A deep space radiation neutron detector

Abstract

The application discloses a deep space radiation neutron detector and belongs to the technical field of nuclear radiation detection. The gadolinium film captures slow neutrons to generate multi-state particles, the TPC module detects the three-dimensional tracks and energy of the inner conversion electrons and Auger electrons, the energy quantifier module detects the energy of the prompt gamma rays, and efficient and high-precision neutron detection is realized through electron-gamma coincidence measurement. The application adopts gadolinium to replace the scarce 3 He, solves the problems of low efficiency and high cost of the traditional detector, combines the track reconstruction capability of the TPC module and the high energy resolution of the energy quantifier, significantly improves the signal-to-noise ratio and detection sensitivity of the neutron signal, and is suitable for fields such as deep space exploration and nuclear radiation monitoring.

Description

Technical Field

[0001] This invention belongs to the field of nuclear radiation detection technology, specifically relating to a high-efficiency neutron detector for deep space exploration, particularly suitable for detecting the abundance of hydrogen / water ice on planetary surfaces, analyzing nuclide distribution, and monitoring the space radiation environment. This detector is based on a composite detection scheme using a gadolinium thin-film conversion layer, a time projection chamber (TPC) module, and a gamma calorimeter. It achieves efficient detection and background suppression of slow neutron signals through electron-gamma coincidence measurements, and can be applied to deep space exploration, nuclear safety monitoring, materials analysis, and other fields. Background Technology

[0002] High-energy cosmic ray particles interact with planetary media to produce fast neutrons, which are then slowed down by scattering into thermal / slow neutrons. Measuring their energy spectrum and flux allows for non-destructive inversion of hydrogen / water ice abundance, volatile matter distribution, and regolith density and temperature at depths below the Earth's surface. This data serves resource exploration and landing site selection on the Moon, Mars, and other small celestial bodies, and has significant value for deep space engineering applications. Furthermore, with the popularization of slow neutron detection technology, its applications have expanded to multiple fields, including cutting-edge science, materials science, and energy.

[0003] Current neutron detection relies on a conversion-trapping reaction to convert neutrons into a measurable signal; therefore, the converter is a key structural element. Nuclides with high slow neutron cross sections include... 3 He 10 B 6 Li, 155 Gd, 157 Gd, etc. 3 Helium, with its large thermal neutron cross-section and insensitivity to environmental gamma, has long been considered the standard detection medium. However, due to high demand in fields such as homeland security, nuclear nonproliferation, cryogenic applications, spallation neutron sources, and magnetic resonance imaging, it remains in short supply and expensive. 10 B or 6 Li compounds, as alternatives to the conversion medium, suffer from limitations in achieving high intrinsic detection efficiency due to the long mean free path of neutrons and the short range of charged particles in the reaction yield, restricting thickness optimization. Furthermore, as a low-density gas... 3 He is less constrained by this. Gadolinium (Gd) has an extremely high capture cross section and is often used for highly sensitive neutron detection, but after capture, it produces multiple internal conversion electrons and a set of gamma rays, with many and complex final states, which are easily affected by the ambient gamma background.

[0004] The next-generation neutron detector uses gadolinium as the neutron conversion layer, combining an advanced time projection chamber (TPC) module with a high spatial / energy resolution cadmium zinc telluride (CZT) calorimeter module for coincidence detection. This approach maintains extremely high detection efficiency while accurately reconstructing the final-state electron energy and emission vertex using information such as the deposition energy and track length of the TPC module. This reconstruction coincides with the cascaded gamma signal measured by the CZT module, achieving high-precision and high-efficiency reconstruction of slow neutron signals. Furthermore, based on the differentiated responses of different particles in the TPC module, pattern recognition can significantly suppress the environmental gamma background. Summary of the Invention

[0005] Traditional slow neutron detection techniques primarily capture neutrons using high-cross-section nuclides and convert them into charged particles or gamma signals. These signals are then read out by gas proportional counters, scintillators, semiconductor or microstructure gas detectors, etc., to achieve counting, energy spectrum, and imaging detection. A trade-off is made between efficiency, background suppression, and manufacturing cost. Existing technologies include: employing... 3 Proportional counter tube for He or BF3 gas, doped 10 Detection schemes for element B include plastic scintillator detectors and detectors with conversion layers. Proportional transistor technology is the most mature approach. 3 He gas medium has high sensitivity for neutron detection, but 3 Helium resources are scarce and expensive; if BF3 gas is used, the cost is relatively controllable, but BF3 is toxic and corrosive, placing higher demands on sealing, materials, and safety. Secondly, because the detection cross-section is relatively lower... 3 He gas requires a larger detection area, making it difficult to deploy in space missions; and proportional counter technology can only acquire counts and cannot identify background signals such as low-energy gamma and charged particles, so it must rely on shielding and anti-coincidence detectors for auxiliary detection.

