A ternary co-doped LaBr3 scintillation crystal for neutron detection and its preparation method

Abstract

This invention relates to a ternary co-doped LaBr3 scintillation crystal for neutron detection and its preparation method. The chemical composition of the ternary co-doped LaBr3 scintillation crystal for neutron detection is A. x B y Ce z La 1‑x‑y‑ z Br 3‑2x‑y Wherein: A is a +1 valent alkali metal ion, preferably Li, 6 One of the following ions: Li, Na, K, Rb, and Cs, more preferably... 6 Li; B is a +2 valent alkaline earth metal ion, preferably one of Mg, Ca, Sr, and Ba ions, more preferably Sr; 0.00001≤x≤0.0025, 0.001≤y≤0.005, 0.03≤z≤0.08, preferably x=0.00005, y=0.003, z=0.05.

Description

Technical Field

[0001] This invention belongs to the field of neutron multimode radiation detection technology, specifically relating to a ternary co-doped LaBr3 scintillation crystal for neutron detection and its preparation method. Background Technology

[0002] Scintillators are energy converters that transform incident high-energy rays or particles into ultraviolet or visible light. Due to this unique property, scintillators are used as core components of radiation detectors and have demonstrated significant application value in fields such as high-energy physics, nuclear medicine imaging, homeland security, and industrial detection. However, existing scintillator materials have limitations in scintillation decay time, light yield, and energy resolution, restricting their further application in high-performance radiation detectors. Therefore, to meet the ever-evolving demands for higher performance scintillation detection materials in scientific research, medicine, and industry, the development of novel multi-mode radiation detection scintillator materials is urgently needed.

[0003] Tradition 3 He proportional gas counter tube due to 3 The supply of hexagenines (H) is insufficient, severely limiting their application. Scintillation crystals, with their advantages of easy growth and excellent scintillation performance, have become the most promising neutron detection materials in recent years. Since neutrons cannot ionize matter, they cannot be directly detected. Scintillation crystal detection materials typically utilize the nuclear reaction between certain elements in the crystal and neutrons, indirectly detecting neutrons by measuring the product nuclei and reaction energy. An incident neutron beam undergoes a nuclear reaction with isotopes in the scintillation crystal, releasing secondary rays or particles. These secondary rays or particles are absorbed by the scintillation crystal, and the resulting electrons and holes relax and diffuse to produce luminescent centers in an excited state. When these excited luminescent centers transition back to the ground state, they emit ultraviolet or visible light. Generally, neutron detection primarily detects the alpha rays generated by the reaction and the fluorescence produced by the crystal.

[0004] Traditional neutron detection materials, such as lithium glass scintillators, have a fast response time and can distinguish neutrons and gammas through pulse height and pulse shape discrimination, but their light yield and energy resolution are poor. 6 LiF / ZnS(Ag) has a high light yield of 160,000 ph / n, but it has low sensitivity to gamma rays and cannot be obtained in single crystals; novel potassium cryolite compounds have high light output and excellent linear non-proportional response, but their gamma ray energy resolution is slightly inferior to that of LaBr3. Summary of the Invention

[0005] To address the technical problems of poor gamma-ray energy resolution in existing neutron-gamma discrimination scintillation crystals, the present invention aims to provide a neutron detection scintillation crystal and its preparation method, which can be widely used in the field of multimode radiation detection.

[0006] In a first aspect, the present invention provides a ternary co-doped LaBr3 scintillation crystal for neutron detection, wherein the chemical composition of the ternary co-doped LaBr3 scintillation crystal for neutron detection is A. x B y Ce z La 1-x-y-z Br 3-2x-y ;in: A is a +1 valent alkali metal ion, preferably Li, 6 One of the following ions: Li, Na, K, Rb, and Cs, more preferably... 6 Li; B is a +2 valent alkaline earth metal ion, preferably one of Mg, Ca, Sr, and Ba ions, more preferably Sr; 0.00001≤x≤0.0025, 0.001≤y≤0.005, 0.03≤z≤0.08, preferably x=0.00005, y=0.003, z=0.05.

