Point-to-point imaging and point-to-parallel imaging beam line transmission device and its implementation method

Abstract

The present invention discloses a point-to-point imaging and point-to-parallel imaging beamline transmission device and its implementation method. In the present invention, a magnet element is arranged in the transmission path. By utilizing the characteristics of the weak focusing magnet that focuses simultaneously in the horizontal direction X and the vertical direction Y and analyzes energy in the X direction, based on the weak focusing effect, double achromatic transmission is realized to eliminate the influence of chromatic aberration effects on the particle beam transmission. A particle beam close to the target size is obtained at the outlet of the double achromatic system, retaining the high brightness characteristics of the laser-driven particle beam, and realizing point-to-point imaging of high energy spread and large divergence angle particle beams; the energy is selected and the energy spectrum is shaped during transmission; in addition, the particles with higher energy travel a longer path to compress the pulse length and retain the short pulse characteristics of the particle beam, meeting the requirements of applications such as warm dense matter research and fast ignition for the spatial and temporal characteristics of the particle beam; point-to-parallel imaging is realized through a triple quadrupole lens to transform the particle beam into a large-area collimated beam, meeting the requirements of applications such as cancer treatment.

Description

Technical Field

[0001] The present invention relates to the technologies of particle beam transmission and laser accelerator applications, and particularly to a point-to-point imaging and point-to-parallel imaging beam line transmission device and an implementation method thereof. Background Art

[0002] After the emergence of ultra-intense lasers, the research under extreme physical conditions achievable by humans has been greatly promoted with extremely high energy density. The interaction of laser with plasma has increased the acceleration gradient to the order of 100 GV / m with a new acceleration mechanism, capable of accelerating ions to ~MeV at the micron scale and electrons to ~GeV at the centimeter scale, and is expected to become a new generation of compact and low-cost acceleration devices applied in many fields.

[0003] The proton beam generated by the interaction of ultra-intense laser with plasma has characteristics such as a small initial beam spot (~10μm), a pulse length in the ps order, a high current, and a wide energy spectrum. Its unique beam quality has great potential for applications such as warm dense matter research, fast ignition, imaging, and cancer treatment.

[0004] Due to the presence of intense lasers, it is difficult to directly apply the micron-scale particle beam generated by laser target shooting. In addition, the hot electrons and strong electromagnetic pulses generated by target shooting interfere with the measurement. The instability of the interaction between laser and plasma results in fluctuations in the energy, charge, etc. of the accelerated particle beam. Different from the mono-energetic beam in traditional accelerators, the laser-driven particle beam usually has an exponentially rising energy spectrum, and the extended Bragg peak required for applications such as cancer treatment requires an energy spectrum that rises with energy. Therefore, energy spectrum shaping is needed to reduce the number of particles in the low-energy part. These problems require using a beam line to transmit the particle beam to the application end, maintaining the spatial and temporal characteristics of the particle beam, non-interceptively diagnosing and controlling the energy, energy spread, charge, etc. of the particle beam on the beam line, so that the laser accelerator can exert its true application value.

[0005] The achromatic system composed of quadrupole magnets and deflection magnets is a commonly used achromatic design, but it can only achieve achromatism in one transverse direction to realize point-to-point imaging transmission and cannot achieve achromatism in the other direction; even in the achromatic design, chromatic aberration still has an impact. This makes it difficult to maintain the quality of the laser-driven particle beam during transmission and affects the application of the laser accelerator. Summary of the Invention

[0006] Aiming at the problems existing in the above prior art, centering on the transmission and application of laser-driven particle beams, and aiming at the problem that the chromatic aberration effect in non-achromatic transmission causes the particle beam unable to achieve point-to-point transmission and the limitation of the single-direction achromatic beam line, the present invention proposes a point-to-point imaging and point-to-parallel imaging beam line transmission device and an implementation method thereof.

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

[0008] An object of the present invention is to provide a point-to-point imaging and point-to-parallel imaging beam line transmission device.

[0009] The point-to-point imaging and point-to-parallel imaging beam line transmission device of the present invention includes: a first and a second weak focusing magnet, and a triplet quadrupole lens; wherein, the first and the second weak focusing magnets have the same shape and size, and deflect particles in opposite directions; the entrance of the first weak focusing magnet faces the target point directly, and there is a first floating section between the entrance of the first weak focusing magnet and the target point. The length of the first floating section is L1, and in the laboratory coordinate system X′Y′Z′, the first floating section extends along the Z′ axis direction; the exit of the first weak focusing magnet faces the entrance of the second weak focusing magnet directly, and there is a second floating section between the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet. The length of the second floating section is L2; the exit of the second weak focusing magnet faces the exit of the double achromatic system, and there is a third floating section between the exit of the second weak focusing magnet and the exit of the double achromatic system. The length of the third floating section is L3, which extends along the Z′ axis direction, and the length of the third floating section is equal to the length of the first floating section, that is, L3 = L1; the first and the second weak focusing magnets and the first to the third floating sections form a double achromatic system; a triplet quadrupole lens is placed on the extension line of the exit of the second weak focusing magnet and the exit of the double achromatic system. The triplet quadrupole lens includes three quadrupole magnets; there is a fourth floating section between the exit of the double achromatic system and the triplet quadrupole lens. The length of the fourth floating section is L4, which extends along the Z′ axis direction, and the triplet quadrupole lens is arranged along the Z′ axis;

