Position-sensitive reactor core optical fiber detector and preparation method thereof

Abstract

The invention discloses a position-sensitive reactor core optical fiber detector and a preparation method thereof, and relates to the field of radiation detection, the position-sensitive reactor core optical fiber detector comprises a probe (1), an optical fiber bundle (2) and an electronics system (3), and the probe (1), the optical fiber bundle (2) and the electronics system (3) are externally connected in sequence by using a high-temperature-resistant sealant (4); the probe (1) comprises a scintillator (11), an optical glass light guide rod (12) and a protective shell (13); the scintillator (11) and the optical glass light guide rod (12) are sequentially arranged according to a sandwich structure and are arranged in the protective shell (13); the optical fiber bundle (2) comprises a metal coating optical fiber (21), a high-temperature-resistant adhesive (22) and a stainless steel metal coil (23). The problems that an existing optical fiber detector cannot be used for detection work under the conditions of high temperature, high pressure and strong irradiation, and the existing optical fiber detector can only achieve flux detection and cannot be used for position detection are solved.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection, and particularly to a position-sensitive core optical fiber detector and a preparation method thereof. Background Art

[0002] Core detection technology is mainly used for nuclear reactor power monitoring and core condition monitoring. By simultaneously measuring the neutron signal, gamma signal, or both in the core, the working state of the reactor core can be understood to ensure that the reactor operates within a safe range.

[0003] At present, the equipment used for reactor core γ detection mainly includes a self-powered gamma detector (SPGD). The SPGD is a new type of detector with the characteristics of not requiring an external power supply, miniaturization, and simple structure, and can be used for detecting γ signals in the core under high-temperature and high-pressure conditions. However, the SPGD is only applicable to high-flux situations and not to low-flux conditions. The reactor needs to have sufficient power and sufficient flux to output a signal, and it cannot achieve the detection of accurate position information.

[0004] Optical fiber detectors are a new type of detector that has emerged in recent years. Due to their instantaneous characteristics, optical fiber detectors can provide real-time data on core temperature, neutron flux density, and thermal power, and can also be used to monitor the consumption of nuclear fuel. By analyzing γ-ray information, the fission products of the fuel can be evaluated, thereby optimizing the fuel use and replacement strategies. In the event of an accident or abnormal situation, real-time core detection can quickly provide key information inside the reactor, helping emergency personnel quickly assess the situation and take appropriate countermeasures to reduce the impact of the accident. The main body of this detector is composed of optical fibers, and a detection material is coated on the top of the optical fibers. Radiation particles interact with the detection material and generate fluorescence signals, and the optical signals are transmitted to the photomultiplier tube at the other end of the optical fiber through total internal reflection of the optical fiber, converted into electrical signals, and analyzed and output by the subsequent electronics system. At the same time, neutron optical fiber detectors and gamma optical fiber detectors have emerged. Optical fiber detectors have the characteristics of being small enough in size and simple in structure, but they cannot be used for detection work under high-temperature, high-pressure, and strong irradiation conditions. There are problems such as the detection material being difficult to withstand high temperatures under high-temperature conditions and the optical fiber hardening under strong irradiation conditions. Moreover, optical fiber detectors can only achieve flux detection and cannot be used for position detection. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the present invention proposes a position-sensitive core optical fiber detector and its preparation method, which realizes radiation measurement at different points on a single detection optical fiber detector. This detector is used for the core, can solve the problem of multi-point radiation measurement in a narrow space, thereby more accurately reflecting the operating state of the reactor core, and solves the problems that existing optical fiber detectors cannot be used for detection under high-temperature, high-pressure and strong irradiation conditions, and that existing optical fiber detectors can only achieve flux detection and cannot be used for position detection.

