Synchrotron radiation could contribute to detector background significantly, especially when the electron beam deviates from the design orbit. Without effective control, synchrotron radiation could impede physics data taking or even damage detector components. One of the key contributors to suppress synchrotron radiation in the Electron-Ion Collider IR is to control the electron orbit upstream the detectors. Therefore, it is imperative to define the tolerance of orbit errors in the IR which requires studying the orbital effects on synchrotron radiation. In this report, we will present the studies of orbital effects on synchrotron radiation background in EIC IR, including beam offsets introduced by upstream dipole, correctors, and quadrupole offsets.

We present a Fixed-Field-Alternating (FFA) permanent magnet racetrack electron accelerator with energy range between 10-60 GeV for the future LHeC. Electron beam is brought back to the linac by the single beam line without requiring electric power REDUCING estimated wall power of 100 MW in the present LHeC design to a negligible power for arcs as the permanent magnets are used. The design is based on experience from the very successful commissioning of the Cornell University and Brookhaven National Laboratory Energy Recovery Test Accelerator – ‘CBETA’. The proposal supports sustainability efforts for LHeC by making a 'green' accelerator. It is an energy recovery linac with 99.9% energy efficiency and reduces the power consumption by using small permanent magnets. The FFA non-linear gradient design is a racetrack shape, where, as in the CBETA, the arcs are matched by adiabatic transition to the two (LHeC) or multiple straight sections. Two 10 GeV superconducting linacs are placed on both sides of the Interaction Region (IR) significantly reducing the power of synchrotron radiation loss.

ALBA, the Spanish third generation synchrotron light source, is studying the future construction in the same location of a fourth generation light source called ALBA-II. Since the construction of ALBA in 2008, its critical slab has moved significantly, changing with it the accelerator elements positions. In this study, the effects on closed orbit and beam optics errors are simulated from data of the survey campaigns on the ALBA storage ring and compared to measurements in terms of orbit, linear optics, and orbit correctors budget. The results of this study on ALBA are used to infer the effect of the slab movement on the future machine through simulations, predicting yearly and seasonal changes. Plausible correction methods are discussed.

The peak-detected Schottky system is a powerful diagnostic tool for observing the longitudinal beam parameters. According to the theoretical model, the peak value of the signal from a wide-band pick-up contains information on particle distribution as a function of the synchrotron frequency. Due to intrinsic assumptions needed for modelling the acquisition set-up and uncertainties in beam parameters, a one-to-one comparison of predictions and measurements remains a challenge. We obtained, for the first time, the peak-detected Schottky spectra in macro-particle simulations for a simplified experimental set-up. Following refinement of the theoretical model, a direct comparison was performed under controlled conditions. Agreement with the numerical results was improved by introducing an additional form factor describing the probability of a particle being present in the observation window. Modifications due to collective effects are briefly discussed as well.

Recent studies have investigated a longitudinal instability that may develop in electron storage rings featuring higher-harmonic cavities. The instability, also referred to as periodic transient beam loading (PTBL), manifests as a slow oscillation of bunch longitudinal profiles following a coupled-bunch mode 1 pattern. In this contribution, we applied a well-established theory of longitudinal mode-coupling to assess the thresholds for this instability. Results obtained through this semi-analytical approach, considering different storage ring and harmonic cavity parameters, were validated using macroparticle tracking and compared against other methods proposed in previous investigations.

Almost all linac-based free-electron laser (FEL) facilities have employed a symmetric three- or four-dipole chicane to compress the electron beam in order to achieve a kA-level bunch current. The achromatic C-type chicane has been widely used in present linac-FEL facilities. Coherent synchrotron radiation (CSR) induced microbunching instability (MBI) can be an issue in the chicane design. Recently a novel design of non-symmetric four-dipole chicane has been proposed to effectively mitigate the CSR-induced emittance growth. In this work we derive an analytical formula of the CSR-induced microbunching gain in a generic four-dipole chicane based on the iterative approach. The formulas have been benchmarked against semi-analytical Vlasov calculation, applied for a quick estimate of CSR-induced MBI for a generic four-dipole achromatic chicane beamline, and can be used to verify the effectiveness of suppressing MBI in a non-symmetric S-type four-dipole bunch compressor chicane.