[0006] The plastic scintillator (PSS) doping scheme introduces boron-containing elements and other impurities with high slow neutron capture cross-sections into a plastic scintillator to achieve slow neutron capture. Its advantages include the ability to distinguish between neutron and gamma signals based on the shape of the PSS pulse, flexible fabrication, high mechanical strength, and large-area production capabilities. However, boron doping reduces light yield and transmittance, weakens the detector signal, and degrades resolution. Furthermore, the boron-doped neutron capture cross-section is lower than that of the plastic scintillator. 3 To achieve higher detection efficiency, doping concentration, detector thickness, and scintillator luminescence efficiency are mutually constrained.

[0007] The conversion layer plus semiconductor / scintillator detector coupling scheme utilizes a combination of... 10 B 6 Li or gadolinium ( 155 Gd, 157The Gd conversion layer captures slow neutrons and produces gamma rays and alpha charged particles. Neutrons are detected by detecting the secondary final state particles produced after capture. 10 B 6 Due to its relatively low neutron capture cross section, Li typically requires multiple conversion layers to improve detection efficiency. However, increasing the thickness reduces the detection capability of secondary charged particle signals, thus lowering neutron detection efficiency. Gadolinium, on the other hand, has an extremely high capture cross section, but its capture results in multiple gamma-ray cascaded final states and multiple internal conversion electrons. Due to the complex composition of these final states, coincidence detectors are usually placed on both sides of the gadolinium layer, forming a sandwich structure to improve the coincidence detection efficiency of multiple final state particles. Furthermore, due to gadolinium's high atomic number (Z=64), it has a very high probability of interacting with gamma rays. Gadolinium's high gamma-ray interaction cross section leads to an enhanced gamma-ray background signal, resulting in a deterioration in the neutron detection signal-to-noise ratio.

[0008] 3 While Hexane (He), as a traditional neutron detection medium, has a large thermal neutron trapping cross section and is insensitive to background gamma rays, its widespread applications in fields such as homeland security, cryogenics, and magnetic resonance imaging have led to a long-term shortage, necessitating the search for alternative materials. The shortcomings of existing alternatives include: 10 B or 6 Li compound coating schemes, due to the long mean free path of neutrons and the short range of charged particles, cannot achieve high intrinsic detection efficiency. This invention uses gadolinium (Gd) as the neutron trapping material, possessing an extremely high thermal neutron trapping cross-section and Q value (approximately 8 MeV), thus solving the aforementioned efficiency problem. Furthermore, this invention, based on advanced microstructure gas detection technology—time projection chambers—combined with semiconductor detectors or high-resolution scintillator calorimeter coincidence measurements, can achieve event-level neutron / background signal identification and reconstruction of trapped multi-final-state particles.

[0009] The technical solution of the present invention is as follows:

[0010] A deep-space radiation neutron detector, comprising:

[0011] Gadolinium thin film conversion layer, used to capture slow neutrons and generate multiple final state particles;

[0012] A polyethylene electron shielding module, installed close to a gadolinium film, is used to shield final-state electrons;

[0013] The Time Projection Chamber (TPC) module is used to detect the three-dimensional tracks and energies of internal conversion electrons and Auger electrons produced after gadolinium captures a neutron;

[0014] The gamma-ray detector module is used to detect the energy of the transient gamma rays produced after gadolinium captures a neutron;

[0015] The Time Projection Chamber (TPC) module and the calorimeter module achieve neutron detection through signal coincidence.

[0016] In the above technical solution, the gadolinium film is gadolinium metal with a thickness of no more than 0.1 mm, or a gadolinium layer with a thickness of 1-10 μm is deposited on a substrate material.

[0017] In the above technical solution, the TPC module adopts an air-tight design, and the sealing material is stainless steel, titanium alloy, aluminum alloy or carbon fiber, and the working air pressure is 0.1-3 bar.

[0018] In the above technical solution, the TPC module uses a microstructured gas detector (MPGD) as the signal readout detector, including a gas electron multiplier (GEM / THGEM), a micromegagas detector, a dual-layer micromegagas detector (DMM), or a resistive microwell detector (μRWELL).

[0019] In the above technical solution, the working gas of the TPC module is a mixture of argon, neon, or xenon with polyatomic molecular gases, or a single-component gas such as carbon tetrafluoride or methane.

