Proton beam transmission and homogenization device based on guide magnet and implementation method thereof

Abstract

The present invention discloses a proton beam transmission and homogenization device based on a guide magnet and an implementation method thereof. The present invention arranges a guide magnet after a sector magnet to separately adjust the focusing of proton beams above the central energy and below the central energy, respectively providing appropriate focusing forces, reducing the envelope of the proton beam in the quadrupole lens after the sector magnet by half, significantly reducing the construction cost of the quadrupole lens, and at the same time overcoming the application obstacle of the proton beam distribution deformity at the irradiation terminal caused by insufficient focusing force of the proton beam above the central energy and excessive focusing force of the proton beam below the central energy in the quadrupole lens after the sector magnet, thereby realizing the homogenized transmission and application of the proton beam.

Description

Technical Field

[0001] The invention relates to proton beam transmission and laser accelerator application technology, and in particular to a proton beam transmission and homogenization device based on a guide magnet and a realization method thereof. Background Art

[0002] The laser plasma effect can increase the acceleration gradient to the order of 100GV / m. Nearly 100MeV protons and severalGeV electrons have been output, and it is expected to become a new generation of compact, low-cost accelerator used in multiple fields.

[0003] Laser-driven proton beams have the characteristics of μm-level size, large energy dispersion (~100%), and large divergence angle, and have broad application prospects, including isotope production, proton photography, biological irradiation, etc. Due to the instability of laser plasma action, the energy, energy dispersion, and charge of the proton beam generated have certain fluctuations. It is necessary to use a beam line to transmit the proton beam to the application end, diagnose and control the energy, energy dispersion, and charge of the proton beam during the transmission process, shape the energy spectrum, and regulate the spatial distribution of the proton beam to ensure the uniformity of the dose distribution at the application end. This requires the transmission beam line of the laser-driven proton beam to have functions such as focusing and energy selection.

[0004] The divergence angle of the laser-driven proton beam is usually more than ~100 mrad, and it needs to be collected by a focusing element first. The quadrupole lens composed of quadrupole magnets is the most commonly used focusing element. After being collected by the quadrupole lens, the energy divergence of the proton beam is still large, and it is necessary to use a fan-shaped magnet to analyze the energy, select the energy range, and shape the energy spectrum. Then, the quadrupole lens is used to focus and regulate the spatial distribution of the proton beam and deliver it to the application end.

[0005] Energy selection requires that proton beams of different energies be separated in space, resulting in a larger envelope of the proton beam when it enters the quadrupole lens after the fan-shaped magnet, which increases the manufacturing cost of the quadrupole lens. In addition, the chromatic aberration effect causes the proton beams with higher energies than the center energy in the quadrupole lens after the fan-shaped magnet to have insufficient focusing force, and the proton beams with lower energies than the center energy to have excessive focusing force, causing the proton beam distribution at the application end to be distorted. It is necessary to use technical design to reduce the beam envelope in the quadrupole lens after the fan-shaped magnet and overcome the adverse effects of the chromatic aberration effect on the uniformity of the proton beam distribution. Summary of the invention

[0006] In view of the requirements of laser driven proton beam transmission and application, in order to reduce the beam envelope in the quadrupole lens after the fan magnet and overcome the adverse effect of chromatic aberration on the uniformity of proton beam distribution, the present invention proposes a proton beam transmission and homogenization device based on a guide magnet and an implementation method thereof.

[0007] In the laser target chamber, the laser pulse interacts with the target to produce a proton beam on the micron scale. The point of action between the laser pulse and the target is called the target point. The laser target chamber is a vacuum environment, and the proton beam is transmitted along the pipeline after it is generated.

[0008] One object of the present invention is to provide a proton beam transport and homogenization device based on a guide magnet.

[0009] The proton beam transmission and homogenization device based on the guide magnet of the present invention comprises: a first quadrupole lens, a fan-shaped magnet, a guide magnet, and a second quadrupole lens in sequence along the advancing direction of the proton beam; wherein, in the coordinate system XYZ, the X axis represents the horizontal direction, the Y axis represents the vertical direction, and the Z axis points to the advancing direction of the proton beam, which is the longitudinal direction; the first quadrupole lens and the second quadrupole lens are both along the Z direction; the magnetic field direction of the fan-shaped magnet is along the Y direction; the entrance of the first quadrupole lens is directly facing the target point; the exit of the second quadrupole lens is directly facing the irradiation terminal; there is a first quadrupole lens between the entrance of the first quadrupole lens and the target point. a floating section, the length of the first floating section is L1; a second floating section is provided between the exit of the first quadrupole lens and the entrance of the sector magnet, the length of the second floating section is L2; ​​a third floating section is provided between the exit of the sector magnet and the image point of the proton beam with central energy after deflection by the sector magnet, the length of the third floating section is L3; a fourth floating section is provided between the image point of the proton beam with central energy after deflection by the sector magnet and the entrance of the second quadrupole lens, the length of the fourth floating section is L4; a fifth floating section is provided between the exit of the second quadrupole lens and the irradiation terminal, the length of the fifth floating section is L5;

[0010] The laser pulse interacts with the target to generate a micron-scale proton beam at the target point, which enters the first quadrupole lens through the first floating section, and the first quadrupole lens focuses the proton beam; after passing through the second floating section, the proton beam enters the fan-shaped magnet, and the fan-shaped magnet deflects the proton beam. The deflection radius of proton beams with different energies is different, and the deflection radius of proton beams with large energy is large, and the deflection radius of proton beams with small energy is small; after passing through the third floating section, the proton beams with different energies are separated along the X direction;