[0006] In order to achieve the above object of the invention, the technical solution adopted by the present invention is: a position-sensitive core optical fiber detector, comprising a probe, an optical fiber bundle and an electronics system, and the probe, the optical fiber bundle and the electronics system are externally connected in sequence using a high-temperature resistant sealant;

[0007] The probe includes a scintillator, an optical glass light guide rod and a protective shell, and the scintillator and the optical glass light guide rod are arranged in a sandwich structure in sequence and placed inside the protective shell;

[0008] The optical fiber bundle includes metal-coated optical fibers, high-temperature resistant adhesive, and stainless steel metal coils;

[0009] The electronics system includes a photomultiplier tube, a preamplifier, a main amplifier and a multi-channel pulse amplitude analyzer connected in sequence.

[0010] Furthermore, the scintillator, the optical glass light guide rod and the protective shell are all made of high-temperature resistant materials.

[0011] Furthermore, both the scintillator and the optical glass light guide rod are cylindrical, the protective shell is a cylindrical shape with one end open and one end closed, and the outer diameters of the scintillator and the optical glass light guide rod are both matched with the inner diameter of the protective shell.

[0012] Furthermore, multiple metal-coated optical fibers are arranged in a bundle, and the end faces of all metal-coated optical fibers are located in the same plane.

[0013] Furthermore, the position-sensitive core optical fiber detector is used to detect the position information of gamma signals or neutron signals. When the scintillator uses a gamma-sensitive material, the position detection of gamma signals is realized; when the scintillator uses a neutron-sensitive material, the detection of neutron position signals is realized.

[0014] Furthermore, the electronics system adopts two different analysis and discrimination methods: pulse amplitude discrimination method and decay time discrimination method.

[0015] Further, under high-temperature and high-pressure conditions, the fiber optic bundle uses metal-coated optical fibers; under non-high-temperature conditions, the fiber optic bundle uses wavelength-shifted optical fibers to change the wavelength of the incident light, enabling total internal reflection of the laterally incident light and facilitating long-distance signal transmission.

[0016] Another technical solution adopted by the present invention is: a preparation method of a position-sensitive core fiber optic detector, comprising the following steps:

[0017] S1: Process the material of the protective shell into a cylindrical shape, polish its interior, and weld and seal one end of the protective shell;

[0018] S2: Select scintillators made of different materials and process them into cylindrical shapes of the same volume. Process the optical glass light guide rods into cylindrical shapes, and arrange the scintillators and the optical glass light guide rods in a sandwich structure of one scintillator and one optical glass light guide rod in sequence, and then install them into the protective shell;

[0019] S3: Arrange multiple metal-coated optical fibers to form a fiber optic bundle, wrap and fix it with a stainless steel metal coil on the outside, make its end faces lie in the same plane, and fix both ends of the metal-coated optical fibers respectively with a high-temperature-resistant adhesive;

[0020] S4: Align one end of the fiber optic bundle with the opening of the protective shell, connect them with a high-temperature-resistant sealant on the outside of the connection. Align the other end of the fiber optic bundle with the incident window end of the photomultiplier tube, and connect them with a high-temperature-resistant sealant on the outside of the connection;

[0021] S5: Connect the photomultiplier tube, preamplifier, main amplifier, and multi-channel pulse amplitude analyzer to complete the preparation of the position-sensitive core fiber optic detector.

[0022] The beneficial effects of the present invention are: The present invention provides a position-sensitive core fiber optic detector, which has the characteristics of high temperature resistance, high pressure resistance, radiation resistance, small volume, simple structure, anti-interference, and high sensitivity, providing a new method for detecting the position information of radiation signals in the narrow space of the reactor core and under the harsh environment of high temperature, high pressure, and strong radiation.

[0023] Adopting the technical solution of the present invention, the position information of radiation signals under one-dimensional spatial conditions can be detected in real time online. By using materials such as GAGG and LSO that respond to γ signals, the detection of gamma position information can be achieved; by replacing the scintillation material with materials such as CLYC and CLLB that are sensitive to neutrons, the detection of neutron signals can be achieved. By arranging the detectors in an array in two-dimensional directions, the detection of the position information of γ signals in three-dimensional space can be achieved.

