Integrated bunching and energizing device

Abstract

The invention discloses an integrated bunching and energizing standing wave acceleration structure, and relates to the technical field of particle acceleration, the integrated bunching and energizing standing wave acceleration structure comprises a cavity structure, a hollow pipeline is arranged in the cavity structure, the inlet end of the hollow pipeline is a bunching gap, and the outlet end of the hollow pipeline is an energizing gap; the voltage of the beam bunching gap is lower than that of the energy increasing gap, so that beam bunching and large-amplitude energy increasing of the beam with relatively low energy can be realized at the same time; according to the integrated bunching and energizing standing wave acceleration structure, bunching and acceleration, namely energizing, of beam current can be achieved at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of particle acceleration technology, in particular to an integrated bunching and energy-increasing standing wave acceleration structure. BACKGROUND

[0002] Accelerating charged particles by electric field in radio frequency or microwave band is the main particle acceleration method at present, wherein the smaller the phase width of the beam in the radio frequency field, the smaller the beam energy spread and emittance that can be achieved, and thus the better the beam quality, which is beneficial to the application of the beam in multiple aspects.

[0003] For example, in industrial CT non-destructive testing, the focal spot size of the electron beam can be reduced; in free electron laser application, better beam quality can reduce the gain length and improve the saturated output power; the most common bunching method is to let the beam with a speed that has not reached a very high relativistic degree, i.e., the speed has not yet fully approached the speed of light, pass through a radio frequency acceleration gap in a so-called zero acceleration phase, so that the particles at the head of the beam are slightly decelerated and thus their speed is slowed down, and the particles at the tail of the beam are slightly accelerated and thus their speed is increased; after passing through the acceleration gap, the beam is allowed to move freely for a period of time, and the length of the beam gradually decreases. Through specific design, the length of the beam can be greatly reduced to achieve the effect of bunching; however, bunching leads to an increase in the peak current of the beam, and thus the space charge effect causes the lateral size of the beam to increase rapidly, which is not conducive to the transmission of the accelerator beam.

[0004] In high-power accelerators, the beam with a large current is accelerated, and the peak power and average power of the beam generated are high; for industrial irradiation accelerators applied to cobalt source replacement, an electron beam with hundreds of kilowatts of average power needs to be generated to pass through a bremsstrahlung target to convert into X-rays, which requires the beam to have a large current.

[0005] In the disclosed petal accelerator design, a high-voltage radio frequency grid-controlled hot cathode electron gun of 60kV instead of the conventional 40kV is used to reduce the influence of the space charge effect of the beam under high current; and the beam quality is poor without bunching, and the petal accelerator uses 6 times of acceleration instead of more times of acceleration, which leads to relatively low energy efficiency.

[0006] In summary, the disclosed design has the following deficiencies: the use of a bunching cavity for bunching faces the problem of too strong space charge effect under large current; and directly increasing the voltage of the radio frequency grid-controlled electron gun leads to poor beam quality and reduced reliability. SUMMARY

[0007] In view of the above technical problems, the present application proposes the following technical solutions:

[0008] An integrated bunching and energy boosting standing wave accelerating structure, comprising a cavity structure, a hollow pipe is arranged in the cavity structure, an entrance end of the hollow pipe is a bunching gap, an exit end of the hollow pipe is an energy boosting gap, a radio frequency electric field phase of the bunching gap and the energy boosting gap is 180 degrees, that is, at the same time, a radio frequency electric field direction of the bunching gap and the energy boosting gap is opposite.

[0009] Further, a voltage of the bunching gap is lower than a voltage of the energy boosting gap, so as to simultaneously realize bunching of a relatively low-energy beam and large-amplitude energy boosting; a distance between the bunching gap and the energy boosting gap (an equivalent position of a gap beam effect) is set as 3βλ / 4; a voltage amplitude ratio of the bunching gap and the energy boosting gap ranges from 1:4 to 1:40.

[0010] Further, a plurality of partitions are arranged in the cavity structure, the partitions are used to support the hollow pipe; the plurality of partitions are uniformly arranged in the cavity structure, the cavity structure is used to adjust a resonant frequency and a voltage ratio of the bunching gap and the energy boosting gap, a plurality of fan-shaped through holes are arranged in the partitions, and positions of the partitions in the cavity structure and sizes and positions of the fan-shaped through holes can affect the resonant frequency and the voltage ratio of the bunching gap and the energy boosting gap.

