An inorganic scintillation crystal performance testing system and method based on an adjustable pinhole collimator

Abstract

The application provides an inorganic scintillation crystal performance test system and method based on an adjustable pinhole collimator, and solves the problem that existing inorganic scintillation crystal performance test systems are mostly limited to the research of specific crystals and radioactive sources and are not universal in radiation detection macroscopic applications. The system comprises a base, a radioactive source, a radioactive source limiting unit, a collimation assembly, a collimation adjusting unit, a detector position adjusting unit and a rear-end test unit. Through the use of the system core structure, the collimation assembly composed of multiple pinhole collimators, the radioactive source radiation is accurately injected into the scintillation crystal at a certain angle, reducing the interference caused by scattering and environmental background, and combining standard scintillation crystals and standard radioactive sources of the same kind, the activity and energy consistency of the radioactive source is calibrated with high precision and sensitivity, and then flexible matching of various types of radioactive sources is realized, and the objective conditions of the numerous radiation isotopes in the application environment are restored as much as possible.

Description

Technical Field

[0001] This invention belongs to the field of nuclear radiation detection technology, specifically relating to an inorganic scintillation crystal performance testing system and method based on an adjustable pinhole collimator. Background Technology

[0002] Since the 1960s, the space industry has developed rapidly. However, the diverse types of radiation and high radiation doses in the space environment have made the research and application of radiation identification and radiation tolerance in radiation detection extremely urgent and crucial. Scintillators, due to their mechanism of generating photons upon exposure to radiation, can be applied to radiation detection and identification. Among them, inorganic scintillation crystals have gradually attracted increasing attention and research due to their excellent scintillation properties, such as high light output, high energy resolution, and rapid decay. Given the energy differences and high doses of radiation in various radiation detection application environments, while small-sized scintillation crystals offer high detection accuracy, their efficiency is insufficient to meet practical needs. Therefore, the demand for large-sized scintillation crystals is becoming increasingly strong. For large-sized scintillation crystals, the uniformity of scintillation properties, such as light output, has a decisive impact on their detection performance. Therefore, the construction of a scintillation performance uniformity testing system, based on equipment such as a pulse height spectroscopy testing system and a digital oscilloscope, is of great significance for characterizing these properties.

[0003] Existing systems for testing the uniformity of scintillation performance of large-size scintillation crystals typically use a single pinhole collimator as the core structure. Under the condition that the radiation source and the sample under test are kept at a certain distance, the radiation rays are emitted through the pinhole whose diameter and length are determined by the collimator and reach the detector structure. Then, after a series of signal conversions, electronic signals are output, which are recorded by the back-end test data collection equipment and analyzed to obtain the corresponding performance parameters.

[0004] Reference 1, “Sturm BW, Cherepy NJ, Drury OB, et al. Evaluation of largevolume SrI₂(Eu) scintillator detectors[C] / / IEEE Nuclear Science Symposuim & Medical Imaging Conference. IEEE, 2010: 1607-1611,” reports an experimental method based on a collimated gamma-ray source, using a pinhole-shaped collimator formed by a slit in lead bricks to detect gamma rays. 137 Cs gamma rays were collimated, and the light collection uniformity at different locations of the crystal was scanned. The study found that the light collection uniformity of the encapsulated SrI2(Eu) crystal was significantly improved, and the energy resolution was improved from 5.01% to 3.22%, providing an important basis for the optimized design of large scintillator detectors.

[0005] Literature 2 "Wu Y, Lindsey AC, Zhuravleva M, et al. Growth of inch-sizedKCa 0.8 Sr 0.2 I3: Eu 2+ The paper "Scintillating crystals and high performance for gamma-ray detection[J]. CrystEngComm, 2016, 18(39): 7435-7440" reports an experimental method based on a collimated gamma-ray source, which also uses a pinhole collimator formed by a slit in lead bricks to detect gamma-rays. 137 Collimation of Cs γ rays and systematic study of KCa 0.8 Sr 0.2 I3:Eu 2+ Light collection in crystals and the generation of inhomogeneities. Studies have found that the tail end of the crystal is affected by Eu. 2+ Uneven distribution leads to degraded energy resolution, while the seed end performs better, providing key data to reveal the impact of doping distribution on performance.

[0006] Reference 3, “Large-size CsI:Na single crystals for future high energy physics experiment,” reports an experimental method based on a collimated gamma-ray source. This method utilizes a fully enclosed pinhole collimator that leaves only the pinhole visible. 137 The axial homogeneity of CsI:Na crystals was evaluated by collimation with Cs gamma rays. The results show that the energy resolution of the 51 mm × 51 mm × 152 mm crystal is stable at 6.5%, and the peak position is not affected by the irradiation position, verifying its excellent performance consistency and laying the foundation for the application of large-size crystals in high-energy physics experiments.

[0007] All of the above studies used a self-built single pinhole collimator and precision collimation technology to achieve local scanning characterization of the internal properties of scintillation crystals, providing a key experimental method for revealing the non-uniformity of scintillation crystals.

[0008] However, current scintillation crystal performance uniformity characterization systems, which use single-pinhole collimators as the core structure of the testing system, have many limitations. Due to the fixed aperture and length parameters of the single-pinhole collimator, its attenuation effect on radiation rays is also fixed. Therefore, to achieve the optimal balance between testing efficiency and accuracy, the radiation sources used in the tests are mostly standard radiation sources with fixed activities, making it difficult to accurately reflect the complex composition of radiation isotopes in the application environment. Furthermore, scintillation crystals of different sizes will exhibit significant differences in testing results under these conditions, failing to comprehensively characterize their performance uniformity across various application environments. In conclusion, current scintillation crystal performance testing systems largely remain at the research level under specific crystal and radiation source conditions, lacking universality for macroscopic applications in radiation detection.

[0009] Therefore, it is necessary to design an inorganic scintillation crystal performance testing system that is universally applicable in macroscopic applications. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing inorganic scintillation crystal performance testing systems, which are mostly limited to research on specific crystal and radiation source conditions and lack universality in macroscopic radiation detection applications. This invention provides an inorganic scintillation crystal performance testing system and method based on an adjustable pinhole collimator.

[0011] To achieve the above objectives, the technical solution provided by this invention is:

[0012] An inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator is characterized by comprising a base, a radiation source, a radiation source limiting unit, a collimation assembly, a collimation adjustment unit, a detector position adjustment unit, and a back-end testing unit.

[0013] Definition: One side of the base is the front end, and the opposite side is the rear end;

[0014] From front end to rear end, the base is fixed and supports the detector position adjustment unit, the collimation adjustment unit, and the radiation source limiting unit;

[0015] The radioactive source limiting unit includes a support rod, a connecting rod, and a radioactive source receiving module; wherein, the support rod is vertically installed on the base, and the connecting rod is vertically installed on the support rod at one end, and the radioactive source receiving module is detachably installed at the other end; the radioactive source receiving module is used to accommodate the radioactive source, and its front end face is provided with an opening, the center of which is located on the same horizontal line as the center of the radioactive source, and the size of the opening is smaller than the size of the radioactive source;

[0016] The collimation adjustment unit includes a support frame and an adjustment rod; wherein, the support frame is fixed on the base; the adjustment rod is horizontally installed on the support frame from front to back, and its position is adjustable, but it will not rotate relative to the support frame after installation to ensure stability during detection.