[0024] In the backend electronics system, the present invention can also adopt two different technical solutions: pulse amplitude discrimination method and signal attenuation time discrimination method. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall position-sensitive core fiber optic detector of the present invention example.

[0026] Figure 2 It is a structural diagram of the probe part of the position-sensitive core fiber optic detector of the present invention example

[0027] Figure 3 It is an end face diagram of the fiber optic bundle of the position-sensitive core fiber optic detector of the present invention example.

[0028] Figure 4 It is a flowchart of the preparation method of the position-sensitive core fiber optic detector of the present invention example.

[0029] Wherein: 1. Probe; 2. Fiber optic bundle; 3. Electronics system; 4. High-temperature resistant sealant; 11. Scintillator; 12. Optical glass light guide rod; 13. Protective shell; 111. First scintillator; 112 - Second scintillator; 21. Metal-coated optical fiber; 22. High-temperature resistant adhesive; 23. Stainless steel metal coil. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0031] Example 1, as Figure 1 shown, a position-sensitive core fiber optic detector includes a probe 1, a fiber optic bundle 2, and an electronics system 3. The outside of the probe 1, the fiber optic bundle 2, and the electronics system 3 are sequentially connected using a high-temperature resistant sealant;

[0032] The probe 1 includes a scintillator 11, an optical glass light guide rod 12, and a protective shell 13. The scintillator 11 and the optical glass light guide rod 12 are arranged in a sandwich structure in sequence and placed inside the protective shell 13;

[0033] The fiber optic bundle 2 includes a metal-coated optical fiber 21, a high-temperature resistant adhesive 22, and a stainless steel metal coil 23;

[0034] The electronics system 3 includes a photomultiplier tube 31, a preamplifier 32, a main amplifier 33, and a multi-channel pulse amplitude analyzer 34 connected in sequence.

[0035] The scintillator 11, the optical glass light guide rod 12, and the protective shell 13 are all made of high-temperature resistant materials. The inorganic scintillator material has a relatively high melting point and can withstand the high temperature and high pressure inside the core during the core detection work. For example, the melting points of halide scintillation crystals are all above 600 °C, and Ce 3+The melting points of the novel doped scintillators are basically around 2000 °C. The material of the optical glass light guide rod 12 is mainly quartz material, and the protective shell 13 of the probe part is made of metal material, so it can withstand the working environment of high temperature and high pressure.

[0036] Both the scintillator 11 and the optical glass light guide rod 12 are cylindrical, the protective shell 13 is a cylindrical shape with one end open and one end closed, and the outer diameters of the scintillator 11 and the optical glass light guide rod 12 are both matched with the inner diameter of the protective shell 13.

[0037] Multiple metal-coated optical fibers 21 are arranged in a bundle, and the end faces of all the metal-coated optical fibers 21 are located in the same plane.

[0038] In the present invention, the type of optical fiber used is a metal-coated optical fiber. A metal-coated optical fiber is an optical fiber with a metal layer such as Al or Au coated on the surface of the optical fiber, aiming to improve heat resistance and resist harsh environments. The metal-coated optical fiber not only retains the mechanical strength of the optical fiber but also can withstand the static fatigue caused by long-term tensile loads. The principle is that the coated metal coating and the optical fiber cladding are molecularly bonded, so it has extremely high mechanical properties.

[0039] If in the actual use process, there is no too high requirement for the temperature resistance performance of the detector, but there is a need for long-distance transmission, then wave-shifting optical fibers can be used, which can change the wavelength of the incident light, so that the laterally incident light can also undergo total reflection, which is beneficial to the long-distance transmission of signals.

[0040] The position-sensitive core optical fiber detector is used to detect the position information of gamma signals or neutron signals. When the scintillator 11 uses a gamma-sensitive material, it realizes the position detection of gamma signals; when the scintillator 11 uses a neutron-sensitive material, it realizes the detection of neutron position signals.

