A single coil winding type four-octupole composite iron system for beam homogenization

Abstract

The application discloses a single-coil winding type four-eight-pole composite iron system for beam homogenization, which comprises a composite magnet current control device, a composite magnet main power supply and a four-eight-pole composite iron. The four-eight-pole composite iron has eight pole heads, and only one type of excitation coil is wound on each pole head. The current value of the A-type excitation coil is the absolute value of the four-pole magnetic field excitation current value plus the eight-pole magnetic field excitation current value. The current value of the B-type excitation coil is the absolute value of the four-pole magnetic field excitation current value minus the eight-pole magnetic field excitation current value. The four-eight-pole composite iron is used for simultaneously generating a dominant four-pole magnetic field and an eight-pole magnetic field, so that the functions of the four-pole iron and the eight-pole iron can be realized simultaneously by installing only one transmission element. The application improves the excitation coil structure of the four-eight-pole composite iron composite magnet, only one set of excitation coils is wound on each pole head, so that the volume of the coil structure can be reduced, and the engineering cost can be lowered.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cyclotron, and particularly relates to a single-coil winding type four-octupole composite magnet system for beam homogenization. BACKGROUND

[0002] In order to utilize the charged particle beam generated in the accelerator, it is necessary to use a beam transport line composed of beam transport elements to transport the beam to the experimental terminal or designated position. Common beam transport elements include dipole magnets, quadrupole magnets, sextupole magnets and octupole magnets. The function of the beam transport element is to control the envelope shape of the beam during transmission to ensure that the envelope does not diverge during transmission, thereby avoiding particle collision with the transmission pipeline and causing beam loss. At the same time, the experimental terminal will have a series of requirements for the beam quality, such as beam uniformity, and only the beam that meets these conditions can meet the use requirements. Good beam quality is achieved by modulating the beam through the transmission element.

[0003] The functions of the beam transport elements used at the present stage are generally independent of each other. The quadrupole magnetic field for controlling the focusing or divergence of the beam is generated by a quadrupole magnet, and the octupole magnetic field for controlling the uniformity of the beam is generated by an octupole magnet.

[0004] The distribution of the accelerator extracted beam is generally approximately Gaussian distribution, which has the highest particle density at the center of the beam bunch, and also causes the local power on the neutron target to be too large and the temperature to be too high, resulting in damage to the neutron target. In order to solve the problem of uneven particle distribution, an octupole magnet is used on the beam transport line to homogenize the Gaussian distributed beam and reduce the peak power density on the neutron target.

[0005] One of the difficulties of using an octupole magnet to homogenize the Gaussian distributed beam is that the same octupole magnet installed at different positions on the beam transport line will have different effects. Only when the octupole magnet is installed at a position with a large beam envelope can it provide the strongest homogenization effect. However, the largest envelope in the existing technology is usually occupied by the quadrupole magnetic field, such as Figure 14aAs shown, the prior art transmission line is arranged in the order of the first quadrupole magnet, the first octupole magnet, the second quadrupole magnet and the second octupole magnet. Since the octupole magnet first focuses before homogenization, in order to ensure focusing, the positions of the first and second octupole magnets must be selected first at the waist position of the X-direction envelope and the waist position of the Y-direction envelope. However, since the first quadrupole magnet has a smaller envelope in the Y-direction at the waist position of the X-direction envelope, and the second quadrupole magnet has a smaller envelope in the X-direction at the waist position of the Y-direction envelope, at the first octupole magnet, although the waist position of the first octupole magnet in the X-direction is ensured, the envelope in the Y-direction is smaller. Similarly, at the second octupole magnet, although the waist position of the second octupole magnet in the Y-direction is ensured, the envelope in the X-direction is smaller. In summary, according to the conventional method, after the particles pass through the first and second quadrupole magnets, the beam envelope has been significantly reduced, so that the first and second octupole magnets cannot fully play their roles.

[0006] The second difficulty in using the octupole magnet to homogenize the Gaussian distribution of the beam is that the field strength K value of the octupole magnet is very large due to the small beam envelope at the positions of the first and second octupole magnets. The excessively high magnetic field strength is not only difficult to achieve in engineering, but also too high in cost and difficult to achieve.

