Pulse Picking by Resonant Excitation (PPRE) enables synchrotron facilities to provide single-bunch light for timing users without interrupting multi-bunch operation*. We report the first vertical-plane PPRE tests at Diamond using the Multi-Bunch Feedback system, achieving vertical bunch-size growth and measurable X-ray enlargement. A simple novel optimisation improved PPRE purity by reducing the baseline emittance. Beyond readily-available diagnostics, we demonstrate how crystallographic diffraction can be used as a user-relevant method to characterise PPRE with statistically significant evidence of isolating a single excited bunch. Together, these methods provide a practical and user-orientated framework for synchrotron facilities considering similar timing-mode capabilities.

The KEK e⁺/e⁻ Linac supplies electron beams to SuperKEKB HER, PF, and PF-AR, and positron beams to SuperKEKB LER. We utilize machine learning for both online beam tuning and offline data analysis. Machine learning based on Bayesian optimization has been employed to improve and maintain beam quality, contributing to the enhancement and stabilization of beam injection efficiency into SuperKEKB HER and LER. In this report, we present monitors and beam tuning methods that incorporate machine learning. Identifying parameters that affect beam quality and stability is important, but finding them among the vast number of parameters is not easy. In machine learning-based beam tuning, selecting the appropriate parameters for tuning is crucial, and another important issue is identifying factors that lead to beam instability. To address this, we have applied explainable AI techniques to analyze archived data and attempted to extract parameters that have a significant impact on the beam. This report also covers our data archiving system and analysis efforts using explainable AI.

With the high current physical operations of the upgraded Beijing Electron–Positron Collider (BEPCII), thresholds on collision luminosity and beam current have been presented due to various factors such as collision background, noise, equipment stability under high power operation, and so on. One of the most serious influences on beam dynamics was beam instability which has been clearly exhibited. The comprehensive experimental investigation of beam instabilities in BEPCII is an indispensable part of beam physics research and can provide references for the upgrade project of BEPCII. Over the past two years, the experimental investigation of beam instabilities in BEPCII has been carried on with the single and multiple bunch filling in the storage ring. With the optimization of the bunch-bunch feedback system, the designed collision luminosity , 1.0x10^33cm^-2s^-1 was achieved during the physical operation and the primary process on configuration of Feedback system will be introduced. For comprehensive understanding the feedback system, a physical model is developed and analysis is conducted to demonstrate the relationship between feedback capability and various parameters. This comprehensive physical model and analysis of the practical feedback system may provide valuable insights into the optimization of the feedback system.

Diamond-II will require two types of stripline kickers during normal operation: the kicker actuators for the transverse multibunch feedback system; and the injection stripline kickers which enable transparent injection. Both are very similar in design as they need to kick individual bunches without disturbing the following bunches. The main difference is the voltage requirements. The feedback kicker is expected to be driven with a maximum peak voltage of ~100 V using a broadband power amplifier, whereas the injection stripline kicker is driven with a trapezoid voltage signal with a maximum peak voltage of 20 kV using a dedicated power supply. This paper will describe the design and prototyping for both stripline kickers along with discussion of the required steps to get to final designs for each type.

NanoTerasu is a 3 GeV light source newly constructed in Sendai, Japan. The circumference is 349 m and the natural emittance is 1.1 nm rad, which is realized by a double-double-bend achromat lattice. The commissioning of the storage ring started in June 2023. The longitudinal instability was observed when the stored beam current reached 150 mA in August 2023. The temperature of RF cavity was adjusted to suppress the instability. The user operation was started on schedule in April 2024 with a stored beam current of 160 mA. The stored beam current was reached 200 mA without the beam instability in July 2024. The stored beam current at user operation period was limited to 200 mA by the longitudinal instability. We try to suppress the longitudinal beam instability using several methods. We developed the pillbox type RF kicker cavity to suppress the instability. In addition, we tried to suppress the longitudinal instability using the transverse feedback kicker. I will report the status of longitudinal instability suppression at NanoTerasu.

