Ultra-short symmetrically bent beam homogenizer

Abstract

The application discloses a super-short symmetrical bending type beam homogenization transmission line, which is a symmetrical bending type strong current homogenization beam line containing two pieces of four-eight level composite iron and one piece of shared two level iron; the symmetrical bending type strong current homogenization beam line is composed of one shared beam line and two branch beam lines; the shared beam line is provided with an accelerator exit, a beam matching mechanism, four-eight level composite iron 1 and two level iron along the beam direction; the first branch beam line is sequentially provided with four-eight level composite iron 2, a beam matching and homogenization effect observation mechanism 1 and a terminal 1; the second branch beam line is sequentially provided with four-eight level composite iron 3, a beam matching and homogenization effect observation mechanism 2 and a terminal 2; the four-eight level composite iron of the beam line can simultaneously realize the focusing and homogenization of the beam envelope, the composite iron installed on the beam transmission line can reduce the number of transmission elements, shorten the length of the transmission line and reduce the engineering cost of the beam transmission line.

Description

Technical Field

[0001] This invention belongs to the field of accelerator transmission line technology, and particularly relates to an ultra-short symmetrical bending beam homogenization transmission line. Background Technology

[0002] The secondary particles produced when the beam from an accelerator strikes a target are important radiation sources for many nuclear technology research and applications. For example, in nuclear technology applications such as neutron imaging and boron neutron capture therapy based on high-current proton accelerators, the accelerator generates a high-energy, high-current proton beam, which, after passing through a transmission line, strikes a neutron target, producing high-flux neutrons.

[0003] The distribution of the accelerator beam is generally similar to a Gaussian distribution, with the highest particle density at the center of the beam cluster. This also causes excessive local power and temperature on the neutron target, leading to damage to the neutron target.

[0004] To address the issue of uneven particle distribution, an octagonal magnet was attempted on the beam transmission line to homogenize the Gaussian-distributed beam and reduce the peak power density on the neutron target.

[0005] One of the challenges in using octagonal magnets to homogenize a Gaussian-distributed beam is that the same octagonal magnet will have different effects depending on the position it is installed on the beam transmission line. Only when the octagonal magnet is installed at a position with a larger beam envelope can it provide the strongest homogenization effect. However, the largest envelope area in existing technologies is usually occupied by quadrupole magnetic fields: the transmission lines in existing technologies are arranged in the order of quadrupole 1, octupole 1, quadrupole 2, and octupole 2. Since the octupoles must be focused before homogenization (the purpose of focusing is to allow the beam to pass through the circular hole in the center of the octupole without hitting the octupole), in order to ensure focusing, the positions of octupole 1 and octupole 2 must first be selected at the waist position of the X-direction envelope and the waist position of the Y-direction envelope. However, since the Y-direction envelope of quadrupole 1 at the waist position of the X-direction envelope is small, and the X-direction envelope of quadrupole 2 at the waist position of the Y-direction envelope is small, at octupole 1, although the position of octupole 1 at the waist position of the X-direction is guaranteed, the Y-direction envelope at that position is small. Similarly, at octupole 2, although the position of octupole 2 at the waist position of the Y-direction is guaranteed, the X-direction envelope at that position is small. In summary, according to the traditional method, the beam envelope is significantly reduced after the particles pass through quadrupole 1 and quadrupole 2, so the full effect of octupole 1 and octupole 2 cannot be achieved.

[0006] The second difficulty in homogenizing a Gaussian-distributed beam using an octagonal magnet lies in the fact that the beam envelope at the locations of octagonal magnet 1 and octagonal magnet 2 is small, resulting in a very large field strength K value for the octagonal magnet. Excessively high magnetic field strength is not only difficult to achieve in engineering, but also too costly and difficult to implement.

[0007] The third challenge in homogenizing a Gaussian-distributed beam using octagonal magnets lies in the fact that achieving good beam homogenization requires strict control over the placement and phase of the octagonal magnets. To meet these requirements, transmission lines often need to be over ten meters long. Cyclotrons have a diameter of no more than two meters; dragging a beamline over ten meters long would render miniaturizing the accelerator pointless. Furthermore, the longer the beamline, the more expensive the surrounding shielding infrastructure becomes. In short, the large footprint and high cost of excessively long transmission lines significantly limit the application of beam homogenization technology. Summary of the Invention

[0008] This invention addresses the problems of existing technologies by proposing an ultra-short symmetrical bending beam homogenization transmission line. The first objective is to solve the problem that existing technologies using discrete quadrupole and octupole magnets often fail to fully utilize the octupole magnet's function because the area with the largest envelope is usually occupied by the quadrupole magnetic field. The second objective is to solve the problem that using discrete quadrupole and octupole magnets results in a smaller beam envelope at the locations of octupole magnet 1 and octupole magnet 2, requiring extremely high field strength from the octupole magnet, which is prohibitively expensive and difficult to achieve in engineering. The third objective is to solve the problem that using discrete quadrupole and octupole magnets leads to excessively long transmission lines, resulting in increasingly expensive surrounding shielding structures, larger footprints, and higher costs.

[0009] To solve its technical problem, the present invention adopts the following technical solution:

[0010] An ultra-short symmetrical bend beam homogenization transmission line is characterized in that: the transmission line is a symmetrical bend beam homogenization transmission line that includes two quadrature octet composite irons and one common diode iron; the symmetrical bend beam homogenization transmission line that includes two quadrature octet composite irons and one common diode iron consists of one common transmission line and two branch transmission lines.

[0011] The four-pole and eight-pole composite iron 1, four-pole and eight-pole composite iron 2, and four-pole and eight-pole composite iron 3 of the first and second bend-transformer beam homogenization transmission lines generate four-pole magnetic fields and eight-pole magnetic fields simultaneously, so that the functions of four-pole and eight-pole iron can be realized simultaneously by installing only one transmission element.

[0012] The first curved beam homogenization transmission line reaches a maximum value in the Y or X direction at the octapole composite iron 1, and a maximum value in the X or Y direction at the octapole composite iron 2; the phase shift of the particle between the octapole composite iron 1 and octapole composite iron 2 and the target. They are respectively close to integer multiples of 180 degrees; the transmission matrix between the two octagonal magnetic fields is close to an identity matrix;

[0013] The diodes on this ultrashort symmetrical bend beam homogenization transmission line are shared diodes on the ultrashort symmetrical bend beam homogenization transmission line. These shared diodes have symmetrical upper and lower edge angles at their exit edges. Specifically, their beam inlet edge is a straight line, and their beam outlet edge is a pair of symmetrical upper and lower oblique lines. The inclination direction of these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting these symmetrical oblique lines and the center of the beam bending trajectory to the beam at the diode outlet forms the diode outlet edge angle. By changing the size of the diode outlet edge angle, the edge field focusing effect of the diode is adjusted, and in conjunction with the envelopes of the four-octet composite irons on both sides of the diode in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

[0014] The second curved beam homogenization transmission line reaches a maximum value at the octapsodium composite iron 1 in the Y or X direction, and at the octapsodium composite iron 3 in the X or Y direction, indicating a phase shift between the particle and the target at octapsodium composite iron 1 and octapsodium composite iron 3. They are all close to integer multiples of 180 degrees; the transmission matrix between the two octagonal magnetic fields is close to an identity matrix;

[0015] The first and second curved beam homogenization transmission lines, comprising four-eight-pole composite iron 1, four-eight-pole composite iron 2, and four-eight-pole composite iron 3, are based on a four-eight-pole composite magnet system. This system includes a composite magnet current control device, a composite magnet main power supply, and the four-eight-pole composite magnet itself. The composite magnet current control device controls the current output of the four-pole field coil and the eight-pole field coil of the four-eight-pole composite magnet from the main power supply.

