Fast Neutron Imaging Detector and Imaging Method Based on Chlorine-Containing Halide Scintillation Screen

Abstract

The present invention discloses a fast neutron imaging detector and an imaging method based on a chlorine-containing halide scintillation screen. The fast neutron imaging detector includes a fast neutron scintillator conversion screen, an optical path system for collecting and reflecting the scintillation fluorescence emitted by the fast neutron scintillator conversion screen, and a detection imaging system. The imaging object is located in front of the fast neutron scintillator conversion screen, the optical path system is located behind the fast neutron scintillator conversion screen, and the detection imaging system is located on the side of the optical path system. The fast neutron scintillator conversion screen of the present invention comprises a chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8‑x I x , and the fast neutron scintillator conversion screen is based on 35 the Cl(n,p) nuclear reaction to detect fast neutrons. Compared with the nuclear recoil method, 35 the Cl(n,p) nuclear reaction generates secondary protons with a smaller average energy and better monochromaticity for fast neutrons with the same incident energy, resulting in a smaller fluorescence diffusion distribution, and thus a better imaging spatial resolution is obtained.

Description

Technical Field

[0001] The present invention relates to the field of fast neutron imaging, and particularly to a fast neutron imaging detector and an imaging method based on a chlorine-containing halide scintillation screen. Background Art

[0002] Fast neutrons have a strong penetration ability for most substances. Therefore, fast neutron imaging is a potential technical means in the field of non-destructive testing of large-sized components by rays. A fast neutron scintillation screen is an important part of a fast neutron imaging system, which effectively converts the incident signal of fast neutrons into a visible light output signal.

[0003] Commercially used fast neutron imaging screen materials include plastic scintillators (NE102 or EJ200) and polypropylene (PP) / ZnS-based commercial scintillators (ZnS(Ag):PP and ZnS(Cu):PP). They have a high hydrogen density, thus promoting a relatively high interaction cross-section between protons and fast neutrons. It should be noted that the principles of fast neutron imaging using the above-mentioned scintillators are all based on the nuclear recoil method. Fast neutrons interact with hydrogen in the scintillator through elastic scattering to generate recoil protons, and deposit energy through ionization and excitation. However, the nuclear recoil method based on hydrogen atoms has its inherent limitations. Specifically, the average energy of the recoil protons generated by the reaction is relatively large and the distribution is relatively dispersed, resulting in a relatively wide overall energy diffusion area or point spread function (PSF), which has an adverse effect on the spatial resolution of imaging. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a fast neutron imaging detector based on a chlorine-containing halide scintillation screen with a simple structure and a small fast neutron fluorescence diffusion distribution, and provides a fast neutron imaging method based on a chlorine-containing halide scintillation screen.

[0005] The technical solution of the present invention for solving the above technical problems is: a fast neutron imaging detector based on a chlorine-containing halide scintillation screen, including a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system for collecting and reflecting the scintillation fluorescence emitted by the fast neutron scintillator conversion screen, and a detection imaging system. The imaging object is located in front of the fast neutron scintillator conversion screen, the optical path system is located behind the fast neutron scintillator conversion screen, and the detection imaging system is located on the side of the optical path system; the fast neutron scintillator conversion screen includes chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8-x I x , 1 ≤ x ≤ 2.

[0006] For the above fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the surface shape of the fast neutron scintillator conversion screen is circular, with a diameter of 1 - 10 cm and a thickness of 1 - 5 mm.

[0007] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, wherein the surface shape of the fast neutron scintillator conversion screen is square, with a side length of 1-10 cm and a thickness of 1-5 mm.

[0008] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the manufacturing process of the fast neutron scintillator conversion screen is as follows: According to the stoichiometric ratio of Cs5Cu3Cl 8-x I x mix CsCl, CuCl and CsI evenly, then vacuum-seal the mixture and perform high-temperature sintering to obtain Cs5Cu3Cl 8-x I x powder, and finally use a tablet press to form a sheet.

[0009] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the optical path system is an optical mirror, and the optical mirror forms a 45° angle with the fast neutron scintillator conversion screen and the detection imaging system, and is used for the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and for optical path turning.

[0010] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the detection imaging system includes an image intensifier and an imaging camera, the image intensifier and the imaging camera are on the same straight line, and the scintillation fluorescence reflected by the optical mirror is sent into the imaging camera after passing through the image intensifier.

