Shielding structure applied to small linear accelerator

Abstract

The invention belongs to the technical field of irradiation shielding, and discloses a shielding structure applied to a small linear accelerator, the shielding structure comprises an upper shielding body and a lower shielding body, the upper shielding body is arranged around the accelerator; the lower shielding body is provided with an internal cavity for placing an object to be irradiated; in the shielding structure, the thicknesses of the outer walls of the local areas are different. According to the invention, the shielding effect can be ensured on the basis of saving shielding body materials.

Description

Technical Field

[0001] The invention belongs to the technical field of radiation shielding, and in particular relates to a shielding structure applied to a small linear accelerator. Background Art

[0002] The energy range of the accelerator is 0.5MeV to 3.5MeV, and the power is 0.5kW to 3kW. Considering that the electron beam generated by the accelerator will generate X-rays, and X-rays have strong penetrating power, heavy metal materials must be installed on both sides of the internal space and any area where X-rays can directly penetrate for shielding. Conventional accelerator shielding structures are mostly made of concrete, which occupies a large area; once built, it is difficult to move, and it is even more impossible to move it together with the accelerator. If the accelerator is taken out, the shield cannot be used again. Summary of the invention

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a shielding structure for a small linear accelerator. By optimizing the material and outer wall thickness of the shielding structure, the shielding structure can be more miniaturized and lightweight while ensuring the shielding effect, making transportation possible.

[0004] To achieve the above-mentioned objectives, one or more embodiments of the present invention provide a shielding structure applied to a small linear accelerator, wherein the shielding structure comprises an upper shielding body and a lower shielding body, wherein the upper shielding body is arranged around the accelerator; the lower shielding body has an internal cavity for placing an object to be irradiated; in the shielding structure, the outer wall thickness of each local area is different.

[0005] In some embodiments, the material of the shielding structure is lead, lead antimony or lead alloy.

[0006] In some embodiments, the accelerator includes an electron gun, an accelerating tube, a bellows, and a scanning box arranged from top to bottom, and a waveguide is provided on one side of the accelerating tube.

[0007] In some embodiments, the method for optimizing the thickness of the outer wall of the shielding structure is:

[0008] The analysis space range is set with the shielding structure as the center;

[0009] Set the X-ray energy value and record the point with the maximum radiation dose as the ray source point;

[0010] Setting an initial thickness of the shielding structure, and calculating the radiation dose rate received on the boundary of the analysis space under the initial thickness;

[0011] According to the irradiation dose rate threshold set for the boundary of the analysis space, the thickness of the shielding structure is optimized to ensure that the irradiation dose rate threshold is met when the ray source point reaches the boundary of the analysis space.

[0012] In some embodiments, the upper shielding body includes a shielding body body, and the inner cavity shape of the shielding body body is adapted to the accelerator; a first shielding block is provided on the upper surface of the shielding body body at a position corresponding to the accelerator electron gun; a second shielding block is provided on the outer surface of a side wall of the shielding body body at a position corresponding to the waveguide, and a third shielding block is provided at a position corresponding to the titanium pump.

[0013] In some embodiments, the lower shielding body includes a side shielding body and a bottom shielding body, and a shielding block is provided on the upper surface of the bottom shielding body for placing the object to be irradiated.

[0014] In some embodiments, the shielding block includes a plurality of stacked shielding plates of the same shape but different sizes, wherein the largest shielding plate is in contact with the bottom shielding body, and the uppermost shielding plate is used to place the object to be irradiated.

[0015] In some embodiments, at least one side surface of the lower shielding body is configured as a shielding door.

[0016] In some embodiments, guide holes are provided on both sides of the top of the shielding door, a horizontal guide rail is provided in the guide hole, the upper surface of the horizontal guide rail is a rack, and column brackets are provided on both sides of the horizontal guide rail, which are respectively located on both sides of the shielding door; the upper surface of the guide hole is open, and a gear meshing with the rack is provided in the opening, and the central axis of the gear is connected to an operating handle, and the operating handle can drive the gear to rotate in the opening.

