A Cherenkov detection array screen with selectable energy threshold

Abstract

The present invention relates to high-energy radiation imaging technology, and more specifically, to a Cherenkov detector array screen with a selectable energy threshold. This technology addresses the existing shortcomings of the Cherenkov radiator, which suffer from a very limited adjustment range for the energy threshold. The Cherenkov detector array screen comprises a converter array structure and an external package. The converter array structure comprises an array of parallel metal capillaries filled with silica aerogel, with adjacent metal capillaries sealed and opaque. The metal capillaries serve as a cladding for the silica aerogel, improving the efficiency of converting radiation into secondary charged particles. The silica aerogel has a refractive index of 1.01-1.2.

Description

Technical Field

[0001] The present invention relates to high-energy ray imaging technology, and in particular to a Cherenkov detection array screen with a selectable energy threshold. Background Art

[0002] In high-energy-density physics measurements and diagnostics of cosmic high-energy radiation, energy-resolved radiation measurement technology is the development direction for refined diagnostics and an essential requirement for continuously improving our understanding of high-energy radiation physics. In the diagnostics of ultrafast gamma-ray facilities and inertial confinement fusion devices currently under construction, energy-resolved ultrafast radiation imaging is a key tool for diagnosing the evolution of morphological parameters in the radiation region and distinguishing the mechanisms of different physical processes. Simultaneously, the application of effective energy threshold detection technology can reduce interference from low-energy scatter or background radiation, thereby obtaining higher-quality target information. In the diagnostics of cosmic high-energy particle physics, high-energy particles of different energies represent information on different astrophysical evolutions, requiring detection technology with energy discrimination capabilities. Currently, radiation detection technology primarily uses scintillators as radiation converters. While scintillators inherently possess position resolution and ultrafast temporal resolution, they respond to radiation of all energies and are unable to discriminate energy.

[0003] Cherenkov converters combine ultrafast time response (hundreds of picoseconds) with energy threshold characteristics. Materials that can serve as Cherenkov converters include gases, liquids, and solids. Solids are relatively easy to process into arrays, while gases and liquids require more complex encapsulation processes. The energy threshold of the radiation that excites the converter to emit Cherenkov photons is related to the converter's refractive index. A higher refractive index corresponds to a lower energy threshold, while a lower refractive index corresponds to a higher energy threshold. Existing liquids and solids that can serve as Cherenkov converters have a refractive index above 1.2, corresponding to a lower energy threshold. Gases, on the other hand, have a lower refractive index, approaching 1, resulting in a higher energy threshold. While the refractive index can be further increased by varying the gas pressure, this is limited. Furthermore, high-pressure gases are inconvenient to use. Consequently, the energy thresholds corresponding to existing Cherenkov converters have a certain "blind spot," resulting in a very limited adjustment range for the energy threshold. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem in the prior art that the adjustment range of the energy threshold corresponding to the Cherenkov radiator is very limited, and to provide a Cherenkov detection array screen with a selectable energy threshold.

[0005] Inventive concept

[0006] The present invention utilizes the Cherenkov effect, generated by the transport of charged particles and radiation within a material, to convert charged particle and radiation information into visible light information that can be collected and transmitted. According to the Cherenkov effect, if the velocity of a charged particle group in a medium exceeds the speed of light within the medium, Cherenkov radiation is generated. Specifically, only charged particles with an energy threshold exceeding a certain threshold can generate Cherenkov radiation within a material. The energy threshold for generating Cherenkov radiation is related to the material's refractive index. Because high-energy radiation (such as gamma rays and neutrons) interacting with a medium can generate secondary charged particles, high-energy radiation can also be detected using Cherenkov radiation.