The bunch-by-bunch feedback system is now an key function in high-current, multi-bunch storage rings to suppress coupled-bunch instability and/or to reduce the effects of injection vibration. In high-luminosity e+e- colliders such as SuperKEKB, strong beam-beam interactions occur due to collisions, which usually introduce very wide frequency response on the transverse bunch motion far out of the betatron tune. In vertical plane it may cause increase of the beam size which has a large impact on the luminosity. In this presentation, we will present the principle and configuration of our bunch feedback system, the cause of the side effects of the bunch feedback system, and several trials to overcome them.

The Diamond-II upgrade will enhance the performance of the Diamond Light Source synchrotron, including improved beam stability by the Fast Orbit Feedback system. Achieving the targeted closed-loop bandwidth of 1 kHz necessitates an open-loop actuator bandwidth of approximately 10 kHz, which presents significant design challenges for the corrector magnet vacuum vessel. Additionally, subsystems such as the corrector magnet power supplies and Beam Position Monitors, must comply with a stringent closed-loop latency of less than 100 microseconds. Initially, a 1 millimetre stainless steel vessel was deemed viable; however, experimental findings indicated that the combination of stainless steel and neighbouring copper vessels resulted in a decrease in both integrated magnetic field strength and system bandwidth. This prompted a reassessment of the material selection for the fast corrector vessels to optimise orbit feedback performance. This paper investigates these challenges, analyses experimental data, and explores solutions to achieve the necessary bandwidth for the Diamond-II upgrade.

The Electron Ion Collider (EIC) requires an electron cooler operating at the EIC injection energy to obtain the design proton beam emittances. A non-magnetized RF-based electron cooler, the EIC Low Energy Cooler (LEC), is currently under design. It will be operating at γ-factor 25 and will be delivering 70 mA electron current to a 170 m long cooling section (CS). To obtain required cooling an input from electron-proton relative trajectory misalignment into an overall angles in the cooling section must be kept below 15 urad. In this paper we give comprehensive consideration of the factors affecting the trajectory angles and set the resulting requirements to various CS subsystems.

The Low Energy RHIC Electron Cooler (LEReC), the world’s first RF-based non-magnetized electron cooler successfully provided cooling of gold ions at γ-factors 4.1 and 4.9 during RHIC Runs 2019-2021, substantially increasing RHIC luminosity. Since then, LEReC has been routinely used for numerous cooling studies. Development of trajectory and energy feedbacks for electron beam was an important step in achieving the optimized cooling in LEReC. This paper summarizes our experience with design, commissioning and operation of the LEReC feedback systems.

The SOLARIS synchrotron light source has commissioned a transverse bunch-by-bunch feedback system designed to suppress coupled-bunch instabilities and serve as a diagnostic tool for accelerator studies. The system was successfully installed and integrated with the existing infrastructure, including timing and control systems. After a series of commissioning steps, it was brought into operation and tested under standard user conditions. Although routine instability suppression is not currently needed during regular operation, the system has been effectively used in dedicated machine studies. It enabled detailed observation of transverse bunch motion, instability spectra, and individual bunch tune measurements. The system also played a crucial role in advanced measurements such as LOCO experiments with selectively emptied buckets and tune shift studies under varying machine conditions. The bunch-by-bunch feedback system significantly enhances the diagnostic and research capabilities at SOLARIS and provides a solid foundation for potential future applications in active beam stabilization.

SIRIUS, the Brazilian 4th generation synchrotron light source, has been in operation since 2020. Over time, insertion devices (IDs) are expected to populate its straight sections. To supress edge effects from undulators and support overall beam stability, a feedforward correction system is currently available through EPICS layer for the first installed ID. However, performance could be improved by adopting a lower-level solution with higher actuation rates and reduced jitter. To address this, a new approach has been developed using hardware technology already available: control system nodes based on BeagleBone Black platform, which integrates both embedded linux and dedicated real-time processors within the same SoC. This setup enables current setpoints updates at rates up to 1 kHz and aiming to be scalable. This paper presents an overview of the system's architecture and objectives, first results with IVU and VPU undulators as well as future developments and improvements.

At Diamond, it was previously observed that the response of the beam changes with mode number when excited by the transverse multi-bunch feedback (TMBF). This study presents the results of various experimental campaigns carried out to investigate the behaviour of tune-sweep waveforms for a variety of stored beam conditions and TMBF settings. We demonstrate that it is unlikely that wakefields cause the mode dependence in the output TMBF waveforms. Investigations to explain what is causing the mode-dependent behaviour are ongoing.

