A scintillation composite material for neutron-gamma discrimination and a preparation method and application thereof

Abstract

The present application relates to a kind of neutron-gamma discrimination with scintillation composite material and its preparation method and application.The neutron-gamma discrimination with scintillation composite material includes: plastic scintillator, and inorganic scintillation single crystal arranged in array embedded inside plastic scintillator;The volume percentage of the inorganic scintillation single crystal is 1~95 vol%, preferably 10~50 vol%;The size of the inorganic scintillation single crystal is at least 0.1 mm.

Description

TECHNICAL FIELD

[0001] The present application relates to a low-cost, large-size-preparable, scintillation composite material with simultaneous neutron-gamma detection and discrimination advantages and its preparation method and application, belonging to the field of multi-mode radiation detection. BACKGROUND

[0002] The scintillator is the component of the scintillator detector and particle interaction, which can convert high-energy rays or high-energy particles into visible light or ultraviolet light through ionizing radiation. As a light functional material, it is widely used in high-energy physics, medical imaging, security and safety inspection, industrial exploration and other fields. In recent years, with the demand of national major strategic applications such as national defense and military industry, nuclear energy utilization and nuclear physics experiment, nuclear radiation detectors are required to realize effective synchronous detection and discrimination of various particles or rays in the radiation mixed field where neutrons and gamma rays coexist, which requires the scintillation material used to have multi-mode detection and discrimination capability.

[0003] The plastic scintillator is a solid solution of organic scintillation material in plastic, which has the advantages of non-hydration, stable performance, radiation resistance, fast decay, easy processing, large-size preparation and low cost, and its rich hydrogen content makes it have fast neutron detection capability. However, due to the small effective atomic number of plastic scintillator, it can only realize gamma ray counting detection and lacks energy spectrum detection capability. So far, the scintillation crystals that can simultaneously detect neutrons and gamma rays and have relatively good performance include LiI:Eu, Li6Gd(BO3)3:Ce(LGBO), LiCaAlF6:Ce(LiCAF), Cs2LiYCl6:Ce(CLYC), Cs2LiLaBr6:Ce(CLLB), NaI:Tl, Li, etc. In the aspect of gamma ray detection, they have the advantages of excellent energy response linearity, high energy resolution and high light output, etc., while the concentration of Li (up to 95%) can also realize slow neutron detection by nuclear reaction, realizing simultaneous detection and discrimination of gamma rays and slow neutrons. However, from the perspective of crystal growth, the preparation of large-size crystals of this type not only has high cost, but also has great difficulty in growth. So far, there is no multi-mode nuclear detection scintillation material that can be prepared in large size and at low cost. 6 Li (up to 95%) can also realize slow neutron detection by nuclear reaction, realizing simultaneous detection and discrimination of gamma rays and slow neutrons. However, from the perspective of crystal growth, the preparation of large-size crystals of this type not only has high cost, but also has great difficulty in growth. So far, there is no multi-mode nuclear detection scintillation material that can be prepared in large size and at low cost.

[0004] The preparation of existing composite scintillation materials generally selects physical mixing of organic plastic scintillators and inorganic scintillation powders. Due to the easy agglomeration of inorganic scintillation powders, the light emission uniformity of the scintillation composite material is affected. In addition, the inorganic scintillation powders have a large number of surface defects, the prepared scintillation composite material has poor transparency, has serious self-absorption, can only be prepared into detection films or detection sheets, has small thickness, and has poor high-energy ray stopping ability, so it can only be used for low-energy ray detection. SUMMARY

[0005] In view of the above problems, the present application aims to develop a high-performance, low-cost, large-size-preparable scintillation composite material for neutron-gamma detection and discrimination, which can realize synchronous and efficient detection and discrimination of fast neutrons, slow neutrons and gamma rays in a mixed radiation field with coexisting neutron and gamma radiation.

[0006] In one aspect, the present application provides a neutron-gamma discrimination scintillation composite material, comprising: a plastic scintillator, and inorganic scintillation single crystals arranged in an array embedded inside the plastic scintillator; the volume fraction of the inorganic scintillation single crystals is 1-95 vol%, preferably 5-50 vol%, and more preferably 10-50 vol%; the size of the inorganic scintillation single crystals is at least 0.1 mm. If the volume fraction of the inorganic scintillation single crystals is insufficient, the count rate of the scintillation composite material for gamma rays or thermal neutrons is low, and the detection efficiency is low; as the volume fraction of the inorganic scintillation single crystals increases, the detection efficiency for gamma rays or thermal neutrons improves, but the cost also increases significantly accordingly, so by weighing the pros and cons of the preparation cost and detection efficiency of the scintillation composite material, an ideal value of the volume fraction of the inorganic scintillation single crystals can be obtained.

[0007] In the present application, the organic-inorganic composite scintillation material prepared from the organic plastic scintillator and the large-size inorganic scintillation single crystals combines the advantages of the organic plastic scintillator and the inorganic scintillation single crystals, has high light transmittance, and still achieves excellent scintillation performance in large size, so that this new type of scintillation composite material has low cost, can be prepared in large size, has high light yield, high energy resolution, and synchronous neutron-gamma detection and discrimination capability, and is an ideal multi-mode nuclear radiation detection scintillation material.

