Pulse gamma-ray energy spectrum measurement system and method based on scintillation fiber-SiPM

Abstract

The invention relates to a pulse gamma ray energy spectrum measurement system, in particular to a pulse gamma ray energy spectrum measurement system and method based on scintillation fiber-SiPM, and aims to solve the problems that an existing system for detecting a pulse gamma ray energy spectrum has no time-intensity joint spectrum information and is high in cost. The system comprises a scintillation fiber array, a light conduction unit whose input end is connected with the output end of the scintillation fiber array, a light homogenizer whose input end is connected with the output end of the light conduction unit, and a photoelectric detection system whose input end is connected with the output end of the light homogenizer. The input surface of the scintillation optical fiber array is perpendicular to the path of an incident electron beam, and the scintillation optical fiber array comprises x scintillation optical fibers which are arranged in a gapless close arrangement manner; the light conduction unit comprises x conduction optical fibers; the light homogenizer comprises x light homogenization units; the photoelectric detection system comprises x SiPM detectors and a signal reading unit.

Description

Technical Field

[0001] The present invention relates to a measurement system for pulsed gamma-ray energy spectrum, and particularly to a pulsed gamma energy spectrum measurement system and method based on scintillating fiber - SiPM. Background Art

[0002] New pulsed radiation sources (such as laser inverse Compton scattering sources, free electron laser sources, advanced synchrotron radiation sources, or radiation sources based on laser plasma acceleration) have become key tools for frontier scientific research due to their ultrafast and quasi-monochromatic energy characteristics. Pulsed gamma energy spectrum, as a key parameter characterizing the radiation field characteristics of pulsed radiation sources, directly affects key applications such as pulsed radiation field calibration and detector sensitivity calibration, and is of great significance for radiation physics research and ray source performance evaluation. In recent years, laser inverse Compton scattering sources have developed rapidly. Through the interaction of high-energy electron beams and high-power lasers, they can generate gamma-ray beams with picosecond pulse widths and excellent energy monochromaticity, which makes the conventional energy spectrum measurement techniques in counting mode inapplicable and poses new challenges to traditional energy spectrum measurement methods.

[0003] The Compton magnetic spectrometer is the core device for pulsed gamma energy spectrum diagnosis, providing support for the research and application of inverse Compton scattering sources. Its main structure includes a conversion target, a collimator, an analyzing magnet, a detection system, and other auxiliary devices. The working principle of the Compton magnetic spectrometer: The detected gamma rays are converted into Compton electrons when hitting the conversion target. Compton electrons with the same energy are screened by the collimator and then deflected and focused to the same transverse position by the analyzing magnet. The detection system collects the position and intensity information of the electrons, and finally inversely solves the gamma energy spectrum information. The Compton magnetic spectrometer requires the detection system to have good transverse position resolution ability and intensity detection ability.

[0004] Traditional Compton magnetic spectrometers usually use a detection system based on an imaging plate (IP plate). Such a detection system can only detect one-dimensional energy spectrum information and cannot achieve the function of online monitoring. If it is necessary to detect the time-energy joint spectrum, a detection system based on a scintillator / Cherenkov radiation + photomultiplier tube is required. The photomultiplier tube needs to be combined with a high-speed data acquisition system. For a single-channel signal of pulsed gamma rays, a sampling rate of 1 GHz and a bandwidth greater than 300 MHz are required. In a detection system based on scintillating fiber coupled with silicon photomultiplier (SiPM), often hundreds of channels of signals need to be collected and output simultaneously, which is difficult to achieve and has a high cost. Summary of the Invention

[0005] The object of the present invention is to solve the problems of the existing system for detecting pulsed gamma energy spectrum having no signal, no time-intensity joint spectrum information, and high cost, and to provide a pulsed gamma energy spectrum measurement system and method based on scintillating fiber - SiPM.