[0017] In some embodiments, the object to be irradiated is a water box, the water box is used to store water to be irradiated, and a radiation receiving area is provided on the upper surface of the water box.

[0018] In some embodiments, a water inlet and a water outlet are provided on one side of the lower shielding body for setting a water inlet pipeline and a water outlet pipeline of the water box.

[0019] By optimizing the material and outer wall thickness of the shielding structure, the shielding structure can be made more compact and lightweight while ensuring the shielding effect, making transportation possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the drawings, the sizes and proportions do not represent the sizes and proportions of actual products. The drawings are merely illustrative, and some non-essential elements or features are omitted for clarity.

[0021] Figure 1 This is an overall schematic diagram of the radiation shielding structure in an embodiment of the present invention;

[0022] Figure 2This is a schematic diagram of the internal structure of the radiation shielding structure in an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the internal structure of the radiation shielding structure in another perspective in an embodiment of the present invention;

[0024] Figure 4 A top view of the radiation shielding structure in an embodiment of the present invention;

[0025] Figure 5 It is a three-dimensional rendering of the overall radiation shielding structure in an embodiment of the present invention;

[0026] Figure 6 Schematic diagram of the principle of optimizing the thickness of the outer wall of the radiation shielding structure in an embodiment of the present invention.

[0027] In the figure, 1, upper shielding body, 2, lower shielding body, 3, accelerator, 4, water inlet, 5, water outlet, 1-1, first shielding block, 1-2, second shielding block, 1-3, third shielding block, 2-1, bottom shielding body, 2-2, T-stage shielding block, 3-1, electron gun, 3-2, accelerating tube, 3-3, bellows, 3-4, waveguide window, 3-5, waveguide, 3-6, scanning magnet, 3-7, titanium pump, 3-8, scanning box, 6, shielding door, 7, horizontal guide rail, 8, column bracket, 9, rack, 10, gear, 11, operating handle, 12, water box. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] In the present invention, the directions or positional relationships indicated by terms such as "upper", "lower", "side", "bottom", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and cannot be understood as limitations on the present invention.

[0032] In the present invention, terms such as "connection" should be understood in a broad sense, indicating that the connection can be fixed, integral or detachable; it can be directly connected or indirectly connected through an intermediate medium. Those skilled in the art can determine the specific meaning of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0033] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0034] One or more embodiments of the present invention provide a shielding structure for a small linear accelerator 3, such as Figure 1-Figure 5 As shown, the shielding structure comprises an upper shielding body 1 and a lower shielding body 2, wherein the upper shielding body 1 is arranged around the accelerator 3; the lower shielding body 2 has an internal cavity for placing an object to be irradiated.

[0035] As an example, Figure 3 As shown, the object to be irradiated is a water box 12, which is used to store the water to be irradiated, and a radiation receiving area is provided on the upper surface of the water box 12. A water inlet 4 and a water outlet 5 are provided on one side of the lower shielding body 2, which are used to set the water inlet pipeline and the water outlet pipeline of the water box 12.

[0036] The material of the shielding structure is at least one of lead, lead antimony and lead alloy. The attenuation law of X-rays with a nominal energy of 3MeV in lead material is that it drops to 1 / 10 every 40cm. Therefore, for a dose attenuation of 7 orders of magnitude, at least 28cm of lead or lead antimony or lead alloy material is required. If the shielding material is installed according to this thickness in all X-ray radiation directions, the overall weight will reach 50 to 160 tons. Considering the thickness of the shielding layer from the source of the ray to each angle in space, some angles will be superimposed due to different channels, and some angles will increase after dividing by the cosine value of the angle, so the thickness of the shielding layer in many positions can be reduced accordingly. Based on this, in some embodiments, the shielding structure is partitioned, and the thickness of the outer wall of each local area is different.

