Bifocal mode petal accelerator

Abstract

The invention relates to a bifocal mode petal accelerator, which belongs to the field of particle accelerators and comprises an injection section, an energizing section, a focusing section and a conversion target, the injection section comprises an electron gun, a bunching element, a solenoid and a collimator; the energizing section comprises a coaxial radio frequency acceleration cavity and a chromatic dispersion deflection structure around the coaxial radio frequency acceleration cavity; the focusing section comprises a quadrupole magnet group or a solenoid; the conversion target is a rotating target and comprises an inner circle and an outer ring which are of a concentric structure. Specific design is used in a petal-shaped accelerator, the petal-shaped accelerator comprises an achromatic deflection structure, a collimator, a quadrupole magnet set and the like, the beam focus and X-ray focal spot size of a high-energy X-ray source of the petal-shaped accelerator are compressed to 10 [mu] m level, and the innovatively designed bremsstrahlung conversion target based on concentric partition of a target surface is provided. And the compatibility of a single petal accelerator X-ray source to two focal spot size working modes is realized.

Description

Technical Field

[0001] This invention relates to the field of particle accelerators, and in particular to dual-focus mode petal accelerators. Background Technology

[0002] The petal accelerator is a high-energy particle accelerator independently developed in my country, utilizing a technology suitable for high-power electron beam acceleration. It can be widely applied in fields such as industrial irradiation sterilization, material modification, medical isotope production, and industrial non-destructive testing.

[0003] X-ray bremsstrahlung sources driven by electron accelerators with energies of megaelectronvolts (MeV) or higher are a key support for high-energy industrial X-ray computed tomography (CT) technology. These high-energy X-ray sources have been widely used in non-destructive testing of high-end, large-scale equipment, making significant contributions to the development of industries such as defense, aerospace, and rail transportation. Specifically, the interaction between the electron beam generated by the accelerator system and a bremsstrahlung target made of high atomic number material produces X-ray photons with energies exceeding MeV. These high-energy X-rays can penetrate large or dense objects, providing detailed information about their internal structure. To improve the crucial spatial resolution of CT systems, small-focal-spot high-energy X-ray bremsstrahlung sources are highly favored.

[0004] The petal-shaped accelerator is a primary technology for driving high-energy X-ray bremsstrahlung sources. The energy-enhancing element of the petal-shaped accelerator is a coaxial radio frequency accelerating cavity. The beam, deflected by surrounding diode magnets, forms a petal-shaped trajectory, repeatedly passing through the accelerating cavity and gaining energy. The lateral dimension of the beam is focused using a solenoid. A conversion target is placed at the focal point, where the beam drives the generation of bremsstrahlung X-rays. In existing literature, the achieved electron beam focal size is 46 μm, the full width at half maximum (FWHM) of the X-ray focal spot is 68 μm, and the X-ray dose rate at a distance of 1 m is 4700 cGy / min. The electron energy is 9 MeV, the target material is tantalum, and the target thickness is 1 mm.

[0005] However, the urgent national need for detecting minute defects in major equipment demands that high-energy industrial CT have better spatial resolution. Current technology can achieve an X-ray focal spot size of approximately 70 μm, but this is still not ideal. If the X-ray focal spot size could be further reduced to around 10 μm, the spatial resolution of CT could be significantly improved, breaking through current technological bottlenecks and providing strong technical support for the quality control and reliability of major national equipment. Furthermore, if both 70 μm and 10 μm X-ray focal spot sizes could be achieved in a single petal-shaped accelerator X-ray source, it could simultaneously serve different application needs, greatly expanding the application scenarios of the device.

[0006] The main reason why existing technologies struggle to further reduce X-ray focal spot size is the difficulty in achieving smaller electron beam focus sizes. Specifically, on the one hand, considering the effects of space charge and dispersion from the diode deflector magnet, the beam emittance is difficult to optimize further under current technologies. On the other hand, existing technologies use solenoids as the final focusing element, but their focusing intensity is limited, and the beam manipulation freedom is low. These factors collectively hinder the realization of smaller electron beam focuses and X-ray focal spots. Under such circumstances, dual-focus operating modes are naturally also difficult to achieve. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a dual-focus mode petal accelerator. Using a specific design, including an achromatic deflection structure, a collimation aperture, and a quadrupole magnet assembly, the beam focus and X-ray focal spot size of the petal-shaped accelerator high-energy X-ray source are compressed to the 10μm level. Furthermore, an innovative bremsstrahlung conversion target based on a concentric partitioning of the target surface is proposed, enabling a single petal accelerator X-ray source to be compatible with two focal spot size operating modes.

