Neutron radiation detection device based on superconducting quantum interferometer and particle accelerator

Abstract

The present application relates to the technical field of particle acceleration, in particular to a neutron radiation detection device based on a superconducting quantum interferometer and a particle accelerator, the neutron radiation detection device comprising a neutron conversion mechanism, a magnetic flux coupling mechanism and a superconducting quantum interferometer arranged in sequence, the magnetic flux coupling mechanism comprising a superconducting induction coil adjacent to the neutron conversion mechanism and a magnetic flux concentrator adjacent to the superconducting quantum interferometer, so as to utilize the ultrahigh sensitivity of the superconducting quantum interferometer to the magnetic signal of the order of picotesla, combine the neutron conversion mechanism and the magnetic flux coupling mechanism, and construct an efficient conversion link of "neutron-charged particle-magnetic flux-electrical signal", wherein the superconducting quantum interferometer greatly improves the neutron radiation detection sensitivity, realizes accurate detection of neutron radiation, and is further provided with a signal processing mechanism connected with the electrical signal of the superconducting quantum interferometer, so as to realize real-time monitoring of the neutron flux change and provide early warning for the safety of nuclear facilities.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of particle acceleration technology, in particular to a neutron radiation detection device based on a superconducting quantum interferometer and a particle accelerator. BACKGROUND

[0002] Particle Accelerator as a key equipment in modern scientific research and industrial applications, its core function is to use electromagnetic field to accelerate charged particles (such as protons, electrons, heavy ions, etc.) to extremely high energy. In the running process, the high-energy particles accelerated will not only have physical reactions with the preset target material to achieve the specific research or application goal, but also have complex nuclear reactions with the pipe wall, focusing magnet, correction element and other structural materials of the accelerator beam transmission line, such as neutron capture reaction, nuclear fission reaction, spallation reaction, etc. These nuclear reactions will produce neutron radiation with extremely wide energy coverage (from MeV level of thermal neutron to GeV level of fast neutron), and the amount of neutron radiation is usually much higher than that of photon beam radiation at the same period. The essential reason for this phenomenon is that when high-energy charged particles interact with atomic nuclei, the original stable structure of the atomic nucleus is easily broken, causing nuclear rearrangement or release, thereby causing the generation of a large number of neutrons.

[0003] The existing particle accelerator can effectively block most of the outflow of neutron radiation through heavy radiation protection measures, but in the long-term operation process of the particle accelerator, it is very important to ensure the safety of personnel, the stable operation of equipment and the safety of the environment to monitor the neutron radiation level in real time at specific places outside the protective shield to ensure that it is always below the national limit value.

[0004] Traditional neutron detectors are mainly divided into three categories according to working principle: gas detector, scintillator detector and semiconductor detector. The detection efficiency of gas detector is greatly affected by gas pressure and purity, gas molecules are easy to decompose or ionize in high radiation dose environment, leading to long-term stability decline, equipment volume is large and sensitive to vibration, etc., which is difficult to meet the detection needs of high precision and miniaturization. In the complex radiation field of particle accelerators and other devices, γ rays can easily cause interference fluorescence signals in scintillator detectors, making it difficult to distinguish between neutron and γ ray signals; at the same time, the long-term radiation of scintillator material will cause the decay of light-emitting efficiency (radiation damage), affecting the detection accuracy and service life. The semiconductor detector has low direct neutron detection efficiency (which needs to rely on the doped layer), thermal noise and 1 / f noise in low-temperature environment significantly affect the detection sensitivity, and the anti-radiation ability of semiconductor material is weak, which limits its application in strong radiation and low flux neutron scenarios.

[0005] It can be seen that although the traditional neutron detector has been widely used in some scenarios, it has obvious limitations in detection performance and adaptability to complex environments, and the neutron detection technology urgently needs to make breakthroughs in detection sensitivity, energy resolution, environmental adaptability and the like. SUMMARY

[0006] The purpose of the present application is to provide a superconducting quantum interferometer-based neutron radiation detection device, aiming to avoid environmental interference and improve neutron radiation detection accuracy.

[0007] In order to achieve the above purpose, the present application provides a superconducting quantum interferometer-based neutron radiation detection device, which comprises a neutron conversion mechanism, a magnetic flux coupling mechanism, a superconducting quantum interferometer and a signal processing mechanism, the magnetic flux coupling mechanism comprises a superconducting induction coil and a magnetic flux concentrator arranged adjacent to each other along the neutron transmission direction, the neutron conversion mechanism is located at one end of the superconducting induction coil away from the magnetic flux concentrator, the superconducting quantum interferometer is arranged at one end of the magnetic flux concentrator away from the superconducting induction coil, and the signal processing mechanism is electrically connected with the superconducting quantum interferometer.

[0008] Optionally, the neutron conversion mechanism comprises an incident layer and an exit layer, the incident layer is a planar thin film structure and has a thickness of 5-10 microns, one end of the exit layer away from the incident layer is provided with a lead-out structure, and the lead-out structure is arranged adjacent to the superconducting induction coil.

[0009] Optionally, the lead-out structure is a plurality of V-shaped grooves arranged in an array, the groove depth of the V-shaped grooves is 100-200 microns, the groove spacing between two adjacent V-shaped grooves is 50-100 microns, and the angle of the V-shaped grooves is set to an angle alpha and satisfies 60°≤alpha≤90°.

[0010] Optionally, the surface of the exit layer facing the superconducting induction coil is provided with a carbon ion implantation modified surface.

[0011] Optionally, one end of the superconducting induction coil is adjacent to the neutron conversion mechanism and is arranged at a first spacing, and the first spacing is 1-2 mm.

[0012] Optionally, the superconducting induction coil and the magnetic flux concentrator are coaxially installed, the magnetic flux concentrator is arranged with a variable diameter along the length direction, the input end is the large diameter end, the output end is the small diameter end, and the large diameter end is arranged adjacent to the superconducting induction coil.