SOLEIL II is an upgrade project of the existing Synchrotron SOLEIL facility. It aims to reach fourth-generation light source parameters. This includes reductions of the transverse beam emittance, vacuum chamber dimensions and momentum compaction factor. A new impedance model of the SOLEIL II storage ring was developed. This paper demonstrates the evaluation of transverse single- and coupled-bunch instabilities with an up-to-date impedance model. Storage ring operation with a harmonic cavity is an essential component of the project. A harmonic cavity provides bunch lengthening and perturbs synchrotron motion. Its effects on transverse instabilities in SOLEIL II are reported in this contribution.

We develop an alternative theory of coherent synchrotron radiation (CSR) wakefield using the transverse field solution of Maxwell equations in angular domain. This approach allows us to retain only the radiative interaction between particles and cure the frequently encountered divergence in retarded potentials. We analyze the classical radiation reaction force and mass renormalization induced by the CSR self-field. Futhermore, we illustrate our theory by explicitly calculating the steady-state CSR wakefield of a wiggler.

Near-adiabatic capture into an RF bucket with rising voltage has been used since 1946 or earlier. But until the present work, there is no analytic and deterministic description of the process capable of predicting the final phase space distribution (for arbitrary voltage ramps). Recently, we have developed formulae for trajectories that cross the instantaneous separatrix, and the corresponding change of Hamiltonian. Previous attempts at this calculation were unsatisfactory: either plagued by singularities, or limited to probabilistic results for linear variation of the confining potential. Previously*, we presented formulae for the changes in Hamiltonian (due to modulation and bunching) before and after separatrix crossing; and those contributions to emittance growth are equally or more important. Together, the three results provide a complete, analytic description of near-adiabatic capture into an RF bucket.

In the latest years Machine Learning (ML) has seen an unprecedented diffusion in the most different fields in simulations and real life as well. Probably two of the first and most used ML applications in accelerators are the optimization of the final performance of the machines, and the so called virtual diagnostics. In the latest years ML was successfully applied to improve the machine safety performing fault detection or to prevent interlocks. In this work we explored the possibility to use a ML approach to efficiently steer the beam in case the lattice contains high order magnets (sextupolar order and higher). We applied this scheme to SLS 2.0, the synchrotron upgrading at the Paul Scherrer Institut.

The Korea fourth-generation storage ring (Korea-4GSR) project was launched in 2021 to generate high-brightness photon beams as a diffraction-limited light source. The 200 MeV beam is injected into the booster synchrotron. The beam parameters and transmission efficiency fluctuate with initial beam conditions such as beam Twiss parameters and centroid offsets during the injection and energy ramping process. Therefore, the study on the initial conditions of the incident beam to the booster synchrotron needs to be carried out to gain high beam quality and efficiency. This paper presents the energy ramping results of the beams injected into the booster synchrotron with various initial beam conditions.

In this paper, we delve into the application and comparative analysis of the Accelerator Physics Emulation System Cavity-Beam Interaction (APES_CBI) module within the BEPC-II (Beijing Electron-Positron Collider) experiments. We developed the APES_CBI module as an advanced time-domain solver, specifically designed to analyze RLC circuits driven by beam and generator currents and to simulate the dynamic responses and synchrotron oscillations of charged particles within the cavity. We begin by discussing our method for solving RLC parallel circuits, followed by an explanation of the logical architecture of our program. In the second part, we detailed our simulation results, starting with the BEPC-II electron ring. By comparing these results with experimental data, we validate the reliability of our simulations, showcasing our module's ability. Additionally, we extend our simulations to the CEPC Higgs mode on-axis injection conditions and studied the transient phase response to the sudden change of beam pattern.

CERN Proton Synchrotron (PS) is featured with 100 C-shaped combined-function Main Units (MUs) magnets with a complicated pole shape. The operation and the modelling of the PS-MUs has been historically carried out with empirical beam-based studies. However, it would be interesting to understand whether, starting from a proper magnetic model and using the predicted harmonics as input to optics simulations, it is possible to accurately predict the beam dynamics behavior in the PS, and assess the model accuracy with respect to beam-based measurements. To evaluate the magnetic model quality and its predictions, bare-machine configurations at different energies were prepared, where only the Main Coil is powered and the additional circuits are off. In this paper, a comparison of tunes and chromaticity measurements with the predicted optics is reported, showing the saturation of the quadrupolar and sextupolar components at high energy, which affect these quantities.