[0017] The collimation assembly includes multiple pinhole collimators (multiple pinhole collimators are used in this invention, allowing the number of pinhole collimators to be selected according to the needs of different application scenarios, thereby adjusting the total length of the collimation assembly); multiple pinhole collimators are coaxially spaced on the adjusting rod and will not rotate relative to the adjusting rod, with the interval between adjacent pinhole collimators less than 2mm to ensure that the intensity scattering of radiation rays passing through the area between adjacent pinhole collimators is minimized; each pinhole collimator has a coaxial mounting hole, and in addition, 3-5 collimation holes of different diameters are evenly distributed on the pinhole collimator (the different diameters are designed to meet the different requirements for radiation ray attenuation in different application scenarios, making the entire device more universal), and the center of each collimation hole is located on the same circle with the center of the pinhole collimator itself as the center. On the circumference of the center; the total length L of the collimation component in the horizontal direction and the two thicknesses in the vertical direction of the collimation hole can both satisfy the requirement that the ineffective radiation rays (i.e., unwanted radiation rays, also known as attenuated rays) can achieve an attenuation of more than 99%; the two thicknesses are respectively the distance p between the side of the collimation hole closest to the edge of the pinhole collimator and the edge of the pinhole collimator, and the distance h between the side of the collimation hole closest to the edge of the mounting hole and the edge of the mounting hole. Specifically, for example, for a collimation hole located above the mounting hole, its two thicknesses in the vertical direction are respectively the distance p between the upper edge of the collimation hole and the upper edge of the pinhole collimator, and the distance h between the lower edge of the collimation hole and the upper edge of the mounting hole; among each pinhole collimator, the distance between the center of the collimation hole and the center of the pinhole collimator itself is equal, and collimation holes with the same diameter are located in the same orientation. With the adjustment of the adjusting rod, the collimation hole on each pinhole collimator can be aligned with the center of the radiation source on the same horizontal line; thus, the center of the collimation hole of each pinhole collimator in the same orientation can also be aligned with the center of the radiation source on the same horizontal line.

[0018] The detector position adjustment unit includes a lifting assembly and a detector limiting assembly; wherein, the detector limiting assembly is used to limit and accommodate the inorganic scintillation crystal detector, and its overall design is light-shielding and the material is magnetic shielding material; the lifting assembly is used to stably support the detector limiting assembly and adjust the height of the detector limiting assembly so that different height regions of the crystal in the inorganic scintillation crystal detector are on the same horizontal line as the center of the radiation source.

[0019] The back-end test unit is connected to the inorganic scintillation crystal detector via an electrical signal transmission line (such as a BNC line) and is used to test the performance of the inorganic scintillation crystal detector. Different equipment is used depending on the test parameters. For example, a pulse height spectrum test device is used to measure the light yield and energy resolution, and a digital oscilloscope is used to measure the decay time.

[0020] Furthermore, the collimation component determines the key parameters according to the following method:

[0021] ① Based on the requirement that the attenuation flux of ineffective radiation rays reaches more than 99%, the attenuation coefficient formula is used:

[0022]

[0023] Where I is the total flux of the ray after passing through the collimation component;

[0024] I0 is the total flux of the ray before it enters the collimation component;

[0025] μ is the linear attenuation coefficient of the collimation component material under the action of radiation rays of a specific energy;

[0026] x is the total length of the ray affected by attenuation, that is, the total length L of the collimation component in the horizontal direction;

[0027] Based on this, the formula for calculating the attenuation percentage (D) of the attenuated ray flux is obtained:

[0028] D = 1 - (I / I0)

[0029] Through calculation, the total length of the collimation component in the horizontal direction and the thicknesses p and h at two points in the vertical direction of the largest collimation hole on the pinhole collimator were determined.

[0030] ② Determine the diameter and length of the collimation hole on the pinhole collimator.

[0031] First, the limitations on the aperture and length are defined as follows:

[0032] The aperture is greater than or equal to 0.1 mm and less than or equal to one-third of the vertical length of the irradiated cross section of the crystal in the inorganic scintillation crystal detector under test;

[0033] The sum of the lengths of the collimating holes on all pinhole collimators is equal to the total length of the collimating assembly in the horizontal direction;

[0034] Secondly, to achieve precise control of the flux after attenuation, the collimation orifice diameter and length used in each test are specifically determined using the geometric solid angle formula:

[0035]

[0036] Among them, Atotal The percentage of radiation flux retained after passing through the collimator, i.e., the percentage of effective radiation rays;

[0037] d is the diameter of the collimation hole of the pinhole collimator;

[0038] L is the sum of the lengths of the collimating holes of the pinhole collimator, i.e., the total length;

[0039] Furthermore, the other end of the connecting rod has a snap-fit ​​structure, which allows for the free installation and removal of the radiation source housing module;

[0040] The upper surface of the radioactive source receiving module is provided with a placement hole (for easy placement of the radioactive source), and a matching cover is also provided;

[0041] The opening is a square hole, the side length of which is smaller than the diameter of the radiation source, with a difference of 1-5 mm.

[0042] Furthermore, the support frame includes four first fixing rods and two second fixing rods;

[0043] All four first fixing rods are vertically installed on the base and are arranged symmetrically in pairs (i.e., axially and radially symmetrically distributed on the horizontal plane), forming a cubic frame with a defined length, width and height.

[0044] Two second fixing rods are respectively installed between the two first fixing rods at the front end and between the two first fixing rods at the rear end of the cube frame. Each of the two second fixing rods has a square opening in the middle for inserting and removing the adjusting rod. To ensure that the two second fixing rods are securely installed in the cube frame, many existing technologies can be used for connection. This application provides a method in which each first fixing rod has a through hole with internal threads. After the second fixing rod is inserted into the two first fixing rods located on the same side, the two ends of the second fixing rod can be fixed with screws to maintain overall stability.

[0045] The adjusting rod is a square rod that can be fitted with the square opening in the middle of the second fixed rod (the difference between the side length of the adjusting rod and the side length of the square opening does not exceed 5mm), ensuring that it can be smoothly inserted and removed before and after use; and the material of the adjusting rod must ensure that it has both good load-bearing capacity and sliding properties.

[0046] Furthermore, the pinhole collimator is a cylindrical radiation attenuator (depending on the type of radiation source used in the test, a material with strong attenuation properties, such as lead, is used). It has a square mounting hole coaxially arranged at its center to fit the adjusting rod, allowing for clearance fitting (the side length of the square mounting hole differs from the side length of the adjusting rod by no more than 5mm). With the center of the pinhole collimator as the origin, four collimation holes of varying diameters are formed in four directions on both positive and negative sides (each collimation hole has a different diameter, but the distance between the center of the hole and the center of the pinhole collimator is equal). The thickness of each pinhole collimator can be equal or unequal, adjusted according to actual needs and considering the ease of manufacturing.

[0047] Furthermore, the lifting assembly is a scissor-type lifting platform, the surface of which is covered with anti-slip material to ensure the horizontal orientation stability of the detector limiting assembly and the inorganic scintillation crystal detector, with an adjustment accuracy not exceeding 5μm;

[0048] The detector limiting assembly includes a limiting module and a limiting cover. The limiting module has internal space to fix and limit the inorganic scintillation crystal detector, ensuring stability and accuracy during testing. A through-hole is provided on its side for easy connection between the inorganic scintillation crystal detector and the downstream testing unit. The limiting cover is removable before and after use to facilitate the removal and placement of the inorganic scintillation crystal detector from the limiting module. After reinstallation, the gap between the limiting cover and the limiting module is further enhanced by using black light-shielding material. The entire detector limiting assembly uses a material that simultaneously provides light and magnetic shielding. Combined with the black light-shielding material used in the aforementioned gap, this ensures shielding against light and magnetic fields while reducing attenuation of incoming radiation. The diameter of the internal space of the limiting module differs from the maximum external diameter of the inorganic scintillation crystal detector by no more than 5mm; the diameter of the upper opening differs from the diameter of the limiting cover by no more than 5mm; and the diameter of the through-hole on its side differs from the maximum diameter of the interface for the electrical signal transmission line by no more than 5mm.

