Position sensitive core fiber probe and preparation method thereof

Abstract

The application discloses a position-sensitive type core optical fiber detector and a preparation method thereof, and relates to the field of radiation detection.The position-sensitive type core optical fiber detector comprises a probe (1), an optical fiber bundle (2) and an electronic system (3), and the probe (1), the optical fiber bundle (2) and the electronic system (3) are sequentially connected by using high-temperature-resistant sealing glue (4) externally; 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 in a sandwich structure and placed in the protective shell (13); the optical fiber bundle (2) comprises a metal-coated optical fiber (21), high-temperature-resistant adhesive glue (22) and a stainless steel coil (23). The application solves the problems that the existing optical fiber detector cannot be used for detection work under high-temperature, high-pressure and high-intensity radiation conditions, and the existing optical fiber detector can only realize flux detection and cannot be used for position detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiation detection, in particular to a position sensitive core optical fiber detector and a preparation method thereof. BACKGROUND

[0002] The core detection technology is mainly used for nuclear reactor power monitoring and core condition monitoring. By measuring the neutron signal, gamma signal or both in the core, the working state of the reactor core is understood, and the reactor is ensured to operate within a safe range.

[0003] At present, the equipment used for reactor core gamma detection mainly includes self-powered gamma detector (SPGD). SPGD is a new type of detector, which has the characteristics of not needing external power supply, miniaturization and simple structure, and can be used for the detection of gamma signals in the core under high temperature and high pressure conditions. However, SPGD is only suitable for high flux conditions and is not suitable for detection under low flux conditions. It needs a reactor with sufficient power and sufficient flux to output signals, and cannot realize precise position information detection.

[0004] Optical fiber detector is a new type of detector that has appeared in recent years. Optical fiber detector can provide real-time data about core temperature, neutron flux density and thermal power due to its instantaneous characteristics. It can also be used to monitor the consumption of nuclear fuel, and by analyzing gamma ray information, the fuel fissile products can be evaluated to optimize the use and replacement strategy of the fuel. 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 measures to reduce the impact of the accident. The main body of this detector is composed of an optical fiber, and a detection material is coated on the top end of the optical fiber. Radiation particles interact with the detection material and produce a fluorescence signal. The optical signal is transmitted to the photomultiplier tube at the other end of the optical fiber through total reflection of the optical fiber, and is converted into an electrical signal, which is analyzed and output by the post-electronics system. At the same time, neutron optical fiber detectors and gamma optical fiber detectors have appeared. Optical fiber detectors have the characteristics of small size and simple structure, but cannot be used for detection under high temperature, high pressure and strong radiation conditions. The detection material is difficult to withstand high temperature under high temperature conditions, and the optical fiber will harden under strong radiation conditions. Moreover, the optical fiber detector can only realize flux detection and cannot be used for position detection. SUMMARY

[0005] To address the aforementioned shortcomings of existing technologies, this invention proposes a position-sensitive reactor core fiber optic detector and its fabrication method, which enables radiation measurements at different points on a single detection fiber optic detector. This detector, used in reactor cores, can solve the problem of multi-point radiation measurements within confined spaces, thus providing a more accurate reflection of the reactor core's operating status. It also overcomes the limitations of existing fiber optic detectors, which cannot be used for detection under high-temperature, high-pressure, and high-irradiation conditions, and which can only perform flux detection, not position detection.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: a position-sensitive core fiber optic detector, comprising a probe, a fiber bundle, and an electronics system, wherein the probe, fiber bundle, and electronics system are sequentially connected externally using high-temperature resistant sealant;

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

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

[0009] The electronic system includes a photomultiplier tube, a preamplifier, a main amplifier, and a multichannel pulse amplitude analyzer connected in sequence.

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

[0011] Furthermore, both the scintillator and the optical glass light guide are cylindrical, and the protective shell is a cylindrical shape with one end open and the other end closed, and the outer diameters of the scintillator and the optical glass light guide are 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 the metal-coated optical fibers are located in the same plane.

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

[0014] Furthermore, the electronic system employs two different analysis and discrimination methods: pulse amplitude discrimination and decay time discrimination.