[0010] The interaction between the laser pulse and the target generates a particle beam on the target point with a micron scale. The beam enters the first weak focusing magnet after passing through the first floating section. The first weak focusing magnet deflects the particle beam. The particles have a deflection angle, and the deflection radius of particles with different energies is different. The deflection radius of particles with higher energy is larger. Therefore, at the exit of the first weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ. The particle coordinate system changes with the movement of the particles. The origin of the particle coordinate system is always at the reference particle. The reference particle is a hypothetical particle that always moves along a preset orbit. The Z axis always points along the forward direction of the reference particle. In the first and second weak focusing magnets, the X axis always points radially. The particle beam floats through the second floating section and enters the second weak focusing magnet. The divergence angle is the angle relative to the Z axis in the particle coordinate system. In each floating section, the divergence angle of the particles remains unchanged. In the first and second weak focusing magnets, the Z axis points tangentially. The divergence angle of the reference particle is always zero, but the deflection angle is not zero. The divergence angles of other particles change continuously during deflection but are not equal to the deflection angle. In the first and second weak focusing magnets, the change in the divergence angle is determined by the focusing forces in the X and Y directions. The focusing forces increase as the deflection angle increases. At the entrance of the second weak focusing magnet, particles with different energies are separated along the X direction. The particle beam leaving the exit of the second weak focusing magnet passes through the third and fourth floating sections and passes through a triplet quadrupole lens to achieve point-to-parallel imaging and reach the irradiation terminal.

[0011] Double achromatic requirements: In the second floating section, particles with the same energy in the X direction have the same divergence angle, that is, their trajectories are parallel to each other. At the same time, all particles are collimated in the Y direction, that is, parallel to the Z axis, and the divergence angle is 0. In the first and second weak focusing magnets with the same deflection angle, the deflection angles of all energies are the same, resulting in the divergence angles of low-energy and high-energy particles in the second floating section not meeting the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction. Therefore, edge angles are respectively set at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic end faces at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet have an included angle with the X direction, and the included angle is a (0 < a < 1 rad). The edge angles at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet change the deflection angles of the particles in the first and second weak focusing magnets, that is, reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles. While changing the deflection angle, the focusing forces in the X and Y directions are also changed. The change in the focusing force directly changes the divergence angle of the particles when leaving the first and second weak focusing magnets, reduces the focusing forces on low-energy particles in the X and Y directions, and increases the focusing forces on high-energy particles in the X and Y directions. At the exit of the double achromatic system, the longitudinal position of the image point (i.e., the focus) of low-energy particles appears later and the image point of high-energy particles appears earlier.

[0012] And two steering magnets are respectively arranged after the edge angles of the first weak focusing magnet and before the edge angles of the second weak focusing magnet; particles with the same energy and different initial divergence angles have different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, and the influence of the edge angles is different, resulting in different deflection angles, and they cannot be imaged simultaneously at the image point; the steering magnets after the edge angles of the first weak focusing magnet and before the edge angles of the second weak focusing magnet compensate for the influence of the edge angles on the divergence angle in the X direction; the magnetic field of the steering magnet is a uniform magnetic field, and the steering magnet deflects the particles. In the steering magnet, the change amount of the divergence angle is determined by the deflection angle and is equal to the deflection angle; the change amount of the divergence angle of the particles in the X direction is the same in magnitude and opposite in direction to the change amount of the divergence angle caused by the edge angles; the cooperation of the edge angles and the steering magnets ensures that the total deflection angles of particles with the same energy and different initial divergence angles are the same, and at the same time changes the deflection angles of particles with different energies, that is, the low-energy particles decrease and the high-energy particles increase, so that the divergence angles of the low-energy and high-energy particles meet the double achromatic requirements, that is, it meets the requirements that particles with the same energy have the same divergence angle in the X direction and all particles are collimated in the Y direction in the second floating section; effectively reduces the influence of chromatic aberration and the non-linear terms in the motion equation in achromatic transmission, so that the longitudinal positions of the image points of the low-energy, central-energy and high-energy particles are the same, realizing the point-to-point imaging transmission of particles with all energies from the target point to the exit of the double achromatic system, and retaining the high-brightness characteristics of the laser-driven particle beam.

[0013] The particle beams coming out from the target point are all transmitted in the pipeline, and the pipeline is kept in vacuum and passes through the pole face gaps of the first and second weak focusing magnets and the triplet quadrupole lenses; and there are no any obstacles on the path of the particle beams; the second floating section passes through the gap between the quadrupole magnets of the triplet quadrupole lens.

[0014] The first and second weak focusing magnets adopt C-shaped magnets, which is convenient for the operation of slit energy selection.

[0015] At the exit of the double achromatic system, the transverse phase space of the particle beam returns to the state at the target point, and the transverse size remains at the micron level at the target point. The particle beam output at the exit of the double achromatic system is a particle beam with a micron size, which is suitable for applications requiring high brightness; after the exit of the double achromatic system, point-to-parallel imaging is realized through the triplet quadrupole lens to change the particle beam into the centimeter level to meet the requirements of irradiation applications.

[0016] Using beam transport dynamics, strict relationship constraints between the deflection radius r and deflection angle θ of the central-energy particles of the first and second weak focusing magnets and the lengths L1 and L2 of the first and second floating sections and the magnetic field fall index n are obtained:

[0017] In the X direction:

[0018]

[0019] In the Y direction:

[0020]

[0021]

[0022] When the deflection radius r of the central energy particle and the length L1 of the first floating section are determined, from Equations (1.1) and (1.2), within the range of 0 < θ < 2π, the required deflection angle θ and the magnetic field fall index n are obtained, and then the length L2 of the second floating section is obtained through Equation (1.3). The deflection radius r of the central energy particle is proportional to the square root of the central energy, and the length L1 of the first floating section is selected between 0.1 m and 0.5 m. The length L2 of the second floating section is obtained from Equation (1.3), L3 = L1, and the parameters of the double achromatic system are determined, realizing that particles with the same energy have the same divergence angle in the second floating section between the first and second weak focusing magnets, that is, the trajectories are parallel to each other; at the same time, all particles are collimated in the Y direction.

