflective layer, a detection crystal, a silicon photomultiplier tube, and a data output module.

[0059] The detector housing is made of corrosion-resistant and easily machinable materials, offering a wide range of options. The overall shape is rectangular, with a split structure consisting of an upper and lower detector housing. The lower detector housing is divided into two spaces by a partition: a signal acquisition space and a signal transmission space. Signal cable guides are provided on the partition. Mounting holes for data output module interfaces are located on the side of the lower detector housing closest to the signal transmission space. The upper and lower detector housings are mechanically sealed together and then reinforced with an adhesive that isolates them from water and oxygen.

[0060] The crystal mounting shell is made of polyethylene and has the same shape as the signal acquisition space. Its inner cavity is cylindrical and it is integrally positioned within the signal acquisition space, fitting snugly against the detector housing. The crystal mounting shell is a split structure, consisting of an upper crystal mounting shell and a lower crystal mounting shell connected by screws. The top of the lower crystal mounting shell has an annular groove, and the bottom of the upper crystal mounting shell has a corresponding convex ring. Furthermore, the lower crystal mounting shell has mounting positions for silicon photomultiplier tubes at positions corresponding to the signal line guide slots. The upper and lower crystal mounting shells, along with the screws, are bonded together with epoxy adhesive, which is effective against water and oxygen.

[0061] The reflective layer of the crystal is made of polytetrafluoroethylene and is cylindrical in shape. It is integrally fitted inside the crystal's inner shell and has a split structure, consisting of an upper reflective layer and a lower reflective layer. The reflective layers are uniformly 1mm thick. The lower reflective layer has a notch at the corresponding mounting position.

[0062] Selected detection crystal 6A Cs₂LiYCl₆:Ce (CLYC) crystal with a Li isotope enrichment of 95% was used. The crystal was cylindrical with a diameter of 51 mm and a thickness of 6 mm. A flat surface, 12 mm in length, was cut from the side of the crystal cylinder to serve as the light-emitting surface. All surfaces of the crystal were polished to 5000 grit using sandpaper. Except for the light-emitting surface, the rest of the detector crystal was tightly covered by upper and lower reflective layers.

[0063] The silicon photomultiplier tube is installed at the mounting position of the crystal's fixed inner shell. Its light receiving surface is 12mm long and 6mm wide, and it is optically coupled to the light emitting surface of the detector crystal through silicone oil.

[0064] The data extraction module is embedded within the detector housing, with its interface located in a mounting hole. It is secured by mechanical mechanisms and structural adhesive, and is protected from water and oxygen. The data extraction module uses a Type-C data interface and connects to the silicon photomultiplier tube via a signal line. Its rear end is connected to an energy spectrum testing system and a pulse waveform discrimination (PSD) system. Neutron and gamma detection tests were conducted using a 137Cs gamma radiation source and an AmBe neutron radiation source. This miniaturized neutron and gamma detector device can simultaneously detect and distinguish between neutron and gamma signals.

[0065] The neutron and gamma spectra measured by the energy spectrum testing system are as follows: Figure 4 The neutron and gamma peaks are distinct, with high energy resolution; the neutron and gamma discrimination PSD images tested by the pulse waveform discrimination (PSD) system are shown below. Figure 5 It can be seen that there is a clear distinction between the neutron signal region and the gamma signal region, with a FoM as high as 3.72, which indicates that the neutron and gamma signals are completely separated.

[0066] In summary, it can be determined that the device of this invention can realize the functions of neutron and gamma detection, and significantly reduce the size and weight of the detection system, thus meeting the requirements of miniaturization and portability of neutron and gamma detectors.

[0067] The above description is only a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model.

