A portable gamma irradiation collimator and its design method

Abstract

The present invention discloses a portable gamma irradiation collimator and a design method thereof. The portable gamma irradiation collimator comprises: an irradiation source chamber, a shielding body and an irradiation opening; the irradiation source chamber is used to accommodate gamma irradiation sources of different sizes; the irradiation opening is used to collimate the gamma rays emitted by the gamma irradiation source; the irradiation source chamber is located at the center of the shielding body; the irradiation opening passes through the shielding body and is connected to the irradiation source chamber; the uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening meet the preset requirements. The portable gamma irradiation collimator can accommodate gamma irradiation sources of different sizes, and the uniformity and scattering characteristics of the generated gamma radiation field meet the preset requirements, which expands the scope of application of the portable gamma radiation collimator.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of ionizing radiation dosimetry, and in particular to a portable gamma irradiation collimator and a design method thereof. Background Art

[0002] After the γ radiation source is installed in the γ irradiation collimator, it can provide a γ radiation field that meets certain technical indicators. It is often used in food sterilization, industrial flaw detection, and ionizing radiation dosimetry research. At present, most γ irradiation collimators are relatively bulky. In order to ensure that the emitted γ radiation field meets certain technical requirements, they are fixed in the γ irradiation laboratory. With the development of ionizing radiation technology and its applications, some special irradiation needs cannot be carried out in the γ irradiation laboratory, and on-site or online operations are required. Therefore, it is necessary to develop and design portable γ irradiation collimators.

[0003] In the existing portable gamma irradiation collimator, the gamma radiation source is placed on the side of the irradiation opening close to the center of the shield, and only a specific gamma radiation source can be placed. Gamma radiation sources of different sizes correspond to different gamma irradiation collimators. Therefore, for the designed gamma irradiation collimator, only one size of gamma radiation source can be placed, and its application range is relatively narrow and its applicability is relatively low. In addition, the opening diameter of the irradiation opening away from the center of the shield in the existing portable gamma irradiation collimator is relatively large, and the size of the radiation attenuation plate matched with it is relatively large, which is inconvenient to use in some cases where there are requirements for size, limiting the application scenario of the gamma irradiation collimator and further affecting the application scope of the portable gamma irradiation collimator. Due to the organic combination of all dimensional parameters in the gamma irradiation collimator, a portable gamma irradiation collimator that meets the requirements of uniformity and scattering characteristics of the radiation field can be designed. Therefore, the size of the chamber for placing the gamma radiation source and the opening diameter of the irradiation opening away from the center of the shield cannot be adjusted at will, otherwise the portable gamma irradiation collimator cannot meet the requirements of uniformity and scattering characteristics of the radiation field. Summary of the invention

[0004] The invention provides a portable gamma radiation collimator and a design method thereof, so as to expand the application range of the portable gamma radiation collimator and improve its applicability.

[0005] In a first aspect, an embodiment of the present invention provides a portable gamma irradiation collimator, the portable gamma irradiation collimator comprising: an irradiation source chamber, a shielding body and an irradiation opening; the irradiation source chamber is used to accommodate gamma irradiation sources of different sizes; the irradiation opening is used to collimate the gamma rays emitted by the gamma irradiation source;

[0006] The radiation source chamber is located at the center of the shielding body; the radiation opening passes through the shielding body and is connected to the radiation source chamber;

[0007] The uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening meet preset requirements.

[0008] Optionally, a side of the irradiation opening facing away from the irradiation source chamber is a first opening, a surface at a connection between the shielding body and the first opening is a first surface, and the first surface is parallel to the first opening.

[0009] Optionally, the radiation source chamber is cylindrical; the bottom surface of the cylinder is parallel to the central axis of the radiation opening; the first surface and the radiation source chamber are symmetrically distributed along the central axis of the radiation opening.

[0010] Optionally, a height H of a side wall of the irradiation source chamber communicating with the irradiation opening satisfies: 10 mm ≤ H ≤ 30 mm; and a diameter D of a bottom surface of the irradiation source chamber satisfies: 8 mm ≤ D ≤ 20 mm.

[0011] Optionally, the shielding body further includes a second surface; the second surface is connected to the first surface; the second surface is spherical; and the center of the sphere coincides with the center of the irradiation source chamber; the radius R of the sphere satisfies: R≥35mm.

[0012] Optionally, a side of the irradiation opening close to the irradiation source chamber is a second opening, and a height W of the second opening satisfies: 8 mm ≤ W ≤ 20 mm.