[0013] Optionally, the superconducting quantum interference device is packaged in a shield, the superconducting quantum interference device is provided with a sensitive area adjacent to one end of the magnetic flux coupler, the shield is provided with an opening corresponding to the sensitive area, and the shield is a cryostat or a superconducting shield cylinder; and / or the magnetic flux coupler is provided with a plurality of transmission channels, and the plurality of transmission channels are arranged in an array and pass through both ends of the magnetic flux coupler in the length direction.

[0014] Optionally, the signal processing mechanism comprises a low-noise preamplifier, a data collector and a data analyzer, and the data collector is connected to the superconducting quantum interference device.

[0015] Optionally, the neutron radiation detection device further comprises a packaging shell provided with a packaging cavity, and the packaging shell is provided with a support structure corresponding to the neutron conversion mechanism, the magnetic flux coupling mechanism and the superconducting quantum interference device; the neutron conversion mechanism, the magnetic flux coupling mechanism and the superconducting quantum interference device are detachably arranged in the packaging cavity through the corresponding support structure.

[0016] The application further provides a particle accelerator comprising the neutron radiation detection device based on the superconducting quantum interference device.

[0017] The neutron radiation detection device based on the superconducting quantum interference device comprises a neutron conversion mechanism, a magnetic flux coupling mechanism and a superconducting quantum interference device arranged in sequence, the magnetic flux coupling mechanism comprises a superconducting induction coil adjacent to the neutron conversion mechanism and a magnetic flux concentrator adjacent to the superconducting quantum interference device, the superconducting quantum interference device is combined with the neutron conversion mechanism and the magnetic flux coupling mechanism to construct an efficient conversion link of "neutron-charged particle-magnetic flux-electrical signal" by using the super-high sensitivity of the superconducting quantum interference device to the magnetic signal of the order of picotesla, wherein the superconducting quantum interference device greatly improves the neutron radiation detection sensitivity and realizes accurate detection of neutron radiation, and the signal processing mechanism is further connected to the electrical signal of the superconducting quantum interference device, so as to realize real-time monitoring of the neutron flux change and provide early warning for nuclear facility safety. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the local partial structure of the neutron radiation detection device based on the superconducting quantum interference device.

[0019] In the figure: 100, a neutron radiation detection device based on a superconducting quantum interferometer; 10, a neutron conversion mechanism; 11, an incident layer; 13, an exit layer; 131, a lead-out structure; 13A, a V-shaped groove; 30, a magnetic flux coupling mechanism; 31, a superconducting induction coil; 33, a magnetic flux concentrator; 331, a large-diameter end; 333, a small-diameter end; 50, a superconducting quantum interferometer; 70, a signal processing mechanism; 71, a preamplifier; 73, a data collector; 75, a data analyzer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the technical scheme of the present application will be described clearly and completely below in combination with the drawings.

[0021] The present application provides a neutron radiation detection device 100 based on a superconducting quantum interferometer, which is applied to neutron detection in the field of particle accelerator technology. With the in-depth development of nuclear physics research towards high-precision spectroscopy analysis, precise monitoring of neutron radiotherapy dose in the medical field, and safety early warning of nuclear facilities, higher requirements are put forward for neutron detection technology. Compared with traditional neutron detection structures, breakthroughs are urgently needed in detection sensitivity, energy resolution, environmental adaptability and other aspects of neutron detection technology.

[0022] As shown in Figure 1 In order to achieve the above purpose, the present application provides a neutron radiation detection device 100 based on a superconducting quantum interferometer (hereinafter referred to as detection device 100), which comprises a neutron conversion mechanism 10, a magnetic flux coupling mechanism 30, a superconducting quantum interferometer 50 and a signal processing mechanism 70. The magnetic flux coupling mechanism 30 comprises a superconducting induction coil 31 and a magnetic flux concentrator 33 arranged adjacent to each other along the neutron transmission direction. The neutron conversion mechanism 10 is located at one end of the superconducting induction coil 31 away from the magnetic flux concentrator 33. The superconducting quantum interferometer 50 is arranged at one end of the magnetic flux concentrator 33 away from the superconducting induction coil 31. The signal processing mechanism 70 is electrically connected to the superconducting quantum interferometer 50.

[0023] The detection device 100 of the present application comprises a neutron conversion mechanism 10, a magnetic flux coupling mechanism 30 and a superconducting quantum interferometer 50 arranged in sequence. The magnetic flux coupling mechanism 30 comprises a superconducting induction coil 31 adjacent to the neutron conversion mechanism 10 and a magnetic flux concentrator 33 adjacent to the superconducting quantum interferometer 50. The superconducting quantum interferometer 50 is combined with the neutron conversion mechanism and the magnetic flux coupling mechanism to construct an efficient conversion link of "neutron-charged particle-magnetic flux-electrical signal" by utilizing the ultra-high sensitivity of the superconducting quantum interferometer 50 to the pico-tesla level magnetic signal. The superconducting quantum interferometer 50 greatly improves the neutron radiation detection sensitivity and realizes accurate detection of neutron radiation. In addition, the signal processing mechanism 70 is electrically connected to the superconducting quantum interferometer 50, thereby monitoring the neutron flux change in real time and providing early warning for the safety of nuclear facilities.

[0024] Understandably, the detection principle corresponding to the structure is that neutrons in the particle beam are incident on the neutron conversion mechanism 10 to generate charged particles. The charged particles move in the superconducting induction coil 31 to generate a magnetic field (electromagnetism). Then, they enter the superconducting quantum interference device 50 (SQUID) through the magnetic flux concentrator 33 to react to the radiation level according to the change in the magnetic field. The key point is the magnetic flux conversion between the magnetic flux concentrator and the superconducting quantum interference device 50 (SQUID). The signal transmission is "radiation → electrical signal → magnetic signal → signal output".

[0025] Understandably, the superconducting quantum interference device (SQUID) 50, as the most sensitive magnetic flux detection device currently available, possesses quantum-level detection capabilities for weak magnetic field changes. Combining it with neutron conversion technology and magnetic flux coupling technology to construct a novel neutron radiation detection device 100 effectively overcomes the performance bottlenecks of traditional detectors, providing a new technological path for achieving high-precision neutron radiation detection. The SQUID mentioned below refers to the superconducting quantum interference device 50.