[0049] Furthermore, the collimator adjustment unit also includes a storage component for accommodating the pinhole collimator;

[0050] The storage component is located on the base below the adjustment rod. It has a semi-circular groove with a diameter larger than the overall diameter of the pinhole collimator, and the difference is not less than 10mm.

[0051] Furthermore, the radioactive source is... 137 Cs or 60 High-energy gamma-ray sources primarily composed of radioactive elements or isotopes such as Co. In this invention, the default shape of the radioactive source is circular; however, in practical applications, different shapes and types of radioactive sources can be used depending on the specific circumstances. For this type of radioactive source, a cylindrical lead sheet can be used as the pinhole collimator.

[0052] The aforementioned inorganic scintillation crystal detector specifically includes a scintillation crystal, a photomultiplier tube, and a packaging shell. The scintillation crystal and photomultiplier tube are optically coupled via a light transmission coupler to enhance the uniformity of light transport. The outer shell of the packaging shell is composed of heat-resistant and shock-resistant material, which also provides shielding against external signals and light. Furthermore, its size is highly matched to the scintillation crystal and photomultiplier tube, with a spacing on the order of approximately 1 mm, thus achieving a limiting and fixing effect on both. Scintillation crystals are mainly divided into standard scintillation crystals and scintillation crystals under test. The former has known performance parameters such as light yield and energy resolution and should be the same type, size, and shape as the latter.

[0053] Meanwhile, the present invention also provides a testing method for the inorganic scintillation crystal performance testing system based on the above-mentioned adjustable pinhole collimator, which is characterized by including the following steps:

[0054] Step 1: Install the radiation source

[0055] Place the radioactive source in the radioactive source receiving module and install the radioactive source receiving module at the other end of the connecting rod; that is, after selecting the radioactive source required for testing, open the cover on the upper surface of the radioactive source receiving module, put the radioactive source into the module through the placement hole (ensure that the center of the radioactive source and the center of the opening are on the same horizontal line), then close the cover, and then snap the radioactive source receiving module into the buckle structure of the connecting rod to complete the installation and fixation of the radioactive source;

[0056] Step 2: Install the collimation components

[0057] Install each pinhole collimator of the collimation assembly sequentially onto the adjusting rod. Then, horizontally install the adjusting rod onto the support frame from front to back and fix it in place. Ensure that the collimation hole diameters corresponding to each pinhole collimator are not only the same, but also that the center of the upper collimation hole (i.e., the hole center) is on the same horizontal line as the center of the radiation source. In specific installation, one end of the adjusting rod can be installed on the second fixing rod at one end of the support frame. Then, insert each pinhole collimator into the adjusting rod. Finally, install the other end of the adjusting rod with the second fixing rod at the other end of the support frame, so that the center of the upper collimation hole of the pinhole collimator is on the same horizontal line as the center of the radiation source.

[0058] Step 3: Install the inorganic scintillation crystal detector to be tested

[0059] The inorganic scintillation crystal detector to be tested is placed in the detector limiting assembly, and the detector limiting assembly is placed stably on the upper surface of the lifting assembly. By adjusting the height, the initial height area of ​​the crystal in the inorganic scintillation crystal detector to be tested is aligned with the center of the radiation source and the center of the collimation hole above.

[0060] Step 4: Test the crystal performance in the inorganic scintillation crystal detector under test.

[0061] Connect the inorganic scintillation crystal detector under test to the back-end test unit, and set the prerequisite parameters according to the type of test performance (for example, the prerequisite parameters for testing optical yield and energy resolution are operating voltage and main amplifier gain; the prerequisite parameter for testing decay time is operating voltage. In general, the prerequisite parameters to be adjusted are different depending on the back-end test unit). After completing the settings, start the test and collect the test results.

[0062] After completing the initial height area test, adjust the lifting assembly to change the height area of ​​the crystal in the inorganic scintillation crystal detector under test, and continue testing. Repeat this process. After completing the current angle test, rotate the detector limiting assembly as needed to perform the next set of tests. Continue this process until all tests are completed under the current collimation assembly parameters, thus completing the scintillation crystal performance uniformity test. Specifically:

[0063] Connect the back-end test unit, set the operating voltage, main amplifier gain and other prerequisite parameters. After setting, start the test and collect test results with a certain face of the detector limiting component as the initial angle (0°). After completing the initial height area test, adjust the lifting component and change the height area of ​​the crystal in the inorganic scintillation crystal detector under test according to a specific step size (the step size can be determined according to actual needs, such as 5cm) and continue the test until the bottom area of ​​the crystal is reached and the initial angle test is completed. Then rotate the detector limiting component clockwise by 90° (this is a specific angle, and the rotation angle can be determined according to actual needs) to perform the next set of tests. Repeat this process until the initial angle is rotated back, which completes all tests under the current collimation component parameter conditions (determine the aperture, aperture length, total length in the horizontal direction, and thickness at two points in the vertical direction).

[0064] If additional testing is required, a second test can be conducted by changing the thickness of the collimator and the diameter of the upper collimation hole, depending on the different requirements for radiation flux, while keeping the overall process unchanged.

[0065] In practical applications, standard radioactive sources with known activity are usually used for testing. However, the possibility of using radioactive sources with unknown activity cannot be ruled out. Therefore, this invention also provides a method for calibrating radioactive sources using the aforementioned inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator. (If crystal performance uniformity is tested using a standard radioactive source on a crystal with unknown parameters, then calibration, under this premise, involves simultaneously testing a standard scintillation crystal with a standard radioactive source and a radioactive source with activity to be calibrated, and then comparing the results to achieve reverse calibration of the radioactive source to be calibrated.) Its special feature lies in the following steps:

[0066] S1: Install standard radioactive sources

[0067] A standard radioactive source with a known activity of A0 is placed in the radioactive source housing module, and the radioactive source housing module is installed at the other end of the connecting rod;

[0068] S2: Install the alignment components

[0069] Install each pinhole collimator of the collimation assembly onto the adjusting rod in sequence. Then, install the adjusting rod horizontally onto the support frame from front to back and fix it in place. Ensure that the collimation hole diameters corresponding to each pinhole collimator are not only the same, but also that the center of the collimation hole located above is on the same horizontal straight line as the center of the radiation source.

[0070] S3: Install an inorganic scintillation crystal detector

[0071] The inorganic scintillation crystal detector containing the standard scintillation crystal is placed in the detector limiting assembly, and the detector limiting assembly is placed stably on the upper surface of the lifting assembly. By adjusting the height, the initial height area of ​​the crystal in the inorganic scintillation crystal detector for testing is aligned with the center of the radiation source and the center of the collimation hole above.

[0072] S4: Testing the standard radioactive source

[0073] Connect the inorganic scintillation crystal detector to the pulse height spectroscopy test equipment and ensure a light-proof environment; set the prerequisite parameters of the pulse height spectroscopy test equipment (including voltage, gain, molding time, and test time), and after completing the settings, start the test and collect the full-energy peak address Ch0 and count rate R0.

[0074] S5: Replacement and Testing of Radioactive Sources to be Calibrated

[0075] After completing S4, remove the voltage and turn off the pulse height spectroscopy test equipment. Replace the standard radioactive source in the radioactive source containment module with the radioactive source to be calibrated. Then repeat the test process in S4 and collect the full-energy peak address Ch1 and count rate R1. After completing the test, remove the voltage and turn off the pulse height spectroscopy test equipment.

