A wide energy spectrum particle beam transmission and homogenization device and implementation method thereof

Abstract

The present invention discloses a wide energy spectrum particle beam transmission and homogenization device and its implementation method. The present invention adopts a weak focusing magnet, a slit and a guide magnet; the present invention selects the energy range by the position of the slit in the X direction, and selects the passing ratio of each energy particle beam by the opening range of the slit in the Y direction, thereby realizing the shaping energy spectrum; a specially designed guide magnet is arranged at the outlet of the weak focusing magnet, and the shape of the outlet of the guide magnet is obtained according to the divergence angle correction amount and the deflection radius r of the particle, and the divergence angle of each energy particle beam in the X direction is corrected in a targeted manner, so that the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, the limitation of the chromatic aberration effect on the irradiation application of large energy divergence particle beams is overcome, the irradiation application efficiency of the particle beam is improved, and the requirements of irradiation application are met.

Description

Technical Field

[0001] The invention relates to particle beam transmission and laser accelerator application technology, and in particular to a wide energy spectrum particle beam transmission and homogenization device and an implementation method thereof. Background Art

[0002] With the advancement of high-power laser technology, laser plasma acceleration has developed rapidly due to its excellent acceleration structure, increasing the acceleration gradient to the order of 100GV / m. It has now achieved nearly 100 MeV protons and several GeV electron outputs, and is expected to become a new generation of compact, low-cost particle accelerator.

[0003] Laser-driven proton beams have the characteristics of μm-level size (point source), ampere-level peak current, large energy dispersion (~100%), and large dispersion angle, and have broad application prospects. Irradiation applications require that the dose distribution generated by the proton beam at the irradiation terminal is uniform (including transverse and longitudinal directions, the transverse direction includes the horizontal and vertical directions, and the longitudinal direction is the direction of the proton beam's advance), so it is necessary to complete the transformation from a point source to a proton beam with a larger area and uniform dose distribution during transmission. In order to improve the utilization efficiency of the proton beam, the energy dispersion range of the transmission is required to be as large as possible, and the chromatic aberration effect poses a great challenge to the transmission and homogenization of proton beams with large energy dispersion.

[0004] The lateral homogenization of particle beams after transmission includes the homogenization of particle beams with the same energy and different initial divergence angles, as well as the homogenization of particle beams with different energies. The homogenization of particle beams with different energies requires that the sizes of the particle beams after transmission are close, which requires the realization of position achromatism or the reduction of chromatic aberration.

[0005] The longitudinal homogenization of the particle beam after transmission requires that the doses deposited at different depths of the incident beam in the sample are close. This is usually achieved by generating an extended Bragg peak dose platform technology, which requires that the energy spectrum of the particle beam increases with the energy. Laser-driven particle beams usually have an exponentially decreasing energy spectrum, so energy spectrum shaping is required to reduce the number of low-energy particles. This requires accurate energy analysis of the particle beam and setting slits to control the passing ratio of particle beams of each energy.

[0006] Therefore, the transmission and homogenization of wide energy spectrum particle beams require the beamline to have the ability to shape and homogenize the energy spectrum. The weak focusing effect of the constant gradient magnetic field can focus in both the horizontal and vertical directions and analyze the energy in the horizontal direction; the integrated optical characteristics of focusing and energy analysis can achieve achromatism or significantly reduce the influence of chromatic aberration, which has great application value. Summary of the invention

[0007] In view of the requirements of irradiation on the transmission and homogenization of laser-driven particle beams, in order to overcome the adverse effects of chromatic aberration on the application of wide energy spectrum particle beams, the present invention proposes a wide energy spectrum particle beam transmission and homogenization device and an implementation method thereof.

[0008] One object of the present invention is to provide a wide energy spectrum particle beam transmission and homogenization device.

[0009] The particle coordinate system XYZ or the laboratory coordinate system X'Y'Z' is often used to describe the movement of particles. In the particle coordinate system XYZ, the origin of the coordinate system is always at the reference particle; the reference particle is an imaginary particle moving along a predetermined path, and the reference particle moves in the longitudinal direction (Z axis), and the transverse direction includes the horizontal direction (X axis) and the vertical direction (Y axis); in the floating section, the direction of the particle coordinate system remains unchanged, and the origin changes with the reference particle; in the deflection magnet, the Z axis is always tangential, and changes continuously as the reference particle moves forward; the X axis is always radial, and the Y axis remains unchanged; in the laboratory coordinate system X'Y'Z', the direction and origin of the coordinate axis remain unchanged after the coordinate system is selected; in the present invention, the Y axis and the Y' axis have the same direction.

[0010] The dispersion angle of a particle is defined as the ratio of the transverse velocity to the longitudinal velocity in the particle coordinate system. For example, the dispersion angle in the X direction is equal to the velocity v in the X direction. x With longitudinal velocity v z The ratio of, in each floating segment, the dispersion angle of the particles remains unchanged, in the weak focusing magnet, the Z axis is along the tangential direction, the dispersion angle of the reference particles is always zero, but the deflection angle is not zero, while the dispersion angles of other particles change continuously during the deflection, but are not equal to the deflection angle.