[0006] To achieve the above object, the technical solution provided by the present invention is as follows:

[0007] A pulsed gamma energy spectrum measurement system based on a scintillating fiber - SiPM, characterized in that:

[0008] It includes a γ - e conversion module, a scintillating fiber array, an optical conduction unit with its input end connected to the output end of the scintillating fiber array, an optical homogenizer with its input end connected to the output end of the optical conduction unit, a photoelectric detection system with its input end connected to the output end of the optical homogenizer, and a data processing module;

[0009] The γ - e conversion module is used to convert the gamma rays to be measured into Compton electrons and deflect the Compton electrons with different energies to different lateral positions to form an incident electron beam;

[0010] The input surface of the scintillating fiber array is perpendicular to the path of the incident electron beam. It includes x scintillating fibers arranged in a gap - free close - packed manner. The cross - section of each scintillating fiber is a square, and x ∈ [100, 1500];

[0011] The optical conduction unit includes x conduction fibers, and the input end of each conduction fiber is connected to the output end of a corresponding scintillating fiber;

[0012] The optical homogenizer includes x optical homogenization units. Each optical homogenization unit includes an input surface and an output surface. Each input surface is connected to the output end of a corresponding conduction fiber; the area of the input surface < the area of the output surface;

[0013] The photoelectric detection system includes x SiPM detectors with their photosensitive surfaces connected to the output surfaces of the corresponding optical homogenization units, and a signal readout unit with its input ends respectively connected to the output ends of each SiPM detector. The output end of the signal readout unit is used to be connected to the data processing module;

[0014] The scintillating fiber array is used to convert the incident electron beam into scintillation light at different lateral positions, and then transmit the photons to the optical homogenizer through the optical conduction unit. The optical homogenizer is used to evenly distribute the photons transmitted in the conduction fibers onto the photosensitive surfaces of the corresponding SiPM detectors; the SiPM detectors are used to receive the incident photons and generate and amplify the corresponding electrical signals; the signal readout unit is used to generate the time - intensity spectrum of the incident electrons in the incident electron beam corresponding to different lateral positions; the data processing module is used to convert the time - intensity spectrum into pulsed gamma time - energy spectrum information, that is, the energy spectrum of the gamma rays.

[0015] Furthermore, the photosensitive surface area of each SiPM detector is greater than or equal to the output surface area of the corresponding optical homogenization unit.

[0016] Further, x = 400, the length of each scintillating optical fiber is 200 mm, and the cross-sectional area of each is 1 mm 2 ; the length of each of the conducting optical fibers is ≥500 mm; the input surface area of each of the optical homogenizing units is 1 mm 2 , and the output surface area of each is 6 mm 2 .

[0017] Further, each of the optical homogenizing units is an optical cone.

[0018] Meanwhile, the present invention also provides a method for measuring pulsed gamma energy spectrum based on scintillating optical fiber - SiPM, which is characterized in that it includes the following steps:

[0019] Step 1, assemble the above-mentioned pulsed gamma energy spectrum measurement system based on scintillating optical fiber - SiPM;

[0020] Step 2, gamma rays generate Compton electrons through the conversion module, and Compton electrons with different energies are deflected to different lateral positions to form an incident electron beam; the incident electron beam reaches the scintillating optical fiber array and deposits energy in the scintillating optical fibers at different lateral positions to emit scintillation light, and the scintillation light is collected by the scintillating optical fibers and reaches the optical homogenizer through the corresponding conducting optical fibers in the optical conduction unit;

[0021] Step 3, the optical homogenizer uniformly distributes the received scintillation light onto the photosensitive surface of the SiPM detector in the photoelectric detection system;

[0022] Step 4, each photon is collected by a micropore in the SiPM detector, and an avalanche effect occurs in the micropore to generate and amplify an electrical signal. The amplified electrical signals generated by all the micropores are used as an amplified electrical signal set, which is integrated and transmitted to the signal readout unit of the photoelectric detection system;

[0023] Step 5, the signal readout unit collects the time information at at least five different voltage thresholds in the amplified electrical signal set, inversely calculates the electrical signal generated by the SiPM detector through signal feature fitting, and obtains the time - intensity spectrum of the incident electron beam of the corresponding scintillating optical fiber according to the number of the SiPM detector. The time - intensity spectra of the incident electrons in the incident electron beams corresponding to different scintillating optical fibers are used as the first raw data and transmitted to the data processing module. Then, the data processing module combines the number information of the scintillating optical fibers in the scintillating optical fiber array and the first raw data, and finally obtains the pulsed gamma time - energy spectrum information to complete the measurement.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM provided by the present invention has a scintillating fiber array with an ns - level time resolution, capable of realizing the joint measurement of time - intensity spectra.