In 2023, an RF technique known as empty-bucket channelling was implemented operationally at the CERN Super Proton Synchrotron (SPS) to improve the quality of the spill provided to the North Area experiments. Empty-bucket channelling suppresses particle-flux variations during resonant slow extraction by accelerating particles between empty RF buckets and rapidly displacing particles into the tune resonance via chromatic coupling. The flux variations are often caused by the power converter ripple present in the synchrotron’s magnets, which modulates the beam dynamics during the extraction process. In a chromatic extraction, the quadrupole ripple is the main contribution to the modulation as it directly perturbs the transverse tune. When empty-bucket channelling is applied, however, dipole ripple additionally modulates the size of the empty RF bucket. In this contribution, the phenomenon is explored and the consequences for empty bucket channelling in the SPS are outlined.

The 3.0 GeV ALBA Synchrotron Light Source, in operation with users since 2012, is looking forward an upgrade aimed at enhancing the brightness and coherence fraction of the delivered X-ray beam. The Storage Ring (SR) will be completely renewed but we plan on keeping the same orbit length and the position of the ID source points. The energy of the electrons will be preserved and the same injector will be used. Major part of the Insertion Devices and Front Ends will be kept; new ones will feed additional long Beamlines (230m-275m), included on the project. The “dark period” is foreseen for 2030-2031. This paper presents the strategic plans being developed to test and assemble the new SR components, the dismantling of the present SR and the seamless installation of the upgraded SR. Emphasizing a cost-effective and time-efficient approach, we have started the planning by focusing on optimizing spaces and equipment movements necessary for the upgrade process.

Conceptual design work is under way for a fourth generation light source in Australia.This new light source is being designed as a completely new facility, intended to come into operation around 2037 as the current Third generation Australian Synchrotron reaches its end of life. Previous design work was done to consider a 600 m ring, but on review the decision was made to reduce the circumference to 450 m. This paper will outline the main design considerations, initial lattice design and technology choices currently under consideration.

A new project is underway to develop the successor to the current Australian Synchrotron. The new storage ring is proposed to be 455 m in circumference operating at 3 GeV. A preliminary 7BA lattice has been designed which utilizes the higher-order achromat (HOA) scheme to suppress strong sextupole driving terms. The lattice has 24 sectors and a natural horizontal emittance of 50 pm-rad. This is achieved using a combination of strong combined function magnets and reverse bending magnets in the unit cell, as well as careful tuning of the bending angles to preserve positive momentum compaction factor. The dynamic aperture, momentum aperture and Touschek lifetime have been optimized by tuning the linear optics and sextupole strengths with a multi-objective genetic algorithm.

Bunches excited by a transverse kick out of the closed orbit develop betatron oscillations, whose dynamics is affected by the chromaticity used in the accelerator or storage ring. Specifically, decoherence and recoherence effects caused by chromaticity can be modified by introducing Landau damping in the synchrotron phase space, when using a harmonic cavity to stretch the bunch length in order to improve the beam stability. Chromaticity will convert any oscillation in the longitudinal phase space into a frequency modulation of the betatron tune, changing the pattern of the echos of the kick in the beam offset. Focusing on the SLS 2.0 storage ring, we present a study about the damping of single bunch transverse oscillations with non zero chromaticity, including the harmonic cavity and the broadband impedance. These damping times are used to predict the threshold of the transverse coupled bunch instability in SLS 2.0.

