Ultra-short beam homogenization transmission line system and method based on a four-pole composite magnet

Abstract

The application provides an ultra-short beam current homogenization transmission line system and method based on a four-octupole composite magnet, which comprises the four-octupole composite magnet and a system, a linear type and a bending type beam homogenization structure, and a two-stage iron for the beam homogenization transmission line; further comprises an ultra-short linear type beam homogenization transmission line, an ultra-short bending type beam homogenization transmission line, an ultra-short linear-bending composite type beam homogenization transmission line and an ultra-short symmetric bending type beam homogenization transmission line based on the homogenization structure and / or the two-stage iron; the method comprises a four-octupole composite iron-based excitation current debugging method and a linear type and a bending type beam debugging method; the application solves the problems that the place with the largest envelope on the transmission line is occupied and the eight-pole iron cannot fully play a role, solves the problem that the beam envelope at the position of the eight-pole iron is small and the field intensity requirement of the eight-stage magnet is high, and solves the problem that the length of the transmission line is too long, which leads to the increasing cost of the surrounding shielding civil engineering.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of accelerator transmission lines, and particularly relates to an ultra-short beam homogenization transmission line system and method based on a four-octupole composite magnet. BACKGROUND

[0002] The secondary particles generated by the post-targeting of the accelerator extracted beam are important radiation sources required by many nuclear technology research and applications. For example, in the nuclear technology applications such as neutron imaging and boron neutron capture therapy based on a high-intensity proton accelerator, the accelerator generates a high-energy high-intensity proton beam, which is post-targeted on a neutron target after being transmitted through a transmission line to generate high-flux neutrons.

[0003] The distribution of the accelerator extracted beam is generally approximately Gaussian distribution, which has the highest particle density at the center of the beam group, and at the same time, 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.

[0004] In order to solve the problem of uneven particle distribution, an octupole magnet is used in the beam transmission 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 transmission 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 prior art is usually occupied by a quadrupole magnetic field. As shown in FIG. 6, the transmission line of the prior art is arranged in the order of quadrupole 1, octupole 1, quadrupole 2, and octupole 2. Since the octupole magnet needs to be focused (the focusing function is to allow the beam to pass through the circular hole in the center of the octupole magnet without hitting the octupole magnet) before homogenization, in order to ensure focusing, the positions of the octupole 1 and the octupole 2 must be selected at the waist position of the X-direction envelope and the waist position of the Y-direction envelope. However, since the quadrupole 1 has a small envelope in the Y-direction at the waist position of the X-direction envelope, and the quadrupole 2 has a small envelope in the X-direction at the waist position of the Y-direction envelope, at the octupole 1, although the waist position of the octupole 1 in the X-direction is ensured, the envelope in the Y-direction is small, and at the octupole 2, although the waist position of the octupole 2 in the Y-direction is ensured, the envelope in the X-direction is small. In summary, according to the conventional method, after the particles pass through the quadrupole 1 and the quadrupole 2, the beam envelope has been significantly reduced, so the octupole 1 and the octupole 2 cannot fully play their roles.

[0006] The second difficulty of using octupole magnets to homogenize the Gaussian distribution of the beam is that the field strength K of the octupole magnet is very high because the beam envelope at the positions of the octupole magnet 1 and the octupole magnet 2 is small, and the excessively high magnetic field strength is difficult to achieve in engineering.

[0007] The third difficulty of using octupole magnets to homogenize the Gaussian distribution of the beam is that if the octupole magnet is used to achieve a better beam homogenization effect, the position and phase of the octupole magnet have strict requirements, and in order to meet these requirements, the length of the transmission line often needs to be tens of meters. If the beam line is dragged for tens of meters, it is equivalent to making the accelerator small, which has no meaning. The longer the beam line, the more expensive the civil engineering of the surrounding shielding. In short, the excessively long transmission line has the disadvantages of large occupied area and high cost, which greatly limits the use of the beam homogenization technology. SUMMARY

[0008] The present application aims at the problems existing in the prior art, and proposes an ultra-short beam homogenization transmission line system and method based on a four-octupole composite magnet. The first purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the place with the largest envelope is usually occupied by the quadrupole magnetic field, and the octupole magnet cannot fully play its role. The second purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the beam envelope at the positions of the octupole magnet 1 and the octupole magnet 2 is small, and the field strength of the octupole magnet is very high, and the excessively high magnetic field strength is difficult to achieve in engineering. The third purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the excessively long transmission line leads to more expensive civil engineering of the surrounding shielding, large occupied area and high cost.

[0009] The present application aims at the problems existing in the prior art, and proposes an ultra-short beam homogenization transmission line system and method based on a four-octupole composite magnet. The first purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the place with the largest envelope is usually occupied by the quadrupole magnetic field, and the octupole magnet cannot fully play its role. The second purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the beam envelope at the positions of the octupole magnet 1 and the octupole magnet 2 is small, and the field strength of the octupole magnet is very high, and the excessively high magnetic field strength is difficult to achieve in engineering. The third purpose is to solve the problem that when the prior art uses discrete quadrupole magnets and octupole magnets, the excessively long transmission line leads to more expensive civil engineering of the surrounding shielding, large occupied area and high cost.

[0010] An ultra-short beam homogenization transmission line system based on a four-octupole composite magnet, characterized in that the transmission line system comprises a four-octupole composite magnet, a four-octupole composite magnet system, an ultra-short straight-line type beam homogenization structure, an ultra-short bending type beam homogenization structure, and a two-stage iron for an ultra-short symmetric bending type beam homogenization transmission line.

[0011] Further comprising an ultra-short straight-line type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system, and the ultra-short straight-line type beam homogenization structure.

[0012] Further comprising an ultra-short bending type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system, and the ultra-short bending type beam homogenization structure.

[0013] Also comprising a super-short linear-bend compound beam homogenization transmission line based on the quadrupole-octupole compound magnet, the quadrupole-octupole compound magnet system, the super-short linear beam homogenization structure, and the super-short bend-type beam homogenization structure;

[0014] Also comprising a super-short symmetric bend-type beam homogenization transmission line based on the quadrupole-octupole compound magnet, the quadrupole-octupole compound magnet system, the super-short bend-type beam homogenization structure, and the secondary iron for the super-short symmetric bend-type beam homogenization transmission line;

[0015] The quadrupole-octupole compound magnet has a total of eight pole heads, and each pole head is provided with inner and outer two layers of current coils in the radial direction close to the major radius. The inner layer coil is an octupole magnetic field excitation coil, and the outer layer coil is a quadrupole magnetic field excitation coil. The quadrupole-octupole compound magnet is arranged on the super-short beam homogenization transmission line, and is used to generate a large envelope in the Y direction together with the quadruple iron in front of it at the position of the quadrupole-octupole compound magnet 1, and to generate a large envelope in the X direction together with the quadruple iron of the quadrupole-octupole compound magnet 1 in front of it at the position of the quadrupole-octupole compound magnet 2, thereby homogenizing the Gaussian distributed beam, and installing the quadrupole-octupole compound magnet on the beam transmission line can reduce the number of transmission elements and shorten the length of the transmission line.

[0016] The quadrupole-octupole compound magnet system comprises a compound magnet current control device, a compound magnet main power supply, and a quadrupole / octupole compound iron. The compound magnet current control device is used to control the quadrupole field coil current output and the octupole field coil current output of the quadrupole / octupole compound iron of the compound magnet main power supply. The quadrupole / octupole compound iron is used to simultaneously generate a dominant quadrupole magnetic field and an octupole magnetic field, so that the functions of the quadruple iron and the octuple iron can be realized simultaneously by installing only one transmission element.

[0017] The super-short linear beam homogenization structure uses two quadrupole-octupole compound magnets on the transmission line, which simultaneously generate a quadrupole magnetic field and an octupole magnetic field, respectively, so that the functions of the quadruple iron and the octuple iron can be realized simultaneously by installing only one transmission element.

[0018] The super-short bend-type beam homogenization structure realizes a bend-type beam homogenization substructure and a symmetric bend-type beam homogenization substructure by using a secondary iron and multiple quadrupole-octupole compound irons on the transmission line. The bend-type beam homogenization substructure is used to realize a bend-type beam homogenization transmission line. The symmetric bend-type beam homogenization substructure is used to realize a super-short symmetric bend-type beam homogenization transmission line.

[0019] The secondary electrode used for the ultra-short symmetrical bending beam homogenization transmission line is a common electrode with symmetrical edge angles at the exit edge. Specifically, its beam inlet edge is a straight line, and its beam outlet edge is a pair of symmetrical 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 the center of the beam bending trajectory and the beam at the electrode outlet forms the electrode outlet edge angle. By optimizing the design of the electrode edge angle, utilizing the focusing effect of the electrode edge field, and cooperating with the envelopes of the four-eight-stage composite electrodes on both sides of the electrode in the Y and X directions, an ideal phase shift that meets the homogenization requirements can be obtained.

[0020] The ultrashort linear beam homogenization transmission line is a linear beam homogenization transmission line containing two quadrupole-octupole composite irons. The linear beam homogenization transmission line is provided with the following components along the beam direction: accelerator outlet, beam matching mechanism, quadrupole-octupole composite iron 1, quadrupole-octupole composite iron 2, beam homogenization effect observation mechanism, and terminal.

[0021] The ultra-short bend transition beam homogenization transmission line comprises two 4 / 8 grade composite iron pieces and one 2 grade iron piece. The ultra-short bend transition beam homogenization transmission line can be either Ultra-short bend transition beam homogenization transmission line A or Ultra-short bend transition beam homogenization transmission line B, both arranged along the beam direction. Ultra-short bend transition beam homogenization transmission line A, along the beam exit direction, sequentially includes: an accelerator outlet, a beam matching mechanism, 4 / 8 grade composite iron 1, a 2 grade iron piece, 4 / 8 grade composite iron 2, a beam matching and homogenization effect observation mechanism 1, and a terminal 1. Ultra-short bend transition beam homogenization transmission line B, along the beam exit direction, sequentially includes: an accelerator outlet, a beam matching mechanism, 4 / 8 grade composite iron 1, a 2 grade iron piece, 4 / 8 grade composite iron 3, a beam matching and homogenization effect observation mechanism 2, and a terminal 2.

[0022] The aforementioned ultrashort symmetrical bend beam homogenization transmission line is a symmetrical bend beam homogenization transmission line comprising two 48-level composite irons and one shared 2-level iron; the symmetrical bend beam homogenization transmission line comprising two 48-level composite irons and one shared 2-level iron consists of one shared beamline and two branch beamlines.

[0023] The aforementioned ultra-short straight-line-bending composite beam homogenization transmission line consists of a straight beam homogenization transmission line containing two 48-level composite iron pieces and a bending beam homogenization transmission line containing two 48-level composite iron pieces and one 2-level iron piece; the straight beam homogenization transmission line and the bending beam homogenization transmission line are composed of a common transmission line and two branch transmission lines.

[0024] The ultra-short bend-type beam homogenization structure, ultra-short bend-type beam homogenization transmission line, ultra-short symmetrical bend-type beam homogenization transmission line, and ultra-short straight-line bend-type composite beam homogenization transmission line utilize the combined focusing effect of the four-eight-pole composite iron 1 and the dipolar iron to generate a beam waist in the Y direction near the four-eight-pole composite iron 2 or four-eight-pole composite iron 3; and utilize the quadrupole field superposition of the dipolar iron and the four-eight-pole composite iron 2 or the dipolar iron and the four-eight-pole composite iron 3 to generate the envelope size in the X direction on the target, so that the envelope sizes in the X and Y directions are consistent.

[0025] The ultrashort linear beam homogenization structure, ultrashort curved beam homogenization structure, an ultrashort linear beam homogenization transmission line, an ultrashort curved beam homogenization transmission line, an ultrashort linear-curved composite beam homogenization transmission line, and an ultrashort symmetrical curved beam homogenization transmission line all exhibit the following characteristics: At the first quadruple-octagonal composite magnet, the beam envelope function in the Y or X direction reaches a large value; at the second quadruple-octagonal composite magnet, the beam envelope function in the X or Y direction reaches a large value; the phase shift of the particle between the two quadruple-octagonal composite magnets and the target... They are respectively 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.

[0026] Furthermore, this ultra-short bendable beam homogenization structure is provided with, sequentially along the beam direction, a quadrupole-octupole composite iron 1, a secondary iron, a quadrupole-octupole composite iron 2, and / or a quadrupole-octupole composite iron 3; the secondary iron is used to change the beam direction of the beam line from a straight line to a bend; the quadrupole-octupole composite iron 1, 2, and / or 3 are used to simultaneously generate quadrupole and octupole magnetic fields, respectively, so that only one transmission element is needed to simultaneously achieve the functions of quadrupole and octupole irons; this bendable beam homogenization structure... The homogenization substructure includes a 4 / 8 composite iron layer 1 upstream of the secondary iron layer and either a 4 / 8 composite iron layer 2 or 4 / 8 composite iron layer 3 downstream of the secondary iron layer. This symmetrical bend-type beam homogenization substructure comprises a symmetrical first bend-type beam homogenization structure and a symmetrical second bend-type beam homogenization structure. The symmetrical first bend-type beam homogenization structure has a 4 / 8 composite iron layer 1 upstream of the secondary iron layer and a 4 / 8 composite iron layer 2 downstream of the secondary iron layer. The symmetrical second bend-type beam homogenization structure… A 4 / 8 composite iron 1 is installed upstream of the secondary iron, and a 4 / 8 composite iron 3 is installed downstream of the secondary iron. The symmetrical first bending beam homogenization structure and the symmetrical second bending beam homogenization structure operate in a time-division manner. The diodes on the symmetrical bending beam homogenization transmission line based on the symmetrical bending beam homogenization substructure are shared diodes on the ultra-short symmetrical bending beam homogenization transmission line. The shared diodes are diodes with symmetrical upper and lower edge angles at the exit side. Specifically, the beam inlet side is a straight line, and the beam outlet side is a pair of symmetrical upper and lower oblique lines. The inclination direction of the symmetrical upper and lower oblique lines is the direction in which the beam bends at the exit side. The line connecting the center of the beam bending track to the beam at the exit of the diode forms the exit edge angle of the diode. By changing the size of the exit edge angle of the diode, the edge field focusing effect of the diode is adjusted, and in conjunction with the envelopes of the 4 / 8 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.

[0027] This ultra-short, straight-line, curved-type composite beam homogenization transmission line has the following components along the beam direction: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a 4 / 8 composite iron 2. The 4 / 8 composite iron 2, when applied to the curved-type branch transmission line, only has a quadrupole field and not an 8th-order field. The two branch transmission lines are a straight-line branch transmission line and a curved-type branch transmission line. The straight-line branch transmission line has a beam homogenization effect observation mechanism and a terminal. The curved-type branch transmission line has a secondary iron, a 4 / 8 composite magnet 3, a beam matching and homogenization effect observation mechanism, and a terminal. The transmission line and the straight branch transmission line form a composite straight beam homogenization transmission line; the common transmission line and the curved branch transmission line form a composite curved beam homogenization transmission line; the composite straight beam homogenization transmission line and the composite curved beam homogenization transmission line operate in a time-division manner; the four-eight-pole composite iron 1 and four-eight-pole composite iron 2 of the composite straight beam homogenization transmission line and the four-eight-pole composite iron 1 and four-eight-pole composite iron 3 of the composite curved beam homogenization transmission line simultaneously generate quadrupole magnetic fields and octupole magnetic fields, so that the functions of quadrupole iron and octupole iron can be realized simultaneously by installing only one transmission element;

[0028] The common beamline of this ultra-short symmetrical bend-type beam homogenization transmission line is provided along the beam direction as follows: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a 2-stage iron; the two branch beamlines are a first branch beamline and a second branch beamline; the first branch beamline is provided with a 4 / 8 composite iron 2, a beam matching and homogenization effect observation mechanism 1, and a terminal 1; the second branch beamline is provided with a 4 / 8 composite iron 3, a beam matching and homogenization effect observation mechanism 2, and a terminal 2; the common beamline and the first branch beamline form a first bend-type beam homogenization transmission line; the common beamline and the second branch beamline form 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; the first bend-type beam homogenization transmission line and the second bend-type beam homogenization transmission line... The four-eighths-pole composite iron 1, four-eighths-pole composite iron 2, and four-eighths-pole composite iron 3 of the homogenization transmission line simultaneously generate quadrupole magnetic fields and octupole magnetic fields, respectively, so that only one transmission element is needed to achieve the functions of both quadrupole and octupole irons. The shared secondary iron is a dipole iron that satisfies the homogenization of the beam under symmetrical bending. The dipole iron has a vertically symmetrical straight edge at the entrance of the symmetrically bent beam and a vertically symmetrical inclined edge at the exit of the symmetrically bent beam. The inclination direction of the symmetrical inclined edge is the direction of beam bending. The vertically symmetrical inclined line and the line connecting the center of the beam bending track to the beam at the exit of the dipole iron form the dipole iron exit edge angle. By changing the size of the dipole iron exit edge angle, the edge field focusing effect of the dipole iron is adjusted, and in conjunction with the envelopes of the four-eighths-pole composite irons on both sides of the dipole iron in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

[0029] Furthermore, in the inner layer of the octagonal magnetic field excitation coil of the four-octagonal composite magnet, the current directions of adjacent poles are opposite, 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. The outer layer of the four-pole magnetic field excitation coil has coils on adjacent poles as a group, divided into four groups, namely poles 1 and 2, poles 3 and 4, poles 5 and 6, and poles 7 and 8. Among them, the excitation current magnitude and direction of the four-pole magnetic field coils of poles 1 and 2 and symmetrically arranged poles 5 and 6 are the same, the excitation current magnitude and direction of the two groups of coils of poles 3 and 4 and symmetrically arranged poles 7 and 8 are the same, the current direction of the coils of poles 1 and 2 and poles 3 and 4 is opposite, and the current direction of the coils of poles 5 and 6 and poles 7 and 8 is opposite, thereby generating a four-pole magnetic field.