[0007] Silica aerogel is an important material for detecting Cherenkov transitions with a refractive index between 1.01 and 1.2, providing a solution for detecting the energy threshold corresponding to this refractive index range. However, simple block or flat aerogel materials lack image and position detection capabilities. Therefore, we combined silica aerogel with a metal capillary array, leveraging the independent light guidance of each metal capillary to establish position resolution. Furthermore, the use of metal cladding improves the efficiency of converting radiation into secondary charged particles, resulting in the development of a Cherenkov radiation detection array with a refractive index between 1.01 and 1.2.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] A Cherenkov detection array screen with a selectable energy threshold is special in that it includes a converter array structure and an external package, wherein the converter array structure is arranged within the external package, the external package is used to protect the converter array structure, and the external package has light holes at the incident end and the output end of the converter array structure; the converter array structure includes an array formed by parallel arranged metal capillaries and silica aerogel filled in the metal capillaries, and an opaque sealing material is provided between adjacent metal capillaries; the refractive index of the silica aerogel is 1.01-1.2; rays or charged particles enter through the incident end of the converter array structure, generate Cherenkov radiation in the converter array structure, and are converted into Cherenkov photons to be emitted from the output end; the metal capillaries serve as a cladding for the silica aerogel, and are used to improve the efficiency of converting rays into secondary charged particles.

[0010] Furthermore, the thickness of the converter array structure is calculated using the following formula:

[0011]

[0012] Where Z is the charge of the charged particles generated in the silica aerogel, θ is the angle between the emission direction of the radiated Cherenkov photons and the movement direction of the charged particles, λ1 and λ2 are the wavelengths of the Cherenkov photons, and N pis the number of Cherenkov photons emitted with a wavelength in the range [λ1,λ2], and a is the linear attenuation coefficient of silica aerogel to photons, in cm -1 , l is the thickness of the converter array structure, that is, the length of the metal capillary.

[0013] Furthermore, the inner diameter of the metal capillary is 0.4-1 mm, the wall thickness is 0.1 mm, and the diameter of the silica aerogel matches the inner diameter of the metal capillary.

[0014] Furthermore, the thickness of the converter array structure is 10-50 mm.

[0015] Furthermore, the thickness of the converter array structure is 30 mm.

[0016] Furthermore, the refractive index of the silica aerogel and the corresponding energy threshold are calculated by the following formulas:

[0017] n=1+kρ

[0018]

[0019] Where n is the refractive index, k is the conversion constant between the density and refractive index of silica aerogel, usually taken as 0.21; ρ is the density of silica aerogel; m e is the rest mass of the charged particle; c is the speed of light in air; E e,th is the energy threshold corresponding to the refractive index.

[0020] Furthermore, it also includes a conversion target arranged at the incident end of the converter array structure, and the distance between the conversion target and the incident end is less than 2 mm.

[0021] Furthermore, the conversion target is made of aluminum, beryllium or cesium iodide, and has a thickness of 2-5 mm.

[0022] Furthermore, the metal capillary is made of stainless steel, and the inner wall of the stainless steel is polished.

[0023] Furthermore, the material of the external package is aluminum, and the external package needs to be blackened and frosted to reduce background stray light;

[0024] The metal capillaries are cured by thermal infrared curing glue.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses silica aerogel as a light guide to prepare a detection array screen with a refractive index between 1.01 and 1.2 and an energy threshold selectable. The energy threshold is high, greater than the MeV level, and the refractive index has a wide adjustment range. Since silica aerogel can only cause charged particles or rays with energies above the energy threshold to excite Cherenkov radiation, the use of silica aerogel can distinguish the energy of incident rays or particles on the array screen.

[0027] 2. The present invention packages silica aerogel into a light-conducting array with pixel functions as an energy threshold Cherenkov detector. Specifically, an array formed by metal capillaries is used as a light-conducting element. The silica aerogel in each metal capillary of the array acts as a light-emitting unit, so that it has spatial position resolution, realizing image detection or position resolution detection with a certain spatial resolution capability, so that the array detection screen has energy resolution, position resolution and ultra-fast time resolution.

