Fusion radiation imaging diagnostic device based on lead tungstate array

Abstract

The invention discloses a fusion radiation imaging diagnostic device based on a lead tungstate array. Comprising a radiation collimator, a scintillator array, a photoelectric converter, a data acquisition unit, an imaging system and a shielding assembly. The radiation collimator is made into a porous grid structure by adopting a high-density heavy metal thick target and is locked at a diagnosis window at the lower part of the fusion device; the scintillator array is a pixelated array formed by a plurality of lead tungstate scintillator units, is arranged in one-to-one correspondence with the collimation micropores, and converts incident high-energy radiation into scintillation light signals; the photoelectric converter is in pixel coupling with the scintillator array pixel pair and converts an optical signal into an electric signal; the data acquisition unit acquires and preprocesses the electric signals and then transmits the electric signals to the imaging system to realize two-dimensional or three-dimensional imaging of radiation distribution. The high density, high atomic number and excellent radiation resistance of lead tungstate are utilized, and a high length-diameter ratio collimation structure is combined, so that the problems of insufficient radiation resistance and lack of spatial resolution capability in a high-flux neutron-gamma mixed radiation environment are solved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fusion diagnostic technology, specifically relating to a fusion radiation imaging diagnostic device based on a lead tungstate array. Background Technology

[0002] Fusion devices based on deuterium-tritium reactions (such as CFEDR) will produce a large number of 14 MeV neutrons and 3.5 MeV alpha particles. These high-energy neutrons generate strong gamma radiation through scattering and trapping in structural materials (W, Be, stainless steel, etc.). Furthermore, escape electrons are easily generated in deuterium-tritium fusion, and the bremsstrahlung radiation of these escape electrons may also produce high-energy photons. Information on the spatial distribution of gamma radiation is crucial for core power distribution, first-wall sputtering / deposition, and early warning of structural damage. However, existing imaging or detection technologies cannot simultaneously meet the following requirements: firstly, high throughput and high dose (102) of the reactor. 3 -10 5 The system must be able to operate stably for extended periods in environments with radiation levels of Gy / year; secondly, it must possess high spatial / temporal resolution and imaging capabilities; and thirdly, it must be able to adapt to the complex neutron + gamma-ray mixed background within a fusion reactor. Traditional CCD / CMOS visual cameras fail rapidly in such high-radiation environments; while conventional scintillators (such as NaI and CsI) can detect gamma rays, they have weak radiation resistance, short lifespans, and are difficult to pixelate into camera arrays. Therefore, there is an urgent need for a radiation-resistant, high-speed, pixelated radiation imaging system specifically designed for fusion reactor environments.

[0003] In existing fusion devices, visible light and near-infrared cameras based on CCD or CMOS detectors are widely used for imaging and diagnostics of plasma boundary luminescence, impurity spectral lines, and visible radiation from the first wall. This technology is mature and widely used in tokamak experimental devices, offering advantages such as intuitive imaging, high spatial resolution, and relatively simple system structure. However, these detectors are essentially semiconductor devices, extremely sensitive to high-energy neutrons and gamma radiation, especially when the cumulative irradiation dose reaches 10... 3 -10 4 Beyond Gy, problems such as a sharp increase in dark current, pixel failure, and permanent device damage occur, making it difficult to operate stably in reactor-level fusion devices (such as CFETR / CFEDR) for extended periods. Furthermore, this type of imaging is only sensitive to visible or near-infrared light and cannot directly reflect the distribution of gamma radiation generated by neutron action in the core and structural materials, thus exhibiting significant limitations in critical diagnostic tasks such as core power distribution and structural irradiation load monitoring.

[0004] Currently, the diagnosis of neutron and gamma radiation in fusion devices mainly employs point-based measurements using detectors such as ionization chambers, plastic scintillators, NaI(Tl), or HPGe to obtain neutron flux, gamma spectrum, or time evolution information. This type of technology is relatively mature in radiation measurement, with high sensitivity, and is suitable for flux and spectrum analysis. However, its detection methods are typically single-point or have a limited number of detection channels, lacking spatial resolution and unable to obtain two-dimensional or three-dimensional distribution information of gamma radiation in the reactor core or first wall region. Furthermore, commonly used scintillator materials (such as NaI and CsI) are prone to permanent discoloration and light yield decay under high-dose gamma and neutron irradiation, resulting in limited lifespan; high-resolution semiconductor detectors (such as HPGe) have stringent operating environment requirements and are difficult to adapt to the intense radiation, high temperatures, and restricted maintenance conditions of reactor-level systems. Therefore, this type of technology cannot meet the future needs of fusion reactors for long-term, spatially resolved radiation imaging diagnostics.

