A lateral feedback excitation device with high shunt impedance and horizontal light extraction

Abstract

This invention discloses a transverse feedback excitation device with high shunt impedance and horizontal light extraction, belonging to the field of particle accelerator technology. The device includes a beam position detector (BPM), an RF front-end, an ADC module, a digital signal processing module, a DAC module, a power divider, a power amplifier, a low-pass filter, an exciter (Kicker), and matching loads. The exciter (Kicker) has four parallel electrode strips located on both sides of the beam centerline, with two strips on the same side connected in parallel. Each electrode has a characteristic impedance of 100Ω, resulting in an equivalent total characteristic impedance of 50Ω after parallel connection. The four electrode strips are symmetrically distributed at the four corners within the vacuum chamber cross-section, avoiding the horizontal midplane to form an open optical path. This invention improves the shunt impedance of the exciter, reduces the RF power requirement, achieves impedance matching with a standard 50Ω system, and ensures unobstructed horizontal extraction of synchrotron radiation light.

Description

Technical Field

[0001] This invention relates to the field of particle accelerator technology, and in particular to a transverse feedback excitation device with high shunt impedance and horizontal light extraction. Background Technology

[0002] In the transverse feedback system of a particle accelerator, shunt impedance is a core physical indicator for evaluating kicker performance. According to electromagnetic field theory, transverse shunt impedance is directly proportional to the characteristic impedance of the electrodes, and current technologies typically employ a matching scheme with a single 50Ω impedance electrode. However, under specific vacuum pipe conditions, especially for vacuum pipes with non-four-fold symmetry structures (such as racetrack-shaped vacuum chambers), the horizontal dimension is relatively wide. The traditional arrangement of two opposing electrodes leads to a significant increase in the electrode spacing, resulting in a substantial decrease in shunt impedance, making it difficult to improve the horizontal shunt impedance.

[0003] To compensate for the aforementioned insufficient excitation efficiency, the system must be equipped with a higher output power radio frequency (RF) power amplifier to meet the target excitation voltage requirements. In practical engineering, the RF power amplifier is one of the most expensive components in the feedback system, and its cost is not linearly proportional to its output power. The increase in power level is often accompanied by an exponential or stepwise increase in R&D difficulty, heat dissipation requirements, power system complexity, and the cost of core components, leading to a surge in system construction budget and a significant deterioration in economic efficiency.

[0004] Furthermore, for synchrotron accelerator storage rings, synchrotron radiation typically exits horizontally, and traditional horizontal kicker structures often obstruct the exit path of the synchrotron radiation. If electrode layout space is sacrificed to avoid optical path obstruction, the shunt impedance will be further reduced, thus trapping the system in a vicious cycle of low efficiency, high power demand, and high cost, making it difficult to simultaneously meet the engineering requirements of high shunt impedance and horizontal optical path openness. Summary of the Invention

[0005] The purpose of this invention is to provide a transverse feedback excitation device with high shunt impedance and horizontal light extraction. It aims to solve the technical problems of low excitation efficiency, high cost of high-power amplifiers, and obstruction of horizontal mid-plane synchronous light extraction in the existing 50Ω matching scheme by adopting a four-band parallel structure with a high characteristic impedance of 100Ω.