[0023] After the particle beam is deflected by a set deflection angle in the first and second weak focusing magnets, particles with the same energy are focused and particles with different energies are separated along the X direction. A slit is arranged along the X direction in the first or second weak focusing magnet, so as to select the energy range of the particles.

[0024] In the double achromatic system, when the particles are deflected in the first and second weak focusing magnets, the deflection radius increases with the increase of energy and the path length increases. By selecting the appropriate deflection radius r of the central energy particle and the length L1 of the first floating section, and the other parameters are determined by Equations (1.1), (1.2) and (1.3), so that the positive and negative energy chirps generated by the weak focusing magnets and the floating section are cancelled, the longitudinal pulse length of the particle beam is compressed, and the short pulse characteristics of the laser-driven particle beam are maintained.

[0025] The length L4 of the fourth floating section and the parameters of the triple quadrupole lens (composed of the first, second and third quadrupole magnets Q1, Q2 and Q3) are selected according to the application requirements. The length L4 of the fourth floating section and the spacing ranges of the first, second and third quadrupole magnets are between 5 cm and 30 cm. On the basis of point-to-point imaging transmission from the target point to the exit of the double achromatic system, point-to-parallel imaging is realized through the triple quadrupole lens, and the particle beam is turned into a large-area collimated beam for irradiation.

[0026] The cross-sectional shape of the guiding magnet in the XZ plane is determined by the curve determined by z = 0 and Equation (1.4), and is rotated clockwise by an angle, and the rotation angle is equal to the edge angle. Where C is a constant determined by the magnetic field strength, and a is the angle between the magnetic extreme surfaces of the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet and the X direction.

[0027]

[0028] The direction of the current determines the direction of the magnetic field. When the current directions of the first and second weak focusing magnets are positive, proton beams, ion beams or positron beams are transmitted; when the current directions are negative, electron beams are transmitted.

[0029] Another object of the present invention is to provide a method for implementing a point-to-point imaging and point-to-parallel imaging beam line transmission device.

[0030] The method for implementing the point-to-point imaging and point-to-parallel imaging beam line transmission device of the present invention includes the following steps:

[0031] 1) Device setting:

[0032] a) The first and second weak focusing magnets have the same shape and size, and deflect particles in opposite directions;

[0033] b) The entrance of the first weak focusing magnet faces the target point directly. There is a first floating section between the entrance of the first weak focusing magnet and the target point. The length of the first floating section is L1, and in the laboratory coordinate system X′Y′Z′, the first floating section is along the Z′ axis direction;

[0034] c) The exit of the first weak focusing magnet faces the entrance of the second weak focusing magnet directly. There is a second floating section between the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet. The length of the second floating section is L2;

[0035] d) The exit of the second weak focusing magnet faces the exit of the double achromatic system. There is a third floating section between the exit of the second weak focusing magnet and the exit of the double achromatic system. The length of the third floating section is L3, along the Z′ axis direction, and the length of the third floating section is equal to the length of the first floating section, that is, L3 = L1;

[0036] e) The first and second weak focusing magnets and the first to third floating sections form a double achromatic system; A triple quadrupole lens is placed on the extension line of the exit of the second weak focusing magnet and the exit of the double achromatic system. The triple quadrupole lens includes three quadrupole magnets;

[0037] f) There is a fourth floating section between the exit of the double achromatic system and the triple quadrupole lens. The length of the fourth floating section is L4, along the Z′ axis direction, and the triple quadrupole lens is arranged along the Z′ axis;

[0038] 2) The interaction between the laser pulse and the target generates a particle beam on the target point with a micron scale. The particle beam enters the first weak focusing magnet after passing through the first floating section. The first weak focusing magnet deflects the particle beam. The particles have a deflection angle, and the deflection radii of particles with different energies are different. The deflection radius of particles with higher energy is larger. Thus, at the exit of the first weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ. The particle coordinate system changes with the movement of the particles. The origin of the particle coordinate system is always at the reference particle. The reference particle is a hypothetical particle that always moves along the preset orbit. The Z-axis always points along the forward direction of the reference particle. In the first and second weak focusing magnets, the X-axis always points along the radial direction. The particle beam floats through the second floating section and enters the second weak focusing magnet. The divergence angle is the angle relative to the Z-axis in the particle coordinate system. In each floating section, the divergence angle of the particles remains unchanged. In the first and second weak focusing magnets, the Z-axis points tangentially. The divergence angle of the reference particle is always zero, but the deflection angle is not zero. The divergence angles of other particles change continuously during deflection but are not equal to the deflection angle. In the first and second weak focusing magnets, the change in the divergence angle is determined by the focusing forces in the X and Y directions, and the focusing forces increase with the increase in the deflection angle. At the entrance of the second weak focusing magnet, particles with different energies are separated along the X direction.

[0039] 3) Double achromatic requirements: In the second floating section, particles with the same energy in the X direction have the same divergence angle, that is, the trajectories are parallel to each other. At the same time, all particles are collimated in the Y direction, that is, parallel to the Z-axis with a divergence angle of 0. In the first and second weak focusing magnets with the same deflection angle, the deflection angles of all energies are the same, resulting in the divergence angles of low-energy and high-energy particles in the second floating section not meeting the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction. Therefore, edge angles are respectively set at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic end faces at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet have an included angle with the X direction, and the included angle is a (0 < a < 1 rad). The edge angles at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet change the deflection angles of the particles in the first and second weak focusing magnets, that is, reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles. While changing the deflection angle, it also changes the focusing forces in the X and Y directions. The change in the focusing force directly changes the divergence angle of the particles when leaving the first and second weak focusing magnets, reduces the focusing forces on low-energy particles in the X and Y directions, and increases the focusing forces on high-energy particles in the X and Y directions. At the exit of the double achromatic system, the longitudinal position of the image point (i.e., the focus) of low-energy particles appears later and that of high-energy particles appears earlier.