[0037] As a specific implementation method, Figure 6 As shown, with the shielding structure as the center, the analysis space range (for example, the space within 3 meters of the irradiation area) is set; the X-ray energy value is set, and the point with the maximum irradiation dose is recorded as the ray source point; the initial thickness of the shielding structure is set, and the irradiation dose rate received on the boundary of the analysis space under the initial thickness is calculated; according to the irradiation dose rate threshold set for the boundary of the analysis space, the thickness of the shielding structure is optimized to ensure that when the ray source point reaches the boundary of the analysis space, the irradiation dose rate threshold is met. Figure 6 Middle①- For the sample point example of calculating the irradiation dose rate received on the boundary of the analysis space, if the irradiation dose rate at a certain point on the analysis boundary is greater than the set irradiation dose rate threshold, the thickness of the outer wall on the path from the ray source point to the point can be appropriately reduced. On the contrary, if the irradiation dose rate at a certain point on the analysis boundary is less than the set irradiation dose rate threshold, the thickness of the outer wall on the path from the ray source point to the point needs to be increased. As an example, the irradiation dose at the exit of the accelerating tube 3-2 is the largest, followed by the large dose irradiation reaching the top radiation receiving area of ​​the water box 12, which will reflect the X-rays. Therefore, the exit of the accelerating tube 3-2 and the top radiation receiving area of ​​the water box 12 are used as ray source points, and the top irradiation dose rate, the side irradiation dose rate and the bottom irradiation dose rate of the analysis space are set respectively, for example, set to 100μSv / h, 2.5μSv / h, and 5mSv / h respectively. After the structural optimization, the overall weight of the shielding body is between 12 and 28 tons, which has a significant decrease and meets the transportation requirements. To facilitate the processing of the shielding structure, in some embodiments, the thickness of the outer wall of the shielding structure is optimized by partitioning according to the radiation dose rate received on the analysis boundary. The areas where the shielding structures correspond to adjacent sample points with similar radiation dose rates are also similar. Therefore, a cross-overlapping design is adopted, and adjacent shielding structure areas with similar required thicknesses use a whole shielding block, which reduces the processing difficulty, reduces the overall quality of the self-shielding, and achieves effective shielding, so that the environmental radiation dose outside the self-shielding body meets the requirements of domestic and international radiation protection standards, thereby ensuring the safety of the environment and personnel.

[0038] As an example, the accelerator 3 includes an electron gun 3-1, an accelerating tube 3-2, a bellows 3-3 and a scanning box 3-8 arranged from top to bottom, and the scanning box 3-8 is surrounded by a scanning magnet 3-6. The upper shielding body 1 and the lower shielding body 2 are bounded by the scanning box 3-8 of the accelerator 3. Among them, the electron gun 3-1 is a device for generating electrons. When the gun high voltage is applied, the electrons are accelerated and injected into the accelerating tube 3-2. A waveguide 3-5 is provided on one side of the accelerating tube 3-2. A waveguide window 3-4 is provided at the connection between the accelerating tube 3-2 and the waveguide 3-5. The waveguide 3-5 is used to transmit microwave power, and the microwave power is fed into the accelerating tube 3-2 through the waveguide window 3-4. The accelerating tube 3-2 is a resonant cavity column for accelerating electrons, which can establish an alternating accelerating electric field to enable the electrons to obtain continuous acceleration. The bellows 3-3 is a component connecting the accelerating tube 3-2 and the scanning box 3-8, which is an important channel for electron beam drift, and has the function of solving thermal expansion problems and adjusting the accumulated errors during equipment installation. The scanning box 3-8 is used to provide the vacuum space required for the formation of a fan-shaped electron beam. The lower surface of the scanning box 3-8 is provided with a titanium window (50 microns thick), which can ensure vacuum while allowing electrons to pass smoothly. The titanium pump 3-7 is arranged on one side of the scanning box 3-8 to maintain the vacuum inside the accelerating tube 3-2 and the scanning box 3-8. Under the control of the triangular wave current, the scanning magnet 3-6 generates an alternating magnetic field to deflect the electrons to form a fan-shaped electron beam.