[0011] Further, the partitions divide the cavity structure into two regions, a region from the partitions to the energy boosting gap in the cavity structure is a right region, and a region from the partitions to the bunching gap in the cavity structure is a left region.

[0012] Further, the right region comprises an inner conductor and an outer conductor, the inner conductor is arranged outside the hollow pipe, the outer conductor is arranged on an inner wall of the cavity structure, the inner conductor and the outer conductor arranged on the cavity structure are coaxial structures, the inner conductor is a generalized tapered structure and is used to improve shunt impedance, a closest end of the inner conductor to the energy boosting gap is a minimum end, and a farthest end of the inner conductor from the energy boosting gap is a maximum end.

[0013] Further, the outer conductor structure is the same as the inner conductor, the outer conductor is a generalized tapered structure, a closest end of the outer conductor to the energy boosting gap is a minimum end, and a farthest end of the outer conductor from the energy boosting gap is a maximum end.

[0014] Further, the left region comprises a nose cone structure, the nose cone structure is formed by the beam pipe and the cavity structure, and the nose cone structure is used to shield a radio frequency magnetic field to avoid adverse effects of the magnetic field on the beam.

[0015] Further, a plurality of radio frequency signal pickers are arranged in the cavity structure, and the radio frequency signal pickers in the cavity structure are uniformly distributed in the right area and the left area; the radio frequency signal pickers are arranged at least two in the cavity structure, and one radio frequency signal picker is arranged in the right area and the left area.

[0016] Further, the right area is a strong field area in the cavity structure, and the radio frequency signal pickers are used for measuring and feedback controlling the amplitude and phase of the radio frequency field in the cavity structure.

[0017] Further, the left area is a weak field area in the cavity structure, and the left area is prone to secondary electron multiplication behavior, and the radio frequency signal pickers are used for monitoring and necessary protection of the secondary electron multiplication behavior in the cavity structure.

[0018] Further, the cavity structure further comprises an input coupler for feeding the required radio frequency power into the cavity structure.

[0019] Further, two fan-shaped through holes are arranged on the partition plate, and the two fan-shaped through holes on the partition plate are symmetrically arranged.

[0020] Further, four fan-shaped through holes are arranged on the partition plate, and the four fan-shaped through holes on the partition plate are uniformly arranged.

[0021] The beneficial effects of the present application compared with the prior art are: (1) the integrated bunching and energy-increasing standing wave acceleration structure can realize bunching and acceleration of the beam, that is, energy increasing.

[0022] (2) The integrated bunching and energy-increasing standing wave acceleration structure can improve the quality of the electron beam, so that the beam size can be smaller in the petal accelerator, and the energy efficiency of the entire accelerator is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a cavity structure, hollow pipe, partition plate, and internal conductor cross-sectional structure diagram.

[0024] Figure 2 It is a partition plate with four fan-shaped through holes overall structure diagram.

[0025] Figure 3 It is a partition plate with four fan-shaped through holes partition plate structure diagram.

[0026] Figure 4 It is a partition plate with four fan-shaped through holes cavity structure, hollow pipe, and partition plate cross-sectional structure diagram.

[0027] Figure 5The overall structure schematic diagram after two fan-shaped through holes are arranged in the partition plate of the application.

[0028] Figure 6 The partition plate structure schematic diagram after two fan-shaped through holes are arranged in the partition plate of the application.

[0029] Figure 7 The cavity structure, hollow pipe, and partition plate structure schematic diagram after two fan-shaped through holes are arranged in the partition plate of the application.

[0030] The reference signs: 10-cavity structure; 20-hollow pipe; 30-bunching gap; 40-energy increasing gap; 50-partition plate; 60-inner conductor; 70-nose cone structure; 80-fan-shaped through hole. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the application more clear and understandable, the application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and do not limit the application.