[0008] Preferably, the inorganic scintillation single crystals are selected from the group consisting of NaI: 6 Li, Tl, CsI: 6 Li, Tl, NaI: 6 Li, CsI: 6 Li, 6 LiI:Eu, Cs3Cu2I5, Cs3Cu2I5:Tl, Cs3Cu2I5: 6 Li, Tl, CsCu2I3, CsCu2I 3: Tl, CsCu2I 3: 6 at least one of Li, Tl, LaBr3, and CeBr3; the thickness of the neutron-gamma discrimination scintillation composite material is at least 0.1 mm.

[0009] Preferably, the inorganic scintillation single crystal includes irregular bulk scintillation single crystal (corresponding size is average size) and regular bulk single crystal; the geometric structure of the regular bulk single crystal is one of a cube (corresponding size is side length), a cuboid (corresponding size is length / width / height), a cylinder (corresponding size is diameter and height), a prism (corresponding size is base side length and height), a sphere (corresponding size is diameter), and a hemisphere (corresponding size is diameter); the size of the inorganic scintillation single crystal is at least 0.1 mm, preferably at least 1 mm, more preferably at least 2 mm, and most preferably at least 5 mm. The size and geometric structure of the inorganic scintillation single crystal should be as consistent as possible, and the light yield and energy resolution should be as similar as possible. Further, the arrangement of the inorganic scintillation single crystal, the aspect ratio, and the volume ratio are optimized by Monte Carlo simulation to ensure that the prepared scintillation composite has excellent scintillation performance such as uniform light emission. The size of the inorganic scintillation single crystal depends on the size of the scintillation composite and increases accordingly as the size of the scintillation composite increases. The height of the inorganic scintillation single crystal is less than the height of the scintillation composite and increases accordingly as the height of the scintillation composite increases. The size and geometric structure of the inorganic scintillation single crystal are consistent, and further, the arrangement of the inorganic scintillation single crystal should be as uniformly distributed as possible in the cover layer plastic scintillator to ensure that the prepared scintillation composite has excellent scintillation performance such as uniform light emission.

[0010] Preferably, the plastic scintillator is composed of a plastic matrix, an initiator, a primary fluorescent dye, and a wave transfer agent; the content of the initiator is 0-1 wt%; the content of the primary fluorescent dye is 1-40 wt%; and the content of the wave transfer agent is 0.01-10 wt%.

[0011] Preferably, the plastic matrix is selected from at least one of polyvinyltoluene, polymethyl methacrylate, polystyrene, polydimethylsiloxane, poly(9-vinylcarbazole), and polyethylene terephthalate.

[0012] Preferably, the initiator is selected from at least one of azo initiators, peroxide initiators, and photoinitiators; preferably, it is selected from at least one of azobisisobutyronitrile, azobisisopentyl nitrile, azobisisoheptyl nitrile, benzoyl peroxide, t-butyl benzoyl peroxide, methyl ethyl ketone peroxide, photoinitiator 184, and photoinitiator BAPO.

[0013] Preferably, the primary fluorescent dye is selected from at least one of 2,5-diphenyloxazole, p-terphenyl, 2-(4'-tert-butylphenyl)-5-(4'-biphenyl)-1,3,4-oxadiazole, and 2-(4-biphenyl)-5-phenyloxadiazole.

[0014] Preferably, the wave shifter is selected from one of 1,4-bis(5-phenyl-2-oxazolyl)benzene, 1,4-bis(2-methylphenyl)benzene, 1,4-di(4-methylphenyl)benzene, 9,10-diphenylanthracene, and coumarin dye, or a combination thereof.

[0015] In another aspect, the present invention provides a method for preparing a scintillation composite material for neutron-gamma discrimination, comprising:

[0016] (1) In an inert atmosphere, a plastic matrix monomer, an initiator (0-1 wt%), a primary fluorescent dye (1-40 wt%), and a wave shifter (0.01-10 wt%) are added to a reaction mold to obtain a uniform clear solution, and the reaction mold is sealed;

[0017] (2) sealing the reaction mold in step (1) and heating it for prepolymerization, so that the base layer is slightly solidified and can support the scintillation crystal, thereby obtaining a partially polymerized base layer;

[0018] (3) In an inert atmosphere, a plurality of inorganic scintillating single crystals are placed on a partially polymerized substrate layer in an array arrangement and sealed, and heating and polymerization are continued to make the inorganic scintillating single crystals and the partially polymerized substrate layer completely adhere to form a whole;

[0019] (4) Pour a clear solution of a plastic matrix monomer, an initiator (0-1 wt%), a primary fluorescent dye (1-40 wt%), and a wave shifter (0.01-10 wt%) into a reaction mold to form a covering layer (the height of the covering layer solution is at least above the base layer and the inorganic scintillating single crystal), seal the reaction mold, and heat until the covering layer is completely solidified. Then, heat it to a higher temperature and keep it warm for 1-7 days to ensure that the remaining monomers are completely solidified. Finally, slowly cool it to room temperature to obtain a scintillation composite material for neutron-gamma discrimination.