[0011] Proton beams of the same energy but different initial divergence angles converge at an image point after being deflected by a sector magnet; under the influence of the chromatic aberration effect, the image points of proton beams of different energies after being deflected by the sector magnet are at different positions on the X-axis and the Z-axis in the ZX plane; after being deflected by the sector magnet, the image point of the proton beam with the central energy is located on the X-axis, the image point of the proton beam with higher energy than the central energy is located on the positive half axis of the X-axis, and the image point of the proton beam with lower energy than the central energy is located on the negative half axis of the X-axis, and the image point of the proton beam with higher energy has a larger value on the Z-axis; guide magnets are arranged along the image points of proton beams of different energies in the ZX plane; the guide magnets include two identical magnetic pole faces placed parallel to each other, each magnetic pole face of the guide magnets is parallel to the ZX plane, and there is a distance between the two magnetic pole faces of the guide magnets, which are respectively located in the positive direction and the negative direction of the Y-axis; each magnetic pole face of the guide magnets includes a first triangle and a second triangle, and the first and second triangles have The first and second triangles have a common vertex and are placed opposite to each other, and are located at the positive semi-axis and the negative semi-axis of the X-axis respectively. The projection of the common vertex on the ZX plane at Y=0 is the origin of the coordinate system XYZ at the image point of the proton beam of central energy after being deflected by the fan-shaped magnet; the first side of the first and second triangles is the entrance side, the second side is the exit side, and the third side is parallel to the Z-axis. The straight line slopes of the entrance side and the exit side of the first triangle located at the positive semi-axis of the X-axis are k1 and k2 respectively, and the straight line slopes of the entrance side and the exit side of the second triangle located at the negative semi-axis of the X-axis are k3 and k4 respectively; the angle bisectors of the vertex angles of the first triangle and the second triangle are along the image points of the proton beams of different energies in the ZX plane, and the image points of the proton beams of different energies in the ZX plane are in the guide magnet; the magnetic field in the guide magnet is a uniform magnetic field, the direction of the magnetic field in the first triangle is along the positive semi-axis of the Y-axis, and the direction of the magnetic field in the second triangle is along the negative semi-axis of the Y-axis;

[0012] After being deflected by the fan-shaped magnet, the proton beam reaches the guide magnet. The proton beam with a larger energy dispersion has a larger absolute value of its position in the X direction, is farther from the beam line centerline, passes through a larger magnetic field area in the guide magnet, and is subjected to a greater focusing force. By adjusting the linear slopes k1 and k2 of the entrance and exit edges of the first triangle and the magnetic field strength of the guide magnet, the distribution center of the proton beam with energy higher than the central energy in the X direction at the irradiation terminal is located at the origin of the X axis. In addition, by adjusting the linear slopes k3 and k4 of the entrance and exit edges of the second triangle and the magnetic field strength of the guide magnet, the distribution center of the proton beam with energy lower than the central energy in the X direction at the irradiation terminal is located at the origin of the X axis. The guide magnet has no effect on the transmission in the Y direction.

[0013] The proton beam passes through the fourth floating section and reaches the second quadrupole lens, and the second quadrupole lens focuses the proton beam, and the proton beam passes through the fifth floating section and reaches the irradiation terminal; the focusing of proton beams with energy higher than the center energy and lower than the center energy are adjusted separately, so as to overcome the obstacle that the focusing force of the proton beams higher than the center energy and the focusing force of the proton beams lower than the center energy in the second quadrupole lens after the fan-shaped magnet are insufficient and excessive, resulting in the deformed distribution of the proton beams at the irradiation terminal when there is no guide magnet, so as to achieve the uniformity of the proton beam, and at the same time significantly reduce the proton beam envelope in the second quadrupole lens, thereby reducing the construction cost.

[0014] Furthermore, it also includes a slit, which is set at the entrance or exit of the guide magnet; the energy range is selected by adjusting the position of the slit in the X direction; and the passing ratio of proton beams of various energies is selected by adjusting the width of the slit in the Y direction, thereby shaping the energy spectrum.

[0015] The proton beams coming out from the target are all transmitted in the pipe, which is kept in a vacuum and passes through the gap between the magnetic pole faces; and there are no obstacles on the path of the proton beam.

[0016] The first quadrupole lens adopts an N-element quadrupole lens, including N quadrupole magnets along the Z direction; the second quadrupole lens adopts an R-element quadrupole lens, including R quadrupole magnets along the Z direction, N is a natural number ≥3, and R is a natural number ≥2.

[0017] The larger the length L1 of the first floating section, the larger the size of the proton beam when entering the first quadrupole lens, and the larger the envelope of the proton beam in the first quadrupole lens, 0.1m≤L1≤0.3m; the length L2 of the second floating section includes the floating length required for the proton beam of central energy to reach the focusing point after being focused by the first quadrupole lens and the floating length before entering the sector magnet, and the value range is 3m≤L2≤4m; the length L3 of the third floating section is the floating distance required when the proton beam of central energy leaves the sector magnet and reaches the image point, and the value range is 1.3m≤L3≤1.8m; the length L4 of the fourth floating section provides space for the guide magnet, and the value range is 0.7m≤L4≤0.9m; the length L5 of the fifth floating section provides space for the proton beam to meet application requirements, and the value range is 0.5m≤L5≤1.5m.