[0040] 4) And two steering magnets are respectively arranged after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet; particles with the same energy and different initial divergence angles have different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, and the influence of the edge angle is different, resulting in different deflection angles, so they cannot be imaged simultaneously at the image point; the steering magnets after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet compensate for the influence of the edge angle on the divergence angle in the X direction; the magnetic field of the steering magnet is a uniform magnetic field, and the steering magnet deflects the particles. In the steering magnet, the change amount of the divergence angle is determined by the deflection angle and is equal to the deflection angle; the change amount of the divergence angle of the particles in the X direction is the same in magnitude and opposite in direction to the change amount of the divergence angle caused by the edge angle; the cooperation of the edge angle and the steering magnet ensures that the total deflection angles of particles with the same energy and different initial divergence angles are the same, and at the same time changes the deflection angles of particles with different energies, that is, the low-energy particles are reduced and the high-energy particles are increased, so that the divergence angles of the low-energy and high-energy particles meet the double achromatic requirements, that is, it meets the requirement that particles with the same energy have the same divergence angle in the X direction and all particles are collimated in the Y direction in the second floating section; effectively reduces the influence of chromatic aberration and the nonlinear terms in the motion equation in achromatic transmission, so that the longitudinal positions of the image points of the low-energy, central-energy and high-energy particles are the same, realizing the point-to-point imaging transmission of particles with all energies from the target point to the exit of the double achromatic system, and retaining the high brightness characteristics of the laser-driven particle beam;

[0041] 5) The particle beam leaving the exit of the second weak focusing magnet is transmitted through the third and fourth floating sections, passes through the triplet quadrupole lens, realizes point-to-parallel imaging, and reaches the irradiation terminal.

[0042] Advantages of the present invention:

[0043] Due to the energy spread and divergence angle of the particle beam, it inevitably expands laterally and longitudinally during transmission, so focusing is required. In addition, the energy range needs to be analyzed and selected; the present invention sets magnet elements in the transmission path, and uses the characteristics of the weak focusing magnet to focus simultaneously in the horizontal direction X and the vertical direction Y and analyze the energy in the X direction, designs a beam line scheme for double achromatic (achromatic in both the X direction and the Y direction) transmission based on the weak focusing effect, eliminates the influence of chromatic aberration on the particle beam transmission, obtains a particle beam close to the target size at the exit of the double achromatic system, retains the high brightness characteristics of the laser-driven particle beam, and realizes point-to-point imaging of a particle beam with large energy spread and large divergence angle; selects energy and shapes the energy spectrum during transmission; in addition, makes the particles with higher energy travel a longer path, compresses the pulse length, retains the short pulse characteristics of the particle beam, and meets the requirements of applications such as warm dense matter research and fast ignition for the spatial and temporal characteristics of the particle beam; realizes point-to-parallel imaging through the triplet quadrupole lens, turns the particle beam into a large-area collimated beam, and meets the requirements of applications such as cancer treatment. Description of the Drawings

[0044] Figure 1 Schematic diagram of an embodiment of the point-to-point imaging and point-to-parallel imaging beam line transmission device of the present invention;

[0045] Figure 2 Schematic diagram of the edge angle and guiding magnet of an embodiment of the point-to-point imaging and point-to-parallel imaging beam line transmission device of the present invention. Detailed implementation manners

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] As Figure 1 shown, the point-to-point imaging and point-to-parallel imaging beam line transmission device of this embodiment includes: a first weak focusing magnet M1, a second weak focusing magnet M2, and a triplet quadrupole lens; wherein, the first and second weak focusing magnets have the same shape and size, and opposite deflection directions; the entrance of the first weak focusing magnet faces the target point T directly, and there is a first floating section between the entrance of the first weak focusing magnet and the target point, the length of the first floating section is L1, and in the laboratory coordinate system X′Y′Z′, the first floating section is along the Z′ axis direction; the exit of the first weak focusing magnet faces the entrance of the second weak focusing magnet directly, and there is a second floating section between the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, the length of the second floating section is L2; the exit of the second weak focusing magnet faces the exit E of the double achromatic system, and there is a third floating section between the exit of the second weak focusing magnet and the exit of the double achromatic system, the length of the third floating section is L3, along the Z′ axis direction, and the length of the third floating section is equal to the length of the first floating section, that is, L3 = L1; the first and second weak focusing magnets and the first to third floating sections form a double achromatic system; a triplet quadrupole lens is placed on the extension line of the exit of the second weak focusing magnet and the exit of the double achromatic system, the triplet quadrupole lens includes first, second, and third quadrupole magnets Q1, Q2, and Q3, and there is a vacuum between each quadrupole magnet without a magnetic field, there is a fourth floating section between the exit of the double achromatic system and the triplet quadrupole lens, the length of the fourth floating section is L4, along the Z′ axis direction, and the triplet quadrupole lens is arranged along the Z′ axis. The particle beam B coming out from the target point T is all transmitted in the pipeline G, the pipeline maintains a vacuum, and passes through the pole face gaps of the first and second weak focusing magnets and the first, second, and third quadrupole magnets Q1, Q2, and Q3 of the triplet quadrupole lens to reach the irradiation terminal P; and there are no any obstacles on the path of the particle beam; the second floating section passes through the gap between the quadrupole magnets of the triplet quadrupole lens.