[0005] In the design of ITER and related fusion devices, neutron camera or neutron collimation channel diagnostic schemes have been proposed and partially implemented. These schemes measure neutron flux from different perspectives using multiple collimation channels to invert the neutron source distribution in the reactor core. This type of technology can directly reflect the intensity of the fusion reaction and is of great significance for power distribution diagnosis. However, neutron camera systems are complex in structure and large in size, with extremely high requirements for collimation structure and shielding design, resulting in high system costs and engineering implementation difficulties. At the same time, the neutron detector itself must deal with extremely high neutron flux and irradiation damage issues, leading to high long-term stability and maintenance costs. Furthermore, this type of technology mainly targets neutron source distribution and lacks imaging capabilities for the secondary gamma radiation distribution generated by neutron-material interactions, making it difficult to achieve intuitive and visual monitoring of first-wall sputtering, structural irradiation hotspots, and anomalous radiation events.

[0006] For the high-flux neutron and gamma radiation coexisting environment that is a long-term problem in reactor-level nuclear fusion devices, existing diagnostic technologies generally suffer from insufficient radiation resistance, inability to operate stably for extended periods, lack of spatial resolution imaging capabilities, or complex system structures and high engineering implementation difficulties. The core technical problem this invention aims to solve is: how to achieve a long-term stable imaging diagnostic device and method with high spatial and temporal resolution, applicable to measuring the radiation field distribution in key reactor areas (such as the reactor core and the vicinity of the first wall) under high-dose neutron-gamma mixed radiation environments. Specifically, the technical challenges to be addressed include: first, the maintenance and recovery of the performance of detection materials under high irradiation conditions; second, the effective detection and direction selection of gamma radiation in complex backgrounds; third, ensuring high resolution while balancing engineering feasibility and ease of maintenance in the imaging system; and fourth, this invention does not aim for direct neutron imaging, but rather for spatial imaging diagnosis of the gamma field generated by neutron-material interactions and plasma radiation. Summary of the Invention

[0007] To address the above technical problems, this invention proposes a fusion radiation imaging diagnostic device based on a lead tungstate array. Through synergistic optimization of material selection, structural design, and imaging architecture, it achieves stable, high-resolution imaging diagnosis of high-energy X-ray or gamma-ray radiation distribution. The specific technical solution is as follows:

[0008] A fusion radiation imaging diagnostic device based on a lead tungstate array, comprising:

[0009] A radiation collimator is used to define the incident direction of radiation and to achieve selection and spatial resolution of radiation signals in a specific spatial region. The radiation collimator has a porous grid structure with multiple parallel through-collimation micro-holes inside.

[0010] The scintillator array, composed of multiple inorganic lead tungstate scintillator units, is used to generate energy deposition and form a scintillator light signal by electromagnetic interaction of incident high-energy radiation after it has been collimated by the radiation collimator. The scintillator array is designed as a pixelated array structure, wherein each lead tungstate scintillator unit corresponds one-to-one with the collimation micro-hole of the radiation collimator, and the rear end face of the radiation collimator is in close contact with the scintillator array.

[0011] A photoelectric converter, coupled to the scintillator array, is used to detect the light signal generated by the scintillator array and convert it into an electrical signal. The photoelectric converter is configured to correspond one-to-one with each pixel unit of the scintillator array.

[0012] The data acquisition unit is electrically connected to the photoelectric converter and is used to acquire, preprocess, and transmit the electrical signals.

[0013] An imaging system, communicatively connected to the data acquisition unit, is used to reconstruct the acquired radiation signals to obtain two-dimensional or three-dimensional imaging results of the radiation distribution in a specific region of the fusion device; and,

[0014] A shielding assembly for supporting the radiation collimator, the scintillator array, and the photoelectric converter, and for shielding stray radiation from the plasma or the device structure.

[0015] The present invention has the following beneficial effects:

[0016] First, this scheme selects lead tungstate as the core detection material. This material has high density, high atomic number and excellent radiation resistance. It can maintain stable scintillation performance under the long-term combined effect of high flux neutrons and gamma radiation. Moreover, the color centers generated after irradiation can recover naturally at room temperature, which has a certain degree of radiation damage recovery capability. This avoids the problem of permanent degradation of conventional scintillators in high-dose environments, thus significantly improving the lifespan and reliability of the diagnostic system in the fusion reactor environment.

