Fan-shaped magnet of superconducting separation fan-shaped isochronous particle cyclotron

Abstract

A fan-shaped magnet of a superconducting separation fan-shaped isochronous particle cyclotron comprises a pair of upper and lower fan-shaped magnetic poles (1), two groups of arc-shaped magnet exciting coil winding columns (2) connected with the outer surfaces of the pair of fan-shaped magnetic poles, and two groups of magnet exciting coils (3) made of superconducting materials and wound on the two groups of winding columns respectively, the two fan-shaped magnetic conductive plates (4) are connected with the outer end faces of the two groups of winding columns respectively, and each liquid refrigerant storage pool frame, the corresponding magnetic pole and the corresponding magnetic conductive plate form a liquid refrigerant storage pool containing the corresponding winding column and a magnet exciting coil. And the two liquid refrigerant storage pools are respectively connected with an upper support arm and a lower support arm of the C-shaped magnet yoke (8) through a heat insulation pad (7) to form a superconducting fan-shaped magnet. According to the superconducting fan-shaped magnet arranged in this way, the arc-shaped winding columns arranged from large radius to small radius and the excitation coil independently supplying power can form a gradient magnetic field between the upper magnetic pole and the lower magnetic pole.

Description

Technical Field

[0001] "A superconducting separated sector isochronous particle cyclotron accelerator sector magnet" is specially made for tumor radiotherapy. Background Art

[0002] For the "separated sector isochronous particle cyclotron", the main magnetic field is established between the upper and lower poles of each sector magnet. Each pole uses a main excitation coil and several auxiliary coils. A magnetic field gradient is established from a large radius to a small radius between the poles. A large number of shimming coils are used on the surface of each pole. Whether only one set of excitation coils can play the functions of the main excitation coil and the auxiliary coil, as well as the shimming coil, is a topic worth exploring. Summary of the invention

[0003] The present invention transforms the excitation mechanism of the traditional isochronous cyclotron sector magnet, dividing the traditional sector coil winding column into a number of arc-shaped winding columns, each winding column is wound with an excitation coil. Since the sum of the cross-sectional areas of the several arc-shaped winding columns is smaller than the surface area of ​​the sector winding column, the magnetic flux will be reduced; furthermore, the reduction in the number of turns of each excitation coil will reduce the excitation capacity. To this end, making the excitation coil superconducting can greatly increase the current density of the excitation coil, and then increase the ampere-turns of the excitation coil. Placing the several arc-shaped winding columns in an ultra-low temperature environment can also increase the magnetic flux density of the arc-shaped winding columns, thereby increasing the overall magnetic flux of the several arc-shaped winding columns. The specific contents of the invention are as follows: The beginning of a separated sector-shaped isochronous particle cyclotron accelerator sector-shaped magnet is a pair of upper and lower sector-shaped magnetic poles with the same shape in top view and mirror-symmetric relative to a horizontal central plane.

[0004] Furthermore, two groups of arc-shaped excitation coil windings are provided, one group is connected to the upper surface of the upper magnetic pole, and the other group is connected to the lower surface of the lower magnetic pole.

[0005] Furthermore, two groups of excitation coils made of superconducting materials are provided, one group is wound on the upper arc-shaped excitation coil winding column, and the other group is wound on the lower arc-shaped excitation coil winding column.

[0006] Furthermore, two magnetic conductive plates similar to the pole sector surface are provided, one connected to the upper end surface of an upper group of arc-shaped excitation coil winding columns, and the other connected to the lower end surface of a lower group of arc-shaped excitation coil winding columns.

[0007] Furthermore, two upper and lower opened liquid refrigerant storage pool frames are provided, which are respectively connected to the upper and lower magnetic poles and the vertical end faces of the magnetic conductive plate to form two liquid refrigerant storage pools.

[0008] Furthermore, two liquid refrigerant pipelines are provided, one of which is connected to the upper liquid refrigerant storage tank, and the other is connected to the upper and lower liquid refrigerant storage tanks.

[0009] Furthermore, two insulation plates similar to the pole sector surfaces are provided, one connected to the upper surface of the upper magnetic conductive plate, and the other connected to the lower surface of the lower magnetic conductive plate.

[0010] Furthermore, a C-shaped magnetic yoke is provided, and the upper and lower inner surfaces of the two arms of the C-shaped magnetic yoke are respectively connected to the upper and lower outer surfaces of the two insulation plates.