[0030] Furthermore, the composite magnet current control device of the four-pole / octole composite magnet system 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 / octole field gradient current curves, and a module for outputting four / octole coil current.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 fourth-order 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 eighth-order field gradient.

[0035] 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 fourth-order field gradient and the current curve that satisfies the eighth-order field gradient, and uses the intersection point as the solution of the composite iron excitation current.

[0036] 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.

[0037] Furthermore, the phase shift of particles in the ultrashort straight beam homogenization structure, ultrashort curved beam homogenization structure, an ultrashort straight beam homogenization transmission line, an ultrashort curved beam homogenization transmission line, an ultrashort straight-curved composite beam homogenization transmission line, and an ultrashort symmetrical curved beam homogenization transmission line between the target and two quadrupole composite magnets. The integer multiples of 180 degrees (0, 1, 2, 3…) refer to integer 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.

[0038] Furthermore, the transmission matrix between the two octagonal magnetic fields of the ultrashort straight beam homogenization structure, ultrashort curved beam homogenization structure, ultrashort straight beam homogenization transmission line, ultrashort curved beam homogenization transmission line, ultrashort straight-curved composite beam homogenization transmission line, and ultrashort symmetrical curved beam homogenization transmission line is close to a unit matrix. That is, the phase shift between the two quadrupole 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.

[0039] Furthermore, the expressions for the magnet strength k at the first four-octet composite magnet and the second four-octet composite magnet of the ultrashort straight beam homogenization structure, the ultrashort curved beam homogenization structure, the ultrashort straight beam homogenization transmission line, the ultrashort curved beam homogenization transmission line, the ultrashort straight-curved composite beam homogenization transmission line, and the ultrashort symmetrical curved beam homogenization transmission line are as follows:

[0040]

[0041] Let: the starting point of the transport 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.

[0042] Furthermore, when the ultrashort bending beam homogenization structure uses a bending beam homogenization substructure or a symmetrical first bending beam homogenization structure, the beam envelope function in the Y or X direction reaches a large value at the 4 / 8 composite iron 1, and the beam envelope function in the X or Y direction reaches a large value at the 4 / 8 composite iron 2; the phase shift of the particle between the 4 / 8 composite iron 1 and 4 / 8 composite iron 2 and the target... These values ​​are approximately integer multiples of 180 degrees (0, 1, 2, 3…); the transmission matrix between the two octagonal magnetic fields is approximately an identity matrix; when using a bending-type beam homogenization substructure or a symmetrical second bending-type beam homogenization structure, the beam envelope function in the Y or X direction reaches a large value at the 4 / 8-pole composite iron 1, and the beam envelope function in the X or Y direction reaches a large value at the 4 / 8-pole composite iron 3; the phase shift of the particle between the 4 / 8-pole composite iron 1 and 4 / 8-pole composite iron 3 and the target. They are respectively 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.

[0043] Furthermore, the secondary iron is a common diode on an ultra-short symmetrical bend-type beam homogenization transmission line, which consists of a common transmission line and two branch transmission lines. The common transmission line, along the beam direction, is sequentially equipped with: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a secondary iron. The common transmission line, the 4 / 8 composite iron 2 of the first branch transmission line, the beam matching and homogenization effect observation mechanism 1, and the terminal 1 constitute the first bend-type beam homogenization transmission line. The common transmission line and the 4 / 8 composite iron 3 of the second branch transmission line, the beam matching and homogenization effect observation mechanism 2, and the terminal 2 constitute the 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.

[0044] The aforementioned ultrashort symmetrical bend-type beam homogenization transmission line comprises a common transmission line and two branch transmission lines. The common transmission line, along the beam direction, sequentially includes: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a secondary iron 2. The common transmission line, along with the 4 / 8 composite iron 2, beam matching and homogenization effect observation mechanism 1, and terminal 1 of the first branch transmission line, constitutes the first bend-type beam homogenization transmission line. The common transmission line, along with the 4 / 8 composite iron 3, beam matching and homogenization effect observation mechanism 2, and terminal 2 of the second branch transmission line, constitute the second bend-type beam homogenization transmission line. The first bend-type beam homogenization transmission line and the second bend-type... The beam homogenization transmission line operates in a time-division multiplexing manner. Its characteristic is that the shared diode has symmetrical edge angles at its exit edge. Specifically, its beam inlet edge is a straight line, and its beam outlet edge is a pair of symmetrical oblique lines. The inclination direction of these symmetrical oblique lines corresponds to 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 outlet at the diode 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. Combined with the envelopes in the Y and X directions of the four-eighths-level composite iron on both sides of the diode, an ideal phase shift meeting homogenization requirements is obtained.

[0045] Furthermore, the step of optimizing the edge angle of the diode to obtain an ideal phase shift that meets the homogenization requirements is as follows: by adjusting the size of the edge angle of the diode outlet, the phase difference in the Y direction from the first four-eight-pole composite iron to the target point is close to 180 degrees, the phase difference in the X direction from the second four-eight-pole composite iron to the target point is close to 0 degrees, the phase difference in the X direction between the two four-eight-pole composite irons is less than 30 degrees, and the phase difference in the Y direction between the two four-eight-pole composite irons is less than 30 degrees.

[0046] The angle formed by the center of the beam deflection track and the lines connecting the beam at the inlet and outlet of the diode is the beam deflection angle. When the beam deflection angle is constant, the larger the edge angle of the diode outlet, the stronger the focusing in the Y direction and the weaker the focusing in the X direction. When the beam deflection angle is constant, the smaller the edge angle of the diode outlet, the stronger the focusing in the X direction and the weaker the focusing in the Y direction.

[0047] The method involves adjusting the edge field focusing effect of the diode by changing the size of the diode exit edge angle, and coordinating with the envelopes of the four-eighths-level composite iron on both sides of the diode in the Y and X directions to obtain an ideal phase shift that meets the homogenization requirements. Specifically: when the homogenization effect requires enhanced focusing in the Y direction and weakened focusing in the X direction to obtain an ideal phase shift that meets the homogenization requirements, the diode exit edge angle is increased when the beam bending angle is constant; when the homogenization effect requires weakened focusing in the Y direction and enhanced focusing in the X direction to obtain an ideal phase shift that meets the homogenization requirements, the diode exit edge angle is decreased when the beam bending angle is constant.

[0048] The adjustable range of the electrode outlet edge angle is ≥0 degrees and <90 degrees;

[0049] The adjustable range of the electrode outlet edge angle is preferably 20 degrees to 60 degrees;

[0050] For the first curved beam homogenization transmission line, the diode with symmetrical upper and lower edge angles at the exit edge is arranged between the 48-level composite iron 1 and the 48-level composite iron 2. The conventional diode is replaced by the diode with symmetrical upper and lower edge angles at the exit edge of the ultra-short transmission line to achieve phase shift matching and beam focusing in the case of ultra-short transmission line.

[0051] For the second curved beam homogenization transmission line, the diode with symmetrical upper and lower edge angles at the exit edge is arranged between the 48-level composite iron 1 and the 48-level composite iron 3. The diode with symmetrical upper and lower edge angles at the exit edge of the ultra-short transmission line is used to replace the conventional diode to achieve phase shift matching and beam focusing in the case of ultra-short transmission line.

[0052] A method for adjusting the excitation current of a four / eight-pole composite iron, characterized by the following steps:

[0053] Step 1: Establish a two-dimensional data comparison table for coil current of four-pole iron and eight-pole iron; this two-dimensional data comparison table for coil current is based on the two-dimensional data comparison table for coil current of four / eight-pole composite iron.

[0054] Step 2: Experimental measurement 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.

[0055] Step 3: Use cubic spline functions to perform two-dimensional interpolation on the three-dimensional surface sample database of the quadrupole magnetic field gradient and the octupole magnetic field gradient to refine the grid point density.

[0056] Step 4: Select a quadrupole magnetic field gradient plane. This plane intersects with the surface of the quadrupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the four-level field gradient. Select an octupole magnetic field gradient plane. This plane intersects with the surface of the octupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the eight-level field gradient.

[0057] Step 5: Obtain the current curves that satisfy the fourth-order field gradient and the current curves that satisfy the eighth-order field gradient in the two-dimensional data grid plane of the coil current, and finally find the intersection point of the two current curves.

[0058] Step 6: Use the intersection point as the solution for the excitation current of the composite iron.

[0059] A method for commissioning a linear beam homogenization transmission line is disclosed. This method is based on a four / eight-pole composite iron, a four / eight-pole composite iron system, an excitation current adjustment method based on the four / eight-pole composite iron, and an ultra-short linear beam homogenization transmission line. The method is characterized by the following steps:

[0060] Step 1: Set the quadrupole field and octupole field currents of the quadrupole iron and the two quadrupole-octupole composite irons to zero;

[0061] Step 2: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current in front of the quadrupole-octupole composite iron 1 so that the beam in the X direction near the quadrupole-octupole composite iron 1 forms a waist.

[0062] Step 3: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current of the quadrupole-octupole composite iron 1 in front of the quadrupole-octupole composite iron 2 so that the beam in the Y direction near the quadrupole-octupole composite iron 2 forms a waist, and retain the quadrupole field gradient of the quadrupole-octupole composite iron 1 at this time.

[0063] Step 4: Adjust the quadrupole current of the quadrupole-octapole composite iron 2 so that the X-direction envelope of the beam on the fluorescent target is consistent with the Y-direction envelope, to obtain a circular beam, and retain the quadrupole field gradient of the quadrupole-octapole composite iron 2 at this time.

[0064] Step 5: Adjust the octagonal field of the four-octagonal composite iron 1 to adjust the beam homogenization effect in the Y direction. Based on the four-octagonal field gradient of the four-octagonal composite iron 1 recorded in Step 3 and the current octagonal field gradient of the four-octagonal composite iron 1, calculate the intersection current that simultaneously satisfies the four-octagonal field gradient and the octagonal field gradient of the four-octagonal composite iron 1, and retain the octagonal field gradient of the four-octagonal composite iron 1 at this time.

[0065] Step 6: If the beam homogenization is not significantly improved when adjusting the octet field current of the four-octet composite iron 1, the four-octet field gradient of the four-octet composite iron 1 needs to be modified for phase shift matching so that the phase shift of the four-octet composite iron 1 to the target in the Y direction is close to 180°. That is, based on the adjusted four-octet field gradient of the four-octet composite iron 1 and the octet field gradient retained in step 5, the intersection current that simultaneously satisfies the four-octet field gradient and the octet field gradient of the four-octet composite iron 1 is calculated.

[0066] Step 7: Adjust the octet field of the four-octet composite iron 2 to adjust the beam homogenization effect in the X direction. Based on the four-octet field gradient of the four-octet composite iron 2 recorded in Step 4 and the current octet field gradient of the four-octet composite iron 2, calculate the intersection current that simultaneously satisfies the four-octet field gradient and the octet field gradient of the four-octet composite iron 2, and retain the octet field gradient of the four-octet composite iron 2 at this time.

[0067] Step 8: If the uniformity of the beam current does not change significantly when adjusting the octet field current of the four-octet composite iron 2, it is necessary to increase the beam current envelope in the X direction at the four-octet composite iron 2.

[0068] A method for debugging a curved beam homogenization transmission line, the method being based on a four / octet composite iron, a four / octet composite iron system, an excitation current adjustment method based on the four / octet composite iron, and an ultra-short straight beam homogenization transmission line; characterized by including the following steps:

[0069] Step 1: Set the quadrupole field and octupole field currents of the quadrupole iron and the two quadrupole-octupole composite irons to zero;

[0070] Step 2: Adjust the diode current so that the center of the beam spot is roughly aligned with the center of the fluorescent target;

[0071] Step 3: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current in front of the quadrupole-octupole composite iron 1 so that the beam in the X direction near the quadrupole-octupole composite iron 1 forms a waist.

[0072] Step 4: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole field current of the quadrupole-octupole composite iron 1 in front of the diode. Under the combined action of the edge field of the diode and the quadrupole field of the quadrupole-octupole composite iron 1, the beam in the Y direction near the quadrupole-octupole composite iron 2 is made to form a waist, and the quadrupole field gradient of the quadrupole-octupole composite iron 1 is preserved at this time.

[0073] Step 5: Adjust the quadrupole current of the quadrupole-octupole composite iron 2 so that the X-direction envelope of the beam on the fluorescent target is consistent with the Y-direction envelope to obtain a circular beam. Adjust the diode current again to align the beam spot center with the target center and retain the quadrupole field gradient of the quadrupole-octupole composite iron 2 at this time.

[0074] Step 6: Adjust the octagonal field of the four-octagonal composite iron 1 to adjust the beam homogenization effect in the Y direction. Based on the four-octagonal field gradient of the four-octagonal composite iron 1 recorded in Step 4 and the current octagonal field gradient of the four-octagonal composite iron 1, calculate the intersection current that simultaneously satisfies the four-octagonal field gradient and the octagonal field gradient of the four-octagonal composite iron 1, and retain the octagonal field gradient of the four-octagonal composite iron 1 at this time.

[0075] Step 7: If the beam homogenization is not significantly changed when adjusting the octet field current of the four-octet composite iron 1, it is necessary to modify the four-electrode field gradient of the four-octet composite iron 1 for phase shift matching, so that the phase shift of the four-octet composite iron 1 to the target in the Y direction is close to 180°. That is, based on the adjusted four-electrode field gradient of the four-octet composite iron 1 and the octet field gradient retained in step 6, the intersection current that simultaneously satisfies the four-electrode field gradient and the octet field gradient of the four-octet composite iron 1 is calculated.

[0076] Step 8: Adjust the octagonal field of the four-octagonal composite iron 2 to adjust the beam homogenization effect in the X direction. Based on the four-octagonal field gradient of the four-octagonal composite iron 2 recorded in Step 5 and the current octagonal field gradient of the four-octagonal composite iron 2, calculate the intersection current that simultaneously satisfies the four-octagonal field gradient and the octagonal field gradient of the four-octagonal composite iron 2, and retain the octagonal field gradient of the four-octagonal composite iron 2 at this time.

[0077] Step 9: If the uniformity of the beam current does not change significantly when adjusting the octet field current of the four-octet composite iron 2, it is necessary to increase the beam current envelope in the X direction at the four-octet composite iron 2.

[0078] Advantages and effects of the present invention

[0079] 1. This invention comprises a linear beam homogenization transmission line consisting of two quadrupole-octupole composite irons. It employs a method of generating a large envelope using both quadrupole-octupole composite irons and quadrupole irons, which solves the problem in existing technologies where, when using discrete quadrupole irons and octupoles, the largest area of ​​the envelope is usually occupied by the quadrupole magnetic field, thus failing to fully utilize the function of the octupole iron.

[0080] 2. This invention includes a linear beam homogenization transmission line consisting of two quadrupole-octupole composite irons. Since the quadrupole-octupole composite irons are located at the large envelope, the requirement for the magnetic field strength K value of the quadrupole-octupole composite irons is reduced. This solves the problem that when using discrete quadrupole irons and octupoles in the prior art, the beam envelope at the locations 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.

[0081] 3. This invention comprises a linear beam homogenization transmission line consisting of two quadrupole and octupole composite irons. Within the aperture of the quadrupole and octupole composite irons, quadrupole and octupole magnetic fields are generated simultaneously, achieving both focusing and homogenization of the beam envelope. Installing the composite irons on the beam transmission line reduces the number of transmission elements and shortens the transmission line length. This solves 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.

[0082] 4. This invention comprises a linear beam homogenization transmission line consisting of two quadrature-octet composite magnets, 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...). This makes the required magnetic field strengths k1 and k2 at the first and second four-eight-pole composite magnets smaller. While ensuring the homogenization effect, it is beneficial to reduce the difficulty and cost of magnet manufacturing.

[0083] 5. The present invention comprises a linear beam homogenization transmission line of two octagonal composite irons, which limits the transmission matrix between the two octagonal magnetic fields to be close to the identity matrix. That is, the phase shift between the two octagonal composite magnets is controlled within 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

[0084] Figure 1 This is a schematic diagram of the ultrashort beam homogenization transmission line system based on a four-octet composite magnet according to the present invention.

[0085] Figure 2a This is a schematic diagram of the four-eight-pole composite magnet current control device of the present invention;

[0086] Figure 2b This invention provides a novel four / octet composite iron model.

[0087] Figure 2c The arrangement and current direction of the four-eight-pole composite magnet coils of this invention;

[0088] Figure 2d This is a schematic diagram showing the current values ​​of the two sets of coils during magnetic field measurement in this invention;

[0089] Figure 2e This is a schematic diagram illustrating the quadrupole magnetic field gradient under different currents in the experimental measurement of this invention.

[0090] Figure 2f 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.

[0091] Figure 2g 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;

[0092] Figure 2h This is a schematic diagram of the current curve corresponding to the four / octet field selected in this invention;

[0093] Figure 2i This is a schematic diagram illustrating the solution for the composite iron excitation current of the present invention;

[0094] Figure 3 This is a schematic diagram of the ultrashort linear beam homogenization structure of the present invention;

[0095] Figure 4 This is a schematic diagram showing the phase difference between the two octet composite iron pieces and the target point (target) and the phase difference between the two octet composite iron pieces in this invention;

[0096] Figure 5a This is a schematic diagram of the ultra-short bending beam homogenization structure of the present invention;

[0097] Figure 5b This is a schematic diagram of the ultra-short single-bend transition beam homogenization substructure A of the present invention. Figure 1 ;

[0098] Figure 5c This is a schematic diagram of the ultra-short single-bend transition beam homogenization substructure B of the present invention;

[0099] Figure 5d This is a schematic diagram of the ultra-short symmetrical bending beam homogenization substructure of the present invention;

[0100] Figure 6a This is a schematic diagram of the linear beam homogenization transmission line of the present invention;

[0101] Figure 6b This is a schematic diagram of the maximum envelope positions of the four-octet composite iron 1 and 2 in the linear beam homogenization transmission line of the present invention.