[0011] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the image intensifier is a microchannel plate, a low-light-level camera tube or an optical amplifier, and the imaging camera is a CCD camera or an sCMOS camera.

[0012] The above-mentioned fast neutron imaging detector based on a chlorine-containing halide scintillation screen, the entire fast neutron imaging detector is placed in a dark room to avoid environmental light interference.

[0013] A fast neutron imaging method based on a chlorine-containing halide scintillation screen, comprising the following steps:

[0014] Step 1: Shoot a fast neutron beam from the front of the imaging object, and the fast neutron beam hits the fast neutron scintillator conversion screen after passing through the imaging object;

[0015] Step 2: The fast neutron scintillator conversion screen absorbs fast neutrons based on 35 the Cl (n, p) nuclear reaction, and converts the fast neutrons into scintillation fluorescence and emits it;

[0016] Step 3: The optical path system turns the optical path of the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and shoots it towards the detection imaging system;

[0017] Step 4: The detection imaging system converts the received optical signal into an electrical signal and finally outputs it as an image signal.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The fast neutron imaging detector of the present invention includes a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence. The fast neutron scintillator conversion screen includes a chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8-x I x , and the fast neutron scintillator conversion screen is based on 35 the Cl (n, p) nuclear reaction to detect fast neutrons. Compared with the nuclear recoil method, 35 the Cl (n, p) nuclear reaction produces secondary protons with a smaller average energy and better monochromaticity for fast neutrons with the same incident energy, resulting in a smaller fluorescence diffusion distribution, and thus better imaging spatial resolution is obtained.

[0020] 2. The fast neutron scintillator conversion screen of the present invention operates based on the principle of self-confined exciton luminescence. High-energy particles generate secondary electrons, which lose energy through phonon scattering (thermalization). After reaching the edge of the conduction band, these secondary electrons combine with holes through Coulomb interaction to form free excitons, and the free excitons then relax into self-confined excitons through lattice distortion, having a large Stokes shift and high light yield, effectively improving the detection efficiency of the scintillation screen.

[0021] 3. In the fast neutron imaging detector of the present invention, the manufacturing process of the fast neutron scintillator conversion screen is as follows: According to the stoichiometric ratio of Cs5Cu3Cl 8-x I x , CsCl, CuCl, and CsI are mixed evenly, and then the mixture is vacuum-sealed and sintered at high temperature to obtain Cs5Cu3Cl 8-x I x powder. Finally, a tablet press is used for tablet forming, and fast neutron scintillator conversion screens with different sizes, thicknesses, and shapes can be prepared according to the application scenarios and environments. Different energy fast neutron imaging can be achieved by selecting fast neutron scintillator conversion screens with different thicknesses. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the fast neutron imaging detector of the present invention.

[0023] Figure 2 is a schematic crystal structure diagram of the chlorine-containing copper-based halide perovskite.

[0024] Figure 3 is an X-ray diffraction pattern of the chlorine-containing copper-based halide perovskite powder.

[0025] Figure 4 is a photoluminescence spectrum diagram of the fast neutron scintillator conversion screen.

[0026] Figure 5 It is a test chart of the fluorescence quantum efficiency of the fast neutron scintillator conversion screen.

[0027] Figure 6 It is a comparison chart of photos of the fast neutron scintillator conversion screen under natural light and ultraviolet light.

[0028] Figure 7 It is a test result chart of the irradiation and environmental stability of the fast neutron scintillator conversion screen.

[0029] Figure 8 It is the fast neutron energy spectrum chart of the fast neutron scintillator conversion screen.

[0030] Figure 9 It is the spatial resolution chart of the fast neutron scintillator conversion screen.

[0031] Figure 10 It is a schematic diagram of the fast neutron imaging photo of the fast neutron imaging detector. Specific implementation manners

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] As Figure 1 shown, a fast neutron imaging detector based on a chlorine-containing halide scintillation screen includes a fast neutron scintillator conversion screen 1 for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system for collecting and reflecting the scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1, and a detection imaging system. The imaging object 2 is located in front of the fast neutron scintillator conversion screen 1, the optical path system is located behind the fast neutron scintillator conversion screen 1, and the detection imaging system is located on the side of the optical path system. The entire fast neutron imaging detector is placed in a darkroom 3 to avoid environmental light interference.