[0032] Example 1:

[0033] An integrated bunching and energy increasing standing wave acceleration structure, as shown in FIG. 1, comprises: Figure 1

[0034] A cavity structure 10, wherein a hollow pipe 20 is arranged in the cavity structure 10, an entrance end of the hollow pipe 20 is a bunching gap 30, an exit end of the hollow pipe 20 is an energy increasing gap 40, and a plurality of partition plates 50 are arranged in the cavity structure 10, and the partition plates 50 are used to support the hollow pipe 20;

[0035] The radio frequency electric field phases of the bunching gap 30 and the energy increasing gap 40 are 180 degrees different, that is, at the same time, the radio frequency electric field directions of the bunching gap 30 and the energy increasing gap 40 are opposite, and the voltage of the bunching gap 30 is much lower than that of the energy increasing gap 40, so as to simultaneously realize the bunching of the relatively low energy beam and the large amplitude energy increasing, so as to effectively reduce the influence of the space charge effect in the subsequent beam transmission, thereby realizing the design requirements of low phase width and high current intensity of the beam;

[0036] The distance between the bunching gap 30 and the energy increasing gap 40 (the equivalent position of the gap beam effect) is set as 3βλ / 4, wherein β is the relativistic velocity of the beam (the ratio of the average motion velocity of the beam to the speed of light), and λ is the design working frequency of the cavity, which is one time or N times (N is a positive integer) of the micro-pulse repetition frequency f0 of the entrance beam; in this way, the beam can meet the requirements of the average energy increasing of 0 when passing through the bunching gap 30, and the beam is just located at the peak acceleration phase when passing through the energy increasing gap 40; ​

[0037] The voltage amplitude ratio of the bunching gap 30 to the energizing gap 40 ranges from 1:4 to 1:40; in this way, the electron beam with tens of keV can be effectively bunched after passing through the bunching gap 30, and its energy can be significantly increased after passing through the energizing gap 40, so that the increase of the beam envelope size caused by the space charge effect in the subsequent transmission process can be effectively inhibited.

[0038] The cavity structure 10 is used to realize radio frequency resonance at a desired design frequency, and the cavity structure 10 has high shunt impedance and the required voltage amplitude ratio of the bunching gap 30 to the energizing gap 40.

[0039] Embodiment 2:

[0040] This embodiment is further extended on the basis of Embodiment 1, as shown in Figure 1 The partition plate 50 divides the cavity structure 10 into two regions, the region of the partition plate 50 to the energizing gap 40 in the cavity structure 10 is the right region, and the region of the partition plate 50 to the bunching gap 30 in the cavity structure 10 is the left region.

[0041] The right region includes an inner conductor 60 and an outer conductor, the inner conductor 60 is arranged outside the hollow pipe 20, and the outer conductor is arranged on the inner wall of the cavity structure 10. The inner conductor 60 and the outer conductor arranged on the cavity structure 10 are coaxial structures. The inner conductor 60 is a generalized tapered structure to improve the shunt impedance. The inner conductor 60 has a minimum end near one end of the energizing gap 40, and a maximum end away from the other end of the energizing gap 40.

[0042] The outer conductor structure is the same as the inner conductor 60. The outer conductor is a generalized tapered structure. The outer conductor has a minimum end near one end of the energizing gap 40, and a maximum end away from the other end of the energizing gap 40.

[0043] The left region includes a nose cone structure 70, which is formed by the beam pipe and the cavity structure 10. The nose cone structure 70 is used to shield the radio frequency magnetic field to avoid the adverse effects of the magnetic field on the beam.

[0044] Embodiment 3:

[0045] This embodiment is further extended on the basis of Embodiment 2, as shown in Figure 1 A plurality of radio frequency signal pickups are arranged in the cavity structure 10. The radio frequency signal pickups in the cavity structure 10 are uniformly distributed in the right region and the left region.

[0046] At least two radio frequency signal pickups are provided in the cavity structure 10, with one radio frequency signal pickup in the right region and one in the left region of the cavity structure 10.

[0047] The right-side region is a strong field region within the cavity structure 10, and its radio frequency signal pickup is used to measure and control the amplitude and phase of the radio frequency field within the cavity structure 10.

[0048] The left-side region is a weak field region within the cavity structure 10, where secondary electron multiplication is prone to occur. The radio frequency signal pickup is used to monitor and protect the secondary electron multiplication behavior within the cavity structure 10.

[0049] The cavity structure 10 also includes an input coupler for feeding the required radio frequency power into the cavity structure 10.

