Two-dimensional position sensitive neutron detector based on light attenuation intensity adjustment

Abstract

The invention relates to the technical field of neutron position sensitive detectors, and discloses a two-dimensional position sensitive neutron detector based on light attenuation intensity adjustment, which comprises a scintillation crystal, a two-dimensional optical attenuator, a light guide and a photoelectric conversion device, and comprises the following steps: S1, collimated neutron rays hit on the whole scintillation crystal, after neutrons are captured, secondary particles generated by nuclear reaction can deposit energy in the scintillation crystal, some atoms or molecules in the scintillation crystal are excited to a higher energy level, then, when the atoms or molecules in the excited state return to the ground state, energy can be released, and part of energy is released in the form of visible light. The relation between the emergent light intensity and the neutron incidence position is formed through attenuation of the optical attenuators with different attenuation coefficients, and the method has the advantages of being real-time and simple in reconstruction, low in equipment cost and the like and is suitable for neutron imaging fields such as thermal neutron imaging and cold neutron imaging.

Description

Technical Field

[0001] The invention relates to the technical field of neutron position sensitive detectors, in particular to a two-dimensional position sensitive neutron detector based on light attenuation intensity adjustment. Background Art

[0002] Reconstructing the location of radioactive sources is crucial for responding to radiation-related incidents. In the event of a nuclear accident or radiation leak, accurately determining the location of the radioactive source can help relevant agencies take emergency measures in a timely manner, such as evacuating residents, restricting access to areas, and providing medical assistance. At the same time, reconstructing the location of radioactive sources is also crucial for environmental protection and nuclear safety. Timely detection and location of radioactive material leaks can minimize the impact of pollution on the surrounding environment, and in the operation of nuclear facilities, accurate reconstruction of the location of radioactive sources helps monitor the flow of nuclear materials and prevent nuclear materials from being illegally obtained or abused. However, at present, the research on reconstructing the location of gamma radiation sources is relatively mature. In fact, the harm of neutrons to the human body cannot be underestimated, and neutron position reconstruction technology is also gradually developing. Therefore, the continuous development and improvement of neutron position reconstruction technology is of great significance to protecting public health, environmental safety and nuclear safety.

[0003] At present, the scintillation crystals used for neutron position reconstruction are required to have good uniformity, so that relatively uniform emitted visible light can be obtained. Then, most of them will use multi-channel photoelectric conversion devices to collect visible light, and finally use related reconstruction algorithms to reconstruct the neutron position. However, this requires relatively good uniformity of the scintillation crystals, and the area of ​​the entire system will be relatively large, the cost will be relatively high, and the quality of the reconstruction algorithm is also crucial to neutron position reconstruction.

[0004] To this end, we urgently need a two-dimensional position-sensitive neutron detector based on light attenuation intensity regulation. Summary of the invention

[0005] The purpose of the present invention is to provide a two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment, which solves the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment, comprising a scintillation crystal, a two-dimensional light attenuator, a light guide and a photoelectric conversion device, comprising the following steps:

[0007] S1: After the collimation, the neutron rays hit the whole scintillation crystal. After the neutrons are captured, the secondary particles produced by the nuclear reaction will deposit energy inside the scintillation crystal. Some atoms or molecules in the scintillation crystal are excited to a higher energy level. Then, when these excited atoms or molecules return to the ground state, they will release energy, part of which is released in the form of visible light.

[0008] S2: Visible light generated at different positions will be emitted as visible light of different intensities after passing through the two-dimensional optical attenuator;

[0009] S3: The light guide efficiently transmits the visible light passing through the optical attenuator to the single-channel photoelectric conversion device, and measures the intensity of the emitted visible light;

[0010] S4: Measure the visible light intensity measured by the photoelectric conversion device when neutrons are incident from different positions, and form a calibration curve of the intensity of the emitted visible light and the neutron incident position;

[0011] S5: Based on the obtained visible light intensity and calibration curve, the incident position of any neutron can be reconstructed.

[0012] Preferably, in step S1, neutrons react with specific nuclei in the scintillation crystal material to convert the energy of the neutrons into visible light, which is then detected by the detector.

[0013] Preferably, in step S2, the light attenuator covers the entire surface of the scintillation crystal, and its attenuation coefficient varies in a two-dimensional plane, so that the intensity of visible light emitted from each position is different.