[0048] When the first and second weak focusing magnets have no edge angles, the magnetic pole end faces are parallel to the radial direction, and the reference particle enters or exits the magnet vertically. In Equations (1.1) and (1.2), due to the difference in the deflection radii of particles with different energies, the deflection angle θ that meets the double achromaticity requirement increases with energy. Without edge angles, the deflection angles of all particles are the same. The actual deflection angle of low-energy particles exceeds the angle required by double achromaticity, and excessive focusing forces are applied in the horizontal and vertical directions. As a result, at the exit E of the double achromaticity system, the longitudinal position of the image point (focus) of low-energy particles appears earlier than that of the central energy particles, while the image point of high-energy particles appears later. Eventually, at the image point of the central energy particles, particles with other energies cannot achieve point-to-point imaging, and the high brightness characteristic of the particle beam cannot be maintained, which directly affects subsequent point-to-parallel imaging. In addition, the non-linear terms in the motion equation also have an adverse effect on the transmission.

[0049] To reduce the influence of chromatic aberration, taking advantage of the characteristic that particles with different energies are separated along the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, edge angles are designed at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic pole end face has an angle with the radial direction, and the angle is a, as Figure 1 and Figure 2 shown, to reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles.

[0050] Particles with the same energy and different initial divergence angles are at different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet. The influence of the edge angle is different, resulting in different deflection angles and unable to form images simultaneously at the image point. Therefore, special guiding magnets need to be designed after the edge angle at the exit of the first weak focusing magnet and before the edge angle at the entrance of the second weak focusing magnet to compensate for the influence of the edge angle on the divergence angle in the X direction. The magnetic field of the guiding magnet is a uniform magnetic field, and the change in the divergence angle of the particles in the X direction increases with the position, and the shape is as Figure 2 shown, Figure 2 where O is the origin of the XZ coordinate system. The cooperation of the edge angle and the guiding magnet ensures that the deflection angles of particles with the same energy and different initial divergence angles are the same, while changing the deflection angles of particles with different energies (decreasing for low-energy particles and increasing for high-energy particles), effectively reducing the influence of chromatic aberration and the non-linear terms in the motion equation in achromatic transmission, achieving point-to-point imaging transmission from the target point T to the exit E of the double achromaticity system, and retaining the high brightness characteristic of the laser-driven particle beam. The cross-sectional shape of the guiding magnet in the XZ plane is determined by the curve determined by z = 0 and Equation (1.4), and rotated clockwise by an angle, and the rotation angle is equal to the edge angle, as Figure 2As shown by the shaded area, the apex angles of the two guiding magnets face each other and are located at the origin O of the XZ coordinate system. One side of the guiding magnet is adjacent to the edge angle. Where C is a constant determined by the magnetic field strength, and a is the angle between the magnetic pole end faces of the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet and the X direction. The cross-sectional shape of the guiding magnet in the XZ plane satisfies the following formula:

[0051]

[0052] In this embodiment, when transmitting a 15 MeV proton beam, the deflection radii of the first and second weak focusing magnets are designed to be 0.5 m, the magnetic field strength is 1 T, L1 = L3 = 0.15 m, L2 = 1.4 m, L4 = 0.15 m. The edge angles of the first and second weak focusing magnets are 0.39 rad. The lengths of the first, second, and third quadrupole magnets Q1, Q2, and Q3 of the triplet quadrupole lens are all 0.15 m. The distance between the first and second quadrupole magnets is 0.15 m, the distance between the second and third quadrupole magnets is 0.6 m, and the distance between the third quadrupole magnet and the irradiation platform can be selected between 0.1 - 1 m. The magnetic field gradients of the first, second, and third quadrupole magnets Q1, Q2, and Q3 are 0.223, -0.127, and 0.032 T / cm respectively. A circular hole slit is set at the entrance of the first weak focusing magnet to select the proton beam within a divergence angle of ±50 mrad. A slit S is set in the second weak focusing magnet to select the energy range, such as a 20% energy spread; for applications such as cancer treatment, the energy spectrum is shaped at the slit to reduce the number of low-energy protons.

[0053] The implementation method of the point-to-point imaging and point-to-parallel imaging beam transmission device in this embodiment includes the following steps:

[0054] 1) Set up the device as Figure 1 shown;

[0055] 2) The interaction between the laser pulse and the target generates a particle beam on the target point with a micron scale. The particle beam enters the first weak focusing magnet through the first floating section. The first weak focusing magnet deflects the particle beam, and the particles have a deflection angle. The deflection radii of particles with different energies are different, and the deflection radius of particles with higher energy is larger. Thus, at the exit of the first weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ. The particle coordinate system changes with the movement of the particles. The origin of the particle coordinate system is always at the reference particle. The reference particle is a hypothetical particle that always moves along the preset orbit. The Z-axis always points along the forward direction of the reference particle. In the first and second weak focusing magnets, the X-axis always points along the radial direction. The particle beam floats through the second floating section and enters the second weak focusing magnet. The divergence angle is the angle relative to the Z-axis in the particle coordinate system. In each floating section, the divergence angle of the particles remains unchanged. In the first and second weak focusing magnets, the Z-axis points along the tangential direction. The divergence angle of the reference particle is always zero, but the deflection angle is not zero, while the divergence angles of other particles change continuously during deflection but are not equal to the deflection angle. In the first and second weak focusing magnets, the change in the divergence angle is determined by the focusing forces in the X and Y directions, and the focusing forces increase with the increase in the deflection angle. At the entrance of the second weak focusing magnet, particles with different energies are separated along the X direction.