[0015] Furthermore, under high temperature and high pressure conditions, the fiber bundle uses metal-coated optical fiber; under non-high temperature conditions, the fiber bundle uses wave-shifting optical fiber to change the wavelength of the incident light, achieving total internal reflection of light incident from the side, which is beneficial for long-distance signal transmission.

[0016] The present invention also employs the following technical solution: a method for fabricating a position-sensitive core fiber optic detector, comprising the following steps:

[0017] S1: The material of the protective shell is processed into a cylindrical shape, its interior is polished, and one end of the protective shell is welded and sealed.

[0018] S2: Select scintillators made of different materials and process them into cylinders of the same volume. Process the optical glass light guide rod into a cylinder. Arrange the scintillators and optical glass light guide rods in a sandwich structure of one scintillator and one optical glass light guide rod, and then put them into the protective shell.

[0019] S3: Arrange multiple metal-coated optical fibers to form an optical fiber bundle, wrap and fix it with stainless steel metal coils on the outside so that its end faces are on the same plane, and fix the two ends of the metal-coated optical fibers respectively with high temperature resistant adhesive.

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

[0021] S5: Connects the photomultiplier tube, preamplifier, main amplifier and multichannel pulse amplitude analyzer to complete the fabrication of the position-sensitive core fiber optic detector.

[0022] The beneficial effects of this invention are as follows: This invention provides a position-sensitive reactor core fiber optic detector, which has the characteristics of high temperature resistance, high pressure resistance, radiation resistance, small size, simple structure, anti-interference, and high sensitivity. It provides a new method for detecting the position information of radiation signals in the confined space of the reactor core under harsh environments of high temperature, high pressure, and strong radiation.

[0023] The technical solution of this invention enables real-time online detection of the location information of radiation signals under one-dimensional spatial conditions. Using materials responsive to gamma signals, such as GAGG and LSO, gamma location information detection can be achieved; replacing the scintillation material with neutron-sensitive materials such as CLYC and CLLB allows for the detection of neutron signals. By arranging the detector in a two-dimensional array, the location information of gamma signals in three-dimensional space can be detected.

[0024] In the back-end electronics system, the present invention can also employ two different technical solutions: pulse amplitude discrimination method and signal attenuation time discrimination method. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the location-sensitive core fiber optic detector, an example of the present invention.

[0026] Figure 2 This is a partial structural diagram of the probe of the position-sensitive core fiber optic detector of the present invention.

[0027] Figure 3 This is a view of the fiber bundle end face of the position-sensitive core fiber detector of the present invention.

[0028] Figure 4 This is a flowchart illustrating the fabrication method of the position-sensitive core fiber optic detector, an example of the present invention.

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

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

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

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

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

[0034] The electronic system 3 includes a photomultiplier tube, a preamplifier, a main amplifier, and a multichannel pulse amplitude analyzer connected in sequence.

[0035] The scintillator 11, optical glass light guide 12, and protective shell are all made of high-temperature resistant materials. Inorganic scintillator materials have high melting points and can withstand the high temperatures and pressures inside the reactor core during core detection operations. For example, the melting points of halide scintillator crystals are all above 600℃, while Ce... 3+The melting points of the novel doped scintillators are generally around 2000℃. The optical glass light guide rod 12 is mainly made of quartz, and the protective shell of the probe is made of metal, so it can withstand high temperature and high pressure working environments.

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

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

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

[0039] If the temperature resistance of the detector is not a major requirement in actual use, but there is a need for long-distance transmission, then wave-shifting fiber can be used to change the wavelength of the incident light, so that light incident from the side can also undergo total internal reflection, which is beneficial for long-distance signal transmission.

[0040] The position-sensitive core 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 can detect the position of gamma signals; when the scintillator 11 uses a neutron-sensitive material, it can detect the position of neutron signals.

[0041] The electronic system 3 employs two different analysis and discrimination methods: pulse amplitude discrimination and decay time discrimination.