[0026] Optionally, the neutron conversion mechanism 10 includes an incident layer 11 and an exit layer 13. The incident layer 11 is a planar thin film structure with a thickness of 5-10 μm. The exit layer 13 has an exit structure 131 at one end away from the incident layer 11, and the exit structure 131 is disposed adjacent to the superconducting induction coil 31.

[0027] In this embodiment, the design and implementation scheme of the neutron conversion mechanism 10 are as follows:

[0028] (1) Material selection: Example selection 6 Li or 10 B is the core conversion material, in which 6 Li is suitable for high energy resolution scenarios (where the energy dispersion of reaction products is small). 10 B is suitable for high-detection-efficiency scenarios (with a higher thermal neutron reaction cross section). To improve material performance, an isotope enrichment process is employed to... 6 Li abundance increased to 99.9% or 10 The abundance of boron was increased to 96%, ensuring the efficiency of the neutron reaction.

[0029] (2) Structural design: It is a double-layer structure: The incident layer 11 is a planar thin film located on the outermost side of the neutron conversion mechanism 10, directly facing the incident neutron, and is the first layer of material in contact with the neutron. The thickness is only 5-10 μm. The ultra-thin thin film structure prepared by magnetron sputtering process ensures high neutron transmittance; The exit layer 13 is located at the other end of the incident layer 11 away from the neutron incident surface. The exit layer 13 is made of the same material as the incident layer 11 (for example, it can be a high abundance layer). 6 Li / 10B), but the exit layer 13 is a block structure (thickness 100-200 pm), which is the core area of neutron nuclear reaction and charged particle generation.

[0030] The incident layer 11 and the exit layer 13 of the neutron conversion mechanism 10 are an integrated structure of the same material, without physical isolation joints, to avoid neutron reflection or leakage between layers. The two layers are commonly attached to an ultra-thin insulating substrate (such as aluminum nitride ceramic, thickness <50 pm), which only serves as a support and does not participate in neutron reactions.

[0031] The incident layer 11 receives neutrons, which undergo nuclear reactions in the incident layer 11 and the exit layer 13 to generate charged particles. The charged particles then exit through the exit layer 13 near one end of the superconducting induction coil 31, specifically through the lead-out structure 131. The lead-out structure 131 is designed to guide the charged particles generated by the nuclear reaction to pass through the wall of the lead-out structure 131 of the exit layer 13, reducing collisions with the material. The specific nuclear reaction process is as follows: 6 Taking the Li conversion layer as an example, incident neutrons react with 6 Li to generate 6 Li(n, a) 3 H reactions, and the generated alpha particles (energy 2.05 MeV) and 3 H nuclei (energy 2.73 MeV) move in opposite directions and enter the induction region of the magnetic flux coupling mechanism 30 after passing through the exit layer 13, inducing an induced current.

[0032] Among them, the structure form selection of the incident layer 11 and the exit layer 13 is flexible according to the neutron flux scenario.

[0033] Low flux scenario (such as nuclear facility leakage monitoring, flux <10 -6 n / (cm²·s)): Thin film conversion layer (total thickness <20 pm) is used to reduce neutron absorption and scattering and improve detection sensitivity.

[0034] High flux scenario (such as particle accelerator beam monitoring, flux >10 2 n / (cm²·s)): Block conversion layer (total thickness >150 pm) is used to increase the probability of neutron interaction with the material and improve signal strength.

[0035] Optionally, the lead-out structure 131 is an array of multiple V-shaped grooves 13A, the groove depth of the V-shaped groove 13A is 100-200 pm, the groove spacing between adjacent two V-shaped grooves 13A is 50-100 pm, and the angle of the V-shaped groove is set to angle a and satisfies 60°≤a≤90°.

[0036] In this embodiment, the lead-out structure 131 of the exit layer 13 is a block structure with V-shaped grooves (groove depth: 100-200 μm), and the V-shaped groove angle is designed to be 60°-90°, the groove spacing is 50-100 μm, and the structure is prepared by a photoetching and etching process. This structure can effectively reduce the energy loss of charged particles in the material inside, and improve the reaction product lead-out efficiency (more than 30% higher than the flat structure).

[0037] Among them, the V-shaped groove 13A does not involve the incident layer 11 (to avoid damaging its high transmittance), and is only processed inside the exit layer 13 on the side close to the superconducting induction coil 31. The groove body is almost through the entire thickness (100-200 μm) of the exit layer 13, but does not penetrate the incident layer 11, and finally forms a uniform distribution of “V-shaped groove 13A array” in the exit layer 13.

[0038] The opening direction of the V-shaped groove 13A is consistent with the direction of the charged particle motion, and the two inclined surfaces of the groove are respectively towards the inside of the exit layer 13, forming a structure of “wide outside and narrow inside”. This direction design can guide the α particles, 3 H nuclei (moving in the opposite direction) along the groove wall to exit, reducing the collision with the material.

[0039] The purpose of the V-shaped groove 13A is to improve the charged particle lead-out efficiency and reduce energy loss. This is because the energy of the charged particles (α particles, 3 H nuclei) generated by the reaction of neutrons and the conversion layer material is fixed (for example, 6 2.05 MeV α particles are generated by Li reaction), but the charged particles will lose energy due to collision when moving in the material inside the neutron conversion mechanism 10. If the energy loss is too much, it may not be able to penetrate the conversion layer to reach the superconducting induction coil 31, resulting in signal loss.

[0040] The V-shaped groove 13A reduces particle scattering, reduces the number of particles reflected in the opposite direction, and increases the penetration rate. At the same time, the V-shaped groove 13A increases the surface area of the exit layer 13, so that the reaction area of neutrons and materials is more dispersed, avoiding “particle congestion” (multiple particles moving and interfering with each other) caused by local reaction being too dense, and indirectly improving the neutron conversion efficiency.

[0041] Optionally, the surface of the exit layer 13 facing the superconducting induction coil 31 is set as a carbon ion implantation modified surface.

