Liquid metal technology is key to the next-generation high-power hadron facilities. Following early R&D collaboration between Argonne National Laboratory and Michigan State University, FRIB pioneered the technology of liquid lithium thin film and is the first in the world applying such technology in accelerator operations. FRIB uses a liquid lithium film for the charge stripping of high-power heavy-ion beams, enabling FRIB to achieve world’s highest power uranium beam on target. Liquid lithium technology has been successfully applied to the liquid lithium charge stripper for FRIB operations, offering a superior choice for charge stripping of high-power heavy ion beams including uranium. Valuable experience has been gained in the performance and maintenance. This talk focuses on operational experience, lessons learned and future improvements.

The polarization of the gamma-ray beam plays a critical role in experimental photonuclear research by probing angular momentum. For example, the multipolarities of the 80Se(g,n)79Se reaction can be assigned by measuring cross-sections relative to the plane of polarization*. Dynamic control over gamma beam polarization will open new opportunities in nuclear research, particularly by allowing relative asymmetries to be calculated without the uncertainty introduced by relative detector efficiency. A gamma-ray beam with rotational linear poarization and high polarization purity (Plin ~ .99) has been demonstrated at the High Intensity Gamma-ray Source (HIGS)**. Without active tuning by an accelerator physicist, polarization quality is degraded due to decoupling of the free-electron laser (FEL) axis and the electron beam orbit. The FOAMS is an active feedback system that is sensitive to the small centroid motions of the FEL optical axis. Measurement uncertainty characterization has been conducted. Ongoing work will utilize this feedback system to automatically sustain controllable gamma-ray polarization for nuclear physics experiments.

Local coupling correction in Interaction Regions (IRs) and global coupling correction based on Base-Band Tune (BBQ) measurement have been performed routinely for RHIC operation. However, one still observes significant residual local coupling measured by beam position data. For the Electron-Ion Collider (EIC) project, betatron decoupling for the hadron beam needs to be improved to maintain a large horizontal to vertical beam emittance ratio (12:1). In this paper, we will analyze the cause for noticeable residual coupling in RHIC and propose an integrated local and global betatron coupling correction based on beam position measurements. We will also present experimental results from ML-based optimization of the local and global coupling in RHIC.

In the coming decades, numerous designs for new accelerator-based facilities, or potential upgrades to current facilities, have been proposed to support the next generation of scientific advancement. While these facilities have significant scientific, economic, and societal benefits, they also require considerable resources to operate effectively. Amid the ongoing climate crisis, these facilities face the challenge of balancing the need for increased scientific output, size, and/or power with the global need to reduce resource consumption. This challenge presents a unique opportunity to integrate innovative environmental impact reduction techniques into their design. The presented living document offers high-level guidelines to enhance environmental sustainability across the planning, construction, operation, and decommissioning stages of large accelerator facilities. It consolidates various resources and highlights both existing and proposed practices to inspire more sustainable approaches.

Resonant slow extraction is routinely used to provide ion beams to various users. At GSI SIS18, two extraction methods are implemented: quadrupole-driven and Radio Frequency Knock Out (RF-KO) extraction. In either case, delivering a defined beam intensity (spill) without fluctuations or drifts is desired for an efficient beam usage. The Spill Optimization System (SOS) was developed to address this demand and improve the spill quality based on online spill monitoring. Developed using software-defined radio technology, it comprises a feedback controlling the spill rate and an optimization algorithm to improve the spill quality. In the case of RF-KO extraction, it controls the spill by generating tailored excitation signals for the KO exciter. For quadrupole-driven extraction, it produces a control signal for the tune ramp including tune wobbling to improve the spill quality. This contribution gives an overview on the systems and compares different usage scenarios.