Previous TDR (Technical Design Report) studies for the SOLEIL upgrade project (SOLEIL II) have converged towards a lattice alternating 7BA and 4BA HOA (High Order Achromat) type cells providing an ultra low natural horizontal emittance value in the 85 pm·rad range at an energy of 2.75 GeV. The new TDR lattice is an evolution that keep the insertion devices photon source points at their present location, allows a better relative magnet positioning and more space for accommodating photon absorbers, BPMs (Beam Position Monitor) and other mandatory diagnostics. This last evolution includes a better modeling of all the bend magnets based on their realistic field profiles and the accommodation of height super-bends for beam-lines as well as for beam size diagnostics. In addition an exhaustive investigation of the systematic and especially the cross-talk multipoles as well as the phase 1 portfolio of insertion devices impacts has been carried out. This paper reports the linear and the non-linear beam dynamic optimizations as well as future directions for performance improvement.

The synchrotron SOLEIL is the French third-generation 2.75 GeV synchrotron light source, a research laboratory at the forefront of experimental techniques for the analysis of matter down to the atomic level, and a service platform open to all scientific and industrial communities. We present the performance of the accelerators, which deliver extremely stable photon beams to 29 beamlines. We report on last year's overall performance figures and the operation of the brand-new cooling station. As the optimization of the energy and carbon footprint becomes more and more prevalent in France and Europe, actions for a more sustainable operation are given. Several incidents are also presented, together with the lessons learned to avoid recurrence. Major research and development activities related to component obsolescence and the SOLEIL II project will also be presented.

Scraping the beam in an electron storage ring while counting photons of synchrotron radiation is a well-known technique to produce a beam of a single or a few electrons which enables new experimental opportunities compared to standard accelerator physics. Synchrotron radiation is usually described as an electromagnetic wave in the frame of classical electrodynamics. The emission of photons by a single electron, on the other hand, reveals the quantum nature of synchrotron light. The statistical properties of photons contain additional information, which can be used for beam diagnostics purposes. The paper describes the experimental setup and first single-electron measurements at the 1.5-GeV synchrotron radiation source DELTA at TU Dortmund University.

To reduce the electric power consumption and advance the magnetic stability, a prototype of BTS dipole magnet in TPS transfer line between booster and storage ring came into sight. An 1 m long, high current dipole will be replaced by a permanent magnet with Sm2Co17. The new permanent dipole magnet will decrease total volume compared with original electric one, and the homogeneity of integral field is promoted as well. With simulation, the assembly deviation was also discussed. This article presents the magnet circuit design status of prototype to upgrade the transport line in TPS.

Fourth-generation synchrotron radiation sources, which are currently being planned in several accelerator laboratories, require fast orbit feedback systems to correct distortions in the particle orbit in order to meet stringent stability requirements. Such feedback systems feature corrector magnets powered at frequencies up to the kilohertz range, giving rise to strong eddy currents. To understand the eddy current effects and the characteristics of these fast corrector magnets, elaborate finite element simulations must be conducted. This paper gives an overview of the most important findings of our simulation studies for the fast corrector magnets of the future synchrotron radiation source PETRA IV at DESY, Hamburg, Germany. Using a homogenization technique for the laminated yokes, we simulate the magnets over a wide frequency range.

Conceptual studies for a muon collider identify fast-ramping magnets as a major design challenge. Rise rates of more than 1 T/ms are attainable with normal-conducting magnets, incorporating iron yokes to make sure that stored magnetic energies and inductances stay below reasonable thresholds. Moreover, for energy efficiency, the magnets need to exchange energy with capacitors, such that the electric grid only needs to compensate for the losses. The design of such magnet systems is based on two- and three-dimensional finite element models of the magnets coupled to circuit models of the power-electronics equipment. The occurring phenomena necessitate nonlinear and transient simulation schemes. This contribution presents the analysis of a two-dimensional, nonlinear and time transient analysis of a bending magnet, energized by a symmetrical current pulse of a few ms.The magnet yoke is represented by a homogenized material refraining from the spatial discretization of the individual laminates, but nevertheless representing the true eddy-current and hysteresis losses.

