Neutron-gamma mixed radiation screening method based on radiation response signal

Abstract

The invention discloses a neutron-gamma mixed radiation screening method based on a radiation response signal. The neutron-gamma mixed radiation screening method depends on a nano-coating CMOS sensor neutron measurement system. The neutron measurement system of the nano-coating CMOS sensor comprises a detector, the detector comprises a CMOS sensor; a LiF thin film is attached to the light-sensitive surface of the CMOS sensor; the method comprises the following steps that a part of neutrons enable the CMOS sensor to generate a radiation response signal A; the other part of neutrons and 6Li are subjected to nuclear reaction to generate alpha rays and tritium ions, so that the CMOS sensor respectively generates a radiation response signal B and a radiation response signal C; the gamma ray enables the CMOS sensor to generate a radiation response signal D; and according to the difference of the four radiation response signals in morphology and / or gray values, discriminating the neutron-gamma mixed radiation field. The detector formed by combining the LiF film and the CMOS sensor is used for discriminating a neutron-gamma mixed radiation field and can be used for monitoring nuclear leakage of a reactor.

Description

Technical Field

[0001] The present invention relates to the field of nuclear science and technology, in particular to a neutron-gamma mixed radiation screening method based on radiation response signals. Background Art

[0002] Neutron-gamma-ray mixed radiation discrimination is an important research area in nuclear science. Its primary goal is to accurately distinguish neutrons from gamma rays in complex radioactive environments. Due to interactions between neutrons and the surrounding environment, such as non-ejective scattering and radiative capture by slow neutrons, gamma rays often coexist with neutrons, making discrimination between neutrons and gamma rays a challenge.

[0003] Current methods for identifying mixed neutron-gamma radiation fields have evolved from "mixed radiation time-domain identification methods" to "intelligent identification technologies based on machine learning." However, these methods still have some shortcomings in practical applications, such as: 1. Poor identification performance at low energy thresholds; 2. Sensitivity to noise in electronic systems, leading to distortion and inaccuracy in identification results; and 3. Reliability in identification relies on high-quality training sets, which are difficult and costly to obtain. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a neutron-gamma ray mixed radiation discrimination method based on radiation response signals, which solves the problems of the existing neutron-gamma ray mixed radiation discrimination technology, such as poor discrimination effect at low energy thresholds, sensitivity to noise in electronic systems, and dependence of discrimination accuracy on high-quality training sets.

[0005] The technical solution of the present invention is: a neutron-gamma mixed radiation discrimination method based on radiation response signals, relying on a nano-coated CMOS sensor neutron measurement system; The nano-coated CMOS sensor neutron measurement system includes a detector, a circuit board, a chip board and a PC. The detector includes a CMOS sensor. The photosensitive surface of the CMOS sensor is not glass-encapsulated. The photosensitive surface of the CMOS sensor is attached with a LiF film with a thickness of 200nm to 2um. The lithium element in LiF is 6 Li; The CMOS sensor is mounted on a circuit board, which is in communication with a chip board. The chip board has a SoC chip mounted thereon, and the chip board is used to output a frame image containing a radiation response signal. A PC is in communication with the chip board, and the PC is used to identify the radiation response signal in the frame image. The method is as follows: the neutrons incident on the LiF film are divided into two parts, one part of the neutrons directly passes through the LiF film and does not interact with the LiF film. 6Li undergoes nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal A; another part of the neutrons passes through the LiF film and reacts with 6 Li undergoes nuclear reaction, generating α rays and tritium ions that are incident on the CMOS sensor, causing the CMOS sensor to generate radiation response signals B and C respectively; the γ rays incident on the LiF film pass through the LiF film directly without reacting with the CMOS sensor. 6 Li undergoes a nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal D. Based on the differences in morphology and / or grayscale values of the above four radiation response signals, neutrons, α rays, tritium ions and γ rays are distinguished, thereby realizing the discrimination of the neutron-gamma mixed radiation field.