[0006] To achieve the above objectives, the present invention provides a lateral feedback excitation device with high shunt impedance and horizontal light extraction, comprising: A beam position detector (BPM) measures the beam oscillation signal. An RF front-end, electrically connected to the BPM, receives the beam signal and amplifies and filters it. An ADC module, electrically connected to the RF front-end, converts the beam signal into a digital signal. A digital signal processing module, electrically connected to the ADC module, performs digital signal processing and generates an excitation signal. A DAC module, electrically connected to the DAC module, performs digital-to-analog conversion. A power divider, electrically connected to the DAC module, adjusts the phase distribution of the excitation signal. A power amplifier, electrically connected to the power divider, amplifies the excitation signal as needed. A low-pass filter, electrically connected to the power amplifier, eliminates high-frequency noise. An exciter, Kicker, electrically connected to the low-pass filter, applies lateral feedback excitation to the beam. A matching load, 50Ω in this embodiment, is electrically connected to the Kicker. The exciter Kicker has four electrodes, including a first electrode bar, a second electrode bar, a third electrode bar, and a fourth electrode bar. The first electrode bar and the second electrode bar are located on one side of the beam center line, are parallel to each other, and are connected in parallel. The third electrode bar and the fourth electrode bar are located on the other side of the beam center line, are parallel to each other, and are connected in parallel. The four electrodes are symmetrically distributed at the four corners within the cross-section of the vacuum chamber, avoiding the horizontal mid-plane of the vacuum chamber, so as to form an open optical path channel in the horizontal mid-plane; the characteristic impedance of each electrode bar in the out-of-phase working mode is 100Ω, and the equivalent total characteristic impedance of two electrode bars connected in parallel on the same side is 50Ω.

[0007] Preferably, the upstream ports of the four electrode kickers are connected to a 50Ω matching load, and the downstream ports are electrically connected to a power amplifier via a low-pass filter.

[0008] Preferably, four kickers with electrodes are installed in a racetrack-shaped vacuum chamber that is not symmetrical about four folds.

[0009] Preferably, the electrode length of the four kickers is 1 / 4 wavelength corresponding to the center frequency of the operating frequency band.

[0010] Preferably, the beam position detector (BPM) and the four strip electrodes (Kicker) are both located at points where the accelerator's β function is relatively large.

[0011] Preferably, each of the four electrode strips with electrode kickers has a preset electrode angle, which is determined according to the geometric boundary of the vacuum chamber cross section, so as to maintain impedance matching between the electrode and the vacuum chamber wall while increasing the shunt impedance.

[0012] Preferably, the open optical path is configured to allow synchrotron radiation to exit the vacuum chamber horizontally without obstruction.

[0013] The advantages and beneficial effects of this invention compared to the prior art are: 1. The shunt impedance is doubled. By utilizing the physical property that the shunt impedance is proportional to the characteristic impedance of the electrode, and by designing the single-channel strip to be 100Ω and realizing vector superposition, the horizontal shunt impedance is increased by about 100Ω compared to the traditional single-channel 50Ω scheme.

[0014] 2. Significantly reduce power amplifier costs: Since the cost of power amplifiers increases non-linearly with the increase of output power (doubling the power requirement usually results in more than doubling the cost), this invention improves the excitation efficiency of the Kicker hardware itself, so that the system only needs a lower power amplifier to achieve the predetermined excitation effect, thereby greatly reducing the construction and maintenance costs of the system while ensuring feedback performance.

[0015] 3. Excellent impedance matching and high-frequency performance: Precise impedance matching: The parallel connection of two 100Ω strips is achieved through the bus structure inside the vacuum chamber, and its total input characteristic impedance is exactly matched to the standard 50Ω system, ensuring seamless connection with standard power amplifiers and transmission feeders.

[0016] 4. Low reflection characteristics: Simulation verification shows that after proper matching, the port reflection parameters of this structure are all less than 10% under harmonic excitation, which effectively avoids power back reflection caused by impedance mismatch, protects the power amplifier and improves the effectiveness of power loading.

[0017] 5. Excellent engineering compatibility and physical openness: Avoiding obstruction of synchrotron light: Four strips are symmetrically distributed in the four "corner" regions of the vacuum chamber cross-section, keeping the horizontal midplane physically open. This structure ensures that synchrotron radiation light can pass through the gaps between the electrodes without obstruction, resolving the sharp contradiction in spatial layout between the horizontal excitation components and the high-throughput optical path.

