Head high-voltage electrode structure of tandem accelerator

Abstract

The invention belongs to the technical field of accelerators, and particularly relates to a head high-voltage electrode structure of a serial accelerator, which comprises a terminal electrode (1), a middle electrode (2) and support frames (3), the middle electrode (2) is of a hollow cylindrical structure with two open ends, the support frames (3) are respectively arranged at the two ends of the middle electrode (2), and the terminal electrode (1) is arranged on the support frames (3). By adopting a separated and assembled structure, the electric field intensity distribution on the surface of the head high-voltage electrode is effectively controlled, the local electric field intensity is prevented from being too high, meanwhile, the head high-voltage electrode can be conveniently assembled and disassembled structurally, and internal devices of the head high-voltage electrode can be conveniently maintained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of accelerators, and particularly relates to a head high-voltage electrode structure of a tandem accelerator. BACKGROUND

[0002] The accelerating tube and stripper of the tandem accelerator are placed in a steel cylinder at ground potential. The two ends of the tandem accelerator are at ground potential, the stripper is at high potential, and the accelerating tube is located on both sides of the stripper and works between high potential and ground potential.

[0003] The negative ion beam generated by the ion source is accelerated by the accelerating tube located on one side of the stripper, reaches the stripper at high potential, the polarity of the ion is converted by the stripper from a negative ion beam to a positive ion beam, and the positive ion beam is accelerated from the stripper at high potential to the other end of the accelerator at ground potential by the accelerating tube on the other side. The stripper, as an important device for converting the polarity of the ion beam, is located in the middle of the tandem accelerator and is at the highest potential during the operation of the accelerator. Usually, a smooth metal cylinder is wrapped outside the stripper. The metal cylinder is located in the middle of the tandem accelerator, but is at the highest potential of the tandem accelerator, and is therefore called a head high-voltage electrode.

[0004] The surface electric field strength of the head high-voltage electrode is usually also relatively high, and how to avoid the local electric field strength being too high is a problem that needs to be carefully considered in the design. Influenced by the ground potential steel cylinder, the head high-voltage electrode is mainly subjected to the action of the radial electric field; influenced by the acceleration potential of the axial accelerating tube, the head of the head high-voltage electrode is also subjected to the action of the axial electric field. Under the joint action of the radial and axial electric fields, the electric field strength distribution on the surface of the head high-voltage electrode will appear local electric field strength being too high at both ends. How to realize the relatively uniform electric field distribution on the surface of the head high-voltage electrode and avoid the local electric field strength being too high is an important problem faced in the design of the tandem accelerator. At the same time, since the devices inside the head high-voltage electrode, such as the stripper, need to be regularly maintained, the head high-voltage electrode must be easy to install and disassemble. SUMMARY

[0005] In view of the problems existing in the prior art, the purpose of the present application is to provide a head high-voltage electrode structure of a tandem accelerator. The separated and assembled structure is adopted to effectively control the electric field strength distribution on the surface of the head high-voltage electrode, avoid the local electric field strength being too high, and facilitate the installation and disassembly of the structure, thereby facilitating the maintenance of the devices inside the head high-voltage electrode.

[0006] In order to achieve the above-mentioned purpose of the application, the technical scheme of the present application is as follows:

[0007] The head high-voltage electrode structure of a tandem accelerator comprises end electrodes, middle electrodes and support frames, the middle electrode is a hollow cylindrical structure with both ends open, the support frame is arranged at both ends of the middle electrode respectively, and the end electrode is arranged on the support frame.

[0008] Further, the middle electrode adopts a split assembly structure and is enclosed by a plurality of circular arc surfaces.

[0009] Further, the end electrode is a tire-shaped structure, and the axial cross-sectional profile is an elliptical curve or a smooth transition spline curve.

[0010] Further, the outer surface of the back of the end electrode is polished to a mirror surface.

[0011] Further, the inner surface of the end electrode is provided with a plurality of reinforcing strips along the circumference.

[0012] Further, the reinforcing strip is provided with a fixed screw hole a, which is a threaded hole for being fixed with the support frame through a screw.