[0028] 3. The metal capillary structure of the present invention significantly increases the contact area between the radiation passing through the silica aerogel and the metal. Since the metal material can improve the efficiency of converting the radiation in the silica aerogel into secondary charged particles, the efficiency of converting the radiation into secondary charged particles is further improved by increasing the contact area.

[0029] 4. The Cherenkov radiation array screen provided by the present invention has a short luminous duration and a fast response time capability, reaching the order of hundreds of picoseconds, without a slow component decay time, and the silica aerogel can be used stably and is highly safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic cross-sectional structural diagram of an embodiment of the present invention;

[0031] Figure 2 is a schematic cross-sectional view of a converter array structure according to an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the structure of the metal capillary and silica aerogel in an embodiment of the present invention;

[0033] Figure 4 is a schematic structural diagram of the external package in an embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the working principle of calculating Cherenkov photons using the converter array structure model and detector model in an embodiment of the present invention;

[0035] Figure 6 The curve of the relationship between the light yield normalized to each electron and the incident electron energy is calculated and given in the embodiment of the present invention;

[0036] Figure 7 This is a curve showing the relationship between the light yield normalized to each gamma photon and the energy of the incident gamma ray calculated in an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1-conversion target, 2-external packaging, 3-conversion body array structure, 4-silica aerogel, 5-metal capillary, 6-detector. DETAILED DESCRIPTION

[0039] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0040] The energy threshold of the present invention can be selected by the Cherenkov detection array screen, such as Figure 1 As shown, it includes a converter array structure 3, an external package 2, and a conversion target 1 arranged at the incident end of the converter array structure 3. The converter array structure 3 is arranged in the external package 2. The external package 2 is located at the incident end and the exit end of the converter array structure 3 and has light holes, as shown in FIG. Figure 4 As shown, the external package 2 is used to protect the converter array structure 3. The material of the external package 2 is aluminum, and the external package 2 needs to be blackened and frosted to reduce background stray light.

[0041] After passing through the conversion target 1, the ray or charged particle beam enters from the incident end of the converter array structure 3, excites Cherenkov radiation in the silica aerogel 4, and generates Cherenkov photons that are emitted from the output end. The silica aerogel 4 has an energy threshold characteristic. The energy threshold characteristic means that the ray or charged particle acting on it must be greater than a certain energy to excite Cherenkov radiation. The energy is the energy threshold of the charged particle or ray. The energy threshold is related to the refractive index of the silica aerogel 4, and the refractive index is related to the density. The relationship between the energy threshold and the refractive index and density of the silica aerogel 4 is shown in the following formula:

[0042]

[0043] n=1+kρ

[0044] Where n is the refractive index, k is the conversion constant between the density and refractive index of silica aerogel 4, usually taken as 0.21; ρ is the density of silica aerogel 4; m e is the rest mass of the charged particle; c is the speed of light in air; E e,th is the card threshold.

[0045] By adjusting the ratio of chemical components and the synthesis process, silica aerogels 4 with different densities can be obtained, thereby achieving a refractive index adjustment between 1.01 and 1.2. The present invention manufactures a converter array structure 3 with different energy threshold characteristics based on the silica aerogel 4 with adjustable density, thereby achieving the discrimination and detection of rays of different energies.

[0046] Converter array structure 3 Figure 2 and Figure 3 As shown, the array includes parallel metal capillaries 5 and silica aerogel 4 filled in the metal capillaries 5. The use of the metal capillaries 5 is conducive to improving the conversion efficiency of the radiation in the silica aerogel 4 to generate secondary charged particles. Combined with the spatial resolution caused by the energy deposition and diffusion of the radiation in the array and the light output efficiency of a single metal capillary 5, to achieve a spatial resolution of the entire converter array structure 3 within 1 mm, the inner diameter of the metal capillary 5 is 0.4-1 mm, the tube wall thickness is 0.1 mm, and the thickness of the converter array structure 3, that is, the length of the metal capillary 5, can be optimized according to the following formula:

[0047]

[0048] Where Z is the charge of the charged particles generated in the silica aerogel 4, θ is the angle between the emission direction of the radiated Cherenkov photons and the movement direction of the charged particles, λ1 and λ2 are the wavelengths of the Cherenkov photons, and N p is the number of Cherenkov photons of radiation with a wavelength in the range [λ1,λ2], and a is the linear attenuation coefficient of silica aerogel for photons, in cm -1 , l is the thickness of the converter array structure 3.