[0042] In this embodiment, the ion implantation modification is mainly for the exit side surface of the neutron conversion mechanism 10, that is, the side of the exit layer 13 opposite to the magnetic flux coupling mechanism 30 (specifically, the superconducting induction coil 31 adjacent thereto), that is, the side where the charged particles (exemplarily α particles, 3 H nuclei) generated by nuclear reaction penetrate the neutron conversion mechanism 10.

[0043] It should be noted that (1) the conversion layer emits side directly receives the energy transfer of neutron nuclear reaction (such as 6 Li(n,α) 3 H reaction releases 4.786 MeV energy), and the risk of lattice damage under long-term irradiation is the highest, and the modification can directly improve the radiation resistance of the core reaction region; (2) the charged particles need to pass out from the emitting side into the superconducting induction coil 31, and if the emitting side appears structural damage (such as lattice defects causing particle scattering) due to irradiation, the particle extraction efficiency will be reduced. The injection modification can maintain the flatness of the emitting side surface (referring to the purpose of "V-shaped groove type structure to reduce self-absorption"), and avoid signal attenuation.

[0044] Further, the design and implementation scheme of the magnetic flux coupling mechanism 30 is as follows.

[0045] Optionally, one end of the superconducting induction coil 31 is adjacent to the neutron conversion mechanism 10 and is arranged at a first interval, and the first interval is 1-2 mm, so as to ensure that the charged particle motion track can effectively pass through the coil magnetic field region.

[0046] In this embodiment, the superconducting induction coil 31 is a core component of the "magnetic flux coupling mechanism 30", and the installation position needs to meet the signal coupling requirement of the neutron conversion mechanism 10 and the magnetic flux transfer requirement of the magnetic flux concentrator 33 at the same time.

[0047] The specific position is: (1) relative to the position of the neutron conversion mechanism 10: adjacent to one side of the emitting layer 13 of the neutron conversion mechanism 10, the plane where the radial section of the superconducting induction coil 31 is located is parallel to the radial section of the emitting layer 13, and the interval between them is strictly controlled to be 1-2 mm. The distance design can ensure that the charged particles (alpha particles, 3 H nucleus) generated by the conversion layer can effectively pass through the magnetic field region of the superconducting induction coil 31, so as to avoid that the energy loss of the particles is too large to cause the induction signal to weaken.

[0048] (2) relative to the position of the magnetic flux concentrator 33: the superconducting induction coil 31 is adjacent to, spaced from and coaxially installed with the magnetic flux concentrator 33. The magnetic flux generated by the superconducting induction coil 31 can directly enter the magnetic flux concentrator 33, and then be output through the other end of the magnetic flux concentrator 33, so as to realize efficient transfer of the magnetic flux. The other end of the magnetic flux concentrator 33 corresponds to the magnetic flux sensitive region of the superconducting quantum interference device 50.

[0049] (3) position in the overall device: together with the magnetic flux concentrator 33 in the shielding part below, needs to be in the liquid helium temperature area of 4.2K to maintain the superconducting characteristics of the niobium titanium (NbTi) superconducting wire, and avoid energy loss or signal distortion caused by resistance.

[0050] Regarding the material selection of the superconducting induction coil 31: NbTi superconducting wire (diameter 50-100 pm) is used, which has a critical current density > 2 x 10 5 A / cm 2 at 4.2 K low temperature, and zero resistance, which can avoid energy loss during current transmission.

[0051] Regarding the parameter optimization of the material of the superconducting induction coil 31, the following is used.

[0052] Parameter 1. Number of turns: According to the detection sensitivity and response speed requirements, the number of turns is designed to be 50-200 turns. Increasing the number of turns can improve the induction sensitivity (about 10-15 V per turn of induction voltage), but will increase the inductance of the coil (the inductance value is proportional to the square of the number of turns), resulting in a decrease in response speed (response time < 1 ps). Through simulation calculation, the optimal number of turns is determined to be 100 turns, at which the sensitivity and response speed are balanced.

[0053] Parameter 2. Shape and size: A circular coil (diameter 5-10 mm) is used, the coil plane is parallel to the neutron conversion mechanism 10 emission layer 13, and the distance is controlled at 1-2 mm, which ensures that the charged particle motion trajectory can effectively pass through the coil magnetic field region.

[0054] Parameter 3. Preparation process: The NbTi wire is wound on an alumina ceramic skeleton using a precision winding machine, and the tension (5-10 g) is controlled during winding to avoid damage to the superconducting wire; after winding, low-temperature annealing treatment (temperature 600°C, holding time 2 hours) is performed to eliminate winding stress and improve superconducting performance.

[0055] Optionally, the superconducting induction coil 31 is coaxially installed with the magnetic flux concentrator 33, the magnetic flux concentrator 33 is provided with a variable diameter along the length direction and the input end is the large-diameter end 331 and the output end is the small-diameter end 333, and the large-diameter end 331 is arranged adjacent to the superconducting induction coil 31.

[0056] In this embodiment, the design and implementation scheme of the magnetic flux concentrator 33 is as follows.

[0057] Material selection: High magnetic permeability permalloy is used, which can efficiently concentrate magnetic flux.

[0058] Structural design: A conical hollow structure is used, the diameter of the large-diameter end 331 matches the diameter of the induction coil (5-10 mm), the diameter of the small-diameter end 333 matches the size of the magnetic flux sensitive region of the superconducting quantum interference device 50 (100-200 pm), and the length is 5-10 mm. This structure can concentrate and focus the magnetic flux generated by the induction coil to the sensitive region of the superconducting quantum interference device 50 (SQUID), and the magnetic flux transmission efficiency is improved to more than 80% (5 times higher than the detection structure without the magnetic flux concentrator 33).