[0013] Optionally, an angle θ between a side wall of the irradiation opening and a central axis of the irradiation opening satisfies: 20°≤θ≤45°.

[0014] Optionally, along a direction parallel to a central axis of the irradiation opening, a distance L between the first opening and the second opening satisfies: 10 mm ≤ L ≤ 35 mm.

[0015] Optionally, the shielding body material includes lead and its alloys, tungsten and its alloys, or depleted uranium and its alloys.

[0016] In a second aspect, an embodiment of the present invention further provides a method for designing a portable gamma irradiation collimator, the method being used to design the portable gamma irradiation collimator provided in the first aspect, comprising:

[0017] The gamma irradiation collimator model was constructed by Monte Carlo simulation technology;

[0018] An orthogonal experimental table is designed according to the Taguchi experimental design method; the orthogonal experimental table includes a combination of multiple γ-irradiation collimator model size parameters;

[0019] According to the gamma irradiation collimator model, simulating the uniformity and scattering characteristics of the gamma radiation field of the gamma irradiation collimator under different combinations of size parameters of the gamma irradiation collimator model;

[0020] According to the simulation results of the Taguchi experimental design method, a combination of the gamma irradiation collimator model size parameters whose uniformity and scattering characteristics of the gamma radiation field meet preset requirements is selected to design the portable gamma irradiation collimator.

[0021] The portable gamma irradiation collimator provided by the embodiment of the present invention is provided with an irradiation source chamber at the center position of the shielding body to accommodate gamma irradiation sources of different sizes, and an irradiation opening penetrating the shielding body and communicating with the irradiation source chamber is provided to collimate the gamma rays emitted by the gamma irradiation source, thereby realizing the collimation of the gamma radiation field. The uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening meet the preset requirements, that is, the uniformity and scattering characteristics of the collimated gamma radiation field meet the preset requirements. In summary, the portable gamma irradiation collimator provided by the embodiment of the present invention can be applied to gamma irradiation sources of different sizes, the opening caliber away from the center of the shielding body can be reduced as required, and the uniformity and scattering characteristics of the generated gamma radiation field meet the preset requirements, therefore, the applicable scope of the portable gamma irradiation collimator can be expanded and its applicability can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of a portable gamma irradiation collimator provided in an embodiment of the present invention;

[0023] Figure 2 A method for Figure 1 The schematic diagram of the structure of the radiation attenuation sheet of the portable gamma irradiation collimator shown;

[0024] Figure 3 A schematic diagram of the uniformity of a gamma radiation field formed by a portable gamma irradiation collimator provided by an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of the scattering characteristics of a gamma radiation field formed by a portable gamma irradiation collimator provided in an embodiment of the present invention

[0026] Figure 5 A schematic flow chart of a design method of a portable gamma irradiation collimator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0028] Figure 1The structure diagram of a portable gamma irradiation collimator provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the portable gamma irradiation collimator 100 comprises: an irradiation source chamber 110, a shielding body 120 and an irradiation opening 130; the irradiation source chamber 110 is used to accommodate gamma irradiation sources of different sizes; the irradiation opening 130 is used to emit gamma rays emitted by the gamma irradiation source.

[0029] The radiation source chamber 110 is located at the center of the shielding body 120 ; the radiation opening 130 passes through the shielding body 120 and is communicated with the radiation source chamber 110 .

[0030] The uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening 130 meet the preset requirements.

[0031] Specifically, Figure 1 As shown, an irradiation source chamber 110 is arranged at the center of the shield 120, and the inner surface of the shield 120 forms the surface of the irradiation source chamber 110. The irradiation source chamber 110 can accommodate γ irradiation sources of different sizes, and the γ irradiation source provides a radiation field in a 4π direction, that is, the γ irradiation source can emit γ rays in all directions; the irradiation opening 130 passes through the shield 120 and is connected to the irradiation source chamber 110, that is, the irradiation opening 130 connects the irradiation source chamber 110 and the external environment, and only part of the γ rays emitted by the γ irradiation source are emitted to the external environment through the irradiation opening 130, and the remaining part is absorbed by the shield 120, so that the emission angle of the γ rays is within a certain angle range, so the portable γ irradiation collimator 100 constrains the radiation field in the 4π direction to a collimated radiation field. It should be noted that the shield 120 can be made of radiation shielding materials such as lead and its alloys, tungsten and its alloys, and depleted uranium.