This work presents the development and experimental validation of a control system for synchrotron X-ray beam stabilization. A laboratory-scale replica of a beamline was constructed using an analog oscilloscope to emulate beam dynamics. Electrical actuation was implemented via deflection plates, while disturbances were introduced using an electromagnet. Beam position monitoring was performed through a 2×2 photodiode matrix, replicating the functionality of X-ray Beam Position Monitors (XBPMs). System identification through steady-state and transient analysis resulted in a first-order linear dynamic model relating input voltages to beam position. A PI controller was designed based on this model, and experimental validation demonstrated the controller’s effectiveness in maintaining beam stability under position drift conditions—typical disturbances during X-ray Absorption Spectroscopy (XAS) experiments—achieving a control frequency of 1 kHz, limiting the steady-state error to below 0.2% of the total drift. The proposed approach provides a foundation for the development of high-performance control systems for synchrotron beamlines, with potential application to operational facilities.

The High Energy Photon Source (HEPS) is the fourth-generation synchrotron light source with a beam energy of 6 GeV, developed by the Institute of High Energy Physics. As a essential partment of the HEPS, The Fast Orbit Feedback (FOFB) systemhas been developed to maintain the beam orbit stability. In this work, a neural network-based algrithm has been designed and developed to replace the tradional PID control algrithm of FOFB. In this papaer, we have introduced the design and developmenyt of the MLP neural network, which has been trained using operational data from HEPS, and hyperparameter optimization was conducted to improve performance. The trained model was then quantized to support deployment on FPGA hardware. A laboratory test environment was set up, where BPM data was fed into the neural network, and the corrected values for the corrector magnets were output after computation. Experimental results show that the neural network maintained a control error of approximately 1 mA. These results demonstrate the feasibility of using neural networks as an effective alternative to PID control in FOFB systems.

The Super Tau-Charm Facility (STCF), a third-generation electron-positron collider operating in the tau-charm energy region, will be subject to mechanical disturbances and ground vibrations, which can lead to beam-beam misalignments at the interaction point (IP). Such misalignments degrade luminosity and shorten beam lifetime. To maintain an optimum beam collision condition, the development of a high-performance collision feedback system is therefore essential for suppressing orbit offsets at the IP. This study first analyzes the primary sources of orbit perturbations and evaluates the feasibility of three candidate feedback signals for monitoring IP beam offsets in the STCF collision system from the perspective of detection principles. Finally, a preliminary design of the collision feedback system is proposed based on the STCF's performance requirements.

A new orbit feedback system has been introduced to the PF-ring, a synchrotron radiation source at KEK, starting from the third operation period of FY2024. The new system is built with state-of-the-art digital signal processing circuits based on the MicroTCA.4 standard. The stored beam’s closed orbit distortion (COD) is measured at a 10 kHz rate using the circuits matched to the number of BPMs, and corrected to a designated reference orbit by feeding back the results of matrix calculations using the inverse response matrix to the currents of fast steering magnets. The transition from the legacy VME-based system, which had been in service for nearly 30 years, was carried out carefully and stepwise during the startup phase of the third operation period. The reference orbit was successfully transferred to the new system, and even in-vacuum undulators with a minimum gap of 4 mm were operated without requiring additional orbit corrections. In this presentation, we will describe the setup of the newly implemented system, the transition process from the old system, and plans for future improvements.

A model-based optimal control approach has been developed for the slow orbit feedback (SOFB) system to enhance orbit stability in the Siam Photon Source (SPS) storage ring. The control strategy utilizes a linear quadratic regulator (LQR) based on a multi-input, multi-output (MIMO) state-space model of the linear SPS storage ring, derived through system identification using MATLAB and SIMULINK. The necessary and sufficient conditions for controllability and boundedness of the dynamic system are established. Experimental simulations were conducted to assess the performance of the LQR controller in a practical SPS storage ring. The results demonstrate that the proposed control method effectively minimizes the quadratic cost function and error signals between setpoints and process variables for both horizontal and vertical orbit positions while ensuring system stability and robustness. The study also outlines the fundamental principles of optimal control theory, system identification, and future development directions.