[0039] In particular, the scanning box 3-8 is a scanning box 3-8 with a built-in ion pump (for the specific structure, see patent document CN1207729C). By directly integrating the vacuum system on the scanning box 3-8, the flow resistance loss of the vacuum system can be reduced, the efficiency is high, the pumping speed is large, and at the same time, the size is small and the shape is regular, which makes it easy to perform radiation protection shielding, providing a basis for the miniaturization of the overall shielding body.

[0040] In addition, by sleeve-arranging the scanning magnet 3-6 outside the scanning box 3-8, the scanning and beam uniformity are improved, and the beam non-uniformity after scanning is less than ±5%. The scanning magnet coil is an inductive load, and the voltage waveform of the coil power supply is a square wave, so the current waveform of the scanning magnet 3-6 coil and the magnetic field distribution of the scanning magnet 3-6 can be obtained, further improving the scanning uniformity.

[0041] As a specific implementation method, Figure 3 and Figure 5As shown, the upper shielding body 1 includes a shielding body body, and the inner cavity shape of the shielding body body is adapted to the accelerator 3. For example, the inner cavity corresponding to the top of the electron gun 3-1 is provided with a groove, and the inner cavity corresponding to the transverse waveguide 3-5 is also provided with a groove. In addition, the initial outer wall thickness meets a certain threshold value, and the overall shape of the upper shielding body 1 is similar to the accelerator 3. The cross-sectional area in the height interval corresponding to the electron gun 3-1 is the smallest, and the cross-sectional area in the height interval corresponding to the accelerating tube 3-2 and the bellows 3-3 and the height interval corresponding to the scanning box 3-8 increases successively. The upper surface of the shielding body body, at the position corresponding to the electron gun 3-1 of the accelerator 3, is provided with a first shielding block 1-1; the outer surface of one side wall of the shielding body body, at the position corresponding to the waveguide 3-5, is provided with a second shielding block 1-2, and the outer surface corresponding to the titanium pump 3-7, that is, the position corresponding to the outlet of the accelerating tube 3-2 to the scanning magnet 3-6, is provided with a third shielding block 1-3. For example, the waveguide 3-5, the connecting pipe, the ventilation pipe, etc. can be buried in the upper shielding body 1 by pre-buried pipes.

[0042] like Figure 2 and Figure 3 As shown, the lower shielding body 2 includes a side shielding body and a bottom shielding body 2-1. The upper surface of the bottom shielding body 2-1 is provided with a T-stage shielding block 2-2. The T-stage shielding block 2-2 includes a plurality of flat shielding plates of the same shape and different sizes. The plurality of shielding plates are stacked from large to small at the center of the upper surface of the bottom shielding body 2-1, and the largest shielding plate is in contact with the bottom shielding body 2-1. The uppermost shielding plate is used to place the object to be irradiated.

[0043] The shielding block and shielding plate are a specific implementation method of optimizing the thickness structure of the shielding body outer wall, so that no matter where outside the accelerator 3, it can ensure that the radiation dose rate is lower than the target when it is a certain distance away from the radiation source. Based on the above structural optimization, mobile transportation becomes possible.

[0044] In order to facilitate the placement of the object to be irradiated, at least one side of the lower shielding body 2 is provided with a shielding door 6. As an example, a guide through hole is provided on both sides of the top of the shielding door 6, and a horizontal guide rail 7 is provided in the guide through hole. Both sides of the horizontal guide rail 7 are provided with a column bracket 8, which is respectively located on both sides of the shielding door 6. A rack 9 is provided on the upper surface of the horizontal guide rail 7, and the upper surface of the guide through hole is open. A gear 10 meshing with the rack 9 is provided in the opening. The central axis of the gear 10 is connected to an operating handle 11, and the operating handle 11 can drive the gear 10 to rotate in the opening; a roller guide rail mechanism is provided between the bottom of the shielding door 6 and the bottom shielding body 2-1, which is used to support the shielding door 6. Based on this, the shielding door 6 can be opened or closed under the control of the operating handle 11. In some embodiments, two opposite sides of the lower shielding body 2 are provided as shielding doors 6.