[0018] 6. Adaptable to asymmetric vacuum chambers: This invention specifically solves the technical problem of extremely low excitation efficiency in the horizontal direction of non-four-fold symmetric vacuum pipes, such as racetrack-shaped pipes, due to the long distance of the pipe wall (e.g., the 90mm clear area in SSRF). Its design concept also has broad applicability and can be applied to symmetric structures such as circles or squares, so as not to obstruct the extraction of synchrotron light in the horizontal direction, and to further pursue extremely high feedback efficiency and system redundancy.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a transverse feedback excitation device with high shunt impedance and horizontal light extraction according to an embodiment of the present invention. Figure 2This is a schematic diagram of a runway-shaped vacuum pipeline in an embodiment of the present invention; Figure 3 A schematic diagram of a traditional 2-electrode kicker; Figure 4 This is a diagram showing the electric and magnetic field distributions after applying a feedback signal in an embodiment of the present invention. Figure 5 This is a diagram of the port reflection coefficients of the horizontal Kicker in the out-of-phase mode in this embodiment of the invention; Figure 6 This is a diagram of the port reflection coefficients of the vertical Kicker in the out-of-phase mode in this embodiment of the invention. Figure 7 This is a Mafia simulation result of the horizontal Kicker shunt impedance in an embodiment of the present invention; Figure 8 This is a Mafia simulation result of the Kicker shunt impedance in the vertical direction in an embodiment of the present invention. Detailed Implementation

[0021] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing the 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. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] This invention proposes a four-electrode kicker device for accelerator lateral feedback systems, particularly suitable for non-four-fold symmetrical vacuum chamber structures (e.g., racetrack-type). This device optimizes the electrical connections of the electrodes and matches their characteristic impedance without altering the external power supply system. Under the premise of significantly improving the horizontal shunt impedance.

[0023] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the present invention provides a lateral feedback excitation device with high shunt impedance and horizontal light extraction, comprising: Beam position detector (BPM) is used to measure beam oscillation signals; The RF front end is electrically connected to the beam position detector (BPM) and is used to receive beam signals and perform amplification and filtering. The ADC module, electrically connected to the RF front end, is used to convert the beam signal into a digital signal; The digital signal processing module, electrically connected to the ADC module, is used to perform digital signal processing and generate excitation signals; The DAC module, electrically connected to the digital signal processing module, is used for digital-to-analog conversion; The power divider, electrically connected to the DAC module, is used to adjust the phase distribution of the excitation signal; A power amplifier, electrically connected to the power divider, is used to amplify the excitation signal as needed. A low-pass filter, electrically connected to the power amplifier, is used to eliminate high-frequency noise; The exciter, Kicker, is electrically connected to the low-pass filter and is used to apply transverse feedback excitation to the beam. The matching load, which is 50Ω in this embodiment, is electrically connected to the exciter Kicker. The exciter Kicker has four electrodes, including a first electrode bar, a second electrode bar, a third electrode bar, and a fourth electrode bar. The first electrode bar and the second electrode bar are located on one side of the beam center line, are parallel to each other, and are connected in parallel. The third electrode bar and the fourth electrode bar are located on the other side of the beam center line, are parallel to each other, and are connected in parallel. The four electrodes are symmetrically distributed at the four corners within the cross-section of the vacuum chamber, avoiding the horizontal mid-plane of the vacuum chamber, so as to form an open optical path channel in the horizontal mid-plane; the characteristic impedance of each electrode bar in the out-of-phase working mode is 100Ω, and the equivalent total characteristic impedance of two electrode bars connected in parallel on the same side is 50Ω.

[0025] Preferably, the upstream ports of the four electrode kickers are connected to a 50Ω matching load, and the downstream ports are electrically connected to a power amplifier via a low-pass filter.

[0026] Preferably, four kickers with electrodes are installed in a racetrack-shaped vacuum chamber that is not symmetrical about four folds.

[0027] like Figure 2 As shown, the vacuum tube is shaped like a racetrack, with particles passing through the center (from the inside out). The kicker consists of a pair of parallel electrode plates on the left and right sides. Ports 1 and 4 are connected upstream to a 50Ω matching resistor, and ports 2 and 3 are connected downstream to the excitation signal.