[0016] The common transmission line, along the beam direction, is sequentially equipped with: an accelerator outlet, a beam matching mechanism, a quad-octet composite iron 1, and a diode; the two branch transmission lines are a first branch transmission line and a second branch transmission line; the first branch transmission line is sequentially equipped with a quad-octet composite iron 2, a beam matching and homogenization effect observation mechanism 1, and a terminal 1; the second branch transmission line is sequentially equipped with a quad-octet composite iron 3, a beam matching and homogenization effect observation mechanism 2, and a terminal 2; the common transmission line and the first branch transmission line constitute a first bend-type beam homogenization transmission line; the common transmission line and the second branch transmission line constitute a second bend-type beam homogenization transmission line; the first bend-type beam homogenization transmission line and the second bend-type beam homogenization transmission line operate in a time-division multiplexing manner;

[0017] The beam matching mechanism on the shared transmission line is used to observe the initial state of the beam extracted from the accelerator, adjust the size of the beam envelope in the X or Y direction according to the initial state, and align the beam center with the mechanical center of the beam tube.

[0018] The beam matching and homogenization effect observation mechanism 1 on the first branch transmission line is used to align the beam center and the mechanical center of the beam tube, measure the beam intensity after homogenization by the four-eight-pole composite iron 1 and the four-eight-pole composite iron 2, and observe the weak beam shape and strong beam shape after homogenization.

[0019] The beam matching and homogenization effect observation mechanism 2 on the second branch transmission line is used to align the beam center and the mechanical center of the beam tube, measure the beam intensity after homogenization by the four-eight-pole composite iron 1 and the four-eight-pole composite iron 3, and observe the weak beam shape and strong beam shape after homogenization.

[0020] The diode has a straight side that is symmetrical at the entrance of the symmetrically bent beam and a sloping side that is symmetrical at the exit of the symmetrically bent beam. The direction of inclination of the symmetrical sloping side is the direction of beam bending.

[0021] Furthermore, the beam matching mechanism includes a fluorescent target 1, a quadrupole magnet, and a guide magnet; the fluorescent target 1 provides the tester with the initial beam state; the quadrupole magnet is used to form a large beam envelope in the Y or X direction at the position of the quadrupole-octupole composite iron 1; and the guide magnet is used to align the beam center with the mechanical center of the beam channel.

[0022] Furthermore, the beam matching and homogenization effect observation mechanism 1 on the first branch transmission line includes a guide magnet 2, a Faraday cylinder 1, a fluorescent target 2, and a dual-wire 1. The guide magnet 2 is used to align the beam center with the mechanical center of the beam channel; the Faraday cylinder 1 is used to measure the beam intensity after homogenization; the fluorescent target 2 is used to observe the shape of the weak beam after homogenization; and the dual-wire 1 is used to observe the shape of the strong beam after homogenization. The beam matching and homogenization effect observation mechanism 2 on the second branch transmission line includes a guide magnet 3, a Faraday cylinder 2, a fluorescent target 3, and a dual-wire 2. The guide magnet 3 is used to align the beam center with the mechanical center of the beam channel; the Faraday cylinder 2 is used to measure the beam intensity after homogenization; the fluorescent target 3 is used to observe the shape of the weak beam after homogenization; and the dual-wire 2 is used to observe the shape of the strong beam after homogenization.

[0023] Furthermore, the phase shift of the particles between the target and the four-octap composite iron 1 and four-octap composite iron 2. Or the phase shift of particles between the target and the octapole composite iron 1 and octapole composite iron 3. Multiples close to 180 degrees refer to multiples that are close to but not equal to 180 degrees: Let... for The remainder after 180 degrees, The value is generally less than ±15 degrees.

[0024] Furthermore, the transmission matrix between the two octagonal magnetic fields is close to the identity matrix, that is, the phase shift between the two four-octagonal composite magnets is controlled within a range of 30 degrees. This 30-degree range can greatly avoid the high-order nonlinear effects caused by the coupling of the two octagonal magnets and can achieve a better homogenization effect.

[0025] Furthermore, the expression for the magnetic strength k at the four-eight-pole composite iron 1 and the four-eight-pole composite iron 2, or the magnetic strength k at the four-eight-pole composite iron 1 and the four-eight-pole composite iron 3, is as follows:

[0026]

[0027] Let: the starting point of the transmission line be 0, the position of the first quadrupole magnet be 1, the position of the second quadrupole magnet be 2, and the position of the endpoint, which is the position of the target, be 3; in the above formula (1), ux02 represents the phase shift of the particle in the x direction between positions 0 and 2, ux23 represents the phase shift of the particle in the x direction between positions 2 and 3; βx2 represents the envelope function in the x direction at position 2; in the above formula (2), uy01 represents the phase shift of the particle in the y direction between 0 and 1; uy13 represents the phase shift of the particle in the y direction between 1 and 3; βy1 represents the envelope function in the y direction at position 1.

[0028] Furthermore, the composite magnet current control device includes: a module for establishing two-dimensional sampling points for coil current, a module for experimentally measuring and initially establishing a three-dimensional surface sample library of magnetic field gradient, a module for refining the three-dimensional surface sample library of magnetic field gradient using interpolation, a module for inputting field gradient and solving the corresponding field gradient current curve, a module for solving the intersection point of four / octagonal field gradient current curves, and a module for outputting four / octagonal coil current.

[0029] The module for establishing two-dimensional sampling points for coil current is used to establish a two-dimensional data comparison table of coil current for quadrupole and octupole iron.

[0030] The experimental measurement initially establishes a three-dimensional surface sample library module for magnetic field gradients. This module uses the current values ​​from a two-dimensional data lookup table of coil currents to perform magnetic field experimental measurements on composite iron, thereby obtaining four-pole and octole magnetic field gradient measurement values ​​that correspond one-to-one with the two-dimensional current data lookup table, thus obtaining a three-dimensional surface sample database of magnetic field gradients. The aforementioned three-dimensional surface sample database of magnetic field gradients includes a four-pole field magnetic field gradient three-dimensional surface sample database and an octole field magnetic field gradient three-dimensional surface sample database.

[0031] The module for refining the magnetic field gradient three-dimensional surface sample library using interpolation is used to perform two-dimensional interpolation on the quadrupole magnetic field gradient three-dimensional surface sample database and the octupole magnetic field gradient three-dimensional surface sample database using cubic spline functions, thereby increasing the density of grid points.

[0032] The module for solving the input field gradient corresponding to the current curve is used to intersect the input quadrupole field gradient and octupole field gradient with the magnetic field gradient surface of the three-dimensional sample database, and obtain two corresponding current curves after the intersection; specifically: a quadrupole field magnetic field gradient plane is selected, and this plane intersects with the surface of the quadrupole field magnetic field gradient three-dimensional surface sample database to obtain the current curve that satisfies the quadrupole field gradient; an octupole field magnetic field gradient plane is selected, and this plane intersects with the surface of the octupole field magnetic field gradient three-dimensional surface sample database to obtain the current curve that satisfies the octupole field gradient.

[0033] The module for solving the intersection point of the four / octet field gradient current curves is used to obtain the intersection point of the current curve that satisfies the four-pole field gradient and the current curve that satisfies the octet field gradient, and uses the intersection point as the solution of the composite iron excitation current.