[0042] Under high temperature and high pressure conditions, the fiber bundle 2 uses a metal-coated fiber 21; under non-high temperature conditions, the fiber bundle 2 uses a wave-shifting fiber to change the wavelength of the incident light, thereby achieving total internal reflection of the light incident from the side, which is beneficial for long-distance signal transmission.

[0043] The technical solution of this invention enables real-time online detection of the location information of radiation signals under one-dimensional spatial conditions. Using materials responsive to gamma signals, such as GAGG and LSO, gamma location information detection can be achieved; replacing the scintillation material with neutron-sensitive materials such as CLYC and CLLB allows for the detection of neutron signals. By arranging the detector in a two-dimensional array, the location information of gamma signals in three-dimensional space can be detected.

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

[0045] The probe 1 includes a scintillator 11, an optical glass light guide 12, and a protective shell;

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

[0047] The first scintillator 111 is made of GAGG (HL), with a light yield of 54,000 ph / MeV and a density of 6.63 g / cm³. 3 The decay time is 150 ns, and the melting point is 1850℃;

[0048] The second scintillator 112 is made of LSO material, with a light yield of 26,000 ph / MeV and a density of 7.4 g / cm³. 3 The decay time is 40 ns, and the melting point is 2150℃;

[0049] The optical glass light guide rod 12 is made of quartz material;

[0050] The protective shell is made of Inconel 600. Inconel 600 has excellent corrosion resistance and performs exceptionally well in many corrosive environments. Whether in high-temperature oxidizing environments or environments containing various corrosive media such as strong acids and strong alkalis, it can effectively resist corrosion. With a melting point of 1400℃, it can maintain good mechanical properties and stability at high temperatures. Inconel 600 can withstand extreme in-pile corrosion environments and high-temperature conditions, ensuring that the internal scintillator 11 material and optical glass light guide rod 12 will not deform or be damaged due to high temperatures.

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

[0052] The optical fiber used in fiber bundle 2 is gold-plated fiber. Gold-plated fiber is fiber with an Au metal layer coated on its surface. This coating improves heat resistance and resistance to harsh environments. The metal-coated fiber not only retains the fiber's mechanical strength but also withstands static fatigue caused by long-term tensile loads. The principle is that the coated metal layer is molecularly bonded to the fiber cladding, thus possessing extremely high mechanical properties. Gold plating exhibits excellent temperature adaptability, operating stably in environments ranging from high temperatures of 700℃ to extreme cold of -269℃. The chemical stability of Au itself makes it resistant to corrosion from acids, alkalis, salts, and other chemicals, and it has strong oxidation resistance; even after prolonged use, the gold plating layer will not oxidize. Furthermore, gold-plated fiber has high strength and good flexibility. The gold plating layer, tightly bonded to the fiber, enhances its mechanical strength and makes it less prone to breakage under tensile and bending forces. Moreover, its excellent fatigue resistance allows it to withstand long-term repeated stress, extending its service life.

[0053] The electronic system includes a photomultiplier tube, a preamplifier, a main amplifier, and a multichannel pulse amplitude analyzer connected in sequence.

[0054] The photomultiplier tube used is an end-window type photomultiplier tube with a circular shape for the photocathode surface area.

[0055] This invention is based on the following principle: After entering the radiation field, the one-dimensional position-sensitive core fiber optic detector will have γ photons incident on the probe 1, pass through the protective shell and reach the inside of the probe 1. The γ photons will excite the scintillator 11 to emit fluorescence. The generated fluorescence will be transmitted to the photocathode part of the photomultiplier tube through the fiber bundle 2. The photomultiplier tube will convert the optical signal into an electrical signal. After further processing by the subsequent electronic system 3, an analyzable electrical signal will be formed. This process realizes the detection of γ photons.

[0056] The probe 1 of the one-dimensional position-sensitive core fiber optic detector has a protective shell containing two scintillators 11 (first scintillator 111 and second scintillator 112) made of different materials and an optical glass light guide rod 12, arranged in a row to form a sandwich structure. The purpose of this structure is to ensure that, under the same gamma dose, the scintillators 11 receive the same gamma photon flux because they have the same volume. Under the same gamma flux conditions, the fluorescence intensities emitted by the first scintillator 111 and the second scintillator 112 differ, resulting in different signal pulse amplitudes generated by the back-end electronics system 3. By analyzing the amplitude of a series of pulse signals through the electronics system 3, it is possible to identify which scintillator material emitted each pulse signal, thereby determining the position of the gamma signal and realizing the position detection of gamma photons using a fiber optic detector.