The stability of electron beams in storage rings is vital for precise synchrotron radiation experiments. However, external vibrations, such as earthquakes, ocean waves, and human activities, often disrupt beam stability. This study analyzed low-frequency(~0.3Hz) disturbances in the beam orbit systems of the Taiwan Photon Source (TPS) and Taiwan Light Source (TLS). Using Fast Fourier Transform (FFT) and Dynamic Time Warping (DTW), we identified a strong correlation between these disturbances and ocean wave frequencies, with a similarity score of 0.12. Our findings confirm ocean waves as a major disturbance source and emphasize the need for advanced orbit control and vibration compensation to enhance beam stability.

We present recent impedance modeling studies of the kicker systems developed for the Advanced Light Source Upgrade (ALS-U), including ferrite-loaded kickers, stripline-type fast kickers, and septa. The modeling supports the injection/extraction systems to ensure beam stability in the accumulator and storage rings. In addition, it provides guidance for component fabrication and offline testing by incorporating realistic factors such as mechanical tolerances and assembly specifications.

In the slow extraction operation of the J-PARC Main Ring (MR), ensuring the uniformity of the extracted beam's time structure (“spill structure”) is crucial. One primary factor distorting the spill structure is the random fluctuation of the horizontal tune caused by current ripples in the main magnet power supplies. To address this issue, a system called the "tune ripple canceller" has been developed. This system calculates correction values for the horizontal betatron tune based on current ripples and controls the spill structure using fast-responding quadrupole magnets. In 2021, proof-of-principle beam experiments demonstrated its effectiveness in improving the spill structure. Subsequently, as part of the MR's power upgrade plan, the main magnet power supply system was upgraded by 2022. During this upgrade, the current measurement system was reconfigured, and the power spectrum of the current ripples was altered. As a result, it is now urgent to update the hardware and software of the tune ripple canceller system to align with these changes. This paper highlights updates, addresses challenges, and explores strategies to further enhance spill structure control in the MR.

ALBA is a 3rd generation synchrotron light source located in Barcelona, Spain. The circumference is 268.8 meters and electrons are stored at 3 GeV. In the framework of the upgrade towards the 4th generation light source ALBA II, an active 3rd harmonic RF system at 1.5 GHz is foreseen to increase the Touschek lifetime component. The system will be installed and available for operation in the current machine, which will allow to gather experience before the upgrade. Four normal conducting HOM damped harmonic cavities will be placed in the storage ring, each of it including a complete WR650 waveguide system with circulator and load, a 20 kW high power SSPA amplifier and a Low Level RF control system. We are presenting in this contribution the complete design of the active harmonic RF system for ALBA and the expected performance during operation.

The SLS consists of a 100MeV linac, a 2.7GeV booster synchrotron with 9nm horizontal emittance and the storage ring (SR). The old 12-TBA SR with 5nm horizontal emittance operating at 2.4GeV was turned off in 09/2023 after 22 years of successful user operation. In course of the SLS 2.0 upgrade project the 288m circumference SR has been replaced by a 2.7GeV 12-fold 7-bend achromat lattice with a considerably reduced horizontal emittance of 150pm, while keeping the injector complex mostly unchanged. After recommissioning of the injector chain at the end of 2024 SR commissioning starts in January 2025 with some challenges ahead. A reverse bend design has been implemented to achieve the lowest possible emittance with the given small footprint of the SR leading to a very dense magnet arrangement. All bending and combined function magnets which largely determine the novel optics are permanent magnets which will guide the beam through NEG coated vacuum tubes with an aperture of only 18mm. Due to excellent beam diagnostics and optics adjustment capabilities combined with an advanced remote girder alignment system we expect to achieve the performance goals of the storage ring by mid 2025.