[0011] The superconducting sector magnet arranged as above, the arc-shaped excitation coil winding column arranged from large radius to small radius and the independently powered excitation coil can form a gradient magnetic field between the upper and lower magnetic poles. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 , Schematic diagram of sector magnetic poles Figure 2 , schematic diagram of sector-shaped magnetic poles and arc-shaped excitation coil winding Figure 3 , Schematic diagram of arc radius of arc excitation coil around column Figure 4 , schematic diagram of sector poles, arc windings and excitation coils Figure 5 , Schematic diagram of establishing gradient magnetic field Figure 6 , schematic diagram of sector poles, arc windings, excitation coils and magnetic plates Figure 7 , schematic diagram of sector-shaped magnetic poles, arc-shaped winding columns, excitation coils, magnetic guide plates and liquid refrigerant storage tanks Figure 8 , Schematic diagram of superconducting sector magnet Symbols in the figure: 1. Sector-shaped magnetic poles 2. Arc-shaped excitation coil winding 3. Excitation coil 4. Magnetic plate 5. Liquid refrigerant storage tank frame 6. Liquid refrigerant pipeline 7. Insulation pad 8. C-shaped yoke 100. Symmetry lines of sector-shaped magnetic poles from a bird's-eye view 200. The center of the arc excitation coil around the column 300. The br curve A formed by each set of arc-shaped excitation coil winding column and excitation coil 400. br curve B synthesized from br curves A DETAILED DESCRIPTION

[0013] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Without violating the scope of the present invention, the present invention is not limited by the specific embodiments disclosed below.

[0014] This embodiment is a sector magnet of a separation sector isochronous particle cyclotron.

[0015] like Figure 1 As shown, this embodiment includes a pair of phases with the same shape when viewed from above. The upper and lower sector-shaped magnetic poles 1 are mirror-symmetrical to the horizontal center plane.

[0016] There is a central plane in the sector magnet 1, and the magnetic field is upward to this plane. The plane is located at the geometric center between the upper and lower sector magnetic poles 1. The emphasis on mirror symmetry indicates that a pair of sector magnetic poles 1 have not only the same shape when viewed from above, but also the same thickness. The center plane is an important concept and will be used many times in the following descriptions.

[0017] like Figure 2 As shown, this embodiment also includes two groups of arc-shaped excitation coil windings 2, one group is connected to the upper surface of the upper magnetic pole 1, and the other group is connected to the lower surface of the lower magnetic pole 1, and the two groups of arc-shaped excitation coil windings 2 are mirror-symmetrical relative to the central plane.

[0018] like Figure 3 As shown, from the large arc to the small arc on the sector surface of the sector pole 1, the arc radius of each group of arc excitation coils around the column 2 decreases successively, and the center 200 thereof changes position along the direction from the large arc to the small arc on the symmetry line 100 of the sector pole 1 in a top-down view.

[0019] like Figure 4 As shown, this embodiment also includes two groups of excitation coils 3 made of superconducting materials, one group is wound on an upper group of arc-shaped excitation coil winding poles 2, and the other group is wound on a lower group of arc-shaped excitation coil winding poles 2. In order to reduce the radial spacing between adjacent arc-shaped excitation coil winding poles 2, the coils in each group of excitation coils 3 can be staggered up and down, and the two groups of excitation coils 3 are mirror-symmetrical relative to the center plane.

[0020] like Figure 4 and Figure 5 As shown, in the upper and lower groups of excitation coils 3, the excitation coils at the upper and lower radially symmetrical positions are one group. After each group of coils is energized in series or in parallel, a magnetic field will be formed between the upper and lower magnetic poles 1. If the current intensity of each group of excitation coils 3 is reduced from a large radius to a small radius, the magnetic field intensity between the upper and lower magnetic poles 1 will gradually decrease from a large radius to a small radius, forming a magnetic field gradient and satisfying the isochronism condition.

[0021] Figure 5In the figure, the vertical axis represents the magnetic field intensity B, and the horizontal axis represents the bending radius R of the particle beam between the upper and lower magnetic poles. The lower curve in the figure represents the br curve A300 of each arc excitation coil winding column 2 and the excitation coil 3, and the upper curve represents the br curve B400 synthesized by the curve A300.

[0022] from Figure 5 It can be found that the more the number of arc-shaped excitation coil windings 2, the smaller the radial thickness and gap, the shorter the horizontal and oblique lines in the br curve B400, and the finer the adjustment of the magnetic field gradient. However, this brings two problems. First, the sum of the cross-sectional areas of a group of arc-shaped excitation coil windings 2 is smaller than the surface area of ​​the sector pole 1, which will reduce the magnetic flux; second, the number of turns of each excitation coil is reduced, thereby reducing the ampere-turns. The solution is to achieve superconductivity. On the one hand, the current density of the excitation coil 3 is increased, thereby increasing the ampere-turns; on the other hand, the arc-shaped excitation coil windings 2 in a low-temperature environment can increase the magnetic flux density and make up for the lack of magnetic flux area. This requires that the arc-shaped excitation coil windings 2 and the excitation coil 3 be placed in a low-temperature environment together, and this arrangement is made next.

[0023] like Figure 6 As shown, this embodiment also includes two magnetic conductive plates 4 similar to the sector-shaped surface of the magnetic pole 1, one connected to the upper end surface of an upper group of arc-shaped excitation coil winding columns 2, and the other connected to the lower end surface of a lower group of arc-shaped excitation coil winding columns 2.