[0007] The third difficulty in using the octupole magnet to homogenize the Gaussian distribution of the beam is that a type of transmission element on the beam transmission line only achieves one function, and each element has a fixed size. The number of transmission elements on the transmission line directly determines the length of the transmission line. For some specific occasions, due to the limited axial space for layout of the beam transmission line, too many transmission elements cannot be placed, so some sacrifices must be made in the axial direction, resulting in an undesirable beam quality. If the octupole magnet is used to achieve a better beam homogenization effect, the position of the octupole magnet and the phase thereof have strict requirements. In order to meet these requirements, the length of the transmission line often needs to be tens of meters. Since the diameter of the cyclotron is not more than 2 meters, dragging a beam line of tens of meters is equivalent to making the accelerator too small, which has no meaning. The longer the beam line, the more expensive the civil engineering of the surrounding shielding. In summary, the long transmission line has the disadvantages of large occupied area and high cost, which greatly limits the use of beam homogenization technology. SUMMARY

[0008] The present application is a single coil winding type four-octupole composite magnet system for beam homogenization, which aims to solve the problem that the maximum envelope is usually occupied by the quadrupole magnetic field in the prior art, and the octupole magnet cannot provide the strongest homogenization effect; the second purpose is to solve the problem that the envelope at the position of the octupole magnet on the transmission line is small, so that the field strength K value of the octupole magnet is very large, and the excessively high magnetic field strength is difficult to implement in engineering, and the cost is too high; the third purpose is to solve the problem that if the octupole magnet is used to achieve better beam homogenization effect, the length of the transmission line often needs to be tens of meters, and the long transmission line occupies a large area and has high cost, which greatly limits the use of beam homogenization technology.

[0009] The present application is a single coil winding type four-octupole composite magnet system for beam homogenization, which aims to solve the problem that the maximum envelope is usually occupied by the quadrupole magnetic field in the prior art, and the octupole magnet cannot provide the strongest homogenization effect; the second purpose is to solve the problem that the envelope at the position of the octupole magnet on the transmission line is small, so that the field strength K value of the octupole magnet is very large, and the excessively high magnetic field strength is difficult to implement in engineering, and the cost is too high; the third purpose is to solve the problem that if the octupole magnet is used to achieve better beam homogenization effect, the length of the transmission line often needs to be tens of meters, and the long transmission line occupies a large area and has high cost, which greatly limits the use of beam homogenization technology.

[0010] A single coil winding type four-octupole composite magnet system for beam homogenization, characterized in that: the four-octupole composite magnet system comprises a four-octupole composite magnet current control device, a four-octupole composite magnet main power supply, and a four-octupole composite magnet; the four-octupole composite magnet has eight pole heads, and only one type of excitation coil is wound on each pole head; the excitation coils of the four-octupole composite magnet are designed as A-type excitation coils and B-type excitation coils; the four-octupole composite magnet current control device is used to control the A-type excitation coil current output and the B-type excitation coil current output of the four-octupole composite magnet main power supply to the four-octupole composite magnet; the four-octupole composite magnet is used to generate a dominant quadrupole magnetic field and an octupole magnetic field at the same time, so that the functions of the quadrupole magnet and the octupole magnet can be realized at the same time by installing only one transmission element;

[0011] The current value of the A-type excitation coil is the absolute value of the quadrupole magnetic field excitation current value plus the octupole magnetic field excitation current value; and the current value of the B-type excitation coil is the absolute value of the quadrupole magnetic field excitation current value minus the octupole magnetic field excitation current value.

[0012] Further, the coil arrangement of each pole head is as follows: A-type excitation coils are installed on pole heads 1, 4, 5, and 8, and B-type excitation coils are installed on pole heads 2, 3, 6, and 7, wherein the current values of the excitation coils of the same type are equal; wherein the current directions of the A-type excitation coils on pole heads 1 and 5 are the same and opposite to the current directions on pole heads 4 and 8, and the current directions of the B-type excitation coils on pole heads 2 and 6 are the same and opposite to the current directions on pole heads 3 and 7.

[0013] Further, the four / eight-pole composite magnet current control device comprises: a coil current two-dimensional sampling point establishing module, an experimental measurement preliminary magnetic field gradient three-dimensional curved surface sample library establishing module, an interpolation fine magnetic field gradient three-dimensional curved surface sample library using module, an input field gradient corresponding field gradient current curve solving module, a four / eight-pole field gradient current curve intersection point solving module, and an A / B type excitation coil current size output module.

[0014] The coil current two-dimensional sampling point establishing module is used to establish a four-pole magnet and an eight-pole magnet coil current two-dimensional data comparison table.