[0102] Figure 6c This is a schematic diagram of the linear beam homogenization transmission line-beam matching mechanism of the present invention;

[0103] Figure 6d This is a schematic diagram of the linear beam homogenization transmission line and beam homogenization effect observation mechanism of the present invention.

[0104] Figure 6e This is a schematic diagram comparing the particle distribution state before and after the transmission line homogenization in this invention.

[0105] Figure 7a This is a schematic diagram of the curved beam homogenization transmission line of the present invention;

[0106] Figure 7bThis is a schematic diagram showing the maximum envelope positions of the four-octet composite iron 1 and 2 of the curved beam homogenization transmission line of the present invention.

[0107] Figure 7c This is a schematic diagram of the beam current matching mechanism for the bending beam current homogenization transmission line of the present invention;

[0108] Figure 7d This is a schematic diagram of the beam current matching and homogenization effect observation mechanism 1 of the curved beam homogenization transmission line of the present invention.

[0109] Figure 7e This is a schematic diagram comparing the particle distribution state before and after homogenization of the curved beam homogenization transmission line of the present invention.

[0110] Figure 8a This is a schematic diagram of the symmetrical bending beam homogenization transmission line of the present invention.

[0111] Figure 8b This is a schematic diagram showing the maximum envelope positions of the four-octet composite iron 1 and 2 of the symmetrical bending beam homogenization transmission line of the present invention.

[0112] Figure 8c This is a schematic diagram of the beam matching mechanism for the symmetrical bending beam homogenization transmission line of the present invention.

[0113] Figure 8d This is a schematic diagram of the beam matching and homogenization effect observation mechanism 1 for the symmetrical bending beam homogenization of the present invention;

[0114] Figure 8e This is a schematic diagram of the beam matching and homogenization effect observation mechanism 2 for the symmetrical bending beam homogenization of the present invention;

[0115] Figure 8f This is a schematic diagram comparing the particle distribution state before and after homogenization of the symmetrical bending beam homogenization transmission line of the present invention.

[0116] Figure 9a This is a schematic diagram of the ultra-short straight-line bending composite beam homogenization transmission line of the present invention;

[0117] Figure 9b This is a schematic diagram showing the maximum envelope positions of the four-eight-pole composite iron 1 and 2 in the composite linear transmission line of the present invention.

[0118] Figure 9c This is a schematic diagram showing the maximum envelope positions of the four-eight-pole composite iron 1 and 3 in the composite bending transmission line of the present invention.

[0119] Figure 9d This is a schematic diagram of the ultra-short straight-line bending composite transmission line matching mechanism of the present invention;

[0120] Figure 9eThis is a schematic diagram of the observation mechanism for the homogenization effect of the composite bending beam homogenization transmission line of the present invention.

[0121] Figure 9f This is a schematic diagram of the observation mechanism for the homogenization effect of the composite linear beam homogenization transmission line of the present invention.

[0122] Figure 9g This is a comparison of the homogenization process before and after the homogenization of the composite bending beam homogenization transmission line of the present invention.

[0123] Figure 9h This is a comparison of the composite linear beam homogenization transmission line before and after homogenization in this invention.

[0124] Figure 10 This is a schematic diagram of the secondary iron of the ultra-short symmetrical bending beam homogenization transmission line of the present invention.

[0125] Figure 11 This is a flowchart of a linear beam homogenization debugging method based on a four-octet composite magnet according to the present invention.

[0126] Figure 12 This is a flowchart of a bending beam homogenization debugging method based on a four-octet composite magnet according to the present invention.

[0127] Figure 13 The beam envelope diagrams for existing technologies based on discrete components, such as quadrupole and octupole iron.

[0128] Figure 14 This is a diagram showing the positions of various components in an ultra-short linear beam homogenization transmission line according to the present invention.

[0129] Figure 15 This is a diagram showing the positions of various components in an ultra-short bend beam homogenization transmission line according to the present invention.

[0130] Figure 16 This is a diagram showing the positions of various components in an ultra-short symmetrical bending beam homogenization transmission line according to the present invention.

[0131] Figure 17 This is a diagram showing the positions of various components in an ultra-short straight-line bending composite beam homogenization transmission line of the present invention. Detailed Implementation

[0132] Innovation of this invention:

[0133] One of the innovations lies in the invention of a four-octet composite iron. (The text abruptly ends here, seemingly mid-sentence.) Figure 2a , 2b The octet composite iron shown in 2c replaces, for example, Figure 13 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 6b , 7bAs shown in Figures 8b and 9b: the quadrupole and octupole share the positions of the large envelopes in the Y and X directions. The reason they can share these positions 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 both 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 13 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.

[0134] 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 relationship 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 2a As shown, it includes: a two-dimensional sampling point module based on coil current; a three-dimensional surface sample library module for the initial magnetic field gradient based on experimental measurements; a three-dimensional surface sample library module for the refined magnetic field gradient based on interpolation algorithms; a current curve module for solving the corresponding field gradient based on the field gradient input; a current curve intersection point module based on the field gradient solution; and an output four-pole / octole coil current module. This four / octole composite iron excitation current design method is as follows:

[0135] Step 1, such as Figure 2d 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 2d As shown, the horizontal axis represents the current of the fourth-stage coil, and the vertical axis represents the current of the fourth-stage coil.

[0136] Step Two, as follows Figure 2e 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.

[0137] The above three-dimensional surface sample database Figure 2e As shown, the current of the four-stage coil is used as the X-axis coordinate, the current of the eight-stage coil is used as the Y-axis coordinate, and the magnetic field gradient is used as the Z-axis coordinate.

[0138] Step 3, as follows Figure 2f 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.

[0139] The effect of the above-mentioned encrypted grid point density is as follows: Figure 2f As shown, the grid density on the X, Y, and Z axes has increased.

[0140] Step 4, as follows Figure 2g 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 four-level field 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 eight-level field gradient.

[0141] Step 5, as follows Figure 2h As shown, the current curves satisfying the fourth-order field gradient and the eighth-order 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.

[0142] Step Six, as Figure 2i As shown, the intersection point is used as the solution for the excitation current of the composite iron.

[0143] The third innovation lies in the invention of an ultra-short straight beam homogenization structure and an ultra-short curved beam homogenization structure, as well as a secondary iron for an ultra-short symmetrical curved beam homogenization transmission line.

[0144] First, such as Figure 3 As shown, the ultra-short linear beam homogenization structure uses two quadrupole composite irons on the transmission line. 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. 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.

[0145] Second, such as Figure 5a As shown, the ultra-short bending beam homogenization structure employs two quadrupole-octupole composite iron pieces and a diode between them on the transmission line. The diode is used to bend the direction of the beam. The innovation lies in that, at the current intersection point of quadrupole-octupole composite iron 1, the quadrupole current of quadrupole-octupole composite iron 1 is appropriately reduced. The edge field focusing effect of the diode entrance behind quadrupole-octupole composite iron 1 and the quadrupole focusing effect of quadrupole-octupole composite iron 1 itself are superimposed to generate the waist in the Y direction at quadrupole-octupole composite iron 2. At the current intersection point of quadrupole-octupole composite iron 2, the quadrupole current of quadrupole-octupole composite iron 2 is appropriately reduced. The edge field focusing effect of the diode exit behind quadrupole-octupole composite iron 1 and the quadrupole focusing effect of quadrupole-octupole composite iron 2 itself are superimposed to generate the envelope size in the X direction on the target, making the envelope sizes in the X and Y directions consistent.

[0146] Third, such as Figure 10 As shown, the secondary electrode used for the ultra-short symmetrical bending beam homogenization transmission line is a common electrode on the ultra-short symmetrical bending beam homogenization transmission line. This common electrode 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 these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting the center of the beam bending trajectory and the beam at the electrode outlet forms the electrode outlet edge angle. By changing the size of the electrode outlet edge angle, the edge field focusing effect of the electrode is adjusted, and in conjunction with the envelopes of the four-eight-stage composite electrodes on both sides of the electrode in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

[0147] 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 6b , 7bAs shown in Figures 8b, 9b, and 9c, the homogenization effect of the ultra-short bend transition beam homogenization transmission line is significant. This is due to innovations in three aspects, all of which are indispensable and must support each other to achieve the ideal homogenization effect:

[0148] 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.

[0149] The second aspect: solving the problem of optimizing homogenization effect: specifically through phase shifting 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.

[0150] 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. This approximation to a unit matrix is ​​as follows: Figure 3 , 4As shown in Figure 5a, the phase difference between the first octagonal composite iron (point 1) and the second octagonal composite iron (point 2) is close to 0 degrees and less than 30 degrees. At this point, the required magnetic field strength of the octagonal magnet is relatively small, and the nonlinear effect caused by coupling is smaller, resulting in better homogenization. The difference between this invention and the prior art is that the transmission matrix between the two octagonal magnetic fields in the prior art 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 octagonal composite iron (point 1) and the second 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 4x8 composite iron (point 1) and the second 4x8 composite iron (point 2) is close to 0 degrees and less than 30 degrees, it can effectively shorten the transmission line length and meet the requirement of "avoiding nonlinear effects caused by coupling". A balance point is found between transmission line homogenization, avoiding nonlinear effects caused by coupling, and shortening the transmission line.

[0151] The fifth innovation lies in the invention of a linear beam homogenization transmission line debugging method based on octet composite iron. Figure 11 As shown, and a method for debugging a bending beam homogenization transmission line based on a four-octet composite iron, as follows: Figure 12 As shown; the former debugging method is used for ultra-short straight beam homogenization transmission lines, while the latter debugging method is used for ultra-short curved beam homogenization transmission lines.

[0152] 1) Challenges in debugging transmission lines based on quadrupole-octupole composite iron: Debugging transmission lines based on quadrupole-octupole composite iron presents two challenges compared to debugging based on a single type of quadrupole current or a single type of octupole current.

[0153] One challenge is that when the transmission line uses discrete components of four-pole iron and eight-pole iron, because they are far apart, adjusting the four-pole field current does not affect the eight-pole field current, and vice versa.

[0154] The four-pole / octole composite iron is a composite magnet sharing a single aperture. The multipole magnetic fields generated by the two sets of coils in the four-pole / octole composite iron are coupled. This coupling means that changing the current in either the four-pole or octole coil will simultaneously alter both the original four-pole and octole magnetic field gradients of the magnet. Therefore, the one-to-one adjustment strategy for the current-magnetic field gradient of a single type of magnet is no longer applicable.

[0155] Another challenge is that when using discrete components like quadrupole, dipolar, and octapole in the transmission line, the length is unrestricted, potentially reaching tens of meters. Although the dipole exhibits edge field focusing effects at its entrance and exit, these effects have little impact on the beam envelope due to the distance between the dipole and the preceding quadrupole. However, the ultra-short transmission line based on quadrupole composites is only about one-third the length of a conventional transmission line. The minimum distance between the dipole and the preceding quadrupole-octapole composite 1 and the following quadrupole-octapole composite 2 is 0.6 meters. Under such ultra-short distance conditions, the edge field focusing effect at the dipole entrance superimposed on the focusing of the preceding quadrupole-octapole composite 1, and the edge field focusing effect at the dipole exit superimposed on the focusing of the following quadrupole-octapole composite 2. This causes a change in the phase waist position of the quadrupole-octapole composite 1 in the X-direction, resulting in inconsistencies between the X-direction and Y-direction envelope dimensions on the target.

[0156] 2) Solution

[0157] First, in order to solve the problem of coupling relationship between the multipole magnetic fields generated by the two sets of coils of the four / eight-pole composite iron, the debugging method of this invention adopts the method of debugging near the intersection point of the four-pole iron current and the eight-pole iron current. First, find the intersection point, and then debug near it.

[0158] Secondly, to address the issue of the edge field focusing effect of the diode and the preceding and following octapoles affecting the beam envelope of the octapole composite iron when they are very close, this invention appropriately reduces the octapole current of octapole composite iron 1 at the current intersection point. The edge field focusing effect at the entrance of the diode behind octapole composite iron 1, combined with the octapole focusing effect of octapole composite iron 1 itself, is used to generate the waist in the Y direction at octapole composite iron 2. Similarly, at the current intersection point of octapole composite iron 2, the octapole current of octapole composite iron 2 is appropriately reduced. The edge field focusing effect at the exit of the diode behind octapole composite iron 1, combined with the octapole focusing effect of octapole composite iron 2 itself, is used to generate the envelope size in the X direction on the target, ensuring that the envelope sizes in the X and Y directions are consistent.

[0159] Based on the above principles, this invention designs an ultrashort beam homogenization transmission line system based on a four-octet composite magnet, such as... Figure 1 As shown, its features are: the transmission line system includes a four-eight-pole composite magnet, a four-eight-pole composite magnet system, an ultra-short straight beam homogenization structure, an ultra-short curved beam homogenization structure, and a secondary iron for ultra-short symmetrical curved beam homogenization transmission line.

[0160] like Figure 6aAs shown, it also includes an ultra-short straight beam homogenization transmission line based on the aforementioned four-eight-pole composite magnet, four-eight-pole composite magnet system, and ultra-short straight beam homogenization structure.

[0161] like Figure 7a As shown, it also includes an ultra-short bend transition beam homogenization transmission line based on the aforementioned four-eight-pole composite magnet, four-eight-pole composite magnet system, and ultra-short bend transition beam homogenization structure.

[0162] like Figure 8a As shown, it also includes an ultra-short symmetrical bend beam homogenization transmission line based on the aforementioned four-octet composite magnet, four-octet composite magnet system, ultra-short bend beam homogenization structure, and a secondary iron for ultra-short symmetrical bend beam homogenization transmission line.

[0163] like Figure 9a As shown, it also includes an ultra-short straight-curved composite beam homogenization transmission line based on the aforementioned four-eight-pole composite magnet, four-eight-pole composite magnet system, ultra-short straight beam homogenization structure, and ultra-short curved beam homogenization structure.

[0164] (1) The four-octet composite magnet, such as Figure 2b , 2c As shown, there are eight poles in total. Each pole has two layers of current coils along the radial direction near its large radius. The inner layer coil is an octagonal magnetic field excitation coil, and the outer layer coil is a quadrupole magnetic field excitation coil. This quadrupole-octagonal composite magnet is arranged on the ultra-short beam homogenization transmission line. It is used to generate a large envelope in the Y direction at the position of the quadrupole-octagonal composite magnet 1 together with the quadrupole iron in front of it, and to generate a large envelope in the X direction at the position of the quadrupole-octagonal composite magnet 2 together with the quadrupole iron in front of it of the quadrupole-octagonal composite magnet 1. This homogenizes the Gaussian distributed beam. Installing the quadrupole-octagonal composite magnet on the beam transmission line can reduce the number of transmission elements and shorten the length of the transmission line. The inner octagonal magnetic field excitation coil has a current direction between adjacent poles. Conversely, the octagonal field coil is divided into two groups: one with poles 1, 3, 5, and 7, and the other with poles 2, 4, 6, and 8. The excitation currents in both groups are equal in magnitude but opposite in direction, thus generating an octagonal magnetic field. The outer quadrature magnetic field excitation coil has four groups, with adjacent poles forming a group: poles 1 and 2, poles 3 and 4, poles 5 and 6, and poles 7 and 8. The excitation currents of poles 1 and 2, and symmetrically arranged poles 5 and 6, are in the same magnitude and direction. The excitation currents of poles 3 and 4, and symmetrically arranged poles 7 and 8, are in the same magnitude and direction. The currents of poles 1 and 2 are opposite to those of poles 3 and 4, and the currents of poles 5 and 6 are opposite to those of poles 7 and 8, thus generating a quadrature magnetic field. Figure 2bAs shown, the quadrupole composite magnet is arranged on the ultra-short beam homogenization transmission line to form a large envelope in the Y direction at the position of the quadrupole composite magnet 1 together with the quadrupole iron in front of it, and to form a large envelope in the X direction at the position of the quadrupole composite magnet 2 together with the quadrupole iron in front of the quadrupole composite magnet 1, thereby homogenizing the Gaussian distributed beam. Furthermore, by installing the quadrupole composite magnet on the beam transmission line, the number of transmission elements can be reduced and the length of the transmission line can be shortened.

[0165] (2) For example Figure 2a As shown, the four-pole / octole composite magnet system includes a composite magnet current control device, a composite magnet main power supply, and a four-pole / octole composite iron. The composite magnet current control device is used to control the current output of the four-pole field coil and the octole field coil of the four-pole / octole composite iron from the composite magnet main power supply. The four-pole / octole composite iron is used to simultaneously generate the dominant four-pole magnetic field and the octole magnetic field, so that the functions of the four-pole iron and the octole iron can be realized simultaneously by installing only one transmission element.

[0166] like Figure 2a As shown, the composite magnet current control device includes: a module for establishing two-dimensional sampling points for coil current, a module for experimentally 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.

[0167] like Figure 2d 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.

[0168] like Figure 2e 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.

[0169] like Figure 2f 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.

[0170] like Figure 2g , 2hAs shown, the module for solving the input field gradient corresponding to the field gradient 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 fourth-order 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 eighth-order field gradient.

[0171] like Figure 2i 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 fourth-order field gradient and the current curve that satisfies the eighth-order field gradient, and uses the intersection point as the solution of the composite iron excitation current.

[0172] 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.

[0173] (3) For example Figure 3 As shown, the ultra-short linear beam homogenization structure uses two quadrupole-octupole composite magnets on the transmission line. These two quadrupole-octupole composite magnets generate quadrupole magnetic fields and octupole magnetic fields simultaneously, so that only one transmission element is installed to achieve the functions of quadrupole iron and octupole iron at the same time.