[0076] S6: Radioactive source calibration (mainly calibrating activity and energy consistency)

[0077] Comparing the differences in the results for the total peak address and count rate obtained in S4 and S5, the following calibration calculations were performed on the radioactive source to be calibrated:

[0078] ① Energy consistency: Calculated using the following formula

[0079] Energy uniformity=(Ch1-Ch0) / Ch0

[0080] If the value is ≤1%, the energy of the radioactive source to be calibrated is considered to be the same as that of the standard radioactive source.

[0081] ② The activity A1 of the radioactive source to be calibrated: calculated using the following formula

[0082] A1 = A0 × (R1 / R0)

[0083] The entire process of radioactive source calibration is now complete.

[0084] Important: When not in use, the back-end test unit must be turned off and the voltage divider at the end of the detector must be disconnected.

[0085] The principle of this invention:

[0086] This invention achieves dual-factor control of radiation flux and intensity by adjusting the total length L of the collimation component in the horizontal direction, the thickness of the two points of the collimation hole in the vertical direction, and the aperture of the collimation hole. Combined with the integrated structure at the front end of the system and various testing equipment at the back end of the system, it accurately and reliably reproduces the test results of the uniformity of inorganic scintillation crystals of different types and sizes in real radiation environments in various application fields.

[0087] The total horizontal length of the collimation component, the thickness of the two vertical points of the collimation hole located above, and the aperture of the collimator can all be flexibly adjusted according to actual application requirements. In conjunction with other components, precise axial and radial tests can be performed on different crystals under different radiation conditions to obtain more realistic scintillation performance uniformity. This provides more accurate data support for evaluating its performance in practical applications, realizing the construction of a comprehensive and reliable scintillation crystal uniformity characterization test system.

[0088] Advantages of this invention:

[0089] This invention proposes a performance testing system for inorganic scintillation crystals based on an adjustable pinhole collimator structure, and a corresponding testing method based on this system. Compared with traditional technologies, the main advantages of this invention are as follows:

[0090] 1. This invention utilizes a collimation component, composed of multiple pinhole collimators, as the core structure of the system. This allows the radiation from the radioactive source to be precisely directed into the scintillation crystal at a defined angle, reducing scattering and interference from the background radiation. By combining a standard scintillation crystal with a standard radioactive source of the same type, it achieves high-precision and sensitivity calibration of the activity and energy consistency of the radioactive source. This enables flexible matching of various types of radioactive sources and restores the objective conditions of a wide variety of radioactive isotopes in the application environment as much as possible.

[0091] 2. By adjusting the total length L of the collimation component in the horizontal direction, the thickness of the two collimation holes in the vertical direction, and the aperture of the collimation hole, this invention can achieve complex control over the intensity of radiation rays and flux attenuation. At the same time, by using multiple types of radiation sources calibrated in the pre-process, it provides conditions that are closer to the real scene for testing, enabling precise and rapid testing of the uniformity of scintillation crystals of different types, sizes, and shapes.

[0092] 3. This invention, through multiple flexible selections or adjustments of components such as the radiation source, scintillation crystal, collimation component, and lifting component in the system, deepens the application scope and versatility of existing one-dimensional or two-dimensional crystal homogeneity characterization work. It can achieve accurate characterization of the three-dimensional spatial performance distribution of the measured scintillation crystal, which has extremely important guiding significance for the application of selective cutting of large-size scintillation crystals to obtain high-quality small-size scintillation crystals.

[0093] In summary, this invention comprehensively expands the breadth and depth of applications for scintillation crystal uniformity testing and characterization, achieving a test effect that maintains dynamic equilibrium even when components such as crystals, radiation sources, and collimators change in various conditions such as type, size, shape, and thickness. Furthermore, it provides, for example, the idea of ​​guiding selective processing to produce high-quality, small-sized crystals through the characterization of crystal three-dimensional performance uniformity, broadening the application path of testing systems based on pinhole collimators and giving them greater application prospects and promotion potential. Attached Figure Description

[0094] Figure 1 This is a planar schematic diagram of an inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator.

[0095] Figure 2 This is a three-dimensional structural diagram of a single pinhole collimator;

[0096] Figure 3 This is a schematic diagram of the emission path of attenuated rays in the material region of the collimation component;

[0097] Figure 4 This is a schematic diagram of the emission path of the radiation rays in the aperture region of the collimation component;

[0098] Figure 5 This is a schematic diagram of the points used for testing axial non-uniformity of crystals in the embodiments listed in this invention;

[0099] Figure 6 This is a schematic diagram of the points used for testing the radial inhomogeneity of the crystal in the embodiments listed in this invention;

[0100] Figure 7These are the corresponding pulse height spectrum images of the same test point under two different collimator length and aperture settings in Example 1;

[0101] Figure 8 This is a real photograph of a high-quality, small-sized cylindrical crystal with excellent performance uniformity obtained by cutting and processing from the tested crystal after following the axial and radial performance uniformity test results in Example 1.

[0102] Figure 9 These are the corresponding pulse height spectrum images of the same test point under two different collimator length and aperture settings in Example 2;

[0103] Figure 10 This is a real photograph of a high-quality, small-sized cylindrical crystal with excellent performance uniformity obtained by cutting and processing from the tested crystal after being guided by the axial and radial performance uniformity test results in Example 2.

[0104] Figure 11 It is via Example 3 137 Cs standard source and to be calibrated 137 The corresponding pulse height spectrum image at the same test point (center) under Cs source radiation conditions. Detailed Implementation

[0105] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0106] like Figure 1 As shown, an inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator includes a base, a high-energy gamma radiation source, a radiation source limiting unit, a collimation assembly, a collimation adjustment unit, a detector position adjustment unit, and a rear-end testing unit. Definition: One side of the base is the front end, and the opposite side is the rear end; from the front end to the rear end, the detector position adjustment unit, the collimation adjustment unit, and the radiation source limiting unit are fixed and supported on the base.

[0107] The radioactive source limiting unit includes a support rod, a connecting rod, and a radioactive source receiving module. The support rod is vertically mounted on the base, and the connecting rod is vertically mounted on the support rod at one end, while the other end is detachably mounted to the radioactive source receiving module via a snap-fit ​​structure. The radioactive source receiving module is used to house the radioactive source, and its front end face has a square opening. The center of this opening is on the same horizontal line as the center of the radioactive source, and the side length of the opening is smaller than the diameter of the radioactive source. The upper surface of the radioactive source receiving module has a placement hole, which is matched with a cover.

[0108] The collimation adjustment unit includes a support frame, an adjustment rod, and a storage assembly for the pinhole collimator. The support frame includes four first fixed rods and two second fixed rods. The four first fixed rods are vertically mounted on the base and arranged symmetrically in pairs to form a cubic frame. The two second fixed rods are respectively installed between the two first fixed rods at the front end and between the two first fixed rods at the rear end of the cubic frame. Each of the two second fixed rods has a square opening in the middle for inserting and removing the adjustment rod. The adjustment rod is a square rod, horizontally mounted on the support frame from front to back, and can be fitted with the square opening in the middle of the second fixed rod. Its position is adjustable, but it will not rotate relative to the support frame after installation. The storage assembly is located on the base below the adjustment rod and has a semi-circular groove with a diameter larger than that of the pinhole collimator.

