Conversion target device and target material layer structure

Abstract

The present invention provides a conversion target device, which includes an upper frame, a target material layer, a cooling cavity frame and a sealing layer, wherein the upper frame fixes the target material layer to the cooling cavity frame; the sealing layer is fixedly connected to the cooling cavity frame, the target material layer, the cooling cavity frame and the sealing layer form a cooling cavity, and the cooling cavity includes an inlet and an outlet for a cooling liquid; wherein the target point of the target material layer is set to be conical; the present invention also provides a target material layer structure, which includes a target point position, and when an electron beam interacts with the target point position of the target material layer structure, X-rays are generated; the target material layer at the target point position is conical. The present invention optimizes the planar target structure to improve the conversion efficiency of the target, the irradiation dose distribution and the heat dissipation effect of the target.

Description

Technical Field

[0001] The embodiments of the present invention relate to a conversion target device and a target material layer structure. Background Art

[0002] In the field of irradiation processing, X-rays, gamma rays and electron beams are usually used as radiation sources for processing and production. Compared with the three radiation sources, X-ray sources have the advantages of strong penetration of gamma rays and good directionality, high radiation intensity, high efficiency and good safety of accelerator electron sources. The advantages of X-ray sources are more obvious when irradiating objects with large thickness and density. The X-ray generating devices used for irradiation processing can be mainly divided into two categories, namely, radioactive nuclide decay and the use of high-energy electron beams to generate X-rays; for example, in common electron linear accelerators, the emission rate of X-rays generated by the electron beam output by the accelerator is related to factors such as electron energy, beam intensity, target material atomic number and target thickness, and different dose distributions are formed in space with different energies. At present, X-rays have been widely used in many fields such as agriculture, industry, medicine, and scientific research.

[0003] In the traditional design of X-ray conversion targets, the research focuses on the material selection of the conversion target, the thickness of the target material, and the heat dissipation structure of the target. However, the optimization of the target material and thickness does not significantly improve the conversion efficiency. Therefore, it is necessary to optimize the structural design of the target to improve the conversion efficiency of X-rays and improve the dose distribution, while improving the heat dissipation capacity of the target. In the prior art, the conversion target design has the following disadvantages:

[0004] (1) The conversion target is usually a single-layer or multi-layer planar target design. When the high-energy electron beam vertically bombards the heavy metal conversion target, some electrons will be reflected back due to elastic collision, resulting in low utilization of the electron beam and thus low conversion efficiency of the conversion target;

[0005] (2) As the energy of the electron beam increases, the non-uniformity of the X-ray irradiation dose generated when vertically bombarding the heavy metal conversion target increases; generally speaking, when the electron energy is lower than 1 MeV, the direction of the maximum X-ray emission rate tends to be perpendicular to the incident direction of the electron beam; as the electron energy increases, the direction of the maximum emission rate tends to be in the direction of the incident electron beam;

[0006] (3) When a high-energy electron beam vertically bombards a heavy metal conversion target, if the conversion target is a flat design, it is easy to cause the target points to be concentrated within a radius of several millimeters, resulting in a small heat dissipation area and concentrated heat. Therefore, the heat dissipation effect is poor, which can easily cause damage to the conversion target and reduce its service life. Summary of the invention

[0007] In order to solve at least one aspect of the above technical problems, an embodiment of the present invention provides a conversion target device and a target material layer structure, which optimizes the planar target structure to improve the conversion efficiency of the target, the irradiation dose distribution and the heat dissipation effect of the target.

[0008] According to one aspect of the present invention, there is provided a conversion target device, comprising an upper frame, a target material layer, a cooling chamber frame and a sealing layer, wherein the upper frame fixes the target material layer to the cooling chamber frame; the sealing layer is fixedly connected to the cooling chamber frame, the target material layer, the cooling chamber frame and the sealing layer form a cooling chamber, and the cooling chamber comprises an inlet and an outlet for a cooling liquid; wherein the target point of the target material layer is arranged to be conical.

[0009] In a preferred embodiment, the angle between the generatrix of the cone and the normal line is no greater than 20°.

[0010] Preferably, the thickness of the target material layer at the apex of the cone is not less than the thickness of other parts of the target material layer.

[0011] Preferably, the taper of the target material layer is formed so that the taper is located at a part of the outer wall of the cooling cavity.

[0012] Preferably, the target material layer, the cooling chamber frame and the sealing layer are sealed and connected.