[0020] On the other hand, the present invention provides an application of a scintillation composite material for neutron-gamma discrimination, wherein the scintillation composite material for neutron-gamma discrimination is used to detect and discriminate gamma rays, fast neutrons and slow neutrons; the scintillation composite material for neutron-gamma discrimination is used in detectors in the fields of border security, homeland security, environmental testing, and nuclear energy utilization radiation mixed fields.

[0021] Beneficial effects:

[0022] The scintillation composite material prepared by the present invention not only has the advantages of low cost, large size, and non-deliquescent properties, but also has excellent scintillation properties, including high light yield, high energy resolution, and neutron-gamma detection and discrimination. It can be used to detect gamma rays, fast neutrons, and thermal neutrons, and has important application prospects in security and safety inspection fields involving nuclear weapons testing, nuclear non-proliferation, and other areas where neutron radiation and gamma radiation coexist. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Sample photo of the scintillating composite material prepared for Example 1 under natural light;

[0024] Figure 2 Sample photo of the scintillating composite material prepared for Example 2 under natural light;

[0025] Figure 3 Fluorescence spectra of the prepared inorganic scintillation crystal, plastic scintillator and transmission spectrum of the plastic scintillator;

[0026] Figure 4 X-ray excitation emission spectra of the prepared inorganic scintillation crystal and plastic scintillator;

[0027] Figure 5 Scintillating composite material prepared 137 Pulse height spectrum under Cs source;

[0028] Figure 6 Scintillating composite material prepared 137 Pulse height spectrum under Cs source;

[0029] Figure 7 Scintillating composite material prepared 137 Scintillation decay time under Cs source;

[0030] Figure 8 Neutron-gamma pulse shape discrimination spectrum of the prepared scintillating composite material. DETAILED DESCRIPTION

[0031] The present application is further illustrated by the following examples, which are not intended to limit the present application.

[0032] In the present application, a low-cost, large-size-preparable, high light yield, high energy resolution and neutron-gamma detection and discrimination capable scintillating composite material has high practical value in the field of radiation detection with coexistence of neutron and gamma radiation.

[0033] In an embodiment of the present application, the scintillating composite material comprises a plastic scintillator and an embedded body. The plastic scintillator comprises a pre-polymerized base layer (A) and a cover layer (B) (substantially as a whole). The embedded body is an inorganic scintillation single crystal (C). Compared with conventional scintillation powder, the scintillation single crystal has a complete structure, small light scattering degree and high transmittance, which can make the scintillation light completely transmit out and has ideal scintillation performance. Moreover, the inorganic scintillation single crystal has good light transmittance, and large size can still achieve high light output, so that low-energy and high-energy radiation detection can be achieved. The following exemplarily illustrates the preparation method of the new scintillating composite material for neutron-gamma discrimination with high performance, low cost and large size.

[0034] The glass reaction vessel is cleaned with deionized water, ethanol, and acetone, at least three times in sequence, and then is placed in an oven for vacuum heating. The temperature of the vacuum heating is 120°C, and the time can be more than 24 hours.

[0035] In an inert atmosphere, the monomers of the plastic scintillator, initiator (0-1 wt%), primary fluorescent dye (1-40 wt%), and wave mover (0.01-10 wt%) are added to the cleaned reaction mold, dissolved and obtained a uniform solution system, and the reaction mold is sealed. As a further preferred solution, the monomers of the plastic scintillator should be purified to remove stabilizers and water, the purity of the initiator, fluorescent dye, and wave mover is more than 99%, and the ingredient environment is an inert gas environment (a glove box filled with argon or nitrogen).

[0036] The sealed reaction mold is placed in an oven or heated to a certain temperature (70-120°C) using a heat transfer fluid (oil, water, etc.), and pre-polymerized (2-120 hours) to support the inorganic scintillation single crystal to form the base layer (A) of the scintillation composite material. If this step is completely cured, the base layer cannot be adhered to the inorganic scintillation single crystal as a whole, further causing the base layer and the cover layer to also form a scintillation composite material. If the pre-polymerization time of this step is insufficient, the base layer cannot support the inorganic scintillation single crystal, and the inorganic single crystal will tilt or even fall to the bottom of the base layer, causing uneven arrangement of the inorganic single crystal and even deliquescence, which further degrades the scintillation performance of the scintillation composite material, such as light yield and energy resolution.

[0037] In an inert atmosphere, several inorganic scintillation single crystals (C) with similar light yield and energy resolution, the same size and geometric structure are placed on the base layer (A), and the reaction mold is sealed and placed in an oven or heated to a certain temperature (70-120°C) using a heat transfer fluid (oil, water, etc.), and polymerized to completely adhere the inorganic scintillation single crystal (C) to the base layer (A) and form a whole. Preferably, the surface of the inorganic scintillation single crystal also needs to be pretreated, and the surface of the single crystal is thoroughly cleaned to eliminate the unsaturated bonds and surface oil as much as possible.