[0109] The collimation assembly includes multiple pinhole collimators; these pinhole collimators are coaxially spaced on the adjusting rod and do not rotate relative to it, with adjacent pinhole collimators spaced less than 2 mm apart; the pinhole collimators are cylindrical radiation attenuators (e.g., for radiation sources). 137 In Cs, the pinhole collimator is a cylindrical lead sheet. It has a square mounting hole coaxially arranged at its center to match the adjusting rod, allowing for clearance fit with the adjusting rod. Using the center of the pinhole collimator as the origin as the coordinate axis, four collimation holes of different diameters are opened on it in four directions on the positive and negative sides. The center of each collimation hole is located on the same circumference with the center of the pinhole collimator as the center. The total length L of the collimation assembly in the horizontal direction and the two thicknesses in the vertical direction of the collimation holes can both ensure that the attenuation flux of the ineffective radiation rays reaches more than 99%. The two thicknesses are the distance p between the side of the collimation hole closest to the edge of the pinhole collimator and the edge of the pinhole collimator, and the distance h between the side of the collimation hole closest to the edge of the mounting hole and the edge of the mounting hole. The detector position adjustment unit includes a lifting assembly and a detector limiting assembly. The detector limiting assembly is used to limit and accommodate the inorganic scintillation crystal detector. It includes a limiting module and a limiting cover. The whole assembly is designed to block light and is made of magnetic shielding material (in this embodiment, black polytetrafluoroethylene and black electrical tape are used together to achieve both light blocking and magnetic shielding). The lifting assembly is used to stably support the detector limiting assembly and adjust the height of the detector limiting assembly so that different height areas of the crystal in the inorganic scintillation crystal detector are on the same horizontal line as the center of the radiation source. The lifting assembly is a scissor-type lifting platform. The surface of the platform is covered with anti-slip material, and its adjustment accuracy does not exceed 5μm.

[0110] The back-end test unit is connected to the inorganic scintillation crystal detector and is used to test the performance of the inorganic scintillation crystal detector.

[0111] The collimation component in the above test system determines its key parameters using the following method:

[0112] ① Based on the requirement that the attenuation flux of ineffective radiation rays reaches more than 99%, the attenuation coefficient formula is used:

[0113]

[0114] Where I is the total flux of the ray after passing through the collimation component;

[0115] I0 is the total flux of the ray before it enters the collimation component;

[0116] μ is the linear attenuation coefficient of the collimation component material under the action of radiation rays of a specific energy;

[0117] x is the total length of the ray affected by attenuation, that is, the total length L of the collimation component in the horizontal direction;

[0118] Based on this, the formula for calculating the attenuation percentage (D) of the attenuated ray flux is obtained:

[0119] D = 1 - (I / I0)

[0120] Through calculation, the total length of the collimation component in the horizontal direction and the thicknesses p and h at two points in the vertical direction of the largest collimation hole on the pinhole collimator were determined.

[0121] ② Determine the diameter and length of the collimation hole on the pinhole collimator.

[0122] First, the limitations on the aperture and length are defined as follows:

[0123] The aperture is greater than or equal to 0.1 mm and less than or equal to one-third of the vertical length of the irradiated cross section of the crystal in the inorganic scintillation crystal detector under test;

[0124] The sum of the lengths of the collimating holes on all pinhole collimators is equal to the total length of the collimating assembly in the horizontal direction;

[0125] Secondly, to achieve precise control of the flux after attenuation, the collimation orifice diameter and length used in each test are specifically determined using the geometric solid angle formula:

[0126]

[0127] Among them, A total The percentage of radiation flux retained after passing through the collimator, i.e., the percentage of effective radiation rays;

[0128] d is the diameter of the collimation hole of the pinhole collimator;

[0129] L is the sum of the lengths of the collimating holes of the pinhole collimator, i.e., the total length;

[0130] Here are some supplementary explanations for the two methods:

[0131] ① The total horizontal length L of the collimation assembly and the two thicknesses p and h in the vertical direction of each collimation aperture mainly reflect the attenuation effect on "ineffective radiation rays," because the key point of the pinhole collimator is that after use, only the total flux of radiation rays passing through the collimation aperture needs to be considered. Taking a complete collimation assembly composed of multiple pinhole collimators with the same aperture length and thickness (t) as an example, such as... Figure 2 As shown, at this point, only the incident rays from the upper edge of the collimating hole 442 to the upper edge of the collimator and from the lower edge of the collimating hole 442 to the upper edge of the central mounting hole are considered. The exit path of the attenuated ray within the corresponding collimator material region is as follows. Figure 3 As shown (in fact, the attenuation of radiation rays in the collimator region outside the collimator aperture can be considered as a case occurring on the p1-nt or h1-nt two-dimensional plane, rotated 360°), from Figure 3 It is not difficult to see that the path of the attenuated ray within the collimator has three extreme cases, with lengths of nt, p1, and l, respectively. max According to the Pythagorean theorem, l max =((nt)^ 2 +(p1)^ 2 )^ 0.5 For attenuated rays, the shortest possible length is either nt or p1. Therefore, based on the attenuation coefficient formula, the total length nt of the collimation component in the horizontal direction and the thicknesses p and h at the two points in the vertical direction of the collimation aperture must satisfy exp(-μ(nt)) < 1%, exp(-μ(p)) < 1%, and exp(-μ(h)) < 1%.

[0132] At this point, the total horizontal length of the collimation assembly involves the number of collimators and the length of a single collimator hole. The determination of the hole length value needs to be combined with the determination of the hole diameter (both need to be adjusted together to achieve the expected throughput, which will be explained in detail in Part ②). After determining the hole length, the range of values ​​for n is calculated based on the total limit of exp(-μ(nt)) < 1%, and the smallest positive integer is taken (if the hole diameters of each collimator are not equal, then nt in the formula can be converted to L for calculation). Regarding the two thicknesses of the collimator in the vertical direction (the minimum distance p between the edge of each opening and the edge of the nearest collimator and the distance h between the edge of each opening and the edge of the nearest center mounting hole), it is important to clarify that the collimator used in this invention has multiple collimation holes, and the sizes of different collimation holes are different. However, the center of each collimation hole is located on the circumference with the center of the collimator itself as the center. The collimator itself is circular. Therefore, the larger the radius of the collimation hole, the smaller the minimum distance p between its edge and the edge of the nearest collimator and the minimum distance h between the edge of the nearest center mounting hole. Under these conditions, the aperture d is at its maximum (d max The collimation aperture has the smallest p and h values ​​(p). min / h minIn other words, if exp(-μ(p) is satisfied min ))<1% / exp(-μ(h min If the thickness of each collimating hole in the vertical direction is less than 1%, then the thickness of each collimating hole in the vertical direction also meets the flux attenuation requirement for the attenuated rays.

[0133] ② Determining the aperture and length of the collimating hole on the pinhole collimator mainly considers the attenuation effect on the radiation rays entering the detector. This is the key point in the control process. At this time, the upper and lower limits of the flux attenuation effect need to be considered first.

[0134] Scintillation crystals have numerous applications in radiation detection, such as oil well logging, space payloads, and medical imaging. This study uses a scintillation crystal detector used in high-energy physics experiments as an example. These experiments typically prioritize high spatial resolution and testing accuracy, while minimizing background noise and environmental radiation. To achieve these effects, the collimator requires highly attenuated and precisely controlled radiation rays. Currently, this application requires approximately 0.1-2% flux retained after collimation, i.e., an attenuation ratio of 98-99.9%. It is important to clarify that aperture is the primary parameter determining radiation flux. It mainly limits the incident angle θ of the radiation rays included in the effective flux. A smaller aperture results in a smaller θ and a higher signal-to-noise ratio of the radiation flux entering the downstream testing unit, but also leads to greater flux loss and reduced detection efficiency. Aperture length is the second parameter affecting radiation flux in conjunction with aperture. It also corresponds to the total horizontal length of the collimator assembly. A larger aperture length results in higher testing accuracy (i.e., higher spatial resolution), but also greater flux loss.