[0006] A further technical solution of the present invention is that the radiation response signal D excited by gamma rays is in the form of one or more rectangles superimposed with an aspect ratio greater than 2:1, and in the radiation response signal D, the grayscale values of 80%-95% of the pixels are distributed in the range of 230-255; the radiation response signal A excited by neutrons is in the form of a circle or an ellipse, including a central area and a peripheral area surrounding the central area, and in the radiation response signal A, only 5%-20% of the pixels have grayscale values distributed in the range of 50-60, and are all in the central area of the radiation response signal A, and the average grayscale value of the remaining pixels is in the range of 230-255. Between 10-30; the radiation response signal B excited by α rays is circular or elliptical in shape, and in the radiation response signal B, the grayscale values of more than 70%-95% of the pixels are distributed in the range of 230-255; the radiation response signal C excited by tritium ions is circular or elliptical in shape, which includes a central area and a peripheral area surrounding the central area. In the radiation response signal C, only 5%-15% of the pixels have grayscale values distributed in the range of 230-255, and are all in the central area of the radiation response signal C. The average grayscale value of the remaining pixels is between 50-120.

[0007] A further technical solution of the present invention is: when one or more of radiation response signal A, radiation response signal B, radiation response signal C, and radiation response signal D exist in the frame image at the same time, it means that the neutron-gamma mixed radiation field has been identified.

[0008] A further technical solution of the present invention is: the processing process of the CMOS sensor is as follows: a LiF film with a thickness of 200nm to 2um is evaporated on the photosensitive surface of the CMOS sensor from which the glass package has been removed using vacuum thermal evaporation coating technology.

[0009] A further technical solution of the present invention is that a layer of moderation material for slowing down fast neutrons into slow neutrons is attached to the surface of the LiF film, and the moderation material is paraffin.

[0010] Compared with the prior art, the present invention has the following advantages: 1. This detector, formed by combining a LiF film with a CMOS sensor, is used to discriminate mixed neutron-gamma radiation fields. This solves the problems of existing neutron-gamma ray mixed radiation discrimination technologies, such as poor discrimination performance at low energy thresholds, sensitivity to noise in electronic systems, and reliance on high-quality training sets for discrimination accuracy. It can be used to monitor nuclear leaks in reactors. Neutrons in the mixed radiation field, after conversion by the LiF film, generate alpha rays and tritium ions, which are incident on the photosensitive surface of the CMOS sensor. Gamma rays and some neutrons in the mixed radiation field do not react with the LiF film and instead enter the photosensitive surface of the CMOS sensor. The radiation response signals generated by these four types of rays and particles in the CMOS sensor exhibit significant differences in morphology and / or grayscale values (due to the different response capabilities of the CMOS sensor to these four types of rays or particles). This allows for accurate discrimination, thereby achieving the goal of discriminating mixed neutron-gamma radiation fields.

[0011] 2. Achieve efficient neutron detection and discrimination: Based on the efficient conversion capability of LiF coating for neutrons, neutrons to which CMOS sensors are insensitive are converted into α rays to which CMOS sensors are sensitive, significantly improving the detection efficiency of neutrons (especially low-energy neutrons), thereby providing a prerequisite for the discrimination of neutron-gamma mixed radiation fields.

[0012] 3. Retain the visible light imaging function of the CMOS sensor: LiF is a transparent material. When attached to the photosensitive surface of the CMOS sensor, it does not affect the CMOS sensor's detection of visible light, thus retaining the CMOS sensor's imaging capability.

[0013] 4. Achieve low cost and portability: Based on the miniaturization and integrated design of CMOS sensors, combined with the cost-effective LiF coating evaporation technology, the system cost is effectively reduced and the portability is improved.

[0014] 5. Flexibility and scalability: The coating material and CMOS sensor configuration can be adjusted according to specific detection requirements to adapt to different neutron detection scenarios.

[0015] 6. Real-time image feedback and processing: Combined with existing image noise suppression algorithms, the system extracts and suppresses radiation response signals in frame images, thereby providing clear imaging images and real-time radiation monitoring feedback.