In ultra-low-emittance synchrotron light sources, the bunch-lengthening technique is useful to mitigate harmful effects due to the intrabeam scattering. The perfomacne of the bunch lengthening can be degraded by the transient beam loading (TBL) effect induced in the cavities. To mitigate the TBL effect, we proposed a TBL compensation technique using a wide-band longitudinal kicker cavity. In this presentation, we report the result of the experimental demonstration of the TBL compensation performed at the KEK PF 2.5 GeV ring. In this experiment, the fill pattern of the electron bunches were customized to enlarge the phase variation of electron bunches induced by the TBL effect. The fundamental cavities and newly developed digital low-level RF (DLLRF) system were used for the experiment. The DLLRF enables the TBL compensation by an arbitrary feedforward pattern of the cavity voltage modulation that is synchronized with the revolution frequency. Although the bandwidth of the fundamental cavity is limited, the variation of the cavity voltage and bunch phase induced by the TBL effect was reasonably mitigated by applying sinusoidal wave modulation of the cavity voltage.

Fast orbit feedback systems are an important component in fourth-generation synchrotron radiation sources such as PETRA IV at DESY in Hamburg, Germany. These control systems are designed to stabilize the particle orbit, i.e., to correct deviations from the design orbit due to various disturbances. To that end, such a system employs fast orbit corrector magnets, which must be powered at frequencies up to the kilohertz range. This leads to significant eddy current effects that must be predicted via finite element simulations. Therefore, extensive simulation studies have already been conducted. These simulations did not, however, consider the magnetization curve’s nonlinearity since doing so requires prohibitive computational effort when using commercial software. Hence, we have constructed a dedicated method, based on a combination of the harmonic balance finite element method and homogenization schemes, to enable nonlinear simulations. This contribution outlines the general idea and application of our method to the corrector magnets of PETRA IV and presents the most important findings regarding the impact of the nonlinear magnetization curve on the magnet’s performance.

This study presents a multi-module parallel current output system based on the correction magnet power supplies (CMPS) of the TPS storage ring. An N+1 re-dundant control interface card was designed to enable high-current, bipolar modular parallel output. The system integrates external DCCTs and current feed-back signals from the internal module. After PI com-pensation, these feedback signals are compared with the reference current to compute correction values distributed to each CMPS for closed-loop current con-trol. Each CMPS module provides an output of ±48 V/±10 A, and up to eight modules can be connected in parallel for a maximum output of ±80 A. Experimental results demonstrate long-term output current stability within 0.6 mA (or 7.5 ppm), with current noise spectra primarily below 500 µA. The system also supports N+1 redundancy and bipolar current output, offering a stable and flexible solution for magnet power control.

This study investigates the influence of insertion devices (IDs) on the optical properties of the Solaris electron storage ring through a combination of experimental measurements and simulations. The effects of various ID settings were analyzed using tune measurements and the Linear Optics from Closed Orbits (LOCO) method. These results were compared with simulations performed using the Python Accelerator Toolbox (pyAT). Furthermore, a Long Short-Term Memory (LSTM) neural network was developed and tested for forecasting corrector magnet currents associated with the IDs. Diagnostics included monitoring the electron beam in the storage ring and photons delivered to beamlines. Additionally, the performance of both slow and fast orbit correction systems in response to ID-induced perturbations was assessed. This work provides insights into ID impact on beam dynamics and highlights the potential of machine learning for predictive control in accelerator systems.

Recently, two SIRIUS hard X-ray beamlines, EMA and PAINEIRA, were upgraded by replacing their previous insertion devices (IDs) with SIRIUS’s first in-vacuum undulators (IVUs). These new IDs have a period of 18.5 mm and can achieve a peak magnetic field of 1.24 T at a minimum gap of 4.3 mm. This paper reports on the effects of these new light sources on the electron beam, including static and dynamic orbit distortions, impacts on optics, injection efficiency, and changes in the storage ring’s equilibrium parameters.

This work presents the results of single-bunch-instability measurements in the Diamond storage ring. A streak camera was used to measure the bunch lengthening with current, whilst transverse multi-bunch feedback (TMBF) was utilised to quantify the charge-dependent betatron tune shifts and the head-tail instability thresholds. The results show that increasing chromaticity can be used to mitigate head-tail instabilities which can allow to accumulate higher charge in a single bunch. Using TMBF to suppress single-bunch instabilities is discussed.