[0011] The wide energy spectrum particle beam transmission and homogenization device of the present invention comprises: a weak focusing magnet, a slit and a guide magnet; wherein the weak focusing magnet comprises two pole faces of exactly the same shape, and the projection shape of the pole faces of the weak focusing magnet on the Z'X' plane of the laboratory coordinate system is a partial ring, comprising an upper pole face located in the positive direction of the Y axis and a lower pole face located in the negative direction of the Y axis; the entrance of the weak focusing magnet faces the target point, and there is a distance between the entrance of the weak focusing magnet and the target point to form a first floating section, and the length of the first floating section is L1; the outlet of the weak focusing magnet faces the irradiation terminal, and there is a distance between the outlet of the weak focusing magnet and the irradiation terminal to form a second floating section, and the length of the second floating section is L2; ​​after a set deflection angle in the weak focusing magnet, After deflection, particles with the same energy and different initial divergence angles in the X direction are focused at the image point. The image points of particles with different energies are located at different positions in the X direction. A slit is set at the image point of particles with required energy between the two pole faces of the weak focusing magnet. A guide magnet is set at the exit of the weak focusing magnet. The guide magnet includes two pole faces placed parallel to each other. Each pole face of the guide magnet is parallel to the ZX plane. There is a distance between the two pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y direction. The entrance of the guide magnet is parallel to the exit of the weak focusing magnet. The shape of the exit of the guide magnet is determined by formula (3) in the ZX plane in the particle coordinate system at the exit of the weak focusing magnet, which is expressed as the width increases with the absolute value of the coordinate on the X axis.

[0012] The interaction between the laser pulse and the target generates a micrometer-scale particle beam at the target point. The particle beam has an initial divergence angle in the X and Y directions. The velocity v of the particle in the positive half axis of the X direction in the X direction x are all greater than 0, that is, the dispersion angle of the particle in the positive X direction is positive, and the velocity v of the particle in the negative X direction is xare all less than 0, that is, the dispersion angle of the particle in the X direction is negative, and the X direction is in a defocused state; similarly, the dispersion angle of the particle in the Y direction is positive, and the dispersion angle of the particle in the Y direction is negative, and the Y direction is in a defocused state; the movement in the X and Y directions is independent and does not affect each other; entering the first floating section, the lateral size of the particle beam increases continuously in the first floating section, and the dispersion angle of the particle beam remains unchanged; passing through the first floating section, entering the weak focusing magnet, the weak focusing magnet deflects the particle beam and changes the dispersion angle, the particle has a deflection angle, the deflection radius of particles with different energies is different but the deflection angle is the same, and the deflection radius of particles with large energy is large, so that at the exit of the weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ, and the particles with larger energy dispersion are farther from the center line of the beam line; the particle beam reaches the image point after being deflected by the set deflection angle in the weak focusing magnet, and particles with the same energy and different initial dispersion angles converge in the X direction, and particles with different energies are separated along the X direction; through the slit in the X direction The energy range is selected by the position, and the passing ratio of particles of each energy is selected by the opening range of the slit in the Y direction, so as to realize the shaping energy spectrum; the weak focusing magnet provides focusing force in the X and Y directions, and the change of the divergence angle is determined by the focusing force in the X and Y directions. The focusing force increases with the increase of the deflection angle, and the divergence angle changes continuously at the same time; after being focused by the weak focusing magnet, the particles enter the second floating section, and the divergence angle of the particles with a positive position in the X direction is negative, and the divergence angle of the particles with a negative position in the X direction is positive in the X direction, and they are in a focusing state in the X direction. Similarly, the divergence angle of the particles with a positive position in the Y direction is negative in the Y direction, and the divergence angle of the particles with a negative position in the Y direction is positive in the Y direction, and they are in a focusing state in the Y direction. In the second floating section, the lateral size of the particle beam is continuously reduced, and the distance between the distribution center of each energy particle beam and the center line of the beam line is continuously reduced; the uniformity requirement is that the distribution center of each energy particle beam in the X direction is located on the center line of the beam line at the irradiation terminal; but when the weak focusing magnet is deflected at the same angle, the change of the divergence angle due to the focusing force in the X direction cannot meet the uniformity requirement;

[0013] Using beam transmission dynamics, the relationship that the length L2 of the second floating section needs to satisfy when the particle beam is transmitted to the irradiation terminal to achieve position achromatism in the X direction is obtained:

[0014]

[0015] When the particle deflection radius r, the total deflection angle θ generated by the weak focusing magnet and the magnetic field drop index n are determined, the length L2 of the second floating section is obtained by formula (1);

[0016] In formula (1), the deflection radius r of particles with higher energy is larger. When the total deflection angle θ generated by the weak focusing magnet is the same, the length L2 of the second floating section is required to increase with energy to achieve position achromatism. The length L2 of the second floating section is calculated according to the deflection radius r of the particle with the central energy.c The energy divergence of the particle beam is greater than that of the center beam, and the divergence angle correction value is greater than that of the center beam. The larger the energy divergence, the greater the deviation between the distribution center of the particle beam and the center line of the beam line, resulting in the overall distribution of the particle beam being deformed. The uneven dose distribution makes the particle beam unusable for irradiation. Therefore, a guide magnet is set at the exit of the weak focusing magnet to correct the divergence angle in the X direction, so that the distribution center of each energy particle beam at the irradiation terminal returns to the center line of the beam line. The larger the energy divergence of the particle beam, the greater the divergence angle correction value. The bigger;

[0017] The particle beam corrects the divergence angle in the X direction through the guide magnet and reaches the irradiation terminal through the second floating section;

[0018] Through the beam transmission matrix, the divergence correction value at the weak focusing magnet exit is calculated. for:

[0019]

[0020] x e is the coordinate of the particle on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet, and the origin of the coordinate is located at the center line of the beam line; particles of different energies are separated along the X direction at the exit of the weak focusing magnet, and the greater the energy dispersion, the greater the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The larger the absolute value of As the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The absolute value of increases;

[0021] In the ZX plane of the particle coordinate system at the weak focusing magnet outlet, the shape of the guide magnet close to the boundary of the weak focusing magnet, i.e. the entrance, is a straight line of z=0, and the coordinate of the right boundary, i.e. the exit of the guide magnet, in the ZX plane of the particle coordinate system at the weak focusing magnet outlet is (z e ,x e ) indicates that z e Represents x e The width of the guide magnet in the Z direction is used to calculate the particle deflection radius According to the amount of correction With the particle deflection radius r, the shape of the outlet of the guide magnet satisfies:

[0022]

[0023] (3) Where B sis the magnetic field strength of the guide magnet, which is a known quantity determined artificially, q is the charge of the particle, including protons, ions and electrons, and p0 is the momentum of the central energy particle. Since the guide magnet is at the position z ≥ 0 in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, we take The absolute value of

[0024] Therefore, the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, overcoming the limitation of chromatic aberration effect on the irradiation application of large energy dispersion particle beam and improving the irradiation application efficiency of particle beam.