[0026] 2. For the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM provided by the present invention, on the one hand, its optical homogenizer reduces the intensity requirement for the detected pulsed radiation source; on the other hand, it expands the upper limit of the dynamic range of the SiPM detector chip, increasing the detection range of the gamma energy spectrum.

[0027] 3. For the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM provided by the present invention, in its photoelectric detection system, the SiPM detector and the signal read - out unit simplify the acquisition and reading processes of the multi - channel system. On the one hand, it reduces the overall sampling rate requirement; on the other hand, it optimizes the spatial structure of the system and greatly reduces the cost, and can meet the diagnostic requirements of the gamma energy spectrum time - energy joint spectrum efficiently and at low cost.

[0028] 4. For the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM provided by the present invention, the photosensitive surface area of each SiPM detector is greater than or equal to the output surface area of the corresponding optical homogenization unit, which can improve the utilization efficiency of the photosensitive surface and avoid light loss.

[0029] 5. For the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM provided by the present invention, each optical homogenization unit is an optical cone, which can control the size and shape of the expanded light spot, and has good light transmission consistency in the case of multiple arrays. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of an embodiment of the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM of the present invention; (the conversion module and the data processing module are not shown)

[0031] Figure 2 It is a schematic diagram of the pulse X - ray intensity - time spectrum obtained by the photoelectric detection system in an embodiment of the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM of the present invention;

[0032] Description of the Reference Numerals:

[0033] 1 - incident electron beam, 2 - scintillating fiber array, 3 - light conduction unit, 4 - optical homogenizer, 5 - photoelectric detection system. Detailed Embodiments

[0034] The present invention will be further described below with reference to the drawings and specific embodiments.

[0035] A pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM is used to measure the energy spectrum of gamma rays according to the incident electron beam 1 converted from gamma rays. See Figure 1 , and includes a γ - e conversion module, a scintillating fiber array 2, an optical conduction unit 3 with its input end connected to the output end of the scintillating fiber array 2, an optical homogenizer 4 with its input end connected to the output end of the optical conduction unit 3, a photoelectric detection system 5 with its input end connected to the output end of the optical homogenizer 4, and a data processing module;

[0036] The conversion module includes a conversion target and an analyzing magnet. Gamma rays generate Compton electrons through the conversion target, and the analyzing magnet deflects Compton electrons with different energies to different lateral positions to form the incident electron beam 1;

[0037] The scintillating fiber array 2 uses plastic scintillating fibers. Its input surface is perpendicular to the path of the incident electron beam 1. It includes 400 scintillating fibers arranged in a gap - free close - packed manner, and the cross - section of each scintillating fiber is a square; the length of each scintillating fiber is 200 mm, and the cross - sectional area of each is 1 mm 2 ;

[0038] The optical conduction unit 3 includes 400 conduction fibers. The input end of each conduction fiber is connected to the output end of a corresponding scintillating fiber; the length of each conduction fiber is 500 mm;

[0039] The optical homogenizer 4 includes 400 optical homogenization units. Each optical homogenization unit is an optical cone, and each includes an input surface and an output surface. Each input surface is connected to the output end of a corresponding conduction fiber; the area of each input surface is 1 mm 2 , and the area of each output surface is 6 mm 2 .

[0040] The photoelectric detection system 5 includes 400 SiPM detectors with their photosensitive surfaces connected to the output surfaces of corresponding optical homogenization units, and a signal read - out unit with its input end connected to the output end of each SiPM detector. The output end of the signal read - out unit is used to be connected to the data processing module;

[0041] The scintillating fiber array 2 is used to convert the incident electron beam 1 into scintillation light, and then transmit the photons to the optical homogenizer 4 via the optical conduction unit 3. The optical homogenizer 4 is used to evenly distribute the photons transmitted in the conduction fibers onto the photosensitive surfaces of the corresponding SiPM detectors; the SiPM detectors are used to receive the incident photons and generate corresponding amplified electrical signals; the signal read - out unit is used to generate the time - intensity spectrum of the incident electrons in the incident electron beam 1 corresponding to different lateral positions; the external data processing module is used to convert the time - intensity spectrum into pulse gamma time - energy spectrum information, that is, the energy spectrum of gamma rays.