[0034] The output four-pole / eight-pole coil current module outputs four-pole field coil current and eight-pole field coil current to the four-pole / eight-pole composite iron according to the solution of the excitation current of the composite iron.

[0035] Furthermore, this four-eight-pole composite magnet has a total of eight poles. Each pole has two layers of current coils along the radial direction near the large radius. The inner coil is an eight-pole magnetic field excitation coil, and the outer coil is a four-pole magnetic field excitation coil.

[0036] The inner layer of the octagonal magnetic field excitation coil has two adjacent poles with opposite current directions, that is, the octagonal field coil is divided into two groups: poles 1, 3, 5, 7 and poles 2, 4, 6, 8. The excitation currents of the two groups are equal in magnitude but opposite in direction, thereby generating an octagonal magnetic field.

[0037] The outer quadrupole magnetic field excitation coil has four groups, namely poles 1 and 2, poles 3 and 4, poles 5 and 6, and poles 7 and 8. The excitation current of the quadrupole magnetic field coils of poles 1 and 2 and the symmetrically arranged poles 5 and 6 is in the same direction and magnitude. The excitation current of the coils of poles 3 and 4 and the symmetrically arranged poles 7 and 8 is in the same direction and magnitude. The current direction of the coils of poles 1 and 2 is opposite to that of the coils of poles 3 and 4. The current direction of the coils of poles 5 and 6 is opposite to that of the coils of poles 7 and 8. This generates a quadrupole magnetic field.

[0038] Advantages and effects of the present invention

[0039] 1. The present invention comprises a symmetrical bending beam homogenization transmission line consisting of two quadrupole-octupole composite irons and a common dipole iron. It adopts a method of generating a large envelope by using quadrupole-octupole composite irons and quadrupole irons together, which solves the problem that when the existing technology uses separate quadrupole irons and octupoles, the largest part of the envelope is usually occupied by the quadrupole magnetic field, and the role of the octupole iron cannot be fully utilized.

[0040] 2. This invention comprises a symmetrically bent beam homogenization transmission line consisting of two quadrupole-octupole composite irons and a shared dipole iron. Since the quadrupole-octupole composite iron is located at the large envelope, the requirement for the magnetic field strength K value of the quadrupole-octupole composite iron is reduced. This solves the problem that when using discrete quadrupole and octupole irons in the prior art, the beam envelope at the location of octupole iron 1 and octupole iron 2 is small, which makes the field strength requirement of the octupole magnet very high. Excessive magnetic field strength is too costly and difficult to achieve in engineering.

[0041] 3. This invention comprises a symmetrically bent beam homogenization transmission line consisting of two quadrupole-octupole composite irons and a shared dipole iron. Within the aperture of the quadrupole-octupole composite iron, both quadrupole and octupole magnetic fields are generated simultaneously, achieving both focusing and homogenization of the beam envelope. Installing the composite iron on the beam transmission line reduces the number of transmission elements and shortens the transmission line length, solving the problem that when using discrete quadrupole and octupole irons, the excessively long transmission line length leads to increasingly expensive civil engineering for surrounding shielding, a large footprint, and high costs.

[0042] 4. This invention comprises a symmetrically bent beam homogenization transmission line consisting of two quadrature-octet composite magnets and a common diode magnet, which limits the phase shift of particles between the two quadrature-octet composite magnets and the target. The values ​​of the magnetic field strengths k1 and k2 at the first and second four-eight-pole composite magnets are close to integer multiples of 180 degrees (0, 1, 2, 3...), but not equal to integer multiples of 180 degrees (0, 1, 2, 3...), which makes the required magnetic field strengths k1 and k2 at the first and second four-eight-pole composite magnets smaller, which helps to reduce the difficulty and cost of magnet manufacturing.

[0043] 5. The present invention comprises a symmetrical bending beam homogenization transmission line consisting of two four-octagonal composite irons and a common dipolar iron, respectively. The transmission matrix between the two octagonal magnetic fields is limited to a unit matrix, that is, the phase shift between the two four-octagonal composite magnets is controlled within a range of 30 degrees. This 30-degree range can greatly avoid the high-order nonlinear effects caused by the coupling of the two octagonal magnets and can achieve a better homogenization effect. Attached Figure Description

[0044] Figure 1a This is a schematic diagram of the ultra-short symmetrical bending beam homogenization transmission line of the present invention;

[0045] Figure 1b This is a schematic diagram of the transmission line harness current matching mechanism of the present invention;

[0046] Figure 1c This is a schematic diagram comparing the particle distribution state before and after the transmission line homogenization in this invention.

[0047] Figure 1d This is a schematic diagram of the beam matching and homogenization effect observation mechanism 1 of the present invention;

[0048] Figure 1e This is a schematic diagram of the beam matching and homogenization effect observation mechanism 2 of the present invention;

[0049] Figure 1f This invention relates to a method for using a symmetrically bent transmission line diode based on shape change.

[0050] Figure 1g This describes the existing technology for using a single-bend transmission line dipole based on attitude change.

[0051] Figure 2 This is a schematic diagram showing the maximum envelope positions of the four-octet composite iron 1 and 2 of the present invention;

[0052] Figure 3 This is a schematic diagram illustrating the representative meanings of the four points 0, 1, 2, and 3 involved in formulas (1) and (2) of this invention;

[0053] Figure 4 This is a schematic diagram showing the phase difference between the two octet composite iron pieces and the phase difference between the two octet composite iron pieces to the target point.

[0054] Figure 5a This is a schematic diagram of the four / octet composite iron system for beam control according to the present invention;

[0055] Figure 5b This invention provides a novel four / octet composite iron model.

[0056] Figure 5c The arrangement and current direction of the four / octet composite magnet coil.

[0057] Figure 5d This is a schematic diagram showing the current values ​​of the two sets of coils during magnetic field measurement in this invention;

[0058] Figure 5e This is a schematic diagram showing the quadrupole / octapole magnetic field gradients corresponding to different currents measured in the present invention.

[0059] Figure 5f This is a schematic diagram illustrating the use of cubic spline functions for two-dimensional interpolation to refine the grid point density in this invention.

[0060] Figure 5g This is a schematic diagram showing the intersection of the magnetic field gradient plane selected in this invention with the magnetic field gradient surface of the three-dimensional sample database;

[0061] Figure 5h This is a schematic diagram of the current curve corresponding to the four / octet field selected in this invention;

[0062] Figure 5i This is a schematic diagram illustrating the solution for the composite iron excitation current of the present invention;

[0063] Figure 6This is a schematic diagram of an existing octet iron in the small envelope position.

[0064] Figure 7 This is a schematic diagram of an embodiment of the ultra-short symmetrical bending beam homogenization transmission line of the present invention; Detailed Implementation

[0065] Design principle of the invention

[0066] One of the innovations lies in the invention of a four-octet composite iron. (The text abruptly ends here, seemingly mid-sentence.) Figure 5b , 5c The octet composite iron shown is replaced by, for example Figure 6 The discrete components shown are tetrapole and octapole iron. One effect is that after being combined, the tetrapole and octapole magnetic fields are generated within the aperture of the tetrapole-octapole composite iron, with the following effect: Figure 2 As shown: the quadrupole and octupole share the positions of the large envelopes in the Y and X directions. The reason they can share the positions of the large envelopes in the Y or X directions is that the quadrupole-octupole composite iron 1 and the quadrupole preceding it coexist in the large envelope in the Y direction; the quadrupole-octupole composite iron 2 and the quadrupole of the quadrupole-octupole composite iron 1 preceding it coexist in the large envelope in the X direction. Because the octupoles in the quadrupole-octupole composite iron 1 and 2 are positioned within the large envelope, a better beam homogenization effect can be achieved, that is, it can simultaneously achieve the functions of focusing and homogenizing the beam envelope. Compared to... Figure 6 The existing technology, due to the separate arrangement of quadrupole and octupole magnets, 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, resulting in poor homogenization. Secondly, installing composite magnets on the beam transmission line can reduce the number of transmission elements, shorten the transmission line length, and reduce the engineering cost of the beam transmission line. This reduction in the number of transmission elements not only saves on quadrupole magnets but also saves on the multiple additional components required to achieve the same homogenization effect on the transmission line.