[0025] The direction of the current determines the direction of the magnetic field. When the current direction of the weak focusing magnet is positive, a proton beam, an ion beam or a positron beam is transmitted; when the current direction is negative, an electron beam is transmitted.

[0026] The particle beams coming out from the target are all transmitted in the pipeline, which is kept in a vacuum, and pass through the gap between the weak focusing magnet and the magnetic pole surface of the guide magnet; and there are no obstacles on the path of the particle beam.

[0027] Achromatization is to make the items related to the position or dispersion angle in the transmission matrix and the chromatic aberration (energy dispersion) equal to 0, so that the position or dispersion angle after transmission is not affected by the chromatic aberration. If there is no position achromatization design, due to the influence of chromatic aberration, particles with the same initial position and dispersion angle but different energies will have different positions when they are transmitted to the irradiation terminal. After adding the position achromatization design, the items related to the position and chromatic aberration in the transmission matrix are equal to 0, which will not affect the position after transmission, that is, the particles with the same initial position and dispersion angle but different energies will still have the same position when they are transmitted to the irradiation terminal.

[0028] Another object of the present invention is to provide a method for realizing a wide energy spectrum particle beam transmission and homogenization device.

[0029] The method for implementing the wide energy spectrum particle beam transmission and homogenization device of the present invention comprises the following steps:

[0030] 1) Wide energy spectrum particle beam transmission and homogenization device settings:

[0031] a) providing a weak focusing magnet, the weak focusing magnet comprising two pole surfaces of identical shape, the projection shape of the pole surface of the weak focusing magnet on the Z'X' plane of the laboratory coordinate system is a partial ring, comprising an upper pole surface located in the positive direction of the Y axis and a lower pole surface located in the negative direction of the Y axis;

[0032] b) the entrance of the weak focusing magnet faces the target point, and there is a distance between the entrance of the weak focusing magnet and the target point to form a first floating section, and the length of the first floating section is L1;

[0033] c) the outlet of the weak focusing magnet faces the irradiation terminal, and there is a distance between the outlet of the weak focusing magnet and the irradiation terminal to form a second floating section, and the length of the second floating section is L2;

[0034] d) After being deflected by a set deflection angle in the weak focusing magnet, particles with the same energy and different initial divergence angles are focused at the image point in the X direction. The image points of particles with different energies are located at different positions in the X direction. A slit is set at the image point of particles with the required energy between the two pole surfaces of the weak focusing magnet;

[0035] e) a guide magnet is arranged at the outlet of the weak focusing magnet, the guide magnet comprises two pole faces placed parallel to each other, each pole face of the guide magnet is parallel to the ZX plane, there is a distance between the two pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y direction, the inlet of the guide magnet is parallel to the outlet of the weak focusing magnet, and the width of the outlet of the guide magnet increases with the absolute value of the coordinate on the X-axis;

[0036] 2) The interaction between the laser pulse and the target generates a micrometer-level particle beam at the target point. The particle beam has an initial divergence angle in the X and Y directions. The velocity v of the particle in the positive half axis of the X direction in the X direction x are all greater than 0, that is, the dispersion angle of the particle in the positive X direction is positive, and the velocity v of the particle in the negative X direction is x are all less than 0, that is, the dispersion angle of the particle in the X direction is negative, and the X direction is in a defocused state; similarly, the dispersion angle of the particle in the Y direction is positive, and the dispersion angle of the particle in the Y direction is negative, and the Y direction is in a defocused state; the movement in the X and Y directions is independent and does not affect each other; entering the first floating section, the lateral size of the particle beam increases continuously in the first floating section, and the dispersion angle of the particle beam remains unchanged; passing through the first floating section, entering the weak focusing magnet, the weak focusing magnet deflects the particle beam and changes the dispersion angle, and the particles have a deflection angle, and the deflection radius of particles with different energies is different but the deflection angle is the same, and the deflection radius of particles with large energy is large, so that at the exit of the weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ, and particles with larger energy dispersion are farther from the center line of the beam line;

[0037] 3) The particle beam reaches the image point after being deflected by a set deflection angle in a weak focusing magnet. Particles with the same energy and different initial divergence angles converge in the X direction, and particles with different energies separate along the X direction. The energy range is selected by the slit position in the X direction, and the passing ratio of particles of each energy is selected by the slit opening range in the Y direction, thereby realizing a shaped energy spectrum.

[0038] 4) The weak focusing magnet provides focusing force in the X and Y directions, and the change in the divergence angle is determined by the focusing force in the X and Y directions. The focusing force increases with the increase of the deflection angle, and the divergence angle changes continuously at the same time; after being focused by the weak focusing magnet, the particles enter the second floating section, and the divergence angle of the particles with a positive position in the X direction is negative, and the divergence angle of the particles with a negative position in the X direction is positive in the X direction, and they are in a focused state in the X direction. Similarly, the divergence angle of the particles with a positive position in the Y direction is negative in the Y direction, and the divergence angle of the particles with a negative position in the Y direction is positive in the Y direction, and they are in a focused state in the Y direction. In the second floating section, the lateral size of the particle beam is continuously reduced, and the distance between the distribution center of each energy particle beam and the center line of the beam line is continuously reduced; the uniformity requirement is that the distribution center of each energy particle beam in the X direction is located on the center line of the beam line at the irradiation terminal; but when the weak focusing magnet is deflected at the same angle, the change in the divergence angle due to the focusing force in the X direction cannot meet the uniformity requirement;

