Fast neutron imaging detector based on chlorine-containing halide scintillation screen and imaging method

Abstract

The invention discloses a fast neutron imaging detector and imaging method based on a chlorine-containing halide scintillation screen, and the detector comprises a fast neutron scintillator conversion screen, a light path system which is used for collecting and reflecting scintillation fluorescence emitted by the fast neutron scintillator conversion screen, and a detection imaging system. An imaging object is located in front of the fast neutron scintillator conversion screen, the light path system is located behind the fast neutron scintillator conversion screen, and the detection imaging system is located on the side of the light path system. The fast neutron scintillator conversion screen comprises chlorine-containing copper-based halide perovskite Cs5Cu3Cl8-xIx, and the fast neutron scintillator conversion screen is used for detecting fast neutrons based on a 35Cl (n, p) nuclear reaction. Compared with a nuclear recoil method, the 35Cl (n, p) nuclear reaction has the advantages that the average energy of secondary protons generated by fast neutrons with the same incident energy is small, the monochromaticity is better, fluorescence diffusion distribution is smaller, and therefore better imaging spatial resolution is obtained.

Description

Technical Field

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

[0002] Fast neutrons have strong penetrating power for most substances, so fast neutron imaging is a potential technical means in the field of X-ray nondestructive testing of large-sized components. The fast neutron scintillator is an important component of the fast neutron imaging system, which effectively converts the fast neutron incident signal into a visible light output signal.

[0003] Commercially used fast neutron imaging screen materials include plastic scintillators (NE102 or EJ200) and polypropylene (PP) / ZnS-type commercial scintillators (ZnS (Ag): PP and ZnS (Cu): PP), which have high hydrogen density, thus promoting a relatively high interaction cross section between protons and fast neutrons. It is worth noting that the principles of fast neutron imaging using the above scintillators are all based on the nuclear recoil method, where fast neutrons interact with hydrogen in the scintillator through elastic scattering to produce recoil protons, which 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 produced by the reaction is large and the distribution is dispersed, resulting in a 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 scintillator screen with a simple structure and small fast neutron fluorescence diffusion distribution, and provides a fast neutron imaging method based on a chlorine-containing halide scintillator screen.

[0005] The technical solution of the present invention to solve the above technical problems is: a fast neutron imaging detector based on a chlorine-containing halide scintillator screen, comprising a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system and a detection imaging system for collecting and reflecting the scintillation fluorescence emitted by the fast neutron scintillator conversion screen, wherein 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 comprises a chlorine-containing copper-based halide perovskite Cs 5 Cu 3 Cl 8-x I x , 1≤ x≤2.

[0006] The fast neutron imaging detector based on the chlorine-containing halide scintillation screen has a circular surface shape, a diameter of 1 to 10 cm, and a thickness of 1 to 5 mm.

[0007] The fast neutron imaging detector based on the chlorine-containing halide scintillation screen has a surface shape of a square with a side length of 1 to 10 cm and a thickness of 1 to 5 mm.

[0008] The fast neutron imaging detector based on the chlorine-containing halide scintillator screen is manufactured by: 5 Cu 3 Cl 8-x I x The stoichiometric ratio of CsCl, CuCl and CsI is uniformly mixed, and then the mixture is vacuum sealed and sintered at high temperature to obtain Cs 5 Cu 3 Cl 8-x I x The powder is finally formed into tablets using a tablet press.

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

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

[0011] In the fast neutron imaging detector based on the chlorine-containing halide scintillation screen, the image intensifier is a microchannel plate, a low-light 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 the chlorine-containing halide scintillation screen is placed in a dark room to avoid interference from ambient light.

[0013] A fast neutron imaging method based on a chlorine-containing halide scintillation screen comprises the following steps: Step 1: inject the 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; Step 2: Fast neutron scintillator conversion screen is based on 35 Cl (n, p) nuclear reaction to absorb fast neutrons and convert them into scintillation fluorescence for emission; Step 3: The optical path system deflects the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and sends it to the detection imaging system; Step 4: The detection imaging system converts the received light signal into an electrical signal, which is finally output as an image signal.

[0014] The beneficial effects of the present invention are: 1. The fast neutron imaging detector of the present invention comprises a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence, wherein the fast neutron scintillator conversion screen comprises a chlorine-containing copper-based halide perovskite Cs 5 Cu 3 Cl 8-x I x The fast neutron scintillator conversion screen is based on 35 Cl (n, p) nuclear reaction to detect fast neutrons. Compared with the nuclear recoil method, 35 The secondary protons produced by the Cl (n, p) nuclear reaction for fast neutrons of the same incident energy have a smaller average energy and better monochromaticity, which makes the fluorescence diffusion distribution smaller, thus obtaining better imaging spatial resolution.