[0007] Preferably, the ternary co-doped LaBr3 scintillation crystal for neutron detection is a bulk single crystal; more preferably, when the ternary co-doped LaBr3 scintillation crystal for neutron detection is a bulk single crystal, the size of the ternary co-doped LaBr3 scintillation crystal for neutron detection is not less than 20 mm in at least one dimension.

[0008] Preferably, the scintillation decay time of the ternary co-doped LaBr3 scintillation crystal for neutron detection is 20 ns to 35 ns.

[0009] Preferably, the light yield of the ternary co-doped LaBr3 scintillation crystal for neutron detection is 70,000 ± 2,000 ph. / MeV.

[0010] Preferably, the neutron detection ternary co-doped LaBr3 scintillation crystal can achieve an energy resolution of 2.24% at 662 keV.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned ternary co-doped LaBr3 scintillation crystal for neutron detection, the method comprising the following steps: First, according to the chemical composition A of the ternary co-doped LaBr3 scintillation crystal for neutron detection... x B y Ce z La 1-x-y- z Br 3-2x-yThe molar ratios of the elements in the mixture were weighed and mixed to obtain the raw material powder; then, the Bridgman method was used to grow the crystal to obtain the ternary co-doped LaBr3 scintillation crystal for neutron detection.

[0012] Preferably, the ABr powder, BBr2 powder, CeBr3 powder and LaBr3 powder are all in anhydrous state and have a purity ≥99.99%.

[0013] Preferably, the Bridgman method includes the following steps: (1) Place the raw material powder in a quartz crucible with a capillary tip structure and evacuate it, then dry the material and seal the crucible. (2) Place the sealed quartz crucible vertically in the center of the crystal growth furnace, then raise the temperature of the crystal growth furnace to the melting point of the raw material powder and keep it warm so that the raw material powder is completely melted and fully mixed. (3) Adjust the height and position of the quartz crucible and the furnace temperature so that the temperature of the capillary tip structure of the quartz crucible is maintained within ±10℃ of the crystallization point of the ternary co-doped LaBr3 scintillation crystal for neutron detection. (4) The quartz crucible is lowered into the crystal growth furnace to grow the crystal. After the growth is completed, the temperature is lowered to obtain the neutron detection ternary co-doped LaBr3 scintillation crystal.

[0014] Preferably, in step (1), the vacuum level of the vacuum pump is 10. -2 ~10 -7 Pa; The drying temperature is 200℃, and the time is 4-6 hours; The size of the capillary tip structure is ≤3cm.

[0015] Preferably, in step (4), the longitudinal temperature gradient of the crystal growth furnace is controlled to be 5-50℃ / cm, and the quartz crucible is lowered at a rate of 0.01-10.0mm / h. The cooling method is as follows: the growth furnace is first cooled to 600-950℃ at a rate of 5-10℃ / h, held at that temperature for 24 hours, and then cooled to room temperature at a rate of 10-15℃ / h.

[0016] Beneficial effects The ternary co-doped LaBr3 scintillation crystal for neutron detection provided in this invention has ultra-high gamma-ray energy resolution, through... 6 Doping with Li and other non-luminescent alkaline earth metal ions such as Sr enables the doped crystal to maintain ultra-high light yield and energy resolution while possessing neutron-gamma discrimination performance. Attached Figure Description

[0017] Figure 1 In Example 1 6Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 exist 137 A schematic diagram of energy resolution under Cs source irradiation; Figure 2 In Example 1 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 exist 252 Pulse shape discrimination diagram under Cf source irradiation; Figure 3 For Comparative Example 1, Ce 0.05 La 0.95 Br3 in 137 A schematic diagram of energy resolution under Cs source irradiation; Figure 4 For Comparative Example 2, Li 0.003 Ce 0.05 La 0.947 Br 2.994 exist 137 A schematic diagram of energy resolution under Cs source irradiation; Figure 5 For Comparative Example 3, Sr 0.007 Ce 0.05 La 0.943 Br 2.993 exist 137 A schematic diagram of energy resolution under Cs source irradiation; Figure 6 For Comparative Example 4, Li 0.003 Sr 0.003 Ce 0.05 La 0.944 Br 2.991 exist 137 A schematic diagram of the energy resolution under Cs source irradiation. Detailed Implementation