The Radio-Frequency (RF) system of the CERN Proton Synchrotron Booster (PSB) features Finemet-loaded cavities that cover a wide range of frequencies. This system generates a significant broad-band longitudinal impedance, which must be mitigated to maintain beam stability, particularly at higher beam intensities. To counteract the induced voltage, a direct RF feedback is employed over the entire operational frequency range. It is complemented by a multi-harmonic feedback that applies narrow-band signal processing to reduce the cavity impedance at integer multiples of the revolution frequency. Recent measurements have revealed that these long-delay cavity loops implemented in the Low-Level RF (LLRF) system have a substantial effect on beam dynamics. To validate the impedance model in the closed-loop regime, a detailed model of their behaviour is necessary. This contribution outlines the development process of the numerical model for the PSB cavity feedback loops for particle tracking simulations, which is based on dedicated measurements used to characterise the feedback performance. Comparisons between simulations and measurements are carried-out to assess the validity of the modeling.

The CERN Proton Synchrotron Booster (PSB) delivers a wide variety of high-intensity and high-brightness proton beams to several destinations, including operations at the Large Hadron Collider (LHC) and various fixed-target experiments. Following the Long Shutdown 2 (LS2) upgrades, discrepancies between beam measurements and macro-particle simulations were observed, highlighting the need for a deeper understanding of the longitudinal impedance and related effects in the PSB. To address this, longitudinal single-bunch instability studies have been conducted to evaluate the impedance model through the intensity and energy thresholds across different radio-frequency configurations. This contribution presents experimental results that explore instability mechanisms and the effect of the beam loading compensation feedback system. These results are used to benchmark a new cavity loop simulation, which enables more detailed studies of the accelerator impedance.

Controlled longitudinal emittance blow-up is indispensable for the operation of the Large Hadron Collider (LHC) to counteract single-bunch loss of Landau damping during the acceleration ramp. The blow-up is performed by injecting RF phase noise in a narrow frequency band into the beam phase loop, with bunch-length feedback regulating the noise amplitude. In 2024, the variation of the bunch length due to imperfect regulation caused unacceptable beam-induced heating of certain accelerator components. In this contribution, we present the results of extensive simulation scans that have been used to optimize the feedback parameters. We show how this optimization, along with a reduction of the feedback delay on the controls side, has been implemented in the LHC and significantly improved the bunch length evolution during acceleration. Finally, we discuss the results of a measurement scan performed during an operational period of five weeks to fine-tune the blow-up feedback settings.

The High Luminosity Large Hadron Collider (HL-LHC) project is a major upgrade of the LHC presently operating at CERN, designed to enhance the performance reach in terms of integrated luminosity collected during its operational era by another order of magnitude. It involves the replacement of the entire machine and services over more than 200 meters on each side of the high luminosity experiments of ATLAS and CMS, and other modifications across the entire LHC complex. In this context, the HL-LHC Integration team is responsible for the optimization and validation of the new machine layout to ensure an efficient installation, ease of maintenance, and effective system operation. The paper focuses on the challenges of this integration task, in particular for gathering the information and the models to produce accurate 3D assemblies of the overall project, and identify and manage conflict resolution between different teams. This includes the coordination of several equipment groups and related design offices, adapting to spatial constraints of the existing infrastructure, managing equipment at various stages of their design, and dealing with interfaces between existing and new infrastructure. The team employs a combination of 3D design tools and agile management strategies, such as interactive progress-tracking tools (Kanban Board), scrum, sprints and feedback loops. The integration relies on a complete 3D model from which the new reference Layout drawings and database are derived when design milestones are achieved. Integration releases through robust documentation approval and archiving systems constitute the installation baseline.