[0067] The second innovation lies in the invention of a four / octagonal composite magnet current control system and a four / octagonal composite iron excitation current design method. First, the design challenge of the four / octagonal composite iron excitation current lies in the coupling relationship between the multipole magnetic fields generated by the two sets of coils. This coupling means that changing the current magnitude of the four-pole or octagonal field coil will simultaneously change the original four-pole and octagonal magnetic field gradients of the magnet. Therefore, the one-to-one adjustment strategy of the current magnetic field gradient for a single type of magnet is no longer applicable. In composite magnets, if the current magnitude of the four-pole field coil is adjusted first to meet the usage requirements, and then the current magnitude of the octagonal field coil is adjusted, any change in the octagonal field coil current will alter the previously adjusted four-pole magnetic field gradient, causing it to no longer meet the usage requirements. Second, the innovative design of the four / octagonal composite magnet current control system and the four / octagonal composite iron excitation current design method solves the problem of the coupling relationship between the multipole magnetic fields generated by the two sets of coils in the four / octagonal composite iron, and finds the current intersection point that simultaneously satisfies the four-pole and octagonal field gradients. The system is like Figure 5a As shown, it includes: a two-dimensional sampling point module based on coil current, a three-dimensional surface sample library module based on experimentally measured initial magnetic field gradient, a three-dimensional surface sample library module based on interpolation algorithm for refined magnetic field gradient, a current curve module for solving the corresponding field gradient based on field gradient input, a current curve intersection module based on field gradient solution, and a module for outputting four-pole / eight-pole coil current.

[0068] The design method for the excitation current of a four / octet composite iron is as follows:

[0069] Step 1, such as Figure 5d As shown, a two-dimensional data comparison table for coil currents of four-pole and eight-pole composite iron is established; this two-dimensional data comparison table is based on the two-dimensional data comparison table for coil currents of four / eight-pole composite iron; the above two-dimensional data comparison table for coil currents is as follows. Figure 5d As shown, the horizontal axis represents the current in the four-pole coil, and the vertical axis represents the current in the four-pole coil.

[0070] Step Two, as follows Figure 5e As shown, experimental measurements were performed to obtain the four-pole and octole magnetic field gradient measurement values ​​that correspond one-to-one with the two-dimensional current data comparison table, thereby obtaining a three-dimensional surface sample database of magnetic field gradients; the above three-dimensional surface sample database of magnetic field gradients includes a three-dimensional surface sample database of four-pole field magnetic field gradients and a three-dimensional surface sample database of octole field magnetic field gradients.

[0071] The above three-dimensional surface sample database Figure 5e As shown, the current of the four-pole coil is used as the X-axis coordinate, the current of the eight-pole coil is used as the Y-axis coordinate, and the magnetic field gradient is used as the Z-axis coordinate.

[0072] Step 3, as follows Figure 5f As shown, cubic spline functions are used to perform two-dimensional interpolation on the three-dimensional surface sample database of the quadrupole magnetic field gradient and the octupole magnetic field gradient, thereby increasing the density of the grid points.

[0073] The effect of the above-mentioned encrypted grid point density is as follows: Figure 5f As shown, the grid density on the X, Y, and Z axes has increased.

[0074] Step 4, as follows Figure 5g As shown, a quadrupole magnetic field gradient plane is selected, which intersects with the surface of the quadrupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the quadrupole gradient; an octupole magnetic field gradient plane is selected, which intersects with the surface of the octupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the octupole gradient.

[0075] Step 5, as follows Figure 5h As shown, the current curves satisfying the quadrupole field gradient and the octupole field gradient are obtained in the two-dimensional data grid plane of the coil current, and the intersection point of the two current curves is finally determined.

[0076] Step Six, as Figure 5i As shown, the intersection point is used as the solution for the excitation current of the composite iron.

[0077] The third innovation lies in the invention of an ultra-short symmetrical bending beam homogenization transmission line and a diode for the ultra-short symmetrical bending beam homogenization transmission line.

[0078] First, such as Figure 2 As shown, the ultra-short symmetrical bending beam homogenization transmission line uses two quadrupole composite irons on the transmission line. The quadrupole composite iron 1 and the quadrupole in front of it coexist with a large envelope in the Y direction. The large envelope is generated because the quadrupole in front is defocused and the dashed line is upward, while the quadrupole in the back is focused and the dashed line is downward. The large envelope in the Y direction is generated at the intersection of the two dashed lines. The quadrupole composite iron 2 and the quadrupole in front of it coexist with a large envelope in the X direction. The large envelope is generated because the quadrupole in front is defocused and the solid line is upward, while the quadrupole in the back is focused and the solid line is downward. The large envelope in the X direction is generated at the intersection of the two solid lines.

[0079] like Figure 2As shown, the ultrashort symmetrical bending beam homogenization transmission line employs two quadrupole-octupole composite irons and a diode in between on the transmission line. The diode is used to bend the direction of the beam. The innovation lies in the fact that this ultrashort symmetrical bending beam homogenization transmission line utilizes the combined focusing effect of the quadrupole-octupole composite iron 1 and the diode to generate a beam waist in the Y direction near the quadrupole-octupole composite iron 2. The envelope size in the X direction on the target is generated by superimposing the quadrupole fields of the diode and the quadrupole-octupole composite iron 2, making the envelope sizes in the X and Y directions consistent. Specifically, at the current intersection point of the quadrupole-octupole composite iron 1, the quadrupole current of the quadrupole-octupole composite iron 1 is appropriately reduced. The edge field focusing effect of the diode behind the quadrupole composite iron 1 and the quadrupole focusing effect of the quadrupole composite iron 1 itself are superimposed to generate the waist in the Y direction at the quadrupole-octupole composite iron 2. At the current intersection point of the four-eight-pole composite iron 2, the quadrupole current of the four-eight-pole composite iron 2 is appropriately reduced. The focusing effect of the edge field of the diode iron outlet behind the four-eight-pole composite iron 1 and the focusing effect of the quadrupole iron of the four-eight-pole composite iron 2 itself are superimposed to generate the envelope size in the X direction on the target, so that the envelope size in the X direction and the Y direction are consistent.

[0080] Third, such as Figure 1f As shown, the diode used for the ultra-short symmetrical bending beam homogenization transmission line is a common diode on the ultra-short symmetrical bending beam homogenization transmission line. The common diode has an exit edge with symmetrical upper and lower edge angles. Specifically, its beam inlet edge is a straight line, and its beam outlet edge is a pair of symmetrical upper and lower oblique lines. The inclination direction of the symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting the center of the beam bending track to the beam at the diode outlet forms the diode outlet edge angle. By changing the size of the diode outlet edge angle, the edge field focusing effect of the diode is adjusted, and in conjunction with the envelopes of the four-octet composite irons on both sides of the diode in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

[0081] The fourth innovation lies in finding a balance between transmission line homogenization, avoiding nonlinear effects caused by coupling, and shortening the transmission line. For example... Figure 2 As shown, the homogenization effect of the ultra-short bend transition beam homogenization transmission line is significant, stemming from innovations in three aspects. All three are indispensable and must support each other to achieve the desired homogenization effect:

[0082] The first aspect is to ensure uniformity as a premise. Specifically, two octet composite irons are used on the transmission line. The octet in front of octet composite iron 1 and its own octet are used to generate a large envelope in the Y direction at octet composite iron 1. The octet in front of octet composite iron 1 and its own octet are used to generate a large envelope in the X direction at octet composite iron 2.