[0015] The experimental measurement preliminary magnetic field gradient three-dimensional curved surface sample library establishing module is used to perform magnetic field experimental measurement on the four / eight-pole composite magnet by using the current value of the coil current two-dimensional data comparison table, so that the four / eight-pole magnetic field gradient measurement value corresponding to the two-dimensional current data comparison table is obtained, and a three-dimensional curved surface sample database of the magnetic field gradient is obtained. The three-dimensional curved surface sample database of the magnetic field gradient comprises a four-pole field gradient three-dimensional curved surface sample database and an eight-pole field gradient three-dimensional curved surface sample database.

[0016] The interpolation fine magnetic field gradient three-dimensional curved surface sample library using module is used to perform two-dimensional interpolation on the four-pole field gradient three-dimensional curved surface sample database and the eight-pole field gradient three-dimensional curved surface sample database by using a cubic spline function, and to encrypt the grid point density.

[0017] The input field gradient corresponding field gradient current curve solving module is used to intersect the input four-pole field gradient and eight-pole field gradient with the magnetic field gradient curved surface of the three-dimensional curved surface sample database, and to obtain two corresponding current curves after the intersection. Specifically, a four-pole field gradient plane is selected, the plane intersects the magnetic field gradient curved surface of the four-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the four-pole field gradient is obtained. An eight-pole field gradient plane is selected, the plane intersects the magnetic field gradient curved surface of the eight-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the eight-pole field gradient is obtained.

[0018] The four / eight-pole field gradient current curve intersection point solving module is used to obtain the intersection point of the current curve satisfying the four-pole field gradient and the current curve satisfying the eight-pole field gradient, and to use the intersection point as the excitation current solution of the four / eight-pole composite magnet.

[0019] The A / B type excitation coil current output module adds the four-pole field coil current and the eight-pole field coil current value to obtain an absolute value as the current value of the A type coil, subtracts the four-pole field coil current and the eight-pole field coil current value to obtain an absolute value as the current value of the B type coil, and outputs the A type coil current and the B type coil current to the four / eight-pole composite magnet.

[0020] Advantages and effects of the present application

[0021] 1. The single-coil winding type four-octupole composite magnet system for beam current homogenization is provided in the present application, which improves the structure of the excitation coil of the four-octupole composite magnet on the basis of the four-pole magnetic field excitation coil and the eight-pole magnetic field excitation coil of the four-octupole composite magnet, and only one set of excitation coil is wound on each pole head, so that the volume of the coil structure can be reduced and the engineering cost can be reduced. Meanwhile, the single-coil structure of the pole head does not have the situation that the actions of the two sets of coil currents in the double-coil structure cancel each other out, so that the coil power loss of the four-octupole composite magnet system can be reduced.

[0022] 2. The four-pole magnetic field and the eight-pole magnetic field are generated in the aperture of the four-octupole composite magnet, which can simultaneously realize the focusing and homogenization of the beam envelope, and solve the problem that the envelope maximum is usually occupied by the four-pole magnetic field and the eight-pole magnet cannot provide the strongest homogenization effect in the prior art.

[0023] 3. The four-pole magnetic field and the eight-pole magnetic field are generated in the aperture of the four-octupole composite magnet, which can simultaneously realize the focusing and homogenization of the beam envelope, provide the strongest homogenization effect, and solve the problem that the field strength K value of the eight-pole magnet is very large due to the small envelope at the position of the eight-pole magnet on the transmission line in the prior art, and the excessively high magnetic field strength is difficult to implement in engineering, and the cost is too high.

[0024] 4. The four-pole magnetic field and the eight-pole magnetic field are generated in the aperture of the four-octupole composite magnet, which can simultaneously realize the focusing and homogenization of the beam envelope, and when it is installed on the beam transmission line, the number of transmission elements can be reduced, the length of the transmission line can be shortened, and the engineering cost of the beam transport line can be reduced. For the transmission line, the four-octupole composite magnet can simultaneously exert the maximum effect of the magnet, because it is installed at the position of the maximum beam envelope, at which time the focusing effect and the homogenization effect are the strongest, and the problem that the traditional four-pole magnet and the eight-pole magnet cannot be simultaneously installed at the position of the maximum beam envelope due to the space problem and cannot exert the maximum effect of the magnet is solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the four-octupole composite magnet system for beam current homogenization in the present application;

[0026] Figure 2 It is an application effect diagram of the beam transmission element: (left) four-pole magnet; (right) eight-pole magnet;

[0027] Figure 3 Four-pole magnetic field distribution and focusing principle;

[0028] Figure 4 Eight-pole magnetic field and beam homogenization process;

[0029] Figure 5a The four eight-pole composite magnet structure is based on double coil winding.