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

[0058] Under the same gamma flux incident conditions, scintillators 11 made of different materials exhibit significantly different fluorescence intensities after excitation due to differences in intrinsic properties such as atomic structure, energy level distribution, and fluorescence quantum yield. From a physical perspective, when scintillators 11 are excited by gamma photons, internal electrons undergo energy level transitions. Upon de-excitation back to the ground state, they release energy in the form of fluorescence. Factors such as the material's band gap and electron mobility affect the energy conversion efficiency, thus influencing the fluorescence intensity.

[0059] These differences in fluorescence intensity are further reflected in the signal pulse amplitude acquired by the back-end electronics system 3. Utilizing high-precision pulse amplitude analysis technology, the electronics system 3 rigorously identifies the amplitude characteristics of each pulse signal according to a pre-defined model of the correspondence between different scintillator materials and pulse amplitude, thereby accurately determining the scintillator material to which it belongs. Through multi-channel signal acquisition, digital processing, and complex algorithm calculations, combined with the geometric layout information of the detector array, the incident position of the gamma photon is accurately traced back, ultimately achieving high-resolution position detection of gamma photons using fiber optic detectors, meeting the stringent requirements of 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 of the same volume but different materials to emit pulse signals of different amplitudes for detection.

[0061] This invention can also have other technical solutions: In an extended solution, using scintillators 11 of different volumes but the same material is also feasible. The same material ensures the consistency of basic physical properties, while volume differences lead to different photon capture and energy conversion efficiencies, thus generating pulse signals of varying amplitudes when stimulated by radiation. Furthermore, using scintillators 11 of different volumes and materials, with the superposition of these two variables, further enriches the differentiated performance of pulse amplitudes, comprehensively meeting diverse detection needs.

[0062] This invention can also utilize the different decay times of light emitted by different crystals, resulting in different signal waveforms, to identify which crystal the optical signal transmitted in the same fiber bundle originates from, thereby determining its location. For example, CsI(Tl) (decay time 1020ns) or LYSO (decay time 42ns) can be selected.

[0063] When considering actual operating conditions, the applicable conditions must be carefully considered. In the complex and ever-changing nuclear radiation environment, the energy and flux of radiation fluctuate constantly, and the detector must ensure both sensitive response and accurate signal discrimination. In this invention, pulse averaging amplitude is selected to achieve the discrimination purpose. Compared with pulse attenuation as a characteristic, pulse averaging amplitude has better stability and stronger anti-interference ability, and can accurately highlight the pulse characteristics corresponding to each scintillator 11 in noisy radiation background noise.

[0064] Example 2, as Figure 4 As shown, a method for fabricating a position-sensitive core fiber optic detector includes the following steps:

[0065] S1: The material of the protective shell is processed into a cylindrical shape, its interior is polished, and one end of the protective shell is welded and sealed.

[0066] S2: Select scintillators made of different materials and process them into cylinders of the same volume. Process the optical glass light guide rod into a cylinder. Arrange the scintillators and optical glass light guide rods in a sandwich structure of one scintillator and one optical glass light guide rod, and then put them into the protective shell.

[0067] S3: Arrange multiple metal-coated optical fibers to form an optical fiber bundle, wrap and fix it with stainless steel metal coils on the outside so that its end faces are on the same plane, and fix the two ends of the metal-coated optical fibers respectively with high temperature resistant adhesive.

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

[0069] S5: Connects the photomultiplier tube, preamplifier, main amplifier and multichannel pulse amplitude analyzer to complete the fabrication of the position-sensitive core fiber optic detector.

[0070] In one embodiment of the present invention, the fabrication process of the position-sensitive core fiber detector is as follows:

[0071] Step 1: Processing the protective shell.