[0013] Further, the reinforcing strip is fixed on the end electrode by welding.

[0014] Further, the support frame is a ring-shaped structure, a fixed screw hole c is arranged along the circumference at one end close to the middle electrode, the fixed screw hole c is a threaded hole for being fixed with the middle electrode through a screw, a fixed screw hole b is arranged along the circumference at one end away from the middle electrode, the fixed screw hole b is a threaded hole for being fixed with the accelerator tube support frame through a screw, a fixed screw hole a is arranged along the circumference at the middle part of the support frame, the fixed screw hole a is a threaded hole for being fixed with the end electrode through a screw, and a plurality of through holes are arranged as air holes along the circumference at the middle part of the support frame.

[0015] Further, the two ends of the middle electrode are respectively provided with a fixed screw hole c along the circumference, the fixed screw hole c is a threaded hole for being fixed with the support frame through a screw, and the air hole is in the shape of an oblong.

[0016] Further, the middle electrode, the end electrode and the support frame are all made of aluminum alloy.

[0017] Further, the outer diameter of the middle electrode is smaller than the maximum outer diameter of the end electrode.

[0018] The beneficial effects of the present application are as follows:

[0019] 1. The split assembly structure is adopted to effectively control the surface electric field intensity distribution of the head high-voltage electrode, avoid the local electric field intensity being too high, and facilitate installation and disassembly on the structure, and facilitate maintenance of the internal devices of the head high-voltage electrode. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1A schematic diagram of the head high-voltage electrode structure of a tandem accelerator

[0021] Figure 2 A schematic diagram of the head high-voltage electrode structure of a 2x3MV tandem accelerator

[0022] Figure 3 A sectional view of the end electrode structure

[0023] Figure 4 A schematic diagram of the end electrode structure

[0024] Figure 5 A comparison diagram of the surface electric field intensity of a cylindrical head electrode and a combined head electrode under a 3MV head voltage load.

[0025] In the above figures, 1, end electrode; 2, intermediate electrode; 3, support frame; 4, fixed screw hole a; 5, fixed screw hole b; 6, fixed screw hole c; 7, reinforcing strip. DETAILED DESCRIPTION

[0026] The present application will be described in detail below with reference to the accompanying drawings and examples.

[0027] A head high-voltage electrode structure of a tandem accelerator, comprising an end electrode 1, an intermediate electrode 2 and a support frame 3, the intermediate electrode 2 being a hollow cylindrical structure with both ends open, the support frame 3 being arranged at both ends of the intermediate electrode 2 respectively, and the end electrode 1 being arranged on the support frame 3.

[0028] The specific technical solutions are as follows:

[0029] The present application is a head high-voltage electrode structure of a tandem accelerator, as shown in Figure 1 The negative ion beam enters the accelerator from the accelerating tube at one end of the tandem accelerator, is converted into a positive ion beam by the stripper at a high potential, and then the positive ion beam is accelerated to ground potential by the accelerating tube at the other end.