[0030] Figure 5b The four eight-pole composite magnet model based on double coil winding is partially enlarged. Figure 5a The four eight-pole composite magnet model based on double coil winding is partially enlarged.

[0031] Figure 6 The four eight-pole composite magnet coil arrangement and current direction based on double coil winding.

[0032] Figure 7a The four eight-pole composite magnet structure based on single coil winding.

[0033] Figure 7b The four eight-pole composite magnet coil winding based on single coil winding.

[0034] Figure 8 The current value diagram of two groups of coils during magnetic field measurement.

[0035] Figure 9 The four / eight-pole magnetic field gradient diagram corresponding to different currents in the experimental measurement.

[0036] Figure 10 The three-dimensional interpolation grid point density diagram using cubic spline function.

[0037] Figure 11 The intersection diagram of the selected magnetic field gradient plane and the magnetic field gradient surface of the three-dimensional sample database.

[0038] Figure 12 The current curve diagram corresponding to the four / eight-pole magnetic field.

[0039] Figure 13 The four eight-pole composite magnet excitation current solving diagram.

[0040] Figure 14a The four eight-pole composite magnet is applied to the super-short beam uniformization transmission line.

[0041] Figure 14b The existing eight-pole magnet is in a small envelope position diagram. DETAILED DESCRIPTION

[0042] Design principle of the application

[0043] 1. Problems existing in the transmission line based on four-pole magnet and eight-pole magnet discrete element arrangement

[0044] 1) Conventional methods of combining two quadrupole magnets cannot meet the requirements of limited axial space in the transmission line. The magnetic field lines of a quadrupole magnet generating a quadrupole field are distributed as follows: Figure 3 As shown, when the beam passes through the central aperture of a quadrupole magnet, it experiences an inward lateral focusing force in the X direction, causing the beam envelope to contract and focus in that direction. Conversely, it experiences an outward lateral focusing force in the Z direction, causing the beam envelope to diverge and defocus in that direction. Therefore, a single quadrupole magnet focuses the beam in one direction and defocuses it in the other. To ensure the beam experiences an inward lateral focusing force in both the Y and X directions, two quadrupole magnets are typically used. When using two quadrupole magnets, the excitation currents in their coils are in opposite directions; one magnet focuses in the X direction, and the other defocuses it. Combining two quadrupole magnets in this case, according to the alternating focusing principle, ensures the beam is focused in both the X and Z directions, thus preventing divergence during transmission. The same quadrupole magnet will have different effects depending on the position it is installed on the beam transmission line. When it is installed at the position with the largest beam envelope, it can provide the strongest focusing effect. Generally, the quadrupole magnet is installed at the position with the largest beam envelope.

[0045] 2) When octagonal and quadrature magnets are deployed independently, the octagonal magnet cannot fully exert its function. For example... Figure 4 As shown, the first principle of how an octagonal magnet achieves uniform particle distribution is as follows: An octagonal magnet generates an octagonal magnetic field, which ensures a uniform distribution of particles in the beam within space. Before passing through the octagonal magnet, the particles exhibit a Gaussian distribution, primarily concentrated in the central region of the envelope. After passing through the octagonal magnet, they become uniformly distributed within the envelope. The octagonal magnet has eight poles, with the N and S poles alternating. The effect of the octagonal magnet on the beam is as follows... Figure 4 As shown, adjacent magnetic poles have opposite effects on the beam: one compresses inward, and the other stretches outward, gradually transforming the beam envelope from a circle to a square, and finally to a four-pointed star envelope. Because the proportions of the four inward-facing beams and the four outward-facing beams are similar, the four-pointed star envelope shape results in a more uniform particle distribution. Therefore, by adjusting the strength of the octagonal magnetic field, a square beam spot can be initially obtained, and over time, the square envelope shape gradually changes to the final four-pointed star envelope shape. Secondly, when octagonal and quadrupole magnets are deployed independently, the octagonal magnet cannot fully exert its function. The same octagonal magnet installed at different positions on the beam transmission line will have different effects. When installed at the position with the largest beam envelope, it provides the strongest homogenization effect. However, quadrupole magnets are generally installed where the envelope is largest, so octagonal magnets can only be installed where the envelope is not very large, and their function cannot be fully utilized.