[0024] The magnetic conductive plate 4 has two functions: one is to constitute a component in the low temperature environment component; the other is to diffuse the magnetic lines of force.

[0025] like Figure 7 As shown, this embodiment also includes two upper and lower opened liquid refrigerant storage pool frames 5, which are respectively connected to the upper and lower magnetic poles 1 and the vertical end faces of the magnetic conductive plate 4 to form two liquid refrigerant storage pools.

[0026] If the excitation coil is made of low-temperature superconducting material, the liquid refrigerant is liquid helium, and the liquid refrigerant storage pool is a liquid helium pool; if the excitation coil is made of high-temperature superconducting material, the liquid refrigerant is liquid nitrogen, and the liquid refrigerant storage pool is a liquid nitrogen pool.

[0027] After setting up the liquid cryostat storage pool, there is the insulation problem. Generally, vacuum insulation is used, which can be considered together with the vacuum system of the separation sector isochronous particle cyclotron.

[0028] like Figure 7 As shown, this embodiment also includes two liquid refrigerant pipelines 6, one of which is connected to the upper liquid refrigerant storage tank, and the other is connected to the upper and lower liquid refrigerant storage tanks. The liquid refrigerant pipeline 6 is used to inject liquid refrigerant and also to remove gaseous refrigerant generated by heat leakage.

[0029] like Figure 8 As shown, this embodiment also includes two thermal insulation pads 7 similar to the sector-shaped surface of the magnetic pole 1, one connected to the upper surface of the upper magnetic conductive plate 4, and the other connected to the lower surface of the lower magnetic conductive plate 4.

[0030] like Figure 8 As shown, this embodiment further includes a C-shaped magnetic yoke 8, the upper and lower inner surfaces of the two arms of which are respectively connected to the upper and lower outer surfaces of the two insulation pads 7 to form a superconducting sector magnet.

[0031] Towards the center plane is inside, and away from the center plane is outside.

[0032] Combined with the C-shaped magnetic yoke 8, the insulation pad 7 plays two roles: one is the insulation role, which prevents excessive loss of coldness in the upper and lower liquid refrigerant storage pools; the other is the connection role. For the upper insulation pad 7, it plays the role of suspending the liquid refrigerant storage pool, and for the lower insulation pad 7, it plays the role of supporting the liquid refrigerant storage pool. role.

[0033] The heat-insulating plate 7 does not affect the magnetic field lines between the upper and lower magnetic conductive plates 4 and the C-shaped magnetic yoke arms, and its effect is similar to the magnetic field lines between the upper and lower magnetic poles.

Claims

1. A sector magnet of a superconducting separation sector isochronous particle cyclotron accelerator comprises: A pair of upper and lower sector-shaped magnetic poles (1) having the same shape when viewed from above and mirror-symmetrical with respect to a horizontal central plane; Two groups of arc-shaped excitation coil windings (2), one group connected to the upper surface of the upper magnetic pole (1), and the other group connected to the lower surface of the lower magnetic pole (1), the two groups of arc-shaped excitation coil windings (2) are mirror-symmetrical with respect to the central plane, the arc radii of the two groups of arc-shaped excitation coil windings (2) decrease in sequence from the large arc to the small arc on the fan-shaped surface of the fan-shaped magnetic pole (1), and the center (200) thereof changes position along the direction from the large arc to the small arc on the symmetry line (100) of the fan-shaped magnetic pole (1) when viewed from a top view; Two groups of excitation coils (3) made of superconducting material, one group is wound on an upper group of arc-shaped excitation coil winding columns (2), and the other group is wound on a lower group of arc-shaped excitation coil winding columns (2), the coils in each group of excitation coils (3) can be staggered up and down, and the two groups of excitation coils (3) are mirror-symmetrical with respect to the central plane; Two magnetic conductive plates (4) having a similar sector-shaped surface to the magnetic pole (1), one connected to the upper end surface of an upper set of arc-shaped excitation coil winding columns (2), and the other connected to the lower end surface of a lower set of arc-shaped excitation coil winding columns (2); Two upper and lower open liquid refrigerant storage pool frames (5) are respectively connected to the upper and lower magnetic poles (1) and the vertical end faces of the magnetic conductive plate (4) to form two liquid refrigerant storage pools; Two liquid refrigerant pipelines (6), one of which is connected to the upper liquid refrigerant storage tank, and the other of which is connected to the upper and lower liquid refrigerant storage tanks; Two heat-insulating pads (7) having a similar fan-shaped surface to the magnetic pole (1), one connected to the upper surface of the upper magnetic conductive plate (4), and the other connected to the lower surface of the lower magnetic conductive plate (4); A C-shaped magnetic yoke (8) has upper and lower inner surfaces of two arms connected to upper and lower outer surfaces of two thermal insulation pads (7) respectively, forming a superconducting sector magnet.

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