Research on a novel permanent quadrpole magnet (PQM) design is introduced in this paper. It can make the quadrupole magnetic field gradient continuously adjustable by modulating several permanent magnet blocks. Four poles of the magnet inform an integral whole to ensure good structural symmetry, which is essential to obtain high-quality quadrupole magnetic field permanent quadrupole magnet. Series of simula-tion calculations have been done to study the effects of four distinct types of pole position coordinate errors on the central magnetic field. By juxtaposing these results with those derived from optimal design scenario of PQM, the study underscores the critical role that pole symmetry plays in this context. Two integrated design methodologies were proposed, with one of the designs undergoing processing and coordinate detection. The results indicate that this design, is capable of meeting the specified requirements. This design effectively ad-dresses the issue of asymmetrical pole installation, thereby ensuring to a certain extent that well-machined pole can generate a high-quality magnetic field.

Modification of an arc-cell vacuum system (length 14 m) for the cell SR18 in the TPS storage ring is described, which includes (a) replacement of a new bending chamber (B1) with an increased vertical aperture from 9 to 18 mm to prevent the B1 chamber from being exposed to synchronous radiation from the upstream elliptically polarized undulator (EPU), and (b) incensement of three pairs of flanges to separate the old arc-cell vacuum system into four subsystems (S3, B1, S4, B2). In this paper, we will report the manufacturing processes, measurement data and vacuum tests of these vacuum chambers.

The European LEAPS-INNOV project has launched a Research and Development program dedicated to the design of a new generation of germanium detectors for X-ray spectroscopy applications. The present article shows the results of the thermomechanical simulations of this design, based on finite element analysis (FEA) studies, under vacuum and cryogenic conditions. The first results of these simulations were published at IPAC'23*. In this new work, the final results are presented, which includes the thermal optimization of the detector with respect to the previous study, as well as new numerical simulations to investigate the effects of vibration transmission from the cryocooler to the head detector.

Within the field of Particle Accelerators engineering, the design of cooling channels for its components has heavily relied on experimental correlations to compute convective heat transfer coefficients. These coefficients are believed to have a conservative factor which end up in oversized designs. The following study assesses this conservative factor for fully developed flows, in the laminar, turbulent and transition regimes. It will also focus on different geometries to do so. With this objective in mind, simulation models have been developed and correlated with experiments carried out at ALBA synchrotron. In the course of this research, various turbulence models and meshes have been examined for the development of the simulations. Heat transfer coefficients were derived from the Computational Fluid Dynamics (CFD) simulations and juxtaposed with empirical correlations. The specific geometries under investigation encompass a circular channel with a 10mm inner diameter, a rectangular section channel, and a pinhole geometry, the latter being frequently employed in accelerator technology.

MedAustron is a synchrotron-based cancer therapy center located in Lower Austria. Patients are treated with proton and carbon ion beams in an energy range of 62-252 MeV/u and of 120-400 MeV/u respectively. The facility features three clinical irradiation rooms, among which horizontal and vertical beam lines as well as a proton gantry are available for treatment. A fourth irradiation room (IR1) is dedicated to non-clinical research activities among which helium ion beams are currently under commissioning. Helium ions are also promising future candidates for clinical treatment due their favorable physical and biological properties. At MedAustron the beam commissioning up to IR1 is near completion. A large energy range (i.e. 39-402 MeV/u) has been commissioned with the support of Monte Carlo simulations performed by the future users. The beam properties in terms of spot size and beam roundness obtained at the isocenter fulfill the user requirements. In this work we present the helium commissioning status with the main focus on the recent results obtained from the commissioning of the synchrotron and transfer line up to the isocenter in IR1.

Compact synchrotrons, such as those proposed for cancer therapy, use short and highly bent dipoles. Large curvature drives non-linear effects in both body and fringe fields, which may be critical to control to obtain the desired dynamic aperture. Similarly to current practice, for straight magnet, our long-term goal is to aim at finding a parametrization of the field map that requires few terms to capture the relevant long term dynamical effects. This parametrization will then be used to optimize the performance of the synchrotron by long-term tracking simulations and, at the same time, drive the development of the magnet design by providing measurable quantities that can be computed from field maps. This paper presents the first steps towards the goal of representing the field with a few key parameters.

MedAustron is an ion therapy facility located in Wiener Neustadt, Austria, which uses third order resonant slow extraction to deliver protons and carbon ions for clinical irradiation. The foreseen upgrade of the new low level RF (LLRF) system facilitates advanced longitudinal beam manipulation schemes involving multiple RF harmonics, which will be exploited to improve the slow extraction process and the consequent spill characteristics. To support these studies and provide a new diagnostic tool longitudinal tomography is being implemented. This proceeding presents the employed measurement set-ups and compares the first obtained tomographic reconstructions with BLonD simulations.