[0013] According to another aspect of the present invention, a target material layer structure is provided, wherein the target material layer structure includes a target point position, and when the electron beam interacts with the target point position of the target material layer structure, X-rays are generated; the target material layer at the target point position is conical.

[0014] In this preferred embodiment, the angle between the generatrix of the cone and the normal line is no greater than 20°.

[0015] Preferably, the thickness of the target material layer at the apex of the cone is not less than the thickness of other parts of the target material layer.

[0016] Preferably, the thickness of the cone surface is greater than the stroke of the electron beam in the incident direction.

[0017] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0018] (1) The present invention sets the target point into a cone shape, which can effectively reduce the reflection loss rate of the incident electrons and improve the utilization rate of the electron beam, thereby improving the conversion efficiency of the conversion target;

[0019] (2) The target point is set to be cone-shaped in the present invention, forming a certain angle with the electron incident direction, which is conducive to reducing the unevenness of the irradiation dose distribution;

[0020] (3) The present invention sets the target point into a cone shape, which can effectively increase the contact area between the target point and the coolant, avoid heat concentration at the target point, and thus enhance the heat dissipation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other objects and advantages of the present invention will become apparent from the following description of the present invention with reference to the accompanying drawings, which will help to provide a comprehensive understanding of the present invention.

[0022] Figure 1 is a sectional front view of a conversion target device according to an embodiment of the present invention;

[0023] Figure 2 is a three-dimensional side sectional view of a conversion target device according to an embodiment of the present invention;

[0024] Figure 3 The dose normalization values ​​and horizontal dose distribution diagrams of a planar target and a target according to an embodiment of the present invention at a distance of 1 meter from the target point are shown.

[0025] Description of the drawings: 1-upper frame, 2-target material layer, 3-cooling chamber, 4-cooling chamber frame, 5-cooling liquid inlet, 6-cooling liquid outlet, 7-sealing layer, 8-target point, 9-bolt hole.

[0026] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0029] like Figure 1 As shown in or 2, a conversion target device according to an embodiment of the present invention includes an upper frame 1, a target material layer 2, a cooling chamber frame 4 and a sealing layer 7, wherein the upper frame 1 fixes the target material layer 2 to the cooling chamber frame 4; the sealing layer 7 is fixedly connected to the cooling chamber frame 4, the target material layer 2, the cooling chamber frame 4 and the sealing layer 7 form a cooling chamber 3, and the cooling chamber 3 includes an inlet 5 and an outlet 6 for a cooling liquid; wherein the target point 8 of the target material layer 2 is arranged to be conical.

[0030] In this embodiment, the target point 8 of the target material layer 2 is set to be conical, so that the electrons bombarding the target form an angle with the conical surface in the incident direction compared to the plane target. When the incident electron interacts with the target point 8, the following situations may exist: (1) the incident electron and the target collide inelastically (specifically, the electron and the extranuclear electron of the material collide inelastically), the electron loses energy, is deposited on the target body in the form of ionization energy loss, and is finally converted into heat energy; (2) the incident electron and the target collide inelasticly (specifically, the electron and the atomic nucleus of the material collide inelasticly), the energy loss of the electron is scattered in the form of X-rays, that is, Bremsstrahlung X-rays; (3) when the incident electron interacts with one of the conical surfaces, the electron is scattered, and the scattered electrons continue to interact with the other surface of the conical surface and generate X-rays. Therefore, compared with the plane target, the conical target greatly reduces the amount of electron beam reflection loss, thereby improving the utilization rate of electron beam energy, which is conducive to improving the conversion efficiency of the conversion target. At the same time, the conical design increases the effective area between the electron beam and the target, that is, expands the heat load area, which is beneficial to heat dissipation.

[0031] The angle between the cone's generatrix and the normal is no greater than 20°. When the incident electron beam vertically bombards the target, if the angle between the cone's generatrix and the normal is too small, it is difficult for the cone surface and the incident electrons to form an angle, and the electrons are likely to act on the apex of the cone, so that the cone surface part other than the apex will not be utilized, and it is easy to cause the concentrated heat dissipation of the electrons at the cone apex; if the angle between the cone's generatrix and the normal is too large, when the electrons act on the cone surface, the scattered part is not easy to continue to act on the cone surface (or the electrons are directly reflected), thereby reducing the utilization rate of the electron beam.