[0083] The second aspect: Solving the problem of optimizing the homogenization effect: specifically as follows Figure 4 As shown, this is achieved through the phase shift between the four-octet composite magnet 1 and the target. The phase shift between the four-octet composite magnet 2 and the target is close to an integer multiple of 180 degrees (0, 1, 2, 3…). It is achieved by applying multiples of 0 degrees. The homogenization effect is best when the angle is close to 180 degrees and close to 0 degrees.

[0084] The third aspect is to avoid nonlinear effects caused by coupling while ensuring homogenization. These nonlinear effects occur when two octet composite iron pieces are used together; improper handling can lead to nonlinear coupling. When nonlinear coupling occurs, the particle amplitude increases, causing particle loss, which reduces the homogenization effect. Therefore, to avoid nonlinear coupling, this invention approximates the transmission matrix between the two octet magnetic fields of the two octet composite iron pieces to a unit matrix, specifically as follows: Figure 3 , Figure 4 As shown, the near-identical matrix means that the phase difference between the first four-octet composite iron (point 1) and the second four-octet composite iron (point 2) is close to 0 degrees and less than 30 degrees. At this point, the required magnetic field strength for the octet magnet is relatively small, and the nonlinear effect caused by coupling is also smaller, resulting in better homogenization.

[0085] The difference between this invention and existing technologies lies in the fact that the transmission matrix between the two octagonal magnetic fields in existing technologies is "equal to the identity matrix" rather than "close to the identity matrix," while the transmission matrix between the two octagonal magnetic fields in this invention is "close to the identity matrix" rather than "equal to the identity matrix." That is, the phase difference between the first four-octagonal composite iron (point 1) and the second four-octagonal composite iron (point 2) is close to 0 degrees rather than equal to 0 degrees, and less than 30 degrees rather than equal to 30 degrees. The significance of using "close to" rather than "equal to" in this invention is to shorten the transmission line. If the method of "equal to the identity matrix" were used, many more components would need to be added to the transmission line, resulting in a very long transmission line. This invention adopts a "sufficient" approach to address the issue of "avoiding nonlinear effects caused by coupling": when the phase difference between the first four-octagonal composite iron (point 1) and the second four-octagonal composite iron (point 2) is close to 0 degrees and less than 30 degrees, it effectively shortens the transmission line length while also satisfying the requirement of "avoiding nonlinear effects caused by coupling." A balance is found between transmission line homogenization, avoiding nonlinear effects caused by coupling, and shortening the transmission line.

[0086] Based on the principles of the present invention, the present invention designs an ultra-short symmetrical bending beam homogenization transmission line, such as... Figure 1a , Figure 1b , Figure 1c , Figure 1d , 1e As shown, its characteristics are: the transmission line is a symmetrical bending beam homogenization transmission line that contains two quadrature octet composite irons and one common diode iron; the symmetrical bending beam homogenization transmission line that contains two quadrature octet composite irons and one common diode iron consists of one common transmission line and two branch transmission lines.

[0087] like Figure 1a As shown, the common transmission line is provided with the following components along the beam direction: an accelerator outlet, a beam matching mechanism, a quad-octet composite iron 1, and a diode; the two branch transmission lines are a first branch transmission line and a second branch transmission line; the first branch transmission line is provided with a quad-octet composite iron 2, a beam matching and homogenization effect observation mechanism 1, and a terminal 1; the second branch transmission line is provided with a quad-octet composite iron 3, a beam matching and homogenization effect observation mechanism 2, and a terminal 2; the common transmission line and the first branch transmission line form a first curved beam homogenization transmission line; the common transmission line and the second branch transmission line form a second curved beam homogenization transmission line; the first curved beam homogenization transmission line and the second curved beam homogenization transmission line operate in a time-division multiplexing manner;

[0088] The four-pole and eight-pole composite iron 1, four-pole and eight-pole composite iron 2, and four-pole and eight-pole composite iron 3 of the first and second bend-transformer beam homogenization transmission lines generate four-pole magnetic fields and eight-pole magnetic fields simultaneously, so that the functions of four-pole and eight-pole iron can be realized simultaneously by installing only one transmission element.

[0089] like Figure 2 As shown, the beam homogenization transmission line of the first curved beam reaches a large value in the Y or X direction at the four-octap composite iron 1, and the beam envelope function in the X or Y direction reaches a large value at the four-octap composite iron 2; the phase shift of the particle between the four-octap composite iron 1 and four-octap composite iron 2 and the target. They are all close to integer multiples of 180 degrees (0, 1, 2, 3...); the transmission matrix between the two octagonal magnetic fields is close to the identity matrix;

[0090] The diodes on this ultrashort symmetrical bend beam homogenization transmission line are shared diodes on the ultrashort symmetrical bend beam homogenization transmission line. These shared diodes have symmetrical upper and lower edge angles at their exit edges. Specifically, their beam inlet edge is a straight line, and their beam outlet edge is a pair of symmetrical upper and lower oblique lines. The inclination direction of these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting these symmetrical oblique lines and the center of the beam bending trajectory to the beam at the diode outlet forms the diode outlet edge angle. By changing the size of the diode outlet edge angle, the edge field focusing effect of the diode is adjusted, and in conjunction with the envelopes of the four-octet composite irons on both sides of the diode in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

[0091] like Figure 2 As shown, the second curved beam homogenization transmission line reaches a large value in either the Y or X direction at the octet composite iron 1, and a large value in either the X or Y direction at the octet composite iron 3. The phase shift of the particle between the octet composite iron 1 and octet composite iron 3 and the target... They are all close to integer multiples of 180 degrees (0, 1, 2, 3...); the transmission matrix between the two octagonal magnetic fields is close to the identity matrix;

[0092] like Figure 5a As shown, the four-eight-pole composite iron 1, four-eight-pole composite iron 2, and four-eight-pole composite iron 3 of the first and second bend-transformer beam homogenization transmission lines are based on a four-eight-pole composite magnet system. The four-eight-pole composite magnet system includes a composite magnet current control device, a composite magnet main power supply, and four-eight-pole composite magnets. The composite magnet current control device is used to control the current output of the four-pole field coil and the eight-pole field coil of the four-eight-pole composite magnet by the composite magnet main power supply.

[0093] like Figure 1b , 1c As shown, the beam matching mechanism on the shared transmission line is used to observe the initial state of the beam extracted from the accelerator, and adjust the size of the beam envelope in the X or Y direction according to the initial state, and align the beam center with the mechanical center of the beam tube.

[0094] like Figure 1d As shown, the beam matching and homogenization effect observation mechanism 1 on the first branch transmission line is used to align the beam center and the mechanical center of the beam tube, measure the beam intensity after homogenization by the four-eight-pole composite iron 1 and the four-eight-pole composite iron 2, and observe the weak beam shape and strong beam shape after homogenization.

[0095] like Figure 1eAs shown, the beam matching and homogenization effect observation mechanism 2 on the second branch transmission line is used to align the beam center and the mechanical center of the beam tube, measure the beam intensity after homogenization by the four-eight-pole composite iron 1 and the four-eight-pole composite iron 3, and observe the weak beam shape and strong beam shape after homogenization.