[0072] The protective shell is made of Inconel 600 metal, a material with a small cross-section for gamma photons. This material possesses excellent resistance to high temperatures and pressures, as well as corrosion resistance, enabling it to withstand the harsh environment inside the reactor. First, it is machined into a tubular shape with an inner diameter of 2mm, an outer diameter of 3mm, and a length of 75mm. For ease of assembly of the scintillator later, the inner diameter is machined to 2.1mm. Then, internal grinding and polishing are performed to improve the efficiency of the front-end probe, ensuring more fluorescent photons can be transmitted to the back-end electronics system. Using Smank abrasive flow polishing technology and a specialized tooling structure, soft abrasive is extruded from the outlet 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 inside the tube, providing sufficient grinding force even in the middle and end sections to achieve internal wall polishing. After grinding, one end is sealed using laser welding, with a bottom sealing thickness of 1mm. This effectively withstands the high temperature and pressure inside the reactor, ensuring the stability of the weld.

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

[0074] Scintillators were fabricated using GAGG(HL), LYSO, LSO, and YAP materials. These four scintillators were machined into cylindrical shapes with an outer diameter of 2mm and a height of 3mm. Simultaneously, three cylindrical quartz optical glass light guides with an outer diameter of 2mm and a length of 20mm were fabricated. A clearance fit was formed between the outer diameter of the cylinders and the inner diameter of the protective shell to facilitate the insertion of materials into the shell. First, the first GAGG(HL) scintillator was placed into the protective shell, followed by the first light guide. Then, materials were sequentially placed into the protective shell in the following order: second LYSO scintillator, second light guide, third LSO scintillator, third light guide, and fourth YAP scintillator. The first scintillator, GAGG(HL), was placed first due to its high light yield, and the remaining scintillators were arranged according to their light yield to optimize photon collection and transmission.

[0075] Step 3: Assemble the metal-coated optical fibers into an optical fiber bundle.

[0076] Gold-plated optical fibers were selected for signal transmission. The SFS400 / 440 / 510G model fiber from Feibo Gaide has a core diameter of 400μm, a cladding diameter of 440μm, and an outer coating diameter of 510μm. Nineteen gold-plated fibers were neatly bundled together and tightly wrapped and secured with stainless steel coils to ensure the fiber bundle's ends were flat and all fiber end faces were on the same plane. High-temperature resistant adhesive was then used to fix both ends, ensuring the fiber bundle structure was stable and providing reliable protection for subsequent signal transmission. The resulting fiber bundle has an outer diameter of approximately 2.6mm-2.7mm.

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

[0078] Connect one end of the fiber optic bundle to the open end of the protective shell, using high-temperature resistant adhesive from the side of the connection port to ensure a secure connection and smooth signal transmission. Simultaneously, connect the other end of the fiber optic bundle to the entrance window of the photomultiplier tube, again using high-temperature resistant adhesive from the side of the connection port to ensure a tight connection, thus efficiently converting the optical signal into an electrical signal.

[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 shielded connection cables with good performance. Securely connect the output end of the photomultiplier tube to the input end of the electronics system and ensure proper protection. Enable the pulse amplitude measurement function module of the electronics system, and set an appropriate range and resolution based on the output characteristics of the photomultiplier tube. Construct a model showing the correspondence between signal pulse amplitude and different detection conditions. Calibrate the synchronization of the response time of both systems by triggering and measuring the delay time using a pulse generator. Set compensation parameters accordingly and verify the stability of the response time under different pulse frequencies and intensities. After completing the connection and initial setup, conduct overall system testing. Optimize the electronics system parameters and the photomultiplier tube operating voltage based on the results until the average pulse amplitude can accurately distinguish different output signals. At this point, the one-dimensional position-sensitive core fiber optic detector is fabricated and assembled. After completing the calibration of the signal pulse amplitude and response time, detection work can begin.