[0046] 2. Innovation points of this invention:

[0047] One of the innovations lies in the invention of a four-octet composite magnet. For example... Figure 7a , 7b As shown, a four-octet composite magnet wound with a single coil is used instead of the one shown above. Figure 14b The existing technology of discrete element quadrupole magnets and octupole magnets, and the replacement of such Figure 5a and Figure 6 A four-eighth pole composite magnet with two coils wound together. After being combined, the four-eighth pole composite magnet generates a four-pole magnetic field and an octagonal magnetic field within its aperture, such as... Figure 14a As shown, for transmission lines, the four-eight-pole composite magnet can simultaneously exert its maximum magnetic effect because it is installed at the maximum position of the beam envelope. At this position, the focusing and homogenization effects are strongest, solving the problem that traditional four-pole and eight-pole magnets cannot be simultaneously installed at the maximum beam envelope due to space constraints, thus limiting their effectiveness. The four-pole magnets of the first four-eight-pole composite magnet share the large envelope position in the Y direction with the four-pole magnet in front of it, and the four-pole magnets of the second four-eight-pole composite magnet share the large envelope position in the X direction with the four-pole magnets of the first four-eight-pole composite magnet in front of it. Because the eight-pole magnets in both the first and second four-eight-pole composite magnets are positioned within the large envelope, a better beam homogenization effect can be achieved; that is, it can simultaneously achieve the effects of focusing and homogenizing the beam envelope. Compared to... Figure 14b The existing technology, due to the separate arrangement of quadrupole and octupole magnets, suffers from poor homogenization because the octupole magnet cannot change its envelope like the quadrupole magnet, meaning it cannot coexist with the quadrupole magnet to form a large envelope. Therefore, the envelopes in both the Y and X directions of the separately arranged octupole magnets are relatively small. Secondly, installing quadrupole-octupole composite magnets on the beam transmission line reduces the number of transmission elements, shortens the transmission line length, and reduces the engineering cost of the beam transmission line. This reduction in the number of transmission elements not only saves on quadrupole magnets but also eliminates the need for additional components on the transmission line to achieve the same homogenization effect.

[0048] The second innovation lies in: Figure 9 As shown, a three-dimensional surface sample database of magnetic field gradient was established. This database uses a two-dimensional data comparison table of coil currents of quadrupole and octupole magnets as the projection coordinates of the three-dimensional surface and the magnetic field gradient as the height of the three-dimensional surface, thereby establishing the relationship between the coil currents of quadrupole and octupole magnets and the magnetic field gradient.

[0049] The third innovation lies in: Figure 11As shown, the relationship between the magnetic field gradient plane and the magnetic field gradient three-dimensional surface intersection is established, so that the current curve at the intersection is obtained, the magnetic field gradient of any point on the curve is equal, but the quadrupole magnetic field current and octupole magnetic field current values on any point on the curve are not equal or equal, which lays the foundation for the solution of the intersection of the two curves as the excitation current of the four-octupole composite magnet.

[0050] The fourth innovation lies in that, as shown in Figure 12 , 13 , the current curve on different magnetic field gradients is projected into the same coordinate plane using the independence of the current curve and the magnetic field gradient, and the intersection point is obtained, which is used as the solution of the excitation current of the four-octupole composite magnet.

[0051] The fifth innovation lies in that, as shown in Figure 7b , Figure 6 , the single-coil winding type four-octupole composite magnet is used to replace the double-coil winding type four-octupole composite magnet. The single-coil winding has the characteristics of improving the excitation coil structure of the composite magnet, winding only one set of excitation coils on each pole head, so as to reduce the volume of the coil structure and reduce the engineering cost. At the same time, the single-coil structure of the pole head does not have the situation that the actions of the two sets of coil currents in the double-coil structure cancel each other out, so as to reduce the coil power loss of the composite magnet system.