[0032] The uniformity and scattering characteristics of the collimated gamma rays emitted from the irradiation opening 130 meet the preset requirements, that is, the uniformity and scattering characteristics of the collimated gamma radiation field meet the preset requirements, for example: the uniformity of the collimated gamma radiation field meets that the diameter of the uniform field at a distance of 100 cm from the center of the portable gamma irradiation collimator 100 is not less than 30 cm, and the relative deviation of the air kerma rate in the uniform field does not exceed 5%; the scattering characteristics of the collimated gamma radiation field meet that on the central axis of the radiation opening 130, the air kerma rate is proportional to the inverse of the square of the distance from the center of the gamma irradiation source to the center of the detector, and the deviation from the ideal value does not exceed 5%. It should be noted that the embodiment of the present invention only exemplifies the preset requirements for the uniformity and scattering characteristics of the collimated gamma radiation field, and does not limit this.

[0033] The portable gamma irradiation collimator provided by the embodiment of the present invention is provided with an irradiation source chamber at the center position of the shielding body to accommodate gamma irradiation sources of different sizes, and an irradiation opening penetrating the shielding body and communicating with the irradiation source chamber is provided to collimate the gamma rays emitted by the gamma irradiation source, thereby realizing the collimation of the gamma radiation field. The uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening meet the preset requirements, that is, the uniformity and scattering characteristics of the collimated gamma radiation field meet the preset requirements. In summary, the portable gamma irradiation collimator provided by the embodiment of the present invention can be applied to gamma irradiation sources of different sizes, the opening caliber away from the center of the shielding body can be reduced as required, and the uniformity and scattering characteristics of the generated gamma radiation field meet the preset requirements, therefore, the applicable scope of the portable gamma irradiation collimator can be expanded and its applicability can be improved.

[0034] Optional, continue to see Figure 1 The side of the irradiation opening 130 facing away from the irradiation source chamber 110 is a first opening 131 , and the connecting surface of the shielding body 120 and the first opening 131 is a first surface 121 . The first surface 121 is parallel to the first opening 131 .

[0035] Specifically, Figure 1 As shown, the first surface 121 is parallel to the first opening 131, the distance between the first opening 131 and the second opening 132 is L, and the angle between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130 is θ. From the perspective of geometric structure, the distance L between the first opening 131 and the second opening 132 is irrelevant to the angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130. Therefore, the two parameters are only subject to the uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening 130 meeting the preset requirements, which reduces the distance between the first opening 131 and the second opening. The correlation between the distance L between the first opening 131 and the second opening 132 and the angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130 is conducive to more flexible setting of the distance L between the first opening 131 and the second opening 132 and the angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130, so it is conducive to designing a portable gamma irradiation collimator with a lower height of the first opening 131, and it is conducive to reducing the size of the radiation attenuation plate matched with the portable gamma irradiation collimator, thereby increasing the use scenarios of the portable gamma irradiation collimator and further improving its scope of application. It should be noted that in actual applications, the first surface 121 and the first opening 131 can be approximately parallel.

[0036] Optional, continue to see Figure 1 , the radiation source chamber 110 is cylindrical; the bottom surface of the cylinder is parallel to the central axis of the radiation opening 130 ; the first surface 121 and the radiation source chamber 110 are symmetrically distributed along the central axis of the radiation opening 130 .

[0037] Specifically, Figure 1 As shown, the bottom surface of the cylinder is parallel to the central axis of the irradiation opening 130 (the dotted arrow shown in the figure). In actual applications, common exempted-level gamma irradiation sources or Class V gamma irradiation sources are mainly cylindrical. Therefore, the irradiation source chamber 110 that accommodates gamma irradiation sources of different sizes is also set to be cylindrical, which can accommodate the common exempted-level gamma irradiation sources or Class V gamma irradiation sources on the market while avoiding occupying too much space.

[0038] Optional, continue to see Figure 1 , the height H of the side wall of the irradiation source chamber 110 communicating with the irradiation opening 130 satisfies: 10 mm ≤ H ≤ 30 mm; the diameter D of the bottom surface of the irradiation source chamber 110 satisfies: 8 mm ≤ D ≤ 20 mm.