Reinforcement Learning (RL) has demonstrated its effectiveness in solving control problems in particle accelerators. A challenging application is the control of the microbunching instability (MBI) in synchrotron light sources. Here the interaction of an electron bunch with its emitted coherent synchrotron radiation leads to complex non-linear dynamics and pronounced fluctuations. Addressing the control of intricate dynamics necessitates meeting stringent microsecond-level real-time constraints. To achieve this, RL algorithms must be deployed on a high-performance electronics platform. The KINGFISHER system, utilizing the AMD-Xilinx Versal family of heterogeneous computing devices, has been specifically designed at KIT to tackle these demanding conditions. The system implements an experience accumulator architecture to perform online learning purely through interaction with the accelerator while still satisfying strong real-time constraints. The preliminary results of this innovative control paradigm at the Karlsruhe Research Accelerator (KARA) will be presented. Notably, this represents the first experimental attempt to control the MBI with RL using online training only.

We present the results of the first experiments on 6-dimensional phase-space tracking of a single electron in a storage ring, using a linear multi-anode photomultiplier tube for simultaneously measuring transverse coordinates and arrival times of synchrotron-radiation pulses. This technology makes it possible to fully reconstruct turn-by-turn positions and momentums in all three planes for a single particle. Complete experimental particle tracking enables the first direct measurements of dynamical properties, including invariants, amplitude and energy dependence of tunes with exceptional precision, and chaotic behavior.

New technical approaches are under investigation to further push the intensity frontier of the next generation heavy ion synchrotrons. Residual gas dynamics and corresponding charge exchange processes are key issues which need to be overcome by means of advanced UHV system technologies, but also by a focused design of the synchrotron as a whole. Cryogenics and superconductivity enable high field operation but in synergy also enable technologies for stabilizing the dynamic vacuum. Beam loss usually implicated as driver for activation and damages is as well an important initiator for residual gas pressure dynamics. Advanced superconducting cables promise lower energy consumption, fast ramping and higher average beam intensities. The cryo-pumping properties of specially developed cryogenic inserts, can also be used to upgrade existing synchrotrons and enable operation with lower charge states and higher intensities. The advancement of laser technologies may be applied as new devices in heavy ion synchrotrons for advanced manipulations, e.g. non-liouville injection or laser cooling. With FAIR, GSI has expanded its competence for the design of novel high intensity heavy ion synchrotrons.

Synchrotron radiation (SR) is a phenomena found in most accelerator facilities. Whilst many look to reduce the amount of SR produced to minimize beam losses, its existence allows for several types of novel non-invasive beam instrumentation. The aim of this study is to use SR in the development of a non-invasive, high resolution, longitudinal bunch length monitor. The monitor will be capable of sub 100 fs bunch measurements, which are becoming more common in novel acceleration and free electron laser facilities. This contribution details the simulation work carried out in Synchrotron Radiation Workshop (SRW), which allows for complex studies into the production and features of coherent synchrotron radiation (CSR). The design of the monitor has also been discussed, alongside simulations of the planned optical setup performed in Zemax OpticStudio (ZOS).

Observation of Schottky signals provides information on important beam and machine parameters, such as transverse emittance, betatron tune, and first-order chromaticity. However, the so-far developed theory of Schottky spectra does not include the impact of the higher-order chromaticity, known to be non-negligible in the case of the Large Hadron Collider (LHC). In this contribution, we expand the theory of Schottky spectra to also take into account second-order chromaticity. Analytical results are compared with macro-particle simulations and the errors resulting from neglecting second-order chromaticity are assessed for the case of the LHC.