[0052] 3. Design principle of double-coil winding type four-octupole composite magnet system

[0053] ① Design principle of double-coil winding type four-octupole composite magnet, as shown in Figure 5a , Figure 6 , that is, each pole head of the magnet is wound with two sets of coils, the inner layer is the octupole magnetic field excitation coil, and the outer layer is the quadrupole field coil. The current directions of the 1, 3, 5, and 7 pole heads of the outer layer octupole field coil are opposite, that is, the octupole field coil is divided into 1, 3, 5, and 7 pole heads and 2, 4, 6, and 8 pole heads, the excitation currents of the two are equal in size but opposite in direction, thereby generating an octupole magnetic field. The adjacent two pole heads of the outer layer quadrupole magnetic field excitation coil are a group, which are divided into four groups, that is, 1, 2 pole heads, 3, 4 pole heads, 5, 6 pole heads, and 7, 8 pole heads; among them, 1, 2 pole heads and symmetrically arranged 5, 6 pole heads, the excitation currents of the two sets of quadrupole magnetic field coils are consistent in size and direction, 3, 4 pole heads and symmetrically arranged 7, 8 pole heads, the excitation currents of the two sets of coils are consistent in size and direction, the current directions of 1, 2 pole heads and 3, 4 pole heads are opposite, and the current directions of 5, 6 pole heads and 7, 8 pole heads are opposite, thereby generating a quadrupole magnetic field.

[0054] The current directions of each pole head of the double-coil winding type four-eight-pole composite magnet are summarized as follows: the current directions of the inner and outer coils of pole head 1 are opposite, the inner coil is left-in and right-out, and the outer coil is right-in and left-out; the current directions of the inner and outer coils of pole head 2 are the same, the inner coil is right-in and left-out, and the outer coil is also right-in and left-out; the current directions of the inner and outer coils of pole head 3 are the same, the current directions of the inner and outer coils of pole head 4 are opposite, the current directions of the inner and outer coils of pole head 5 are opposite, the current directions of the inner and outer coils of pole head 6 are the same, the current directions of the inner and outer coils of pole head 7 are the same, and the current directions of the inner and outer coils of pole head 8 are opposite. In summary, the current directions of the four-pole magnetic field and the eight-pole magnetic field on pole heads 2, 3, 6 and 7 are the same, and the current directions of the four-pole magnetic field and the eight-pole magnetic field on pole heads 1, 3, 5 and 8 are opposite.

[0055] The double-coil winding type four-eight-pole composite magnet has the following problems: first, the double-coil structure of winding a set of four-pole magnet coils and eight-pole magnet coils on each pole head of the magnet increases the overall volume of the coil structure, which requires sufficient space between the pole heads of the composite magnet to install the coil structure, resulting in limitations on the volume optimization of the composite magnet, and the double-coil structure also increases the engineering cost; second, the current directions of the four-pole magnet coils and the eight-pole magnet coils on some pole heads are opposite, so the actions of the currents of the two sets of coils on these pole heads will cancel out a part, thus causing unnecessary coil power loss.

[0056] 4. Single-coil winding type four-eight-pole composite magnet system design principle: 1) The single-coil winding type is to group the pole heads whose current directions of the four-pole magnetic field and the eight-pole magnetic field are the same (for example, pole heads 2, 3, 6 and 7 of the double-coil winding type four-eight-pole composite magnet) as a set, and to group the pole heads whose current directions of the four-pole magnetic field and the eight-pole magnetic field are opposite (for example, pole heads 1, 3, 5 and 8 of the double-coil winding type four-eight-pole composite magnet) as a set. Figure 6 Figure 6 ​The current directions of the 1, 4, 5, 8 pole heads are set to be the same, and the 1, 4, 5, 8 pole heads are set as A type excitation coils, the current value of the A type excitation coils is: the absolute value of the four-pole magnetic field excitation current value plus the eight-pole magnetic field excitation current value; the current directions of the 2, 3, 6, 7 pole heads are set to be opposite, and the 2, 3, 6, 7 pole heads are set as B type excitation coils, the current value of the B type excitation coils is: the four-pole magnetic field excitation current value minus the absolute value of the eight-pole magnetic field excitation current value. The same point of the single coil and the double coil winding is that: the four-pole field current and the eight-pole field current of the coil are superimposed, the difference is that: the single coil winding type only winds one group of excitation coils on each pole head, and the current value of the one group of excitation coils superimposes the four-pole field current and the eight-pole field current, and the double coil winding type winds two groups of coils on each pole head, which respectively represent the four-pole field current and the eight-pole field current. 2) Based on the design principle of the single coil winding type four-eight pole composite magnet system, the single coil winding type four-eight pole composite magnet system for beam homogenization is proposed in the application, the system is characterized in that the excitation coil structure of the double coil winding four-eight pole composite magnet is improved, only one group of excitation coils is wound on each pole head, so that the volume of the coil structure can be reduced, and the engineering cost can be reduced. At the same time, the single coil structure of the pole head does not exist the situation that the actions of the currents of the two groups of coils are counteracted, so that the coil power loss of the four-eight pole composite magnet system can be reduced.