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

[0082] To calibrate the detector's gamma signal response, prepare a gamma-ray source with known activity and energy (such as cesium-137 or cobalt-60), a lead shield, a high-precision data acquisition card, and supporting computer and calibration software. Fix the detector on the experimental platform and align it with the gamma-ray source, adjusting the photomultiplier tube's operating voltage and data acquisition parameters. Perform energy calibration by first irradiating the detector with a cesium-137 source at low intensity, acquiring the signal, and plotting the energy spectrum to determine the preliminary relationship between pulse amplitude and energy. Repeat the process with a cobalt-60 source and fit a precise curve. For response time calibration, use a high-precision pulse generator to simulate the signal, measuring the trigger time and the detector's output signal start time delay. Statistical analysis of the parameters after multiple parameter changes yields the response characteristics. If the detector has a position-sensitive function, irradiate the detector with the gamma-ray source at different lateral positions along its sensitive region, recording the data to establish a model of the relationship between position and output signal. Finally, repeatability was verified through multiple calibration experiments under the same conditions. If the results differed beyond the allowable range, the experimental setup and system parameters were checked and optimized until stable and accurate calibration results were obtained, so as to ensure the accuracy and reliability of the detector's response to gamma signals.

[0083] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of the invention.

Claims

1. A position-sensitive core fiber optic detector, characterized in that, It includes a probe (1), an optical fiber bundle (2), and an electronics system (3), which are connected sequentially externally using a high-temperature resistant sealant (4); The probe (1) includes a scintillator (11), an optical glass light guide (12), and a protective shell. The scintillator (11) and the optical glass light guide (12) are arranged in a sandwich structure and placed inside the protective shell. The fiber bundle (2) includes a metal-coated fiber (21), a high-temperature adhesive (22), and a stainless steel metal coil (23). The electronic system (3) includes a photomultiplier tube, a preamplifier, a main amplifier and a multichannel pulse amplitude analyzer connected in sequence; The electronic system (3) employs two different analysis and discrimination methods: pulse amplitude discrimination method and decay time discrimination method. The electronic system (3) uses high-precision pulse amplitude analysis technology to identify the amplitude characteristics of each pulse signal according to the preset correspondence model between different scintillator materials and pulse amplitude, thereby accurately determining the scintillator material to which it belongs. Through multi-channel signal acquisition, digital processing and algorithm calculation, combined with the geometric layout information of the detector array, the incident position of γ photon is accurately traced back, and finally the high-resolution position detection of γ photon using fiber optic detector is achieved. Under high temperature and high pressure conditions, the fiber bundle (2) uses metal-coated fiber (21); under non-high temperature conditions, the fiber bundle (2) uses wave-shifting fiber to change the wavelength of the incident light, so as to achieve total internal reflection of the light incident from the side, which is beneficial for long-distance signal transmission.

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

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

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

5. A position-sensitive core fiber optic detector according to claim 1, characterized in that, The position-sensitive core fiber detector is used to detect the position information of gamma signals or neutron signals. When the scintillator (11) is made of gamma-sensitive material, it can detect the position of gamma signals; when the scintillator (11) is made of neutron-sensitive material, it can detect the position of neutron signals.

6. A method for fabricating a position-sensitive core fiber optic detector as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: The material of the protective shell is processed into a cylindrical shape, its interior is polished, and one end of the protective shell is welded and sealed. S2: Select scintillators made of different materials and process them into cylinders of the same volume. Process the optical glass light guide rod into a cylinder. Arrange the scintillators and optical glass light guide rods in a sandwich structure of one scintillator and one optical glass light guide rod, and then put them into the protective shell. S3: Arrange multiple metal-coated optical fibers to form an optical fiber bundle, wrap and fix it with stainless steel metal coils on the outside so that its end faces are on the same plane, and fix the two ends of the metal-coated optical fibers respectively with high temperature resistant adhesive. S4: Align one end of the fiber bundle with the opening of the protective shell, and connect the connection with high-temperature resistant sealant on the outside. Align the other end of the fiber bundle with the entrance window of the photomultiplier tube, and connect the connection with high-temperature resistant sealant on the outside. S5: Connects the photomultiplier tube, preamplifier, main amplifier and multichannel pulse amplitude analyzer to complete the fabrication of the position-sensitive core fiber optic detector.

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