[0174] (4) For example Figure 5a As shown, the ultra-short bendable beam homogenization structure achieves a bendable beam homogenization substructure and a symmetrical bendable beam homogenization substructure by using a secondary iron and multiple 4 / 8 composite iron on the transmission line; the bendable beam homogenization substructure is used to realize a bendable beam homogenization transmission line; the symmetrical bendable beam homogenization substructure is used to realize an ultra-short symmetrical bendable beam homogenization transmission line.

[0175] This ultra-short bending beam homogenization structure is arranged along the beam direction with: a quadrupole-octupole composite iron 1, a secondary iron, a quadrupole-octupole composite iron 2, and / or a quadrupole-octupole composite iron 3. The secondary iron is used to change the beam direction of the beam line from a straight line to a bending shape. The quadrupole-octupole composite iron 1, quadrupole-octupole composite iron 2, and / or quadrupole-octupole composite iron 3 are used to generate quadrupole magnetic fields and octupole magnetic fields simultaneously, so that only one transmission element is installed to achieve the functions of quadrupole iron and octupole iron at the same time.

[0176] The curved beam homogenization substructure has a 4 / 8 composite iron 1 upstream of the secondary iron and a 4 / 8 composite iron 2 or 4 / 8 composite iron 3 downstream of the secondary iron.

[0177] The symmetrical bend-type beam homogenization substructure includes a symmetrical first bend-type beam homogenization structure and a symmetrical second bend-type beam homogenization structure. The symmetrical first bend-type beam homogenization structure has a 4 / 8 composite iron 1 upstream of the secondary iron and a 4 / 8 composite iron 2 downstream of the secondary iron. The symmetrical second bend-type beam homogenization structure has a 4 / 8 composite iron 1 upstream of the secondary iron and a 4 / 8 composite iron 3 downstream of the secondary iron. The symmetrical first bend-type beam homogenization structure and the symmetrical second bend-type beam homogenization structure operate in a time-division multiplexing manner.

[0178] The diode on the symmetrical bending beam homogenization transmission line based on this symmetrical bending beam homogenization substructure is a shared diode on the ultra-short symmetrical bending beam homogenization transmission line. This shared 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 these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting the center of the beam bending trajectory and 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-eight-level composite iron 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.

[0179] When using a bend-type beam homogenization substructure or a symmetrical first bend-type beam homogenization structure, the beam envelope function in the Y or X direction reaches a large value at the 4 / 8 composite iron 1, and the beam envelope function in the X or Y direction reaches a large value at the 4 / 8 composite iron 2; the phase shift of the particle between the 4 / 8 composite iron 1 and 4 / 8 composite iron 2 and the target. These values ​​are approximately integer multiples of 180 degrees (0, 1, 2, 3…); the transmission matrix between the two octagonal magnetic fields is approximately an identity matrix; when using a bending-type beam homogenization substructure or a symmetrical second bending-type beam homogenization structure, the beam envelope function in the Y or X direction reaches a large value at the 4 / 8-pole composite iron 1, and the beam envelope function in the X or Y direction reaches a large value at the 4 / 8-pole composite iron 3; the phase shift of the particle between the 4 / 8-pole composite iron 1 and 4 / 8-pole composite iron 3 and the target. They are respectively 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;

[0180] Supplementary note 1

[0181] 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:

[0182]

[0183] 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...).

[0184] (5) For example Figure 8a , Figure 10 As shown, the secondary electrode used in the ultra-short symmetrical bend beam homogenization transmission line is a common electrode on the ultra-short symmetrical bend beam homogenization transmission line. This common electrode 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 these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting the center of the beam bending trajectory and the beam at the electrode outlet forms the electrode outlet edge angle. By optimizing the design of the electrode edge angle, utilizing the electrode edge field focusing effect, and cooperating with the envelopes of the four-eight-stage composite electrodes on both sides of the electrode in the Y and X directions, an ideal phase shift that meets the homogenization requirements can be obtained.

[0185] The process of optimizing the edge angle of the diode to obtain an ideal phase shift that meets the homogenization requirements involves adjusting the size of the diode outlet edge angle so that the phase difference in the Y direction from the first octet composite iron to the target point is close to 180 degrees, the phase difference in the X direction from the second octet composite iron to the target point is close to 0 degrees, the phase difference in the X direction between the two octet composite irons is less than 30 degrees, and the phase difference in the Y direction between the two octet composite irons is less than 30 degrees.

[0186] The angle formed by the center of the beam deflection track and the lines connecting the beam at the inlet and outlet of the diode is the beam deflection angle. When the beam deflection angle is constant, the larger the edge angle of the diode outlet, the stronger the focusing in the Y direction and the weaker the focusing in the X direction. When the beam deflection angle is constant, the smaller the edge angle of the diode outlet, the stronger the focusing in the X direction and the weaker the focusing in the Y direction.

[0187] The method involves adjusting the edge field focusing effect of the diode by changing the size of the diode exit edge angle, and coordinating with the envelopes of the four-eighths-level composite iron on both sides of the diode in the Y and X directions to obtain an ideal phase shift that meets the homogenization requirements. Specifically: when the homogenization effect requires enhanced focusing in the Y direction and weakened focusing in the X direction to obtain an ideal phase shift that meets the homogenization requirements, the diode exit edge angle is increased when the beam bending angle is constant; when the homogenization effect requires weakened focusing in the Y direction and enhanced focusing in the X direction to obtain an ideal phase shift that meets the homogenization requirements, the diode exit edge angle is decreased when the beam bending angle is constant.

[0188] The adjustable range of the electrode outlet edge angle is ≥0 degrees and <90 degrees;

[0189] The adjustable range of the electrode outlet edge angle is preferably 20 degrees to 60 degrees;

[0190] For the first curved beam homogenization transmission line, the diode with symmetrical upper and lower edge angles at the exit edge is arranged between the 48-level composite iron 1 and the 48-level composite iron 2. The conventional diode is replaced by the diode with symmetrical upper and lower edge angles at the exit edge of the ultra-short transmission line to achieve phase shift matching and beam focusing in the case of ultra-short transmission line.

[0191] For the second curved beam homogenization transmission line, the diode with symmetrical upper and lower edge angles at the exit edge is arranged between the 48-level composite iron 1 and the 48-level composite iron 3. The diode with symmetrical upper and lower edge angles at the exit edge of the ultra-short transmission line is used to replace the conventional diode to achieve phase shift matching and beam focusing in the case of ultra-short transmission line.

[0192] (6) For example Figure 6a As shown, the ultrashort linear beam homogenization transmission line is provided with the following components in sequence along the beam direction: accelerator outlet, beam matching mechanism, four-eight-pole composite iron 1, four-eight-pole composite iron 2, beam homogenization effect observation mechanism, and terminal.

[0193] The beam matching mechanism 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.

[0194] This beam homogenization effect observation device is used to observe the beam intensity, weak beam shape, and strong beam cross-section after homogenization by four-octet composite iron 1 and four-octet composite iron 2.

[0195] 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 composite iron 1; and the guide magnet is used to align the beam center with the mechanical center of the beam channel.

[0196] The beam homogenization effect observation mechanism includes a Faraday tube, a fluorescent target 2, and a double wire. The Faraday tube 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 double wire is used to observe the shape of the strong beam after homogenization.

[0197] (7) For example Figure 7a As shown, the ultra-short bendable beam homogenization transmission line comprises two 4 / 8 grade composite iron pieces and one 2 grade iron piece. This ultra-short bendable beam homogenization transmission line is either ultra-short bendable beam homogenization transmission line A or ultra-short bendable beam homogenization transmission line B arranged along the beam direction. Ultra-short bendable beam homogenization transmission line A, along the beam extraction direction, sequentially includes: an accelerator outlet, a beam matching mechanism, 4 / 8 grade composite iron 1, 2 grade iron, and 4 / 8 grade composite iron 2. The ultra-short curved beam homogenization transmission line B is provided with the following components along the beam extraction direction: accelerator outlet, beam matching mechanism, 4-8 composite iron 1, 2-stage iron, 4-8 composite iron 3, beam matching and homogenization effect observation mechanism 2, and terminal 2. The 4-8 composite iron 1 and 4-8 composite iron 2, or 4-8 composite iron 1 and 4-8 composite iron 3, simultaneously generate a quadrupole magnetic field and an octupole magnetic field, so that the functions of a quadrupole iron and an octupole iron can be achieved simultaneously by installing only one transmission element.

[0198] The beam matching mechanism 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.

[0199] The beam matching and homogenization effect observation mechanism 1 or the beam matching and homogenization effect observation mechanism 2 is used to adjust the eccentricity of the beam after passing through the secondary iron, and to observe the beam intensity, weak beam shape and strong beam shape after homogenization by the four-eight-level composite iron 1 and the four-eight-level composite iron 2.

[0200] 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 position; the quadrupole magnet is used to provide a beam envelope in the opposite direction for the 48-pole composite iron 1; and the guide magnet is used to adjust the beam eccentricity.

[0201] The beam matching and homogenization effect observation mechanism 1 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, and the fluorescent target 2 is used to observe the shape of the weak beam after homogenization. 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 includes a guide magnet 3, a Faraday cylinder 3, 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, and the fluorescent target 3 is used to observe the shape of the weak beam after homogenization. The dual-wire 2 is used to observe the shape of the strong beam after homogenization.

[0202] (8) For example Figure 8a As shown, the ultra-short symmetrical bend beam homogenization transmission line is a symmetrical bend beam homogenization transmission line that includes two 48-level composite irons and one shared 2-level iron. This symmetrical bend beam homogenization transmission line, which includes two 48-level composite irons and one shared 2-level iron, consists of one shared transmission line and two symmetrical branch transmission lines.

[0203] like Figure 8a As shown, the common transmission line is provided with the following components along the beam direction: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a 2-stage iron; 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 4 / 8 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 4 / 8 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;

[0204] like Figure 8c 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.

[0205] like Figure 8a As shown, the first curved beam homogenization transmission line and the second curved beam homogenization transmission line have four-eight-pole composite iron 1, four-eight-pole composite iron 2 and four-eight-pole composite iron 3 that simultaneously generate a quadrupole magnetic field and an octupole magnetic field, respectively, so that the function of a quadrupole iron and an octupole iron can be realized simultaneously by installing only one transmission element.

[0206] like Figure 8aAs 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 48-grade composite iron 1 and 48-grade composite iron 2, and observe the weak beam shape and strong beam shape after homogenization.

[0207] like Figure 8a As 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-level composite iron 1 and the four-eight-level composite iron 3, and observe the weak beam shape and strong beam shape after homogenization.

[0208] like Figure 8a , Figure 10 As shown, the diode on the symmetrical bending beam homogenization transmission line based on the ultra-short symmetrical bending beam homogenization substructure is a common diode on the ultra-short symmetrical bending beam homogenization transmission line. This 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 these symmetrical oblique lines is the direction in which the beam bends at the exit edge. The line connecting the center of the beam bending trajectory and 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-eight-level composite iron 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.

[0209] like Figure 8c As shown, the beam matching mechanism on the shared beamline 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 channel.

[0210] like Figure 8d As shown, the beam matching and homogenization effect observation mechanism 1 on the first branch beam line is used to align the beam center and the mechanical center of the beam tube, measure the beam intensity after homogenization by the 48-grade composite iron 1 and 48-grade composite iron 2, and observe the weak beam shape and strong beam shape after homogenization.

[0211] like Figure 8e As shown, the beam matching and homogenization effect observation mechanism 2 on the second branch beam 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-level composite iron 1 and the four-eight-level composite iron 3, and observe the weak beam shape and strong beam shape after homogenization.

[0212] (9) For example Figure 9aAs shown, the ultra-short straight-line-bending composite beam homogenization transmission line consists of a straight beam homogenization transmission line containing two 48-level composite iron pieces and a bending beam homogenization transmission line containing two 48-level composite iron pieces and one 2-level iron piece.

[0213] like Figure 9a As shown, the linear beam homogenization transmission line and the curved beam homogenization transmission line consist of a common transmission line and two branch transmission lines. The common transmission line, along the beam direction, is sequentially equipped with: an accelerator outlet, a beam matching mechanism, a 4 / 8 composite iron 1, and a 4 / 8 composite iron 2. The 4 / 8 composite iron 2, when applied to the curved branch transmission line, only has a quadrupole field and not an 8th-order field. The two branch transmission lines are a linear branch transmission line and a curved branch transmission line. The linear branch transmission line is equipped with a beam homogenization effect observation mechanism and a terminal. The curved branch transmission line is equipped with a secondary iron, a 4 / 8 composite magnet 3, a beam matching and homogenization effect observation mechanism, and a terminal. The common transmission line and the linear branch transmission line form a composite linear beam homogenization transmission line. The common transmission line and the curved branch transmission line form a composite curved beam homogenization transmission line. The composite linear beam homogenization transmission line and the composite curved beam homogenization transmission line operate in a time-division multiplexing manner.

[0214] like Figure 9a As shown, the four-eight-pole composite iron 1 and four-eight-pole composite iron 2 of the composite linear beam homogenization transmission line and the four-eight-pole composite iron 1 and four-eight-pole composite iron 3 of the composite curved beam homogenization transmission line simultaneously generate quadrupole magnetic field and octupole magnetic field, so that the functions of quadrupole iron and octupole iron can be realized simultaneously by installing only one transmission element.

[0215] like Figure 5a , Figure 7b , Figure 8b , 9c As shown, the ultra-short bend-type beam homogenization structure, an ultra-short bend-type beam homogenization transmission line, an ultra-short symmetrical bend-type beam homogenization transmission line, and an ultra-short straight-line bend-type composite beam homogenization transmission line utilize the combined focusing effect of the four-eight-pole composite iron 1 and the dipolar iron to generate a beam waist in the Y direction near the four-eight-pole composite iron 2 or four-eight-pole composite iron 3; and utilize the superposition of the quadrupole fields of the dipolar iron and the four-eight-pole composite iron 2 or the dipolar iron and the four-eight-pole composite iron 3 to generate the envelope size in the X direction on the target, so that the envelope sizes in the X and Y directions are consistent.

[0216] like Figure 4As shown, the ultrashort straight beam homogenization structure, the ultrashort curved beam homogenization structure, an ultrashort straight beam homogenization transmission line, an ultrashort curved beam homogenization transmission line, an ultrashort straight-curved composite beam homogenization transmission line, and an ultrashort symmetrical curved beam homogenization transmission line all exhibit the following characteristics: at the first quadrupole-octupole composite magnet, the beam envelope function in the Y or X direction reaches a large value; at the second quadrupole-octupole composite magnet, the beam envelope function in the X or Y direction reaches a large value; the phase shift of the particle between the two quadrupole-octupole composite magnets and the target... These are respectively close to integer multiples of 180 degrees (0, 1, 2, 3…); the transmission matrix between the two octagonal magnetic fields is close to an identity matrix; the phase shift between the two quadrupole composite magnets and the target… The integer multiples of 180 degrees (0, 1, 2, 3…) refer to integer 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; the transmission matrix is ​​close to the identity matrix, that is, the phase shift between the two four-octet composite magnets is controlled within 30 degrees. This 30-degree range can greatly avoid the high-order nonlinear effects caused by the coupling of the two octet magnets and can achieve a better homogenization effect.

[0217] The expressions for the magnet strength k at the first and second quadrature-octet composite magnets of the ultrashort linear beam homogenization structure, ultrashort curved beam homogenization structure, ultrashort linear beam homogenization transmission line, ultrashort curved beam homogenization transmission line, ultrashort linear-curved composite beam homogenization transmission line, and ultrashort symmetrical curved beam homogenization transmission line are as follows:

[0218]

[0219] Let: the starting point of the transport 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;

[0220] Supplementary note 2

[0221] like Figure 3As shown, the derivation process of the above formulas (1) and (2) is briefly described below: 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.

[0222] This invention also designs a method for adjusting the excitation current of a four / eight-pole composite iron, characterized by the following steps:

[0223] Step 1: Establish a two-dimensional data comparison table for coil current of four-pole iron and eight-pole iron; this two-dimensional data comparison table for coil current is based on the two-dimensional data comparison table for coil current of four / eight-pole composite iron.

[0224] The above two-dimensional data comparison table of coil current is as follows: Figure 2d As shown, the horizontal axis represents the current of the fourth-stage coil, and the vertical axis represents the current of the eighth-stage coil; the specific process is as follows:

[0225] 1) Use Gq to maximize the gradient requirement of the quadrupole field. max This indicates that the maximum demand for the octagonal field gradient is expressed using Go. max express;

[0226] 2) When the current in the four-pole field coil is zero, the eight-pole field coil generates Go. max The current at that time is the maximum operating current I of the octagonal field coil. o When the current in the octagonal field coil is zero, the quadrupole field coil generates Gq. max The current at that time is the maximum operating current I of the four-pole field coil. q ;

[0227] 3) Using the maximum operating current I of the four-pole field coilq and the maximum operating current I of the octagonal field coil o The current data covers the boundary of the two-dimensional data lookup table for coil current, and is measured with equal-interval current changes.

[0228] Step 2: Experimental measurement 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.

[0229] The above-mentioned three-dimensional surface sample database, such as Figure 2e As shown, the current of the four-stage coil is used as the X-axis coordinate, the current of the eight-stage coil is used as the Y-axis coordinate, and the magnetic field gradient is used as the Z-axis coordinate.

[0230] Step 3: Use cubic spline functions to perform two-dimensional interpolation on the three-dimensional surface sample database of the quadrupole magnetic field gradient and the octupole magnetic field gradient to refine the grid point density.

[0231] The effect of the above-mentioned encrypted grid point density is as follows: Figure 10 As shown, the grid density on the X, Y, and Z axes has increased.

[0232] Step 4: Select a quadrupole magnetic field gradient plane. This plane intersects with the surface of the quadrupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the four-level field gradient. Select an octupole magnetic field gradient plane. This plane intersects with the surface of the octupole magnetic field gradient three-dimensional surface sample database to obtain a current curve that satisfies the eight-level field gradient.