[0059] The structure is designed to be conical for the following purposes: (1) to improve the magnetic flux transmission efficiency: the magnetic flux generated by the superconducting induction coil 31 (corresponding to the neutron signal) will naturally disperse outward. If it is directly transmitted to the SQUID (the sensitive area is only 100-200 pm), most of the magnetic flux will be lost. The conical structure collects and focuses the dispersed magnetic flux through the form of "large-diameter end 331 receiving and small-diameter end 333 outputting", improving the transmission efficiency and ensuring that the weak signal is not diluted. (2) to match the sizes of different components: the diameter of the induction coil is 5-10 mm (which needs to cover the range of charged particle movement), while the sensitive area of the SQUID is only 100-200 pm, with a size difference of 50-100 times. The large-diameter end 331 of the conical structure (diameter 5-10 mm) is adjacent to the superconducting induction coil 31, and the small-diameter end 333 (100-200 pm) is adjacent to the SQUID, acting as a "size adaptation bridge" to avoid signal loss due to size mismatch. (3) to reduce magnetic noise interference: the conical hollow structure can constrain the transmission path of the magnetic flux, making it focus only along the inside of the cone wall, reducing the interference of external stray magnetic fields (such as the weak magnetic field in the low-temperature dewar) on the signal, and avoiding cross-talk caused by magnetic flux leakage.

[0060] Preparation process: The permalloy blank is prepared by a powder metallurgy process, and after precise mechanical processing, a magnetic performance annealing treatment (temperature 1100°C, hydrogen protective atmosphere, heat preservation for 4 hours) is performed to improve the magnetic permeability and magnetic uniformity of the material.

[0061] Optionally, the superconducting quantum interference device 50 is packaged in a shielding member, the superconducting quantum interference device 50 is provided with a sensitive area adjacent to one end of the magnetic flux coupler, the shielding member is provided with a through opening corresponding to the sensitive area, and the shielding member is a low-temperature dewar or a superconducting shielding cylinder; and / or the magnetic flux coupler is provided with a plurality of transmission channels, the plurality of transmission channels are arrayed and all penetrate through both ends of the length direction of the magnetic flux coupler.

[0062] In this embodiment, the shielding member is a low-temperature dewar, and the magnetic flux concentrator 33 provided with a plurality of transmission channels is located inside the low-temperature dewar (together with the SQUID in the 4.2K liquid helium temperature zone), and the plurality of transmission channels are arrayed, with both ends of each transmission channel being arranged adjacent to the superconducting induction coil 31 and the superconducting quantum interference device 50 respectively, to ensure that each channel can efficiently transmit and focus the magnetic flux. Illustratively, the sensitive area of the superconducting quantum interference device 50 is provided with 4-8 SQUID detection units, and the sensitive area of each unit is aligned with the small-diameter end 333 of the magnetic flux concentrator 33 to facilitate the reception of the focused magnetic flux signal.

[0063] Further, the design and implementation scheme of the superconducting quantum interference device 50 (SQUID) is as follows.

[0064] (1) Type selection: Superconducting quantum interference device 50 (SQUID) is a superconducting electronic core element composed of Josephson junction and superconducting closed loop. According to the number of junctions, it can be divided into two types: DC-SQUID (double junction) and RF-SQUID (single junction). According to the application scenario requirements, DC-SQUID or RF-SQUID is selected.

[0065] DC-SQUID: The superconducting ring is composed of two Josephson junctions in parallel. When working, a direct current bias current is applied, and the output voltage changes periodically with the external magnetic flux. Its magnetic flux resolution can reach 10-15 (Φ0 is the magnetic flux quantum, about 2.07×10 -15 Wb), which is suitable for scenes with extremely high requirements for detection sensitivity and energy resolution (such as nuclear physics spectrum analysis and medical radiotherapy dose monitoring).

[0066] RF-SQUID: It is composed of a Josephson junction and a superconducting ring in series. When working, it is coupled through a radio frequency resonant cavity. The structure is simple and the cost is low. The magnetic flux resolution is about 10-13 , which is suitable for cost-sensitive and performance requirements moderate scenes (such as nuclear facility routine safety monitoring).

[0067] (2) Key parameter optimization (take DC-SQUID as an example) as follows.

[0068] Josephson junction design: Nb / Al-AlOx / Nb tunnel junction is used, junction area 1-5μm², junction resistance 5-10Ω, junction capacitance <1pF. Electron beam lithography and magnetron sputtering process are used to ensure the uniformity and stability of the junction parameters.

[0069] Superconducting ring design: A circular superconducting ring made of Nb material is used, with a diameter of 100-200μm, a ring width of 10-20μm, and a thickness of 50-100nm, to ensure that the critical current of the superconducting ring is >10μA and sensitive to external magnetic flux changes.

[0070] Low-temperature cooling scheme: Liquid helium immersion cooling is used, and the SQUID is packaged in a stainless steel low-temperature dewar tank. The effective volume of the dewar tank is 1-2L, the liquid helium evaporation rate is <0.5L / day, and continuous work can be realized for 5-7 days. For scenes that need long-term operation, a small refrigerator (such as a pulse tube refrigerator, minimum temperature 4.2K) can be used to realize closed-loop low-temperature cooling without frequent liquid helium replenishment.

[0071] Optionally, the signal processing mechanism 70 includes a low-noise preamplifier 71, a data collector 73, and a data analyzer 75, and the data collector 73 is in signal connection with the superconducting quantum interference device 50.

[0072] In this embodiment, the design and implementation of the signal processing mechanism 70 are as follows.

[0073] Regarding the low-noise preamplifier 71: 1. Circuit design: a differential amplification structure is adopted, and a low-temperature operational amplifier (such as AD745, noise voltage < 4 nV / Hz1 / 2) is selected as the core device. The working temperature is controlled at 77 K (liquid nitrogen temperature zone), reducing the influence of thermal noise.

[0074] 2. Gain setting: according to the SQUID output signal amplitude (usually 1-10 μV), the amplifier gain is set to 1000-10000 times, ensuring that the output signal amplitude reaches 1-10 V, meeting the input requirements of the data acquisition device 73.

[0075] 3. Filter design: a low-pass filter (cutoff frequency 1 MHz) and a band-stop filter (suppressing 50 Hz / 60 Hz power frequency interference) are set at the output end of the amplifier, further reducing noise.