[0050] Example 4:

[0051] This embodiment further expands upon embodiment 1 by modifying the partition 50, specifically as follows: Figure 1 As shown, multiple partitions 50 are evenly distributed within the cavity structure 10. The cavity structure 10 is used to adjust the resonant frequency and the voltage ratio of the beam-focusing gap to the energy-enhancing gap. Multiple fan-shaped through holes 80 are provided in each partition 50. The left-right position of the partition 50 within the cavity structure 10, as well as the size and position of the fan-shaped through holes 80, can affect the resonant frequency and the voltage ratio of the beam-focusing gap to the energy-enhancing gap. Designers can adjust the position of the partitions 50 within the cavity structure 10 according to actual needs, and can also change the size and position of the fan-shaped through holes 80 within the partitions 50 to adjust the resonant frequency and the voltage ratio of the beam-focusing gap 30 to the energy-enhancing gap 40. Furthermore, in specific designs, to achieve the required voltage ratio of the beam-focusing gap 30 to the energy-enhancing gap 40, the fan-shaped through holes 80 provided on the partitions 50 within the cavity structure 10 need to be relatively large.

[0052] Example 5:

[0053] This embodiment further expands upon the partition 50 based on embodiment 4, specifically as follows: Figures 1 to 4 As shown, the present invention serves as the injector for a petal accelerator, enabling high-flow, high-quality injection. The partition 50 is provided with two fan-shaped through holes 80, which are symmetrically arranged.

[0054] In practical use, the injector used includes an RF gate-controlled hot cathode electron gun with a power boosting gap of 40kV, an RF frequency cavity structure of 108MHz, and generates an electron beam with a phase width of 1 and a hollow tube of 20 degrees. The average current intensity of the electron beam is 50mA, and the peak current intensity is 261mA.

[0055] The electron beam is injected into the cavity structure 10, and the cavity resonance frequency of the cavity structure 10 is 108 MHz.

[0056] In the embodiment, the distance between the bunching gap 30 and the energy-increasing gap 40 is 3βλ / 4=779 mm.

[0057] The voltage ratio of the bunching gap 30 and the energy-increasing gap 40 is selected as 1:9, and the voltage of the bunching gap 30 is selected as 19 kV; after passing through the bunching gap 30, the average energy of the electron beam is increased to 211 keV, and the phase width of the beam current is compressed to 18% of the initial width, that is, about 22 degrees.

[0058] The total length of the embodiment is 880 mm, the maximum outer diameter of the embodiment is 520 mm, the radio frequency loss power corresponding to the energy-increasing of 171 kV is about 16 kW, the 211 keV beam current is injected into the petal-shaped accelerator main accelerating cavity, and is further accelerated to 7 MeV and converted into X rays by a bremsstrahlung target, and then industrial irradiation sterilization and disinfection are carried out.

[0059] Embodiment 6:

[0060] In the embodiment, the distance between the bunching gap 30 and the energy-increasing gap 40 is 3βλ / 4=779 mm. Figure 1 And Figures 5 to 7 As shown in the figure, the energy-increasing beam has small energy dispersion, and is used for focusing and targeting; four fan-shaped through holes 80 are arranged on the baffle 50; and the four fan-shaped through holes 80 are uniformly arranged on the baffle 50.

[0061] In specific use, the injector includes a 40 kV radio frequency grid-controlled hot cathode electron gun, a radio frequency frequency cavity structure 108 MHz, generates an electron beam with a phase width of 60 degrees, and the average current of the electron beam is 1 mA.

[0062] The electron beam is injected into the cavity structure 10, and the cavity resonance frequency of the cavity structure 10 is 108 MHz.

[0063] In the embodiment, the distance between the bunching gap 30 and the energy-increasing gap 40 is 3βλ / 4=779 mm.

[0064] The voltage ratio of the bunching gap 30 and the energy-increasing gap 40 is selected as 1:9, and the voltage of the bunching gap 30 is selected as 19 kV; after passing through the bunching gap 30, the average energy of the electron beam is increased to 211 keV, and the phase width of the beam current is compressed to 18% of the initial width, that is, about 22 degrees.

[0065] The total length of the application is 880mm, the maximum outer diameter of the application is 600mm, and the radio frequency loss power corresponding to the 300kV energy increase of the bunching gap is about 36kW; the 40keV beam energy divergence bottom width of the energy increase gap is less than 4%, the beam is focused to a focal point size of less than 0.03mm through the magnetic lens, and after being converted into X-rays through the bremsstrahlung target, the nondestructive testing application is carried out.