[0018] The linear slope k1 of the entrance edge of the first triangle ranges from 0.11 to 0.17, and the linear slope k2 of the exit edge of the first triangle ranges from 0.07 to 0.12; the linear slope k3 of the entrance edge of the second triangle ranges from 0.1 to 0.14, and the linear slope k4 of the exit edge of the second triangle ranges from 0.2 to 0.3.

[0019] Another object of the present invention is to provide a method for realizing a proton beam transmission and homogenization device based on a guide magnet.

[0020] The method for implementing the proton beam transmission and homogenization device based on the guide magnet of the present invention comprises the following steps:

[0021] 1) Device settings:

[0022] The system includes: a first quadrupole lens, a fan-shaped magnet, a guide magnet, and a second quadrupole lens in the direction of the proton beam; wherein, in the coordinate system XYZ, the X axis represents the horizontal direction, the Y axis represents the vertical direction, and the Z axis points to the direction of the proton beam, which is the longitudinal direction; the first quadrupole lens and the second quadrupole lens are both along the Z direction; the magnetic field direction of the fan-shaped magnet is along the Y direction; the entrance of the first quadrupole lens faces the target point; the exit of the second quadrupole lens faces the irradiation terminal; there is a first floating section between the entrance of the first quadrupole lens and the target point, and the first floating section The length is L1; there is a second floating section between the exit of the first quadrupole lens and the entrance of the sector magnet, and the length of the second floating section is L2; ​​there is a third floating section between the exit of the sector magnet and the image point of the proton beam of central energy after deflection by the sector magnet, and the length of the third floating section is L3; there is a fourth floating section between the image point of the proton beam of central energy after deflection by the sector magnet and the entrance of the second quadrupole lens, and the length of the fourth floating section is L4; there is a fifth floating section between the exit of the second quadrupole lens and the irradiation terminal, and the length of the fifth floating section is L5;

[0023] 2) Design guide magnet:

[0024] A guide magnet is arranged along the image point of the proton beam with different energies in the ZX plane; the guide magnet comprises two identical magnetic pole faces placed parallel to each other, each magnetic pole face of the guide magnet is parallel to the ZX plane, and there is a distance between the two magnetic pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y axis; each magnetic pole face of the guide magnet comprises a first triangle and a second triangle, the first and second triangles have a common vertex and are placed opposite to each other, and are respectively located in the positive semi-axis and the negative semi-axis of the X axis, and the projection of the common vertex on the ZX plane at Y=0 is the origin of the coordinate system XYZ at the image point of the proton beam with the central energy after being deflected by the fan-shaped magnet; the first and second triangles The first side is the entrance side, the second side is the exit side, and the third side is parallel to the Z axis. The straight line slopes of the entrance side and exit side of the first triangle located on the positive half axis of the X axis are k1 and k2 respectively, and the straight line slopes of the entrance side and exit side of the second triangle located on the negative half axis of the X axis are k3 and k4 respectively; the angle bisectors of the vertex angles of the first triangle and the second triangle are along the image points of the proton beams of different energies in the ZX plane, and the image points of the proton beams of different energies in the ZX plane are in the guide magnet; the magnetic field in the guide magnet is a uniform magnetic field, the direction of the magnetic field in the first triangle is along the positive half axis of the Y axis, and the direction of the magnetic field in the second triangle is along the negative half axis of the Y axis;

[0025] 3) The laser pulse interacts with the target to generate a micron-level proton beam at the target point, which passes through the first floating section and enters the first quadrupole lens, which focuses the proton beam; after passing through the second floating section, the proton beam enters the fan-shaped magnet, which deflects the proton beam. The deflection radius of proton beams with different energies is different, and the deflection radius of proton beams with large energy is large, while the deflection radius of proton beams with small energy is small; after passing through the third floating section, the proton beams with different energies are separated along the X direction;

[0026] 4) Proton beams of the same energy but different initial divergence angles converge at an image point after being deflected by a sector magnet; under the influence of the chromatic aberration effect, the image points of proton beams of different energies after being deflected by a sector magnet have different positions on the X-axis and the Z-axis in the ZX plane; after being deflected by a sector magnet, the image point of the proton beam with the center energy is located on the X-axis, the image point of the proton beam with higher energy than the center energy is located on the positive half axis of the X-axis, and the image point of the proton beam with lower energy than the center energy is located on the negative half axis of the X-axis. The higher the energy of the proton beam, the larger the value of the position of the image point on the Z-axis.

[0027] 5) After being deflected by the fan-shaped magnet, the proton beam reaches the guide magnet. The proton beam with a larger energy dispersion has a larger absolute value of its position in the X direction, is farther from the beam line centerline, and passes through a larger magnetic field area in the guide magnet, and is subject to a greater focusing force. By adjusting the magnetic field strength of the guide magnet, the distribution center of the proton beam with higher energy than the center energy in the X direction at the irradiation terminal is located at the origin of the X axis. In addition, by adjusting the magnetic field strength of the guide magnet, the distribution center of the proton beam with lower energy than the center energy in the X direction at the irradiation terminal is located at the origin of the X axis. The guide magnet has no effect on the transmission in the Y direction.