[0096] like Figure 1f As shown, the diode has a straight side that is symmetrically bent at the entrance of the beam and a symmetrically bent side that is inclined at the exit of the beam. The inclination direction of the symmetrical inclined side is the direction of beam bending.

[0097] Supplementary Note 1:

[0098] like Figure 1f As shown, the function of the aforementioned diode is to bend the beam, and at the same time, as Figure 2 As shown, the beam will also be focused in the X and Y directions after passing through the diode. In the design of ultra-short bending beamlines, in order to shorten the transmission line length, it is necessary to adjust the arrangement of the beam elements so that the first quadrupole and the diode are close together, making full use of the edge field focusing effect of the diode, while obtaining an ideal phase shift that meets the homogenization requirements.

[0099] Traditional methods such as Figure 1g As shown, the use of a diode is for unidirectional beam deflection. In this embodiment, when designing a symmetrical bending beamline, it is required that the beam enters the diode and exits from two symmetrical directions. Therefore, a new type of diode is adopted, such as... Figure 1f As shown, the beam enters the dipole perpendicularly. By adjusting the direction of the magnetic field, the direction of beam deflection can be controlled. Furthermore, to achieve better homogenization, when designing a symmetrically bent beamline, the exit edge angle E2 can be modified to control the focusing strength of the dipole's edge field in the X and Y directions. E2 is the angle between the beam direction at the beam exit edge and the dipole's exit edge. Adjusting the angle E2 only changes the shape of the dipole beam exit edge. Figure 1g A pair of oblique lines symmetrically positioned at the exit edge of the electromagnet beam. The inclination direction of each of these oblique lines is the direction in which the beam bends at the exit edge.

[0100] like Figure 1b As shown, the beam matching mechanism includes a fluorescent target 1, a quadrupole magnet, and a guide magnet; the fluorescent target 1 provides the tester with the initial beam state; the quadrupole magnet is used to form a large beam envelope in the Y or X direction at the position of the quadrupole-octupole composite iron 1; and the guide magnet is used to align the beam center with the mechanical center of the beam channel.

[0101] like Figure 1d , 1eAs shown, the beam matching and homogenization effect observation mechanism 1 on the first branch transmission line includes a guide magnet 2, a Faraday cylinder 1, a fluorescent target 2, and a dual-wire 1. The guide magnet 2 is used to align the beam center with the mechanical center of the beam channel; the Faraday cylinder 1 is used to measure the beam intensity after homogenization; the fluorescent target 2 is used to observe the shape of the weak beam after homogenization; and the dual-wire 1 is used to observe the shape of the strong beam after homogenization. The beam matching and homogenization effect observation mechanism 2 on the second branch transmission line includes a guide magnet 3, a Faraday cylinder 2, a fluorescent target 3, and a dual-wire 2. The guide magnet 3 is used to align the beam center with the mechanical center of the beam channel; the Faraday cylinder 2 is used to measure the beam intensity after homogenization; the fluorescent target 3 is used to observe the shape of the weak beam after homogenization; and the dual-wire 2 is used to observe the shape of the strong beam after homogenization.

[0102] like Figure 4 As shown, the phase shift of the particle between the target and the octapole composite iron 1 and octapole composite iron 2. Or the phase shift of particles between the target and the octapole composite iron 1 and octapole composite iron 3. Multiples close to 180 degrees refer to multiples that are close to but not equal to 180 degrees: Let... for The remainder after 180 degrees, The value is generally less than ±15 degrees.

[0103] Supplementary Note 2:

[0104] The aforementioned "phase shift of the particle between the two octet composite magnets and the target" The degrees are respectively close to integer multiples of 180 degrees (0, 1, 2, 3...) but not equal to 180 degrees. The principle is explained in formulas (1) and (2) below:

[0105]

[0106] In formula (1), since the molecule's Csc[ux23] = 1 / sin[ux23], when ux23 approaches 180°, sin[ux23] tends to 0, and Csc[ux23] tends to infinity; similarly, in formula (2), the molecule's Csc[uy13] = 1 / sin[uy13], when ux13 approaches 180°, sin[ux13] tends to 0, and Csc[uy13] tends to infinity; therefore, the phase shift of the particle between the two quadrupole composite magnets and the target... Each is an integer multiple of 180 degrees (0, 1, 2, 3...).

[0107] like Figure 4As shown, the transmission matrix between the two octagonal magnetic fields is close to the identity matrix, that is, the phase shift between the two four-octagonal composite magnets is controlled within a range of 30 degrees. This 30-degree range can greatly avoid the high-order nonlinear effects caused by the coupling of the two octagonal magnets and can achieve a better homogenization effect.

[0108] Furthermore, the expression for the magnetic strength k at the four-eight-pole composite iron 1 and the four-eight-pole composite iron 2, or the magnetic strength k at the four-eight-pole composite iron 1 and the four-eight-pole composite iron 3, is as follows:

[0109]

[0110] Let: the starting point of the transmission line be 0, the position of the first quadrupole magnet be 1, the position of the second quadrupole magnet be 2, and the position of the endpoint, which is the position of the target, be 3; in the above formula (1), ux02 represents the phase shift of the particle in the x direction between positions 0 and 2, ux23 represents the phase shift of the particle in the x direction between positions 2 and 3; βx2 represents the envelope function in the x direction at position 2; in the above formula (2), uy01 represents the phase shift of the particle in the y direction between 0 and 1; uy13 represents the phase shift of the particle in the y direction between 1 and 3; βy1 represents the envelope function in the y direction at position 1.

[0111] Supplementary Note 3

[0112] The derivation process of the above formulas (1) and (2) is briefly described as follows: In the reference "Yosuke Yuri, Uniformization of the transverse beam profile by means of nonlinear focusing method[J]. Physical Review Special Topics-Accelerators and Beams,2007.DOI:10.1103 / physrevstab.10.104001.", the formula for the octagonal magnetic field strength in a single direction is given. This formula only considers an octagonal magnet and the subsequent transmission section. In order to more accurately describe the relationship between the octagonal magnetic field strength and the transmission line design, we extend the formula to consider the influence of the matching section from the accelerator exit to the octagonal magnet on the beam homogenization. The parameters involved are ux02 (phase shift in the x direction between positions 0 and 2), ux23 (phase shift in the x direction between positions 2 and 3), uy01 (phase shift in the x direction between positions 0 and 2), and uy13 (phase shift in the x direction between positions 2 and 3). Using the same "higher-order transport mapping" derivation method as in the references, we obtain the expressions (1) and (2) for the magnetic strength k at the first four-octet composite magnet and the second four-octet composite magnet.

[0113] like Figure 5a As shown, the composite magnet current control device includes: a module for establishing two-dimensional sampling points for coil current; a module for experimentally measuring and initially establishing a three-dimensional surface sample library of magnetic field gradient; a module for refining the three-dimensional surface sample library of magnetic field gradient using interpolation; a module for inputting field gradient and solving the corresponding field gradient current curve; a module for solving the intersection point of four / octagonal field gradient current curves; and a module for outputting four / octagonal coil current.

[0114] like Figure 5d As shown, the module for establishing two-dimensional sampling points for coil current is used to establish a two-dimensional data comparison table of coil current for quadrupole and octupole iron.