[0028] Preferably, the electrode length of the four kickers is 1 / 4 wavelength corresponding to the center frequency of the operating frequency band.

[0029] Preferably, the beam position detector (BPM) and the four strip electrodes (Kicker) are both located at points where the accelerator's β function is relatively large.

[0030] Preferably, each of the four electrode strips with electrode kickers has a preset electrode angle, which is determined according to the geometric boundary of the vacuum chamber cross section, so as to maintain impedance matching between the electrode and the vacuum chamber wall while increasing the shunt impedance.

[0031] Preferably, the open optical path is configured to allow synchrotron radiation to exit the vacuum chamber horizontally without obstruction.

[0032] Preferred, such as Figure 3 As shown, this is a traditional 2-electrode kicker.

[0033] Preferred, such as Figure 4 As shown, the feed signals from the left and right sides of the Kicker in this application are 180° out of phase. The excited electric field distribution (top) has a horizontal electric field at the center, providing a horizontal excitation direction for the particle. The excited magnetic field distribution (bottom) has a magnetic field distribution at the center, with the magnetic force direction being horizontal and consistent with the electric force direction.

[0034] This application employs a four-electrode parallel structure with 100Ω electrodes, significantly improving the horizontal shunt impedance compared to the traditional single-channel 50Ω solution. This substantially reduces the RF power requirement under the same excitation voltage, effectively saving on the procurement and maintenance costs of the power amplifier. The equivalent total characteristic impedance after parallel connection of the two electrodes on the same side is 50Ω, achieving precise matching with standard RF power amplifiers and feeders, effectively suppressing power back reflection and improving loading efficiency. Simultaneously, the four electrodes are symmetrically distributed at the four corners and avoid the horizontal midplane of the vacuum chamber, ensuring unobstructed extraction of synchrotron radiation in the horizontal direction. This structure is particularly suitable for non-four-fold symmetrical vacuum pipes such as racetrack-shaped ones, effectively overcoming the sharp impedance attenuation caused by large horizontal apertures, and possessing good engineering versatility.

[0035] The system implementation of the present invention will be described in detail below with reference to specific embodiments.

[0036] The Shanghai Synchrotron Radiation Facility (SSRF) uses stripline electrodes as kickers in its transverse feedback system. The kickers in the x and y directions are placed separately, allowing them to be positioned where the accelerator's β function is higher, thus strengthening the excitation signal. The two kickers are mounted at both ends of the injection line section ID01, with the beam clarity region at 90mm in the x direction and 26mm in the y direction. The vertical kicker is designed as two vertically opposed flat electrodes with a 26mm spacing. To improve the shunt impedance, the horizontal kicker is designed as a four-electrode structure, with electrodes on the same side connected in parallel to establish the horizontal excitation field. The characteristic impedance of the kickers was simulated using Mafia software, with the kickers operating in out-of-phase mode. For the vertical kicker, the characteristic impedance should be matched to 50Ω; for the horizontal kicker, the characteristic impedance of each strip electrode in out-of-phase mode should be matched to 100Ω, with a total impedance of 50Ω after the two electrodes are connected in parallel. The characteristic impedance distribution and port reflection coefficient of the two kickers in out-of-phase mode are shown in [reference needed]. Figure 5 and Figure 6 .

[0037] As can be seen, after correctly matching the characteristic impedance of the strip electrode, the port reflection parameter of the vertical Kicker does not exceed 5% within the operating bandwidth of 0-250MHz, meaning that less than 0.25% of the excitation power is reflected. Due to the connection issue between the two electrodes, the reflection parameter of the horizontal Kicker is about 17% around 100MHz when excited by Gauss pulses, but the reflection parameter is less than 10% when excited by harmonics.