[0016] The present invention is further described below with reference to the figures and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the connection diagram of the nano-coated CMOS sensor neutron measurement system; Figure 2 is a schematic diagram of the detector structure; Figure 3 is a histogram of pixel values of the radiation response signal D excited by γ rays; Figure 4 is a histogram of pixel values of the radiation response signal A stimulated by neutrons; Figure 5 is a histogram of pixel values of the radiation response signal B excited by α rays; Figure 6 It is a histogram of the pixel value distribution of the radiation response signal C excited by tritium ions.

[0018] Legend: Detector 1; CMOS sensor 11; LiF film 12; circuit board 2; chip board 3; PC 4. DETAILED DESCRIPTION Example 1

[0019] like Figure 1-2 As shown, the nano-coated CMOS sensor neutron measurement system includes a detector 1, a circuit board 2, a chip board 3 and a PC 4. The detector 1 includes a CMOS sensor 11. The photosensitive surface of the CMOS sensor 11 is not glass-encapsulated. The photosensitive surface of the CMOS sensor 11 is attached with a LiF film 12 with a thickness of between 200nm and 2um. The lithium element in LiF is 6 CMOS sensor 11 is mounted on circuit board 2, which is in communication with chip board 3. Chip board 3 has a SoC chip mounted thereon. Chip board 3 is configured to output a frame image containing a radiation response signal. A PC 4 is in communication with chip board 3 and is configured to identify the radiation response signal in the frame image.

[0020] Preferably, the processing process of the CMOS sensor is as follows: a LiF thin film with a thickness of 200 nm to 2 μm is deposited on the photosensitive surface of the CMOS sensor from which the glass package has been removed by using vacuum thermal evaporation coating technology.

[0021] Preferably, a layer of moderation material for slowing down fast neutrons into slow neutrons is attached to the surface of the LiF film, and the moderation material is paraffin.

[0022] The neutron-gamma mixed radiation discrimination method based on the radiation response signal relies on the above-mentioned nano-coated CMOS sensor neutron measurement system. The method is as follows: The neutrons incident on the LiF film are divided into two parts. One part of the neutrons passes through the LiF film directly without 6 Li undergoes nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal A; another part of the neutrons passes through the LiF film and reacts with6 Li undergoes nuclear reaction (n+ 6 Li→α+T+4.786MeV), generating α rays and tritium ions that are incident on the CMOS sensor, causing the CMOS sensor to generate radiation response signals B and C respectively. The γ rays incident on the LiF film pass through the LiF film directly without 6 Li undergoes a nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal D.

[0023] According to the differences in morphology and / or grayscale values of the above four radiation response signals, neutrons, α rays, tritium ions and γ rays are identified, thereby realizing the identification of neutron-gamma mixed radiation field. The radiation response signals excited by neutrons, α rays, tritium ions and γ rays are respectively as follows: Figure 3 、 4 , 5 and 6.

[0024] According to the analysis of the experimental data set (1000 experiments, 22.5ms integration time, 32dB gain), the radiation response signal D excited by gamma rays is shaped like a superposition of one or more rectangles with an aspect ratio greater than 2:1. In the radiation response signal D, the grayscale values of 80%-95% of the pixels are distributed in the range of 230-255 (confidence level >95%).

[0025] According to the analysis of the experimental data set (1000 experiments, 22.5ms integration time, 32dB gain), the radiation response signal A excited by neutrons is circular or elliptical in shape, consisting of a central area and a peripheral area surrounding the central area. In the radiation response signal A, only 5%-20% of the pixels have grayscale values distributed in the range of 50-60, and are all located in the central area of the radiation response signal A (confidence level > 80%). The average grayscale value of the remaining pixels is between 10-30.

[0026] According to the analysis of the experimental data set (1000 experiments, 22.5ms integration time, 32dB gain), the radiation response signal B excited by α rays is circular or elliptical in shape. In the radiation response signal B, the grayscale values of more than 70%-95% of the pixels are distributed in the range of 230-255 (confidence level > 95%).