KEK Accelerator Test Facility (ATF) conducts beam instrumentation R&D for International Linear Collider (ILC) project. ATF includes 1.3 GeV normal conductivity S-band Linac and Damping Ring (DR). There are 9 S-band pulsed klystrons at Linac, which supply High-Power RF to accelerate electron beam up to 1.3 GeV, 1 CW klystron at DR. The electron beam is generated by a photocathode irradiation by a laser pulse. The laser pulse generation is synchronized with the accelerating fields by the laser system oscillator Piezo feedback. These Linac, DR High-Power RF field and laser pulse arrival time jitter and/or drift define the stability of the electron beam parameters, such as average energy, energy spread (RMS), emittance, bunch charge etc. This study demonstrates KEK ATF Linac and DR High-Power RF field phase and amplitude, as well as the laser system oscillator laser pulse arrival stability measurement results. Also, FPGA board based digital Low-Level RF phase&amplitude feedback system is described in this report.

This work summarizes the most significant diagnostic upgrades that have been implemented, as well as those currently under development, at the Solaris synchrotron facility. These include the installation, startup, and initial testing of a Bunch-by-Bunch Feedback (BBF) system that is currently being implemented at the Solaris synchrotron. Once operational, the BBF system will provide real-time corrections on a per-bunch basis, significantly enhancing beam stability. Efforts are also underway to develop a system for measuring the vertical and horizontal tunes without disturbing the electron beam. Additionally, a beam loss monitoring system is being developed and installed. Complementing these activities, numerous diagnostic scripts have been created, including those that utilize fast acquisition and turn-by-turn data from beam position monitors.

This report discusses various efforts to improve beam stability at the Taiwan Photon Source. The Fast Orbit Feedback (FOFB) system is essential for maintaining beam stability in the light source. Considering the trade-off between FOFB reliability and performance, we optimize the FOFB parameters to achieve better orbit stability in the TPS. Occasional spikes in the Beam Position Monitor (BPM) readings are observed in a few BPM pick-ups and it would degrade the efficiency of the FOFB system. The probability of these spikes occurrence could be related to the different filling patterns and beam currents. A schedule for replacing these BPM buttons will be established. Additionally, the effect of various signal processing schemes on the beam is also examined.

A novel approach combining online unknown input estimation with reconfigurable control has been developed to enhance orbit stability in the Siam Photon Source (SPS) storage ring. These unknown inputs, representing disturbances or uncertainties in the dynamic system, provide valuable insights for achieving robust control. Disturbances such as noise, temperature changes, and modeling uncertainties affecting the control variables can be treated as fault signals, allowing the application of fault estimation and compensation techniques from Fault Diagnosis (FD) and Fault-Tolerant Control (FTC) theories. The initial implementation of this slow orbit feedback (SOFB) system has significantly reduced X-Y orbit fluctuations while maintaining robust control stability against temperature disturbances in the SPS storage ring. This presentation will cover the FD/FTC principles, hardware, software, commissioning results of the current SOFB system, and plans for future developments.

To maintain optimal beam collision conditions and luminosity performance, SuperKEKB requires a fast orbit feedback dedicated to correcting offsets at the interaction point (IP). The 'iBump' feedback system calculates IP beam offset from Beam Position Monitor (BPM) measurements before and after collision and corrects by creating closed orbit bumps in the High Energy Ring (HER). This system has demonstrated robustness at stabilising IP offsets during operation. In this paper, we discuss operational aspects of the system and ongoing challenges, with a focus on the identification of vertical offset as the correction target of the iBump system. Dedicated studies on the current dependence of this feedback target as well as historical data are analysed.

To achieve physics performance at the Future Circular electron-positron Collider (FCC-ee), luminosity and beam lifetime must be maintained at close to design specifications. Alongside global feedbacks, a fast feedback system is proposed to mitigate beam offset errors at the interaction points (IP), caused by magnet vibrations or other time-varying errors. In this paper, the FCC-ee luminosity performance is simulated for beam-beam interactions including beam offsets, providing performance requirements for the fast feedback system.