[0034] The fast neutron scintillator conversion screen 1 includes chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8-x I x , where 1 ≤ x ≤ 2. The surface shape of the fast neutron scintillator conversion screen 1 is circular or square, and the thickness is 1 - 5 mm. When it is circular, the diameter is 1 - 10 cm, and when it is square, the side length is 1 - 10 cm.

[0035] The manufacturing process of the fast neutron scintillator conversion screen 1 is as follows: According to the stoichiometric ratio of Cs5Cu3Cl 8-x I x , CsCl, CuCl, and CsI are mixed evenly, and then the mixture is vacuum-sealed and sintered at high temperature to obtain Cs5Cu3Cl 8-x I x powder, and finally a tablet is formed using a tablet press.

[0036] The optical path system is an optical mirror 4, which forms a 45° angle between the fast neutron scintillator conversion screen 1 and the detection imaging system, and is used to reflect the scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1 and make an optical path turn.

[0037] The detection imaging system includes an image intensifier 5 and an imaging camera 6. The image intensifier 5 and the imaging camera 6 are located on the same straight line. The scintillation fluorescence reflected by the optical mirror 4 is sent into the imaging camera 6 after passing through the image intensifier 5. The image intensifier 5 is a microchannel plate, an image orthicon or an optical amplifier, and the imaging camera 6 is a CCD camera or an sCMOS camera.

[0038] A fast neutron imaging method based on a chlorine-containing halide scintillation screen, which conducts fast neutron imaging research based on a fast neutron imaging detector on an accelerator neutron source or a reactor neutron source. The method includes the following steps:

[0039] Step 1: Shoot a fast neutron beam from the front of the imaging object 2. After passing through the imaging object 2, the fast neutron beam hits the fast neutron scintillator conversion screen 1.

[0040] Step 2: The fast neutron scintillator conversion screen 1 35 absorbs fast neutrons based on the Cl (n, p) nuclear reaction and converts the fast neutrons into scintillation fluorescence 7 and emits it.

[0041] Step 3: The optical path system makes an optical path turn for the scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1 and shoots it towards the detection imaging system.

[0042] Step 4: The detection imaging system converts the received optical signal into an electrical signal and finally outputs it as an image signal.

[0043] As Figure 2 shown, the structure of Cs5Cu3Cl6I2 consists of one-dimensional (1D) chain-like [Cu3Cl6I2] n 5n- connected to each other by cations (Cs + ). Among them, the one-dimensional zigzag chain of [Cu3Cl6I2] n 5n- is composed of alternately arranged [CuCl2I2]2 units and single [CuCl2I2] units, and iodide ions are used as bridging species to connect these structural units.

[0044] Figure 3 is the X-ray diffraction pattern of the chlorine-containing copper-based halide perovskite powder. Figure 3 Among them, the powder X-ray diffraction (XRD) pattern of Cs5Cu3Cl6I2 is in good agreement with the simulation results, confirming the good crystalline quality of the crystal.

[0045] Figure 4It is the photoluminescence spectrum diagram of the fast neutron scintillator conversion screen. It can be seen from Figure 4 the wide emission spectrum and Stokes shift shown that the nature of self-confined exciton emission, where the maximum Stokes shift reaches 1.47 eV, indicating that the scintillation screen has small self-absorption and good potential for high light yield.

[0046] Figure 5 It is the fluorescence quantum efficiency test diagram of the fast neutron scintillator conversion screen. According to Figure 5 it can be known that at room temperature, the photoluminescence quantum yield (PLQY) of the fast neutron scintillator conversion screen reaches 51.13%.

[0047] Figure 6 It is the photo comparison diagram of the fast neutron scintillator conversion screen under natural light and ultraviolet light. Figure 6 In it, a square fast neutron scintillator conversion screen with a side length of 5 cm and a thickness of 2 mm emits uniform cyan light under the excitation of 290 nm ultraviolet light.

[0048] The stability of the present invention in humid and irradiated environments is a key consideration for its commercial application. The present invention has carried out stability tests on the fast neutron scintillator conversion screen under humid and hot environments (temperature 25 °C, humidity 45%) and strong irradiation environments. As Figure 7 shown, no obvious quality change was observed during the 15-day exposure experiment; in addition, the material can still maintain the luminous intensity basically unchanged when the cumulative absorbed X-ray dose reaches 764 Gy.