[0028] 6) The proton beam passes through the fourth floating section and reaches the second quadrupole lens, and the second quadrupole lens focuses the proton beam. The proton beam passes through the fifth floating section and reaches the irradiation terminal; the focusing of proton beams with energy higher than the center energy and lower than the center energy are adjusted separately, so as to overcome the obstacle that the focusing force of the proton beams higher than the center energy and the focusing force of the proton beams lower than the center energy in the second quadrupole lens after the fan-shaped magnet when there is no guide magnet, resulting in the deformed distribution of the proton beams at the irradiation terminal, thereby achieving the uniformity of the proton beam, and significantly reducing the proton beam envelope in the second quadrupole lens, thereby reducing the construction cost.

[0029] Among them, in step 2), under a certain magnetic field strength, the straight line slope k1 of the entrance side of the first triangle increases and the straight line slope k2 of the exit side of the first triangle decreases, the magnetic field area through which the proton beam with energy higher than the center passes becomes larger, the resulting focusing force becomes stronger, and it shifts toward the negative direction of the X-axis when arriving at the irradiation terminal; and, under a certain magnetic field strength, the straight line slope k3 of the entrance side of the second triangle decreases and the straight line slope k4 of the exit side of the second triangle increases, the magnetic field area through which the proton beam with energy lower than the center passes becomes larger, the resulting focusing force becomes stronger, and it shifts toward the positive direction of the X-axis when arriving at the irradiation terminal.

[0030] In step 5), the magnetic field strength of the guide magnet is adjusted by adjusting the intensity of the current. Adjustment of the proton beam with energy higher than the center: When the linear slopes k1 and k2 of the entrance and exit sides of the first triangle are determined, the magnetic field strength increases, the focusing force obtained by the proton beam with energy higher than the center becomes stronger, and it shifts toward the negative direction of the X-axis when it reaches the irradiation terminal. Adjustment of the proton beam with energy lower than the center: When the linear slopes k3 and k4 of the entrance and exit sides of the second triangle are determined, the magnetic field strength of the proton beam with energy lower than the center increases, the focusing force obtained becomes stronger, and it shifts toward the positive direction of the X-axis when it reaches the irradiation terminal.

[0031] Advantages of the present invention:

[0032] The present invention arranges a guide magnet behind the sector magnet to provide appropriate focusing force for proton beams with energy higher than the center energy and energy lower than the center energy, reduces the proton beam envelope in the quadrupole lens behind the sector magnet by half, significantly reduces the construction cost of the quadrupole lens, and overcomes the application obstacle of deformed proton beam distribution at the irradiation terminal due to insufficient focusing force for proton beams with energy higher than the center energy and excessive focusing force for proton beams with energy lower than the center energy in the quadrupole lens behind the sector magnet, thereby realizing uniform transmission and application of proton beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of an embodiment of a proton beam transport and homogenization device based on a guide magnet of the present invention;

[0034] Figure 2 It is a schematic diagram of the guide magnet in the ZX plane of the coordinate system XYZ at the image point of the proton beam of central energy after being deflected by the fan-shaped magnet in the proton beam transmission and homogenization device based on the guide magnet of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0036] like Figure 1As shown, the proton beam transmission and homogenization device based on the guide magnet of this embodiment includes: a first quadrupole lens, a fan-shaped magnet B, a guide magnet D and a second quadrupole lens in sequence along the forward direction of the proton beam; wherein, in the coordinate system XYZ, the X axis represents the horizontal direction, the Y axis represents the vertical direction, and the Z axis points to the forward direction of the proton beam, which is the longitudinal direction; the first quadrupole lens adopts a three-element quadrupole lens including the first, second and third quadrupole magnets Q1, Q2 and Q3 along the Z direction; the second quadrupole lens adopts a two-element quadrupole lens including the fourth and fifth quadrupole magnets Q4 and Q5 along the Z direction; the magnetic field direction of the fan-shaped magnet B is along the Y direction; the entrance of the first quadrupole lens is directly opposite to the target point T; the exit of the second quadrupole lens is directly opposite to the irradiation terminal; there is a first floating section between the entrance of the first quadrupole lens and the target point T, and the length of the first floating section L1=0.2m; the first quadrupole lens There is a second floating section between the exit of the lens and the entrance of the sector magnet B, and the length of the second floating section is L2=3.57m; there is a third floating section between the exit of the sector magnet B and the image point of the proton beam with central energy after deflection by the sector magnet B, and the length of the third floating section is L3=1.57m; there is a fourth floating section between the image point M of the proton beam with central energy after deflection by the sector magnet B and the entrance of the second quadrupole lens, and the length of the fourth floating section is L4=0.8m; there is a fifth floating section between the exit of the second quadrupole lens and the irradiation terminal P, and the length of the fifth floating section is L5=1m; the proton beams coming out of the target point T are all transmitted in the pipeline G, and the pipeline is kept in vacuum, and the proton beam envelope E passes through the gap between the magnetic pole surfaces of the ternary quadrupole lens, the sector magnet B, the guide magnet D and the binary quadrupole lens to reach the irradiation terminal P; and no obstacles are set on the path of the proton beam.