[0038] The monomer, initiator (0-1 wt%), primary fluorescent dye (1-40 wt%) and wave mover (0.01-10 wt%) of the plastic scintillator are premixed and dissolved to obtain a uniform and clear solution. The clear solution is poured into a reaction mold to form a cover layer (B), and the height of the cover layer solution is at least higher than the base layer and the inorganic scintillation single crystal to ensure that the deliquescent inorganic scintillation single crystal (C) is encapsulated in the plastic scintillator. After the reaction mold is sealed, it is placed in an oven or uses a heat transfer fluid (oil, water, etc.) to heat to a certain temperature (70-120°C), and is incubated for several weeks (for example, 1-8 weeks) until the cover layer is completely cured. Then, the polymerization temperature is increased to 80-130°C and incubated for 1-7 days to achieve the purpose of post-curing to remove a small amount of un-polymerized monomer. As a further preferred solution, the base layer and the cover layer should be polymerized to a certain extent, and a vacuum should be used to remove bubbles in the system, and the embedded inorganic scintillation single crystal has the same size and geometry, and has similar energy resolution and light yield. After the polymerization is completed, the temperature is slowly reduced to room temperature to reduce internal stress. The cured scintillation composite material is taken out of the reaction mold, cut and polished to obtain the required scintillation composite material.

[0039] In the present application, the plastic scintillator is used to detect fast neutrons, and the inorganic scintillation single crystal is used to detect slow neutrons and gamma rays. The new scintillation composite material described in the present application has the advantages of low cost, large size preparation, high sensitivity, multi-mode detection and discrimination, and can be used for detecting and discriminating gamma rays, fast neutrons and slow neutrons, and has important application prospects in the field of mixed radiation such as border security, homeland security, environmental detection, nuclear energy utilization, etc.

[0040] The following examples are further illustrated to explain the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application. The specific process parameters in the following examples are only one example in the appropriate range, that is, those skilled in the art can make appropriate selection within the range according to the description herein, and are not limited to the specific values in the following examples.

[0041] Example 1:

[0042] In this embodiment 1, the scintillation composite material substrate is a plastic scintillator PVT, which comprises a base layer (A) and a cover layer (B) which are pre-polymerized, and the embedded body is 4 inorganic scintillation single crystals NaI with a size of 12x12x20mm: 6 Li, Tl.

[0043] In this embodiment 1, the neutron-gamma detection and discrimination scintillation composite material PVT-NaI: 6The method for preparing Li, Tl comprises:

[0044] Step 1: A glass reaction vessel with a diameter of 53 mm is cleaned with deionized water, ethanol and acetone in sequence, and then is placed in an oven for vacuum heating at 120°C for drying for more than 24 hours.

[0045] Step 2: In an inert atmosphere, the matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-10 wt%) and wave transfer agent (0.01-2 wt%) are added into the glass reaction vessel cleaned in Step 1, are dissolved and a uniform solution system is obtained, and the glass reaction vessel is sealed.

[0046] Step 3: The sealed glass reaction vessel in Step 2 is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-90°C, and is incubated for pre-polymerization for 12-120 hours to a degree capable of supporting inorganic scintillation single crystals, to form a substrate layer (A) of a scintillation composite material.

[0047] Step 4: In an inert atmosphere, four inorganic scintillation single crystals NaI: 6 Li, Tl with similar light yield and energy resolution are placed on the substrate layer (A) described in Step 3, the reaction glass vessel is sealed, and is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-90°C, and is incubated for polymerization until the inorganic scintillation single crystals NaI: 6 Li, Tl are completely bonded with the substrate layer (A) and form an entirety.

[0048] Step 5: The matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-20 wt%) and wave transfer agent (0.01-2 wt%) are pre-mixed and dissolved to obtain a uniform and clear solution, and the solution is poured into the reaction glass vessel described in Step 4 to form a cover layer (B) to ensure that the deliquescent inorganic scintillation single crystals (C) are encapsulated in the plastic scintillator. After the reaction glass vessel is sealed, it is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-90°C, and is incubated for polymerization for 2-6 weeks until the cover layer is completely cured. Subsequently, the polymerization temperature is increased to 80-100°C and is incubated for 1-7 days to achieve the purpose of post-curing to remove a small amount of un-polymerized monomers.

[0049] Step 6: After the polymerization is completed, the temperature is slowly reduced to room temperature to reduce internal stress. The cured scintillation composite material is taken out of the glass reaction vessel, is cut and polished to obtain the required scintillation composite material. The obtained scintillation composite material has a diameter of 53 mm and a height of 30 mm, and the content of the inorganic scintillation single crystals NaI: 6 Li, Tl is 17.4 vol%.