[0039] 5) The particle beam corrects the divergence angle in the X direction through the guide magnet and reaches the irradiation terminal through the second floating section:

[0040] Using beam transmission dynamics, we can obtain the second

[0041] The length L2 of the floating section needs to satisfy the following relationship:

[0042]

[0043] When the deflection radius r of the central energy particle, the total deflection angle θ generated by the weak focusing magnet and the magnetic field drop index n are determined, the length L2 of the second floating section is obtained by formula (1);

[0044] In formula (1), the deflection radius r of particles with higher energy is larger. When the total deflection angle θ generated by the weak focusing magnet is the same, the length L2 of the second floating section is required to increase with energy to achieve position achromatism. The length L2 of the second floating section is calculated according to the deflection radius r of the particle with the central energy. c The energy divergence of the particle beam is greater than that of the center beam, and the divergence angle correction value is greater than that of the center beam. The larger the energy divergence, the greater the deviation between the distribution center of the particle beam and the center line of the beam line, resulting in the overall distribution of the particle beam being deformed. The uneven dose distribution makes the particle beam unusable for irradiation. Therefore, a guide magnet is set at the exit of the weak focusing magnet to correct the divergence angle in the X direction, so that the distribution center of each energy particle beam at the irradiation terminal returns to the center line of the beam line. The larger the energy divergence of the particle beam, the greater the divergence angle correction value. The bigger;

[0045] 6) Through the beam transmission matrix, the divergence correction value at the weak focusing magnet exit is calculated for:

[0046]

[0047] x e is the coordinate of the particle on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet, and the origin of the coordinate is located at the center line of the beam line; particles of different energies are separated along the X direction at the exit of the weak focusing magnet, and the greater the energy dispersion, the greater the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The larger the absolute value of As the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The absolute value of increases;

[0048] In the ZX plane of the particle coordinate system at the weak focusing magnet outlet, the shape of the guide magnet close to the boundary of the weak focusing magnet, i.e. the entrance, is a straight line of z=0, and the coordinate of the right boundary, i.e. the exit of the guide magnet, in the ZX plane of the particle coordinate system at the weak focusing magnet outlet is (z e ,x e ) indicates that z e Represents x e The width of the guide magnet in the Z direction is used to calculate the particle deflection radius According to the amount of correction With the particle deflection radius r, the shape of the outlet of the guide magnet satisfies:

[0049]

[0050] (3) Where B s is the magnetic field strength of the guide magnet, which is a known quantity determined artificially, q is the charge of the particle, and p0 is the momentum of the central energy particle. Since the guide magnet is at the position z ≥ 0 in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, we take The absolute value of

[0051] Therefore, the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, overcoming the limitation of chromatic aberration effect on the irradiation application of large energy dispersion particle beam and improving the irradiation application efficiency of particle beam.

[0052] Advantages of the present invention:

[0053] The particle beam output by the laser accelerator has a large energy dispersion (chromatic aberration). Due to the influence of the chromatic aberration effect, the particles deviate from the center line of the beam line as a whole in the X direction after position achromatic transmission. The larger the energy dispersion, the larger the offset, resulting in distribution deformity and uneven dose distribution, affecting the irradiation application. The present invention sets a specially designed guide magnet at the outlet of the weak focusing magnet to specifically correct the divergence angle of each energy particle beam in the X direction, so that the particle beam at the application end returns to the center line of the beam line as a whole, ensuring the uniformity of dose distribution and meeting the requirements of irradiation application. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A schematic diagram of an embodiment of a wide energy spectrum particle beam transmission and homogenization device of the present invention;

[0055] Figure 2 This is a schematic diagram of a guide magnet in the ZX plane of an embodiment of the wide energy spectrum particle beam transmission and homogenization device of the present invention. DETAILED DESCRIPTION

[0056] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0057] In the particle coordinate system XYZ, the origin of the coordinate system is always at the reference particle; the reference particle is an imaginary particle moving along a predetermined path, the forward direction of the reference particle is longitudinal (Z axis), and the transverse direction includes the horizontal direction (X axis) and the vertical direction (Y axis); in the floating section, the direction of the particle coordinate system remains unchanged, and the origin changes with the reference particle; in the deflection magnet, the Z axis is always tangential and changes continuously with the forward movement of the reference particle; the X axis is always radial, and the Y axis remains unchanged; in the laboratory coordinate system X'Y'Z', the direction and origin of the coordinate axis remain unchanged after the coordinate system is selected; in the present invention, the direction of the Y axis is the same as that of the Y' axis.

[0058] like Figure 1As shown, the wide energy spectrum particle beam transmission and homogenization device of this embodiment comprises: a weak focusing magnet M and a specially designed guide magnet D; wherein, the entrance of the weak focusing magnet is directly opposite to the target point T, and there is a first floating section between the entrance of the weak focusing magnet and the target point, and the length of the first floating section is L1. The larger L1 is, the larger the envelope of the particle beam after entering the weak focusing magnet, the greater the change of the divergence angle caused by the focusing force in the X and Y directions, and the smaller the size of the particle beam at the irradiation terminal; there is a second floating section between the exit of the weak focusing magnet and the irradiation terminal P, and the length of the second floating section is L2; ​​after being deflected by a set deflection angle φ in the weak focusing magnet, the particles with the same energy and different initial divergence angles in the X direction are uniformly distributed. Particles with different angles are focused at the image point, and the image points of particles with different energies are at different positions in the X direction. A slit is set at the image point of particles with the required energy between the two pole faces of the weak focusing magnet; the set deflection angle φ is determined by the length L1 of the first floating section, the deflection radius r and the magnetic field drop index n, which are calculated by the transmission matrix; a guide magnet is set at the outlet of the weak focusing magnet, and the guide magnet includes two pole faces placed parallel to each other, each pole face of the guide magnet is parallel to the ZX plane, and there is a distance between the two pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y direction, and the inlet of the guide magnet is parallel to the outlet of the weak focusing magnet. A guide magnet is set at the outlet of the weak focusing magnet. The particle beams B coming out of the target point T are all transmitted in the pipeline G, which is kept in a vacuum, and pass through the gap between the magnetic pole faces of the weak focusing magnet and the guide magnet to reach the irradiation terminal P; and no obstacles are set on the path of the particle beam.