[0039] Specifically, the height of the currently existing γ irradiation source generally does not exceed 10 mm, and the diameter of the bottom surface of the γ irradiation source generally does not exceed 8 mm. In order to facilitate the placement of the γ irradiation source, the size of the irradiation source chamber 110 needs to be set to be greater than or equal to the size of the γ irradiation source. Therefore, the side wall height H of the irradiation source chamber 110 connecting with the irradiation opening 130 is greater than or equal to 10 mm, and the diameter D of the bottom surface of the irradiation source chamber 110 is greater than or equal to 8 mm. In addition, if the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 and the diameter D of the bottom surface of the irradiation source chamber 110 are too large, it will affect the uniformity and scattering characteristics of the emitted γ radiation field and the shielding effect in the non-collimated direction. The Monte Carlo simulation results show that the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 should not be greater than 30 mm, and the diameter D of the bottom surface of the irradiation source chamber 120 should not be greater than 20 mm. Therefore, the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 satisfies 10 mm ≤ H ≤ 30 mm; the diameter D of the bottom surface of the irradiation source chamber 110 satisfies 8 mm ≤ D ≤ 20 mm.

[0040] Optional, continue to see Figure 1 The shielding body 120 further includes a second surface 122; the second surface 122 is connected to the first surface 121; the second surface 122 is spherical; and the center of the sphere coincides with the center of the irradiation source chamber 110; the radius R of the sphere satisfies: R≥35mm.

[0041] Specifically, the portable gamma irradiation collimator 100 needs to shield the gamma rays radiated by the gamma radiation source in the main shielding direction by no less than 99.9% to ensure the radiation safety of the surrounding personnel. 137 The shielding capability of the gamma ray of Cs is such that the radius R of the sphere where the second surface 122 of the shielding body 120 is located satisfies: R ≥ 35 mm. For example, the gamma radiation source is 137 Cs radiation source, the shielding body 120 is made of tungsten alloy, combined with tungsten alloy 137The shielding capability of the gamma ray of Cs should be at least 38mm in the main shielding direction to realize the portable gamma irradiation collimator 100 to shield the gamma ray of Cs. 137 The shielding rate of the gamma ray of Cs is not less than 99.9%. Considering that the irradiation source chamber 110 is arranged at the center of the shielding body 120, the radius R of the sphere where the second surface 132 is located should be greater than or equal to 50 mm. In practical applications, the radius R of the sphere where the second surface 122 is located can be flexibly set according to the type of the gamma radiation source and the material of the shielding body 120.

[0042] Optional, continue to see Figure 1 The side of the irradiation opening 130 close to the irradiation source chamber 110 is a second opening 132 , and the height W of the second opening 132 satisfies: 8 mm≤W≤20 mm.

[0043] Specifically, the portable gamma irradiation collimator 100 can form a gamma radiation field whose uniformity and scattering characteristics meet preset requirements. For example, the uniformity meets the preset requirements, which means that the diameter of the uniform field 100 cm away from the center of the portable gamma irradiation collimator 100 is not less than 30 cm, and the relative deviation of the air kerma rate in the uniform field does not exceed 5%; the scattering characteristics meet the preset requirements, which means that on the central axis of the radiation opening 130, the air kerma rate is proportional to the inverse of the square of the distance from the center of the gamma irradiation source to the center of the detector, and the deviation from the ideal value does not exceed 5%. When the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 satisfies: 10mm≤H≤30mm, the diameter D of the bottom surface of the irradiation source chamber 110 satisfies: 8mm≤D≤20mm, and the radius R of the sphere where the second surface 122 of the shielding body 120 is located satisfies: R≥35mm, the height W of the second opening 132 is set to 8mm≤W≤20mm to ensure that the uniformity and scattering characteristics of the gamma radiation field formed by the portable gamma irradiation collimator 100 meet the above-mentioned preset requirements.

[0044] Optional, continue to see Figure 1 , an angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130 satisfies: 20°≤θ≤45°.

[0045] Specifically, when the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 satisfies: 10mm≤H≤30mm, the diameter D of the bottom surface of the irradiation source chamber 110 satisfies: 8mm≤D≤20mm, and the radius R of the sphere where the second surface 122 of the shielding body 120 is located satisfies: R≥35mm, the angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130 is set to 20°≤θ≤45°, so as to ensure that the uniformity and scattering characteristics of the γ radiation field formed by the portable γ irradiation collimator 100 meet the above-mentioned preset requirements.

[0046] Optional, continue to see Figure 1 , along a direction parallel to the central axis of the irradiation opening 130 , a distance L between the first opening 131 and the second opening 132 satisfies: 10 mm≤L≤35 mm.