[0115] like Figure 5e As shown, the experimental measurement initially establishes a three-dimensional surface sample library module for magnetic field gradients. This is achieved by using the current values ​​from a two-dimensional data lookup table of coil currents to perform magnetic field experimental measurements on composite iron, thereby obtaining four-pole and octole magnetic field gradient measurement values ​​that correspond one-to-one with the two-dimensional current data lookup table, thus obtaining a three-dimensional surface sample database of magnetic field gradients. The aforementioned three-dimensional surface sample database of magnetic field gradients includes a four-pole field magnetic field gradient three-dimensional surface sample database and an octole field magnetic field gradient three-dimensional surface sample database.

[0116] like Figure 5f As shown, the module for refining the three-dimensional surface sample library of magnetic field gradient using interpolation is used to perform two-dimensional interpolation on the three-dimensional surface sample database of quadrupole magnetic field gradient and the three-dimensional surface sample database of octupole magnetic field gradient using cubic spline functions, thereby increasing the density of grid points.

[0117] like Figure 5g , 5h As shown, the input field gradient solution module for corresponding field gradient current curves is used to intersect the input quadrupole field gradient and octupole field gradient with the magnetic field gradient surface of the three-dimensional sample database, and obtain two corresponding current curves after the intersection; specifically: a quadrupole field magnetic field gradient plane is selected, and this plane intersects with the surface of the quadrupole field magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the quadrupole field gradient; an octupole field magnetic field gradient plane is selected, and this plane intersects with the surface of the octupole field magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the octupole field gradient.

[0118] like Figure 5i As shown, the module for solving the intersection point of the four / octet field gradient current curves is used to obtain the intersection point of the current curve that satisfies the four-pole field gradient and the current curve that satisfies the octet field gradient, and uses the intersection point as the solution of the composite iron excitation current.

[0119] The output four-pole / eight-pole coil current module outputs four-pole field coil current and eight-pole field coil current to the four-pole / eight-pole composite iron according to the solution of the excitation current of the composite iron.

[0120] like Figure 5b , 5c As shown, this four-eight-pole composite magnet has a total of eight poles. Each pole has two layers of current coils along the radial direction near the large radius. The inner coil is an eight-pole magnetic field excitation coil, and the outer coil is a four-pole magnetic field excitation coil.

[0121] like Figure 5b , 5c As shown, the inner layer of the octagonal magnetic field excitation coil has two adjacent poles with opposite current directions, that is, the octagonal field coil is divided into two groups: poles 1, 3, 5, 7 and poles 2, 4, 6, 8. The excitation currents of the two groups are equal in magnitude but opposite in direction, thereby generating an octagonal magnetic field.

[0122] like Figure 5b , 5c As shown, the outer quadrupole magnetic field excitation coil has four groups, with the coils on two adjacent poles forming a group: poles 1 and 2, poles 3 and 4, poles 5 and 6, and poles 7 and 8. The excitation current of the quadrupole magnetic field coils on poles 1 and 2, and symmetrically arranged on poles 5 and 6, is in the same magnitude and direction. The excitation current of the coils on poles 3 and 4, and symmetrically arranged on poles 7 and 8, is in the same magnitude and direction. The current direction of the coils on poles 1 and 2 is opposite to that of the coils on poles 3 and 4, and the current direction of the coils on poles 5 and 6 is opposite to that of the coils on poles 7 and 8, thus generating a quadrupole magnetic field.

[0123] Example 1

[0124] like Figure 7 As shown, this invention designs an ultrashort symmetrical bendable beam homogenization transmission line. When the total length of the ultrashort symmetrical bendable beam homogenization transmission line is 6.5 meters, the initial placement positions of the components that enable the streamline to achieve a better homogenization effect are as follows: the initial position of the fluorescent target 1 is 100 mm; the initial position of the quadrupole magnet (Q0) is 700 mm; the initial position of the guide magnet 1 is 1100 mm; the initial position of the quadrupole-octupole composite iron (Q1) is 1600 mm; the initial position of the dipole iron is 2200 mm; the initial position of the quadrupole-octupole composite iron (Q2 / Q3) is 3500 mm; the initial position of the guide magnet 2 / 3 is 4200 mm; the initial position of the Faraday cylinder 1 / 2 is 4800 mm; the initial position of the fluorescent target 2 / 3 is 5500 mm; the initial position of the dual wire 1 / 2 is 6000 mm; and the initial position of the terminal 1 / 2 is 6500 mm.

[0125] The magnetic field component of the tetrapole iron (Q0) is 6 (T / m); the tetrapole magnetic field component of the tetrapole-octapole composite iron (Q1) is 2.6 (T / m), and the octapole magnetic field component is 3.5e3 (T / m). 3 The quadrupole magnetic field component of the four-pole / octupole composite iron (Q2 / Q3) is 0.55 (T / m), and the octupole magnetic field component is 3e3 (T / m). 3 The inlet edge angle of the diode is 0°, the outlet edge angle is 32°, and the beam bends at 45°.

[0126] like Figure 1c The image shows a comparison of the transmission line before and after homogenization according to the present invention. Figure 1c The left figure is a cross-section of the beam with a Gaussian distribution before homogenization, which is the beam cross-section of the fluorescent target 1 at the position of 100mm of the transmission line. Figure 1c The right figure shows the beam cross-section after homogenization, that is, the beam cross-section with 2 / 3 of the fluorescent target placed at the 5500mm position of the transmission line. As can be seen from the figure, before homogenization, the particle distribution on the beam cross-section was dense in the middle and sparse around the edges. After homogenization, the particle distribution on the beam cross-section is uniform in both the middle and around the edges.

[0127] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. An ultrashort symmetrically bent beam homogenizer transmission line, characterized by: The transmission line is a symmetrically bent transmission line for beam homogenization, which comprises two four-octupole compound magnets and one common diode magnet. The common beam line is provided with an accelerator exit, a beam matching mechanism, a four-octupole compound magnet 1 and a diode magnet in sequence along the beam direction. The first branch beam line is provided with a four-octupole compound magnet 2, a beam matching and homogenization effect observation mechanism 1 and a terminal 1 in sequence. The first bending type beam homogenization transmission line reaches a larger value of the beam envelope function in the Y direction or the X direction at the four-octupole composite iron 1, and reaches a larger value of the beam envelope function in the X direction or the Y direction at the four-octupole composite iron 2; the phase shift of the particles between the four-octupole composite iron 1, the four-octupole composite iron 2 and the target Respectively close to integer multiples of 180 degrees; the transmission matrix between the two octupole magnetic fields is close to a unit matrix; The second bending type beam current homogenization transmission line reaches a larger value of the beam envelope function in the Y direction or the X direction at the four-octupole composite iron 1, reaches a larger value of the beam envelope function in the X direction or the Y direction at the four-octupole composite iron 3, and the phase shift of the particles between the four-octupole composite iron 1 and the four-octupole composite iron 3 and the target Respectively close to integer multiples of 180 degrees; the transmission matrix between the two octupole magnetic fields is close to a unit matrix; Set For With the remainder of 180 degrees, The value is Degrees, Degrees; the transmission matrix between two octupole magnetic fields is close to the unit matrix, that is, the phase shift control between the front and rear four-octupole composite magnets is within 30 degrees; The second branch beam line is provided with a four-octupole compound magnet 3, a beam matching and homogenization effect observation mechanism 2 and a terminal 2 in sequence. The four-octupole compound magnets 1, 2 and 3 of the first and second bent transmission lines for beam homogenization simultaneously generate quadrupole and octupole magnetic fields, so that the functions of the quadrupole and octupole magnets can be realized simultaneously by installing only one transmission element. The four-octupole compound magnet 1 and the diode magnet are used to generate a beam waist in the Y direction near the four-octupole compound magnet 2 by the focusing effect of the two magnets. The diode magnet and the four-octupole compound magnet 2 are used to generate the envelope size in the X direction on the target by the quadrupole field of the two magnets, so that the envelope sizes in the X and Y directions are consistent. The four-octupole compound magnet system comprises a compound magnet current control device, a compound magnet main power supply and a four-octupole compound magnet. The beam matching mechanism on the common beam line is used to observe the initial state of the beam from the accelerator, adjust the envelope size in the X or Y direction of the beam according to the initial state, and center the beam center and the mechanical center of the beam pipe. The beam matching and homogenization effect observation mechanism 1 on the first branch beam line is used to center the beam center and the mechanical center of the beam pipe, measure the beam intensity after homogenization by the four-octupole compound magnets 1 and 2, and observe the weak beam shape and strong beam shape after homogenization. The beam matching and homogenization effect observation mechanism 2 on the second branch beam line is used to center the beam center and the mechanical center of the beam pipe, measure the beam intensity after homogenization by the four-octupole compound magnets 1 and 3, and observe the weak beam shape and strong beam shape after homogenization. The dipole iron is a dipole iron satisfying the symmetric bending type beam homogenization, the dipole iron is a straight edge symmetrically arranged on the inlet side of the symmetric bending beam, and is a symmetrically inclined edge on the outlet side of the symmetric bending beam, the inclined direction of the symmetric inclined edge is the bending direction of the beam; the symmetrically inclined edge and the center of the bending track of the beam to the line connecting the beam at the outlet of the dipole iron form a dipole iron outlet edge angle; the edge field focusing effect of the dipole iron is adjusted by changing the size of the dipole iron outlet edge angle, and the Y direction envelope and the X direction envelope of the four-octupole composite iron on both sides of the dipole iron are matched, so that the ideal phase shift meeting the homogenization requirement is obtained.