[0059] In order to reduce the influence of chromatic aberration, a special guide magnet is designed at the outlet of the weak focusing magnet, taking advantage of the fact that particles of different energies are separated along the X direction at the outlet of the weak focusing magnet, such as Figure 1 As shown, the shape of the guide magnet is Figure 2 As shown, the divergence angle of each energy particle beam in the X direction is corrected in a targeted manner through the guide magnet, so that the particle beam at the application end returns to the center line of the beam line as a whole, ensuring the uniformity of dose distribution.

[0060] The magnetic field of the guide magnet is a uniform magnetic field. In the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, the shape of the boundary of the guide magnet close to the weak focusing magnet, i.e. the entrance, is a straight line with z=0. The coordinates of the right boundary, i.e. the exit of the guide magnet, in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet are (z e ,x e ) indicates that z e Represents the position x in the X direction e The width of the guide magnet in the Z direction is adjusted according to the divergence correction value. With the deflection radius, the shape of the guide magnet outlet is obtained, such as Figure 2 As shown:

[0061]

[0062] In this embodiment, a 12 MeV proton beam is transmitted, the deflection radius of the weak focusing magnet is designed to be 0.5 m, the total deflection angle θ generated by the weak focusing magnet is 4.703 rad, the magnetic field drop index n is 0.17, and the magnetic field strength B of the guide magnet is s 1T, L1 = 0.25m, L2 = 0.853m. A circular hole-shaped divergence selection slit is set at the entrance of the weak focusing magnet to select the proton beam within the divergence angle of ±50mrad; the proton beam reaches the image point in the X direction after being deflected by 2.98rad in the weak focusing magnet, and a slit S is set at the image point in the weak focusing magnet to select the energy range, such as 90% energy divergence; for irradiation applications, the energy spectrum is shaped at the slit to reduce the number of low-energy protons.

[0063] A beam diagnostic device may be added to the first floating section or the second floating section to measure proton beam parameters.

[0064] The current direction of the weak focusing magnet and the guide magnet determines the magnetic field direction of the weak focusing magnet and the guide magnet. When the current direction changes, the magnetic field direction changes. When the current direction of the weak focusing magnet and the guide magnet is positive, a proton beam, an ion beam or a positron beam is transmitted; when the current direction is negative, an electron beam is transmitted.

[0065] The implementation method of the wide energy spectrum particle beam transmission and homogenization device of this embodiment includes the following steps:

[0066] 1) Wide energy spectrum particle beam transmission and homogenization device settings, such as Figure 1 As shown;

[0067] 2) The interaction between the laser pulse and the target generates a micrometer-level particle beam at the target point. The particle beam has an initial divergence angle in the X and Y directions. The velocity v of the particle in the positive half axis of the X direction in the X direction x are all greater than 0, that is, the dispersion angle of the particle in the positive X direction is positive, and the velocity v of the particle in the negative X direction is x are all less than 0, that is, the dispersion angle of the particle in the X direction is negative, and the X direction is in a defocused state; similarly, the dispersion angle of the particle in the Y direction is positive, and the dispersion angle of the particle in the Y direction is negative, and the Y direction is in a defocused state; the movement in the X and Y directions is independent and does not affect each other; entering the first floating section, the lateral size of the particle beam increases continuously in the first floating section; passing through the first floating section, entering the weak focusing magnet, the weak focusing magnet deflects the particle beam and changes the dispersion angle, and the particles have a deflection angle. The deflection radius of particles with different energies is different but the deflection angle is the same. The deflection radius of particles with large energy is large, so at the exit of the weak focusing magnet, different

[0068] The particles with higher energy are separated along the X direction of the particle coordinate system XYZ, and the particles with higher energy dispersion are farther away from the center line of the beam;

[0069] 3) The particle beam reaches the image point after being deflected by a set deflection angle in a weak focusing magnet. Particles with the same energy and different initial divergence angles converge in the X direction, and particles with different energies separate along the X direction. The energy range is selected by the slit position in the X direction, and the passing ratio of particles of each energy is selected by the slit opening range in the Y direction, thereby realizing a shaped energy spectrum.

[0070] 4) The particle beam corrects the divergence angle in the X direction through the guide magnet and reaches the irradiation terminal through the second floating section:

[0071] Using beam transmission dynamics, the relationship that the length L2 of the second floating section needs to satisfy when the particle beam is transmitted to the irradiation terminal to achieve position achromatism in the X direction is obtained:

[0072]

[0073] When the deflection radius r of the central energy particle, the total deflection angle θ generated by the weak focusing magnet and the magnetic field drop index n are determined, the length L2 of the second floating section is obtained by formula (1);

[0074] In formula (1), the deflection radius r of particles with higher energy is larger. When the total deflection angle θ generated by the weak focusing magnet is the same, the length L2 of the second floating section is required to increase with energy to achieve position achromatism. The length L2 of the second floating section is calculated according to the deflection radius r of the particle with the central energy. c Determine, so that the particle beams with higher and lower energy than the center energy are offset toward the positive direction of the X-axis at the irradiation terminal. The greater the energy spread, the greater the deviation of the distribution center of the particle beam from the center line of the beam line, resulting in the overall distribution of the particle beam being deformed. The uneven dose distribution makes the particle beam unusable for irradiation; in the weak focusing magnet, the particle beam is focused in the Y direction, but the particle beams of different energies are not separated along the Y direction. The distribution center of the particle beams of different energies in the Y direction is always the coordinate origin of the Y axis, while the particle beams of different energies are separated in the X direction. At the exit of the weak focusing magnet, the distribution center of the particle beam with greater energy spread is farther away from the center of the beam line, and the divergence angle of each energy particle beam in the X direction can be corrected in a targeted manner; therefore, a guide magnet is set at the exit of the weak focusing magnet to correct the divergence angle in the X direction, so that the distribution center of each energy particle beam at the irradiation terminal returns to the center line of the beam line; the larger the energy spread of the particle, the greater the divergence angle correction amount The bigger;