[0042] The photosensitive surface of each SiPM detector has the same area as the output surface of the corresponding light homogenization unit. Each SiPM detector further includes a microchannel plate with an input end connected to the photosensitive surface, and the output end of each microchannel plate is connected to the signal readout unit; the photosensitive surface is used to receive incident photons, and the microchannel plate is used to generate an avalanche effect on the incident photons and generate corresponding amplified electrical signals.

[0043] Meanwhile, this embodiment also provides a method for measuring pulsed gamma energy spectrum based on scintillating fiber - SiPM, including the following steps:

[0044] Step 1, Assemble the above - mentioned pulsed gamma energy spectrum measurement system based on scintillating fiber - SiPM;

[0045] Step 2, Gamma rays generate Compton electrons through the conversion target, and after being deflected by the analyzing magnet, they reach the input surface of the scintillating fiber array 2; the electrons reaching the scintillating fiber array 2 deposit energy in the corresponding scintillating fibers and cause them to emit scintillation light. The scintillation light is collected by the scintillating fibers and then reaches the light homogenizer 4 through the corresponding conduction fibers in the light conduction unit 3;

[0046] Step 3, The light homogenizer 4 evenly distributes the received scintillation light to the photosensitive surface of the SiPM detector in the photoelectric detection system 5;

[0047] Step 4, Each photon of the scintillation light is collected by a micropore in the SiPM detector, and an avalanche effect occurs in the micropore to generate and amplify an electrical signal. The amplified electrical signals generated by all micropores are used as an amplified electrical signal set, which is integrated and transmitted to the signal readout unit of the photoelectric detection system 5;

[0048] Step 5, The signal readout unit collects the time information at five different voltage thresholds in the amplified electrical signal set, inversely calculates the electrical signal generated by the SiPM detector through signal feature fitting, and obtains the time - intensity spectrum of the incident electron beam 1 corresponding to the scintillating fiber according to the number of the SiPM detector. The time - intensity spectra of the incident electrons in the incident electron beam 1 corresponding to different scintillating fibers are used as the first original data and transmitted to the external data processing module. Then, the external data processing module combines the number information of the scintillating fibers in the scintillating fiber array 2 and the first original data to finally obtain the pulsed gamma time - energy spectrum information, completing the measurement.

[0049] The method adopted in step 5 of the present invention is the multi - voltage threshold sampling method. The multi - voltage threshold sampling method (MVT, Multi - Voltage Threshold) is to collect the time information at multiple different thresholds and inversely calculate the overall signal information through signal features, which can greatly reduce the requirements for signal sampling rate and transmission bandwidth.

[0050] Scintillating fiber-coupled silicon photomultiplier (SiPM) technology has shown spatial resolution on the order of μm and time resolution on the order of ns in fields such as muon detection, thermal neutron detection, and dose monitoring, and has a cost advantage. The scintillating fiber-coupled SiPM technology combined with the MVT method meets the detection requirements of the Compton magnetic spectrometer.

[0051] Figure 2 This is a schematic diagram of the pulse X-ray intensity-time spectrum obtained by the photodetection system in the embodiment of the pulse gamma energy spectrum measurement system based on scintillating fiber-SiPM of the present invention; according to the MVT method, the time information at five different voltage thresholds in Figure 2 V i , V j , V k , V m , V n can be collected, and the actual signal of a single fiber as shown in Figure 2 can be obtained. Based on this signal, the intensity-time spectrum of the incident electrons on this fiber can be obtained. Combining the position information obtained from its corresponding number, the energy-time spectrum of gamma rays can be finally reconstructed.