[0018] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0019] First, this invention provides a ternary co-doped LaBr3 scintillation crystal for neutron detection. The chemical composition of the ternary co-doped LaBr3 scintillation crystal for neutron detection can be A... x B y Ce z La 1-x-y-z Br 3-2x-y ; Wherein: A is a +1 valent alkali metal ion, preferably Li, 6 One of the following ions: Li, Na, K, Rb, and Cs, more preferably... 6 Li; B is a +2 valent alkaline earth metal ion, preferably one of Mg, Ca, Sr, and Ba ions, more preferably Sr; 0.00001≤x≤0.0025, 0.001≤y≤0.005, 0.03≤z≤0.08, preferably x=0.00005, y=0.003, z=0.05.

[0020] In the scintillation crystal provided by this invention, the introduction of alkaline earth metal ions such as Sr into the LaBr3 crystal can promote the generation of a slow scintillation decay component. 6 Alkali metal ions such as Li can enhance the neutron response capability of LaBr3 crystals, while the introduction of Ce ions can further improve the light yield of LaBr3 crystals. Through ternary co-doping, a ternary co-doped LaBr3 crystal is ultimately obtained that meets the requirements for neutron-gamma discrimination applications.

[0021] It should be noted that Ce, as a luminescent ion, exhibits low light yield when the doping concentration is too low, while excessive doping leads to Ce ion concentration quenching. A and B dopants, when present in insufficient amounts, have little effect on crystal energy regulation. Furthermore, doping with different radii and non-equivalent doping, or excessive doping concentrations, introduces excessive charge defects and severe lattice distortion, thus degrading crystal performance. The combined effect of A and B regulates crystal performance; A is a +1 valence alkali metal ion, and B is a +2 valence alkaline earth metal ion, which, after doping, endows the crystal with neutron detection capabilities.

[0022] In some embodiments, the morphology of the ternary co-doped LaBr3 scintillation crystal for neutron detection can be a bulk single crystal; preferably, when the ternary co-doped LaBr3 scintillation crystal for neutron detection is a bulk single crystal, the size of the ternary co-doped LaBr3 scintillation crystal for neutron detection in at least one dimension is not less than 20 mm.

[0023] In some embodiments, the scintillation decay time of the neutron detector ternary co-doped LaBr3 scintillation crystal can be 20 ns (fast component) to 35 ns (slow component).

[0024] In some embodiments, the light yield of the neutron detector ternary co-doped LaBr3 scintillation crystal can be 70,000 ± 2,000 ph. / MeV.

[0025] In some embodiments, the neutron detection ternary co-doped LaBr3 scintillation crystal can achieve an energy resolution of 2.24% at 662 keV.

[0026] The following is an exemplary description of the preparation method of the ternary co-doped LaBr3 scintillation crystal for neutron detection provided by the present invention. The preparation method may include the following steps: First, according to the chemical composition A of the ternary co-doped LaBr3 scintillation crystal for neutron detection... x B y Ce z La 1-x-y- z Br 3-2x-y The molar ratios of the elements in the mixture were weighed and mixed to obtain the raw material powder; then, the Bridgman method was used to grow the crystal to obtain the ternary co-doped LaBr3 scintillation crystal for neutron detection.

[0027] In some embodiments, the ABr powder, BBr2 powder, CeBr3 powder, and LaBr3 powder can all be in anhydrous state and have a purity ≥99.99%.