[0017] Secondly, this scheme constructs a pixelated array of lead tungstate scintillators. To achieve high spatial resolution imaging, a heavy metal collimator is installed at the front end of the device. The collimator body is made of high-density tungsten alloy or lead to effectively shield neutron and gamma-ray background from non-line-of-sight directions. The collimator is designed as a porous grid structure, with its aperture strictly corresponding to the pixel size of the scintillator at the rear end. To obtain excellent directional selectivity, the collimating aperture has a high aspect ratio, and the aperture length is typically designed to limit the collimator's field of view to a specific range, ensuring that each scintillator pixel receives radiation only from a specific spatial solid angle. The front end of the collimator is precisely aligned and fixed to the detector array via a mechanical frame, and the entire assembly is encapsulated in a shielded shell to maintain constant temperature operation and reduce thermal noise. This design enables two-dimensional or three-dimensional imaging diagnosis of the spatial distribution of gamma radiation. Compared to existing point detection technologies that can only obtain local flux or energy spectrum information, this scheme can directly obtain spatial distribution images of radiation intensity in the reactor core and first wall region, providing more intuitive and comprehensive diagnostic information for power distribution inversion, sputtering source location, and local irradiation hotspot identification.

[0018] Furthermore, this solution utilizes the fast response and wide dynamic range of lead tungstate scintillators to high-energy photons and high radiation fluxes. While ensuring high spatial resolution, it enables real-time measurements with high temporal resolution, covering various operating conditions from steady-state operation to transient events (such as power fluctuations and anomalous radiation enhancement). This overcomes the limitations of traditional visible light cameras, which cannot operate for extended periods under high radiation environments, and the response time and engineering complexity of neutron camera systems. Specifically, this invention employs a high-density inorganic scintillator suitable for the intense radiation environment of fusion as the radiation conversion medium, preferably lead tungstate. Its high effective atomic number, fast response time, and strong radiation tolerance enable it to operate stably for extended periods under high radiation flux and high cumulative dose conditions, thus overcoming the problems of easy degradation and limited dynamic range of traditional semiconductor detectors and conventional scintillators in fusion environments.

[0019] Furthermore, this solution employs a modular structural design, functionally separating the scintillator array, readout unit, and collimation component. This facilitates replacement and maintenance during planned overhauls of the fusion device, reducing overall system operation and maintenance costs while enhancing the diagnostic system's adaptability to future reactor operating conditions. Additionally, this invention improves the adaptability of the radiation imaging diagnostic system under wide dynamic range and high count rate conditions. Through the overall design of the scintillator material properties, photoelectric readout method, and signal processing link, the system can adapt to the operating conditions where radiation intensity varies across multiple orders of magnitude during fusion device operation, thus meeting the dual diagnostic requirements of steady-state operation and transient anomaly monitoring.

[0020] In summary, this invention outperforms existing fusion radiation diagnostic technologies in terms of radiation resistance, imaging spatial resolution, time response capability, system reliability, and engineering feasibility. It can provide a novel radiation imaging diagnostic method for reactor-level fusion devices that is stable in the long term, has strong spatial resolution, and is suitable for high-irradiation environments. Attached Figure Description

[0021] Figure 1 This is an overall structural diagram of the present invention;

[0022] Figure 2 This is a frontal view of the radiation collimator;

[0023] Figure 3 This is a schematic diagram of the assembly of a single lead tungstate crystal, a photoelectric converter, and a signal transmission line.

[0024] Figure 4 This is a structural diagram of the device application of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0026] This invention proposes a fusion radiation imaging diagnostic device based on a lead tungstate array, such as... Figure 1 As shown, the device includes: a radiation collimator 5, a scintillator array 6, a photoelectric converter 7, a data acquisition unit 8, an imaging system 9, and a shielding assembly 10. This invention is used for spatial distribution imaging diagnosis of high-energy radiation generated during the operation of a fusion device.