[0015] 2. The fast neutron scintillator conversion screen of the present invention works 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. The free excitons then relax into self-confined excitons through lattice distortion. They have a large Stokes shift and high light yield, which effectively improves the detection efficiency of the scintillator screen.

[0016] 3. In the fast neutron imaging detector of the present invention, the manufacturing process of the fast neutron scintillator conversion screen is as follows: 5 Cu 3 Cl 8-x I x The stoichiometric ratio of CsCl, CuCl and CsI is uniformly mixed, and then the mixture is vacuum sealed and sintered at high temperature to obtain Cs 5 Cu 3 Cl 8-x I x The powder is finally formed into sheets by a tablet press. According to the application scenario and environment, fast neutron scintillator conversion screens of different sizes, thicknesses and shapes can be prepared. Fast neutron imaging of different energies can be achieved by selecting fast neutron scintillator conversion screens of different thicknesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the fast neutron imaging detector of the present invention.

[0018] Figure 2 Schematic diagram of the crystal structure of chloride-containing copper-based halide perovskite.

[0019] Figure 3X-ray diffraction pattern of chlorine-containing copper-based halide perovskite powder.

[0020] Figure 4 This is the photoluminescence spectrum of the fast neutron scintillator conversion screen.

[0021] Figure 5 This is a test chart of the fluorescence quantum efficiency of the fast neutron scintillator conversion screen.

[0022] Figure 6 This is a comparison of photos of the fast neutron scintillator conversion screen under natural light and ultraviolet light.

[0023] Figure 7 This is a graph showing the irradiation and environmental stability test results of the fast neutron scintillator conversion screen.

[0024] Figure 8 This is the fast neutron energy spectrum of the fast neutron scintillator conversion screen.

[0025] Fig. 9 This is a diagram of the spatial resolution of the fast neutron scintillator conversion screen.

[0026] Fig.10 Schematic diagram of the fast neutron imaging photo of the fast neutron imaging detector. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, a fast neutron imaging detector based on a chlorine-containing halide scintillator screen includes a fast neutron scintillator conversion screen 1 for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system and a detection imaging system for collecting and reflecting scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1, an 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 dark room 3 to avoid interference from ambient light.

[0029] Fast neutron scintillator conversion screen 1 includes chlorine-containing copper-based halide perovskite Cs 5 Cu 3 Cl 8-x I x , 1≤ x≤2. The surface shape of the fast neutron scintillator conversion screen 1 is circular or square, with a thickness of 1~5 mm. If it is circular, the diameter is 1~10 cm, and if it is square, the side length is 1~10 cm.

[0030] The manufacturing process of the fast neutron scintillator conversion screen 1 is as follows: 5 Cu 3 Cl 8-x Ix The stoichiometric ratio of CsCl, CuCl and CsI is uniformly mixed, and then the mixture is vacuum sealed and sintered at high temperature to obtain Cs 5 Cu 3 Cl 8-x I x The powder is finally formed into tablets using a tablet press.

[0031] The optical path system is an optical reflector 4, which forms an angle of 45° with the fast neutron scintillator conversion screen 1 and the detection imaging system, and is used to convert the scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1 and perform optical path deflection.

[0032] The detection imaging system includes an image intensifier 5 and an imaging camera 6, which are located on the same straight line, and the scintillation fluorescence reflected by the optical reflector 4 is sent to the imaging camera 6 after passing through the image intensifier 5. The image intensifier 5 is a microchannel plate, a low-light camera tube or an optical amplifier, and the imaging camera 6 is a CCD camera or an sCMOS camera.

[0033] A fast neutron imaging method based on a chlorine-containing halide scintillation screen is conducted by conducting 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: Step 1: inject a fast neutron beam from the front of the imaging object 2, and the fast neutron beam hits the fast neutron scintillator conversion screen 1 after passing through the imaging object 2; Step 2: Fast neutron scintillator conversion screen 1 is based on 35 Cl (n, p) nuclear reaction to absorb fast neutrons and convert them into scintillation fluorescence 7 for emission; Step 3: The optical path system deflects the scintillation fluorescence 7 emitted by the fast neutron scintillator conversion screen 1 and sends it to the detection imaging system; Step 4: The detection imaging system converts the received light signal into an electrical signal, which is finally output as an image signal.

[0034] like Figure 2 As shown, Cs 5 Cu 3 Cl 6 I 2 The structure consists of a one-dimensional (1D) chain [Cu 3 Cl 6 I 2 ] n 5n- Through the cation (Cs + ) are interconnected, where [Cu 3 Cl 6 I 2 ] n 5n-The one-dimensional zigzag chain consists of alternating [CuCl 2 I 2 ] 2 Unit and single [CuCl 2 I 2 ] units, and iodide ions serve as bridging species to connect these structural units.