[0028] In some implementations, the Bridgman method may include the following steps: (1) Place the raw material powder in a quartz crucible with a capillary tip structure and evacuate it, then dry the material and seal the crucible. (2) Place the sealed quartz crucible vertically in the center of the crystal growth furnace, then raise the temperature of the crystal growth furnace to the melting point of the raw material powder and keep it warm so that the raw material powder is completely melted and fully mixed. (3) Adjust the height and position of the quartz crucible and the furnace temperature so that the temperature of the capillary tip structure of the quartz crucible is maintained within ±10℃ of the crystallization point of the ternary co-doped LaBr3 scintillation crystal for neutron detection. (4) The quartz crucible is lowered into the crystal growth furnace to grow the crystal. After the growth is completed, the temperature is lowered to obtain the neutron detection ternary co-doped LaBr3 scintillation crystal.

[0029] In some implementations, the vacuum level in step (1) can be 10. -2 ~10 -7 Pa; the drying temperature can be 200℃, and the time can be 4-6 hours.

[0030] In some implementations, in step (1), the size of the capillary tip structure is ≤3cm.

[0031] In some embodiments, in step (4), the longitudinal temperature gradient of the crystal growth furnace can be controlled to be 5 to 50 °C / cm, and the quartz crucible can be lowered at a rate of 0.01 to 10.0 mm / h.

[0032] In some embodiments, in step (4), the cooling method can be: the growth furnace is first cooled to 600-950°C at a rate of 5-10°C / h, kept at that temperature for 24 hours, and then cooled to room temperature at a rate of 10-15°C / h.

[0033] In this invention, an R6233-100 photomultiplier is used to collect samples. 137 Scintillation photons under Cs source irradiation. The neutron detector ternary co-doped LaBr3 crystal and the comparative example are... 137 Under Cs source irradiation, it can exhibit ultra-high energy resolution. The ternary co-doped LaBr3 crystal can simultaneously meet the requirements of ultra-high light yield, energy resolution and neutron-gamma discrimination, and has neutron detection capability.

[0034] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0035] Example 1

[0036] The neutron detector ternary co-doped LaBr3 scintillation crystal provided in this embodiment is a bulk single crystal with the following chemical formula: 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 The above-mentioned bulk single crystals were prepared using the Bridgman process, and the steps are as follows: (1) According to 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 The chemical element molar ratios in the sample were measured separately. Raw materials with a purity of 99.99% and a total weight of 120g were weighed. 6LiBr, SrBr2, CeBr3, and LaBr3; In a glove box filled with argon or nitrogen, the raw materials are mixed evenly and transferred into a quartz crucible with a capillary bottom of about 2 cm. After evacuating to a vacuum, the crucible is dried at 200°C for 4-6 hours. After drying, the crucible is sealed by welding. The sealed quartz crucible is then placed on a crucible rack and left to stand for 24 hours. The crucible is then inspected by contact testing with an electric spark gun vacuum detector. The appearance of glow discharge indicates that the inside of the crucible is in a vacuum environment, and the crucible is successfully sealed. (2) Place the quartz crucible after vacuum testing vertically in the center of the crystal growth furnace, heat the crystal growth furnace, and raise the temperature from room temperature to about 950°C in 8 hours. Keep it at that temperature for 24 hours to completely melt and mix the raw materials evenly. (3) Adjust the height and position of the crucible and the furnace temperature to reduce the temperature of the crucible capillary tip to about 750°C. (4) The quartz crucible is lowered relative to the furnace body at a speed of 0.5 mm / h. The crystal nucleates at the capillary tip of the crucible and gradually solidifies towards the tail end during the descent until the melt is completely crystallized. Then, the growth furnace is first cooled to 600℃ at a cooling rate of 5-10℃ / h, held at that temperature for 24 hours, and then cooled to room temperature at a cooling rate of 10-15℃ / h. Finally, the solidified halide scintillation crystal is taken out from the quartz crucible in a dry environment and processed to obtain the neutron detection ternary co-doped LaBr3 scintillation crystal.