[0027] Inside the fusion device, such as Figure 4 and Figure 1 As shown, where Figure 1 for Figure 4The invention is a magnified version of a portion of the structure. The fusion plasma 1 operates under magnetic confinement and is surrounded by a vacuum chamber 3. The vacuum chamber 3 has a first wall and a cladding layer inside to withstand plasma particles and thermal loads. Plasma outside the closed magnetic surface enters the divertor region along magnetic field lines, forming an X-point proximity region 2 with magnetic separation characteristics. During device operation, the X-point proximity region 2 and related divertor structures will generate X-ray or gamma-ray radiation signals due to high-temperature plasma radiation, high-Z impurity radiation, bremsstrahlung radiation generated by the interaction of escaped electrons with structural materials, radiation directly generated in the fusion plasma, and the interaction of high-energy neutrons or alpha particles with the first wall, cladding layer, and divertor-related structures. This invention is installed within the lower diagnostic window. These radiation signals 4 generated by fusion enter the radiation imaging detection unit through diagnostic holes and a radiation collimator 5 in the cladding structure. The radiation collimator 5 is used to define the radiation incident direction, thereby achieving selection and spatial resolution of radiation signals in specific spatial regions. The collimated radiation signal is incident on a scintillator array 6, which consists of multiple inorganic lead tungstate scintillator units. These units are used to deposit energy and form a scintillation light signal from the incident high-energy radiation through electromagnetic interaction. The scintillator array 6 can be designed as an array, pixelated, or modular structure according to diagnostic needs to achieve spatially resolved detection of the radiation signal. The light signal generated by the scintillator array is further detected and converted into an electrical signal by a photoelectric converter 7 coupled to it. The photoelectric converter 7 can be a photomultiplier tube, a silicon photomultiplier, an avalanche photodiode, or a combination thereof to adapt to different count rates and dynamic ranges. The electrical signal is acquired, preprocessed, and transmitted to a remote imaging system 9 via a data acquisition unit 8. The imaging system 9 is used to reconstruct the acquired radiation signal, thereby obtaining two-dimensional or three-dimensional imaging results of the radiation distribution in a specific area of ​​the fusion device, enabling diagnosis and monitoring of the plasma operating state and the radiation characteristics of the first wall or divertor region. In addition, the shielding assembly 10 is used to support the radiation collimator 5, the scintillator array 6 and the photoelectric converter 7, and to shield stray radiation from the plasma or device structure before the signal is transmitted to the remote processing system.

[0028] This invention combines an inorganic scintillator array with a radiation collimation structure. The collimator body is made of a high-density heavy metal thick target with high radiation attenuation capability, preferably a high-density tungsten alloy (W-Ni-Fe), to effectively shield neutrons and high-energy gamma rays from non-direct-view directions. The collimator body is designed as a porous grid structure, with multiple parallel through-hole collimation micro-holes precisely machined inside. The array arrangement and cross-sectional dimensions of these collimation micro-holes correspond strictly one-to-one with the pixel units of the lead tungstate scintillator array at the rear. To ensure high spatial resolution and strict directional selectivity for high-energy fusion radiation signals, the collimation micro-holes have a high aspect ratio (high aspect ratio), ensuring that each scintillator unit receives only direct rays from a specific plasma region or a specific location on the first wall. Mechanically, the radiation collimator 5 is locked at the observation window. The rear end face of the collimator is in close contact with the lead tungstate scintillator array 6 to ensure strict alignment between the collimation micro-aperture and the optical center of the pixel unit below. A photoelectric converter 7 is installed behind each scintillator. The converted electrical signal is transmitted via cable to the data acquisition unit 8, and then via cable to the imaging system 9. A side view of the detailed radiation collimator 5 is shown below. Figure 1 As shown, the front view is as follows Figure 2 As shown, the square aperture serves as the radiation path, with a scintillator array 6 and a photoelectric converter 7 placed behind it. A radiation imaging diagnostic architecture suitable for fusion devices is constructed. Through the rational design of the scintillator size, arrangement, and collimation geometry, the radiation signals can be effectively distinguished spatially, thereby achieving spatially resolved imaging of the radiation distribution in specific regions of the fusion device (such as the plasma boundary, the first wall, or the divertor region), rather than being limited to single-point measurements or overall integration measurements.

[0029] The scintillator array 6 is constructed by using lead tungstate scintillators as a pixelated array. First, large lead tungstate crystals are precisely cut, ground, and polished into individual crystal strips. Multiple crystal strips are then closely arranged to form an M×N pixel array. To prevent crosstalk between adjacent pixels, a high-reflectivity layer is wrapped or coated on the side of each crystal strip. The rear end of the crystal array is coupled pixel-to-pixel to a radiation-resistant photoelectric converter array (such as a silicon photomultiplier tube (SiPM) array or a multi-anode photomultiplier tube) using either a radiation-resistant optical adhesive or a glue-free mechanical dry coupling press-fit method. The combination of a single lead tungstate crystal and photoelectric converter 7 is as follows: Figure 3 As shown. The photoelectric converter 7 is located at one end of a single lead tungstate crystal, and the photoelectric converter 7 is connected to the signal transmission line.