[0233] The current curve that satisfies the fourth-order field gradient or the eighth-order field gradient means that the magnetic field gradient is equal at all points on the curve, and the current value at all points on the curve corresponds to a four-pole field coil current and an eight-pole field coil current, respectively.

[0234] Step 5: Obtain the current curves that satisfy the fourth-order field gradient and the current curves that satisfy the eighth-order field gradient in the two-dimensional data grid plane of the coil current, and finally find the intersection point of the two current curves.

[0235] Obtain the current curves that satisfy the fourth-order field gradient and the current curves that satisfy the eighth-order field gradient in the two-dimensional data grid plane of the coil current, and finally find the intersection point of the two current curves. Specifically, project the two current curves that satisfy the requirements of the four-pole field gradient and the eight-pole field gradient respectively onto the same coordinate plane and obtain the intersection point between them.

[0236] Step 6: Use this intersection point as the solution for the composite iron excitation current; the specific process is as follows:

[0237] 1) Obtain the current curves that satisfy all fourth-order field gradients in the three-dimensional surface sample database of the four-pole field magnetic field gradient, and obtain the current curves that satisfy all eighth-order field gradients in the three-dimensional surface sample database of the eight-pole field magnetic field gradient.

[0238] 2) Obtain all intersection points of the current curve satisfying the fourth-order field gradient and the current curve satisfying the eighth-order field gradient;

[0239] 3) Save the current values ​​of the four-pole and eight-pole field coils at all intersection points;

[0240] 4) Input the current gradient requirements for the quadrupole field and the octupole field;

[0241] 5) Based on the current input requirements for the quadrupole gradient and the octupole gradient, find the corresponding intersection point;

[0242] 6) The x-coordinate of the intersection point represents the current value corresponding to the four-pole coil of the four / octole composite iron, and the y-coordinate represents the current value corresponding to the eight-pole coil.

[0243] 7) Input the corresponding current values ​​of the four-pole field coil and the eight-pole field coil into the four / octole composite magnet current control device to finally complete the magnetic field gradient adjustment of the four / octole composite magnet.

[0244] The present invention also designs a method for debugging a linear beam homogenization transmission line, which is based on a four / eight pole composite iron, a four / eight pole composite iron system, an excitation current adjustment method based on the four / eight pole composite iron, and an ultra-short linear beam homogenization transmission line.

[0245] Its characteristic is that the debugging method includes the following steps:

[0246] Step 1: Set the quadrupole field and octupole field currents of the quadrupole iron and the two quadrupole-octupole composite irons to zero;

[0247] Step 2: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current in front of the quadrupole-octupole composite iron 1 so that the beam in the X direction near the quadrupole-octupole composite iron 1 forms a waist.

[0248] The specific process is as follows:

[0249] 1) Starting from zero, gradually increase the quadrupole current in front of the quadrupole composite magnet 1. The envelope size of the beam in the X direction on the fluorescent target gradually decreases. Continue to increase the quadrupole current until the envelope size in the X direction on the target increases. This indicates that the beam in the X direction forms a waist at some point between the quadrupole and the target (close to the target).

[0250] 2) To make the waist of the X-direction beam near the quadrupole-octupole composite iron 1, it is necessary to continue to increase the quadrupole current to shift the waist of the X-direction beam to the left. Stop increasing it when the following condition is met: when the quadrupole field current of the quadrupole-octupole composite iron 1 is increased, it is observed that the size of the X-direction beam envelope on the fluorescent target hardly changes. At this time, the waist of the X-direction beam is near the quadrupole-octupole composite iron 1.

[0251] Supplementary note A

[0252] ① The beam in the X direction near the octet composite iron 1 is formed into a waist shape. Figure 6b As shown, the Y-direction envelope near the quadrupole-octapole composite iron 1 is large. Observing the change in beam spot size on the target cannot accurately determine whether the beam current has a large envelope in the Y direction. Taking the quadrupole-octapole composite iron 1 as an example, a Y-direction envelope size close to 2.5 cm is considered a large envelope. When the quadrupole field current of the quadrupole-octapole composite iron 1 is changed, a significant change in the Y-direction of the beam current on the target can be observed. However, even if the Y-direction envelope is less than 2.5 cm, such as 1 cm, a significant change in the Y-direction of the beam current on the target can still be observed when changing the quadrupole field current of the quadrupole-octapole composite iron 1. Therefore, the change in the beam current envelope on the target cannot be used to determine whether the Y-direction envelope at the quadrupole-octapole composite iron 1 is large. Since the quadrupole in front of the quadrupole-octapole composite iron 1 is focused in the X direction and defocused in the Y direction, when the beam current at the quadrupole-octapole composite iron 1 has a waist-like envelope in the X direction, the Y-direction envelope is considered large.

[0253] ② Adjust the large envelope (with the waist in the X direction) at the four-eight-pole composite iron 1 by adjusting the current of the quadrupole in front of the four-eight-pole composite iron 1. The stronger the current of the quadrupole in front, the higher the beam envelope (dashed line) in the Y direction at the four-eight-pole composite iron 1 will be. This dashed line, together with the quadrupole of the four-eight-pole composite iron 1 itself (the quadrupole of the four-eight-pole composite iron 1 itself is in a focusing state with the dashed line tilted downward at this time), together form the large envelope.

[0254] Step 3: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current of the quadrupole-octupole composite iron 1 in front of the quadrupole-octupole composite iron 2 so that the beam in the Y direction near the quadrupole-octupole composite iron 2 forms a waist, and retain the quadrupole field gradient of the quadrupole-octupole composite iron 1 at this time.

[0255] Supplementary note B

[0256] like Figure 2g As shown, the above-mentioned preservation of the quadrupole field gradient is to allow it to intersect with the subsequent octupole field gradient and the magnetic field gradient surface of the three-dimensional sample database. After the intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2iAs shown, the current value at the intersection point simultaneously satisfies the requirements of both the quadrupole field gradient and the octupole field gradient; thus solving the problem of coupling when the quadrupole and octupole composite iron are combined. The problem is that the current of the quadrupole field coil is adjusted first to adjust the quadrupole magnetic field gradient to meet the requirements, and then the current of the octupole field coil is adjusted. Once the current of the octupole field coil starts to change, it will change the previously adjusted quadrupole magnetic field gradient. This solves the bottleneck problem of beam current uniformity adjustment based on quadrupole and octupole composite iron.

[0257] The specific process is as follows:

[0258] 1) Starting from zero, the quadrupole field current of the quadrupole-octupole composite magnet 1 is gradually increased. The envelope size of the beam in the Y direction is observed to gradually decrease on the fluorescent target. The quadrupole field current of the quadrupole-octupole composite magnet 1 is further increased until the envelope size in the Y direction is observed to increase on the target. This indicates that the beam in the Y direction forms a waist at some point between the quadrupole-octupole composite magnet 1 and the target (close to the target).

[0259] 2) To make the waist of the Y-direction beam near the four-octet composite iron 2, it is necessary to continue to increase the quadrupole field current of the four-octet composite magnet 1 to shift the waist of the Y-direction beam to the left. Stop increasing it when the following condition is met: when the quadrupole field current of the four-octet composite iron 2 is increased, it is observed that the size of the Y-direction beam envelope on the fluorescent target hardly changes. At this time, the waist of the Y-direction beam is near the four-octet composite iron 2.

[0260] Step 4: Adjust the quadrupole current of the quadrupole-octapole composite iron 2 so that the X-direction envelope of the beam on the fluorescent target is consistent with the Y-direction envelope, thus obtaining a circular beam, and retaining the quadrupole field gradient of the quadrupole-octapole composite iron 2 at this time; the specific process is as follows:

[0261] After steps one to three, ideally the envelope size of the beam in the X direction should be greater than the envelope size in the Y direction. Starting from zero, the quadrupole field current of the four-octupole composite magnet 2 is gradually increased. It is observed on the fluorescent target that the envelope size of the beam in the X direction gradually decreases. Continue to increase the quadrupole field current of the four-octupole composite magnet 2 until the envelope size in the X direction is observed to be consistent with the envelope size in the Y direction on the target.

[0262] If the envelope dimensions in the X and Y directions do not meet expectations after steps one through three, the following adjustment methods should be adopted respectively:

[0263] 1) If the size of the fluorescent target beam in the X direction is larger than the target size, reduce the quadrupole iron current in front of the quadrupole-octupole composite magnet 1 or increase the quadrupole field current of the quadrupole-octupole composite magnet 2; if the size of the beam in the X direction is smaller than the target size, increase the quadrupole iron current in front of the quadrupole-octupole composite magnet 1 or decrease the quadrupole field current of the quadrupole-octupole composite magnet 2.

[0264] 2) If the envelope size of the beam in the Y direction on the fluorescent target is larger than the target size, reduce the quadrupole field current of the quadrupole-octupole composite magnet 1; if the size of the beam in the Y direction is smaller than the target size, increase the quadrupole field current of the quadrupole-octupole composite magnet 1.

[0265] The target size mentioned above is as follows: a square target is usually set at the end of the transmission line. If the side length of the target is L, then the target size is L, that is, the diameter of the circular bundle is L.

[0266] After adjustment, it is necessary to reconfirm, according to the method described in claims 2 and 3, that the waist of the beam in the X direction is near the octet composite iron 1 and the waist of the beam in the Y direction is near the octet composite iron 2.

[0267] Supplementary note C

[0268] The fluorescent target described in this invention is as follows: Figure 6d As shown, this refers to fluorescent target 2, which is positioned behind the four-octet composite iron 2, approximately at the 5.4-meter mark of the 6-meter-long transmission line.

[0269] Step 5: Adjust the octet field of the four-octet composite iron 1 to adjust the beam homogenization effect in the Y direction. Based on the four-octet field gradient of the four-octet composite iron 1 recorded in Step 3 and the current octet field gradient of the four-octet composite iron 1, calculate the intersection current that simultaneously satisfies the four-octet field gradient and the octet field gradient of the four-octet composite iron 1, and retain the current octet field gradient of the four-octet composite iron 1; specifically:

[0270] If the brightness of the beam spot in the Y direction on the fluorescent target is not uniform, and the center of the beam spot in the Y direction is bright while the two sides are dark, then increase the eighth-level field current of the four-octet composite magnet 1 until the brightness distribution of the beam spot in the Y direction on the fluorescent target is uniform and the shape of the beam spot changes from circular to rectangular. If the two sides of the beam spot in the Y direction on the fluorescent target are bright while the center is dark, then decrease the eighth-level field current of the four-octet composite magnet 1 until the brightness distribution of the beam spot in the Y direction on the fluorescent target is uniform and the shape of the beam spot changes from circular to rectangular.

[0271] Supplementary note D

[0272] In step five, the intersection point current is calculated for the first time. When adjusting the octapole beam in step five, the previously adjusted quadrupole beam current will also change. To address the issue of the quadrupole beam current also changing, it is necessary to find their intersection point current (this is the first time the intersection point current is calculated). This involves intersecting the current octapole beam gradient with the previously retained quadrupole beam gradient and the magnetic field gradient surface in the 3D sample database (this is the first time a plane intersects a surface). After intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2iAs shown, the current value at the intersection point satisfies both the requirements of the current octet field gradient and the requirements of the quadrupole field gradient. This solves the problem of coupling when the quadrupole-octet composite iron is combined together.

[0273] Step 6: If the beam homogenization is not significantly improved when adjusting the octet field current of the four-octet composite iron 1, the four-octet field gradient of the four-octet composite iron 1 needs to be modified for phase shift matching so that the phase shift of the four-octet composite iron 1 to the target in the Y direction is close to 180°. That is, based on the adjusted four-octet field gradient of the four-octet composite iron 1 and the octet field gradient retained in step 5, the intersection current that simultaneously satisfies the four-octet field gradient and the octet field gradient of the four-octet composite iron 1 is calculated.

[0274] Supplementary note E

[0275] In step six, the intersection point current is calculated for the second time. The first calculation of the intersection point current was performed when adjusting the octagonal field of the four-octagonal composite iron 1 to improve the beam homogenization in the Y direction. The second calculation is performed because the beam homogenization is not significantly improved when adjusting the octagonal field current of the four-octagonal composite iron 1. Therefore, it is necessary to modify the four-octagonal field gradient of the four-octagonal composite iron 1 for phase shift matching. Since the four-octagonal field gradient has changed, the new four-octagonal field gradient and the octagonal field gradient retained in step five are intersected with the magnetic field gradient surface of the three-dimensional sample database (this is the second time the plane intersects the surface). After intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2i As shown, the current value at the intersection point satisfies both the requirements of the current octet field gradient and the requirements of the quadrupole field gradient. This solves the problem of coupling when the quadrupole-octet composite iron is combined together.

[0276] The specific process is as follows:

[0277] 1) Increase the octagonal field current of the four-octagonal composite magnet 1 and observe whether the brightness change of the beam spot in the Y direction on the fluorescent target is significant. If the brightness in the middle and both sides of the beam spot in the Y direction on the fluorescent target remains almost unchanged, it indicates that the phase shift of the four-octagonal composite magnet 1 to the target in the Y direction is large compared to 180°. If the middle of the beam spot in the Y direction on the fluorescent target changes from bright to dark and the sides change from dark to bright, or the middle changes from dark to bright and the sides change from bright to dark, it indicates that the phase shift of the four-octagonal composite magnet 1 to the target in the Y direction is close to 180°. Brightness indicates a high number of particles, and darkness indicates a low number of particles.

[0278] 2) When the brightness change of the beam spot in the Y direction on the fluorescent target is not obvious, it proves that the difference between the beam current Y phase shift and 180 degrees between the four-octet composite magnet 1 and the target is large. Assuming that the current phase shift is less than 180 degrees, decrease the quadrupole iron current in front of the four-octet composite magnet 1, or increase the quadrupole iron current of the four-octet composite magnet 1. After completing the operation, observe again according to the method in 1). If the brightness change of the beam spot in the Y direction on the fluorescent target is significant when the octet field current of the four-octet composite magnet 1 is increased, it means that the hypothesis is correct. If the brightness of the beam spot in the Y direction on the fluorescent target is almost unchanged, it means that the current phase shift is greater than 180 degrees. Then increase the quadrupole iron current in front of the four-octet composite magnet 1, or decrease the quadrupole iron current of the four-octet composite magnet 1. After completing the operation, observe again according to the method in 1) until the brightness change of the beam spot in the Y direction on the fluorescent target is significant when the octet field current of the four-octet composite magnet 1 is increased. The fine adjustment of the phase shift of the four-octet composite magnet 1 to close to 180 degrees is completed.

[0279] Step 7: Adjust the octet field of the four-octet composite iron 2 to adjust the beam homogenization effect in the X direction. Based on the four-octet field gradient of the four-octet composite iron 2 recorded in Step 4 and the current octet field gradient of the four-octet composite iron 2, calculate the intersection current that simultaneously satisfies the four-octet field gradient and the octet field gradient of the four-octet composite iron 2, and retain the octet field gradient of the four-octet composite iron 2 at this time; the specific process is as follows:

[0280] If the brightness of the beam spot on the fluorescent target is uneven in the X direction, and the center of the beam spot is bright while the two sides are dark in the X direction, then increase the eighth-level field current of the four-octet composite magnet 2 until the brightness distribution of the beam spot on the fluorescent target is uniform in the X direction and the shape of the beam spot changes from a rectangle to a square. If the beam spot on the fluorescent target is bright on the two sides and dark in the center in the X direction, then decrease the eighth-level field current of the four-octet composite magnet 2 until the brightness distribution of the beam spot on the fluorescent target is uniform in the X direction and the shape of the beam spot changes from a rectangle to a square.

[0281] Supplementary note F

[0282] In step seven, the intersection point current is calculated for the third time. The intersection point current obtained in the third calculation is different from that in the previous two calculations. In the previous two calculations, the octagonal field of the four-octagonal composite iron 1 was adjusted, while in the third calculation, the octagonal field of the four-octagonal composite iron 2 was adjusted.

[0283] The third calculation of the intersection point current is different from the first two. The first two calculations of the intersection point current involved adjusting the octagonal field of the four-octagonal composite iron 1, while the third calculation involved adjusting the octagonal field of the four-octagonal composite iron 2.

[0284] Step 8: If adjusting the octet field current of the four-octet composite iron 2 does not significantly improve beam homogenization, it is necessary to increase the beam envelope in the X direction at the four-octet composite iron 2; the specific process is as follows:

[0285] 1) Increase the octagonal field current of the four-octagonal composite magnet 2 and observe whether the brightness change of the beam spot in the X direction on the fluorescent target is significant. If the brightness in the middle and both sides of the beam spot in the X direction on the fluorescent target remains almost unchanged, it indicates that the beam current envelope in the X direction at the four-octagonal composite magnet 2 is small. If the middle of the beam spot in the X direction on the fluorescent target changes from bright to dark and the sides change from dark to bright, or the middle changes from dark to bright and the sides change from bright to dark, it indicates that the size of the beam current envelope in the X direction at the four-octagonal composite magnet 2 meets the uniformity requirements. Brightness indicates a large number of particles, and darkness indicates a small number of particles.

[0286] 2) When the brightness of the beam spot in the X direction on the fluorescent target does not change significantly, increase the quadrupole current and observe again, as in 1), whether the brightness of the beam spot in the X direction on the fluorescent target changes significantly when the octupole field current of the quadrupole-octupole composite magnet 2 is increased. If the brightness of the beam spot does not change significantly, continue to increase the quadrupole current; if the brightness of the beam spot changes significantly, then the size of the beam envelope in the X direction at the quadrupole-octupole composite magnet 2 has met the homogenization requirements, and the adjustment is complete.