[0032] In addition, the thickness of the target material layer at the apex of the cone is not less than the thickness of other parts of the target material layer. Since part of the incident electron beam acts on the apex of the cone, the contactable area of ​​the target point at this position is small, which is easy to cause heat concentration. The thickness of the target material layer at the apex of the cone is set to be not less than the thickness of other parts of the target material layer, which can avoid the problem of damage to the target structure due to heat concentration; and if the thickness is small, the yield of stray electrons is large, which is not conducive to improving the conversion efficiency.

[0033] In addition, the tapered shape of the target material layer 2 forms a part of the outer wall of the cooling cavity 3. As mentioned above, the target material layer 2, the cooling cavity frame 4 and the sealing layer 7 form the cooling cavity 3, that is, the target material layer 2 serves as a part of the outer wall of the cooling cavity 3. Figure 2 As shown, the cone of the target material layer 2 forms a part of the outer wall of the cooling cavity 3, and the cone surface of the cone faces the direction close to the electron incidence, and the apex of the cone faces away from the electron incidence, that is, the apex of the cone extends toward the inside of the cooling cavity 3.

[0034] Furthermore, the cooling chamber 3 is used to contain cooling liquid, so that when the electron beam acts on the target material layer 2, the cooling liquid can promptly take away the generated heat, improve the heat dissipation efficiency, and thus extend the service life of the target material layer 2. Figure 1 As shown in Figure 2, the cooling chamber frame 4 is provided with an inlet 5 and an outlet 6 for cooling liquid, which are arranged relative to each other, so that the cooling liquid can flow in and out at a certain flow rate, thereby forming a cooling circulation system and improving the heat exchange efficiency. Since the target point of the target material layer 2 is arranged in a cone shape, the area in contact with the cooling liquid at the target point is a cone surface, which increases the heat dissipation area, is conducive to quickly reducing the temperature at the target point, thereby protecting the target material layer 2 from high temperature erosion and increasing its working life.

[0035] In this embodiment, the target material layer 2, the cooling chamber frame 4 and the sealing layer 7 are sealed and connected. The sealing connection can be fixed by bolts or other methods. The conversion target device is arranged to be fixedly connected to each separate structure, which is convenient for debugging, installation, detection and maintenance of the conversion target.

[0036] like Figure 2 As shown, the conversion target device according to an embodiment of the present invention comprises an upper frame 1, a target material layer 2, a cooling cavity frame 4 and a sealing layer 7. The conversion target device is a cylindrical structure as a whole. Specifically, the upper frame 1 is an annular structure, and bolt holes 9 are arranged on the circumference of the annular structure. The upper frame 1 fixes the target material layer 2 to the cooling cavity frame 4 through bolts; the target material layer 2 is a circular plate with a certain thickness, and the central target point position of the circular plate is conical; the target material layer 2, the cooling cavity frame 4 and the sealing layer 7 are sealed and connected in sequence from top to bottom, so that the target material layer 2, the cooling cavity frame 4 and the sealing layer 7 form a cooling cavity 3, and the cooling cavity 3 is formed by the target material layer 2, the cooling cavity frame 4 and the sealing layer 7. The cooling chamber 3 forms a cavity with a cylindrical space, and an inlet 5 and an outlet 6 for the cooling liquid to enter and exit are arranged on the circumferential outer wall of the cooling chamber 3, and the inlet 5 and the outlet 6 are symmetrically arranged relative to the center of the circle; further, the conical target point of the target material layer 2 serves as a part of the outer wall of the cooling chamber 3, and the apex of the cone extends toward the inside of the cooling chamber 3, and the apex of the cone is located on the same straight line as the inlet 5 and the outlet 6, so that the cooling liquid can take away the heat at the target point in time during the flow process to achieve heat dissipation; wherein, the inlet 5 and the outlet 6 can have a circular caliber, and the size of the caliber is set corresponding to the flow rate of the liquid.

[0037] Furthermore, the target material of the target material layer 2 can be selected from metals with high atomic numbers and high melting points, such as tungsten, gold, lead, tantalum, etc., which can improve the conversion efficiency of the conversion target on the one hand and improve the high temperature resistance of the target on the other hand. In contrast, the sealing layer 7 can be selected from lightweight materials, such as stainless steel, etc.

[0038] According to another embodiment of the target material layer structure of the present invention, the target material layer structure includes a target point position, and when the electron beam interacts with the target point position of the target material layer structure, X-rays are generated; the target material layer at the target point position is conical.

[0039] In this embodiment, the angle between the generatrix of the cone and the normal line is no greater than 20°.