[0050] Example 2:

[0051] The scintillating composite matrix in this embodiment 2 is plastic scintillator PVT, wherein the plastic scintillator comprises two parts of a pre-polymerized base layer (A) and a cover layer (B), and the inclusions are four inorganic scintillating single crystals NaI of 8x8x20mm: 6 Li, Tl.

[0052] In this embodiment 2, the neutron-gamma detection and discrimination scintillating composite PVT-NaI: 6 The preparation method of Li, Tl includes:

[0053] Step 1: A glass reaction container with a diameter of 53mm is cleaned with deionized water, ethanol, and acetone in sequence for three times, and then is placed in an oven for vacuum heating at 120°C for drying for more than 24 hours.

[0054] Step 2: In an inert atmosphere, the matrix monomer, initiator (0-1wt%), primary fluorescent dye (1-10wt%), and wave transfer agent (0.01-2wt%) are added into the glass reaction container cleaned in step 1 to form a uniform solution system, and the glass reaction container is sealed.

[0055] Step 3: The sealed glass reaction container in step 2 is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-100°C, and is incubated for pre-polymerization for 12-96 hours to a degree capable of supporting inorganic scintillating single crystals, to form a base layer (A) of scintillating composite.

[0056] Step 4: In an inert atmosphere, four inorganic scintillating single crystals NaI: 6 Li, Tl with similar light yield and energy resolution are placed on the base layer (A) in step 3, the reaction glass container is sealed, and is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-100°C, and is incubated for polymerization until the inorganic scintillating single crystals NaI: 6 Li, Tl and the base layer (A) are completely adhered and form an integral whole.

[0057] Step 5: The matrix monomer, initiator (0-1wt%), primary fluorescent dye (1-20wt%), and wave transfer agent (0.01-2wt%) are pre-mixed and dissolved to form a uniform and clear solution, and the solution is poured into the reaction glass container in step 4 to form a cover layer (B) to ensure that the deliquescent inorganic scintillating single crystals (C) are encapsulated in the plastic scintillator. After the reaction glass container is sealed, it is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating, and is incubated for polymerization for 2-5 weeks until the cover layer is completely cured. Subsequently, the polymerization temperature is increased to 80-100°C and is incubated for 1-7 days to achieve the purpose of post-curing to remove a small amount of un-polymerized monomers.

[0058] Step 6: After the polymerization is completed, the temperature is slowly decreased to room temperature to reduce internal stress. The cured scintillating composite is removed from the glass reaction vessel, cut and polished to obtain the desired scintillating composite. The obtained scintillating composite has a diameter of 53 mm and a height of 30 mm, wherein the inorganic scintillating single crystal is NaI: 6 The content of Li, Tl is 7.7 vol%.

[0059] Example 3:

[0060] In this example 3, the scintillating composite substrate is plastic scintillator PVT, wherein the plastic scintillator comprises two parts of a pre-polymerized base layer (A) and a cover layer (B), and the inlay is 9 inorganic scintillating single crystals CsCu2I3 with a diameter of 11 mm and a height of 20 mm.

[0061] In this example 3, the preparation method of the scintillating composite PVT-CsCu2I3 for neutron-gamma detection and discrimination comprises:

[0062] Step 1: A glass reaction vessel with a diameter of 53 mm is cleaned with deionized water, ethanol, and acetone in sequence, and then placed in an oven for vacuum heating at 120°C for drying for more than 24 hours.

[0063] Step 2: In an inert atmosphere, the substrate monomer, initiator (0-1 wt%), primary fluorescent dye (1-10 wt%), and wave mover (0.01-2 wt%) are added to the glass reaction vessel cleaned in step 1, dissolved and obtained a uniform solution system, and the glass reaction vessel is sealed.

[0064] Step 3: The sealed glass reaction vessel in step 2 is placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-90°C, and incubated for pre-polymerization for 24-96 hours to a degree that can support inorganic scintillating single crystals, forming a base layer (A) of the scintillating composite.

[0065] Step 4: In an inert atmosphere, 9 inorganic scintillating single crystals CsCu2I3 with a diameter of 11 mm and a height of 20 mm having similar light yield and energy resolution are placed on the base layer (A) described in step 3, the reaction glass vessel is sealed, and then placed in an oven or uses a heat transfer fluid (oil, water, etc.) for heating at 70-90°C, and incubated for polymerization until the inorganic scintillating single crystals CsCu2I3 and the base layer (A) are completely adhered and form a whole.

[0066] Step 5: The matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-20 wt%) and wave transfer agent (0.01-2 wt%) are premixed and dissolved to form a uniform clear solution, and the solution is poured into the reaction glass container described in step 4 to form a cover layer (B) to ensure that the moisture-sensitive inorganic scintillating single crystal (C) is encapsulated in the plastic scintillator. After sealing the reaction glass container, it is placed in an oven or heated using a heat transfer fluid (oil, water, etc.), and the polymerization is incubated for 2-6 weeks until the cover layer is completely cured. Then the polymerization temperature is increased to 80-100°C and incubated for 1-4 days to achieve post-curing to remove a small amount of unreacted monomer.