[0287] Supplementary note G

[0288] In step eight, the intersection point current was not calculated further because: if adjusting the octet field current of the four-octet composite iron 2 does not significantly homogenize the beam current in the X direction on the target, then it is necessary to increase the beam current envelope in the X direction at the four-octet composite iron 2. However, at this point, the phase shift of the beam current from the four-octet composite iron 2 to the target in the X direction is already close to 0 degrees. Therefore, the phase shift method cannot solve the problem of increasing the beam current envelope in the X direction at the four-octet composite iron 2. It is necessary to increase the quadrupole current in front of the four-octet composite iron 1. Figure 6b It can be seen that when the quadrupole current is increased, the beam current envelope in the X direction at the octupole composite iron 2 will increase until the beam current in the X direction on the target becomes significantly homogenized when the octupole field current of the quadrupole composite iron 2 is changed.

[0289] The present invention also designs a method for debugging a curved beam homogenization transmission line, which is based on a four / eight pole composite iron, a four / eight pole composite iron system, a method for adjusting the excitation current of a four / eight pole composite iron, and an ultra-short curved beam homogenization transmission line.

[0290] Its characteristic is that the debugging method includes the following steps:

[0291] Step 1: Set the quadrupole field and octupole field currents of the quadrupole iron and the two quadrupole-octupole composite irons to zero;

[0292] Step 2: Adjust the diode current so that the center of the beam spot is roughly aligned with the center of the fluorescent target;

[0293] The specific process is as follows:

[0294] To protect the components on the transmission line, calculate and set the initial current value of the diode based on the current beam parameters and the number of turns of the diode coil. Observe whether a beam appears on the fluorescent target. If not, adjust the diode current value near the initial current value until a beam appears on the fluorescent target. At this time, the quadrupole field current of the tetrapole and the two tetrapole-octapole composite irons are both zero, and the beam envelope is relatively large. Once the beam is roughly aligned with the target center, proceed to the next step.

[0295] Step 3: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole current in front of the quadrupole-octupole composite iron 1 so that the beam in the X direction near the quadrupole-octupole composite iron 1 forms a waist.

[0296] The specific process is as follows:

[0297] 1) Starting from zero, gradually increase the quadrupole current in front of the quadrupole composite magnet 1. The envelope size of the beam in the X direction on the fluorescent target gradually decreases. Continue to increase the quadrupole current until the envelope size in the X direction on the target increases. This indicates that the beam in the X direction forms a waist at some point between the quadrupole and the target (close to the target).

[0298] 2) To make the waist of the X-direction beam near the quadrupole-octupole composite iron 1, it is necessary to continue to increase the quadrupole current to shift the waist of the X-direction beam to the left. Stop increasing it when the following condition is met: when the quadrupole field current of the quadrupole-octupole composite iron 1 is increased, it is observed that the size of the X-direction beam envelope on the fluorescent target hardly changes. At this time, the waist of the X-direction beam is near the quadrupole-octupole composite iron 1.

[0299] Supplementary note A

[0300] ① The described beam forming a waist in the X direction near the octet composite iron 1, such as... Figure 7b As shown, the Y-direction envelope near the quadrupole-octapole composite iron 1 is large. Observing the change in beam spot size on the target cannot accurately determine whether the beam current has a large envelope in the Y direction. Taking the quadrupole-octapole composite iron 1 as an example, a Y-direction envelope size close to 2.5 cm is considered a large envelope. When the quadrupole field current of the quadrupole-octapole composite iron 1 is changed, a significant change in the Y-direction of the beam current on the target can be observed. However, even if the Y-direction envelope is less than 2.5 cm, such as 1 cm, a significant change in the Y-direction of the beam current on the target can still be observed when changing the quadrupole field current of the quadrupole-octapole composite iron 1. Therefore, the change in the beam current envelope on the target cannot be used to determine whether the Y-direction envelope at the quadrupole-octapole composite iron 1 is large. Since the quadrupole in front of the quadrupole-octapole composite iron 1 is focused in the X direction and defocused in the Y direction, when the beam current at the quadrupole-octapole composite iron 1 has a waist-like envelope in the X direction, the Y-direction envelope is considered large.

[0301] ② Adjust the large envelope (with the waist in the X direction) at the four-eight-pole composite iron 1 by adjusting the current of the quadrupole in front of the four-eight-pole composite iron 1. The stronger the current of the quadrupole in front, the higher the beam envelope (dashed line) in the Y direction at the four-eight-pole composite iron 1 will be. This dashed line, together with the quadrupole of the four-eight-pole composite iron 1 itself (the quadrupole of the four-eight-pole composite iron 1 itself is in a focusing state with the dashed line tilted downward at this time), together form the large envelope.

[0302] Step 4: Observe the changes in the beam envelope on the fluorescent target and adjust the quadrupole field current of the quadrupole-octupole composite iron 1 in front of the diode. Under the combined action of the edge field of the diode and the quadrupole field of the quadrupole-octupole composite iron 1, the beam in the Y direction near the quadrupole-octupole composite iron 2 is made to form a waist, and the quadrupole field gradient of the quadrupole-octupole composite iron 1 is preserved at this time.

[0303] The specific process is as follows:

[0304] 1) Starting from zero, the quadrupole field current of the quadrupole-octupole composite magnet 1 is gradually increased. The envelope size of the beam in the Y direction is observed to gradually decrease on the fluorescent target. The quadrupole field current of the quadrupole-octupole composite magnet 1 is further increased until the envelope size in the Y direction is observed to increase on the target. This indicates that the beam in the Y direction forms a waist at some point between the quadrupole-octupole composite magnet 1 and the target (close to the target).

[0305] 2) To make the waist of the Y-direction beam near the four-octet composite iron 2, it is necessary to continue to increase the quadrupole field current of the four-octet composite magnet 1 to shift the waist of the Y-direction beam to the left. Stop increasing it when the following condition is met: when the quadrupole field current of the four-octet composite iron 2 is increased, it is observed that the size of the Y-direction beam envelope on the fluorescent target hardly changes. At this time, the waist of the Y-direction beam is near the four-octet composite iron 2.

[0306] Supplementary note B

[0307] like Figure 2g As shown, the above-mentioned preservation of the quadrupole field gradient is to allow it to intersect with the subsequent octupole field gradient and the magnetic field gradient surface of the three-dimensional sample database. After the intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2i As shown, the current value at the intersection point simultaneously satisfies the requirements of both the quadrupole field gradient and the octupole field gradient; thus solving the problem of coupling when the quadrupole and octupole composite iron are combined. The problem is that the current of the quadrupole field coil is adjusted first to adjust the quadrupole magnetic field gradient to meet the requirements, and then the current of the octupole field coil is adjusted. Once the current of the octupole field coil starts to change, it will change the previously adjusted quadrupole magnetic field gradient. This solves the bottleneck problem of beam current uniformity adjustment based on quadrupole and octupole composite iron.

[0308] Step 5: Adjust the quadrupole current of the quadrupole-octupole composite iron 2 so that the X-direction envelope of the beam on the fluorescent target is consistent with the Y-direction envelope to obtain a circular beam. Adjust the diode current again to align the beam spot center with the target center and retain the quadrupole field gradient of the quadrupole-octupole composite iron 2 at this time.

[0309] Supplementary note C

[0310] The fluorescent target described in this invention is as follows: Figure 6d As shown, this refers to fluorescent target 2, which is positioned behind the four-octet composite iron 2, approximately at the 5.4-meter mark of the 6-meter-long transmission line.

[0311] The specific process is as follows:

[0312] After steps one to four, ideally the envelope size of the beam in the X direction should be greater than the envelope size in the Y direction. Starting from zero, the quadrupole field current of the four-octupole composite magnet 2 is gradually increased. The envelope size of the beam in the X direction is observed to gradually decrease on the fluorescent target. The quadrupole field current of the four-octupole composite magnet 2 is continued to be increased until the envelope size in the X direction is observed to be consistent with the envelope size in the Y direction on the target.

[0313] If the envelope dimensions in the X and Y directions do not meet expectations after steps one through four, the following adjustment methods should be adopted respectively:

[0314] 1) If the size of the fluorescent target beam in the X direction is larger than the target size, reduce the quadrupole iron current in front of the quadrupole-octupole composite magnet 1 or increase the quadrupole field current of the quadrupole-octupole composite magnet 2; if the size of the beam in the X direction is smaller than the target size, increase the quadrupole iron current in front of the quadrupole-octupole composite magnet 1 or decrease the quadrupole field current of the quadrupole-octupole composite magnet 2.

[0315] 2) If the envelope size of the beam in the Y direction on the fluorescent target is larger than the target size, reduce the quadrupole field current of the quadrupole-octupole composite magnet 1; if the size of the beam in the Y direction is smaller than the target size, increase the quadrupole field current of the quadrupole-octupole composite magnet 1.

[0316] The target dimensions mentioned above are as follows: A square target is typically placed at the end of the transmission line. If the side length of the target is L, then the target dimension is... That is, the diameter of the circular bundle is

[0317] After the above operations, the beam spot can be clearly observed on the target. The diode current is then adjusted again to align the center of the beam spot with the center of the target. After adjustment, it is necessary to reconfirm, according to the method described in claims 2 and 3, that the waist of the beam in the X direction is near the quadrature-octet composite iron 1 and the waist of the beam in the Y direction is near the quadrature-octet composite iron 2.

[0318] Step 6: Adjust the octagonal field of the four-octagonal composite iron 1 to adjust the beam homogenization effect in the Y direction. Based on the four-octagonal field gradient of the four-octagonal composite iron 1 recorded in Step 4 and the current octagonal field gradient of the four-octagonal composite iron 1, calculate the intersection current that simultaneously satisfies the four-octagonal field gradient and the octagonal field gradient of the four-octagonal composite iron 1, and retain the octagonal field gradient of the four-octagonal composite iron 1 at this time.

[0319] The specific process is as follows:

[0320] If the brightness of the beam spot in the Y direction on the fluorescent target is not uniform, and the center of the beam spot in the Y direction is bright while the two sides are dark, then increase the eighth-level field current of the four-octet composite magnet 1 until the brightness distribution of the beam spot in the Y direction on the fluorescent target is uniform and the shape of the beam spot changes from circular to rectangular. If the two sides of the beam spot in the Y direction on the fluorescent target are bright while the center is dark, then decrease the eighth-level field current of the four-octet composite magnet 1 until the brightness distribution of the beam spot in the Y direction on the fluorescent target is uniform and the shape of the beam spot changes from circular to rectangular.

[0321] Supplementary note D

[0322] In step six, the intersection point current is calculated for the first time. The reason for calculating the intersection point current is that when adjusting the octapole beam in step six, the previously adjusted quadrupole beam current will also change. To address the issue of the quadrupole beam current also changing, it is necessary to find their intersection point current (this is the first time the intersection point current is obtained). This involves intersecting the current octapole beam gradient with the previously retained quadrupole beam gradient and then with the magnetic field gradient surface of the 3D sample database (this is the first time a plane intersects a surface). After intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2i As shown, the current value at the intersection point satisfies both the requirements of the current octet field gradient and the requirements of the quadrupole field gradient. This solves the problem of coupling when the quadrupole-octet composite iron is combined together.

[0323] Step 7: If the beam homogenization is not significantly changed when adjusting the octet field current of the four-octet composite iron 1, it is necessary to modify the four-electrode field gradient of the four-octet composite iron 1 for phase shift matching, so that the phase shift of the four-octet composite iron 1 to the target in the Y direction is close to 180°. That is, based on the adjusted four-electrode field gradient of the four-octet composite iron 1 and the octet field gradient retained in step 6, the intersection current that simultaneously satisfies the four-electrode field gradient and the octet field gradient of the four-octet composite iron 1 is calculated.

[0324] Supplementary note E

[0325] In step seven, the intersection point current is calculated for the second time. The first calculation of the intersection point current was performed when adjusting the octagonal field of the four-octagonal composite iron 1 to improve the beam homogenization in the Y direction. The second calculation is performed because adjusting the octagonal field current of the four-octagonal composite iron 1 does not significantly improve beam homogenization. Therefore, it is necessary to modify the four-octagonal field gradient of the four-octagonal composite iron 1 for phase shift matching. Since the four-octagonal field gradient has changed, the new four-octagonal field gradient and the octagonal field gradient retained in step five are intersected with the magnetic field gradient surface of the three-dimensional sample database (this is the second time the plane intersects the surface). After intersection, as shown... Figure 2h As shown, two corresponding current curves are obtained. The intersection point of these two current curves is as follows: Figure 2i As shown, the current value at the intersection point satisfies both the requirements of the current octet field gradient and the requirements of the quadrupole field gradient. This solves the problem of coupling when the quadrupole-octet composite iron is combined together.

[0326] Specifically:

[0327] 1) Increase the octagonal field current of the four-octagonal composite magnet 1 and observe whether the brightness change of the beam spot in the Y direction on the fluorescent target is significant. If the brightness in the middle and both sides of the beam spot in the Y direction on the fluorescent target remains almost unchanged, it indicates that the phase shift of the four-octagonal composite magnet 1 to the target in the Y direction is large compared to 180°. If the middle of the beam spot in the Y direction on the fluorescent target changes from bright to dark and the sides change from dark to bright, or the middle changes from dark to bright and the sides change from bright to dark, it indicates that the phase shift of the four-octagonal composite magnet 1 to the target in the Y direction is close to 180°. Brightness indicates a high number of particles, and darkness indicates a low number of particles.

[0328] 2) When the brightness change of the beam spot in the Y direction on the fluorescent target is not obvious, it proves that the difference between the beam current Y phase shift and 180 degrees between the four-octet composite magnet 1 and the target is large. Assuming that the current phase shift is less than 180 degrees, decrease the quadrupole iron current in front of the four-octet composite magnet 1, or increase the quadrupole iron current of the four-octet composite magnet 1. After completing the operation, observe again according to the method in 1). If the brightness change of the beam spot in the Y direction on the fluorescent target is significant when the octet field current of the four-octet composite magnet 1 is increased, it means that the hypothesis is correct. If the brightness of the beam spot in the Y direction on the fluorescent target is almost unchanged, it means that the current phase shift is greater than 180 degrees. Then increase the quadrupole iron current in front of the four-octet composite magnet 1, or decrease the quadrupole iron current of the four-octet composite magnet 1. After completing the operation, observe again according to the method in 1) until the brightness change of the beam spot in the Y direction on the fluorescent target is significant when the octet field current of the four-octet composite magnet 1 is increased. The fine adjustment of the phase shift of the four-octet composite magnet 1 to close to 180 degrees is completed.

[0329] Step 8: Adjust the octagonal field of the four-octagonal composite iron 2 to adjust the beam homogenization effect in the X direction. Based on the four-octagonal field gradient of the four-octagonal composite iron 2 recorded in Step 5 and the current octagonal field gradient of the four-octagonal composite iron 2, calculate the intersection current that simultaneously satisfies the four-octagonal field gradient and the octagonal field gradient of the four-octagonal composite iron 2, and retain the octagonal field gradient of the four-octagonal composite iron 2 at this time.

[0330] Specifically:

[0331] If the brightness of the beam spot on the fluorescent target is uneven in the X direction, and the center of the beam spot is bright while the two sides are dark in the X direction, then increase the eighth-level field current of the four-octet composite magnet 2 until the brightness distribution of the beam spot on the fluorescent target is uniform in the X direction and the shape of the beam spot changes from a rectangle to a square. If the beam spot on the fluorescent target is bright on the two sides and dark in the center in the X direction, then decrease the eighth-level field current of the four-octet composite magnet 2 until the brightness distribution of the beam spot on the fluorescent target is uniform in the X direction and the shape of the beam spot changes from a rectangle to a square.

[0332] Supplementary note F

[0333] In step eight, the intersection point current is calculated for the third time. The intersection point current obtained in the third calculation is different from that in the previous two calculations. In the previous two calculations, the octagonal field of the four-octagonal composite iron 1 was adjusted, while in the third calculation, the octagonal field of the four-octagonal composite iron 2 was adjusted.

[0334] Step 9: If adjusting the octet field current of the four-octet composite iron 2 does not significantly improve beam homogenization, it is necessary to increase the beam envelope in the X direction at the four-octet composite iron 2; the specific process is as follows:

[0335] 1) Increase the octagonal field current of the four-octagonal composite magnet 2 and observe whether the brightness change of the beam spot in the X direction on the fluorescent target is significant. If the brightness in the middle and both sides of the beam spot in the X direction on the fluorescent target remains almost unchanged, it indicates that the beam current envelope in the X direction at the four-octagonal composite magnet 2 is small. If the middle of the beam spot in the X direction on the fluorescent target changes from bright to dark and the sides change from dark to bright, or the middle changes from dark to bright and the sides change from bright to dark, it indicates that the size of the beam current envelope in the X direction at the four-octagonal composite magnet 2 meets the uniformity requirements. Brightness indicates a large number of particles, and darkness indicates a small number of particles.

[0336] 2) When the brightness of the beam spot in the X direction on the fluorescent target does not change significantly, increase the quadrupole current and observe again, as in 1), whether the brightness of the beam spot in the X direction on the fluorescent target changes significantly when the octupole field current of the quadrupole-octupole composite magnet 2 is increased. If the brightness of the beam spot does not change significantly, continue to increase the quadrupole current; if the brightness of the beam spot changes significantly, then the size of the beam envelope in the X direction at the quadrupole-octupole composite magnet 2 has met the homogenization requirements, and the adjustment is complete.

[0337] Supplementary note G

[0338] In step nine, the intersection point current was not calculated further because the phase shift of the beam from the quadrupole-octapole composite iron 2 to the target in the X direction is close to 0 degrees. The phase shift method is no longer sufficient to increase the beam current envelope in the X direction at the quadrupole-octapole composite iron 2. It is necessary to increase the quadrupole current in front of the quadrupole-octapole composite iron 1. Figure 7b It can be seen that when the quadrupole current is increased, the beam current envelope in the X direction at the octupole composite iron 2 will increase until the beam current in the X direction on the target becomes significantly homogenized when the octupole field current of the quadrupole composite iron 2 is changed.