[0030] The head high-voltage electrode is located outside the stripper and mainly consists of an end electrode 1, an intermediate electrode 2 and a support frame 3. The end electrode 1, the intermediate electrode 2 and the support frame 3 are all made of aluminum alloy material, which can reduce the weight of the head high-voltage electrode and ensure good electrical conductivity. The intermediate electrode 2 is a hollow cylindrical structure with two open ends, the support frame 3 is a ring structure, and the end electrode 1 is a tire-like structure. The support frame 3 is arranged at the two ends of the intermediate electrode 2, and the fixed screw holes c6 are arranged on the circumferences of the support frame 3 close to the intermediate electrode 2 and the two ends of the intermediate electrode 2. The fixed screw holes c6 arranged on the circumferences of the support frame 3 close to the intermediate electrode 2 correspond to the fixed screw holes c6 arranged on the circumferences of the two ends of the intermediate electrode 2. The fixed screw holes c6 are threaded holes, and the support frame 3 and the intermediate electrode 2 are fixed by screws. The fixed screw holes b5 are arranged on the circumferences of the support frame 3 away from the intermediate electrode 2, and the fixed screw holes b5 are threaded holes for fixing the support frame 3 and the accelerating tube support by screws. The fixed screw holes a4 are arranged on the circumferences of the middle part of the support frame 3. The inner surface of the end electrode 1 facing the center is provided with a plurality of reinforcing strips 7 arranged along the circumferences and parallel to the axial direction. Each reinforcing strip 7 is provided with a fixed screw hole a4, and the fixed screw holes a4 on the reinforcing strips 7 arranged along the circumferences correspond to the fixed screw holes a4 arranged on the middle part of the support frame 3. The fixed screw holes a4 are threaded holes, and the end electrode 1 and the support frame 3 are fixed by screws. A plurality of through holes are arranged on the middle part of the support frame 3 as air holes, which are long oval in shape, facilitating the communication between the inside of the end electrode 1 and the outside, and reducing the weight of the support frame 3. The outer surface of the end electrode 1 away from the center is polished to a mirror surface. The axial cross-sectional profile of the end electrode 1 is an elliptical curve or a smooth spline curve, which can be designed separately according to the structure of the accelerator to minimize the surface electric field intensity of the end electrode 1. For a real end electrode profile simulation, the final goal is to realize that the surface electric field intensity of the end electrode is less than the breakdown electric field intensity. However, general partial ellipse or circular cross-section cannot obtain satisfactory results. In the real simulation process, multiple circular arcs or elliptical lines with different parameters are often used to form the cross-sectional profile of the end electrode, and these circular arcs or elliptical lines are smoothly connected to each other at the junction, which is a spline curve. In addition to obtaining the optimal simulation result, in practice, the difficulty of processing also needs to be considered. In the embodiment of the present application, a partial elliptical cross-sectional structure is adopted, and the surface electric field intensity of the end electrode is far less than the breakdown electric field intensity under the required working parameters, and it is also relatively easy to realize in processing. The outer surface radius of the intermediate electrode 2 is less than the maximum outer surface radius of the end electrode 1, and the surface electric field intensity of the intermediate electrode 2 is significantly lower than that of the end electrode 1. The outer diameter of the end electrode 1 is greater than the outer diameter of the intermediate electrode 2, thereby providing a certain shielding protection for the intermediate electrode 2, especially for the end part of the intermediate electrode 2, reducing the local electric field intensity of the end part of the intermediate electrode 2, and thereby reducing the processing and manufacturing difficulty of the intermediate electrode 2.The intermediate electrode 2 can further adopt a split combination structure, and is formed by a plurality of cylindrical curved surfaces with the same radius and the same length along the axis to form a hollow cylindrical structure. When the stripper needs to be maintained, only one or more cylindrical curved surfaces need to be removed to maintain the equipment inside the intermediate electrode 2, such as the stripper.

[0031] Embodiment

[0032] The head high-voltage electrode structure of the 2x3 MV tandem accelerator according to the application is shown in Figure 2 The head high-voltage electrode of the 2x3 MV tandem accelerator is composed of end electrodes 1, an intermediate electrode 2 and a support frame 3. The end electrodes 1 are two, which are distributed at both ends of the intermediate electrode 2 in the high-voltage area, and the cross-sectional (along the axial direction) profile is an elliptical structure. The intermediate electrode 2 is composed of two metal semi-cylindrical cylinders.

[0033] The end electrode 1 is fixed on the support frame 3 through the fixing screw hole a4, and the intermediate electrode 2 is fixed on the support frame 3 through the fixing screw hole c6. The support frame 3 is fixed on the accelerating tube support on both sides through the fixing screw hole b5.

[0034] When the stripper needs to be maintained, the end electrode 1 does not need to be disassembled, and only the screw on the fixing screw hole c6 needs to be loosened to disassemble the intermediate electrode 2 alone to maintain the equipment inside the electrode.