[0037] In this embodiment, when transmitting a 20 MeV proton beam, the magnetic field strength of the guide magnet D is 0.15 T, and the boundary slopes k1 = 0.148, k2 = 0.092, k3 = 0.12, and k4 = 0.242. Figure 1 The proton beam envelope E in the figure includes the transmission envelopes in the X and Y directions. The transmission envelope of the proton beam with a divergence of 10% and a divergence angle of 100 mrad in the X direction is represented by a solid line, and the transmission envelope in the Y direction is represented by a dotted line. After auxiliary focusing by the guide magnet D, the envelope of the proton beam in the binary quadrupole lens after the fan magnet B is significantly reduced, and the distribution uniformity at the irradiation terminal is improved.

[0038] The implementation method of the proton beam transmission and homogenization device based on the guide magnet D of this embodiment includes the following steps:

[0039] 1) Device settings such as Figure 1 As shown;

[0040] 2) Design guide magnet D:

[0041] like Figure 2As shown, a guide magnet D is arranged along the image point of the proton beam of different energies in the ZX plane; the guide magnet D includes two identical pole faces placed parallel to each other, each pole face of the guide magnet D is parallel to the ZX plane, and there is a distance between the two pole faces of the guide magnet D, which are respectively located in the positive direction and the negative direction of the Y axis; each pole face of the guide magnet D includes a first triangle and a second triangle, the first and second triangles have a common vertex and are placed opposite to each other, and are respectively located in the positive semi-axis and the negative semi-axis of the X axis, and the projection of the common vertex on the ZX plane at Y=0 is O, O coincides with M, and O is the origin of the coordinate system XYZ at the image point of the proton beam of central energy after being deflected by the fan-shaped magnet B; the first side of the first and second triangles is the entrance side, the second side is the exit side, and the third side is parallel to the Z axis, the straight line slopes of the entrance side and the exit side of the first triangle located at the positive semi-axis of the X axis are k1 and k2 respectively, and the straight line slopes of the entrance side and the exit side of the second triangle located at the negative semi-axis of the X axis are respectively

[0042] k3 and k4; under a certain magnetic field strength, the linear slope k1 of the entrance side of the first triangle increases and the linear slope k2 of the exit side of the first triangle decreases, the magnetic field area through which the proton beam with energy higher than the center passes becomes larger, the resulting focusing force becomes stronger, and it deviates to the negative direction of the X-axis when reaching the irradiation terminal; and, under a certain magnetic field strength, the linear slope k3 of the entrance side of the second triangle decreases and the linear slope k4 of the exit side of the second triangle increases, the magnetic field area through which the proton beam with energy lower than the center passes becomes larger, the resulting focusing force becomes stronger, and it deviates to the positive direction of the X-axis when reaching the irradiation terminal; the angular bisectors of the vertex angles of the first triangle and the second triangle are along the image points of the proton beams of different energies in the ZX plane, and the image points of the proton beams of different energies in the ZX plane are in the guide magnet D; the magnetic field in the guide magnet D is a uniform magnetic field, the direction of the magnetic field in the first triangle is along the positive half axis of the Y axis, and the direction of the magnetic field in the second triangle is along the negative half axis of the Y axis;

[0043] 3) The laser pulse interacts with the target to generate a micron-scale proton beam at the target point, which passes through the first floating section and enters the first quadrupole lens, which focuses the proton beam; after passing through the second floating section, the proton beam enters the fan-shaped magnet B, which deflects the proton beam. The deflection radius of proton beams with different energies is different, and the deflection radius of proton beams with large energy is large, while the deflection radius of proton beams with small energy is small; after passing through the third floating section, the proton beams with different energies are separated along the X direction of the coordinate system XYZ;

[0044] 4) Proton beams of the same energy but different initial divergence angles converge at an image point after being deflected by the sector magnet B; under the influence of the chromatic aberration effect, the image points of proton beams of different energies after being deflected by the sector magnet B have different positions on the X-axis and the Z-axis in the ZX plane; after being deflected by the sector magnet B, the image point M of the proton beam with the center energy is located on the X-axis, the image point of the proton beam with higher energy than the center energy is located on the positive half axis of the X-axis, and the image point of the proton beam with lower energy than the center energy is located on the negative half axis of the X-axis. The higher the energy of the proton beam, the larger the value of the position of the image point on the Z-axis.

[0045] 5) After being deflected by the fan-shaped magnet B, the proton beam reaches the guide magnet D. The proton beam with a larger energy dispersion has a larger absolute value of its position in the X direction, is farther from the center line of the beam line, and passes through a larger magnetic field area in the guide magnet D, resulting in a greater focusing force. By adjusting the intensity of the current, the magnetic field intensity of the guide magnet D is adjusted. When the slopes k1 and k2 of the straight lines at the entrance and exit sides of the first triangle are determined, the magnetic field intensity increases, and the focusing force obtained by the proton beam with energy higher than the center energy becomes stronger, and deviates toward the negative direction of the X axis when reaching the irradiation terminal. The proton beam with higher energy than the center is shifted so that the distribution center of the proton beam in the X direction at the irradiation terminal is located at the origin of the X axis; and, by adjusting the magnetic field strength of the guide magnet D, when the straight line slopes k3 and k4 of the entrance side and the exit side of the second triangle are determined, the magnetic field strength of the proton beam with lower energy than the center is increased, the obtained focusing force becomes stronger, and it shifts toward the positive direction of the X axis when reaching the irradiation terminal, so that the distribution center of the proton beam with lower energy than the center is located at the origin of the X axis at the irradiation terminal; the guide magnet D has no effect on the transmission in the Y direction;

[0046] 6) The proton beam passes through the fourth floating section and reaches the second quadrupole lens, and the second quadrupole lens focuses the proton beam. The proton beam passes through the fifth floating section and reaches the irradiation terminal; the focusing of the proton beams above the central energy and below the central energy are adjusted separately, so as to overcome the obstacle that the focusing force of the proton beams above the central energy is insufficient and the focusing force of the proton beams below the central energy is too large in the second quadrupole lens after the fan-shaped magnet B when there is no guide magnet D, resulting in the proton beam distribution at the irradiation terminal being deformed, so as to achieve the uniformity of the proton beam and significantly reduce the proton beam envelope in the second quadrupole lens.