[0037] Comparative Example 1

[0038] The transition metal halide provided in this comparative example is in the form of a bulk single crystal with the chemical formula Ce. 0.05 La 0.95 Br3, the preparation process of which is the same as in Example 1. The main difference is only: In step (1), according to the halide Ce 0.05 La 0.95 The molar ratios of each element in the chemical formula of Br3 were determined by weighing high-purity raw materials CeBr3 and LaBr3 with a purity of 99.99%.

[0039] Comparative Example 2

[0040] The transition metal halide provided in this comparative example is in the form of a bulk single crystal, and its chemical formula is Li. 0.003 Ce 0.05 La 0.947 Br 2.994 The preparation process is the same as in Example 1. The main difference is only: In step (1), according to the halide Li 0.003 Ce 0.05 La 0.947 Br 2.994The molar ratios of the elements in the chemical formulas were measured separately from high-purity raw materials LiBr, CeBr3, and LaBr3 with a purity of 99.99%.

[0041] Comparative Example 3

[0042] The transition metal halide provided in this comparative example is in the form of a bulk single crystal, with the chemical formula Sr. 0.007 Ce 0.05 La 0.943 Br 2.993 The preparation process is the same as in Example 1. The main difference is only: In step (1), according to the halide Sr 0.007 Ce 0.05 La 0.943 Br 2.993 The molar ratios of the elements in the chemical formulas were measured for high-purity raw materials SrBr2, CeBr3, and LaBr3 with a purity of 99.99%.

[0043] Comparative Example 4

[0044] The transition metal halide provided in this comparative example is in the form of a bulk single crystal, and its chemical formula is Li. 0.003 Sr 0.00 3Ce 0.05 La 0.944 Br 2.991 The preparation process is the same as in Example 1. The main difference is only: In step (1), according to the halide Li 0.003 Sr 0.003 Ce 0.05 La 0.944 Br 2.991 The molar ratios of each element in the chemical formula are respectively weighed for high-purity raw materials LiBr, SrBr2, CeBr3 and LaBr3 with a purity of 99.99%.

[0045] Figure 1 In Example 1 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 exist 137 A schematic diagram of the energy resolution under Cs source irradiation. The diagram shows that the energy resolution at 662 keV is 2.24%.

[0046] Figure 2 In Example 1 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969exist 252 Pulse shape discrimination diagram under Cf source irradiation. The diagram shows that the lower address corresponds to the gamma signal, and the higher address corresponds to the neutron signal.

[0047] Figure 3 For Comparative Example 1, Ce 0.05 La 0.95 Br3 in 137 A schematic diagram of the energy resolution under Cs source irradiation. The diagram shows that the energy resolution at 662 keV is 2.75%.

[0048] Figure 4 For Comparative Example 2, Li 0.003 Ce 0.05 La 0.947 Br 2.994 exist 137 A schematic diagram of the energy resolution under Cs source irradiation. The diagram shows that the energy resolution at 662 keV is 2.9%.

[0049] Figure 5 For Comparative Example 3, Sr 0.007 Ce 0.05 La 0.943 Br 2.993 exist 137 A schematic diagram of the energy resolution under Cs source irradiation. The diagram shows that the energy resolution at 662 keV is 2.9%.

[0050] Figure 6 For Comparative Example 4, Li 0.003 Sr 0.003 Ce 0.05 La 0.944 Br 2.991 exist 137 A schematic diagram of the energy resolution under Cs source irradiation. The diagram shows that the energy resolution at 662 keV is 2.85%.

[0051] Tests and comparisons show that Ce 0.05 La 0.95 Br3 possesses ultra-high energy resolution but lacks neutron response capability. 6 Li 0.00005 Sr 0.003 Ce 0.05 La 0.94695 Br 2.9969 It possesses both ultra-high energy resolution and neutron response capability.