[0020] In the above technical solution, the calorimeter module is a block scintillator detector, and the scintillator material is LaBr3:Ce, LaBr3, NaI or CsI, coupled with a silicon photomultiplier tube (SiPM) or photomultiplier tube (PMT) for readout.

[0021] In the above technical solution, the calorimeter module is a pixelated semiconductor detector, the material of which is CdZnTe, CdTe or perovskite, the pixel unit size is 0.1-5 mm, and the thickness is 5-20 mm.

[0022] In the above technical solution, the thickness of the polyethylene electronic shielding module is 300-400 μm.

[0023] In the above technical solution, the readout structure of the TPC module is a two-dimensional intersecting bar or pixel array with a spacing of 0.1-10 mm.

[0024] In the above technical solution, the spatial positions of the calorimeter module and the TPC module are matched, and the neutron signal and the background gamma signal are distinguished through electron-gamma coincidence measurement.

[0025] Beneficial effects:

[0026] Compared to traditional 3 In this invention, gadolinium is used as the neutron trapping material in a neutron detection medium. It possesses an extremely high thermal neutron trapping cross-section and Q value, exhibiting characteristics of large signal amplitude and high detection efficiency, effectively solving the problem of... 3He resource shortage problem and 10 B 6 The low efficiency of Li neutron detection media is a problem. This invention combines advanced gas detector (TPC) technology based on a closed-gas detector with high efficiency and high precision measurement of thermal neutrons through final-state electron and gamma event coincidence measurements. Compared to existing gadolinium detection schemes, this invention not only distinguishes between event-level neutron and background gamma signals but also significantly reduces background interference, enabling accurate neutron signal identification. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a neutron detector.

[0028] Figure 2 Example of a TPC detector and its electronic structure.

[0029] Figure 3 Example of a calorimeter solution (I).

[0030] Figure 4 Example of a calorimeter solution (II).

[0031] Among them: 1 is the time projection chamber, 2 is the gadolinium film, 3 is polyethylene, 4 is the calorimeter, 5 is the signal connector, 6 is the MPGD detector, 7 is the low-pressure gas, 8 is the TPC field cage, 9 is the scintillator crystal, 10 is the silicon photomultiplier tube, 11 is the photomultiplier tube, 12 is the readout electronics, and 13 is the pixel semiconductor. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0033] Example

[0034] This invention proposes a novel ultra-high resolution neutron detector based on a gadolinium thin film 2, a time projection chamber 1, and a calorimeter 4, which includes the overall design of the detector, the selection of specific detection modules, and the implementation scheme.

[0035] A high-efficiency deep-space radiation neutron detector comprises a gadolinium thin film 2, polyethylene 3, a time projection chamber 1, and a calorimeter 4. Neutrons react with the gadolinium thin film 2 to produce various final-state gamma rays and electrons. The electron signal is detected by the time projection chamber 1, and the gamma signal is detected by the calorimeter 4. The coincidence of the two signals achieves high-efficiency neutron detection.

[0036] Overall structure and function: The detector mainly consists of a gadolinium thin film 2, polyethylene 3, a time projection chamber 1, and a calorimeter 4, such as Figure 1As shown. The gadolinium thin film 2 is gadolinium metal with a thickness generally not exceeding 0.1 mm, or a gadolinium layer with a thickness of 1-10 μm deposited on a substrate material. The film is closely attached to the inner side of the gas chamber of the time projection chamber 1 and polyethylene 3. Gadolinium metal, as a neutron trapping material, has an extremely high neutron trapping cross section and Q value. After trapping a neutron, it produces multiple gamma rays and final-state electrons. The polyethylene 3 is about 300-400 μm thick and is used to shield the final-state electrons. The gamma rays pass through the electron shield formed by the polyethylene 3, and the final energy is detected by the calorimeter 4. The electron events emitted to the calorimeter 4 are absorbed by the polyethylene 3, while the final-state electrons emitted towards the time projection chamber are detected by the time projection chamber. The electron tracks detected by the time projection chamber can reconstruct the reaction vertex, thereby determining the location of neutron trapping and distinguishing between neutrons and background signals. The calorimeter 4 can detect the energy of the characteristic gamma rays produced by the reaction, further determining that the event is a signal produced by gadolinium trapping a neutron.

[0037] Time projection room 1: A microstructured gas detector (MPGD detector 6) is used as the signal readout detector. Optional detectors include gas electron multipliers (GEM / THGEM), micromegagas, dual-layer micromegagas detectors (DMM), resistive microwell detectors (μRWELL), etc., in conjunction with corresponding low-noise multi-channel readout electronics 12, to realize the three-dimensional track and energy measurement of internal conversion electrons and Auger electrons emitted during the de-excitation process of gadolinium excited state.