[0135] Regarding the aperture, considering the differences in size and shape of different tested crystals, its size should not exceed one-third of the length of the irradiated cross section of the tested crystal to ensure the accuracy of the test point. It should not be less than 0.1 mm, because if the aperture is too small, the area of ​​the detector to be irradiated will be extremely small and will not be able to reach the detection sensitivity threshold, thus making the test impossible to proceed normally.

[0136] Regarding the hole length, the structural design of the pinhole collimator determines that the hole length of the collimating component is almost equal to its total length L in the horizontal direction. Therefore, the sum of the hole lengths of the collimating holes in the same orientation on the pinhole collimator is equal to the total length of the collimating component in the horizontal direction.

[0137] To ensure that the test variables are controllable, all pinhole collimators used maintain the same upper opening diameter during the test;

[0138] After roughly clarifying some limitations on aperture and aperture length, we then consider their corresponding attenuation effect on radiation flux to further clarify their control and limitations. At this point, a simplified geometric solid angle formula is introduced to link the three parameters of aperture, aperture length, and radiation flux together, for the radiation flux A that completely passes through the collimating aperture and exits to the detector. total Perform the calculation.

[0139] Let B = 1 - A. total The ratio of flux attenuation of the radiation rays entering the detector relative to the flux before entering the collimation aperture of the pinhole collimator is considered. Given that the collimation assembly used in this invention essentially consists of multiple cylindrical pinhole collimators of the same thickness (or unequal thickness, similar to Part ①, where the initial discussion is based on the premise of the same thickness) placed on the same horizontal line, with a certain distance maintained between each collimator, such as... Figure 4 As shown. At this point, it is necessary to consider the number of collimators n and the spacing s between each collimator; the spacing s should be as small as possible (<2mm) to eliminate its influence on the radiation. Then, let t represent the horizontal thickness of a single collimator, or the length of its collimating aperture, and L represent the total horizontal thickness or total aperture length of the n collimators, L≈nt. The collimating aperture configuration of each collimator is as follows. Figure 4 As shown, consider an incident angle θ of the radiation ray relative to the central axis of the collimating aperture. Regarding the determination of the upper and lower limits of B, it is first necessary to clarify that the main function of the pinhole collimator is to maximize the temporal and spatial resolution of the radiation source during testing, while reducing the interference of external magnetic fields and the large amount of scattering of radiation rays from the source on the crystal performance obtained from the test. Therefore, regardless of the adjustment, its attenuation effect on the radiation flux is inevitably significant. Based on its application context, its upper and lower limits depend more on the relative trade-off between improving testing efficiency or further improving accuracy under existing high-precision conditions. This is mainly affected by the values ​​of the aperture and aperture length—if high accuracy is pursued, the aperture should be as small as possible and the aperture length as large as possible; if high efficiency is pursued, the opposite is true. This coincides with the geometric solid angle formula listed above. Considering that the flux of radiation rays from a low-activity radiation source is too small after attenuation by the collimator to meet the detection threshold (minimum limit) of the scintillation crystal detector, B = 1 - A is determined accordingly. total The range is 98% to 99.5%, which is quite close to the range of the above-mentioned high-energy physics experimental templates.

[0140] This concludes the complete description of all key parameters of the alignment component. Based on this, the research work shown in the following embodiments was carried out:

[0141] Example 1

[0142] Complete the installation and configuration of all components before testing:

[0143] In the case of scintillation crystal detectors used in high-energy physics experiments, a LaBr3:Ce crystal with a doping concentration of 5% and a diameter and height of 38 mm is wrapped with a reflective layer of PTFE and then encapsulated in a special aluminum shell (diameter and height of 42 mm) to prevent it from deliquescing and oxidizing. Then, optical silicone oil is used to couple it with a photomultiplier tube and seal it into the detector housing to complete the overall assembly of the detector.

[0144] Use of radioactive sources 137 Cs standard source;

[0145] The lifting platform used has a surface size of 150mm×150mm and a lifting height range of 75-260mm;

[0146] The pinhole collimator used is made of pure lead and has four side openings. Its specific structure is similar to... Figure 2 This is consistent with the results shown. At this point, μ is 1.25 cm. -1 , let A=0.99, then I / I0=e -μx =0.01, and after calculation, we get x≈3.68cm. At this time, p min h min Both L and L must be greater than this value. Based on this, the following parameters are determined: the complete diameter of a single collimator is 100mm and the thickness is 10mm; the diameter of the central mounting hole of the collimator is 50mm; the diameters of the side circular openings 442, 443, 444, and 445 are 5mm, 7mm, 9mm, and 11mm, respectively; the distance from the center of each hole to the core of the square opening 441 is 60mm; and the horizontal distance from the nearest collimator edge is 40mm.

[0147] In Example 1, the overall test system is assembled and built according to the steps described in the technical solution. The upper openings of the pinhole collimator 44 are selected as 443 and 445, respectively, and the total horizontal length of the collimator assembly is selected as 55mm and 40mm, respectively (calculations show that the attenuation effect of the two aperture and length combinations on the flux is close to their upper and lower limits). Based on this, two corresponding tests are performed. Figure 5The non-uniformity of relative light output and energy resolution along the scintillation crystal axis was tested at the marked points at different angles. Specifically, by adjusting the height of the lifting platform so that the center of the region at a distance of 5 / 10 / 15 / 20 / 25 / 30 mm from the PMT incident surface of the crystal was aligned with the center of the aperture above the collimator and the center of the circular radiation source, the high-voltage source output voltage was set to -700V, and the main amplifier gain was set to 50 and the forming time to 1µs. Finally, data images were acquired for 300s using pulse height spectroscopy testing software. Tables 1 and 2 show the numerical comparison results of relative light output and energy resolution of LaBr3:Ce under the conditions of 443 aperture and 55mm length, and 445 aperture and 40mm length, respectively. Figure 7 This shows the corresponding pulse height spectrum images of the same location under two test conditions.

[0148] In Example 1, to further characterize the local property uniformity of the LaBr3:Ce crystal in three-dimensional space, based on the existing axial uniformity results (Table 2), and while maintaining the same collimator parameters, based on... Figure 6 The relative light output, energy resolution, and radial uniformity of the crystal were tested, and the results are shown in Table 3. The results show that the LaBr3:Ce crystal used exhibits good performance in these aspects. Figure 5 The region 10-25 mm from the PMT incident surface along the defined 90° and 180° axes exhibited the best uniformity and performance. Based on this conclusion, cutting was performed from the corresponding region to obtain... Figure 8 The dimensions shown are 6×6×6 mm. 3 A cubic crystal.

[0149] Table 1

[0150]

[0151] Table 2

[0152]

[0153] Table 3

[0154]

[0155] Example 2

[0156] Complete the installation and configuration of all components before testing:

[0157] For scintillation crystal detectors used in high-energy physics experiments, a LaBr3:Ce,Sr crystal with a Ce doping concentration of 5%, a Sr doping concentration of 0.5%, a diameter of 38 mm, and a height of 32 mm is wrapped with a reflective PTFE layer and then encapsulated in a special aluminum shell (diameter and height of 42 mm) to prevent it from deliquescing and oxidation. Then, optical silicone oil is used to couple it with the PMT and seal it into the detector housing to complete the overall assembly of the detector.