[0076] Regarding data acquisition and processing: 1. Data acquisition device 73: a high-speed data acquisition device 73 (such as NIPCIe-6363) with a resolution of 16 bits or more and a sampling rate of > 10 MS / s is selected to realize real-time acquisition of the amplified signal.

[0077] 2. Signal processing algorithm: signal filtering: wavelet transform filtering algorithm is adopted to denoise the collected original signal and retain the characteristic information of the neutron signal; peak detection: threshold method (setting dynamic threshold, adaptive adjustment based on background noise amplitude) is used to identify the peak position of the neutron signal, record the signal amplitude and time information; energy calculation: according to the calibration relationship between signal amplitude and neutron energy (obtained through standard neutron source calibration), the energy of the incident neutron is calculated; pulse shape discrimination: based on the difference between the neutron signal (pulse width is narrow, about 10-100 ns) and the background noise signal (pulse width is wide, about 1-10 μs), digital pulse shape discrimination algorithm is adopted to eliminate background interference signals and improve detection accuracy.

[0078] 3. Result output and display: develop special data processing software to display neutron flux, energy distribution, count rate and other parameters in real time, and support data storage (format is CSV or HDF5) and historical data query, facilitating subsequent analysis.

[0079] Optionally, the detection device 100 further comprises a packaging shell provided with a packaging cavity, and the packaging shell is provided with support structures corresponding to the neutron conversion mechanism 10, the magnetic flux coupling mechanism 30 and the superconducting quantum interference device 50. The neutron conversion mechanism 10, the magnetic flux coupling mechanism 30 and the superconducting quantum interference device 50 are detachably arranged in the packaging cavity through the corresponding support structures.

[0080] ​In this embodiment, the packaging shell is the outermost shell of the detection device 100, which directly contacts the external environment and serves as the first shielding structure of the detection device 100. The shielding member is arranged between the packaging shell and the magnetic flux concentrator 33. The shielding member and the packaging shell are arranged in a nested and detachable structure. The packaging shell is exemplarily made of high magnetic permeability beryllium copper alloy (magnetic permeability μ ≈ 8000 μ0), which is used to package the neutron conversion mechanism 10, the magnetic flux coupling mechanism 30, the superconducting quantum interference device 50, and the shielding member for packaging the magnetic flux coupling mechanism 30 and the superconducting quantum interference device 50 together to shield external magnetic field interference such as the electromagnetic environment of a particle accelerator laboratory and the periphery of industrial equipment.

[0081] The detection device 100 also has a second shielding structure made of superconducting lead material (critical temperature 7.2 K). The second shielding structure can be arranged on the inner wall of the low-temperature dewar in which the SQUID is located, or an independent superconducting shielding cylinder can be arranged. The shielding member is located inside the outermost beryllium copper alloy shell. The second shielding structure is tightly attached to the outside of the low-temperature dewar or integrated into the dewar wall. The SQUID needs to be in a low-temperature environment (≤ 7.2 K) to maintain superconducting properties.

[0082] The detection device 100 also has a converging structure for neutron detection, which is a conical permalloy magnetic flux concentrator 33. The magnetic flux concentrator 33 is independently installed between the superconducting induction coil 31 and the SQUID. One end of the magnetic flux concentrator 33 is adjacent to the superconducting induction coil 31 (diameter 5-10 mm), and the other end (small diameter end 333, diameter 100-200 μm) is opposite to the sensitive area of the SQUID and is located inside the low-temperature dewar.

[0083] The first shielding structure is used to shield external low-frequency magnetic fields (such as power frequency 50 Hz / 60 Hz electromagnetic fields) to avoid low-frequency noise interference with the magnetic flux coupling mechanism 30. The second shielding structure uses the Meissner effect to completely exclude high-frequency magnetic fields and electromagnetic radiation (such as radio frequency signals) while maintaining the stability of the low-temperature environment. The role of the converging structure is not to shield electromagnetic signals, but to focus the weak magnetic flux generated by the induction coil (corresponding to the neutron signal) to the sensitive area of the SQUID to improve the signal strength after signal transmission.

[0084] It can be understood that the overall structural framework of the detection device 100 is composed of four parts of the neutron conversion mechanism 10, the magnetic flux coupling mechanism 30, the superconducting quantum interference device 50 (SQUID) and the signal processing mechanism 70, and the functions and connection relationships of each part are as follows: the neutron conversion mechanism 10 is located at the front end of the detection device 100, directly receives the incident neutrons, and converts the neutrons into charged particles through nuclear reactions; the magnetic flux coupling mechanism 30 is adjacent to the neutron conversion mechanism 10, including a superconducting induction coil 31 and a magnetic flux concentrator 33, which converts the current change induced by the charged particles into a magnetic flux change and efficiently transmits it to the superconducting quantum interference device 50 (SQUID); the superconducting quantum interference device 50 (SQUID) is located at the end of the magnetic flux concentrator 33 away from the superconducting induction coil 31 and in the low-temperature dewar, used to receive the magnetic flux signal transmitted by the magnetic flux coupling mechanism 30, and convert the magnetic flux change into a voltage signal based on the Josephson effect; the signal processing mechanism 70 includes a low-noise preamplifier 71, a data collector 73 and a data analyzer 75, which realizes amplification, collection, analysis and result output of the SQUID output signal.

[0085] It can be understood that the above-mentioned detachable connection implementation form includes but is not limited to the combination structure of guide rail + positioning groove + locking pin, and the structure is designed according to actual installation requirements.

[0086] The specific working process is that the incident neutrons pass through the shell of the detection device 100 and enter the neutron conversion mechanism 10; the neutrons and the conversion layer material (exemplarily 6 Li, 10 B) of the neutron conversion mechanism 10 have a nuclear reaction, generating charged particles (alpha particles, 3 H nuclei); the charged particles move through the superconducting induction coil 31, inducing an induced current in the coil; the magnetic flux generated by the induced current is focused by the magnetic flux concentrator 33 and then transmitted to the SQUID sensitive area; the SQUID converts the magnetic flux change into a voltage signal and outputs it to the preamplifier 71; the preamplifier 71 amplifies and filters the signal and transmits it to the data collector 73; the data collector 73 collects the signal and transmits it to the computer, calculates the neutron flux, energy and other parameters through the signal processing algorithm, and finally displays and stores the results through software.