[0047] Reduce construction costs.

[0048] Finally, it should be noted that the purpose of publishing the embodiments is to help further understand the present invention, but those skilled in the art can understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the embodiments, and the scope of protection claimed by the present invention shall be subject to the scope defined in the claims.

Claims

1. A proton beam transmission and homogenization device based on a guide magnet, wherein in a laser target chamber, a laser pulse interacts with a target to generate a micrometer-level proton beam, and the point of action of the laser pulse and the target is called a target point; the laser target chamber is a vacuum environment, and the proton beam is transmitted along a pipeline after being generated; the pipeline is kept vacuum, and the proton beam passes through the magnetic pole surface gap of the proton beam transmission and homogenization device based on a guide magnet to reach the irradiation terminal, and no obstacles are set on the path of the proton beam, characterized in that: The proton beam transmission and homogenization device based on the guide magnet includes: a first quadrupole lens, a fan-shaped magnet, a guide magnet, and a second quadrupole lens in sequence along the forward direction of the proton beam; wherein, in the coordinate system XYZ, the X axis represents the horizontal direction, the Y axis represents the vertical direction, and the Z axis points to the forward direction of the proton beam, which is the longitudinal direction; the first quadrupole lens and the second quadrupole lens are both along the Z direction; the magnetic field direction of the fan-shaped magnet is along the Y direction; the entrance of the first quadrupole lens is directly facing the target point; the exit of the second quadrupole lens is directly facing the irradiation terminal; there is a first A floating section, the length of the first floating section is L1; a second floating section is provided between the exit of the first quadrupole lens and the entrance of the sector magnet, the length of the second floating section is L2; ​​a third floating section is provided between the exit of the sector magnet and the image point of the proton beam with central energy after deflection by the sector magnet, the length of the third floating section is L3; a fourth floating section is provided between the image point of the proton beam with central energy after deflection by the sector magnet and the entrance of the second quadrupole lens, the length of the fourth floating section is L4; a fifth floating section is provided between the exit of the second quadrupole lens and the irradiation terminal, the length of the fifth floating section is L5; The laser pulse interacts with the target to generate a micron-scale proton beam at the target point, which enters the first quadrupole lens through the first floating section, and the first quadrupole lens focuses the proton beam; after passing through the second floating section, the proton beam enters the fan-shaped magnet, and the fan-shaped magnet deflects the proton beam. The deflection radius of proton beams with different energies is different, and the deflection radius of proton beams with large energy is large, and the deflection radius of proton beams with small energy is small; after passing through the third floating section, the proton beams with different energies are separated along the X direction; Proton beams of the same energy but different initial divergence angles converge at an image point after being deflected by a sector magnet; under the influence of the chromatic aberration effect, the image points of proton beams of different energies after being deflected by the sector magnet are at different positions on the X-axis and the Z-axis in the ZX plane; after being deflected by the sector magnet, the image point of the proton beam with the central energy is located on the X-axis, the image point of the proton beam with higher energy than the central energy is located on the positive half axis of the X-axis, and the image point of the proton beam with lower energy than the central energy is located on the negative half axis of the X-axis, and the image point of the proton beam with higher energy has a larger value on the Z-axis; guide magnets are arranged along the image points of proton beams of different energies in the ZX plane; the guide magnets include two identical magnetic pole faces placed parallel to each other, each magnetic pole face of the guide magnets is parallel to the ZX plane, and there is a distance between the two magnetic pole faces of the guide magnets, which are respectively located in the positive direction and the negative direction of the Y-axis; each magnetic pole face of the guide magnets includes a first triangle and a second triangle, and the first and second triangles have The first and second triangles have a common vertex and are placed opposite to each other, and are located at the positive semi-axis and the negative semi-axis of the X-axis respectively. The projection of the common vertex on the ZX plane at Y=0 is the origin of the coordinate system XYZ at the image point of the proton beam of central energy after being deflected by the fan-shaped magnet; the first side of the first and second triangles is the entrance side, the second side is the exit side, and the third side is parallel to the Z-axis. The straight line slopes of the entrance side and the exit side of the first triangle located at the positive semi-axis of the X-axis are k1 and k2 respectively, and the straight line slopes of the entrance side and the exit side of the second triangle located at the negative semi-axis of the X-axis are k3 and k4 respectively; the angle bisectors of the vertex angles of the first triangle and the second triangle are along the image points of the proton beams of different energies in the ZX plane, and the image points of the proton beams of different energies in the ZX plane are in the guide magnet; the magnetic field in the guide magnet is a uniform magnetic field, the direction of the magnetic field in the first triangle is along the positive semi-axis of the Y-axis, and the direction of the magnetic field in the second triangle is along the negative semi-axis of the Y-axis; After being deflected by the fan-shaped magnet, the proton beam reaches the guide magnet. The proton beam with a larger energy dispersion has a larger absolute value of its position in the X direction, is farther from the beam line centerline, passes through a larger magnetic field area in the guide magnet, and is subjected to a greater focusing force. By adjusting the linear slopes k1 and k2 of the entrance and exit edges of the first triangle and the magnetic field strength of the guide magnet, the distribution center of the proton beam with energy higher than the central energy in the X direction at the irradiation terminal is located at the origin of the X axis. In addition, by adjusting the linear slopes k3 and k4 of the entrance and exit edges of the second triangle and the magnetic field strength of the guide magnet, the distribution center of the proton beam with energy lower than the central energy in the X direction at the irradiation terminal is located at the origin of the X axis. The guide magnet has no effect on the transmission in the Y direction. The proton beam passes through the fourth floating section and reaches the second quadrupole lens, and the second quadrupole lens focuses the proton beam, and the proton beam passes through the fifth floating section and reaches the irradiation terminal; the focusing of proton beams with energy higher than the center energy and lower than the center energy are adjusted separately, so as to overcome the obstacle that the focusing force of the proton beams higher than the center energy and the focusing force of the proton beams lower than the center energy in the second quadrupole lens after the fan-shaped magnet are insufficient and excessive, resulting in the deformed distribution of the proton beams at the irradiation terminal when there is no guide magnet, so as to achieve the uniformity of the proton beam, and at the same time significantly reduce the proton beam envelope in the second quadrupole lens, thereby reducing the construction cost.