[0056] 3) Double achromatic requirements: In the second floating section, particles with the same energy in the X direction have the same divergence angle, that is, the trajectories are parallel to each other. At the same time, all particles are collimated in the Y direction, that is, parallel to the Z-axis, and the divergence angle is 0. In the first and second weak focusing magnets with the same deflection angle, the deflection angles of all energies are the same, resulting in the divergence angles of low-energy and high-energy particles in the second floating section not meeting the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction. Therefore, edge angles are respectively set at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic end faces at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet have an included angle with the X direction, and the included angle is a (0 < a < 1 rad). The edge angles at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet change the deflection angles of the particles in the first and second weak focusing magnets, that is, reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles. While changing the deflection angle, it also changes the focusing forces in the X and Y directions. The change in the focusing force directly changes the divergence angle of the particles when leaving the first and second weak focusing magnets, reduces the focusing forces on low-energy particles in the X and Y directions, and increases the focusing forces on high-energy particles in the X and Y directions. At the exit of the double achromatic system, the longitudinal position of the image point (i.e., the focus) of low-energy particles appears later and the image point of high-energy particles appears earlier.

[0057] 4) And two steering magnets are respectively arranged after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet; particles with the same energy but different initial divergence angles have different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, and the influence of the edge angle is different, resulting in different deflection angles, so they cannot be imaged simultaneously at the image point; the steering magnets after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet compensate for the influence of the edge angle on the divergence angle in the X direction; the magnetic field of the steering magnet is a uniform magnetic field, and the steering magnet deflects the particles. In the steering magnet, the change amount of the divergence angle is determined by the deflection angle and is equal to the deflection angle; the change amount of the divergence angle of the particles in the X direction is the same in magnitude and opposite in direction to the change amount of the divergence angle caused by the edge angle; the cooperation of the edge angle and the steering magnet ensures that the total deflection angles of particles with the same energy but different initial divergence angles are the same, and at the same time changes the deflection angles of particles with different energies, that is, the low-energy particles are reduced and the high-energy particles are increased, so that the divergence angles of the low-energy and high-energy particles meet the double achromatic requirements, that is, particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction; it effectively reduces the influence of chromatic aberration and the nonlinear terms in the motion equation in the achromatic transmission, so that the longitudinal positions of the image points of the low-energy, central-energy, and high-energy particles are the same, realizing the point-to-point imaging transmission of particles of all energies from the target point to the exit of the double achromatic system, and the size of the particle beam is kept at the micron level at the target point. At the same time, the longitudinal pulse length is compressed, and at the exit E of the double achromatic system, a high-brightness, short-pulse proton beam can be used for applications such as warm dense matter research and fast ignition;

[0058] 5) The particle beam leaving the exit of the second weak focusing magnet is transmitted through the third and fourth floating sections, passes through the triplet quadrupole lens, and reaches the irradiation terminal P to achieve point-to-parallel imaging, retain the high-brightness characteristic of the laser-driven particle beam, and obtain a particle beam with a diameter of 3 cm and uniform dose.

[0059] Beam diagnostic means can be added to the floating section to measure the proton beam parameters.

[0060] The current directions of the first and second weak focusing magnets determine the magnetic field directions of the first and second weak focusing magnets. When the current directions change, the magnetic field directions change. When the current directions of the first and second weak focusing magnets are positive, proton beams, ion beams or positron beams are transmitted; when the current directions are negative, electron beams are transmitted.

[0061] It can be seen from this embodiment that the present invention can achieve precise energy selection, retain the high-brightness characteristic, retain the short-pulse characteristic, and beam homogenization of high-energy-dispersion and large-divergence-angle particle beams in a compact space, break through the problems of high-quality applications of laser-driven particle beams, and promote the miniaturized application of laser accelerators. Using the technology of superconducting magnets to generate high-gradient magnetic fields, the present invention can transmit higher-energy particle beams in a compact space.

[0062] This embodiment is to demonstrate the general design of the beam line. In practical applications, usually only the high brightness and short pulse characteristics of the particle beam, or a large area uniform beam are required, and the beam line parameters can be optimized according to specific application requirements.

[0063] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, 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 content disclosed in the embodiments, and the scope of protection claimed by the present invention shall be subject to the scope defined by the claims.