[0075] 5) Through the beam transmission matrix, the divergence correction value at the weak focusing magnet exit is calculated for:

[0076]

[0077] x e is the coordinate of the particle on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet, and the origin of the coordinate is located at the center line of the beam line; particles of different energies are separated along the X direction at the exit of the weak focusing magnet, and the greater the energy dispersion, the greater the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The larger the absolute value of As the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The absolute value of increases;

[0078] In the ZX plane of the particle coordinate system at the weak focusing magnet outlet, the shape of the guide magnet close to the boundary of the weak focusing magnet, i.e. the entrance, is a straight line of z=0, and the coordinate of the right boundary, i.e. the exit of the guide magnet, in the ZX plane of the particle coordinate system at the weak focusing magnet outlet is (z e ,x e ) indicates that z e Represents x e The width of the guide magnet in the Z direction is used to calculate the particle deflection radius According to the amount of correction With the particle deflection radius r, the shape of the outlet of the guide magnet satisfies:

[0079]

[0080] (3) Where B s is the magnetic field strength of the guide magnet, which is a known quantity determined artificially, q is the charge of the particle, including protons, ions and electrons, and p0 is the momentum of the central energy particle; since the guide magnet is designed to be at a position z ≥ 0 in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, The absolute value of

[0081] Therefore, the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, overcoming the limitation of chromatic aberration effect on the irradiation application of large energy dispersion particle beam and improving the irradiation application efficiency of particle beam.

[0082] It can be seen from this embodiment that the present invention can achieve precise energy selection, energy spectrum shaping and beam homogenization of large energy dispersion and large divergence angle particle beams in a compact space, and significantly improve the irradiation application efficiency of laser-driven particle beams.