[0041] The electronics system 3 adopts two different analysis and discrimination methods: pulse amplitude discrimination method and decay time discrimination method.

[0042] Under high temperature and high pressure conditions, the optical fiber bundle 2 uses metal-coated optical fibers 21; under non-high temperature conditions, the optical fiber bundle 2 uses wave-shifting optical fibers to change the wavelength of the incident light, so that the laterally incident light undergoes total reflection, which is beneficial to the long-distance transmission of signals.

[0043] Adopting the technical solution of the present invention, the position information of the radiation signal under one-dimensional spatial conditions can be detected in real time online. By using materials such as GAGG and LSO that respond to γ signals, the detection of gamma position information can be achieved; by replacing the scintillating material with materials sensitive to neutrons such as CLYC and CLLB, the detection of neutron signals can be realized. By arranging the detectors in an array in two-dimensional directions, the detection of the position information of γ signals in three-dimensional space can be achieved.

[0044] In an embodiment of the present invention, a one-dimensional position-sensitive core fiber detector is provided, which includes three main parts: a probe 1, an optical fiber bundle 2, and an electronics system 3. The three parts can be connected by "adhering with a high-temperature-resistant sealant 4 externally", ensuring the overall structural stability of the detector.

[0045] Among them, the probe 1 includes a scintillator 11, an optical light guide rod 12, and a protective shell 13;

[0046] As Figure 2 shown, the scintillator includes a first scintillator 111 and a second scintillator 112;

[0047] The material used for the first scintillator 111 is GAGG(HL), its light yield is 54000 ph / MeV, the density is 6.63 g / cm 3 , the decay time is 150 ns, and the melting point is 1850 °C;

[0048] The material used for the second scintillator 112 is LSO, its light yield is 26000 ph / MeV, the density is 7.4 g / cm 3 , the decay time is 40 ns, and the melting point is 2150 °C;

[0049] The material used for the optical light guide rod is quartz material;

[0050] The material used for the protective shell 13 is Inconel600. Inconel600 has excellent corrosion resistance and performs outstandingly in many corrosive environments. Whether in a high-temperature oxidation environment or in an environment containing various corrosive media such as strong acid and strong alkali solutions, it can effectively resist corrosion. The melting point is 1400 °C, and it can maintain good mechanical properties and stability in high-temperature environments. Inconel600 can withstand extreme in-core corrosion environments and high-temperature conditions, ensuring that the internal scintillator 11 material and the optical glass light guide rod 12 will not be deformed or damaged due to high temperature.

[0051] As Figure 3 shown, the optical fiber bundle 2 is composed of multiple gold-plated optical fibers 21, wrapped and fixed with a stainless steel metal coil 23 on the outside, and bonded at both ends with a high-temperature-resistant adhesive 22 to ensure stability.

[0052] The optical fibers used in the fiber optic bundle 2 are gold-plated optical fibers 21. The gold-plated optical fiber 21 is an optical fiber with an Au metal layer coated on the surface of the optical fiber. The purpose is to improve heat resistance and resist harsh environments. The metal-coated optical fiber not only retains the mechanical strength of the optical fiber but also can withstand static fatigue caused by long-term tensile loads. The principle is that the coated metal sheath and the fiber cladding are molecularly bonded, so it has extremely high mechanical properties. Gold plating performs excellently in terms of temperature adaptation and can work stably in high-temperature environments of 700 °C to extremely cold temperature environments of -269 °C. The chemical stability of Au itself enables it to resist the corrosion of chemical substances such as acids, alkalis, and salts, and it has strong antioxidant ability. Even after long-term use, the gold-plated layer on its surface will not be oxidized. On the other hand, the gold-plated optical fiber 21 has high strength and good flexibility. The gold-plated layer tightly combined with the optical fiber enhances its mechanical strength, and it is not easy to break when pulled and bent by external forces. Moreover, it has excellent fatigue resistance, can withstand long-term repeated stress, and extends the service life.