[0087] The detection device 100 of the present application can achieve the following core technical effects.

[0088] I. The detection sensitivity is greatly improved

[0089] The neutron conversion mechanism 10 adopts high-abundance 6 Li / 10 B material and V-shaped groove structure, and the neutron-charged particle conversion efficiency is improved to more than 70% (30% higher than the traditional flat conversion layer).

[0090] The superconducting induction coil 31 and the magnetic flux concentrator 33 are cooperatively designed to make the magnetic flux transmission efficiency reach more than 80%, combined with the ultra-high magnetic sensitivity (10-15 ) of the DC-SQUID, the minimum detectable neutron flux of the detection device 100 is as low as 5×10 -9 n / (cm²·s), which is two orders of magnitude higher than that of the traditional 3 He detector (the minimum detectable flux is about 10 -6 n / (cm²·s).

[0091] In the simulation experiment of nuclear reactor core leakage monitoring, the detection device 100 of the present application can realize stable detection when the neutron flux is 10 - 8 n / (cm²·s), while the signal of the traditional detector is submerged in noise and cannot be effectively identified.

[0092] II. The energy resolution is significantly optimized

[0093] The optimized design of the superconducting induction coil 31 parameters (100 turns, diameter 8mm) balances the sensitivity and response speed, and the signal distortion rate is reduced to <3%.

[0094] The conical structure of the magnetic flux concentrator 33 reduces the dispersion of magnetic flux, so that the measurement error of SQUID to the change of magnetic flux is <0.5%.

[0095] The low-noise amplification and wavelet transform filtering algorithm of the signal processing mechanism 70 further eliminate noise interference, and the energy resolution of the detection device 100 to thermal neutrons (0.025eV) is 3.2%, which is nearly twice that of the traditional scintillator detector (energy resolution is about 8%).

[0096] In the neutron energy spectrum analysis experiment, the detection device 100 of the present application can clearly distinguish the neutron signals with energy of 0.025eV (thermal neutron), 1MeV (fast neutron) and 10MeV (high-energy neutron), and the energy spectrum peak separation degree is >95%.

[0097] III. The adaptability to complex environment is comprehensively enhanced

[0098] Electromagnetic interference suppression: The multi-level shielding system (beryllium copper outer layer + superconducting lead inner layer) attenuates the external electromagnetic noise from the nT (nanotesla) level to the pT (pico tesla) level, and in the industrial electromagnetic environment (such as near 10kV high-voltage equipment), the relative error of the detection result is <2%.

[0099] Low-temperature stability: The material low-temperature compatibility design and thermal noise suppression measures make the detection sensitivity of the detection device 100 fluctuate <1% when it works continuously at 4.2K low temperature.

[0100] High radiation tolerance: Nb-Ti alloy superconducting coil (critical magnetic field > 15T) and boron nitride insulation layer are selected, combined with radiation hardening process, after the gamma ray irradiation dose reaches 10 6 Gy, the performance attenuation of the detection device 100 is less than 5% (the performance attenuation of traditional semiconductor detectors is more than 50% under the same dose); the surface of the neutron conversion mechanism 10 is modified by ion implantation (such as implanting carbon ions, dose 10 15 ions / cm²) through the radiation hardening process, which enhances the lattice stability of the material and reduces the structural damage caused by radiation.

[0101] Redundant backup function: the multiple transmission channels of the magnetic flux concentrator 33 are parallel, so that the detection device 100 can automatically switch to the standby channel after one channel fails due to radiation, and the detection capability remains more than 90%, ensuring long-term operation reliability.

[0102] Four, solve the problem of low temperature and thermal noise interference

[0103] SQUID needs to work in a low temperature environment (such as liquid helium temperature zone 4.2K) to maintain superconducting properties, but the low temperature environment can easily cause problems such as uneven thermal shrinkage of materials and thermal noise interference in traditional detector structures. The detection device 100 solves this problem from two aspects of material selection and structure design.

[0104] (1) Material low temperature compatibility design: materials with similar thermal expansion coefficients are selected, such as Nb material (thermal expansion coefficient α ≈ 7.2 × 10 -6 / K) for the superconducting induction coil 31, and titanium alloy (α ≈ 8.9 × 10 -6 / K) for the support structure for supporting the superconducting induction coil 31, to reduce internal stress caused by temperature changes.

[0105] (2) Thermal noise suppression: by optimizing SQUID operating parameters (such as bias current control at 1-10μA, modulation frequency set at 100-500kHz), it works in the lowest thermal noise frequency band; at the same time, low noise preamplifier 71 (noise voltage < 1 ) is used to further reduce the influence of circuit noise on the signal.

[0106] (3) Background radiation noise suppression: by material purification process (such as reducing the content of radioactive impurities such as uranium and thorium to <1ppb) to reduce the background radioactivity of the structure components, combined with pulse shape discrimination algorithm (based on the pulse width and amplitude difference between neutron signal and background signal), effective filtering of background noise is realized, and the noise suppression ratio is improved to more than 1000:1.

[0107] Five, wide application scenarios

[0108] Nuclear physics research: high sensitivity and energy resolution make it suitable for high-precision experiments such as neutron scattering spectroscopy analysis and nuclear reaction cross-section measurement.

[0109] Nuclear facility safety: low-flux detection capability meets the safety needs of nuclear reactor core leakage early warning, spent fuel storage monitoring, etc.

[0110] Medical field: in neutron radiotherapy, real-time monitoring of neutron dose in tumor area can be realized, with a dose measurement error of <2%, providing technical support for improving radiotherapy accuracy.

[0111] Deep space exploration: the anti-radiation and low-power (detection device 100 power <10W) characteristics make it applicable to spacecraft neutron radiation environment monitoring.

[0112] The detection device 100 of the present application has the following advantages.