2. The proton beam transmission and homogenization device based on a guide magnet according to claim 1, characterized in that: It also includes a slit, which is arranged at the entrance or exit of the guide magnet; the energy range is selected by adjusting the position of the slit in the X direction; and the passing ratio of proton beams of various energies is selected by adjusting the width of the slit in the Y direction, thereby shaping the energy spectrum.

3. The proton beam transmission and homogenization device based on a guide magnet according to claim 1, characterized in that: The first quadrupole lens adopts an N-element quadrupole lens, including N quadrupole magnets along the Z direction, where N is a natural number ≥3.

4. The proton beam transmission and homogenization device based on a guide magnet according to claim 1, characterized in that: The second quadrupole lens adopts an R-element quadrupole lens, which includes R quadrupole magnets along the Z direction, where R is a natural number ≥2.

5. The proton beam transmission and homogenization device based on a guide magnet according to claim 1, characterized in that: The larger the length L1 of the first floating section, the larger the size of the proton beam when entering the first quadrupole lens, and the larger the envelope of the proton beam in the first quadrupole lens, 0.1m≤L1≤0.3m; the length L2 of the second floating section includes the floating length required for the proton beam of central energy to reach the focusing point after being focused by the first quadrupole lens and the floating length before entering the fan-shaped magnet, 3m≤L2≤4m; the length L3 of the third floating section is the floating distance required for the proton beam of central energy to leave the fan-shaped magnet and reach the image point, 1.3m≤L3≤1.8m; the length L4 of the fourth floating section provides space for the guide magnet, 0.7m≤L4≤0.9m; the length L5 of the fifth floating section provides space for the proton beam to meet application requirements, 0.5m≤L5≤1.5m.

6. The proton beam transmission and homogenization device based on a guide magnet according to claim 1, characterized in that: The linear slope k1 of the entrance edge of the first triangle ranges from 0.11 to 0.17, and the linear slope k2 of the exit edge of the first triangle ranges from 0.07 to 0.12; the linear slope k3 of the entrance edge of the second triangle ranges from 0.1 to 0.14, and the linear slope k4 of the exit edge of the second triangle ranges from 0.2 to 0.

3.