[0008] The present invention provides a dual-focus mode petal accelerator comprising an injection section, an energy-boosting section, a focusing section, and a conversion target through which electrons pass sequentially. The injection section comprises an electron gun, a focusing unit, a solenoid, and a collimator; the energy-boosting section comprises a coaxial radio frequency accelerating cavity and its surrounding achromatic deflection structure; the focusing section comprises a quadrupole magnet assembly or a solenoid; and the conversion target is a rotating target comprising an inner circle and an outer ring, with its target surface designed as a concentric structure. The inner circle and the outer ring have different target thicknesses, and different target thicknesses are selected corresponding to different partitions.

[0009] Furthermore, the beamforming unit employs a radio frequency beamforming device.

[0010] Furthermore, the diameter of the collimator is set according to the electron beam focal point size requirements and the beam simulation calculation results.

[0011] Furthermore, in the coaxial radio frequency accelerating cavity, the electron beam passes through multiple directions from multiple angles.

[0012] Furthermore, the de-dispersion deflection structure includes at least two diode magnets, the deflection radius, deflection angle, incident angle and exit angle of which are set according to the electron beam de-dispersion conditions and deflection geometry conditions.

[0013] Furthermore, the quadrupole magnet assembly includes several quadrupole magnets and a linear drift segment, and the number, strength, and position of the magnets are set according to the electron beam focal point size requirements and beam simulation calculation results.

[0014] Furthermore, the focusing section determines whether to use a quadrupole magnet assembly or a solenoid based on the electron beam focal spot size requirements and beam simulation calculation results.

[0015] Furthermore, the target thickness of the inner circle and the outer ring is determined based on the electron beam focal point size and Monte Carlo simulation results.

[0016] The beneficial effects of this invention are as follows: This invention uses a specific design, including an achromatic deflection structure, a collimation aperture, a quadrupole magnet assembly, etc., to compress the beam focus and X-ray focal spot size of the petal-shaped accelerator high-energy X-ray source to the 10μm level, and proposes an innovative bremsstrahlung conversion target based on a concentric partition of the target surface, so as to achieve compatibility of a single petal accelerator X-ray source with two focal spot size operating modes. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the petal accelerator of the present invention;

[0018] Figure 2 A schematic diagram of the achromatic deflection structure;

[0019] Figure 3 This is a schematic diagram of the conversion target structure;

[0020] Reference numerals: 1. Injection section; 101. Electron gun; 102. Focusing unit; 103. Solenoid; 104. Collimator; 2. Energy enhancement section; 201. Coaxial radio frequency accelerating cavity; 202. Achromatic deflection structure; 3. Focusing section; 301. Quadrupole magnet assembly; 302. Solenoid; 4. Conversion target. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 1 As shown, the dual-focus mode petal accelerator of this invention includes:

[0023] The electrons pass through the injection section, energy enhancement section, focusing section, and conversion target in sequence.

[0024] The injection section includes an electron gun, a focusing element, a solenoid, and a collimator, wherein the focusing unit employs an RF bundler.

[0025] The boosting section includes a coaxial radio frequency accelerating cavity and its surrounding achromatic deflection structure; the electron beam passes through the coaxial radio frequency accelerating cavity multiple times from multiple angles and directions;

[0026] The focusing section includes a quadrupole magnet assembly and a solenoid, corresponding to two working modes with different focal sizes, using the quadrupole magnet assembly and the solenoid for focusing respectively;

[0027] The conversion target is a rotating target, which includes an inner circle and an outer ring. Its target surface is designed as a concentric structure. The inner circle and the outer ring have different target thicknesses, and different target thicknesses are selected through different partitions.

[0028] In this embodiment, a collimator is placed before the beam first passes through the coaxial RF accelerating cavity. Its diameter can be determined based on the electron beam focal size requirements and beam simulation calculations. By adjusting its diameter, the upper limit of the lateral position of the electrons that can pass through can be controlled, thereby controlling the lateral size and emittance of the beam. When the collimator diameter is small, a sufficiently low emittance beam can be obtained, providing a basis for achieving a 10μm-level beam focal size. For example, a 10μm focal size corresponds to a 5mm diameter, or a 50μm focal size corresponds to a 20mm diameter. The significance of this technique is that introducing a collimator can block electrons whose lateral position exceeds its diameter, preventing them from advancing further; and by changing the collimator diameter, the lateral emittance of the surviving beam can be adjusted, providing a basis for achieving the corresponding beam focal size.

