Feed-forward control method for high-power petal accelerator

Abstract

The invention discloses a high-power petal accelerator and a feed-forward control method, and relates to the technical field of particle accelerators, and the high-power petal accelerator comprises an electron beam source, a beam current intensity detector, a petal accelerator, and a radio frequency low level control system. The electron beam source is used for emitting an electron beam current, the beam current intensity detector is arranged before the electron beam current enters an injection port of the petal accelerator, and the radio frequency low level control system is used for receiving a signal emitted when the beam current intensity detector works. The radio frequency low-level control system adjusts an excitation signal and an amplitude phase in real time through a signal sent by a beam current intensity detector, and compensates cavity pressure change caused by beam current load fluctuation; according to the device, the beam current intensity detector is used for measuring the electron beam current load variable quantity, the amplitude and the phase of an excitation signal are adjusted at the corresponding moment, the cavity pressure change caused by beam current load fluctuation is compensated, and therefore the amplitude and the phase of an accelerating electric field are kept stable.

Description

Technical Field

[0001] The present invention relates to the technical field of particle accelerators, and in particular to a high-power petal accelerator and a feedforward control method. Background Art

[0002] Due to its high-power beam characteristics, petal accelerators are widely used in industrial irradiation, medical isotope preparation and other fields. Under high-power operation, the beam loading effect of the petal accelerator is strong, and fluctuations in the beam current intensity can easily cause disturbances in the acceleration voltage of the high-frequency accelerating cavity, thereby leading to fluctuations in the beam energy. The motion trajectory of the beam in the petal accelerator is very sensitive to energy changes, which increases the risk of beam loss due to trajectory disturbances, and is also not conducive to application fields with high energy stability requirements (such as industrial CT).

[0003] Low-level control technology is the key to ensuring the stable operation of the petal accelerator. The current common method is based on the sampling of the cavity pressure signal in the high-frequency acceleration cavity, combined with the traditional PID feedback control excitation signal output to achieve the stability of the cavity pressure signal. However, due to the narrow bandwidth of the high-frequency cavity loop of the petal accelerator and the long system response time, pure feedback control has a lag problem when dealing with strong beam load disturbances. Especially in the pulse operation mode, the cavity pressure reduction problem introduced by the pulse head of the beam load cannot be effectively solved by feedback control. At this time, the beam is always accelerated in an electric field deviating from the working point, resulting in energy dissipation, thereby increasing the risk of beam loss. Therefore, it is necessary to introduce advanced RF low-level control technology to ensure the stability of the beam acceleration process. Summary of the Invention

[0004] In view of the above technical problems, the present invention proposes the following technical solutions:

[0005] A high-power petal accelerator comprises an electron beam source, a beam current intensity detector, a petal accelerator, and a radio frequency low-level control system; the electron beam source is arranged outside the petal accelerator and is used to emit an electron beam; the beam current intensity detector is arranged before the electron beam enters the injection port of the petal accelerator and is used to detect the electron beam current intensity output by the electron beam source.

[0006] Furthermore, the RF low-level control system is used to receive the signal emitted by the beam current intensity detector when it is working. The RF low-level control system adjusts the excitation signal and amplitude phase in real time through the signal emitted by the beam current intensity detector to compensate for the cavity pressure change caused by the beam load fluctuation.

[0007] Furthermore, the petal accelerator includes a high-frequency cavity and multiple deflection magnets. The deflection magnets are arranged outside the high-frequency cavity. A cavity pressure signal sampling device is arranged inside the petal accelerator to collect sampling signals inside the high-frequency cavity of the petal accelerator.

[0008] The present invention also provides a feedforward control method for a high-power petal accelerator, comprising the following steps:

[0009] S1: The electron beam source emits an electron beam into the petal accelerator;

[0010] S2: When the electron beam passes through the beam current detector and enters the petal accelerator, the beam current detector collects electron beam current information. This current signal is the feedforward signal.

[0011] S3: After the electron beam enters the petal accelerator, the cavity pressure signal sampling device collects the high-frequency cavity sampling signal of the petal accelerator. This sampling signal is the feedback signal.

[0012] S4: The RF low-level control system receives the feedforward signal and the feedback signal, and the RF low-level control system constantly adjusts the amplitude and phase of the excitation signal based on the two types of information;

[0013] S5: The RF low-level control system compensates for changes in the accelerating electric field through feedback signals;

[0014] S6: The RF low-level control system adjusts the excitation signal in advance through the feedforward signal to compensate for the disturbance caused by the beam load.