[0067] Step 6: After the polymerization is completed, the temperature is slowly reduced to room temperature to reduce internal stress. The cured scintillating composite material is removed from the glass reaction container, cut and polished to obtain the desired scintillating composite material. The resulting scintillating composite material has a diameter of 53 mm and a height of 30 mm, and the content of the inorganic scintillating single crystal CsCu2I3 is 25.8 vol%.

[0068] Example 4:

[0069] In this example 4, the scintillating composite material matrix is a plastic scintillator PVT, which comprises a pre-polymerized base layer (A) and a cover layer (B), and the embedded body is 9 inorganic scintillating single crystals Cs3Cu2I5:Tl with a diameter of 11 mm and a height of 20 mm.

[0070] In this example 3, the preparation method of the scintillating composite material PVT-Cs3Cu2I5:Tl for neutron-gamma detection and discrimination comprises:

[0071] Step 1: A glass reaction container with a diameter of 53 mm is cleaned with deionized water, ethanol, and acetone in sequence, and then placed in an oven for vacuum heating at 120°C for drying for more than 24 hours.

[0072] Step 2: In an inert atmosphere, the matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-10 wt%) and wave transfer agent (0.01-2 wt%) are added to the glass reaction container cleaned in step 1, dissolved and a uniform solution system is obtained, and the glass reaction container is sealed.

[0073] Step 3: The sealed glass reaction container in step 2 is placed in an oven or heated using a heat transfer fluid (oil, water, etc.) at 70-100°C, and incubated for 24-96 hours to support the inorganic scintillating single crystal to form the base layer (A) of the scintillating composite material.

[0074] Step 4: Inert atmosphere, 9 inorganic scintillating single crystal Cs3Cu2I5:Tl with similar light yield and energy resolution, 11 mm in diameter, 20 mm in height, are placed on the base layer (A) described in step 3. The reaction glass container is sealed and placed in an oven or using heat transfer fluid (oil, water, etc.) to heat at 70-100°C, and incubate polymerization until the inorganic scintillating single crystal Cs3Cu2I5:Tl and the base layer (A) are completely adhered and form a whole.

[0075] Step 5: The matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-20 wt%) and wave transfer agent (0.01-2 wt%) are pre-mixed and dissolved to obtain a uniform and clear solution, and the solution is poured into the reaction glass container described in step 4 to form the cover layer (B) to ensure that the deliquescent inorganic scintillating single crystal (C) is encapsulated in the plastic scintillator. The reaction glass container is sealed and placed in an oven or using heat transfer fluid (oil, water, etc.) to heat and incubate polymerization for 2-6 weeks until the cover layer is completely cured. Then the polymerization temperature is increased to 80-110°C and incubated for 1-7 days to achieve the purpose of post-curing to remove a small amount of un-polymerized monomer.

[0076] Step 6: After the polymerization is completed, the temperature is slowly reduced to room temperature to reduce internal stress. The cured scintillating composite material is taken out of the glass reaction container, cut and polished to obtain the required scintillating composite material. The obtained scintillating composite material is 53 mm in diameter and 30 mm in height, and the content of inorganic scintillating single crystal Cs3Cu2I5:Tl is 25.8 vol%.

[0077] Example 5:

[0078] In this embodiment 5, the scintillating composite material substrate is a plastic scintillator PVT, which comprises a pre-polymerized base layer (A) and a cover layer (B), and the embedded body is 4 inorganic scintillating single crystals Cs3Cu2I5 with a size of 20x20x20 mm.

[0079] In this embodiment 3, the preparation method of the scintillating composite material PVT-Cs3Cu2I5 for neutron-gamma detection and discrimination comprises:

[0080] Step 1: A glass reaction container with a diameter of 53 mm is cleaned with deionized water, ethanol, and acetone in sequence, and then placed in an oven for vacuum heating at 120°C for more than 24 hours.

[0081] Step 2: In an inert atmosphere, the matrix monomer, initiator (0-1 wt%), primary fluorescent dye (1-10 wt%) and wave transfer agent (0.01-2 wt%) are added to the glass reaction container cleaned in step 1, dissolved and obtained a uniform solution system, and the glass reaction container is sealed.

[0082] Step 3: Put the sealed glass reaction vessel in Step 2 into an oven or use a heat transfer fluid (oil, water, etc.) to heat at 80-100°C and incubate for 24-96 hours to a degree that the inorganic scintillation single crystal can be supported, forming a base layer (A) of the scintillation composite material.

[0083] Step 4: In an inert atmosphere, place 4 inorganic scintillation single crystals Cs3Cu2I5 with similar light yield and energy resolution of 20x20x20mm on the base layer (A) described in Step 3, seal the reaction glass vessel, and put it into an oven or use a heat transfer fluid (oil, water, etc.) to heat at 80-100°C and incubate for polymerization until the inorganic scintillation single crystals Cs3Cu2I5 are completely adhered to the base layer (A) and form a whole.