Claims

1. A miniaturized neutron and gamma detector, characterized in that: It includes a detector housing, a crystal fixing inner housing, a crystal reflective layer, a detector crystal, a silicon photomultiplier tube, and a data output module; The detector housing has a split structure, with its interior divided into two spaces by a partition: a signal acquisition space and a signal transmission space; the partition is provided with signal line guide grooves. The crystal fixing inner shell has an upper and lower split structure, which is set in the signal acquisition space and fits against the detector outer shell; the lower split of the crystal fixing inner shell has a mounting position corresponding to the position of the signal line guide groove. The crystal reflective layer has an upper and lower split structure, which is fitted inside the crystal fixing inner shell; the lower split of the crystal reflective layer has a notch corresponding to the mounting position; The detection crystal is bonded to the crystal reflective layer, with its light-emitting surface facing the notch; the detection crystal is made of Li-based potassium cryolite-type crystal. The silicon photomultiplier tube is installed at the mounting position of the crystal fixed inner shell, and its light receiving surface is optically coupled to the light emitting surface of the detector crystal. The data extraction module is located in the signal transmission space and is connected to the silicon photomultiplier tube via a signal line; The detector crystal converts the absorbed neutron and gamma signals into visible light signals. The crystal reflective layer reflects and transmits the visible light signals to the silicon photomultiplier tube. The silicon photomultiplier tube converts the visible light signals into electrical signals. The data extraction module outputs the electrical signals to obtain the neutron and gamma signals.

2. The miniaturized neutron and gamma detector according to claim 1, characterized in that: The detector housing is rectangular in shape and includes an upper detector housing and a lower detector housing that are mechanically sealed together. The partition is disposed inside the lower detector housing; The lower detector housing has mounting holes for installing the data output module interface on the side near the signal transmission space.

3. The miniaturized neutron and gamma detector according to claim 2, characterized in that: The outer shape of the crystal fixing inner shell is the same as that of the signal capture space. The inner cavity is cylindrical and includes an upper crystal fixing inner shell and a lower crystal fixing inner shell that are sealed and connected by a fastening assembly. The top of the lower crystal fixing inner shell is provided with an annular groove, and the bottom of the upper crystal fixing inner shell is provided with a matching convex ring. The mounting position is provided on the lower crystal fixing inner shell.

4. The miniaturized neutron and gamma detector according to claim 3, characterized in that: The crystal reflective layer is cylindrical in shape and includes an upper reflective layer and a lower reflective layer. The reflective layers on the upper and lower parts of the crystal have uniform thicknesses of 0.5-2 mm. The notch is located on the lower reflective layer of the crystal.

5. The miniaturized neutron and gamma detector according to claim 4, characterized in that: The detection crystal is cylindrical in shape, with a thickness of 6-10 mm and a diameter of 25-75 mm; The length of the light-emitting surface is 1.5-3 times the thickness of the detector crystal.

6. The miniaturized neutron and gamma detector according to claim 5, characterized in that: The light-receiving surface of the silicon photomultiplier tube is the same size as the light-emitting surface of the detector crystal, and the silicon photomultiplier tube is optically coupled to the light-emitting surface of the detector crystal through silicone oil or silicone.

7. The miniaturized neutron and gamma detector according to claim 6, characterized in that: The upper detector housing and the lower detector housing are reinforced and connected by an adhesive that can isolate water and oxygen; The upper crystal fixing inner shell, the lower crystal fixing inner shell, and the fastening assembly are bonded together with an adhesive that can isolate water and oxygen.

8. The miniaturized neutron and gamma detector according to any one of claims 1-7, characterized in that: The Li element in the Li-based potassium cryolite crystals 6 The enrichment of Li isotopes is 93-98%.

9. The miniaturized neutron and gamma detector according to claim 8, characterized in that: The Li-based potassium cryolite crystals are Cs₂LiYCl₆:Ce, Cs₂LiLaBr₆:Ce, and Cs₂LiLaCl₆. x Br (6-x) :Ce.

10. The miniaturized neutron and gamma detector according to claim 9, characterized in that: The material of the crystal reflective layer is polytetrafluoroethylene; The material of the crystal fixing inner shell is polyethylene; The detector housing is made of aluminum alloy, stainless steel, titanium alloy, or hard plastic.

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