[0015] Compared with the prior art, the present invention has the following advantages: (1) the present invention uses a beam current intensity detector to measure the electron beam current intensity output by the electron beam source in real time, and accurately obtains the beam load change injected into the petal accelerator; (2) the present invention uses a beam current intensity detector to measure the electron beam current load change, adjusts the amplitude and phase of the excitation signal at the corresponding moment, compensates for the cavity pressure change caused by the beam load fluctuation, and thus maintains the amplitude and phase stability of the accelerating electric field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Reference numerals: 10 - electron beam source; 20 - beam current intensity detector; 30 - deflection magnet; 40 - high frequency cavity; 50 - electron beam current.

[0017] Figure 1 This is a schematic diagram of the position structure of the beam current intensity detector of the present invention.

[0018] Figure 2 The performance curve of the petal accelerator under feedback control only.

[0019] Figure 3 This is the performance curve of the petal accelerator under feedforward signal plus feedback control. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1:

[0022] This embodiment provides a high-power petal accelerator. Figure 1 As shown, it includes an electron beam source 10, a beam current intensity detector 20, a petal accelerator, and a radio frequency low-level control system;

[0023] The electron beam source 10 is arranged outside the petal accelerator, and the electron beam source 10 is used to emit an electron beam 50. The beam current intensity detector 20 is arranged before the electron beam 50 enters the injection port of the petal accelerator, and the beam current intensity detector 20 is used to detect the current intensity of the electron beam 50 output by the electron beam source 10;

[0024] The beam current detector 20 uses a non-intercepting beam current detector, such as an inductive current transformer (such as ICT, FCT, CWCT, etc.) or a beam position detector. These detectors can output a signal positively correlated with the beam current intensity. The parameters used by the beam current detector 20 should meet the following requirements: measurement accuracy within plus or minus one percent; response time less than one microsecond; and adapt to the operating current intensity range during accelerator operation.

[0025] The beam current intensity detector 20 is arranged before the electron beam 50 enters the injection port of the petal accelerator. The beam current intensity detector 20 can measure and transmit the beam current intensity information output by the electron beam source in real time. The beam current intensity change data obtained by the beam current intensity detector 20 enables the subsequent control system to understand the load changes of the electron beam 50 in real time. At the same time, the beam current intensity detector 20 is a feedforward signal in the RF low-level control system.

[0026] Example 2:

[0027] This embodiment is based on the petal accelerator in embodiment 1. Figure 1As shown, the petal accelerator includes a high-frequency cavity 40 and a plurality of deflection magnets 30. The deflection magnets 30 are arranged outside the high-frequency cavity 40. The petal accelerator increases the energy of the electron beam 50 by multiple round-trip acceleration (the final energy is adjusted according to actual application requirements), and accelerates the electron beam 50 to the required energy through the high-frequency cavity 40. A cavity pressure signal sampling device is provided in the petal accelerator to collect the high-frequency cavity signal of the petal accelerator. The cavity pressure signal sampling device in the petal accelerator is generally a radio frequency probe or a coupler. The sampling signal of the cavity pressure signal sampling device is a feedback signal in the radio frequency low-level control system. The petal accelerator adopts known technical design and combines the radio frequency low-level control system to cope with the beam load effect during high-power operation. The working process of the petal accelerator is precisely controlled by the electromagnetic field to achieve acceleration and stabilization of the electron beam.

[0028] Example 3:

[0029] This embodiment is based on the petal accelerator in embodiment 1. Figure 1 As shown, the RF low-level control system receives feedforward signals and feedback signals and adjusts the amplitude and phase of the accelerating electric field in real time. The data of the RF low-level control system comes from the beam current detector 20 and the high-frequency intracavity sampling signal of the petal accelerator. After receiving the feedback signal, the RF low-level control system is used to compensate for the stability of the accelerating electric field. After receiving the feedforward signal, the RF low-level control system adjusts the excitation signal in advance according to the change in the electron beam current 50 reflected by the feedforward signal to compensate for the disturbance caused by the electron beam current 50 load. For the pulse operation mode, the output excitation signal amplitude Ad = Gfb·Aacc+α

[0030] Abeam, which:

[0031] Aacc: the amplitude of the acquired high-frequency cavity signal;

[0032] Abeam: the amplitude of the collected beam current intensity signal;

[0033] Gfb: feedback loop gain;

[0034] α: Calibration coefficient for beam loading effect feedforward control.

[0035] Note: Before beam injection, the beam current intensity is zero (Abeam = 0). At this time, the excitation signal Ad = Gfb·Aacc, which maintains the electric field stability of the high-frequency cavity. After the beam injection begins, the other part of the excitation signal, α·Abeam, is used to compensate for the power loss required by the beam loading effect. Through feedforward control, the cavity pressure disturbance caused by the pulse head can be responded to in advance, ensuring the amplitude and phase stability of the accelerating electric field, thereby improving the stability of the system.