This paper presents the enhancement of photon beam position stability at the Siam Photon Source (SPS) synchrotron through a real-time feedback control system incorporating a fault-tolerant control (FTC) algorithm. The system utilizes Photon Beam Position Monitor (pBPM) measurements within a global orbit feedback loop to minimize beam position fluctuations. The FTC algorithm plays a critical role in ensuring system reliability by detecting and compensating for disturbances, sensor errors, and actuator faults, maintaining stable beam conditions under varying operational scenarios. Experimental results demonstrate that the FTC-based feedback system significantly reduces photon orbit deviations, improving synchrotron radiation quality. By enhancing robustness and adaptability, the control system ensures precise beam positioning, making the SPS more reliable for scientific and industrial applications requiring high beam stability.

Shifting RF phases is a common task in particular at particle accelerators. Which RF frequencies need to be shifted is highly facility dependent, which demands a wide range phase shifter. The phase shifter presented in this contribution consists of a custom board, that includes a high-performance quadrature modulator, voltage regulators and an 16-bit digital-to-analogue converter that offers an I2C interface. The quadrature modulator is specified to work in the frequency range between 50 MHz and a 6 GHz. The board is combined with commercial off-the-shelf products to provide a software interface and a RF tight compact housing. We present amplitude and phase noise measurements and amplitude stability measurements. At the ELBE Center for High-Power Radiation Sources we use the phase shifter to shift the phase of the superconducting RF gun laser with respect to the accelerator cavity RF field. This allows to implement a feedback loop that stabilizes the THz output power of the THz undulator source at ELBE. In order to achieve this, the beam position is monitored in an energy dispersive beam line section and the gun laser phase is used to keep it constant.

The Korea-4GSR (4th Generation Synchrotron Radiation Source) is under construction since 2021 to be a state-of-the-art research facility requiring exceptional stability for its electron beam to ensure high-quality experimental data. Ground vibrations originating from both natural and artificial sources can significantly impact the stability of critical components, particularly the accelerator and beamline elements. To assess the potential influence of these vibrations, we conducted comprehensive ground vibration measurements at the Korea-4GSR construction site. This study was performed with the sensitive accelerometer at various locations across the construction site to characterize the amplitude and frequency content of the ambient vibrations. The collected data were analyzed to evaluate the potential impact on the beam stability, considering the vibration tolerance levels of key accelerator components. This paper presents the preliminary findings of our ground vibration measurements, discussing the observed vibration characteristics and their implications for maintaining the high level of beam stability required for the successful operation of the Korea-4GSR.

The CSNS RCS (Rapid Cycling Synchrotron) is a proton accelerator designed to achieve a target beam energy of 1.6 GeV, with a typical operating intensity of 140 kW, which is expected to increase to 500 kW after the CSNS II upgrade. However, a significant current instability has been observed during the 100 kW beam operation. To mitigate this instability, techniques such as operational tuning and chrominance modulation were previously used to make the 100 kW beam operate stably. In order to face the subsequent stronger instability, a bunch-by-bunch transverse feedback system is required to mitigate the coherent lateral oscillations caused by instability and injection errors. In this paper, the preliminary design of the feedback system will be presented.

The advent of 4th generation synchrotron light sources has placed unprecedented demands on beam stability, requiring sub-micron orbit control to fully exploit their ultra-low emittance and high-brightness capabilities. This tutorial explores orbit stability, covering sources of perturbations like magnet misalignments, ground vibrations, and power supply fluctuations, as well as correction algorithms used to mitigate their effects. One focus of the tutorial will be on advances in simulations, which have played a crucial role in optimizing the design and performance of subsystems as well global mode space analysis. Various correction techniques, including slow and fast orbit feedback systems, beam-based girder alignment, and the integration of XBPMs into the electron beam control system, will also be discussed to improve long-term beam stability and performance. Real-world examples from leading 4th-generation facilities will highlight how advanced orbit control strategies and cutting-edge hardware have enabled the achievement of remarkable orbit correction bandwidths, significantly enhancing electron beam stability