[0339] Example 1

[0340] like Figure 14 As shown, this invention designs an ultrashort linear beam homogenization transmission line. When the total length of the ultrashort linear beam homogenization transmission line is 6 meters, the initial placement positions of the components that enable the transmission line 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 900 mm; the initial position of the guide magnet is 1300 mm; the initial position of the quadrupole-octupole composite iron (Q1) is 1900 mm; the initial position of the quadrupole-octupole composite iron (Q2) is 3050 mm; the initial position of the Faraday cylinder is 4200 mm; the initial position of the fluorescent target 2 is 5200 mm; the initial position of the dual wire is 5600 mm; and the initial position of the terminal is 6000 mm. The magnetic field component of the tetrapole iron (Q0) is 2.9 (T / m); the tetrapole magnetic field component of the tetrapole-octapole composite iron (Q1) is 3.05 (T / m), and the octapole magnetic field component is 2.5e3 (T / m). 3 The quadrupole magnetic field component of the four-pole octupole composite iron (Q2) is 0.45 (T / m), and the octupole magnetic field component is 3.82e3 (T / m). 3 ).

[0341] like Figure 6e The image shows a comparison of the transmission line before and after homogenization according to the present invention. Figure 6e 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 6e The right figure shows the beam cross-section after homogenization, which is the beam cross-section of fluorescent target 2 at the transmission line position of 5200 mm. As can be seen from the figure, before homogenization, the particle distribution on the beam cross-section is 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.

[0342] Example 2

[0343] like Figure 15As shown, this invention designs an ultra-short bendable beam homogenization transmission line. When the total length of the ultra-short bendable beamline is 6, the initial placement positions of the components that enable the beamline to achieve a better homogenization effect are as follows: the initial position of the fluorescent target 1 is 100mm, the initial position of the quadrupole magnet (Q0) is 1300mm; the initial position of the guide magnet 1 is 1650mm; the initial position of the quadrupole-octupole composite iron (Q1) is 2100mm, the initial position of the dipole iron is 2700mm, the initial position of the quadrupole-octupole composite iron (Q2) is 3850mm; the initial position of the guide magnet 2 is 4250mm; the initial position of the Faraday cylinder is 4700mm; the initial position of the fluorescent target 2 is 5350mm, the initial position of the dual wire is 5750mm; and the initial position of the terminal is 6000mm.

[0344] The magnetic field component of the tetrapole iron (Q0) is 6.8 (T / m); the tetrapole magnetic field component of the tetrapole-octapole composite iron (Q1) is 2.25 (T / m), and the octapole magnetic field component is 1e4 (T / m). 3 The quadrupole magnetic field component of the four-octupole composite iron (Q2) is 0.6 (T / m), and the octupole magnetic field component is 6.25e3 (T / m). 3 The beam is deflected by 90°, with both the incident and exit angles at 45° and a deflection radius of 0.55m.

[0345] like Figure 7e The image shows a comparison of the transmission line before and after homogenization according to the present invention. Figure 7e 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 7e The right figure shows the beam cross-section after homogenization, which is the beam cross-section of fluorescent target 2 at the transmission line position of 5350 mm. As can be seen from the figure, before homogenization, the particle distribution on the beam cross-section is 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.

[0346] Example 3

[0347] like Figure 16As 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.

[0348] 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°.

[0349] like Figure 8f As shown, this is a comparison of the transmission line before and after homogenization according to the present invention. Figure 8f 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 8f 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.

[0350] Example 4

[0351] like Figure 17As shown, this invention designs an ultrashort straight-line bending composite beam homogenization transmission line. When the total length of the ultrashort straight-line bending composite beam homogenization transmission line is 6 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 1150 mm; the initial position of the quadrupole-octupole composite iron (Q1) is 1800 mm; the initial position of the quadrupole-octupole composite iron (Q2) is 2600 mm; the initial position of the dipole iron is 3600 mm; the initial position of the quadrupole-octupole composite iron (Q3) is 4700 mm; the initial position of the guide magnet 2 is 5200 mm; the initial position of the Faraday cylinder 1 is 5500 mm; the initial position of the fluorescent target 2 is 5950 mm; the initial position of the dual wire 1 is 6250 mm; and the initial position of the terminal 1 is 6500 mm. The initial position of Faraday tube 2 is 4450 mm; the initial position of fluorescent target 3 is 5150 mm; the initial position of dual wire 2 is 5600 mm; and the initial position of terminal 2 is 6000 mm.

[0352] The magnetic field component of the tetrapole iron (Q0) is 6.2 (T / m); the fourpole magnetic field components of the tetrapole-octapole composite iron (Q1) are 3.57 / 3.0 (T / m), and the octapole magnetic field components are 2.25e3 / 3.75e3 (T / m). 3 The quadrupole magnetic field component of the four-pole octupole composite iron (Q2) is 3.5 / 0.75 (T / m), and the octupole magnetic field component is 0 / 7.5e3 (T / m). 3 The beam is deflected by 90°, with an incident and exit angle of 45° and a deflection radius of 0.5m; the quadrupole magnetic field component of the four-octupole composite iron (Q3) is 1.0 (T / m), and the octupole magnetic field component is 5e. 3 (T / m 3 ).

[0353] like Figure 9g The image shows a comparison of the composite curved beam homogenization transmission line before and after homogenization. Figure 9g 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 9g The right figure shows the beam cross-section after homogenization, which is the beam cross-section of fluorescent target 2 at the transmission line position of 5950 mm. As can be seen from the figure, before homogenization, the particle distribution on the beam cross-section is 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.

[0354] like Figure 9h The image shows a comparison of the composite linear beam homogenization transmission line before and after homogenization. Figure 9hThe 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 9h The right figure shows the beam cross-section after homogenization, which is the beam cross-section of the fluorescent target 3 at the transmission line position of 5150 mm. As can be seen from the figure, before homogenization, the particle distribution on the beam cross-section is 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 the edges.

[0355] 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. A system for uniformizing transmission of an ultra-short beam based on a four-pole composite magnet, characterized in that: The transmission line system comprises a four-octupole composite magnet, a four-octupole composite magnet system, an ultra-short straight-line type beam homogenization structure, an ultra-short bending type beam homogenization structure, a dipole iron for an ultra-short symmetric bending type beam homogenization transmission line; The application further comprises an ultra-short straight-line type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system and the ultra-short straight-line type beam homogenization structure; The application further comprises an ultra-short bending type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system and the ultra-short bending type beam homogenization structure; The application further comprises an ultra-short straight-line bending composite type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system, the ultra-short straight-line type beam homogenization structure and the ultra-short bending type beam homogenization structure; The application further comprises an ultra-short symmetric bending type beam homogenization transmission line based on the four-octupole composite magnet, the four-octupole composite magnet system, the ultra-short bending type beam homogenization structure and the dipole iron for the ultra-short symmetric bending type beam homogenization transmission line; The four-octupole composite magnet comprises eight pole heads, each of which is provided with inner and outer two layers of current coils in the radial direction close to the major radius, the inner layer of coils being eight-pole magnetic field excitation coils and the outer layer of coils being four-pole magnetic field excitation coils; the four-octupole composite magnet is arranged on the ultra-short beam homogenization transmission line and is used to generate a large envelope in the Y direction together with the four-pole iron in front of the four-octupole composite magnet at a position A of the four-octupole composite iron and to generate a large envelope in the X direction together with the four-pole iron of the four-octupole composite iron A in front of the four-octupole composite magnet B at a position B of the four-octupole composite magnet, so as to homogenize the Gaussian distributed beam, and the four-octupole composite magnet is installed on the beam transmission line, which can reduce the number of transmission elements and shorten the length of the transmission line; The four-octupole composite magnet system comprises a composite magnet current control device, a composite magnet main power supply and a four-octupole composite magnet; the composite magnet current control device is used to control the four-pole field coil current output and the eight-pole field coil current output of the four-octupole composite magnet by the composite magnet main power supply; the four-octupole composite magnet is used to simultaneously generate 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 ultra-short straight-line type beam homogenization structure uses two four-octupole composite magnets on the transmission line, and the two four-octupole composite magnets simultaneously generate a four-pole magnetic field and an eight-pole magnetic field, respectively, 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 ultra-short bending type beam homogenization structure realizes an bending type beam homogenization substructure and a symmetric bending type beam homogenization substructure by using a dipole iron and multiple four-octupole composite irons on the transmission line; the bending type beam homogenization substructure is used to realize a bending type beam homogenization transmission line; and the symmetric bending type beam homogenization substructure is used to realize an ultra-short symmetric bending type beam homogenization transmission line. The dipole iron for the ultra-short symmetrical bending type beam homogenization transmission line is a shared dipole iron, and the shared dipole iron is a dipole iron with upper and lower symmetrical edge angles on the outlet side, specifically: the beam inlet side is a straight line, the beam outlet side is a pair of upper and lower symmetrical inclined lines, the inclination direction of the upper and lower symmetrical inclined lines is the direction of beam bending at the outlet side; the upper and lower symmetrical inclined lines and the center of the circle of the beam bending track to the line connecting the beams at the outlet of the dipole iron form the edge angle of the outlet side of the dipole iron; by optimizing the size of the edge angle of the dipole iron, using the focusing effect of the edge field of the dipole iron, and cooperating with the envelopes of the four-octupole composite iron on the two sides of the dipole iron in the Y direction and the envelopes in the X direction, an ideal phase shift meeting the homogenization requirement is obtained; The ultra-short straight line type beam homogenization transmission line comprises two four-octupole composite irons; the straight line type beam homogenization transmission line is sequentially provided with an accelerator outlet, a beam matching mechanism, a four-octupole composite iron A, a four-octupole composite iron B, a beam homogenization effect observation mechanism, and a terminal along a beam direction; The ultra-short bending type beam homogenization transmission line comprises two four-octupole composite irons and a dipole iron; the ultra-short bending type beam homogenization transmission line is an ultra-short bending type beam homogenization transmission line A arranged along a beam direction or an ultra-short bending type beam homogenization transmission line B arranged along a beam direction; the ultra-short bending type beam homogenization transmission line A is sequentially provided with an accelerator outlet, a beam matching mechanism, a four-octupole composite iron A, a dipole iron, a four-octupole composite iron B, a beam matching and homogenization effect observation mechanism A, and a terminal A along a beam extraction direction; the ultra-short bending type beam homogenization transmission line B is sequentially provided with an accelerator outlet, a beam matching mechanism, a four-octupole composite iron A, a dipole iron, a four-octupole composite iron C, a beam matching and homogenization effect observation mechanism B, and a terminal B along a beam extraction direction; The ultra-short symmetrical bending type beam homogenization transmission line comprises two four-octupole composite irons and a shared dipole iron; the ultra-short symmetrical bending type beam homogenization transmission line comprises a shared beam line and two branch beam lines; The ultra-short straight line bending composite type beam homogenization transmission line comprises a straight line type beam homogenization transmission line comprising two four-octupole composite irons and a bending type beam homogenization transmission line comprising two four-octupole composite irons and a dipole iron; the straight line type beam homogenization transmission line and the bending type beam homogenization transmission line comprise a shared transmission line and two branch transmission lines. The super-short bending type beam homogenization structure, the super-short bending type beam homogenization transmission line, the super-short symmetric bending type beam homogenization transmission line, and the super-short straight-bending composite type beam homogenization transmission line utilize the focusing effect of the four-octupole composite iron A and the dipole iron to superimpose the beam waist in the Y direction near the four-octupole composite iron B or the four-octupole composite iron C; and utilize the four-pole field superposition of the dipole iron and the four-octupole composite iron B or the dipole iron and the four-octupole composite iron C to superimpose the envelope size in the X direction on the target, so that the envelope sizes in the X direction and the Y direction are consistent. The super-short straight linear beam homogenization structure, the super-short bending type beam homogenization structure, a super-short straight linear beam homogenization transmission line, a super-short bending type beam homogenization transmission line, a super-short straight bending composite beam homogenization transmission line, and a super-short symmetric bending type beam homogenization transmission line, wherein the Y direction or X direction beam envelope function reaches a larger value at the first four-octupole composite magnet, and the X direction or Y direction beam envelope function reaches a larger value at the second four-octupole composite magnet; the phase shift of particles between the two four-octupole composite magnets and the target Respectively close to integer multiples of 180 degrees; the transmission matrix between the two octupole magnetic fields is close to the unit matrix.

2. The super-short beam homogenization transmission line system based on the four-octupole composite magnet according to claim 1, characterized in that: The super-short bending type beam homogenization structure is sequentially provided with the four-octupole composite iron A, the dipole iron, the four-octupole composite iron B and / or the four-octupole composite iron C along the beam direction; the dipole iron is used to change the beam direction of the beam line from a straight line type to a bending type; the four-octupole composite iron A, the four-octupole composite iron B and / or the four-octupole composite iron C are used to generate a quadrupole magnetic field and an octupole magnetic field, respectively, so that the functions of the quadrupole iron and the octupole iron can be simultaneously realized by installing only one transmission element; the bending type beam homogenization substructure is provided with the four-octupole composite iron A upstream of the dipole iron and the four-octupole composite iron B or the four-octupole composite iron C downstream of the dipole iron; the symmetric bending type beam homogenization substructure includes a symmetric first bending type beam homogenization structure and a symmetric second bending type beam homogenization structure; the symmetric first bending type beam homogenization structure is provided with the four-octupole composite iron A upstream of the dipole iron and the four-octupole composite iron B downstream of the dipole iron; the symmetric second bending type beam homogenization structure is provided with the four-octupole composite iron A upstream of the dipole iron and the four-octupole composite iron C downstream of the dipole iron; the symmetric first bending type beam homogenization structure and the symmetric second bending type beam homogenization structure work at different times; the dipole iron on the symmetric bending type beam homogenization transmission line based on the symmetric bending type beam homogenization substructure is a common dipole iron on the super-short symmetric bending type beam homogenization transmission line, and the common dipole iron is a dipole iron with upper and lower symmetric edge angles at the outlet edge, specifically: the beam inlet edge is a straight line, the beam outlet edge is a pair of upper and lower symmetric inclined lines, the inclination direction of the upper and lower symmetric inclined lines is the bending direction of the beam at the outlet edge, the upper and lower symmetric inclined lines and the line from the center of the beam bending track to the beam at the outlet edge of the dipole iron form the 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 envelope in the Y direction and the envelope in the X direction 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. This ultra-short, straight-line, curved-type composite beam homogenization transmission line has the following components along the beam direction: an accelerator outlet, a beam matching mechanism, a four-eight-pole composite iron A, and a four-eight-pole composite iron B; wherein, when the four-eight-pole composite iron B is applied to the curved-type branch transmission line, it only has a four-pole field and not an eight-pole field; the two branch transmission lines are a straight-line branch transmission line and a curved-type branch transmission line; the straight-line branch transmission line has a beam homogenization effect observation mechanism and a terminal; the curved-type branch transmission line has a two-pole iron, a four-eight-pole composite magnet C, a beam matching and homogenization effect observation mechanism, and a terminal; the common transmission line is equipped with: an accelerator outlet, a beam matching mechanism, a four-eight-pole composite magnet A, a beam matching and homogenization effect observation mechanism, and a terminal; A composite linear beam homogenization transmission line is formed by combining a transmission line and the linear branch transmission line; a composite curved beam homogenization transmission line is formed by combining a common transmission line and the curved branch transmission line; the composite linear beam homogenization transmission line and the composite curved beam homogenization transmission line operate in a time-division manner; the four-eight-pole composite iron A and four-eight-pole composite iron B of the composite linear beam homogenization transmission line and the four-eight-pole composite iron A and four-eight-pole composite iron C of the composite curved beam homogenization transmission line simultaneously generate a quadrupole magnetic field and an octupole magnetic field, respectively, so that the functions of a quadrupole iron and an octupole iron can be realized simultaneously by installing only one transmission element; The common beamline of this ultra-short symmetrical bend-type beam homogenization transmission line is arranged along the beam direction as follows: an accelerator outlet, a beam matching mechanism, a quad-octet composite iron A, and a diode; the two branch beamlines are a first branch beamline and a second branch beamline; the first branch beamline is arranged with a quad-octet composite iron B, a beam matching and homogenization effect observation mechanism A, and a terminal A; the second branch beamline is arranged with a quad-octet composite iron C, a beam matching and homogenization effect observation mechanism B, and a terminal B; the common beamline and the first branch beamline form a first bend-type beam homogenization transmission line; the common beamline and the second branch beamline form 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; the first bend-type beam homogenization transmission line and the second bend-type beam homogenization transmission line... The four-eight-pole composite iron A, four-eight-pole composite iron B, and four-eight-pole composite iron C of the homogenization transmission line simultaneously generate a quadrupole magnetic field and an octupole magnetic field, respectively, so that only one transmission element is needed to achieve the functions of both quadrupole and octupole irons. The shared dipole iron is a dipole iron that satisfies the homogenization of the symmetrically bent beam. The dipole iron has a vertically symmetrical straight edge at the entrance side of the symmetrically bent beam and a vertically symmetrical inclined edge at the exit side of the symmetrically bent beam. The inclination direction of the symmetrical inclined edge is the direction of beam bending. The vertically symmetrical inclined line and the line connecting the center of the beam bending track to the beam at the exit of the dipole iron form the dipole iron exit edge angle. By changing the size of the dipole iron exit edge angle, the edge field focusing effect of the dipole iron is adjusted, and in conjunction with the envelopes of the four-eight-pole composite irons on both sides of the dipole iron in the Y direction and the X direction, an ideal phase shift that meets the homogenization requirements is obtained.