[0049] In the above formula, when other parameters remain unchanged, the number of emitted photons N p Depends on -al 1. The linear attenuation coefficient of silica aerogel for photons with a wavelength of 500 nm or more is about 0.3 cm -1 According to the above formula, a thickness of 10-50 mm for the converter array structure 3 has minimal impact on light output efficiency. If the length exceeds 50 mm, the increased length of the silica aerogel 4 leads to increased light absorption, significantly decreasing light output efficiency. Furthermore, the increased thickness of the converter array structure 3 increases the spatial trajectory of the scattering interaction between the incident radiation and the array, resulting in a decrease in spatial resolution. The refractive index of silica aerogel 4 is 1.01-1.2. Based on the above formula and the given photon attenuation coefficient, a 30 mm thickness of the converter array structure 3 generates a high number of Cherenkov photons, resulting in a high light output efficiency. The silica aerogel 4 preferably has a transmittance of at least 50% for visible light with a wavelength greater than 500 nm.

[0050] The metal capillary tubes 5 are made of stainless steel with a polished inner surface to improve light transmission efficiency. Thermal infrared curing adhesive is used to seal the gaps between the metal capillaries 5. Other opaque sealing materials can also be used to fill the gaps between the metal capillaries 5 or to bond the metal capillaries 5 together. The diameter of the silica aerogel 4 matches the inner diameter of the metal capillary tubes 5, and the corresponding diameter is 0.4-1 mm.

[0051] The distance between the conversion target 1 and the incident end of the converter array structure 3 is less than 2 mm, which is used to reduce the influence of the spatial dispersion of the outgoing charged particle beam on the spatial resolution of the entire screen. The material is aluminum, beryllium and cesium iodide, and the thickness is 2-5 mm. The material and thickness of the conversion target 1 are selected according to the type of radiation to ensure that the yield of charged particles after conversion is optimized; for the charged particle beam, the conversion target 1 can serve as a primary threshold to perform primary screening of the charged particle energy. The conversion target 1 can also be omitted in the present invention.

[0052] The Geant4 software was used to simulate and calculate the converter array structure 3 in this embodiment, and its relative light yield under different ray energies was obtained. Figure 5 The left side is the model of the converter array structure 3 set in Geant4, and the right side is the model of the detector 6 that records Cherenkov photons. In this embodiment, the density of the silica aerogel 4 is set to 0.181 g / cm 3 , the corresponding refractive index is 1.038, the diameter is 1mm, the thickness of the metal capillary 5 is 0.1mm, the number of arrays is 100*100, and the thickness of the conversion screen is 20mm. The simulation calculation results are as follows Figure 5 The light yield curves corresponding to charged particles of different energies are shown in the figure, as well as Figure 6 The light yield curves under different energy gamma rays are shown. Figure 6 and Figure 7 It shows that when the refractive index of silica aerogel 4 is 1.038, its light output response to electrons and gamma rays of different energies. From the figure, we can obtain the energy threshold of silica to incident electrons and gamma rays. When the energy of the incident electrons and gamma rays is less than the energy threshold, no light is generated after passing through the converter array structure 3, and the number of photons is 0.