Claims

1. A point-to-point imaging and point-to-parallel imaging beam transmission device, characterized in that The point-to-point imaging and point-to-parallel imaging beam line transmission device includes: a first and a second weak focusing magnet, and a triplet quadrupole lens; wherein, the first and the second weak focusing magnets have the same shape and size, and the deflection directions of the particles are opposite; the entrance of the first weak focusing magnet faces the target point, and there is a first floating section between the entrance of the first weak focusing magnet and the target point, the length of the first floating section is L1, and in the laboratory coordinate system X′Y′Z′, the first floating section is along the Z′ axis direction; the exit of the first weak focusing magnet faces the entrance of the second weak focusing magnet, and there is a second floating section between the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, the length of the second floating section is L2; the exit of the second weak focusing magnet faces the exit of the double achromatic system, and there is a third floating section between the exit of the second weak focusing magnet and the exit of the double achromatic system, the length of the third floating section is L3, along the Z′ axis direction, and the length of the third floating section is equal to the length of the first floating section, that is, L3 = L1; the first and the second weak focusing magnets and the first to the third floating sections constitute a double achromatic system; a triplet quadrupole lens is placed on the extension line of the exit of the second weak focusing magnet and the exit of the double achromatic system, and the triplet quadrupole lens includes three quadrupole magnets; there is a fourth floating section between the exit of the double achromatic system and the triplet quadrupole lens, the length of the fourth floating section is L4, along the Z′ axis direction, and the triplet quadrupole lens is arranged along the Z′ axis; The interaction between the laser pulse and the target generates a particle beam in the micron scale at the target point, which enters the first weak focusing magnet through the first floating section. The first weak focusing magnet deflects the particle beam, and the particles have a deflection angle. The deflection radii of particles with different energies are different, and the deflection radius of particles with higher energy is larger. Thus, at the exit of the first weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ; the particle coordinate system changes following the movement of the particles. The origin of the particle coordinate system is always at the reference particle. The reference particle is a hypothetical particle that always moves along the preset orbit. The Z axis is always along the forward direction of the reference particle. In the first and the second weak focusing magnets, the X axis is always along the radial direction; the particle beam floats through the second floating section and enters the second weak focusing magnet; the divergence angle is the angle relative to the Z axis in the particle coordinate system. In each floating section, the divergence angle of the particles remains unchanged. In the first and the second weak focusing magnets, the Z axis is along the tangential direction. The divergence angle of the reference particle is always zero, but the deflection angle is not zero, while the divergence angles of other particles change continuously during deflection but are not equal to the deflection angle; in the first and the second weak focusing magnets, the change amount of the divergence angle is determined by the focusing forces in the X and Y directions, and the focusing forces increase with the increase of the deflection angle; at the entrance of the second weak focusing magnet, particles with different energies are separated along the X direction; the particle beam leaving the exit of the second weak focusing magnet is transmitted through the third and the fourth floating sections, passes through the triplet quadrupole lens, realizes point-to-parallel imaging, and reaches the irradiation terminal; Double achromatic requirements: In the second floating section, particles with the same energy in the X direction have the same divergence angle, that is, the trajectories are parallel to each other. At the same time, all particles are collimated in the Y direction, that is, parallel to the Z axis, and the divergence angle is 0. In the first and second weak focusing magnets with the same deflection angle, the deflection angles of all energies are the same, resulting in the divergence angles of low-energy and high-energy particles in the second floating section not meeting the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction. Therefore, edge angles are respectively set at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic end faces of the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet have an included angle with the X direction, and the included angle is a. The edge angles at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet change the deflection angles of the particles in the first and second weak focusing magnets, that is, reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles. While changing the deflection angle, the focusing forces in the X and Y directions are also changed. The change in the focusing force directly changes the divergence angle of the particles when leaving the first and second weak focusing magnets, reduces the focusing forces received by low-energy particles in the X and Y directions, and increases the focusing forces received by high-energy particles in the X and Y directions. At the exit of the double achromatic system, the longitudinal position of the image point (i.e., the focus) of low-energy particles appears later and the image point of high-energy particles appears earlier. And two guiding magnets are respectively set after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet. Particles with the same energy and different initial divergence angles have different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, and the influence of the edge angle is different, resulting in different deflection angles and unable to form images simultaneously at the image point. The guiding magnets after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet compensate for the influence of the edge angle on the divergence angle in the X direction. The magnetic field of the guiding magnet is a uniform magnetic field. The guiding magnet deflects the particles. In the guiding magnet, the change amount of the divergence angle is determined by the deflection angle and is equal to the deflection angle. The change amount of the divergence angle of the particles in the X direction is the same in magnitude and opposite in direction to the change amount of the divergence angle caused by the edge angle. The cooperation of the edge angle and the guiding magnet ensures that the total deflection angles of particles with the same energy and different initial divergence angles are the same, and at the same time changes the deflection angles of particles with different energies, that is, the deflection angle of low-energy particles decreases and the deflection angle of high-energy particles increases, so that the divergence angles of low-energy and high-energy particles meet the double achromatic requirements, that is, meet the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction in the second floating section. It effectively reduces the influence of chromatic aberration and the nonlinear terms in the motion equation in achromatic transmission, so that the longitudinal positions of the image points of low-energy, central-energy, and high-energy particles are the same, realizing the point-to-point imaging transmission of particles of all energies from the target point to the exit of the double achromatic system and retaining the high-brightness characteristics of the laser-driven particle beam.

2. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, wherein, The deflection radius r and deflection angle θ of the central-energy particles of the first and second weak focusing magnets satisfy the following relationship with the lengths L1 and L2 of the first and second floating sections and the magnetic field fall index n: In the X direction: In the Y direction: After the deflection radius r of the central energy particles and the length L1 of the first floating section are determined, from equations (1.1) and (1.2), within the range of 0 < θ < 2π, the deflection angle θ and the magnetic field fall index n that meet the requirements are obtained, and then the length L2 of the second floating section is obtained through equation (1.3).

3. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, characterized in that, The cross-sectional shape of the guiding magnet in the XZ plane satisfies: Where C is a constant, and a is the angle between the magnetic pole end faces of the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet and the X direction.

4. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, wherein, When the current directions of the first and second weak focusing magnets are positive, proton beams or positron beams are transmitted; when the current directions are negative, electron beams are transmitted.

5. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, characterized in that, The length L4 of the fourth floating section is between 5 cm and 30 cm.

6. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, wherein The spacing range between the first, second, and third quadrupole magnets is between 5 cm and 30 cm.

7. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, characterized in that, It also includes a slit. A slit is provided along the X direction in the first or second weak focusing magnet to select the energy range of the particles.

8. The point-to-point imaging and point-to-parallel imaging beam line transmission device according to claim 1, characterized in that, The first and second weak focusing magnets adopt C-shaped magnets.