Claims

1. A pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM, characterized in that: It includes a γ - e conversion module, a scintillating fiber array (2), an optical conduction unit (3) with its input end connected to the output end of the scintillating fiber array (2), an optical homogenizer (4) with its input end connected to the output end of the optical conduction unit (3), a photoelectric detection system (5) with its input end connected to the output end of the optical homogenizer (4), and a data processing module; The γ - e conversion module is used to convert the gamma rays to be measured into Compton electrons, and deflect Compton electrons with different energies to different lateral positions to form an incident electron beam (1); The input surface of the scintillating fiber array (2) is perpendicular to the path of the incident electron beam (1), and it includes x scintillating fibers arranged in a gap - free close - packed manner. The cross - section of each scintillating fiber is square, and x ∈ [100, 1500]; The optical conduction unit (3) includes x conduction fibers, and the input end of each conduction fiber is connected to the output end of a corresponding scintillating fiber; The optical homogenizer (4) includes x optical homogenization units. Each optical homogenization unit includes an input surface and an output surface. Each input surface is connected to the output end of a corresponding conduction fiber; the area of the input surface < the area of the output surface; The photoelectric detection system (5) includes x SiPM detectors with their photosensitive surfaces connected to the output surfaces of the corresponding optical homogenization units, and a signal read - out unit with its input ends respectively connected to the output ends of each SiPM detector. The output end of the signal read - out unit is used to be connected to the data processing module; The scintillating fiber array (2) is used to convert the incident electron beam (1) into scintillation light at different lateral positions, and then transmit the photons to the optical homogenizer (4) through the optical conduction unit (3). The optical homogenizer (4) is used to evenly distribute the photons transmitted in the conduction fibers onto the photosensitive surfaces of the corresponding SiPM detectors; the SiPM detectors are used to receive the incident photons and generate and amplify the corresponding electrical signals; the signal read - out unit is used to generate a time - intensity spectrum of the incident electrons in the incident electron beam (1) corresponding to different lateral positions; the data processing module is used to convert the time - intensity spectrum into pulse gamma time - energy spectrum information, that is, the energy spectrum of gamma rays.

2. The pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM according to claim 1, characterized in that: The photosensitive surface area of each SiPM detector is greater than or equal to the output surface area of the corresponding optical homogenization unit.

3. The pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM according to claim 1, characterized in that: where x = 400, the length of each scintillating optical fiber is 200 mm, and the cross-sectional area of each is 1 mm 2 ; the length of each of the conducting optical fibers is ≥ 500 mm; the input surface area of each of the optical homogenizing units is 1 mm 2 and the output surface area of each is 6 mm 2 .

4. The pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM according to claim 3, characterized in that: Each of the optical homogenization units is an optical cone.

5. A pulse gamma energy spectrum measurement method based on scintillating fiber - SiPM, characterized in that, It includes the following steps: Step 1, assemble the pulse gamma energy spectrum measurement system based on scintillating fiber - SiPM according to any one of claims 1 - 4; Step 2: Gamma rays generate Compton electrons through the conversion module, and the Compton electrons with different energies are deflected to different lateral positions to form an incident electron beam (1); the incident electron beam (1) reaches the scintillating fiber array (2) and deposits energy in the scintillating fibers at different lateral positions to emit scintillation light, and the scintillation light is collected by the scintillating fibers and reaches the light homogenizer (4) through the corresponding conduction fibers in the light conduction unit (3); Step 3: The light homogenizer (4) evenly distributes the received scintillation light onto the photosensitive surface of the SiPM detector in the photoelectric detection system (5); Step 4: Each photon is collected by a micropore in the SiPM detector, and an avalanche effect occurs in the micropore to generate and amplify an electrical signal. The amplified electrical signals generated by all micropores are used as an amplified electrical signal set, which is integrated and transmitted to the signal readout unit of the photoelectric detection system (5); Step 5: The signal readout unit acquires the time information at at least five different voltage thresholds in the amplified electrical signal set, inversely calculates the electrical signal generated by the SiPM detector through signal feature fitting, and obtains the time-intensity spectrum of the incident electrons in the incident electron beam (1) corresponding to the scintillating fiber according to the number of the SiPM detector. The time-intensity spectra of the incident electrons in the incident electron beam (1) corresponding to different scintillating fibers are used as the first raw data and transmitted to the data processing module. Then, the data processing module combines the number information of the scintillating fibers in the scintillating fiber array (2) and the first raw data, and finally obtains the pulsed gamma time-energy spectrum information to complete the measurement.

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