[0053] The electronics system includes a photomultiplier tube 31, a preamplifier 32, a main amplifier 33, and a multi-channel pulse amplitude analyzer 34 connected in sequence.

[0054] The photomultiplier tube used is an end-window type photomultiplier tube, and the shape of the photocathode surface area is circular.

[0055] The present invention is implemented based on the following principle. After the one-dimensional position-sensitive core fiber detector enters the radiation field, γ photons will enter the probe 1 through the protective shell 13 and reach the inside of the probe 1. The γ photons excite the scintillator 11 to emit fluorescence. The generated fluorescence is transmitted to the photocathode part of the photomultiplier tube through the fiber optic bundle 2. The photomultiplier tube converts the optical signal into an electrical signal, and after further processing by the subsequent electronics system 3, an analyzable electrical signal is formed, and this process realizes the detection of γ photons.

[0056] For the probe 1 of the one-dimensional position-sensitive core fiber detector, the inside of its protective shell 13 is composed of 2 scintillators 11 (the first scintillator 111 and the second scintillator 112) made of different materials and an optical glass light guide rod element 12, which are arranged in a row with intervals in sequence, forming a sandwich structure. The function of this structure is that under the same γ dose, since the volumes of the scintillators 11 are the same, the γ photon fluxes received by the scintillators 11 are the same; under the same γ flux condition, the fluorescence intensities emitted by the first scintillator 111 and the second scintillator 112 are different, which in turn leads to different signal pulse amplitudes generated in the subsequent electronics system 3. By analyzing the amplitudes of a series of pulse signals through the electronics system 3, it can be identified which scintillator material each pulse signal is emitted from, and then the position of the γ signal can be judged, realizing the position detection of γ photons using the fiber detector.

[0057] In a constant γ-dose field environment, based on the characteristics of uniform radiation dose distribution, when the volumes of multiple scintillators 11 are strictly the same, according to the definition of flux and the assumption of a uniform field, the γ-photon fluxes received by each scintillator 11 must be equal. This process follows the microscopic manifestation of the Lambert-Beer law in the scenario of uniform radiation distribution, that is, under the same radiation conditions, irradiated objects with the same volume receive equal photon fluxes, laying a foundation for subsequent precise detection.

[0058] However, on the premise of the same incident γ-flux, due to differences in intrinsic properties such as atomic structure, energy level distribution, and fluorescence quantum yield of scintillators 11 made of different materials, the intensities of the fluorescence emitted after excitation are significantly different. In terms of physical mechanism, when the scintillator 11 is excited by γ-photons, internal electrons undergo energy level transitions, and when they return to the ground state from the excited state, energy is released in the form of fluorescence. Factors such as the bandgap width and electron mobility of the material affect the energy conversion efficiency, and thus influence the fluorescence intensity.

[0059] These differences in fluorescence intensity are further reflected in the pulse signal amplitudes collected by the backend electronics system 3. With high-precision pulse amplitude analysis technology, the electronics system 3 strictly discriminates the amplitude characteristics of each pulse signal according to the pre-set correspondence relationship model between different scintillator materials and pulse amplitudes, so as to accurately determine the scintillator material to which it belongs. Through multi-channel signal acquisition, digital processing, and complex algorithm operations, combined with the geometric layout information of the detector array, the incident position of γ-photons is accurately traced back, and finally high-resolution position detection of γ-photons is achieved using an optical fiber detector, meeting the stringent requirements in fields such as nuclear physics experiments and nuclear facility safety monitoring.

[0060] The technical solution of the present invention provides an operation method: using scintillators 11 with the same volume but different materials to emit pulse signals with different amplitudes for detection work.

[0061] The present invention can also have other technical solutions: in an extended solution, it is also feasible to use scintillators 11 with different volumes but the same material. The same material ensures the coherence of basic physical properties, while the volume difference will result in different photon capture and energy conversion efficiencies, and thus when irradiated, pulse signals with different amplitudes are generated. Furthermore, by using scintillators 11 with different volumes and different materials, the double variables are superimposed, which further enriches the differentiation of pulse amplitudes and fully meets diverse detection requirements.