[0045] The protection scope of the present invention is limited only by the claims. With the help of the teachings of the present invention, those skilled in the art will easily recognize that alternative structures of the structures disclosed in the present invention can be used as feasible alternative embodiments, and the embodiments disclosed in the present invention can be combined to generate new embodiments, which also fall within the scope of the appended claims.

Claims

1. A shielding structure for a small linear accelerator, characterized in that: The shielding structure comprises an upper shielding body and a lower shielding body, wherein the upper shielding body is arranged around the accelerator; the lower shielding body has an internal cavity for placing an object to be irradiated; in the shielding structure, the outer wall thickness of each local area is different.

2. The shielding structure for a small linear accelerator according to claim 1, characterized in that: The material of the shielding structure is lead, lead antimony or lead alloy.

3. The shielding structure for a small linear accelerator according to claim 2, characterized in that: The accelerator comprises an electron gun, an accelerating tube, a bellows and a scanning box which are arranged from top to bottom, and a waveguide is arranged on one side of the accelerating tube.

4. The shielding structure for a small linear accelerator according to claim 3, characterized in that: The optimization method of the outer wall thickness of the shielding structure is: The analysis space range is set with the shielding structure as the center; Set the X-ray energy value and record the point with the maximum radiation dose as the ray source point; Setting an initial thickness of the shielding structure, and calculating the radiation dose rate received on the boundary of the analysis space under the initial thickness; According to the irradiation dose rate threshold set for the analysis space boundary, the thickness of the shielding structure is optimized to ensure that the irradiation dose rate threshold is met when the ray source point reaches the analysis space boundary.

5. The shielding structure for a small linear accelerator according to claim 4, characterized in that: The upper shielding body comprises a shielding body body, the inner cavity shape of which is adapted to the accelerator; a first shielding block is provided on the upper surface of the shielding body body at a position corresponding to the electron gun of the accelerator; a second shielding block is provided on the outer surface of a side wall of the shielding body body at a position corresponding to the waveguide, and a third shielding block is provided at a position corresponding to the titanium pump.

6. The shielding structure for a small linear accelerator according to any one of claims 1 to 5, characterized in that: The lower shielding body comprises a side shielding body and a bottom shielding body. The upper surface of the bottom shielding body is provided with a shielding block for placing an object to be irradiated.

7. The shielding structure for a small linear accelerator according to claim 6, characterized in that: The shielding block comprises a plurality of stacked shielding plates of the same shape but different sizes, wherein the largest shielding plate contacts the bottom shielding body, and the uppermost shielding plate is used for placing the object to be irradiated.

8. The shielding structure for a small linear accelerator according to claim 6, characterized in that: At least one side surface of the lower shielding body is arranged as a shielding door.

9. The shielding structure for a small linear accelerator according to claim 8, characterized in that: Guide holes are provided on both sides of the top of the shielding door, a horizontal guide rail is provided in the guide hole, the upper surface of the horizontal guide rail is a rack, and column brackets are provided on both sides of the horizontal guide rail, which are respectively located on both sides of the shielding door; the upper surface of the guide hole is open, and a gear meshing with the rack is provided in the opening, and the central axis of the gear is connected to an operating handle, and the operating handle can drive the gear to rotate in the opening.

10. The shielding structure for a small linear accelerator according to claim 1, characterized in that: The object to be irradiated is a water box, which is used to store the water to be irradiated. The upper surface of the water box is provided with a radiation receiving area; a side surface of the lower shielding body is provided with a water inlet and a water outlet, which are used to set the water inlet pipeline and the water outlet pipeline of the water box.

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