9. A method for implementing a point-to-point imaging and point-to-parallel imaging beam line transmission device as described in claim 1, characterized in that, The implementation method includes the following steps: 1) Device setting: a) The first and second weak focusing magnets have the same shape and size, and the deflection directions of the particles are opposite; b) The entrance of the first weak focusing magnet faces the target directly. There is a first floating section between the entrance of the first weak focusing magnet and the target. The length of the first floating section is L1. In the laboratory coordinate system X′Y′Z′, the first floating section is along the Z′ axis direction; c) The exit of the first weak focusing magnet faces the entrance of the second weak focusing magnet directly. There is a second floating section between the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet. The length of the second floating section is L2; d) The exit of the second weak focusing magnet faces the exit of the double achromatic system. There is a third floating section between the exit of the second weak focusing magnet and the exit of the double achromatic system. The length of the third floating section is L3, along the Z′ axis direction, and the length of the third floating section is equal to the length of the first floating section, that is, L3 = L1; e) The first and second weak focusing magnets and the first to third floating sections form a double achromatic system; A triple quadrupole lens is placed on the extension line of the exit of the second weak focusing magnet and the exit of the double achromatic system. The triple quadrupole lens includes three quadrupole magnets; f) There is a fourth floating section between the exit of the double achromatic system and the triple quadrupole lens. The length of the fourth floating section is L4, along the Z′ axis direction, and the triple quadrupole lens is arranged along the Z′ axis. 2) The interaction between the laser pulse and the target generates a particle beam on the target point with a micron scale. The beam enters the first weak focusing magnet through the first floating section. The first weak focusing magnet deflects the particle beam. The particles have a deflection angle, and the deflection radii of particles with different energies are different. The deflection radius of particles with higher energy is larger. Thus, at the exit of the first weak focusing magnet, particles with different energies are separated along the X direction of the particle coordinate system XYZ. The particle coordinate system changes following the movement of the particles. The origin of the particle coordinate system is always at the reference particle. The reference particle is a hypothetical particle that always moves along a preset orbit. The Z axis always points along the forward direction of the reference particle. In the first and second weak focusing magnets, the X axis always points along the radial direction. The particle beam floats through the second floating section and enters the second weak focusing magnet. The divergence angle is the angle relative to the Z axis in the particle coordinate system. In each floating section, the divergence angle of the particles remains unchanged. In the first and second weak focusing magnets, the Z axis points along the tangential direction. The divergence angle of the reference particle is always zero, but the deflection angle is not zero, while the divergence angles of other particles change continuously during deflection but are not equal to the deflection angle. In the first and second weak focusing magnets, the change in the divergence angle is determined by the focusing forces in the X and Y directions. The focusing forces increase as the deflection angle increases. At the entrance of the second weak focusing magnet, particles with different energies are separated along the X direction. 3) Double achromatic requirements: In the second floating section, particles with the same energy in the X direction have the same divergence angle, that is, their trajectories are parallel to each other. At the same time, all particles are collimated in the Y direction, that is, parallel to the Z axis, and the divergence angle is 0. In the first and second weak focusing magnets with the same deflection angle, the deflection angles of all energies are the same, resulting in the divergence angles of low-energy and high-energy particles in the second floating section not meeting the conditions that particles with the same energy in the X direction have the same divergence angle and all particles are collimated in the Y direction. Therefore, edge angles are respectively set at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, that is, the magnetic end faces at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet have an included angle with the X direction, and the included angle is a. The edge angles at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet change the deflection angles of the particles in the first and second weak focusing magnets, that is, reduce the deflection angle of low-energy particles and increase the deflection angle of high-energy particles. While changing the deflection angle, the focusing forces in the X and Y directions are also changed. The change in the focusing forces directly changes the divergence angles of the particles when leaving the first and second weak focusing magnets, reduces the focusing forces on low-energy particles in the X and Y directions, and increases the focusing forces on high-energy particles in the X and Y directions. At the exit of the double achromatic system, the longitudinal position of the image point (i.e., the focus) of low-energy particles appears later and that of high-energy particles appears earlier. 4) And two steering magnets are respectively arranged after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet; particles with the same energy and different initial divergence angles have different positions in the X direction at the exit of the first weak focusing magnet and the entrance of the second weak focusing magnet, and the influence of the edge angle is different, resulting in different deflection angles, so they cannot be imaged simultaneously at the image point; the steering magnets after the edge angle of the first weak focusing magnet and before the edge angle of the second weak focusing magnet compensate for the influence of the edge angle on the divergence angle in the X direction; the magnetic field of the steering magnet is a uniform magnetic field, and the steering magnet deflects the particles. In the steering magnet, the change amount of the divergence angle is determined by the deflection angle and is equal to the deflection angle; the change amount of the divergence angle of the particles in the X direction is the same in magnitude and opposite in direction to the change amount of the divergence angle caused by the edge angle; the cooperation of the edge angle and the steering magnet ensures that the total deflection angles of particles with the same energy and different initial divergence angles are the same, and at the same time changes the deflection angles of particles with different energies, that is, the low-energy particles decrease and the high-energy particles increase, so that the divergence angles of the low-energy and high-energy particles meet the double achromatic requirements, that is, it satisfies that particles with the same energy have the same divergence angle in the X direction and all particles are collimated in the Y direction in the second floating section; effectively reduces the influence of chromatic aberration and the nonlinear terms in the equation of motion in achromatic transmission, so that the longitudinal positions of the image points of the low-energy, central-energy, and high-energy particles are the same, realizing the point-to-point imaging transmission of particles with all energies from the target point to the exit of the double achromatic system, and retaining the high brightness characteristics of the laser-driven particle beam; 5) The particle beam leaving the exit of the second weak focusing magnet is transmitted through the third and fourth floating sections and passes through the triplet quadrupole lens, realizing point-to-parallel imaging and reaching the irradiation terminal.

10. The implementation method according to claim 9, wherein When the current directions of the first and second weak focusing magnets are positive, point-to-parallel imaging is realized to transmit the proton beam or the positron beam; when the current directions are negative, the electron beam is transmitted.

Images