[0062] The present invention can also utilize the different decay times of different crystals to emit light, resulting in different signal waveforms, to identify which crystal the optical signal transmitted by the same optical fiber bundle comes from, thereby determining the position. For example, CsI(Tl) (decay time 1020 ns) and LYSO (decay time 42 ns) are selected.

[0063] When considering the actual working conditions, the applicable conditions must be carefully considered. In a complex and changing nuclear radiation environment, the ray energy and flux fluctuate constantly. The detector not only needs to ensure a sensitive response but also accurately distinguish signals. In the present invention, the pulse average amplitude is selected to achieve the discrimination purpose. Compared with the pulse decay as a characteristic, the pulse average amplitude has better stability and stronger anti-interference ability, and can accurately highlight the pulse characteristics corresponding to each scintillator 11 in the noisy radiation background noise.

[0064] Example 2, as Figure 4 shown, a preparation method of a position-sensitive core fiber detector includes the following steps:

[0065] S1: Process the material of the protective shell into a cylindrical shape, polish its interior, and weld and seal one end of the protective shell;

[0066] S2: Select scintillators of different materials and process them into cylindrical shapes of the same volume. Process the optical glass light guide rods into cylindrical shapes, and arrange the scintillators and the optical glass light guide rods in a sandwich structure of one scintillator and one optical glass light guide rod in sequence, and then install them into the protective shell;

[0067] S3: Arrange multiple metal-coated optical fibers to form an optical fiber bundle, wrap and fix it with a stainless steel metal coil on the outside, make its end faces lie on the same plane, and fix both ends of the metal-coated optical fibers respectively with a high-temperature resistant adhesive;

[0068] S4: Align one end of the optical fiber bundle with the opening of the protective shell, connect them with a high-temperature resistant sealant on the outside of the connection. Align the other end of the optical fiber bundle with the incident window end of the photomultiplier tube, and connect them with a high-temperature resistant sealant on the outside of the connection;

[0069] S5: Connect the photomultiplier tube, preamplifier, main amplifier, and multi-channel pulse amplitude analyzer to complete the preparation of the position-sensitive core fiber detector.

[0070] In an embodiment of the present invention, the processing flow of the position-sensitive core fiber detector is as follows:

[0071] The first step: Processing of the protective shell.

[0072] Inconel600 metal material with a smaller gamma photon cross section is selected to make the protective shell. This material has good high temperature resistance, high pressure performance and corrosion resistance, and can adapt to the harsh environment in the reactor. First, it is processed into a tube with an inner diameter of 2mm, an outer diameter of 3mm, and a length of 75mm. In order to simplify the assembly of the scintillator later, the inner diameter is processed to 2.1mm. Then the internal grinding and polishing work is carried out to improve the efficiency of the front-end probe and ensure that more fluorescent photons can be transmitted to the back-end electronics system. Through the Smank abrasive flow polishing technology, with the help of a special tooling structure, the soft abrasive is squeezed from the discharge port into the inner hole of the protective tube. Because the extrusion diameter is larger than the discharge diameter, the soft abrasive can maintain a certain pressure in the tube, and even in the middle and end of the tube, there is enough grinding force to achieve inner wall grinding and polishing. After grinding, one end is closed by laser welding, and the bottom end is closed with a thickness of 1mm, which can effectively withstand the high temperature and high pressure in the reactor and ensure the stability of the weld.

[0073] Step 2: Assemble the scintillator and the optical glass light guide rod.