[0084] Step 5: Pre-mix the matrix monomer, initiator (0-1wt%), primary fluorescent dye (1-20wt%), and wave mover (0.01-2wt%) to obtain a uniform clear solution, pour the solution into the reaction glass vessel described in Step 4 to form a cover layer (B) to ensure that the deliquescent inorganic scintillation single crystal (C) is encapsulated in the plastic scintillator. After sealing the reaction glass vessel, put it into an oven or use a heat transfer fluid (oil, water, etc.) to heat and incubate for polymerization for 2-6 weeks until the cover layer is completely cured. Then increase the polymerization temperature to 90-110°C and incubate for 1-3 days to achieve the purpose of post-curing to remove a small amount of un-polymerized monomer.

[0085] Step 6: After the polymerization is completed, slowly reduce the temperature to room temperature to reduce internal stress. Take out the cured scintillation composite material from the glass reaction vessel, cut and polish to obtain the required scintillation composite material. The obtained scintillation composite material is 53mm in diameter and 30mm in height, and the content of inorganic scintillation single crystal Cs3Cu2I5 is 48.4vol%.

[0086] Figure 8 The neutron / gamma pulse shape discrimination spectrum of the scintillation composite material provided by the present application. The scintillation composite material is 53mm in diameter and 30mm in height, and the content of inorganic scintillation single crystal NaI: 6 Li, Tl is 17.4vol%. The neutron-gamma pulse shape discrimination test results show that the PVT-NaI: 6 Li, Tl composite scintillation material has good neutron-gamma discrimination quality factor. The obtained organic-inorganic composite scintillation material can be applied in the field of neutron-gamma detection and discrimination.

[0087] Figure 1 The sample photo of the scintillation composite material provided by Example 1 of the present application under natural light. The scintillation composite material is PVT-NaI: 6Li, Tl composite scintillation material, diameter 53 mm, height 30 mm, wherein NaI: 6 Li, Tl content is 17.4 vol%.

[0088] Figure 2 Sample photo of the scintillation composite material provided for the embodiment 2 of the present application under natural light. The scintillation composite material is PVT-NaI: 6 Li, Tl composite scintillation material, diameter 53 mm, height 30 mm, wherein NaI: 6 Li, Tl content is 7.7 vol%.

[0089] Figure 3 Inorganic scintillation single crystal NaI provided for the present application: 6 Fluorescence spectrum of Li, Tl, plastic scintillator PVT and transmission spectrum of plastic scintillator PVT.

[0090] Figure 4 Inorganic scintillation single crystal NaI provided for the present application: 6 X-ray excitation emission spectrum of Li, Tl and plastic scintillator PVT. Figure 4 It is shown that the inorganic scintillation single crystal NaI: 6 Li, Tl emits peaks at 341 nm and 417 nm under X-ray excitation, and plastic scintillator PVT emits peaks at 422 nm and 440 nm under X-ray excitation.

[0091] Figure 5 Scintillation composite material provided for the present application 137 Pulse height spectrum under Cs source. PVT-NaI: 6 Li, Tl composite scintillation material, diameter 53 mm, height 30 mm, wherein NaI: 6 Li, Tl content is 17.4 vol%; the size of the standard sample NaI: Tl is diameter 25 mm, height 25 mm, and the light yield is 44,600 photons / MeV. PVT-NaI: 6 Li, Tl composite scintillation material in 137 Under Cs source gamma ray excitation, the light yield is 45,300 photons / MeV, and the energy resolution is 13.6% @662 keV.

[0092] Figure 6 Scintillation composite material provided for the present application 137 Pulse height spectrum under Cs source. PVT-NaI: 6 Li, Tl composite scintillation material, diameter 53 mm, height 30 mm, wherein NaI: 6The content of Li, Tl is 7.7 vol%; the size of the standard sample NaI: Tl is 25 mm in diameter and 25 mm in height, and the light yield is 44,600 photons / MeV. PVT-NaI: 6 The Li, Tl composite scintillation material has a light yield of 34,100 photons / MeV under the excitation of gamma rays from a Cs source. 137 The channel number of the composite scintillation material is 491, and the channel number of the standard sample NaI: Tl is 642, so the relative light yield of the composite scintillation material is 34,100 photons / MeV. In addition, when the full-energy peak counts of the composite scintillation material and the standard sample NaI: Tl both reach 500, the time used is 450 seconds and 96 seconds, respectively, so the NaI: 6 The content of Li, Tl in the PVT-NaI is 7.7 vol%. 6 The gamma ray detection efficiency of the Li, Tl composite scintillation material is about 21% of that of the standard sample NaI: Tl with a diameter of 25 mm and a height of 25 mm.