[0057] Based on the above application principle, the application designs a single coil winding type four-eight pole composite magnet system for beam homogenization, as shown in the accompanying drawings: Figure 1 The four-eight pole composite magnet system includes a four-eight pole composite magnet current control device, a four-eight pole composite magnet main power supply and a four-eight pole composite magnet. The four-eight pole composite magnet has eight pole heads, and only one type of excitation coil is wound on each pole head. The excitation coil of the four-eight pole composite magnet is designed as an A type excitation coil and a B type excitation coil. The four-eight pole composite magnet current control device is used to control the A type excitation coil current output and the B type excitation coil current output of the four-eight pole composite magnet main power supply to the four-eight pole composite magnet. The four-eight pole composite magnet is used to generate a dominant four-pole magnetic field and an eight-pole magnetic field at the same time, so that only one transmission element can realize the functions of the four-pole magnet and the eight-pole magnet at the same time.

[0058] As shown in the accompanying drawings: Figure 7b The current value of the A type excitation coil is: the absolute value of the four-pole magnetic field excitation current value plus the eight-pole magnetic field excitation current value; and the current value of the B type excitation coil is: the four-pole magnetic field excitation current value minus the absolute value of the eight-pole magnetic field excitation current value.

[0059] As shown in the accompanying drawings: Figure 7bAs shown in the figure, the coil arrangement of each pole head is as follows: A type excitation coil is installed on pole head 1, 4, 5, 8, B type excitation coil is installed on pole head 2, 3, 6, 7, and the current value of the same type excitation coil is equal; the current direction of A type excitation coil on pole head 1, 5 is the same and opposite to that on pole head 4, 8, and the current direction of B type excitation coil on pole head 2, 6 is the same and opposite to that on pole head 3, 7.

[0060] As shown in the figure, Figure 1 The four / eight-pole composite magnet current control device comprises: a coil current two-dimensional sampling point establishing module, an experimental measurement preliminary magnetic field gradient three-dimensional curved surface sample database establishing module, an interpolated magnetic field gradient three-dimensional curved surface sample database using module, an input field gradient corresponding field gradient current curve solving module, a four / eight-pole field gradient current curve intersection point solving module, and a four / eight-pole coil current size output module.

[0061] As shown in the figure, Figure 8 The coil current two-dimensional data reference table of the four-pole magnet and the eight-pole magnet is established by the coil current two-dimensional sampling point establishing module.

[0062] As shown in the figure, Figure 9 The coil current two-dimensional data reference table is used to measure the magnetic field of the four / eight-pole composite magnet, so that the four / eight-pole magnetic field gradient measurement value corresponding to the two-dimensional current data reference table is obtained, and the three-dimensional curved surface sample database of the magnetic field gradient is obtained; the three-dimensional curved surface sample database of the magnetic field gradient comprises a four-pole field gradient three-dimensional curved surface sample database and an eight-pole field gradient three-dimensional curved surface sample database.

[0063] As shown in the figure, Figure 10 The interpolated magnetic field gradient three-dimensional curved surface sample database using module is used to perform two-dimensional interpolation on the four-pole field gradient three-dimensional curved surface sample database and the eight-pole field gradient three-dimensional curved surface sample database by using a cubic spline function, and the grid point density is encrypted.

[0064] As shown in the figure, Figure 11 , 12 The input field gradient corresponding field gradient current curve solving module is used to intersect the input four-pole field gradient and eight-pole field gradient with the magnetic field gradient surface of the three-dimensional curved surface sample database, and obtain two corresponding current curves after intersection; specifically: a four-pole field gradient plane is selected, the plane intersects the magnetic field gradient surface of the four-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the four-pole field gradient is obtained; an eight-pole field gradient plane is selected, the plane intersects the magnetic field gradient surface of the eight-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the eight-pole field gradient is obtained.

[0065] As​Figure 13 The module for solving the intersection point of the four-pole field gradient current curve and the eight-pole field gradient current curve is used to obtain the intersection point of the current curve satisfying the four-pole field gradient and the current curve satisfying the eight-pole field gradient, and use the intersection point as the solution of the excitation current of the four-eight-pole compound magnet;

[0066] The module for outputting A / B type excitation coil current adds the absolute value of the four-pole field coil current and the eight-pole field coil current value to obtain the current value of the A type coil, subtracts the absolute value of the four-pole field coil current and the eight-pole field coil current value to obtain the current value of the B type coil, and outputs the A type coil current and the B type coil current to the four-eight-pole compound magnet.