[0053] The converter array structure 3 of the present invention has position resolution and energy threshold characteristics. By adjusting the refractive index of the aerogel material, it can achieve ray detection at different threshold energies, achieving a higher energy threshold than currently commonly used solid Cherenkov converters. The present invention can be applied in inertial confinement fusion experiments, such as pulsed experimental devices such as the National Institute of Fusion (NIF) in the United States and the Shenguang Institute of Physics in China. The silica aerogel array 4 of the present invention can be used to diagnose the reaction time history of 16.7MeV gamma rays generated in the source region and 4.4MeV gamma rays caused by inelastic scattering of fusion neutrons and carbon elements in the outer layer of the target capsule. Under high source intensity conditions, it can also serve as an imaging converter screen. In deep space exploration, it can be used in Cherenkov imaging telescope systems to observe and study the state of gamma pulsars.

[0054] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A Cherenkov detection array screen with selectable energy threshold, characterized by: The device comprises a converter array structure (3) and an external package (2), wherein the converter array structure (3) is arranged in the external package (2), the external package (2) is used to protect the converter array structure (3), and the external package (2) is provided with light holes at the incident end and the output end of the converter array structure (3); The converter array structure (3) comprises an array formed by parallel arranged metal capillaries (5) and silica aerogel (4) filled in the metal capillaries (5), and a light-proof sealing material is provided between adjacent metal capillaries (5); The refractive index of the silica aerogel (4) is 1.01-1.2; the refractive index of the silica aerogel (4) and the corresponding energy threshold are calculated by the following formulas: n=1+kρ Wherein, n is the refractive index, k is the conversion constant between the density and refractive index of silica aerogel (4); ρ is the density of silica aerogel (4); m e is the rest mass of the charged particle; c is the speed of light in air; E e,th is the energy threshold corresponding to the refractive index; The radiation or charged particles enter from the incident end of the converter array structure (3), generate Cherenkov radiation in the converter array structure (3), and are converted into Cherenkov photons, which are emitted from the output end. The metal capillary (5) serves as a cladding of the silica aerogel (4) to improve the efficiency of converting the radiation into secondary charged particles. The thickness of the converter array structure (3) is calculated using the following formula: Wherein, Z is the charge of the charged particles generated in the silica aerogel (4), θ is the angle between the emission direction of the radiated Cherenkov photons and the moving direction of the charged particles, λ1 and λ2 are the wavelengths of the Cherenkov photons, and N p is the number of Cherenkov photons emitted with a wavelength in the range [λ1,λ2], α is the linear attenuation coefficient of silica aerogel (4) to photons, in cm -1 , l is the thickness of the converter array structure (3), that is, the length of the metal capillary (5).

2. The Cherenkov detection array screen with selectable energy threshold according to claim 1, characterized in that: The inner diameter of the metal capillary (5) is 0.4-1 mm, and the wall thickness is 0.1 mm. The diameter of the silica aerogel (4) matches the inner diameter of the metal capillary (5).

3. The Cherenkov detection array screen with selectable energy threshold according to claim 2, characterized in that: The thickness of the converter array structure (3) is 10-50 mm.

4. The Cherenkov detection array screen with selectable energy threshold according to claim 3, characterized in that: The thickness of the converter array structure (3) is 30 mm.

5. The Cherenkov detection array screen with a selectable energy threshold according to any one of claims 1 to 4, characterized in that: The value of k is 0.

21.

6. The Cherenkov detection array screen with selectable energy threshold according to claim 5, characterized in that: It also includes a conversion target (1) arranged at the incident end of the conversion body array structure (3), and the distance between the conversion target (1) and the incident end is less than 2 mm.

7. The Cherenkov detection array screen with selectable energy threshold according to claim 6, characterized in that: The conversion target (1) is made of aluminum, beryllium or cesium iodide and has a thickness of 2-5 mm.

8. The Cherenkov detection array screen with selectable energy threshold according to claim 7, characterized in that: The metal capillary (5) is made of stainless steel, and the inner wall of the stainless steel is polished.

9. The Cherenkov detection array screen with selectable energy threshold according to claim 8, characterized in that: The material of the external package (2) is aluminum, and the external package (2) is blackened and frosted; The metal capillaries (5) are cured by thermal infrared curing glue.

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