[0074] GAGG (HL), LYSO, LSO, and YAP materials were selected to make scintillators. The scintillators of the four different materials were processed into cylindrical shapes with an outer diameter of 2mm and a height of 3mm. At the same time, three cylindrical quartz optical glass light guide rods with an outer diameter of 2mm and a length of 20mm were processed. A gap was formed between the outer diameter of the cylinder and the inner diameter of the protective shell to facilitate the placement of materials into the protective shell. First, the first scintillator GAGG (HL) was placed in the protective shell, and then the first light guide rod was placed. Then, the materials were placed in the protective shell in the order of the second scintillator LYSO, the second light guide rod, the third scintillator LSO, the third light guide rod, and the fourth scintillator YAP. The first piece to be installed is the first scintillator GAGG (HL). It has a large light yield, so it is arranged in the front. The remaining scintillators are arranged in order according to the size of the light yield to optimize the photon collection and transmission effect.

[0075] Step 3: Metal-coated optical fibers are assembled into optical fiber bundles.

[0076] Gold-coated optical fiber is selected for signal transmission. The SFS400 / 440 / 510G optical fiber of Fibergate has an inner core diameter of 400μm, a cladding diameter of 440μm, and an outer coating diameter of 510μm. 19 gold-coated optical fibers are neatly arranged into a bundle, and the outer surface is tightly wrapped and fixed with a stainless steel metal coil to keep both ends of the optical fiber bundle flat and all optical fiber end faces in the same plane. Then, high-temperature resistant glue is used to fix both ends to ensure the stability of the optical fiber bundle structure and provide reliable protection for subsequent signal transmission. The outer diameter of the processed optical fiber bundle is about 2.6mm-2.7mm.

[0077] Step 4: Connect the probe and fiber optic bundle, the photomultiplier tube and fiber optic bundle.

[0078] Connect one end of the optical fiber bundle to the open end of the protective shell, and use high-temperature resistant glue to bond them from the side of the connection port to ensure a firm connection and smooth signal transmission. At the same time, connect the other end of the optical fiber bundle to the incident window of the photomultiplier tube, and also use high-temperature resistant glue to bond them from the side of the connection port to ensure that the two are tightly connected so as to efficiently convert optical signals into electrical signals.

[0079] Step 5: Connect the photomultiplier tube and the electronics system.

[0080] Carefully check the interface type and compatibility between the photomultiplier tube and the electronics system, and prepare a connecting cable with good shielding performance. Firmly connect the output end of the photomultiplier tube to the input end of the electronics system and fix it for protection. Turn on the pulse amplitude measurement function module of the electronics system, set the appropriate range and resolution according to the output characteristics of the photomultiplier tube, and build a model of the corresponding relationship between the signal pulse amplitude and different detection conditions. Calibrate the synchronization of the response time of the two, trigger and measure the delay time with a pulse generator, set the compensation parameters accordingly, and verify the stability of the response time under different pulse frequencies and intensities. After completing the connection and preliminary settings, conduct an overall system test, and optimize the electronic system parameters, photomultiplier tube operating voltage, etc. based on the results, until the average pulse amplitude can be used to accurately distinguish different output signals. At this point, the processing and assembly of the one-dimensional position-sensitive core fiber detector is completed, and the detection work can be carried out after the calibration of the signal pulse amplitude and response time is completed.

[0081] The sixth step is to calibrate the fiber optic detector.

[0082] When calibrating the gamma signal response of the detector, first prepare a gamma ray source with known activity and energy (such as cesium 137, cobalt 60), a lead shield, a high-precision data acquisition card, and supporting computers and calibration software. Fix the detector on the experimental platform and align it with the ray source, and adjust the working voltage of the photomultiplier tube and the data acquisition parameters. For energy calibration, first irradiate with a cesium 137 source at low intensity, collect signals and draw an energy spectrum to determine the preliminary relationship between pulse amplitude and energy, and then repeat the operation with a cobalt 60 source and fit the precise curve. For response time calibration, use a high-precision pulse generator to simulate the signal, measure the delay between the trigger time and the start time of the detector output signal, and change the parameters many times to statistically analyze the response characteristics. If the detector has a position-sensitive function, let the ray source irradiate along the different lateral positions of its sensitive area, record the data and establish a model of the relationship between position and output signal. Finally, verify the repeatability through multiple calibration experiments under the same conditions. If the result difference exceeds the allowable range, check and optimize the experimental device and system parameters until a stable and accurate calibration result is obtained to ensure the accuracy and reliability of the detector's measurement of gamma signal response.