7. A method for implementing the proton beam transmission and homogenization device based on a guide magnet as claimed in claim 1, characterized in that: The implementation method comprises the following steps: 1) Device settings: The system includes: a first quadrupole lens, a fan-shaped magnet, a guide magnet, and a second quadrupole lens in the direction of the proton beam; wherein, in the coordinate system XYZ, the X axis represents the horizontal direction, the Y axis represents the vertical direction, and the Z axis points to the direction of the proton beam, which is the longitudinal direction; the first quadrupole lens and the second quadrupole lens are both along the Z direction; the magnetic field direction of the fan-shaped magnet is along the Y direction; the entrance of the first quadrupole lens faces the target point; the exit of the second quadrupole lens faces the irradiation terminal; there is a first floating section between the entrance of the first quadrupole lens and the target point, and the first floating section The length is L1; there is a second floating section between the exit of the first quadrupole lens and the entrance of the sector magnet, and the length of the second floating section is L2; ​​there is a third floating section between the exit of the sector magnet and the image point of the proton beam of central energy after deflection by the sector magnet, and the length of the third floating section is L3; there is a fourth floating section between the image point of the proton beam of central energy after deflection by the sector magnet and the entrance of the second quadrupole lens, and the length of the fourth floating section is L4; there is a fifth floating section between the exit of the second quadrupole lens and the irradiation terminal, and the length of the fifth floating section is L5; 2) Design guide magnet: A guide magnet is arranged along the image point of the proton beam with different energies in the ZX plane; the guide magnet comprises two identical magnetic pole faces placed parallel to each other, each magnetic pole face of the guide magnet is parallel to the ZX plane, and there is a distance between the two magnetic pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y axis; each magnetic pole face of the guide magnet comprises a first triangle and a second triangle, the first and second triangles have a common vertex and are placed opposite to each other, and are respectively located in the positive semi-axis and the negative semi-axis of the X axis, and the projection of the common vertex on the ZX plane at Y=0 is the origin of the coordinate system XYZ at the image point of the proton beam with the central energy after being deflected by the fan-shaped magnet; the first and second triangles The first side is the entrance side, the second side is the exit side, and the third side is parallel to the Z axis. The straight line slopes of the entrance side and exit side of the first triangle located on the positive half axis of the X axis are k1 and k2 respectively, and the straight line slopes of the entrance side and exit side of the second triangle located on the negative half axis of the X axis are k3 and k4 respectively; the angle bisectors of the vertex angles of the first triangle and the second triangle are along the image points of the proton beams of different energies in the ZX plane, and the image points of the proton beams of different energies in the ZX plane are in the guide magnet; the magnetic field in the guide magnet is a uniform magnetic field, the direction of the magnetic field in the first triangle is along the positive half axis of the Y axis, and the direction of the magnetic field in the second triangle is along the negative half axis of the Y axis; 3) The laser pulse interacts with the target to generate a micron-level proton beam at the target point, which passes through the first floating section and enters the first quadrupole lens, which focuses the proton beam; after passing through the second floating section, the proton beam enters the fan-shaped magnet, which deflects the proton beam. The deflection radius of proton beams with different energies is different, and the deflection radius of proton beams with large energy is large, while the deflection radius of proton beams with small energy is small; after passing through the third floating section, the proton beams with different energies are separated along the X direction; 4) Proton beams of the same energy but different initial divergence angles converge at an image point after being deflected by a sector magnet; under the influence of the chromatic aberration effect, the image points of proton beams of different energies after being deflected by a sector magnet have different positions on the X-axis and the Z-axis in the ZX plane; after being deflected by a sector magnet, the image point of the proton beam with the center energy is located on the X-axis, the image point of the proton beam with higher energy than the center energy is located on the positive half axis of the X-axis, and the image point of the proton beam with lower energy than the center energy is located on the negative half axis of the X-axis. The higher the energy of the proton beam, the larger the value of the position of the image point on the Z-axis. 5) After being deflected by the fan-shaped magnet, the proton beam reaches the guide magnet. The proton beam with a larger energy dispersion has a larger absolute value of its position in the X direction, is farther from the beam line centerline, and passes through a larger magnetic field area in the guide magnet, and is subject to a greater focusing force. By adjusting the magnetic field strength of the guide magnet, the distribution center of the proton beam with higher energy than the center energy in the X direction at the irradiation terminal is located at the origin of the X axis. In addition, by adjusting the magnetic field strength of the guide magnet, the distribution center of the proton beam with lower energy than the center energy in the X direction at the irradiation terminal is located at the origin of the X axis. The guide magnet has no effect on the transmission in the Y direction. 6) The proton beam passes through the fourth floating section and reaches the second quadrupole lens, and the second quadrupole lens focuses the proton beam. The proton beam passes through the fifth floating section and reaches the irradiation terminal; the focusing of proton beams with energy higher than the center energy and lower than the center energy are adjusted separately, so as to overcome the obstacle that the focusing force of the proton beams higher than the center energy and the focusing force of the proton beams lower than the center energy in the second quadrupole lens after the fan-shaped magnet when there is no guide magnet, resulting in the deformed distribution of the proton beams at the irradiation terminal, thereby achieving the uniformity of the proton beam, and significantly reducing the proton beam envelope in the second quadrupole lens, thereby reducing the construction cost.

8. The implementation method according to claim 7, characterized in that: In step 2), under a certain magnetic field strength, the straight line slope k1 of the entrance side of the first triangle increases and the straight line slope k2 of the exit side of the first triangle decreases, the magnetic field area through which the proton beam with energy higher than the center energy passes becomes larger, the resulting focusing force becomes stronger, and it shifts toward the negative direction of the X-axis when arriving at the irradiation terminal; and, under a certain magnetic field strength, the straight line slope k3 of the entrance side of the second triangle decreases and the straight line slope k4 of the exit side of the second triangle increases, the magnetic field area through which the proton beam with energy lower than the center energy passes becomes larger, the resulting focusing force becomes stronger, and it shifts toward the positive direction of the X-axis when arriving at the irradiation terminal.

9. The implementation method according to claim 7, characterized in that: In step 5), the proton beam with energy higher than the center energy is adjusted: when the straight line slopes k1 and k2 of the entrance and exit sides of the first triangle are determined, the magnetic field strength increases, the focusing force obtained by the proton beam with energy higher than the center energy becomes stronger, and it shifts to the negative direction of the X-axis when reaching the irradiation terminal.

10. The implementation method according to claim 7, characterized in that: In step 5), the proton beam below the center energy is adjusted: when the straight line slopes k3 and k4 of the entrance and exit sides of the second triangle are determined, the magnetic field strength of the proton beam below the center energy increases, the resulting focusing force becomes stronger, and it shifts toward the positive direction of the X-axis when reaching the irradiation terminal.

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