[0083] 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 wide energy spectrum particle beam transmission and homogenization device, in which, in the particle coordinate system XYZ, the origin of the coordinate system is always at the reference particle; the reference particle is an imaginary particle moving along a predetermined path, the forward direction of the reference particle is the Z axis, and the lateral direction includes the horizontal X axis and the vertical Y axis; in the floating section, the direction of the particle coordinate system remains unchanged, and the origin changes with the reference particle; in the deflection magnet, the Z axis is always tangential, and changes continuously with the forward movement of the reference particle; the X axis is always radial, and the Y axis remains unchanged; in the laboratory coordinate system X'Y'Z', the direction and origin of the coordinate axis remain unchanged after the coordinate system is selected, and in the wide energy spectrum particle beam transmission and homogenization device, the directions of the Y axis and the Y' axis are the same, characterized in that The wide energy spectrum particle beam transmission and homogenization device comprises: a weak focusing magnet, a slit and a guide magnet; wherein the weak focusing magnet comprises two pole faces of exactly the same shape, and the projection shape of the pole faces of the weak focusing magnet on the Z'X' plane of the laboratory coordinate system is a partial ring, including an upper pole face located in the positive direction of the Y axis and a lower pole face located in the negative direction of the Y axis; the entrance of the weak focusing magnet faces the target point, and there is a distance between the entrance of the weak focusing magnet and the target point to form a first floating section, and the length of the first floating section is L1; the outlet of the weak focusing magnet faces the irradiation terminal, and there is a distance between the outlet of the weak focusing magnet and the irradiation terminal to form a second floating section, and the length of the second floating section is L2; ​​the weak focusing magnet is deflected at a set deflection angle in the weak focusing magnet. After rotation, particles with the same energy and different initial divergence angles in the X direction are focused at the image point. The image points of particles with different energies are located at different positions in the X direction. A slit is set at the image point of particles with the required energy between the two pole faces of the weak focusing magnet. A guide magnet is set at the exit of the weak focusing magnet. The guide magnet includes two pole faces placed parallel to each other. Each pole face of the guide magnet is parallel to the ZX plane. There is a distance between the two pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y direction. The entrance of the guide magnet is parallel to the exit of the weak focusing magnet. The shape of the exit of the guide magnet is determined by formula (3) in the ZX plane in the particle coordinate system at the exit of the weak focusing magnet, which is expressed as the width increases with the absolute value of the coordinate on the X axis. The interaction between the laser pulse and the target generates a micrometer-scale particle beam at the target point. The particle beam has an initial divergence angle in the X and Y directions. The velocity v of the particle in the positive half axis of the X direction in the X direction x are all greater than 0, that is, the dispersion angle of the particle in the positive X direction is positive, and the velocity v of the particle in the negative X direction is x are all less than 0, that is, the dispersion angle of the particle in the X direction is negative, and the X direction is in a defocused state; similarly, the dispersion angle of the particle in the Y direction is positive, and the dispersion angle of the particle in the Y direction is negative, and the Y direction is in a defocused state; the movement in the X and Y directions is independent and does not affect each other; entering the first floating section, the lateral size of the particle beam increases continuously in the first floating section, and the dispersion angle of the particle beam remains unchanged; passing through the first floating section, entering the weak focusing magnet, the weak focusing magnet deflects the particle beam and changes the dispersion angle, the particle has a deflection angle, the deflection radius of particles with different energies is different but the deflection angle is the same, and the deflection radius of particles with large energy is large, so that at the exit of the weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ, and the particles with larger energy dispersion are farther from the center line of the beam line; the particle beam reaches the image point after being deflected by the set deflection angle in the weak focusing magnet, and particles with the same energy and different initial dispersion angles converge in the X direction, and particles with different energies are separated along the X direction; through the slit in the X direction The energy range is selected by the position, and the passing ratio of particles of each energy is selected by the opening range of the slit in the Y direction, so as to realize the shaping energy spectrum; the weak focusing magnet provides focusing force in the X and Y directions, and the change of the divergence angle is determined by the focusing force in the X and Y directions. The focusing force increases with the increase of the deflection angle, and the divergence angle changes continuously at the same time; after being focused by the weak focusing magnet, the particles enter the second floating section, and the divergence angle of the particles with a positive position in the X direction is negative, and the divergence angle of the particles with a negative position in the X direction is positive in the X direction, and they are in a focusing state in the X direction. Similarly, the divergence angle of the particles with a positive position in the Y direction is negative in the Y direction, and the divergence angle of the particles with a negative position in the Y direction is positive in the Y direction, and they are in a focusing state in the Y direction. In the second floating section, the lateral size of the particle beam is continuously reduced, and the distance between the distribution center of each energy particle beam and the center line of the beam line is continuously reduced; the uniformity requirement is that the distribution center of each energy particle beam in the X direction is located on the center line of the beam line at the irradiation terminal; but when the weak focusing magnet is deflected at the same angle, the change of the divergence angle due to the focusing force in the X direction cannot meet the uniformity requirement; Using beam transmission dynamics, the relationship that the length L2 of the second floating section needs to satisfy when the particle beam is transmitted to the irradiation terminal to achieve position achromatism in the X direction is obtained: When the particle deflection radius r, the total deflection angle θ generated by the weak focusing magnet and the magnetic field drop index n are determined, the length L2 of the second floating section is obtained by formula (1); In formula (1), the deflection radius r of particles with higher energy is larger. When the total deflection angle θ generated by the weak focusing magnet is the same, the length L2 of the second floating section is required to increase with energy to achieve position achromatism. The length L2 of the second floating section is calculated according to the deflection radius r of the particle with the central energy. c The energy divergence of the particle beam is greater than that of the center beam, and the divergence angle correction value is greater than that of the center beam. The larger the energy divergence, the greater the deviation between the distribution center of the particle beam and the center line of the beam line, resulting in the overall distribution of the particle beam being deformed. The uneven dose distribution makes the particle beam unusable for irradiation. Therefore, a guide magnet is set at the exit of the weak focusing magnet to correct the divergence angle in the X direction, so that the distribution center of each energy particle beam at the irradiation terminal returns to the center line of the beam line. The larger the energy divergence of the particle beam, the greater the divergence angle correction value. The bigger; The particle beam corrects the divergence angle in the X direction through the guide magnet and reaches the irradiation terminal through the second floating section; Through the beam transmission matrix, the divergence correction value at the weak focusing magnet exit is calculated. for: x e is the coordinate of the particle on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet, and the origin of the coordinate is located at the center line of the beam line; particles of different energies are separated along the X direction at the exit of the weak focusing magnet, and the greater the energy dispersion, the greater the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The larger the absolute value of As the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The absolute value of increases; In the ZX plane of the particle coordinate system at the weak focusing magnet outlet, the shape of the guide magnet close to the boundary of the weak focusing magnet, i.e. the entrance, is a straight line of z=0, and the coordinate of the right boundary, i.e. the exit of the guide magnet, in the ZX plane of the particle coordinate system at the weak focusing magnet outlet is (z e ,x e ) indicates that z e Represents x e The width of the guide magnet in the Z direction is used to calculate the particle deflection radius According to the amount of correction With the particle deflection radius r, the shape of the outlet of the guide magnet satisfies: (3) Where B s is the magnetic field strength of the guide magnet, r c is the deflection radius of the central energy particle, q is the charge of the particle, and p0 is the momentum of the central energy particle; since the guide magnet is designed to be at a position z ≥ 0 in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, The absolute value of Therefore, the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, overcoming the limitation of chromatic aberration effect on the irradiation application of large energy dispersion particle beam and improving the irradiation application efficiency of particle beam.

2. The wide energy spectrum particle beam transmission and homogenization device according to claim 1, characterized in that: The direction of the current determines the direction of the magnetic field. When the current direction of the weak focusing magnet is positive, a proton beam, an ion beam or a positron beam is transmitted; when the current direction is negative, an electron beam is transmitted.

3. The wide energy spectrum particle beam transmission and homogenization device according to claim 1, characterized in that: The particle beams coming out from the target are all transmitted in the pipeline, which is kept in a vacuum, and pass through the gap between the weak focusing magnet and the magnetic pole surface of the guide magnet; and there are no obstacles on the path of the particle beam.

4. The wide energy spectrum particle beam transmission and homogenization device according to claim 1, characterized in that: It also includes a beam diagnostic device, which is arranged in the first floating section or the second floating section and is used to measure proton beam parameters.