[0035] Figure 3 is the X-ray diffraction pattern of chlorine-containing copper-based halide perovskite powder. Figure 3 In, Cs 5 Cu 3 Cl 6 I 2 The powder X-ray diffraction (XRD) pattern of the crystal is highly consistent with the simulation results, confirming the good crystal quality of the crystal.

[0036] Figure 4 This is the photoluminescence spectrum of the fast neutron scintillator conversion screen. Figure 4 The broad emission spectrum and Stokes shift shown indicate the nature of the self-confined exciton emission, where the maximum Stokes shift reaches 1.47 eV, indicating that the scintillator screen has low self-absorption and good potential for high light yield.

[0037] Figure 5 This is a test diagram of the fluorescence quantum efficiency of the fast neutron scintillator conversion screen. Figure 5 It can be seen that at room temperature, the photoluminescence quantum yield (PLQY) of the fast neutron scintillator conversion screen reaches 51.13%.

[0038] Figure 6 This is a comparison of the fast neutron scintillator conversion screen under natural light and ultraviolet light. Figure 6 In the figure, 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.

[0039] The stability of the invention in a humid and irradiated environment is a key consideration for its commercial application. The invention has conducted stability tests on the fast neutron scintillator conversion screen in a humid and hot environment (temperature 25°C, humidity 45%) and a strong irradiation environment. Figure 7 As shown, no obvious quality change was observed during the 15-day exposure experiment; in addition, the material can still maintain basically unchanged luminescence intensity when the cumulative absorbed X-ray dose reaches 764 Gy.

[0040] Figure 8 The luminescence characteristics of fast neutron scintillator conversion screens under fast neutron irradiation were studied on a tandem accelerator. Figure 8 As shown in Figure 3, in the pulse amplitude spectra corresponding to 4 MeV and 6 MeV fast neutrons, the number of channels corresponding to the signal front edge of 6 MeV neutrons is higher than that of 4 MeV neutrons.

[0041] Fig. 9 This is a diagram of the spatial resolution of the fast neutron scintillator conversion screen. Fig. 9 In the experiment, the modulation transfer function (MTF=0.1) was measured by the slant edge method, and the spatial resolution of neutron imaging of the fast neutron scintillator conversion screen reached 1.31 lp / mm, which successfully surpassed the commercial plastic scintillator EJ200 (0.35 lp / mm) and PP / ZnS:Ag (0.50 lp / mm), and was better than the organic-inorganic hybrid perovskite (OIHPs) fast neutron scintillator, such as BA 2 PbB 4 (1.00 lp / mm) and Mn-STA 2 PbB 4 (0.50 lp / mm).

[0042] Fig.10 The application of fast neutron scintillator conversion screen in high-resolution fast neutron imaging was further demonstrated. Fig.10 The cross-sectional imaging shows a hollow polytetrafluoroethylene cylinder with an N-shaped structure and its fast neutron imaging results on a scintillation screen. The clear N-shaped logo and the outline of the cylinder indicate that the 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 scintillator screen, characterized in that: The invention comprises a fast neutron scintillator conversion screen for absorbing fast neutrons and converting them into scintillation fluorescence, an optical path system and a detection imaging system for collecting and reflecting the scintillation fluorescence emitted by the fast neutron scintillator conversion screen, wherein 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 comprises a chlorine-containing copper-based halide perovskite Cs5Cu3Cl 8-x I x , 1≤ x≤2.

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

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

4. The fast neutron imaging detector based on 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: 8-x I x The stoichiometric ratio of CsCl, CuCl and CsI is uniformly mixed, and then the mixture is vacuum sealed and sintered at high temperature to obtain Cs5Cu3Cl 8-x I x The powder is finally formed into tablets using a tablet press.

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

6. The fast neutron imaging detector based on chlorine-containing halide scintillation screen according to claim 5, characterized in that: The detection imaging system comprises an image intensifier and an imaging camera. The image intensifier and the imaging camera are located on the same straight line. The flashing fluorescence reflected by the optical reflector is sent to the imaging camera after passing through the image intensifier.

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

8. The fast neutron imaging detector based on chlorine-containing halide scintillation screen according to claim 1, characterized in that: The entire fast neutron imaging detector is placed in a dark room to avoid interference from ambient light.

9. A fast neutron imaging method based on a chlorine-containing halide scintillator screen, which is implemented by using a fast neutron imaging detector based on a chlorine-containing halide scintillator screen as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: inject the 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; Step 2: Fast neutron scintillator conversion screen is based on 35 Cl (n, p) nuclear reaction to absorb fast neutrons and convert them into scintillation fluorescence for emission; Step 3: The optical path system deflects the scintillation fluorescence emitted by the fast neutron scintillator conversion screen and sends it to the detection imaging system; Step 4: The detection imaging system converts the received light signal into an electrical signal, which is finally output as an image signal.

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