[0049] Figure 8 The luminescence characteristics of the fast neutron scintillator conversion screen under fast neutron irradiation were studied on a tandem accelerator. As Figure 8 shown, in the pulse amplitude spectra corresponding to 4 MeV and 6 MeV fast neutrons, the channel number corresponding to the signal front of 6 MeV neutrons is higher than that of 4 MeV neutrons.

[0050] Figure 9 It is the spatial resolution diagram of the fast neutron scintillator conversion screen. Figure 9 In it, by measuring the modulation transfer function (MTF = 0.1) through the bevel method, the neutron imaging spatial resolution of the fast neutron scintillator conversion screen reaches 1.31 lp / mm, and its value successfully exceeds that of commercial plastic scintillators EJ200 (0.35 lp / mm) and PP / ZnS:Ag (0.50 lp / mm), and is better than organic-inorganic hybrid perovskite (OIHPs) fast neutron scintillators, such as BA2PbBr4 (1.00 lp / mm) and Mn-STA2PbBr4 (0.50 lp / mm).

[0051] Figure 10 It further demonstrates the application of the fast neutron scintillator conversion screen in high-resolution fast neutron imaging.Figure 10 The cross-sectional imaging shows a polytetrafluoroethylene hollow cylinder with an N-shaped structure and its fast neutron imaging results on the scintillation screen. The clear N-shaped mark and the cylinder contour indicate that this material has significant application potential in the field of low-Z material radiography.

Claims

1. A fast neutron imaging detector based on a chlorine-containing halide scintillation screen, characterized in that, It includes a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system for collecting and reflecting the scintillation fluorescence emitted by the fast neutron scintillator conversion screen, and a detection imaging system. The imaging object is located in front of the fast neutron scintillator conversion screen, the optical path system is located behind the fast neutron scintillator conversion screen, and the detection imaging system is located on the side of the optical path system; the fast neutron scintillator conversion screen includes chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8-x I x , 1 ≤ x ≤ 2, and Cl in the perovskite is 35 Cl.

2. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 1, wherein The surface shape of the fast neutron scintillator conversion screen is circular, with a diameter of 1 - 10 cm and a thickness of 1 - 5 mm.

3. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 1, characterized in that, The surface shape of the fast neutron scintillator conversion screen is square, with a side length of 1 - 10 cm and a thickness of 1 - 5 mm.

4. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 1, characterized in that, The manufacturing process of the fast neutron scintillator conversion screen is as follows: According to the stoichiometric ratio of Cs5Cu3Cl 8-x I x , CsCl, CuCl and CsI are mixed evenly, and then the mixture is vacuum-sealed and sintered at high temperature to obtain Cs5Cu3Cl 8-x I x powder, and finally tablet forming is carried out using a tablet press.

5. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 1, characterized in that, The optical path system is an optical mirror, which forms a 45° angle with the fast neutron scintillator conversion screen and the detection imaging system, and is used to reflect the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and make an optical path turn.

6. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 5, wherein The detection imaging system includes an image intensifier and an imaging camera. The image intensifier and the imaging camera are on the same straight line, and the scintillation fluorescence reflected by the optical mirror is sent into the imaging camera after passing through the image intensifier.

7. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 6, characterized in that, The image intensifier is a microchannel plate, an image orthicon or an optical amplifier, and the imaging camera is a CCD camera or an sCMOS camera.

8. The fast neutron imaging detector based on a chlorine-containing halide scintillation screen according to claim 1, wherein The entire fast neutron imaging detector is placed in a darkroom to avoid ambient light interference.

9. A fast neutron imaging method based on a chlorine-containing halide scintillation screen is implemented by using the fast neutron imaging detector based on the chlorine-containing halide scintillation screen described in any one of claims 1-8, and is characterized in that It includes the following steps: Step 1: Shoot the fast neutron beam from the front of the imaging object. After passing through the imaging object, the fast neutron beam hits the fast neutron scintillator conversion screen. Step 2: The fast neutron scintillator conversion screen is based on 35 the Cl(n,p) nuclear reaction to absorb fast neutrons and convert them into scintillation fluorescence for emission; Step 3: The optical path system makes an optical path turn for the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and shoots it towards the detection imaging system. Step 4: The detection imaging system converts the received optical signal into an electrical signal and finally outputs it as an image signal.

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