[0047] Specifically, when the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 satisfies: 10mm≤H≤30mm, the diameter D of the bottom surface of the irradiation source chamber 110 satisfies: 8mm≤D≤20mm, and the radius R of the sphere where the second surface 122 of the shielding body 120 is located satisfies: R≥35mm, the distance L between the first opening 131 and the second opening 132 along the direction parallel to the central axis of the irradiation opening 130 is set to 10mm≤L≤35mm, so as to ensure that the uniformity and scattering characteristics of the gamma radiation field formed by the portable gamma irradiation collimator 100 meet the above-mentioned preset requirements.

[0048] Optional, continue to see Figure 1 The shielding body 120 is provided with a third surface 123, and the third surface 123 is perpendicular to the second surface 122. Specifically, Figure 1 As shown, the third surface 123 is a plane, which provides a flat support surface for the portable gamma irradiation collimator 100 and improves stability.

[0049] In practical applications, the portable gamma irradiation collimator 100 is also equipped with a radiation attenuation sheet. Figure 2 A method for Figure 1 The schematic diagram of the structure of the radiation attenuation sheet of the portable γ-irradiation collimator shown in FIG. Figure 2 As shown, the radiation attenuation plate 200 includes a first surface 210 and a second surface 220 relative to each other, the first surface 210 is a circular plane, and the diameter of the first surface 210 is l; the second surface 220 includes an edge area 221 and a middle area 222, the edge area 221 is a circular plane, the middle area 222 is an arc surface, the radius of the spherical surface where the arc surface is located is o, and the vertical projection of the middle area 222 on the first surface 210 is a circle, and the diameter of the vertical projection is m; the thickness of the middle area 222 is n, and the thickness of the middle area 222 gradually decreases from the center of the middle area 222 to the edge of the middle area 222.

[0050] Specifically, Figure 2 As shown, the arc radius of the middle area 222 is o, and the arc radius o determines the speed of thickness reduction. The smaller the arc radius o, the faster the thickness decreases, and the larger the arc radius o, the slower the thickness decreases. When the arc radius o takes an appropriate value, the radiation field has optimal uniformity. For different portable gamma irradiation collimators 100, the parameters of the radiation attenuation plate 200 matched therewith are different. It should be noted that the uniformity and scattering characteristics of the gamma radiation field formed by the attenuation of the radiation attenuation plate 200 also need to meet the preset requirements.

[0051] Exemplarily, the gamma radiation source is 137 Cs radiation source, the shield 120 is made of tungsten alloy, the radius R of the sphere where the second surface 122 of the shield 120 is located is 50 mm, the height H of the side wall connecting the irradiation source chamber 110 and the irradiation opening 130 is 20 mm, and the diameter D of the bottom surface of the irradiation source chamber 120 is 12 mm. According to the uniformity and scattering characteristics of the gamma radiation field formed by the portable gamma irradiation collimator 100 meeting the preset requirements, the height W of the second opening 132 is determined to be 12 mm, the angle θ between the side wall of the irradiation opening 130 and the central axis of the irradiation opening 130 is 24.23°, and the distance L between the first opening 131 and the second opening 132 along the direction parallel to the central axis of the irradiation opening 130 is 29 mm.

[0052] Figure 3 The schematic diagram of the uniformity of the gamma radiation field formed by a portable gamma radiation collimator provided by an embodiment of the present invention. Taking the above-mentioned size parameters as the size parameters of the portable gamma radiation collimator, and taking the 100cm distance from the center of the portable gamma radiation collimator as the starting point, the gamma radiation measuring instrument moves in the horizontal direction and the vertical direction perpendicular to the axis respectively, and the measured air kerma rate attenuation change relative to the starting point is as follows: Figure 3 As shown, within a range of 15 cm from the central axis of the central axis, the radiation field intensity changes by no more than 4%. Therefore, the uniformity of the gamma radiation field formed by the portable gamma irradiation collimator corresponding to the above size parameters meets the preset requirements.