[0052] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A ternary co-doped LaBr3 scintillation crystal for neutron detection, characterized in that, The chemical composition of the ternary co-doped LaBr3 scintillation crystal for neutron detection is A. x B y Ce z La 1-x-y-z Br 3-2x-y ;in: A is a +1 valent alkali metal ion, preferably Li, 6 One of the following ions: Li, Na, K, Rb, and Cs, more preferably... 6 Li; B is a +2 valent alkaline earth metal ion, preferably one of Mg, Ca, Sr, and Ba ions, more preferably Sr; 0.00001≤x≤0.0025, 0.001≤y≤0.005, 0.03≤z≤0.08, preferably x=0.00005, y=0.003, z=0.

05.

2. The ternary co-doped LaBr3 scintillation crystal for neutron detection according to claim 1, characterized in that, The ternary co-doped LaBr3 scintillation crystal for neutron detection is a bulk single crystal; preferably, when the ternary co-doped LaBr3 scintillation crystal for neutron detection is a bulk single crystal, the size of the ternary co-doped LaBr3 scintillation crystal for neutron detection is not less than 20 mm in at least one dimension.

3. The neutron detection ternary co-doped LaBr3 scintillation crystal according to claim 1 or 2, characterized in that, The scintillation decay time of the ternary co-doped LaBr3 scintillation crystal for neutron detection is 20 ns to 35 ns.

4. The ternary co-doped LaBr3 scintillation crystal for neutron detection according to any one of claims 1-3, characterized in that, The light yield of the ternary co-doped LaBr3 scintillation crystal for neutron detection is 70,000 ± 2,000 ph. / MeV.

5. The ternary co-doped LaBr3 scintillation crystal for neutron detection according to any one of claims 1-4, characterized in that, The neutron detection ternary co-doped LaBr3 scintillation crystal can achieve an energy resolution of 2.24% at 662 keV.

6. A method for preparing a ternary co-doped LaBr3 scintillation crystal for neutron detection according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: First, according to the chemical composition A of the ternary co-doped LaBr3 scintillation crystal for neutron detection... x B y Ce z La 1-x-y-z Br 3-2x-y The molar ratios of the elements in the mixture were weighed and mixed to obtain the raw material powder; then, the Bridgman method was used to grow the crystal to obtain the ternary co-doped LaBr3 scintillation crystal for neutron detection.

7. The preparation method according to claim 6, characterized in that, The ABr powder, BBr2 powder, CeBr3 powder, and LaBr3 powder are all anhydrous and have a purity of ≥99.99%.

8. The preparation method according to claim 6 or 7, characterized in that, The Bridgman method includes the following steps: (1) Place the raw material powder in a quartz crucible with a capillary tip structure and evacuate it, then dry the material and seal the crucible. (2) Place the sealed quartz crucible vertically in the center of the crystal growth furnace, then raise the temperature of the crystal growth furnace to the melting point of the raw material powder and keep it warm so that the raw material powder is completely melted and fully mixed. (3) Adjust the height and position of the quartz crucible and the furnace temperature so that the temperature of the capillary tip structure of the quartz crucible is maintained within ±10℃ of the crystallization point of the ternary co-doped LaBr3 scintillation crystal for neutron detection. (4) The quartz crucible is lowered into the crystal growth furnace to grow the crystal. After the growth is completed, the temperature is lowered to obtain the neutron detection ternary co-doped LaBr3 scintillation crystal.

9. The preparation method according to any one of claims 6-8, characterized in that, In step (1), the vacuum level is 10. -2 ~10 -7 Pa; The drying temperature is 200℃, and the time is 4-6 hours; The size of the capillary tip structure is ≤3cm.

10. The preparation method according to any one of claims 6-9, characterized in that, In step (4), the longitudinal temperature gradient of the crystal growth furnace is controlled to be 5-50℃ / cm, and the quartz crucible is lowered at a rate of 0.01-10.0mm / h. The cooling method is as follows: the growth furnace is first cooled to 600-950℃ at a rate of 5-10℃ / h, held at that temperature for 24 hours, and then cooled to room temperature at a rate of 10-15℃ / h.

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