[0066] The above merely describes the preferred embodiments of the present application, but is not used to limit the protection scope of the present application.

Claims

1. An integrated beam-focusing and energy-enhancing standing wave acceleration structure, characterized in that: Includes a cavity structure (10), in which a hollow pipe (20) is provided. The inlet end of the hollow pipe (20) is a beam-focusing gap (30), and the outlet end of the hollow pipe (20) is an energy-enhancing gap (40). The radio frequency electric fields of the beam-focusing gap (30) and the energy-enhancing gap (40) are 180 degrees out of phase, that is, at the same moment, the radio frequency electric fields of the beam-focusing gap (30) and the energy-enhancing gap (40) are in opposite directions. The voltage of the focusing gap (30) is lower than that of the energy-enhancing gap (40) to simultaneously achieve focusing of the relatively low-energy beam and a larger energy enhancement; the distance between the focusing gap (30) and the energy-enhancing gap (40) (the equivalent position of the gap beam action) is set to 3βλ / 4; the voltage amplitude ratio between the focusing gap (30) and the energy-enhancing gap (40) is in the range of 1:4 to 1:

40.

2. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 1, characterized in that: The cavity structure (10) is provided with a plurality of partitions (50), which are used to support the hollow pipe (20); Multiple partitions (50) are evenly distributed within the cavity structure (10). The cavity structure (10) is used to adjust the resonant frequency and the voltage ratio of the beam-focusing gap to the energy-enhancing gap. Multiple fan-shaped through holes (80) are provided in the partitions (50). The position of the partitions (50) in the cavity structure (10), as well as the size and position of the fan-shaped through holes (80), can affect the resonant frequency and the voltage ratio of the beam-focusing gap (30) to the energy-enhancing gap (40).

3. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 2, characterized in that: The partition (50) divides the cavity structure (10) into two regions: the region from the partition (50) to the energy-enhancing gap (40) is the right region, and the region from the partition (50) to the beam-gathering gap (30) is the left region.

4. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 3, characterized in that: The right-side region includes an inner conductor (60) and an outer conductor. The inner conductor (60) is disposed outside the hollow pipe (20), and the outer conductor is disposed on the inner wall of the cavity structure (10). The inner conductor (60) and the outer conductor disposed on the cavity structure (10) are coaxial. The inner conductor (60) is a generalized conical structure to improve the shunt impedance. The end of the inner conductor (60) closer to the energy-enhancing gap (40) is the minimum end, and the end of the inner conductor (60) further away from the energy-enhancing gap (40) is the maximum end.

5. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 4, characterized in that: The outer conductor has the same structure as the inner conductor (60). The outer conductor is a generalized conical structure. The end of the outer conductor closest to the energy-enhancing gap (40) is the minimum end, and the end of the outer conductor furthest from the energy-enhancing gap (40) is the maximum end.

6. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 3, characterized in that: The left-side region includes a nose cone structure (70), which is formed by a beam channel and a cavity structure (10) and is used to shield the radio frequency magnetic field.

7. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 3, characterized in that: Multiple radio frequency (RF) signal pickups are provided inside the cavity structure (10). The RF signal pickups inside the cavity structure (10) are evenly distributed in the right and left regions. At least two RF signal pickups are provided inside the cavity structure (10), with one RF signal pickup in the right region and one in the left region.

8. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 7, characterized in that: The right-side region is a strong field region within the cavity structure (10), and the radio frequency signal pickup is used to measure and control the amplitude and phase of the radio frequency field within the cavity structure (10).

9. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 7, characterized in that: The left-side region is a weak field region within the cavity structure (10). Secondary electron multiplication is prone to occur within the left-side region. The radio frequency signal pickup is used to monitor and protect the secondary electron multiplication behavior within the cavity structure (10).

10. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 1, characterized in that: The cavity structure (10) also includes an input coupler for feeding the required radio frequency power into the cavity structure (10).

11. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 2, characterized in that: The partition (50) is provided with two fan-shaped through holes (80), and the two fan-shaped through holes (80) on the partition (50) are symmetrically arranged.

12. The integrated beam-focusing and energy-enhancing standing wave acceleration structure according to claim 2, characterized in that: The partition (50) is provided with four fan-shaped through holes (80), which are evenly distributed on the partition (50).

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