[0053] Figure 4 A schematic diagram of the scattering characteristics of a gamma radiation field formed by a portable gamma radiation collimator provided by an embodiment of the present invention. Taking the above-mentioned size parameters as the size parameters of the portable gamma radiation collimator, the gamma radiation measuring instrument moves within the range of 0.75m to 3m along the central axis of the radiation opening, and the relationship between the measured air kerma rate and the inverse square of the distance is as follows: Figure 4 As shown, the air kerma rate is proportional to the inverse of the square of the distance from the gamma radiation source to the center of the detector, and the measured value deviates from the fitting straight line by no more than 2%. Therefore, the scattering characteristics of the gamma radiation field formed by the portable gamma irradiation collimator corresponding to the above size parameters meet the preset requirements.

[0054] Taking the above-mentioned size parameters as the size parameters of the portable γ irradiation collimator, and taking the uniformity and scattering characteristics of the γ radiation field attenuated by the radiation attenuation plate to meet the preset requirements as the criterion, the size parameters of the radiation attenuation plate are obtained by Monte Carlo simulation, as shown in Table 1. Different size parameters in Table 1 correspond to different radiation attenuation plates.

[0055] Table 1 Dimensional parameters of radiation attenuation sheets

[0056]

[0057]

[0058] Compared with the prior art, the radius of the first surface of the radiation attenuation plate provided in the embodiment of the present invention is reduced by nearly 50%. Since the radiation attenuation plate is used in conjunction with a portable gamma irradiation collimator, the portability and applicability of the portable gamma irradiation collimator are improved to a certain extent.

[0059] Starting from 100cm away from the central axis of the radiation attenuation sheet, the gamma radiation measuring instrument moves in the horizontal and vertical directions perpendicular to the axis respectively. Within 15cm from the central axis, the radiation field intensity changes by no more than 3%, and the uniformity of the gamma radiation field formed by the attenuation of the radiation attenuation sheet meets the preset requirements. Along the central axis of the radiation attenuation sheet, the gamma radiation measuring instrument moves within the range of 0.75m to 3m. The air kerma rate should be proportional to the inverse of the square of the distance from the gamma radiation source to the center of the detector. The measured value deviates from the fitting straight line by no more than 3%, and the scattering characteristics of the gamma radiation field formed by the attenuation of the radiation attenuation sheet meet the preset requirements.

[0060] Based on the same inventive concept, an embodiment of the present invention also provides a design method of a portable gamma irradiation collimator, which is used to design the portable gamma irradiation collimator provided by the embodiment of the present invention, and has the corresponding functions and beneficial effects of the device.

[0061] Figure 5 A schematic diagram of a design method of a portable gamma irradiation collimator provided by an embodiment of the present invention. Figure 5 As shown, the design method of the portable gamma irradiation collimator specifically includes:

[0062] S110, constructing a gamma irradiation collimator model using Monte Carlo simulation technology.

[0063] Specifically, according to the material of the shielding body, the type of gamma radiation source and the principle that the shielding rate of gamma rays radiated by the gamma radiation source in the main shielding direction is not less than 99.9%, the radius R of the sphere where the second surface of the shielding body is located is determined; according to the size of the gamma irradiation source, the side wall height H of the irradiation source chamber connected to the irradiation opening and the diameter D of the bottom surface of the irradiation source chamber are determined; according to the determined radius R of the sphere where the second surface of the shielding body is located, the side wall height H of the irradiation source chamber connected to the irradiation opening and the diameter D of the bottom surface of the irradiation source chamber, as well as different combinations of the height W of the first opening, the angle θ between the side wall of the irradiation opening and the central axis of the irradiation opening, and the distance L between the first opening and the second opening along the direction parallel to the central axis of the irradiation opening, a gamma irradiation collimator model is constructed by Monte Carlo simulation technology.

[0064] S120, designing an orthogonal experimental table according to the Taguchi experimental design method; the orthogonal experimental table includes a combination of multiple gamma irradiation collimator model size parameters.

[0065] Specifically, in the orthogonal experimental table designed by the Taguchi experimental design method, there are fewer combinations of γ irradiation collimator model size parameters. For example, the height W of the first opening, the angle θ between the side wall of the irradiation opening and the central axis of the irradiation opening, and the distance L between the first opening and the second opening along the direction parallel to the central axis of the irradiation opening all have five different values. There are 243 combinations of changes in these parameters. There are only 25 combinations in the orthogonal test table obtained by the Taguchi experimental design method, which can reduce the amount of simulation calculations and improve work efficiency.

[0066] S130, simulating, according to the gamma irradiation collimator model, the uniformity and scattering characteristics of the gamma radiation field of the gamma irradiation collimator under different combinations of size parameters of the gamma irradiation collimator model.