[0040] Furthermore, the thickness of the target material layer at the apex of the cone is not lower than the thickness of other portions of the target material layer.

[0041] In addition, the thickness of the cone surface is greater than the stroke of the electron beam in the incident direction. As the target thickness increases, the electrons interact more fully with the target material, and the total photon yield increases, which is beneficial to improving the conversion efficiency of the target.

[0042] According to the conversion target device of the embodiment of the present invention, the target point is set to be cone-shaped, which can effectively reduce the reflection loss rate of the incident electrons and improve the utilization rate of the electron beam, thereby improving the conversion efficiency of the conversion target; at the same time, the incident electrons form a certain angle with the cone, which is beneficial to improving the problem of uneven distribution of the irradiation dose; and the target point is cone-shaped, which can effectively increase the contact area between the target point and the coolant, avoid concentrated heat at the target point, and thus enhance the heat dissipation effect.

[0043] According to a preferred embodiment of the present invention, the effects of the planar target and the conical target are compared. The target materials are both heavy metal tungsten targets, the planar target is set as target 1, and the conical target is set as target 2. The structural parameters are shown in the following table:

[0044]

[0045] Target 1 and target 2 were bombarded with a 9MeV electron beam under the same operating conditions to make the conversion targets generate X-rays, and the conversion efficiency, energy spectrum, dose distribution, etc. of the X-rays generated by them were compared.

[0046] The energy distribution of X-rays generated by the conversion targets was simulated and calculated using a Monte Carlo program (or FLUKA program). The results showed that the energy distribution of X-rays generated by target 2 was significantly higher than that of target 1. The calculations showed that the effective conversion efficiency of X-rays using target 1 was about 10%, while the effective conversion efficiency of X-rays using target 2 was more than 15% higher than that of target 1. That is, the conversion efficiency of X-rays can be significantly improved by performing the target point cone optimization of the above embodiment on the planar target.

[0047] Furthermore, the radiation dose distributions generated by targets 1 and 2 are compared. For the radiation dose distribution of target 1, the radiation distribution is highly uneven in the target area, with X-rays mostly concentrated at the center of the target, while the distribution at the peripheral positions is less and more dispersed; while for the radiation dose distribution of target 2, compared with target 1, the radiation dose distribution is more uniform, and the uniform distribution of radiation reflects the effective utilization of the target area.

[0048] Figure 3 : The normalized dose value and horizontal dose distribution diagram at 1 meter away from the target point. By comparison, it can be seen that the maximum normalized dose of target 2 is 1.7 times that of target 1. It can be seen that the conversion target of the embodiment of the present invention can significantly improve the conversion efficiency of X-rays.

[0049] In addition, the heat dissipation effects of the structures of target 1 and target 2 are compared. Since target 2 sets the target point into a cone, the contact area between the cone and the cooling liquid is increased by more than 3 times compared with the flat target. Therefore, the use of a conical target can significantly enhance the heat dissipation effect, and based on the good heat dissipation of the target layer, it is beneficial to extend the service life of the target.

[0050] Regarding the embodiments of the present invention, it should also be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0051] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A conversion target device, comprising an upper frame, a target material layer, a cooling chamber frame and a sealing layer, in, The upper frame fixes the target material layer to the cooling chamber frame; The sealing layer is fixedly connected to the cooling chamber frame, the target material layer, the cooling chamber frame and the sealing layer form a cooling chamber, and the cooling chamber includes an inlet and an outlet for a cooling liquid; The target point of the target material layer is set to be cone-shaped; the cone of the target material layer is formed so that the cone is located at a part of the outer wall of the cooling cavity; the cooling cavity frame is provided with an inlet and an outlet for cooling liquid, and the inlet and the outlet are arranged oppositely; The apex of the cone extends toward the interior of the cooling cavity, and the apex of the cone is located on the same straight line as the inlet and the outlet; The conversion target device is a cylindrical structure as a whole, the cavity of the cooling cavity forms a cylindrical space, and the inlet and the outlet are symmetrically arranged relative to the center of the circle.

2. The conversion target device according to claim 1, wherein: The angle between the generatrix of the cone and the normal line is no greater than 20°.

3. The conversion target device according to claim 1, wherein: The thickness of the target material layer at the apex of the cone is not less than the thickness of other portions of the target material layer.

4. The conversion target device according to claim 1, wherein: The target material layer, the cooling chamber frame and the sealing layer are sealed and connected.

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