[0030] Based on the foregoing, this invention includes, but is not limited to: a general technical solution for fusion radiation imaging diagnosis based on high-density inorganic scintillators; scintillator material selection and equivalent replacement forms suitable for strong radiation environments; an imaging diagnostic structure combining scintillator arrays and radiation collimation structures; and radiation imaging methods and system integration approaches for the operating conditions of fusion devices. Any equivalent replacements or improvements made to scintillator materials, structural forms, readout methods, or imaging architectures based on the above technical concepts should be included within the scope of protection of this invention. Without departing from the technical concept of this invention, the lead tungstate scintillator used in the fusion radiation imaging diagnostic scheme based on inorganic scintillators described in this invention can be considered as a preferred embodiment. The material is not limited to lead tungstate. Those skilled in the art can, according to the actual needs of the strong radiation environment of the fusion device, equivalently replace it with other inorganic scintillator materials having similar high density, high effective atomic number, fast response characteristics, and radiation tolerance. Simultaneously, the structural form of the scintillator, the array method, the type of optical signal readout device, the specific implementation of the radiation collimation structure, and the position of the detector mounting window can all be adjusted or replaced without changing the basic principles and diagnostic functions of radiation imaging. All such equivalent replacements or improvements should be considered reasonable variations of the technical solution of this invention and fall within the protection scope of this invention.

Claims

1. A fusion radiation imaging diagnostic device based on a lead tungstate array, characterized in that, include: The radiation collimator (5) is used to limit the radiation incident direction and realize the selection and spatial resolution of radiation signals in a specific spatial region. The radiation collimator (5) is a porous grid structure with multiple parallel through collimation micro-holes inside. The scintillator array (6) is composed of multiple inorganic lead tungstate scintillator units, which are used to generate energy deposition and form scintillator light signals by electromagnetic interaction of the incident high-energy radiation after it has been collimated by the radiation collimator (5). The scintillator array (6) is designed as a pixelated array structure, wherein each lead tungstate scintillator unit corresponds one-to-one with the collimation micro-hole of the radiation collimator (5), and the rear end face of the radiation collimator (5) is in close contact with the scintillator array (6). A photoelectric converter (7) is coupled to the scintillator array (6) and is used to detect the light signal generated by the scintillator array (6) and convert it into an electrical signal. The photoelectric converter (7) is configured to correspond one-to-one with each pixel unit of the scintillator array (6). The data acquisition unit (8) is electrically connected to the photoelectric converter (7) and is used to acquire, preprocess and transmit the electrical signal; The imaging system (9) is communicatively connected to the data acquisition unit (8) and is used to reconstruct the acquired radiation signals to obtain two-dimensional or three-dimensional imaging results of the radiation distribution in a specific area of ​​the fusion device. as well as The shielding assembly (10) is used to support the radiation collimator (5), the scintillator array (6) and the photoelectric converter (7), and to shield stray radiation from plasma or device structure.

2. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The main body of the radiation collimator (5) is made of high-density tungsten alloy.

3. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The array arrangement of the collimated micro-holes and the cross-sectional size of each hole correspond strictly one-to-one with the pixel units of the scintillator array (6), ensuring that each scintillator unit receives only direct rays from a specific plasma region or a specific location on the first wall.

4. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The scintillator array (6) is formed by precisely cutting and polishing large lead tungstate crystals into independent crystal strips, arranging multiple crystal strips closely to form an M×N pixel array, and wrapping or coating a high reflectivity layer on the side of each crystal strip to prevent light crosstalk between adjacent pixels.

5. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The scintillator array (6) is coupled pixel-to-pixel to the photoelectric converter (7) via optical adhesive or mechanical coupling at its rear end.

6. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The photoelectric converter (7) is a photomultiplier tube, a silicon photomultiplier, an avalanche photodiode, or a combination thereof.

7. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The shielding assembly (10) encapsulates the radiation collimator (5), the scintillator array (6), and the photoelectric converter (7) entirely within the shielding housing.

8. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The data acquisition unit (8) transmits the preprocessed signal to the imaging system (9) at the remote end via a cable.

9. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The scintillator array (6), the photoelectric converter (7), and the radiation collimator (5) adopt a modular structure design.

10. The fusion radiation imaging diagnostic device based on a lead tungstate array according to claim 1, characterized in that, The lead tungstate scintillator has high density, high atomic number and excellent radiation resistance. It can maintain stable scintillation performance under the long-term combined action of high flux neutrons and gamma radiation, and the color centers generated after irradiation can recover naturally at room temperature.

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