[0067] S140, according to the simulation results of the Taguchi experimental design method, a combination of the size parameters of the gamma irradiation collimator model whose uniformity and scattering characteristics of the gamma radiation field meet preset requirements is selected for designing the portable gamma irradiation collimator.

[0068] Specifically, different combinations of gamma irradiation collimator model size parameters correspond to different gamma irradiation collimators. According to the gamma irradiation collimator model, the uniformity and scattering characteristics of the gamma radiation field formed by different gamma irradiation collimators are simulated, and multiple groups of simulation results are obtained. The simulation results are statistically processed according to the Taguchi experimental design method to obtain the gamma irradiation collimator model size parameter combination corresponding to the simulation results whose uniformity and scattering characteristics of the gamma radiation field meet the preset requirements, and the combination is used as the design parameter to design the portable gamma irradiation collimator. Furthermore, the gamma irradiation collimator model size parameter combination corresponding to the simulation results with the best uniformity and scattering characteristics of the gamma radiation field can be selected as the design parameter for designing the portable gamma irradiation collimator.

[0069] The embodiment of the present invention designs a portable gamma irradiation collimator by means of software simulation, which can reduce the design cost, and obtains an orthogonal experimental table by means of the Taguchi experimental design method, which can reduce the amount of simulation calculations, shorten the design cycle, and improve work efficiency.

[0070] The design method of the portable gamma irradiation collimator provided in the embodiment of the present invention also has the beneficial effects of the corresponding portable gamma irradiation collimator in the above embodiment, which will not be described in detail here.

[0071] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A portable gamma irradiation collimator, characterized in that: include: An irradiation source chamber, a shielding body and an irradiation opening; the irradiation source chamber is used to accommodate gamma irradiation sources of different sizes; The irradiation opening is used for collimating the γ rays emitted by the γ irradiation source; The radiation source chamber is located at the center of the shielding body; the radiation opening passes through the shielding body and is connected to the radiation source chamber; The uniformity and scattering characteristics of the gamma rays emitted from the irradiation opening meet preset requirements; The side of the irradiation opening facing away from the irradiation source chamber is a first opening, the surface where the shielding body and the first opening are connected is a first surface, and the first surface is parallel to the first opening; The shielding body further comprises a second surface; the second surface is connected to the first surface; the second surface is spherical; The height H of the side wall of the irradiation source chamber communicating with the irradiation opening satisfies: 10 mm ≤ H ≤ 30 mm; the diameter D of the bottom surface of the irradiation source chamber satisfies: 8 mm ≤ D ≤ 20 mm; The center of the sphere coincides with the center of the irradiation source chamber; the radius R of the sphere satisfies: R ≥ 35 mm; A side of the irradiation opening close to the irradiation source chamber is a second opening, and a height W of the second opening satisfies: 8 mm ≤ W ≤ 20 mm; An included angle θ between the side wall of the irradiation opening and the central axis of the irradiation opening satisfies: 20°≤θ≤45°.

2. The portable gamma irradiation collimator according to claim 1, characterized in that: The radiation source chamber is cylindrical; the bottom surface of the cylinder is parallel to the central axis of the radiation opening; the first surface and the radiation source chamber are symmetrically distributed along the central axis of the radiation opening.

3. The portable gamma irradiation collimator according to claim 1, characterized in that: Along a direction parallel to a central axis of the irradiation opening, a distance L between the first opening and the second opening satisfies: 10 mm≤L≤35 mm.

4. The portable gamma irradiation collimator according to claim 1, characterized in that: The shielding body material includes lead and its alloys, tungsten and its alloys or depleted uranium and its alloys.

5. A method for designing a portable gamma irradiation collimator, used for designing the portable gamma irradiation collimator according to any one of claims 1 to 4, characterized in that: include: The gamma irradiation collimator model was constructed by Monte Carlo simulation technology; An orthogonal experimental table is designed according to the Taguchi experimental design method; the orthogonal experimental table includes a combination of multiple γ-irradiation collimator model size parameters; According to the gamma irradiation collimator model, simulating the uniformity and scattering characteristics of the gamma radiation field of the gamma irradiation collimator under different combinations of size parameters of the gamma irradiation collimator model; According to the simulation results of the Taguchi experimental design method, a combination of the gamma irradiation collimator model size parameters whose uniformity and scattering characteristics of the gamma radiation field meet preset requirements is selected to design the portable gamma irradiation collimator.

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