[0014] Preferably, in the step S3, all visible light signals passing through the optical attenuator are converged onto a single-channel photoelectric conversion device through a light guide.

[0015] Preferably, in the step S4, the photoelectric conversion device reads all visible light signals and finally measures the visible light. Neutrons incident at different positions will produce different visible light signal intensities, and finally a calibration curve of the measured visible light intensity and the neutron incident position is formed.

[0016] Preferably, in step S5, when the photoelectric conversion device measures a visible light signal of a certain intensity, the position of the incident neutron can be determined by matching the light intensity with a pre-calibrated calibration curve.

[0017] The present invention provides a two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment has the following beneficial effects:

[0018] The present invention uses optical attenuators with different attenuation coefficients to form a relationship between the intensity of the outgoing light and the neutron incident position. This method has the advantages of real-time reconstruction, simplicity, and low equipment cost, and is suitable for neutron imaging fields such as thermal neutron and cold neutron imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the entire two-dimensional position-sensitive neutron detector system of the present invention;

[0020] Figure 2 Schematic diagram of attenuation coefficients in different regions of the two-dimensional optical attenuator of the present invention. DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0022] A preferred embodiment of the two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment provided by the present invention is as follows: Figure 1 to Figure 2 As shown:

[0023] A two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment includes a scintillation crystal, a two-dimensional light attenuator, a light guide, and a photoelectric conversion device, and includes the following steps:

[0024] S1: After the collimation, the neutron beam hits the whole scintillation crystal. After the neutron is captured, the secondary particles produced by the nuclear reaction will deposit energy inside the scintillation crystal. Some atoms or molecules in the scintillation crystal are excited to a higher energy level. Then, when these excited atoms or molecules return to the ground state, they will release energy, part of which is released in the form of visible light. Here, the neutron reacts with the specific nuclei in the scintillation crystal material, converting the neutron's energy into visible light, which is then detected by the detector;

[0025] During the implementation process, the scintillation crystal selected is the common GS20 glass (containing 95% Li-6) on the market. The collimated neutron rays will mainly react with the Li-6 in the GS20 (n, α) to produce tritium and α particles with high kinetic energy. When these particles move in the Li-6 glass material, they will interact with the atoms and electrons in the glass, causing the energy to be gradually lost through multiple inelastic collisions. These inelastic collisions cause the excitation and relaxation process of the electron energy level, and finally convert the kinetic energy into light energy. When the electron returns to a lower energy state, it will emit photons, which form visible light.

[0026] S2: Visible light generated at different positions will be emitted as visible light of different intensities after passing through the two-dimensional optical attenuator. Here, the optical attenuator covers the entire surface of the scintillation crystal, and its attenuation coefficient changes on the two-dimensional plane, so that the intensity of visible light emitted at each position is different;

[0027] In the implementation process, the two-dimensional optical attenuator is evenly covered on the entire GS20 glass. The thickness of the optical attenuator is different at different positions, that is, the attenuation coefficient at different positions is different (for example, the attenuation coefficient of 90% means that the intensity of the emitted light in this area is 10% of the original intensity). The optical attenuator is divided into 3×3 areas. Figure 2 The attenuation coefficient within each region is shown;

[0028] S3: The light guide efficiently transmits the visible light passing through the optical attenuator to the single-channel photoelectric conversion device, and measures the intensity of the emitted visible light. Here, all visible light signals passing through the optical attenuator are converged to the single-channel photoelectric conversion device through the light guide;

[0029] In the implementation process, the light guide transmits the visible light after passing through the two-dimensional optical attenuator to the single-channel PMT;

[0030] S4: When neutrons are incident from different positions, the intensity of visible light measured by the photoelectric conversion device is measured to form a calibration curve of the intensity of the emitted visible light and the position of the neutron incident. Here, the photoelectric conversion device will read all visible light signals and finally measure the visible light. Neutrons incident from different positions will produce different visible light signal intensities, and finally form a calibration curve of the measured visible light intensity and the neutron incident position.