[0158] The radioactive source uses an energy of 662 keV. 137 Cs standard source;

[0159] The lifting platform used has a surface size of 150mm×150mm and a lifting height range of 75-260mm;

[0160] The pinhole collimator used is made of pure lead and has four side openings. Its specific structure is similar to... Figure 2 This is consistent with the results shown. At this point, μ is 1.25 cm. -1 , let A=0.99, then I / I0=e -μx =0.01, and after calculation, we get x≈3.68cm. At this time, p min h min Both L and L must be greater than this value. Based on this, the following parameters are determined: the complete diameter of a single collimator is 100mm and the thickness is 10mm; the diameter of the central mounting hole of the collimator is 50mm; the diameters of the side circular openings 442, 443, 444, and 445 are 1mm, 3mm, 5mm, and 7mm, respectively; the distance from the center of each hole to the core of the square opening 441 is 60mm; and the horizontal distance from the nearest edge is 40mm.

[0161] In Example 2, the overall testing system was assembled and built according to the steps described in the technical solution. The upper openings of the pinhole limiter 44 were selected as 443 and 445, respectively, and the total horizontal length of the collimation component was selected as 55mm and 40mm, respectively (calculations showed that the attenuation effect of the two aperture and length combinations on flux was close to their upper and lower limits). Based on this, two corresponding tests were performed. The relative light output and energy resolution axial non-uniformity tests of the crystal were based on... Figure 5The marking points were determined at different angles. Specifically, by adjusting the height of the lifting platform so that the center of the region at a distance of 5 / 10 / 15 / 20 / 25 / 30 mm from the PMT incident surface was aligned with the center of the opening above the collimator and the center of the circular radiation source, the high-voltage source output voltage was set to -700V, and the main amplifier gain was set to 50 and the forming time to 1µs. Finally, data image acquisition for 300s was performed using pulse height spectroscopy testing software. Tables 4 and 5 show the relative light output and energy resolution values ​​of LaBr3:Ce,Sr under the conditions of 443 opening and 55mm length, and 445 opening and 40mm length, respectively. Figure 9 This shows the corresponding pulse height spectrum images of the same location under two test conditions.

[0162] Table 4

[0163]

[0164] Table 5

[0165]

[0166] Table 6

[0167]

[0168] In Example 2, to further characterize the local property uniformity of the LaBr3:Ce crystal in three-dimensional space, based on the existing axial uniformity results (Table 5), and while maintaining the same collimator parameters, based on... Figure 6 The relative light output, energy resolution, and radial uniformity of the crystal were tested, and the results are shown in Table 6. The results show that the LaBr3:Ce crystal used exhibits good performance in these aspects. Figure 5 The region 20-30 mm from the PMT incident surface along the defined 0° and 90° axes exhibited the best uniformity. Based on this conclusion, cutting was performed from the corresponding region to obtain... Figure 10 The dimensions shown are 6×6×6 mm. 3 A cubic crystal.

[0169] Example 3

[0170] Complete the installation and configuration of all components before testing:

[0171] For the detector, a standard LaBr3:Ce crystal with a Ce doping concentration of 5% and a diameter and height of 38mm is wrapped with a reflective PTFE layer and then encapsulated in a special aluminum shell (diameter and height of 42mm) to prevent it from deliquescing and oxidizing. Then, optical silicone oil is used to couple it with the PMT and seal it into the detector housing to complete the overall assembly of the detector.

[0172] The radioactive source uses an energy of 662 keV. 137 Cs standard source and to be calibrated 137 Cs source (energy: 662 keV; activity: 1 μCi);

[0173] The lifting platform used has a surface size of 150mm×150mm and a lifting height range of 75-260m;

[0174] The pinhole collimator used is made of pure lead and has four side openings. Its specific structure is similar to... Figure 2 This is consistent with the results shown. At this point, μ is 1.25 cm. -1 , let A=0.99, then I / I0=e -μx =0.01, and after calculation, we get x≈3.68cm. At this time, p min h min Both L and L must be greater than this value. Based on this, the following parameters are determined: the complete diameter of a single collimator is 100mm and the thickness is 10mm; the diameter of the central mounting hole of the collimator is 50mm; the diameters of the side circular openings 442, 443, 444, and 445 are 1mm, 3mm, 5mm, and 7mm, respectively; the distance from the center of each hole to the core of the square opening 441 is 60mm; and the horizontal distance from the nearest edge is 40mm.

[0175] In Example 3, the overall testing system is assembled and built according to the steps described in the technical solution. The upper opening of the pinhole limiter 44 is selected as 444, and the total length of the collimator is selected as 38mm. Based on this, two tests are performed: first, […]. 137 The Cs standard source is loaded into the radiation source housing module 32, and the scissor-type lifting platform 5 is adjusted so that the center of the standard LaBr3:Ce crystal is aligned with the radiation source housing module 32. 137 The centers of the Cs standard source and collimator aperture 444 are aligned on the same horizontal line. The high-voltage source output voltage is set to -700V, and the main amplifier gain is set to 50 and the forming time to 1µs. Finally, a 300s pulse height spectrum image is acquired using pulse height spectrum testing software on a computer. After completing the above test, the pressure is released and... 137 Cs standard source is taken out and placed into the calibration chamber. 137 The Cs source was repressurized while keeping other conditions unchanged, and pulse height spectra were acquired again. The results are as follows: Figure 11 As shown.

[0176] In Example 3, the energy consistency and activity of the radioactive source to be calibrated can be determined based on the channel address (channel value at the peak) and count rate difference of the full-energy peak in the pulse height spectrum. According to... Figure 9 The results shown in the diagram indicate that the track position is almost identical under both test conditions, proving that the calibration is not yet complete.137 Cs source energy and standard 137 The Cs source is consistent, both at 662 keV; standard 137 The Cs source test yielded a total peak count of 796.231, with a count rate of approximately 2.65, while the target calibration... 137 The Cs source test yielded a total peak count of 568.044 and a count rate of approximately 1.89, indicating that calibration is required. 137 The activity of the Cs source is 1. (1.89 / 2.65) = 0.71μCi.

[0177] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A performance testing system for inorganic scintillation crystals based on an adjustable pinhole collimator, characterized in that: It includes a base, a radiation source, a radiation source limiting unit, a collimation assembly, a collimation adjustment unit, a detector position adjustment unit, and a back-end testing unit; Definition: One side of the base is the front end, and the opposite side is the rear end; From front end to rear end, the base is fixed and supports the detector position adjustment unit, the collimation adjustment unit, and the radiation source limiting unit; The radioactive source limiting unit includes a support rod, a connecting rod, and a radioactive source receiving module; wherein, the support rod is vertically installed on the base, and the connecting rod is vertically installed on the support rod at one end, and the radioactive source receiving module is detachably installed at the other end; the radioactive source receiving module is used to accommodate the radioactive source, and its front end face is provided with an opening, the center of which is located on the same horizontal line as the center of the radioactive source, and the size of the opening is smaller than the size of the radioactive source; The collimation adjustment unit includes a support frame and an adjustment rod; wherein, the support frame is fixed on the base; the adjustment rod is horizontally installed on the support frame from front to back, and its position is adjustable, but it will not rotate relative to the support frame after installation. The collimation assembly includes multiple pinhole collimators; these pinhole collimators are coaxially spaced on an adjusting rod and do not rotate relative to the adjusting rod, with adjacent pinhole collimators spaced less than 2 mm apart; each pinhole collimator has a coaxial mounting hole, and in addition, 3-5 collimation holes of different diameters are evenly distributed on the pinhole collimator, with the center of each collimation hole located on the same circumference centered on the center of the pinhole collimator itself; the total horizontal length L of the collimation assembly and the two thicknesses in the vertical direction of the collimation holes can both ensure that the ineffective radiation rays can achieve attenuation of more than 99%; the two thicknesses are the distance p between the side of the collimation hole closest to the edge of the pinhole collimator and the edge of the pinhole collimator, and the distance h between the side of the collimation hole closest to the edge of the mounting hole and the edge of the mounting hole; under the adjustment of the adjusting rod, the collimation hole on each pinhole collimator can be located on the same horizontal line as the center of the radiation source; The detector position adjustment unit includes a lifting assembly and a detector limiting assembly; wherein, the detector limiting assembly is used to limit and accommodate the inorganic scintillation crystal detector, and its overall design is light-shielding and the material is magnetic shielding material; the lifting assembly is used to stably support the detector limiting assembly and adjust the height of the detector limiting assembly so that different height regions of the crystal in the inorganic scintillation crystal detector are on the same horizontal line as the center of the radiation source. The back-end test unit is connected to the inorganic scintillation crystal detector and is used to test the performance of the inorganic scintillation crystal detector.

2. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 1, characterized in that, The collimation component determines its key parameters using the following method: ① Based on the requirement that the attenuation flux of ineffective radiation rays reaches more than 99%, and following the attenuation coefficient formula, determine the total length of the collimation assembly in the horizontal direction, as well as the thicknesses p and h at the two points in the vertical direction of the maximum collimation hole on the pinhole collimator; ② Determine the diameter and length of the collimation hole on the pinhole collimator. First, the limitations on the aperture and aperture length are defined as follows: the aperture is greater than or equal to 0.1 mm and less than or equal to one-third of the vertical length of the irradiated cross section of the crystal in the inorganic scintillation crystal detector under test; The sum of the lengths of the collimating holes on all pinhole collimators is equal to the total length of the collimating assembly in the horizontal direction; Secondly, in order to achieve precise control of the flux after attenuation, the diameter and length of the collimating orifice are specifically determined by following the geometric solid angle formula.

3. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 1 or 2, characterized in that: The other end of the connecting rod has a snap-fit ​​structure, which can install and remove the radiation source containing module; The upper surface of the radiation source containing module is provided with a placement hole, and a matching cover is also provided; The opening is a square hole, the side length of which is smaller than the diameter of the radiation source.

4. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 3, characterized in that: The support frame includes four first fixed rods and two second fixed rods; All four first fixing rods are vertically installed on the base and are arranged symmetrically in pairs to form a cubic frame; Two second fixing rods are respectively installed between the two first fixing rods at the front end and between the two first fixing rods at the rear end of the cube frame, and each of the two second fixing rods has a square opening in the middle for inserting and removing the adjusting rod; The adjusting rod is a square rod that can be fitted with a square opening in the middle of the second fixing rod.

5. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 4, characterized in that: The pinhole collimator is a cylindrical radiation attenuator with a square mounting hole coaxially arranged at its center to fit the adjustment rod with clearance. It also has four collimation holes of different diameters on the positive and negative sides, with the center of the pinhole collimator as the origin and the coordinate axis as the coordinate axis.

6. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 5, characterized in that: The lifting assembly is a scissor lift platform, the surface of which is covered with anti-slip material, and its adjustment accuracy does not exceed 5μm; The detector limiting assembly includes a limiting module and a limiting cover.

7. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 6, characterized in that: The collimator adjustment unit also includes a storage component for accommodating the pinhole collimator. The storage component is located on the base below the adjustment rod, and it has a semi-circular groove with a diameter larger than that of the pinhole collimator.

8. The inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator according to claim 7, characterized in that: The radioactive source is a high-energy gamma radioactive source.

9. A test method using the inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Install the radiation source The radioactive source is placed in the radioactive source receiving module, and the radioactive source receiving module is installed at the other end of the connecting rod; Step 2: Install the collimation components Install each pinhole collimator of the collimation assembly onto the adjusting rod in sequence. Then, install the adjusting rod horizontally onto the support frame from front to back and fix it in place. Ensure that the collimation hole diameters corresponding to each pinhole collimator are not only the same, but also that the center of the collimation hole located above is on the same horizontal straight line as the center of the radiation source. Step 3: Install the inorganic scintillation crystal detector to be tested The inorganic scintillation crystal detector to be tested is placed in the detector limiting assembly, and the detector limiting assembly is placed stably on the upper surface of the lifting assembly. By adjusting the height, the initial height area of ​​the crystal in the inorganic scintillation crystal detector to be tested is aligned with the center of the radiation source and the center of the collimation hole above. Step 4: Test the crystal performance in the inorganic scintillation crystal detector under test. Connect the inorganic scintillation crystal detector under test to the back-end test unit, set the prerequisite parameters according to the type of test performance, start the test after completing the settings, and collect the test results. After completing the initial height area test, adjust the lifting component to change the height area of ​​the crystal in the inorganic scintillation crystal detector under test, and continue testing. Repeat this process. After completing the current angle test, rotate the detector limiting component as required to perform the next set of tests. Repeat this process until all tests under the current collimation component parameter conditions are completed.

10. A method for calibrating a radioactive source using the inorganic scintillation crystal performance testing system based on an adjustable pinhole collimator as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Install standard radioactive sources A standard radioactive source with a known activity of A0 is placed in the radioactive source housing module, and the radioactive source housing module is installed at the other end of the connecting rod; S2: Install the alignment components Install each pinhole collimator of the collimation assembly onto the adjusting rod in sequence. Then, install the adjusting rod horizontally onto the support frame from front to back and fix it in place. Ensure that the collimation hole diameters corresponding to each pinhole collimator are not only the same, but also that the center of the collimation hole located above is on the same horizontal straight line as the center of the radiation source. S3: Install an inorganic scintillation crystal detector The inorganic scintillation crystal detector containing the standard scintillation crystal is placed in the detector limiting assembly, and the detector limiting assembly is placed stably on the upper surface of the lifting assembly. By adjusting the height, the initial height area of ​​the crystal in the inorganic scintillation crystal detector for testing is aligned with the center of the radiation source and the center of the collimation hole above. S4: Testing the standard radioactive source Connect the inorganic scintillation crystal detector to the pulse height spectroscopy test equipment and ensure a light-protected environment; set the prerequisite parameters of the pulse height spectroscopy test equipment, and after completing the settings, start the test and collect the full-energy peak address Ch0 and count rate R0; S5: Replacement and Testing of Radioactive Sources to be Calibrated After completing S4, remove the voltage and turn off the pulse height spectroscopy test equipment. Replace the standard radioactive source in the radioactive source containment module with the radioactive source to be calibrated. Then repeat the test process in S4 and collect the full-energy peak address Ch1 and count rate R1. After completing the test, remove the voltage and turn off the pulse height spectroscopy test equipment. S6: Radioactive source calibration Comparing the differences in the results for the total energy peak location and count rate obtained in S4 and S5, the following calibration calculations were performed on the radioactive source to be calibrated: ① Energy consistency: Calculated using the following formula Energy uniformity=(Ch1-Ch0) / Ch0 If the value is ≤1%, the energy of the radioactive source to be calibrated is considered to be the same as that of the standard radioactive source. ② The activity A1 of the radioactive source to be calibrated: calculated using the following formula A1 = A0 × (R1 / R0) This completes the entire process of radioactive source calibration.

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