To damp undesired longitudinal oscillations of bunched beams, the main synchrotron SIS100 of FAIR (Facility for Antiproton and Ion Research) will be equipped with a bunch-by-bunch longitudinal feedback (LFB) system. It will consist of new broadband kicker cavities and a dedicated low-level RF (LLRF) system. The LFB helps to stabilize the beam, to keep longitudinal emittance blow-up low and to minimize beam losses via damping dipole and quadrupole oscillations for up to 10 bunches individually. The topology of the LLRF signal processing is validated in closed loop with beam in the heavy-ion synchrotron SIS18 at GSI for future integration into SIS100. In a recent SIS18 machine development experiment with two bunches at flattop, quadrupole oscillations were excited for one bunch and then damped with a prototype setup of the LFB system using an existing magnetic alloy cavity as dedicated kicker cavity. This paper presents the test setup, the results of this experiment, and the proposed LLRF topology of the closed-loop LFB system. This validates a core part of the final SIS100 system.

In synchrotron light sources, coupled-bunch instabilities driven by resonant wakefields in the vacuum chamber pose significant challenges to beam stability and quality. This study presents the implementation and evaluation of a bunch-by-bunch feedback system at the Pohang Light Source-II (PLS-II). Utilizing state-of-the-art feedback technologies, including Dimtel iGp12 baseband processors and advanced BPM hybrid networks, the system was configured to address both transverse and longitudinal instabilities. Key demonstrations include real-time grow/damp measurements, fast tune tracking, and bunch cleaning to suppress unstable modes effectively. Comparative analysis with the SPring-8 feedback system highlights performance improvements and system tuning strategies tailored to PLS-II’s operational parameters. Results from horizontal and vertical plane modal amplitudes demonstrate robust damping capabilities, maintaining beam stability even at high currents and narrow insertion device gaps. These advancements contribute to enhanced operational efficiency and higher quality photon output at PLS-II.

PAnTHer (Particle Accelerator on THreejs) is a 3D and 2D map for particle accelerators developed using web and touch technologies. The maps are connected to real-time data from accelerator controls, simulators, and an external component database. The map is generated from a lattice file in JSON format and a bundle of JavaScript components for the 3D version, and an SVG bundle for the 2D version. The JSON lattice file can be generated on the fly taking all necessary parameters from a simulator device server and presented instantly to the remote user among with the visualization of some simulated quantities such as position, beta, eta, mu and sigma Available components are: magnets (bending, quadrupoles, sextupoles, correctors, etc.), pumps, valves, PLCs, racks, mirrors, walls etc. Multiple components can be embedded within a single element. The 3D version offers various configurations, ranging from a fast mode, which runs smoothly even on devices with limited computational power, to a standard mode with enhanced graphical details, and a high resolution mode that uses components derived from mechanical department. The latter requires fairly powerful hardware to maintain optimal fluidity.

The FCC-ee, a 90.7 km circumference e+ and e- collider under study at CERN, will require a transverse feedback system capable of handling risetimes as fast as four turns for the lowest order coupled-bunch modes. This can be realized by a distributed system of pick-ups and kickers in more than one location of the ring. The advantages are weighed with respect to the flexibility to respond to different choices of transverse tune working points and the possibility to operate the transverse kickers as an exciter for several measurement applications including as a depolarizer for energy calibration at Z and W energies. Options for the signal processing are outlined together with the overall specifications for the system components. The choice of frequency, a multiple of 40 MHz, is determined by requirements of the baseline 25 ns bunch spacing and the desire for a power efficient kicker system favoring stripline kickers. Performance of different variants of the system are compared in simulation and evaluated for added flexibility and complexity with respect to the placement in the ring.

The KEK e-/e+ LINAC delivers the beams to four storage rings with the top-up injections by switching the beam mode in 50 Hz repetition rate. The beam charge, energy, and number of bunches (one or two) are different for each ring. Therefore, the RF timing and phase are adjusted to each beam mode independently. To stabilize the RF phase drifts caused by the klystron high voltage, the cooling water and accelerating structure temperature, the RF phase feedback was introduced. The correction phase quantity is obtained by feedback calculation using non-injection mode without beam acceleration, and the value is added to set phase value in each mode. As a result, the RF phase in each beam mode has been stabilized.