3. The system of claim 1, wherein the system comprises: a first quadrupole magnet; a second quadrupole magnet; a third quadrupole magnet; and a fourth quadrupole magnet. The eight-pole magnetic field excitation coil of the inner layer of the four-eight-pole compound magnet has two adjacent pole heads with opposite current directions, i.e. the eight-pole field coil is 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, thus generating an eight-pole magnetic field; the four-pole magnetic field excitation coil of the outer layer has two adjacent pole heads with a coil as a group, which is divided into four groups, i.e. 1, 2 pole heads, 3, 4 pole heads, 5, 6 pole heads, and 7, 8 pole heads; wherein, the 1, 2 pole heads and the symmetrically arranged 5, 6 pole heads have the same excitation current size and direction of the two groups of four-pole magnetic field coils, the 3, 4 pole heads and the symmetrically arranged 7, 8 pole heads have the same excitation current size and direction of the two groups of coils, the current directions of the 1, 2 pole heads and the 3, 4 pole heads are opposite, and the current directions of the 5, 6 pole heads and the 7, 8 pole heads are opposite, thus generating a four-pole magnetic field.

4. The system of claim 1, wherein the system comprises: a first quadrupole magnet; a second quadrupole magnet; a third quadrupole magnet; and a fourth quadrupole magnet. The compound magnet current control device of the four-eight-pole compound magnet system 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 four / eight-pole field gradient current curve intersection point solving module, and an output four-pole / eight-pole coil current module; The two-dimensional sampling point module for establishing coil current is used to establish a two-dimensional data table of coil current of the four-pole iron and the eight-pole iron; The experimental measurement preliminary three-dimensional curved surface sample library module for establishing magnetic field gradient is used to perform magnetic field experimental measurement on the compound iron by using the current values of the two-dimensional data table of coil current, so as to obtain four / eight-pole magnetic field gradient measurement values corresponding to the two-dimensional current data table, and thus obtain a three-dimensional curved surface sample database of magnetic field gradient; the three-dimensional curved surface sample database of magnetic field gradient comprises a four-pole field magnetic field gradient three-dimensional curved surface sample database and an eight-pole field magnetic field gradient three-dimensional curved surface sample database; The interpolation refinement three-dimensional curved surface sample library module for using magnetic field gradient is used to perform 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 a cubic spline function, and to encrypt the grid point density; The input field gradient solving corresponding field gradient current curve 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 sample database, and to obtain two corresponding current curves after intersection; specifically, a four-pole field magnetic field gradient plane is selected, the plane intersects the curved surface of the four-pole field magnetic field gradient three-dimensional curved surface sample database, and a current curve satisfying the four-pole field gradient is obtained; an eight-pole field magnetic field gradient plane is selected, the plane intersects the curved surface of the eight-pole field magnetic 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 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 solution of the excitation current of the compound iron. The output quadrupole / octupole coil current module outputs quadrupole field coil current and octupole field coil current to the four-octupole composite magnet according to the solution of the composite iron excitation current.

5. The system of claim 1, wherein the system is a four-pole composite magnet based ultra-short bunch homogenization transmission line system. The particle in the phase shift between the two four-octupole composite magnets and the target of the super-short linear beam homogenization structure, the super-short bending type beam homogenization structure, a super-short linear beam homogenization transmission line, a super-short bending type beam homogenization transmission line, a super-short linear-bending composite beam homogenization transmission line, and a super-short symmetric bending type beam homogenization transmission line Respectively close to 180 degrees of integer multiple, refers to close but not equal to 180 degrees of integer multiple: set As The remainder of 180 degrees, The value is generally less than ± 15 degrees.

6. The system of claim 1, wherein the system comprises: a first quadrupole magnet; a second quadrupole magnet; a third quadrupole magnet; and a fourth quadrupole magnet. The transmission matrix between the two octupole magnetic fields of the super-short linear type beam current homogenization structure, the super-short bending type beam current homogenization structure, the super-short linear type beam current homogenization transmission line, the super-short bending type beam current homogenization transmission line, the super-short linear-bending composite type beam current homogenization transmission line and the super-short symmetric bending type beam current homogenization transmission line is close to a unit matrix, that is, the phase shift between the front and rear two four-octupole composite magnets is controlled within 30 degrees, which can greatly avoid the high-order nonlinear effect caused by the coupling of the two octupole magnets and can obtain better homogenization effect.

7. The system of claim 1, wherein the system further comprises a four-pole composite magnet. The expression of the magnet strength k at the first four-octupole composite magnet and the second four-octupole composite magnet of the super-short linear type beam current homogenization structure, the super-short bending type beam current homogenization structure, the super-short linear type beam current homogenization transmission line, the super-short bending type beam current homogenization transmission line, the super-short linear-bending composite type beam current homogenization transmission line and the super-short symmetric bending type beam current homogenization transmission line is: It is assumed 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 terminal, that is, the position of the target, is 3; ux02 of 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 of the above formula (2) 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; and βy1 represents the envelope function in the y direction at position 1.

8. The system of claim 2, wherein the system is a four-pole composite magnet based ultra-short bunch homogenization transmission line system. When the ultra-short bending type beam homogenization structure uses the bending type beam homogenization substructure or the symmetric first bending type beam homogenization structure, the Y direction or X direction beam envelope function reaches a large value at the four-octupole composite iron A, and the X direction or Y direction beam envelope function reaches a large value at the four-octupole composite iron B; the phase shift of particles between the four-octupole composite iron A and the four-octupole composite iron B and the target respectively close to integer multiples of 180 degrees; the transmission matrix between the two octupole magnetic fields is close to the unit matrix; when the bending type beam homogenization substructure or the symmetric second bending type beam homogenization structure is used, the Y direction or X direction beam envelope function reaches a large value at the four-octupole composite iron A, and the X direction or Y direction beam envelope function reaches a large value at the four-octupole composite iron C; the phase shift of particles between the four-octupole composite iron A and the four-octupole composite iron C and the target respectively close to integer multiples of 180 degrees; the transmission matrix between the two octupole magnetic fields is close to the unit matrix.

9. The system of claim 1, wherein the system comprises: a first quadrupole magnet; a second quadrupole magnet; a third quadrupole magnet; and a fourth quadrupole magnet. The super-short symmetric bending type beam current homogenization transmission line is composed of a common transmission line and two branch transmission lines; the common transmission line is sequentially provided with an accelerator exit, a beam matching mechanism, a four-octupole composite iron A and a diode iron along the beam direction; the common transmission line, the four-octupole composite iron B of the first branch transmission line, the beam matching and homogenization effect observation mechanism A and the terminal A form a first bending type beam current homogenization transmission line; the common transmission line, the four-octupole composite iron C of the second branch transmission line, the beam matching and homogenization effect observation mechanism B and the terminal B form a second bending type beam current homogenization transmission line; the first bending type beam current homogenization transmission line and the second bending type beam current homogenization transmission line work in time division; The one ultra-short symmetrical bending type beam homogenization transmission line is composed of one common transmission line and two branch transmission lines; the common transmission line is sequentially provided with an accelerator exit, a beam matching mechanism, a four-octupole composite iron A and a dipole iron along the beam direction; the common transmission line, the four-octupole composite iron B of the first branch transmission line, a beam matching and homogenization effect observation mechanism A and a terminal A form a first bending type beam homogenization transmission line; the common transmission line, the four-octupole composite iron C of the second branch transmission line, a beam matching and homogenization effect observation mechanism B and a terminal B form a second bending type beam homogenization transmission line; the first bending type beam homogenization transmission line and the second bending type beam homogenization transmission line work in time-sharing mode; the common dipole iron is a dipole iron with upper and lower symmetrical edge angles on the exit side, specifically: the beam inlet side is a straight line, the beam exit side is a pair of upper and lower symmetrical inclined lines, the inclination direction of the upper and lower symmetrical inclined lines is the bending direction of the beam at the exit side; the upper and lower symmetrical inclined lines and the line from the center of the beam bending track to the beam at the exit of the dipole iron form the dipole iron exit edge angle; the edge field focusing effect of the dipole iron is adjusted by changing the size of the dipole iron exit edge angle, and the ideal phase shift meeting the homogenization requirement is obtained by matching the envelopes of the four-octupole composite irons on the two sides of the dipole iron in the Y direction and the envelopes in the X direction.

10. The system of claim 8, wherein the system further comprises a magnetic field generator. The ideal phase shift meeting the homogenization requirement is obtained by optimizing the size of the edge angle of the dipole iron, that is: by adjusting the size of the dipole iron exit edge angle, the phase difference of the first four-octupole composite iron to the target point in the Y direction is close to 180 degrees, the phase difference of the second four-octupole composite iron to the target point in the X direction is close to 0 degrees, the phase difference of the two four-octupole composite irons in the X direction is less than 30 degrees, and the phase difference of the two four-octupole composite irons in the Y direction is less than 30 degrees; The included angle formed by the center of the beam bending track and the line from the beam at the inlet and the exit of the dipole iron is the beam bending angle; in the case of a certain beam bending angle, the larger the dipole iron exit edge angle, the stronger the focusing in the Y direction and the weaker the focusing in the X direction; in the case of a certain beam bending angle, the smaller the dipole iron exit edge angle, the stronger the focusing in the X direction and the weaker the focusing in the Y direction; The edge field focusing effect of the dipole iron is adjusted by changing the size of the dipole iron exit edge angle, and the ideal phase shift meeting the homogenization requirement is obtained by matching the envelopes of the four-octupole composite irons on the two sides of the dipole iron in the Y direction and the envelopes in the X direction, that is: when the homogenization effect needs to enhance the focusing in the Y direction and weaken the focusing in the X direction to obtain the ideal phase shift meeting the homogenization requirement, the dipole iron exit edge angle is increased in the case of a certain beam bending angle; when the homogenization effect needs to weaken the focusing in the Y direction and enhance the focusing in the X direction to obtain the ideal phase shift meeting the homogenization requirement, the dipole iron exit edge angle is decreased in the case of a certain beam bending angle; The adjustable range of the dipole iron exit edge angle is ≥0 degrees and <90 degrees; The adjustable range of the dipole iron exit edge angle is 20 degrees to 60 degrees; For the first bending type beam homogenization transmission line, the dipole iron with upper and lower symmetric edge angles is arranged between the four-octupole composite iron A and the four-octupole composite iron B, and the dipole iron with upper and lower symmetric edge angles on the outlet side of the ultra-short transmission line is used to replace the conventional dipole iron, so that the phase shift matching and beam focusing are realized under the condition of ultra-short transmission line; For the second bending type beam homogenization transmission line, the dipole iron with upper and lower symmetric edge angles is arranged between the four-octupole composite iron A and the four-octupole composite iron C, and the dipole iron with upper and lower symmetric edge angles on the outlet side of the ultra-short transmission line is used to replace the conventional dipole iron, so that the phase shift matching and beam focusing are realized under the condition of ultra-short transmission line.

11. A method for adjusting the excitation current of a quadrupole compound magnet for a quadrupole compound magnet based ultra-short beam uniformity transport line system according to any one of claims 1-10, characterized in that: The method comprises the following steps: Step one, establish a two-dimensional data table of coil current of quadrupole and octupole; the two-dimensional data table of coil current is based on a two-dimensional data table of coil current of four-octupole composite iron; Step two, experimental measurement, obtain four-octupole magnetic field gradient measurement value corresponding to the two-dimensional current data table, so as to obtain a three-dimensional curved surface sample database of magnetic field gradient; the three-dimensional curved surface sample database of magnetic field gradient comprises a four-octupole field magnetic field gradient three-dimensional curved surface sample database and an eight-octupole field magnetic field gradient three-dimensional curved surface sample database; Step three, use cubic spline function to perform two-dimensional interpolation on the four-octupole field magnetic field gradient three-dimensional curved surface sample database and the eight-octupole field magnetic field gradient three-dimensional curved surface sample database, and encrypt the grid point density; Step four, select a four-octupole field magnetic field gradient plane, which intersects with the curved surface of the four-octupole field magnetic field gradient three-dimensional curved surface sample database, to obtain a current curve satisfying the four-octupole field magnetic field gradient; select an eight-octupole field magnetic field gradient plane, which intersects with the curved surface of the eight-octupole field magnetic field gradient three-dimensional curved surface sample database, to obtain a current curve satisfying the eight-octupole field gradient; Step five, obtain the current curve satisfying the four-octupole field gradient and the current curve satisfying the eight-octupole field gradient in the two-dimensional data grid plane of coil current, and finally find the intersection point of the two current curves; Step six, use the intersection point as the solution of the excitation current of the composite iron.

12. A method for adjusting a linear beam homogenization transmission line based on the super short beam homogenization transmission line system based on the quadrupole composite magnet according to any one of claims 1-10, and the method for adjusting the excitation current of the quadrupole composite magnet according to claim 11; characterized in that, The debugging method comprises the following steps: Step one, set the four-octupole field and eight-octupole field current of the quadrupole and two four-octupole composite irons to zero; Step two, observe the change of beam envelope on the fluorescent target, and adjust the four-octupole field current in front of the four-octupole composite iron A, so that the X-direction beam is waist-shaped near the four-octupole composite iron A; Step three, observe the change of beam envelope on the fluorescent target, and adjust the four-octupole field current of the four-octupole composite iron A in front of the four-octupole composite iron B, so that the Y-direction beam is waist-shaped near the four-octupole composite iron B, and the four-octupole field gradient of the four-octupole composite iron A at this time is retained; Step four, adjust the four-octupole field current of the four-octupole composite iron B, so that the X-direction envelope and the Y-direction envelope of the beam on the fluorescent target are consistent, a round beam is obtained, and the four-octupole field gradient of the four-octupole composite iron B at this time is retained; Step five, adjust the octupole field of the quad-octupole A to adjust the uniformity of the beam in Y direction, according to the recorded quad field gradient of the quad-octupole A and the current octupole field gradient of the quad-octupole A, the intersection current that satisfies the quad field gradient and the octupole field gradient of the quad-octupole A at the same time is calculated, and the octupole field gradient of the quad-octupole A at this time is reserved; Step six, if the uniformity of the beam does not change obviously when the octupole field current of the quad-octupole A is adjusted, the quad field gradient of the quad-octupole A needs to be modified for phase shift matching, so that the phase shift of the quad-octupole A to the target in Y direction is close to 180°, that is, according to the adjusted quad field gradient of the quad-octupole A and the reserved octupole field gradient in step five, the intersection current that satisfies the quad field gradient and the octupole field gradient of the quad-octupole A at the same time is calculated; Step seven, adjust the octupole field of the quad-octupole B to adjust the uniformity of the beam in X direction, according to the recorded quad field gradient of the quad-octupole B and the current octupole field gradient of the quad-octupole B, the intersection current that satisfies the quad field gradient and the octupole field gradient of the quad-octupole B at the same time is calculated, and the octupole field gradient of the quad-octupole B at this time is reserved; Step eight, if the uniformity of the beam does not change obviously when the octupole field current of the quad-octupole B is adjusted, the X direction beam envelope at the quad-octupole B needs to be increased.

13. A method for adjusting the bending type beam uniformity transmission line based on the super short beam uniformity transmission line system based on the quadrupole composite magnet according to any one of claims 1-10, and the method is also based on the method for adjusting the excitation current of the quadrupole composite magnet according to claim 11; characterized in that, The method comprises the following steps: Step one, set the quad field and octupole field currents of the quad-octupole and two quad-octupoles to zero; Step two, adjust the diode current so that the center of the beam spot is roughly aligned with the center of the fluorescent target; Step three, observe the change of the beam envelope on the fluorescent target, and adjust the quad field current of the quad-octupole A in front to make the X direction beam waist near the quad-octupole A; Step four, observe the change of the beam envelope on the fluorescent target, and adjust the quad field current of the quad-octupole A in front of the diode, so that the Y direction beam waist near the quad-octupole B is formed under the joint action of the edge field of the diode and the quad field of the quad-octupole A, and the quad field gradient of the quad-octupole A at this time is reserved; Step five, adjust the quad field current of the quad-octupole B so that the X direction envelope of the beam on the fluorescent target is consistent with the Y direction envelope, and a round beam is obtained, and then the diode current is adjusted again to align the center of the beam spot with the center of the target, and the quad field gradient of the quad-octupole B at this time is reserved; Step six, adjust the octupole field of the quad-octupole A to adjust the uniformity of the beam in Y direction, according to the recorded quad field gradient of the quad-octupole A and the current octupole field gradient of the quad-octupole A, the intersection current that satisfies the quad field gradient and the octupole field gradient of the quad-octupole A at the same time is calculated, and the octupole field gradient of the quad-octupole A at this time is reserved; Step seven, adjust the octupole field of the quad-octupole B to adjust the uniformity of the beam in X direction, according to the recorded quad field gradient of the quad-octupole B and the current octupole field gradient of the quad-octupole B, the intersection current that satisfies the quad field gradient and the octupole field gradient of the quad-octupole B at the same time is calculated, and the octupole field gradient of the quad-octupole B at this time is reserved; Step eight, if the uniformity of the beam does not change obviously when the octupole field current of the quad-octupole B is adjusted, the X direction beam envelope at the quad-octupole B needs to be increased. Step seven, if the uniformity of the beam changes is not obvious when adjusting the octupole field current of the quad-octupole compound iron A, the quad-octupole compound iron A needs to be modified to perform phase shift matching on the quadripole field gradient, so that the Y direction phase shift from the quad-octupole compound iron A to the target is close to 180°, that is, according to the adjusted quad-octupole compound iron A quadripole field gradient and the retained octupole field gradient in step six, the intersection point current that satisfies the quad-octupole compound iron A quadripole field gradient and octupole field gradient at the same time is calculated; Step eight, adjust the octupole field of the quad-octupole compound iron B to adjust the uniformity effect of the beam in the X direction, according to the quad-octupole compound iron B quadripole field gradient recorded in step five and the current octupole field gradient of the quad-octupole compound iron B, the intersection point current that satisfies the quad-octupole compound iron B quadripole field gradient and octupole field gradient at the same time is calculated, and the octupole field gradient of the quad-octupole compound iron B at this time is retained; Step nine, if the uniformity of the beam changes is not obvious when adjusting the octupole field current of the quad-octupole compound iron B, the X direction beam envelope at the quad-octupole compound iron B needs to be increased.

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