[0083] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention according to these technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the invention.

Claims

1. A position-sensitive core optical fiber detector, characterized in that: It comprises a probe (1), an optical fiber bundle (2) and an electronic system (3), wherein the probe (1), the optical fiber bundle (2) and the electronic system (3) are connected in sequence externally using a high temperature resistant sealant (4); The probe (1) comprises a scintillator (11), an optical glass light guide rod (12) and a protective shell (13); the scintillator (11) and the optical glass light guide rod (12) are arranged in sequence in a sandwich structure and are placed inside the protective shell (13); The optical fiber bundle (2) comprises a metal-coated optical fiber (21), a high-temperature-resistant adhesive (22), and a stainless steel metal coil (23); The electronic system (3) comprises a photomultiplier tube (31), a preamplifier (32), a main amplifier (33) and a multi-channel pulse amplitude analyzer (34) which are connected in sequence.

2. A position-sensitive core optical fiber detector according to claim 1, characterized in that: The scintillator (11), the optical glass light guide rod (12) and the protective shell (13) are all made of high temperature resistant materials.

3. A position-sensitive core optical fiber detector according to claim 1, characterized in that: The scintillator (11) and the optical glass light guide rod (12) are both cylindrical, the protective shell (13) is cylindrical with one end open and the other end closed, and the outer diameters of the scintillator (11) and the optical glass light guide rod (12) match the inner diameter of the protective shell (13).

4. A position-sensitive core optical fiber detector according to claim 1, characterized in that: A plurality of the metal coated optical fibers (21) are arranged into a bundle, and the end faces of all the metal coated optical fibers (21) are located in the same plane.

5. The position-sensitive core optical fiber detector according to claim 1, characterized in that: The position-sensitive core optical fiber detector is used to detect the position information of a gamma signal or a neutron signal. When the scintillator (11) is made of a gamma-sensitive material, the position detection of the gamma signal is achieved; when the scintillator (11) is made of a neutron-sensitive material, the detection of the neutron position signal is achieved.

6. A position-sensitive core optical fiber detector according to claim 1, characterized in that: The electronic system (3) adopts two different analysis and discrimination methods: pulse amplitude discrimination method and decay time discrimination method.

7. The position-sensitive core optical fiber detector according to claim 1, characterized in that: Under high temperature and high pressure conditions, the optical fiber bundle (2) uses metal-coated optical fibers (21); under non-high temperature conditions, the optical fiber bundle (2) uses wave-shift optical fibers to change the wavelength of incident light, thereby achieving total reflection of side-incident light, which is beneficial to long-distance transmission of signals.

8. A method for preparing a position-sensitive core optical fiber detector according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Process the material of the protective shell into a cylindrical shape, grind and polish the inside thereof, and weld and seal one end of the protective shell; S2: Select scintillators of different materials and process them into cylindrical shapes of the same volume, process the optical glass light guide rod into a cylindrical shape, and arrange the scintillators and the optical glass light guide rod in sequence according to a sandwich structure of one scintillator and one optical glass light guide rod, and then install them into a protective shell; S3: Arrange multiple metal-coated optical fibers to form an optical fiber bundle, wrap and fix them with a stainless steel metal coil on the outside so that their end faces are located on the same plane, and fix the two ends of the metal-coated optical fiber respectively with a high-temperature resistant adhesive; S4: align one end of the optical fiber bundle with the opening of the protective shell, and use a high temperature resistant sealant to connect the outside of the connection; align the other end of the optical fiber bundle with the incident window end of the photomultiplier tube, and use a high temperature resistant sealant to connect the outside of the connection; S5: Connect the photomultiplier tube, preamplifier, main amplifier and multi-channel pulse amplitude analyzer to complete the preparation of the position-sensitive core fiber optic detector.

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