[0027] According to the analysis of the experimental data set (1000 experiments, integration time 22.5ms, gain 32dB), the radiation response signal C excited by tritium ions is circular or elliptical in shape, including a central area and a peripheral area surrounding the central area. In the radiation response signal C, only 5%-15% of the pixels have grayscale values distributed in the range of 230-255, and are all located in the central area of the radiation response signal C (confidence > 80%). The average grayscale value of the remaining pixels is between 50-120.

[0028] When one or more of radiation response signal A, radiation response signal B, radiation response signal C, and radiation response signal D are present in the frame image at the same time, it means that a neutron-gamma mixed radiation field has been identified.

Claims

1. A neutron-gamma mixed radiation discrimination method based on radiation response signals, characterized by: Neutron measurement system based on nano-coated CMOS sensor; The nano-coated CMOS sensor neutron measurement system includes a detector, a circuit board, a chip board and a PC. The detector includes a CMOS sensor. The photosensitive surface of the CMOS sensor is not glass-encapsulated. The photosensitive surface of the CMOS sensor is attached with a LiF film with a thickness of 200nm to 2um. The lithium element in LiF is 6 Li; The CMOS sensor is mounted on a circuit board, which is in communication with a chip board. The chip board has a SoC chip mounted thereon, and the chip board is used to output a frame image containing a radiation response signal. A PC is in communication with the chip board, and the PC is used to identify the radiation response signal in the frame image. The method is as follows: the neutrons incident on the LiF film are divided into two parts, one part of the neutrons directly passes through the LiF film and does not interact with the LiF film. 6 Li undergoes nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal A; another part of the neutrons passes through the LiF film and reacts with 6 Li undergoes nuclear reaction, generating α rays and tritium ions that are incident on the CMOS sensor, causing the CMOS sensor to generate radiation response signals B and C respectively; the γ rays incident on the LiF film pass through the LiF film directly without reacting with the CMOS sensor. 6 Li undergoes a nuclear reaction and is incident on the photosensitive surface of the CMOS sensor, causing the CMOS sensor to generate a radiation response signal D. Based on the differences in morphology and / or grayscale values of the above four radiation response signals, neutrons, α rays, tritium ions and γ rays are distinguished, thereby realizing the discrimination of the neutron-gamma mixed radiation field.

2. The neutron-gamma mixed radiation discrimination method based on radiation response signals according to claim 1, characterized in that: The radiation response signal D excited by gamma rays is in the form of one or more rectangles with an aspect ratio greater than 2:

1. In the radiation response signal D, the grayscale values of 80%-95% of the pixels are distributed in the range of 230-255. The radiation response signal A excited by neutrons is in the form of a circle or ellipse, including a central area and a peripheral area surrounding the central area. In the radiation response signal A, only 5%-20% of the pixels have grayscale values distributed in the range of 50-60, and all are located in the central area of the radiation response signal A. The average grayscale value of the remaining pixels is between 10-30. The radiation response signal B excited by α rays is circular or elliptical in shape. In the radiation response signal B, the grayscale values of more than 70%-95% of the pixels are distributed in the range of 230-255. The radiation response signal C excited by tritium ions is circular or elliptical in shape, which includes a central area and a peripheral area surrounding the central area. In the radiation response signal C, only 5%-15% of the pixels have grayscale values distributed in the range of 230-255, and are all located in the central area of the radiation response signal C. The average grayscale value of the remaining pixels is between 50-120.

3. The neutron-gamma mixed radiation discrimination method based on radiation response signals according to claim 2, characterized in that: When one or more of radiation response signal A, radiation response signal B, radiation response signal C, and radiation response signal D are present in the frame image simultaneously, it means that a neutron-gamma mixed radiation field has been identified.

4. The neutron-gamma mixed radiation discrimination method based on radiation response signals according to claim 3, characterized in that: The processing process of the CMOS sensor is as follows: a LiF thin film with a thickness of 200nm to 2um is deposited on the photosensitive surface of the CMOS sensor from which the glass package has been removed by using vacuum thermal evaporation coating technology.

5. The neutron-gamma mixed radiation discrimination method based on radiation response signals according to claim 4, characterized in that: A layer of moderation material for slowing down fast neutrons into slow neutrons is attached to the surface of the LiF film, and the moderation material is paraffin.

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