[0038] like Figure 2 As shown, the time projection chamber 1 is installed on one side of the gadolinium thin film 2. The MPGD detector 6 uses two-dimensional crossbar readout or pixel readout, with the spacing between the readout bars or pixels typically ranging from 0.1 mm to 10 mm. The working gas is a low-pressure gas 7, usually 0.1-3 bar, and its composition is typically a mixture of inert gases such as argon, neon, and xenon, along with polyatomic gases. Optional polyatomic gases include carbon dioxide, isobutane, carbon tetrafluoride, methane, and ethane; single-component gases such as carbon tetrafluoride and methane can also be used. The TPC field cage 8 is composed of fine metal wires or strips, and typically employs a double-layer structure to improve electric field uniformity.

[0039] Calorimeter 4: Since this invention uses the coincidence measurement of final-state electrons and gamma signals to achieve slow neutron signal detection, the gamma calorimeter uses a block-shaped scintillator crystal 9 (1-2 readout channels, such as...). Figure 3As shown), such as LaBr3:Ce, LaBr3, NaI, CsI, etc., combined with silicon photomultiplier tubes 10 and their corresponding readout electronics 12, the energy of the transient gamma rays after gadolinium absorbs neutrons is measured. To achieve higher detection efficiency and energy resolution, the calorimeter uses a single scintillator, whose length and width dimensions must match the TPC module size, and its thickness is typically 5-10 cm. It is coupled with silicon photomultiplier tubes 10SiPM or 11PMT, etc., for photoelectric signal readout. Alternatively, a novel pixel semiconductor 13 or a scintillator array pixel semiconductor detector can be selected as the calorimeter, which can simultaneously achieve accurate measurement of gamma energy and position. These are typically CdZnTe or CdTe, with pixel unit sizes typically ranging from 0.1 mm to 10 mm and detector thicknesses from 5 mm to 20 mm. In practice, multiple units are usually spliced ​​together to achieve a larger sensitive area (e.g., ...). Figure 4 (As shown).

[0040] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A deep-space radiation neutron detector, characterized in that, include: Gadolinium thin film conversion layer, used to capture slow neutrons and generate multiple final state particles; A polyethylene electron shielding module, installed close to a gadolinium film, is used to shield final-state electrons; The time projection chamber module is used to detect the three-dimensional tracks and energies of internal conversion electrons and Auger electrons produced after gadolinium captures a neutron; The gamma-ray detector module is used to detect the energy of the transient gamma rays produced after gadolinium captures a neutron; The time projection chamber module and the calorimeter module achieve neutron detection through signal coincidence.

2. The detector as described in claim 1, characterized in that, The gadolinium film is gadolinium metal with a thickness not exceeding 0.1 mm, or a gadolinium layer with a thickness of 1-10 μm deposited on a substrate material.

3. The detector as described in claim 1, characterized in that, The TPC module adopts an airtight design, with sealing materials of stainless steel, titanium alloy, aluminum alloy or carbon fiber, and a working air pressure of 0.1-3 bar.

4. The detector as described in claim 1 or 3, characterized in that, The TPC module uses a microstructured gas detector as the signal readout detector, including a gas electron multiplier, a microgrid gas detector, a double-layer microgrid gas detector, or a resistive microwell detector.

5. The detector as described in claim 3, characterized in that, The working gas of the TPC module is a mixture of argon, neon, or xenon with polyatomic molecular gases, or a single-component gas such as carbon tetrafluoride or methane.

6. The detector as claimed in claim 1, characterized in that, The calorimeter module is a block scintillator detector, with the scintillator material being LaBr3:Ce, LaBr3, NaI, or CsI, coupled with a silicon photomultiplier tube or photomultiplier tube readout.

7. The detector as claimed in claim 1, characterized in that, The calorimeter module is a pixelated semiconductor detector made of CdZnTe, CdTe or perovskite, with a pixel unit size of 0.1-5 mm and a thickness of 5-20 mm.

8. The detector as claimed in claim 1, characterized in that, The thickness of the polyethylene electronic shielding module is 300-400 μm.

9. The detector as claimed in claim 1, characterized in that, The readout structure of the TPC module is a two-dimensional intersecting bar or pixel array with a spacing of 0.1-10 mm.

10. The detector as claimed in claim 1, characterized in that, The calorimeter module and the TPC module are spatially matched, and the neutron signal and the background gamma signal are distinguished through electron-gamma coincidence measurement.

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