5. A method for implementing the wide energy spectrum particle beam transmission and homogenization device as claimed in claim 1, characterized in that: The implementation method comprises the following steps: 1) Wide energy spectrum particle beam transmission and homogenization device settings: a) providing a weak focusing magnet, the weak focusing magnet comprising two pole surfaces of identical shape, the projection shape of the pole surfaces of the weak focusing magnet on the Z'X' plane of the laboratory coordinate system is a partial ring, comprising an upper pole surface located in the positive direction of the Y axis and a lower pole surface located in the negative direction of the Y axis; b) the entrance of the weak focusing magnet faces the target point, and there is a distance between the entrance of the weak focusing magnet and the target point to form a first floating section, and the length of the first floating section is L1; c) the outlet of the weak focusing magnet faces the irradiation terminal, and there is a distance between the outlet of the weak focusing magnet and the irradiation terminal to form a second floating section, and the length of the second floating section is L2; d) After being deflected by a set deflection angle in the weak focusing magnet, particles with the same energy and different initial divergence angles are focused at the image point in the X direction. The image points of particles with different energies are located at different positions in the X direction. A slit is set at the image point of particles with the required energy between the two pole surfaces of the weak focusing magnet; e) a guide magnet is arranged at the weak focusing magnet outlet, the guide magnet comprises two pole faces placed parallel to each other, each pole face of the guide magnet is parallel to the ZX plane, there is a distance between the two pole faces of the guide magnet, which are respectively located in the positive direction and the negative direction of the Y direction, the inlet of the guide magnet is parallel to the outlet of the weak focusing magnet, and the width of the guide magnet outlet increases with the absolute value of the coordinate on the X-axis; 2) The interaction between the laser pulse and the target generates a micrometer-level particle beam at the target point. The particle beam has an initial divergence angle in the X and Y directions. The velocity v of the particle in the positive half axis of the X direction in the X direction x are all greater than 0, that is, the dispersion angle of the particle in the positive X direction is positive, and the velocity v of the particle in the negative X direction is x are all less than 0, that is, the dispersion angle of the particle in the X direction is negative, and the X direction is in a defocused state; similarly, the dispersion angle of the particle in the Y direction is positive, and the dispersion angle of the particle in the Y direction is negative, and the Y direction is in a defocused state; the movements in the X and Y directions are independent and do not affect each other; entering the first floating section, the lateral size of the particle beam increases continuously in the first floating section, and the dispersion angle of the particle beam remains unchanged; passing through the first floating section, entering the weak focusing magnet, the weak focusing magnet deflects the particle beam and changes the dispersion angle, and the particles have a deflection angle, and the deflection radius of particles with different energies is different but the deflection angle is the same, and the deflection radius of particles with large energy is large, so that at the exit of the weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ, and particles with larger energy dispersion are farther from the center line of the beam line; 3) The particle beam reaches the image point after being deflected by a set deflection angle in a weak focusing magnet. Particles with the same energy and different initial divergence angles converge in the X direction, and particles with different energies separate along the X direction. The energy range is selected by the slit position in the X direction, and the passing ratio of particles of each energy is selected by the slit opening range in the Y direction, thereby realizing a shaped energy spectrum. 4) The weak focusing magnet provides focusing force in the X and Y directions. The change in the divergence angle is determined by the focusing force in the X and Y directions. The focusing force increases with the increase of the deflection angle, and the divergence angle changes continuously. After being focused by the weak focusing magnet, the particles enter the second floating section. The divergence angle of the particles with a positive position in the X direction is negative, and the divergence angle of the particles with a negative position in the X direction is positive in the X direction, and they are in a focused state in the X direction. Similarly, the divergence angle of the particles with a positive position in the Y direction is negative, and the divergence angle of the particles with a negative position in the Y direction is positive in the Y direction, and they are in a focused state in the Y direction. In the second floating section, the lateral size of the particle beam is continuously reduced, and the distance between the distribution center of each energy particle beam and the center line of the beam line is continuously reduced. The uniformity requires that the distribution center of each energy particle beam in the X direction is located on the center line of the beam line at the irradiation terminal. However, when the weak focusing magnet is deflected at the same angle, the change in the divergence angle due to the focusing force in the X direction cannot meet the uniformity requirement. 5) The particle beam corrects the divergence angle in the X direction through the guide magnet and reaches the irradiation terminal through the second floating section: Using beam transmission dynamics, the relationship that the length L2 of the second floating section needs to satisfy when the particle beam is transmitted to the irradiation terminal to achieve position achromatism in the X direction is obtained: When the deflection radius r of the central energy particle, the total deflection angle θ generated by the weak focusing magnet and the magnetic field drop index n are determined, the length L2 of the second floating section is obtained by formula (1); In formula (1), the deflection radius r of particles with higher energy is larger. When the total deflection angle θ generated by the weak focusing magnet is the same, the length L2 of the second floating section is required to increase with energy to achieve position achromatism. The length L2 of the second floating section is calculated according to the deflection radius r of the particle with the central energy. c The energy divergence of the particle beam is greater than that of the center beam, and the divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The divergence angle of the particle beam is greater than that of the center beam. The bigger; 6) Through the beam transmission matrix, the divergence correction value at the weak focusing magnet exit is calculated for: x e is the coordinate of the particle on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet, and the origin of the coordinate is located at the center line of the beam line; particles of different energies are separated along the X direction at the exit of the weak focusing magnet, and the greater the energy dispersion, the greater the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The larger the absolute value of As the coordinate x on the X-axis in the particle coordinate system ZX at the exit of the weak focusing magnet e The absolute value of increases; In the ZX plane of the particle coordinate system at the weak focusing magnet outlet, the shape of the guide magnet close to the boundary of the weak focusing magnet, i.e., the entrance, is a straight line of z=0, and the coordinate of the right boundary, i.e., the exit of the guide magnet, in the ZX plane of the particle coordinate system at the weak focusing magnet outlet is (z e ,x e ) indicates that z e Represents x e The width of the guide magnet in the Z direction is used to calculate the particle deflection radius According to the amount of correction With the particle deflection radius r, the shape of the guide magnet outlet satisfies: (3) Where B s is the magnetic field strength of the guide magnet, r c is the deflection radius of the central energy particle, q is the charge of the particle, and p0 is the momentum of the central energy particle. Since the guide magnet is at the position z ≥ 0 in the ZX plane of the particle coordinate system at the exit of the weak focusing magnet, The absolute value of Therefore, the distribution center of each energy particle at the irradiation terminal is returned to the center line of the beam line through the guide magnet, so that the dose distribution of the entire particle beam is uniform, overcoming the limitation of chromatic aberration effect on the irradiation application of large energy dispersion particle beam and improving the irradiation application efficiency of particle beam.

6. The implementation method according to claim 5, characterized in that: The direction of the current determines the direction of the magnetic field. When the current direction of the weak focusing magnet is positive, a proton beam, an ion beam or a positron beam is transmitted; when the current direction is negative, an electron beam is transmitted.

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