[0093] Figure 7 The scintillation composite material provided by the present application 137 The scintillation decay time under the excitation of a Cs source. PVT-NaI: 6 The Li, Tl composite scintillation material has a diameter of 53 mm and a height of 30 mm, and the content of NaI: 6 The content of Li, Tl is 17.4 vol%. Figure 7 The PVT-NaI is shown: 6 The Li, Tl composite scintillation material has a light yield of 34,100 photons / MeV under the excitation of gamma rays from a Cs source. 137 The decay time under the excitation of gamma rays from a Cs source can be fitted by a two-exponential function, in which the fast component of the decay time is 4.84 ns, accounting for 66%, and the slow component is 263.58 ns, accounting for 34%.

[0094] Finally, it is necessary to point out that the above examples are only used to further illustrate the technical solutions of the present application and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application all belong to the protection scope of the present application.

Claims

1. A method for preparing a scintillation composite material for neutron-gamma discrimination, characterized in that: include: A plastic scintillator and inorganic scintillating single crystals arranged in an array and embedded in the plastic scintillator; the volume proportion of the inorganic scintillating single crystals is 10 to 48.4 vol%; the size of the inorganic scintillating single crystals is at least 0.1 mm; the plastic scintillator comprises a pre-polymerized base layer and a cover layer; The preparation method of the scintillation composite material for neutron-gamma discrimination comprises: (1) In an inert atmosphere, the monomers of the plastic matrix, the initiator, the primary fluorescent dye, and the wave shifter are added to the reaction mold to obtain a uniform clear solution, and then the reaction mold is sealed; (2) sealing the reaction mold in step (1) and heating it to 70-120°C for prepolymerization for 2-120 hours, so that the plastic matrix is ​​slightly solidified and can support the scintillation crystal, thereby obtaining a partially polymerized base layer; (3) In an inert atmosphere, several inorganic scintillating single crystals with similar light yield and energy resolution, the same size and geometric structure are placed on the partially polymerized substrate in an array arrangement and the reaction mold is sealed. The heating and polymerization are continued until the inorganic scintillating single crystal and the partially polymerized substrate are completely adhered to form a whole; (4) Pour the clarified solution formed by the monomer of the plastic matrix, the initiator, the primary fluorescent dye and the wave shifter into the reaction mold in step (3) to form a covering layer, seal the reaction mold, and heat until the covering layer is completely solidified, then heat it to a higher temperature and keep it warm for 1 to 7 days, and finally slowly cool it to room temperature to obtain a scintillation composite material for neutron-gamma discrimination.

2. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 1, characterized in that: The inorganic scintillating single crystal is selected from NaI: 6 Li, Tl, CsI: 6 Li, Tl, NaI: 6 Li、CsI: 6 Li, 6 LiI:Eu, Cs3Cu2I5, Cs3Cu2I5:Tl, Cs3Cu2I5: 6 Li,Tl,CsCu2I3,CsCu2I 3: Tl、CsCu2I 3: 6 One or more of Li, Tl, LaBr3, and CeBr3; the thickness of the scintillation composite material for neutron-gamma discrimination is at least 0.1 mm.

3. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 1, characterized in that: The inorganic scintillation single crystal includes irregular block scintillation single crystal and regular block single crystal; the geometric structure of the regular block single crystal is one of a cube, a cuboid, a cylinder, a prism, a sphere, and a hemisphere.

4. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 1, wherein: The plastic scintillator consists of a plastic matrix, an initiator, a primary fluorescent dye and a wave shifter; the content of the initiator is 0-1 wt %; the content of the primary fluorescent dye is 1-40 wt %; and the content of the wave shifter is 0.01-10 wt %.

5. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 4, characterized in that: The plastic matrix is ​​selected from at least one of polyvinyl toluene, polymethyl methacrylate, polystyrene, polydimethylsiloxane, poly(9-vinylcarbazole), and polyethylene terephthalate.

6. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 4, characterized in that: The initiator is selected from at least one of an azo initiator, a peroxide initiator and a photoinitiator.

7. The method for preparing the scintillation composite material for neutron-gamma discrimination according to claim 6, characterized in that: The initiator is selected from at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, photoinitiator 184, and photoinitiator BAPO.

8. The scintillation composite material for neutron-gamma discrimination according to claim 4, characterized in that: The primary fluorescent dye is selected from at least one of 2,5-diphenyloxazole, p-terphenyl, 2-(4'-tert-butylphenyl)-5-(4'-biphenyl)-1,3,4-oxadiazole, and 2-(4-biphenyl)-5-phenyloxadiazole.

9. The scintillation composite material for neutron-gamma discrimination according to claim 4, characterized in that: The wave shifter is selected from one of 1,4-bis(5-phenyl-2-oxazolyl)benzene, 1,4-bis(2-methylphenyl)benzene, 1,4-di(4-methylphenyl)benzene, 9,10-diphenylanthracene, and coumarin dye, or a combination thereof.

10. An application of a scintillation composite material for neutron-gamma discrimination prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The scintillation composite material for neutron-gamma discrimination is used for detecting and discriminating gamma rays, fast neutrons and slow neutrons; the scintillation composite material for neutron-gamma discrimination is used for detectors in the fields of border security, homeland security, environmental testing, and nuclear energy utilization radiation mixed fields.

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