[0038] Considering that the lateral feedback system operates within a bandwidth of 100kHz–250MHz, SSRF selected a 300mm long strip electrode as the kicker for the lateral feedback system. Mafia simulation results for the lateral excitation voltage and lateral shunt impedance are as follows: Figure 7 and Figure 8 As shown in the figure. Simulation results show that when the Kicker shape factor is 1.0, the lateral shunt impedances in the horizontal and vertical directions reach approximately 14.3kΩ and 21.6kΩ, respectively, at 250MHz. The advantages of this design are particularly significant in asymmetric apertures. It is known that the beam clarity region of this scheme has dimensions of 90mm in the horizontal direction and 26mm in the vertical direction (aperture ratio of approximately 3.46). If a traditional design is used, the lateral shunt impedance is inversely proportional to the square of the electrode spacing, which will result in an impedance ratio of approximately 12 times in the vertical direction. However, with the high shunt impedance design of this paper, this ratio is successfully reduced to approximately 1.5 times (21.6 / 14.3), effectively overcoming the sharp impedance attenuation caused by the large horizontal aperture, and significantly improving the lateral shunt impedance and overall excitation efficiency.

[0039] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A lateral feedback excitation device with high shunt impedance and horizontal light extraction, characterized in that, include: A beam position detector (BPM) measures the beam oscillation signal. An RF front-end, electrically connected to the BPM, receives the beam signal and amplifies and filters it. An ADC module, electrically connected to the RF front-end, converts the beam signal into a digital signal. A digital signal processing module, electrically connected to the ADC module, performs digital signal processing and generates an excitation signal. A DAC module, electrically connected to the DAC module, performs digital-to-analog conversion. A power divider, electrically connected to the DAC module, adjusts the phase distribution of the excitation signal. A power amplifier, electrically connected to the power divider, amplifies the excitation signal as needed. A low-pass filter, electrically connected to the power amplifier, eliminates high-frequency noise. An exciter, Kicker, electrically connected to the low-pass filter, applies lateral feedback excitation to the beam. A matching load, 50Ω, is electrically connected to the Kicker to match its characteristic impedance and reduce signal reflection. The exciter Kicker has four electrodes, including a first electrode bar, a second electrode bar, a third electrode bar, and a fourth electrode bar. The first electrode bar and the second electrode bar are located on one side of the beam center line, are parallel to each other, and are connected in parallel. The third electrode bar and the fourth electrode bar are located on the other side of the beam center line, are parallel to each other, and are connected in parallel. The four electrodes are symmetrically distributed at the four corners within the cross-section of the vacuum chamber, avoiding the horizontal mid-plane of the vacuum chamber, so as to form an open optical path channel in the horizontal mid-plane; the characteristic impedance of each electrode bar in the out-of-phase working mode is 100Ω, and the equivalent total characteristic impedance of two electrode bars connected in parallel on the same side is 50Ω.

2. The lateral feedback excitation device with high shunt impedance and horizontal light extraction according to claim 1, characterized in that, The upstream ports of the four electrode kickers are connected to the 50Ω matching load, and the downstream ports are electrically connected to the power amplifier via the low-pass filter.

3. The lateral feedback excitation device with high shunt impedance and horizontal light extraction according to claim 2, characterized in that, The four electrode kickers are installed in a non-four-fold symmetrical vacuum chamber.

4. The lateral feedback excitation device with high shunt impedance and horizontal light extraction according to claim 3, characterized in that, The electrode length of the four Kickers is 1 / 4 wavelength corresponding to the center frequency of the operating frequency band.

5. A lateral feedback excitation device with high shunt impedance and horizontal light extraction as described in claim 4, characterized in that, The beam position detector (BPM) and the four strip electrodes (Kicker) are both located at points where the accelerator's β function is relatively large.

6. A lateral feedback excitation device with high shunt impedance and horizontal light extraction as described in claim 5, characterized in that, Each of the four electrode kickers has a preset electrode angle, which is determined according to the geometric boundary of the vacuum chamber cross section, so as to maintain impedance matching between the electrode and the vacuum chamber wall while increasing the shunt impedance.

7. A lateral feedback excitation device with high shunt impedance and horizontal light extraction as described in claim 6, characterized in that, The open optical path is configured to allow synchrotron radiation to pass through the vacuum chamber horizontally without obstruction.

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