[0036] The present invention also provides a feedforward control method for a high-power petal accelerator, which is characterized by:

[0037] S1: The electron beam source 10 emits an electron beam 50 into the petal accelerator;

[0038] S2: When the electron beam 50 passes through the beam current intensity detector 20 and enters the petal accelerator, the beam current intensity detector 20 collects the current intensity information of the electron beam 50. This current intensity signal is a feedforward signal.

[0039] S3: After the electron beam 50 enters the petal accelerator, the cavity pressure signal sampling device collects the high-frequency cavity sampling signal of the petal accelerator. This sampling signal is the feedback signal.

[0040] S4: The RF low-level control system receives the feedforward signal and the feedback signal, and the RF low-level control system constantly adjusts the amplitude and phase of the excitation signal based on the two types of information;

[0041] S5: The RF low-level control system compensates the stability of the accelerating electric field through feedback signals;

[0042] S6: The RF low-level control system adjusts the excitation signal in advance through the feedforward signal to compensate for the disturbance caused by the beam load.

[0043] The experimental process of this application is as follows:

[0044] Startup process:

[0045] When started, the electron beam source 10 outputs an electron beam 50, which first passes through the beam current intensity detector 20 and then enters the petal accelerator. The beam current intensity detector 20 begins to collect the current intensity information of the electron beam 50, and the beam current intensity detector 20 transmits it to the RF low-level control system in real time.

[0046] By calibrating the conversion coefficient between the electron beam current intensity information and the excitation signal in advance, the RF low-level control system adjusts the excitation signal of the accelerating electric field in real time according to the measured changes in beam current intensity to ensure the stability of the electric field amplitude and phase in the accelerating cavity.

[0047] Operation process:

[0048] During the normal operation of the petal accelerator, the beam current intensity detector 20 continuously monitors the changes in the electron beam current 50 and feeds back the real-time data to the RF low-level control system. The RF low-level control system adjusts the working state of the high-frequency acceleration cavity based on this data to ensure that the electron beam is always accelerated in a stable electric field during the acceleration process.

[0049] The cavity pressure signal sampling device in the petal accelerator outputs a feedback signal to the RF low-level control system, which combines the feedback signal with the feedforward signal to ensure the amplitude and phase stability of the accelerating electric field. Especially in the pulsed operation mode, the RF low-level control system can compensate for the cavity pressure drop caused by the beam load, reduce high-frequency cavity pressure disturbances in advance, and improve the stability of the accelerating electric field.

[0050] End process:

[0051] When the experiment is finished, the RF low-level control system stops collecting the beam current detector 20 and turns off the RF acceleration system. At this time, the RF low-level control system also stops adjusting the accelerating electric field, and the experimental data will be saved for subsequent analysis.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A high-power petal accelerator, characterized by: It includes an electron beam source (10), a beam current intensity detector (20), a petal accelerator, and a radio frequency low-level control system; The electron beam source (10) is arranged outside the petal accelerator, and the electron beam source (10) is used to emit an electron beam (50). The beam current intensity detector (20) is arranged before the electron beam (50) enters the injection port of the petal accelerator, and the beam current intensity detector (20) is used to detect the current intensity of the electron beam (50) output by the electron beam source (10). The radio frequency low-level control system is used to receive a signal sent by the beam current intensity detector (20) when it is working. The radio frequency low-level control system adjusts the excitation signal and the amplitude phase in real time through the signal sent by the beam current intensity detector (20), thereby compensating for the cavity pressure change caused by the beam load fluctuation.

2. The high-power petal accelerator according to claim 1, characterized in that: The petal accelerator comprises a high-frequency cavity (40) and a plurality of deflection magnets (30). The deflection magnets (30) are arranged outside the high-frequency cavity (40). A cavity pressure signal sampling device is arranged inside the petal accelerator to collect the high-frequency cavity signal of the petal accelerator.

3. A feedforward control method for a high-power petal accelerator according to claims 1 to 2, characterized in that: S1: The electron beam source (10) emits an electron beam (50) into the petal accelerator; S2: When the electron beam (50) passes through the beam current intensity detector (20) and enters the petal accelerator, the beam current intensity detector (20) collects the electron beam current (50) current intensity information, and this current intensity signal is a feedforward signal; S3: After the electron beam (50) enters the petal accelerator, the cavity pressure signal sampling device collects the high-frequency cavity sampling signal of the petal accelerator, and the sampling signal is the feedback signal; S4: The RF low-level control system receives the feedforward signal and the feedback signal, and the RF low-level control system constantly adjusts the amplitude and phase of the excitation signal based on the two types of information; S5: The RF low-level control system compensates for changes in the accelerating electric field through feedback signals; S6: The RF low-level control system adjusts the excitation signal in advance through the feedforward signal to compensate for the disturbance caused by the beam load.

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