[0029] In this embodiment, an anti-dispersion deflection structure is used at the positions after the beam passes through the coaxial RF accelerating cavity, except for the last time. Figure 2 As shown, the achromatic deflection structure consists of two diode magnets. By adjusting its deflection radius, deflection angle, incident angle, and exit angle, the dispersion effect introduced by the deflecting magnets can be counteracted. Its specific parameters are determined by the electron beam achromatic conditions and deflection geometry. The significance of this technique lies in the fact that introducing the achromatic deflection structure can decouple the horizontal-longitudinal phase space of the beam, eliminating the influence of energy dispersion on the beam emittance and size, thus providing a basis for achieving the corresponding beam focal size.

[0030] In this embodiment, the focusing section includes a quadrupole magnet assembly and a solenoid. The focusing method is determined based on the electron beam focal spot size requirements and beam simulation calculation results. For example, the 50μm beam focal spot operating mode uses a simpler solenoid for focusing, in which case the quadrupole magnet assembly is not powered and does not operate; while the 10μm beam focal spot operating mode uses a quadrupole magnet assembly with stronger focusing capabilities and higher beam manipulation freedom, in which case the solenoid is not powered and does not operate. By adjusting the number, strength, and position of the quadrupole magnets, the lateral size of the beam can be focused, and the specific parameters are determined by the electron beam focal spot size requirements and beam simulation calculation results. The significance of this technical measure is that introducing a focusing section based on a quadrupole magnet assembly can provide a wider range of focusing intensity than a solenoid, and its upper limit for compressing the beam size is also higher; and by changing the position and strength of the magnets, a beam focal spot size of 10μm can be achieved.

[0031] In this embodiment, as Figure 3 As shown, the bremsstrahlung conversion target is designed with a concentric structure, with differences in target thickness between the inner circle and the outer ring. The target thickness of the inner circle and outer ring can be determined based on the electron beam focal spot size and Monte Carlo simulation results. For example, a 10 μm focal spot corresponds to a 0.1 mm target thickness for the outer ring, while a 50 μm focal spot corresponds to a 1 mm target thickness for the inner circle. Corresponding target partitions can be used according to different beam focal spots. Adjusting the target thickness can control the X-ray focal spot broadening effect caused by scattering, providing a basis for achieving X-ray focal spot sizes in the 10 μm range. By adjusting the target thickness of different partitions, the X-ray focal spot broadening effect caused by scattering can be controlled, providing a basis for achieving corresponding X-ray focal spot sizes.

[0032] In the description of the embodiments of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "center," "top," "bottom," "top," "bottom," "inner," "outer," "inner side," and "outer side," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. "Inner side" refers to the interior or enclosed area or space. "Outer perimeter" refers to the area surrounding a specific component or specific area.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dual-focus mode petal accelerator, comprising an injection section, an energy-boosting section, a focusing section, and a conversion target through which electrons pass sequentially, characterized in that, The injection section includes an electron gun, a focusing unit, a solenoid, and a collimator; the energy enhancement section includes a coaxial radio frequency accelerating cavity and its surrounding achromatic deflection structure; the focusing section includes a quadrupole magnet assembly or a solenoid; the conversion target is a rotating target, including an inner circle and an outer ring, with its target surface designed as a concentric structure, and the inner circle and outer ring have different target thicknesses, with different target thicknesses selected corresponding to different partitions.

2. The dual-focus mode petal accelerator according to claim 1, characterized in that, The beamforming unit employs a radio frequency beamforming device.

3. The dual-focus mode petal accelerator according to claim 1, characterized in that, The diameter of the collimator is set according to the electron beam focal point size requirements and the beam simulation calculation results.

4. The dual-focus mode petal accelerator according to claim 1, characterized in that, In the coaxial radio frequency accelerating cavity, the electron beam passes through multiple directions from multiple angles.

5. The dual-focus mode petal accelerator according to claim 1, characterized in that, The de-dispersion deflection structure includes at least two diode magnets, whose deflection radius, deflection angle, incident angle and exit angle are set according to the electron beam de-dispersion conditions and deflection geometry conditions.

6. The dual-focus mode petal accelerator according to claim 1, characterized in that, The quadrupole magnet group includes several quadrupole magnets and a linear drift segment. The number, strength, and position of the magnets are set according to the electron beam focal point size requirements and beam simulation calculation results.

7. The dual-focus mode petal accelerator according to claim 1, characterized in that, The focusing section determines whether to use a quadrupole magnet assembly or a solenoid based on the electron beam focal spot size requirements and beam simulation calculation results.

8. The dual-focus mode petal accelerator according to claim 1, characterized in that, The target thickness of the inner circle and the outer ring is determined based on the electron beam focal point size and Monte Carlo simulation results.

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