2. The ultra-short symmetrically bent beam homogenizer transport line of claim 1, wherein: The beam matching mechanism comprises a fluorescent target 1, a quadrupole magnet and a guide magnet; the fluorescent target 1 provides the initial state of the beam for the tester; the quadrupole magnet is used to form a large beam envelope in the Y direction or the X direction at the position of the four-octupole composite iron 1, and the guide magnet is used to center the beam center and the mechanical center of the beam pipe.

3. The ultra-short symmetrically bent beam homogenizer transport line of claim 1, wherein: The beam matching and homogenization effect observation mechanism 1 on the first branch beam line comprises a guide magnet 2, a Faraday cylinder 1, a fluorescent target 2 and a double wire 1, the guide magnet 2 is used to center the beam center and the mechanical center of the beam pipe; the Faraday cylinder 1 is used to measure the beam current after homogenization, the fluorescent target 2 is used to observe the shape of the weak beam after homogenization, and the double wire 1 is used to observe the shape of the strong beam after homogenization; the beam matching and homogenization effect observation mechanism 2 on the second branch beam line comprises a guide magnet 3, a Faraday cylinder 2, a fluorescent target 3 and a double wire 2, the guide magnet 3 is used to center the beam center and the mechanical center of the beam pipe; the Faraday cylinder 2 is used to measure the beam current after homogenization; the fluorescent target 3 is used to observe the shape of the weak beam after homogenization; and the double wire 2 is used to observe the shape of the strong beam after homogenization.

4. The ultra-short symmetrically bent beam homogenizer transport line of claim 1, wherein: The expression of the magnet strength k at the four-octupole composite iron 1 and the four-octupole composite iron 2, or the magnet strength k at the four-octupole composite iron 1 and the four-octupole composite iron 3 is: Supposing that the starting point of the transmission line is 0, the position of the first four-octupole magnet is 1, the position of the second four-octupole magnet is 2, and the position of the end point, that is, the position of the target, is 3; ux02 in the above formula (1) represents the phase shift of the particle in the x direction between positions 0 and 2, and ux23 represents the phase shift of the particle in the x direction between positions 2 and 3; βx2 represents the envelope function in the x direction at position 2; uy01 in the above formula (2) represents the phase shift of the particle in the y direction between positions 0 and 1; uy13 represents the phase shift of the particle in the y direction between positions 1 and 3; and βy1 represents the envelope function in the y direction at position 1.

5. The ultra-short symmetrical bent beam uniformization transmission line of claim 1, wherein: The composite magnet current control device comprises: a two-dimensional sampling point module for establishing coil current, an experimental measurement preliminary three-dimensional curved surface sample library module for establishing magnetic field gradient, an interpolation refinement three-dimensional curved surface sample library module for using magnetic field gradient, an input field gradient solving corresponding field gradient current curve module, a solving four / eight pole field gradient current curve intersection point module, and an output four / eight pole coil current module; The two-dimensional sampling point module for establishing coil current is used to establish a two-dimensional data comparison table of the coil current of the quadrupole iron and the octupole iron; The experiment measures preliminary establishment magnetic field gradient three-dimensional curved surface sample library module, is using coil current two-dimensional data control table current value to carry out magnetic field experiment measurement to composite iron, thereby obtaining four, eight pole magnetic field gradient measurement value corresponding to two-dimensional current data control table one to one, thereby obtaining the three-dimensional curved surface sample database of magnetic field gradient; The three-dimensional curved surface sample database of magnetic field gradient includes the four-pole field magnetic field gradient three-dimensional curved surface sample database, and the eight-pole field magnetic field gradient three-dimensional curved surface sample database; The interpolation refinement magnetic field gradient three-dimensional curved surface sample library module is used for carrying out two-dimensional interpolation on the four-pole field magnetic field gradient three-dimensional curved surface sample database and the eight-pole field magnetic field gradient three-dimensional curved surface sample database by using cubic spline function, and the grid point density is encrypted; 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 surface of the three-dimensional sample database, obtaining two corresponding current curves after intersection; Specifically: selecting a four-pole field magnetic field gradient plane, the plane intersects the curved surface of the four-pole field magnetic field gradient three-dimensional curved surface sample database, obtaining the current curve satisfying the four-pole field gradient; Selecting an eight-pole field magnetic field gradient plane, the plane intersects the curved surface of the eight-pole field magnetic field gradient three-dimensional curved surface sample database, obtaining the current curve satisfying the eight-pole field gradient; 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 of the composite iron; The four / eight-pole coil current output module outputs the four-pole field coil current and the eight-pole field coil current to the four / eight-pole composite iron according to the solution of the excitation current of the composite iron.

6. The ultra-short, symmetrically bent beam homogenization transmission line of claim 1, wherein: The four / eight-pole composite magnet has eight pole heads, and each pole head is provided with inner and outer two layers of current coils along the radial direction near the major radius. The inner layer coil is an eight-pole magnetic field excitation coil, and the outer layer coil is a four-pole magnetic field excitation coil. The eight-pole magnetic field excitation coil of the inner layer has opposite current directions of adjacent two pole heads, that is, the eight-pole field coils are divided into two groups of 1, 3, 5, 7 pole heads and 2, 4, 6, 8 pole heads. The excitation currents of the two groups are equal in size but opposite in direction, thereby generating an eight-pole magnetic field. The four-pole magnetic field excitation coil of the outer layer has coils on adjacent two pole heads as 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 have the same excitation current size and direction of the two groups of four-pole magnetic field coils, 3, 4 pole heads and symmetrically arranged 7, 8 pole heads have the same excitation current size and direction of the two groups of coils, and 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 four-pole magnetic field.

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