[0035] The diameter of the intermediate electrode 2 is 710 mm, and the length is 230 mm. The end electrode 1 is a tire-like structure, and the structure of the end electrode 1 is shown in Figure 3 and Figure 4 The profile of the end electrode 1 along the axial direction is an elliptical structure, the outer surface is polished to a mirror surface, the maximum outer diameter along the radial direction is 814 mm, the inner diameter (the minimum diameter is 670 mm) of the end electrode 1, the width along the axial direction is 200 mm, and the inner surface of the end electrode 1 is welded with a reinforcing strip 7 along the circumference. The reinforcing strip 7 is arranged in parallel to the axial direction, and a threaded hole is left on each reinforcing strip 7, which can be fixed with the support frame 3 through the fixing screw hole a4.

[0036] The diameter of the intermediate electrode 2, that is, the outer diameter of the cylindrical cylinder of the intermediate electrode 2, is smaller than the maximum outer diameter of the end electrode 1. The shielding effect of the end electrode 1 on the electric field near it will greatly weaken the electric field strength at the end of the intermediate electrode 2. The COMSOL multi-physical field simulation software is used for simulation calculation, and the calculation result is shown in Figure 5The highest electric field intensity of the accelerator is 291KV / cm at the two ends of the head electrode, and the electric field intensity of the corona ring at the two ends of the head electrode is also relatively high (179.7KV / cm) when the general cylindrical electrode is used under the same 3MV head voltage loading. When the combined mode of the end electrode and the middle electrode is used, the highest electric field intensity of the head electrode can be reduced to 173KV / cm under the premise of reaching the same internal electrode space and without increasing the size of the external steel cylinder after optimization, and the electric field intensity of the corona ring near the end electrode is also reduced to a certain extent (167.7KV / cm) due to the shielding effect of the end electrode.

[0037] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A high-voltage electrode structure at the head of a tandem accelerator, characterized in that: It includes an end electrode (1), an intermediate electrode (2) and a support frame (3). The intermediate electrode (2) is a hollow cylindrical structure with openings at both ends. The support frame (3) is respectively disposed at both ends of the intermediate electrode (2). The end electrode (1) is disposed on the support frame (3).

2. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 1, characterized in that: The intermediate electrode (2) adopts a split assembly structure, which is composed of multiple arc surfaces.

3. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 1, characterized in that: The end electrode (1) has a tire-shaped structure, and its axial profile is an elliptical curve or a smoothly transitioning spline curve.

4. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 3, characterized in that: The outer surface of the terminal electrode (1) is polished to a mirror finish.

5. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 4, characterized in that: The inner surface of the end electrode (1) is provided with several reinforcing strips (7) along the circumference.

6. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 5, characterized in that: The reinforcing strip (7) is provided with a fixing screw hole a (4), which is a threaded hole used to fix it to the support frame (3) by screws.

7. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 5, characterized in that: The reinforcing strip (7) is fixed to the end electrode (1) by welding.

8. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 1, characterized in that: The support frame (3) is a ring structure. A fixing screw hole c (6) is provided along the circumference at one end near the middle electrode (2). The fixing screw hole c (6) is a threaded hole used to fix the middle electrode (2) with screws. A fixing screw hole b (5) is provided along the circumference at the other end away from the middle electrode (2). The fixing screw hole b (5) is a threaded hole used to fix the accelerator tube support with screws. A fixing screw hole a (4) is provided along the circumference in the middle of the support frame (3). The fixing screw hole a (4) is a threaded hole used to fix the end electrode (1) with screws. Several through holes are provided along the circumference in the middle of the support frame (3) as ventilation holes.

9. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 8, characterized in that: The two ends of the intermediate electrode (2) are respectively provided with fixing screw holes c (6) along the circumference. The fixing screw holes c (6) are threaded holes used to fix the support frame (3) with screws. The vent hole is an elongated ellipse shape.

10. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 1, characterized in that: The intermediate electrode (2), the end electrode (1), and the support frame (3) are all made of aluminum alloy.

11. The high-voltage electrode structure at the head of a tandem accelerator as described in claim 3, characterized in that: The outer diameter of the intermediate electrode (2) is smaller than the maximum outer diameter of the end electrode (1).

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