[0113] (1) Performance advantage is outstanding: in terms of detection sensitivity, energy resolution, anti-interference ability and other core indicators, it fully surpasses traditional neutron detectors, filling the technical gap in low-flux, high-precision neutron detection.

[0114] (2) Strong technical innovation: the superconducting quantum interference technology is deeply integrated with neutron conversion and magnetic flux coupling technology to build a new neutron detection technology path, which is innovative.

[0115] (3) Good environmental adaptability: through multi-level shielding, radiation-resistant material selection, redundancy design and other means, it can adapt to complex environments such as electromagnetic interference, strong radiation and low temperature, and is widely applicable.

[0116] (4) Strong scalability: the detection device 100 adopts modular design, which can add or reduce detection channels (such as expanding to 8 channels) or replace different types of conversion layers (such as Li, B) to adapt to different neutron energy ranges, with high flexibility. 6 Li, 10 B) to adapt to different neutron energy ranges, with high flexibility.

[0117] The present application also proposes a particle accelerator (not shown in the figure), which includes the above-mentioned superconducting quantum interference device-based neutron radiation detection device 100 (hereinafter referred to as detection device 100), and the specific structure of the detection device 100 is referred to the above-mentioned embodiments. Since the particle accelerator adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. Among them, the detection device 100 is located at the downstream position of the acceleration structure of the particle accelerator, so as to receive the particle beam mixed with a large amount of neutrons.

[0118] In the present application, if the terms "inner", "outer", "upper", "lower" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0119] In the present application, unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "fixation", "connection" appear, they should be understood broadly, for example, "connection" can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0120] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made according to the concept of the present application, using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A neutron radiation detection device based on a superconducting quantum interference device, characterized in that, The device comprises a neutron conversion mechanism, a magnetic flux coupling mechanism, a superconducting quantum interference device, and a signal processing mechanism, the magnetic flux coupling mechanism comprises a superconducting induction coil and a magnetic flux concentrator arranged adjacent to each other along the neutron transmission direction, the neutron conversion mechanism is located at one end of the superconducting induction coil away from the magnetic flux concentrator, the neutron conversion mechanism comprises an incident layer and an exit layer, the incident layer is a planar thin film structure with a thickness of 5-10 μm, one end of the exit layer away from the incident layer is provided with a lead-out structure, the lead-out structure is arranged adjacent to the superconducting induction coil, the lead-out structure is an array of multiple V-shaped grooves, the groove depth of the V-shaped groove is 100-200 μm, the groove spacing of adjacent two V-shaped grooves is 50-100 μm, the angle of the V-shaped groove is set to an angle α and satisfies 60°≤α≤90°, the superconducting quantum interference device is arranged at one end of the magnetic flux concentrator away from the superconducting induction coil, and the signal processing mechanism is electrically connected with the superconducting quantum interference device.

2. The superconducting quantum interference device-based neutron radiation detection apparatus of claim 1, wherein, The surface of the exit layer facing the superconducting induction coil is a carbon ion implantation modified surface.

3. The superconducting quantum interference device-based neutron radiation detection apparatus of claim 1, wherein, One end of the superconducting induction coil is adjacent to the neutron conversion mechanism and is spaced apart at a first spacing, and the first spacing is 1-2 mm.

4. The superconducting quantum interference device-based neutron radiation detection apparatus of claim 1, wherein, The superconducting induction coil is coaxially installed with the magnetic flux concentrator, the magnetic flux concentrator is arranged with a variable diameter along the length direction, the input end is the large diameter end, and the output end is the small diameter end, and the large diameter end is arranged adjacent to the superconducting induction coil.

5. The superconducting quantum interference device-based neutron radiation detection apparatus of claim 1, wherein, The superconducting quantum interference device is packaged in a shielding member, the superconducting quantum interference device is provided with a sensitive area adjacent to one end of the magnetic flux concentrator, the shielding member is provided with a through opening corresponding to the sensitive area, and the shielding member is a low-temperature dewar or a superconducting shielding cylinder; and / or, the magnetic flux concentrator is provided with multiple transmission channels, and the multiple transmission channels are arrayed and all penetrate through both ends of the magnetic flux concentrator in the length direction.

6. The superconducting quantum interference device-based neutron radiation detection apparatus of any one of claims 1 to 5, wherein, The signal processing mechanism comprises a low-noise preamplifier, a data acquisition device, and a data analyzer, and the data acquisition device is signal-connected with the superconducting quantum interference device.

7. The superconducting quantum interference device-based neutron radiation detection apparatus of any one of claims 1 to 5, wherein, The neutron radiation detection device further comprises a packaging shell provided with a packaging cavity, and the packaging shell is provided with a support structure corresponding to the neutron conversion mechanism, the magnetic flux coupling mechanism, and the superconducting quantum interference device; and the neutron conversion mechanism, the magnetic flux coupling mechanism, and the superconducting quantum interference device are detachably arranged in the packaging cavity through the corresponding support structures.

8. A particle accelerator characterized by, The device comprises a neutron conversion mechanism, a magnetic flux coupling mechanism, a superconducting quantum interference device, and a signal processing mechanism, the magnetic flux coupling mechanism comprises a superconducting induction coil and a magnetic flux concentrator arranged adjacent to each other along the neutron transmission direction, the neutron conversion mechanism is located at one end of the superconducting induction coil away from the magnetic flux concentrator, the neutron conversion mechanism comprises an incident layer and an exit layer, the incident layer is a planar thin film structure with a thickness of 5-10 μm, one end of the exit layer away from the incident layer is provided with a lead-out structure, the lead-out structure is arranged adjacent to the superconducting induction coil, the lead-out structure is an array of multiple V-shaped grooves, the groove depth of the V-shaped groove is 100-200 μm, the groove spacing of adjacent two V-shaped grooves is 50-100 μm, the angle of the V-shaped groove is set to an angle α and satisfies 60°≤α≤90°, the superconducting quantum interference device is arranged at one end of the magnetic flux concentrator away from the superconducting induction coil, and the signal processing mechanism is electrically connected with the superconducting quantum interference device.

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