[0031] During the implementation process, when visible light enters the PMT, the photon will hit the photosensitive cathode of the PMT and stimulate electrons. The electrons released by the photosensitive cathode are accelerated by the accelerator electric field and pass through the electron multiplier. When passing through each multiplier, the electrons will release more secondary electrons, thereby realizing the electron multiplication effect. Finally, all electrons are collected and amplified at the anode of the PMT to form an overall output electrical signal, which is then transmitted to the signal processing system. The amplitude of the electrical signal received by the PMT is proportional to the intensity of the incident light. Therefore, the signal processing system can obtain the incident position of the neutron based on information such as the amplitude of the PMT signal. Experiments with different incident positions of neutrons and visible light intensities are conducted in advance. Assuming that a thermal neutron is incident from a certain position, it will react with the Li-6 in the GS20 glass (light yield is approximately 1460 Photons / MeV) to deposit approximately 4.78 MeV of energy. Considering the quenching effect, each thermal neutron absorbed by the GS20 glass generates approximately 5000 photons. Finally, a calibration curve table is obtained. Table 1 shows the results.

[0032] Neutron incident area Measured visible light intensity 1 500 2 1000 3 1500 4 2000 5 2500 6 3000 7 3500 8 4000 9 4500

[0033] Table 1

[0034] S5: Based on the obtained visible light intensity and calibration curve, the incident position of any neutron can be reconstructed. Here, when the photoelectric conversion device measures a visible light signal of a certain intensity, the position of the incident neutron can be determined by matching the light intensity with the pre-calibrated calibration curve;

[0035] During the implementation process, if the visible light intensity measured when a thermal neutron is incident from a certain position is 550, according to the comparison table, it can be obtained that the neutron is incident from area 1; if the obtained visible light intensity is 4260, it means that it is incident approximately in the middle of areas 8 and 9, and the neutron position can be reconstructed based on the results later.

[0036] The above description is only an illustrative specific implementation mode of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention. It should also be noted that the various components of the present invention are not limited to the above-mentioned overall application. The various technical features described in the specification of the present invention can be selected one by one or multiple ones can be selected and used in combination according to actual needs. Therefore, the present invention should naturally cover other combinations and specific applications related to the invention point of this case.

Claims

1. A two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment, comprising a scintillation crystal, a two-dimensional light attenuator, a light guide and a photoelectric conversion device, characterized in that: The following steps are involved: S1: After the collimation, the neutron rays hit the whole scintillation crystal. After the neutrons are captured, the secondary particles produced by the nuclear reaction will deposit energy inside the scintillation crystal. Some atoms or molecules in the scintillation crystal are excited to a higher energy level. Then, when these excited atoms or molecules return to the ground state, they will release energy, part of which is released in the form of visible light. S2: Visible light generated at different positions will be emitted as visible light of different intensities after passing through the two-dimensional optical attenuator; S3: The light guide efficiently transmits the visible light passing through the optical attenuator to the single-channel photoelectric conversion device, and measures the intensity of the emitted visible light; S4: Measure the visible light intensity measured by the photoelectric conversion device when neutrons are incident from different positions, and form a calibration curve of the intensity of the emitted visible light and the neutron incident position; S5: Based on the obtained visible light intensity and calibration curve, the incident position of any neutron can be reconstructed.

2. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment according to claim 1, characterized in that: In step S1, neutrons react with specific nuclei in the scintillation crystal material, converting the neutrons' energy into visible light, which is then detected by the detector.

3. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment according to claim 1, characterized in that: In step S2, the light attenuator covers the entire surface of the scintillation crystal, and its attenuation coefficient varies in a two-dimensional plane, so that the intensity of visible light emitted from each position is different.

4. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment according to claim 1, characterized in that: In step S3, all visible light signals passing through the optical attenuator are converged onto the single-channel photoelectric conversion device through the optical guide.

5. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment according to claim 1, characterized in that: In step S4, the photoelectric conversion device will read all visible light signals and finally measure the visible light. Neutrons incident at different positions will produce different visible light signal intensities, and finally a calibration curve of the measured visible light intensity and the neutron incident position is formed.

6. The two-dimensional position-sensitive neutron detector based on light attenuation intensity adjustment according to claim 1, characterized in that: In step S5, when the photoelectric conversion device measures a visible light signal of a certain intensity, the position of the incident neutron can be determined by matching the light intensity with a pre-calibrated calibration curve.

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