[0067] It should be emphasized that the above-mentioned specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the above-mentioned embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A single coil winding type four octupole composite magnet system for beam homogenization, characterized by: The four-eight-pole composite magnet system comprises a four-eight-pole composite magnet current control device, a four-eight-pole composite magnet main power supply and a four-eight-pole composite magnet; the four-eight-pole composite magnet has eight pole heads, and each pole head is wound with only one type of field coil; the field coils of the four-eight-pole composite magnet are designed as A-type field coils and B-type field coils; The four-eight-pole composite magnet current control device is used for controlling the A-type field coil current output and the B-type field coil current output of the four-eight-pole composite magnet main power supply to the four-eight-pole composite magnet; the four-eight-pole composite magnet is used for simultaneously generating a dominant four-pole magnetic field and an eight-pole magnetic field, so that the functions of the four-pole magnet and the eight-pole magnet can be simultaneously realized by installing only one transmission element; The current value of the A-type field coil is the absolute value of the four-pole field excitation current value plus the eight-pole field excitation current value; and the current value of the B-type field coil is the absolute value of the four-pole field excitation current value minus the eight-pole field excitation current value; The four-eight-pole composite magnet current control device comprises a two-dimensional sampling point module of coil current, an experimental measurement preliminary three-dimensional curved surface sample database module of magnetic field gradient, an interpolation refinement three-dimensional curved surface sample database module of magnetic field gradient, an input field gradient solving corresponding field gradient current curve module, a four / eight-pole field gradient current curve intersection point solving module and an A / B-type field coil current size output module; The two-dimensional sampling point module of coil current is used for establishing a two-dimensional data reference table of coil current of the four-pole magnet and the eight-pole magnet; The experimental measurement preliminary three-dimensional curved surface sample database module of magnetic field gradient is used for performing magnetic field experimental measurement on the four-eight-pole composite magnet by using the current value of the two-dimensional data reference table of coil current, so that four / eight-pole magnetic field gradient measurement values corresponding to the two-dimensional data reference table of coil current are obtained, and a three-dimensional curved surface sample database of magnetic field gradient is obtained; the three-dimensional curved surface sample database of magnetic field gradient comprises a four-pole field gradient three-dimensional curved surface sample database and an eight-pole field gradient three-dimensional curved surface sample database; The interpolation refinement three-dimensional curved surface sample database module of magnetic field gradient is used for performing two-dimensional interpolation on the four-pole field gradient three-dimensional curved surface sample database and the eight-pole field gradient three-dimensional curved surface sample database by using a cubic spline function, and encrypting the grid point density; The input field gradient solving corresponding field gradient current curve module is used for intersecting the input four-pole field gradient and eight-pole field gradient with the magnetic field gradient curved surface of the three-dimensional curved surface sample database, and obtaining two corresponding current curves after the intersection; specifically, a four-pole field gradient plane is selected, the plane intersects the magnetic field gradient curved surface of the four-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the four-pole field gradient is obtained; an eight-pole field gradient plane is selected, the plane intersects the magnetic field gradient curved surface of the eight-pole field gradient three-dimensional curved surface sample database, and a current curve satisfying the eight-pole field gradient is obtained; The four / eight-pole field gradient current curve intersection point solving module is used for obtaining the intersection point of the current curve satisfying the four-pole field gradient and the current curve satisfying the eight-pole field gradient, and using the intersection point as the excitation current solution of the four-eight-pole composite magnet. The output A / B type excitation coil current module adds the absolute value of the four-pole field coil current and the eight-pole field coil current value to obtain the current value of the A type coil, subtracts the four-pole field coil current from the eight-pole field coil current value to obtain the absolute value of the B type coil current, and outputs the A type coil current and the B type coil current to the four-eight-pole composite magnet.

2. The single coil winding type four octupole composite magnet system for beam homogenization according to claim 1, characterized in that: The coil arrangement of each pole head is as follows: the A type excitation coil is installed on the pole heads 1, 4, 5, and 8, and the B type excitation coil is installed on the pole heads 2, 3, 6, and 7, wherein the current values of the same type excitation coils are equal; wherein the current directions of the A type excitation coils on the pole heads 1 and 5 are the same and opposite to the current directions on the pole heads 4 and 8, and the current directions of the B type excitation coils on the pole heads 2 and 6 are the same and opposite to the current directions on the pole heads 3 and 7.

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