Schottky monitors are valuable non-invasive tools used for beam diagnostics, providing insights into crucial bunch characteristics such as tune, chromaticity, bunch profile, or synchrotron frequency distribution. This study investigates Schottky spectra at the Large Hadron Collider (LHC) through a combination of simulations and measurements. Experimental data from lead ion bunches are compared with simulated spectra derived from time-domain, macro-particle simulations. In particular, amplitude detuning due to the octupole magnets, known to influence the Schottky spectra, is incorporated into the simulations. These simulations are performed for various octupoles currents with the goal of better understanding the interplay between octupoles and the Schottky spectrum. Finally, measured spectra are compared to simulations performed using the best available knowledge of the parameters impacting the spectra.

The Karlsruhe research accelerator KARA offers a setup to measure the beam energy with resonant spin depolarization. The depolarization is excited by the stripline kickers of the bunch-by-bunch feedback system and the resonant frequency is measured via change in Touschek lifetime. Energy measurements with resonant spin depolarization are implemented as a standard routine in the control system and are used regularly to measure both the beam energy and the momentum compaction factor for different energies and optics regimes. Long-time experience with the setup, short polarization time, and variation options of beam energy in combination with much available beam time qualify KARA as a test facility for systematic studies. Such studies are of particular interest for future colliders designed for precision studies like FCC-ee, as resonant spin depolarization is known for its high accuracy. This contribution presents the resonant spin depolarization setup at KARA and selected results of recent measurement campaigns.

At the Karlsruhe Research Accelerator (KARA) facility, an electron beam is generated by a thermionic electron gun, pre-accelerated to 53 MeV by a microtron and then ramped up to 500 MeV in a booster synchrotron before being injected into the storage ring, where a final electron energy of 2.5 GeV is reached. Compared to a 2D camera, when using 1D photodetectors either directly at the synchrotron light port or after a fiber optics segment, the optic design goal is to maximize the optical intensity at the photo detector, rather than to keep spacial coherence. In this field of non-imaging optics the emitter, optical setup and sink can be modeled in the optical phase space, with the etendue being the conserved quantity and position and angle the independent variables. In this contribution we describe the synchrotron radiation emitted at a dipole in the KARA booster synchrotron and the imaging setup into an optical multimode fiber with this formalism and compare the results with measurements at the synchrotron light port of the booster synchrotron.

In the upcoming compact STorage ring for Accelerator Research and Technology (cSTART), LPA-like electron bunches are only stored for about 100 ms, in which the equilibrium emittance will not be reached. Therefore, to measure parameters such as bunch profiles, arrival times and bunch current losses, bunch-resolved diagnostics are needed. The booster synchrotron of the KARA accelerator accepts pre-accelerated bunches from a racetrack microtron and accelerates them further over a 500 ms long energy ramp. As the KARA booster synchrotron has a similar circumference and injection energy as the cSTART storage ring, new bunch-by-bunch diagnostics developed there can be transferred to the cSTART project with minimal effort. Currently the diagnostic system of the booster is not designed for bunch-by-bunch diagnostics, thus after using the booster as a testbed for cSTART, such a system could be used permanently. At the booster synchrotron we use the picosecond sampling system KAPTURE-II to read-out a button beam position monitor and an avalanche photo diode at the synchrotron light port and compare the results with a commercial bunch-by-bunch system.

Single-bunch instability is studied at the Taiwan Photon Source both with and without bunch-by-bunch feedback (BBF). The instability thresholds are investigated at various chromaticities by increasing the bunch current until the instability occurs. BBF and chromaticity can increase the maximum stored bunch current and allow the tune to cross the unstable region. As the bunch current increase, the tune around the betatron frequency decreases and the tune around the synchrotron sideband increases. High radiation doses are detected by beam loss monitors when the bunch current exceeds 2 mA, near the unstable region, originating from synchrotron light scattered by the photon absorber. As the single bunch becomes unstable, electron beam loss occurs after the first band magnet of the straight section with the smallest vertical aperture.

The FCC-ee is a proposed high-luminosity circular electron-positron collider which will have beam energies spanning from 45.6 to 182.5 GeV, and will radiate up to 50 MW of synchrotron radiation power per beam. The lattice design upstream of the interaction point is based on weak dipoles and long straight sections combined with a 30 mrad crossing angle. The optics design provides a flat beam at the IP while integrating an anti-solenoid and detector solenoid. This paper summarizes the design principle and performance of the FCC-ee synchrotron radiation collimation scheme and provides insights into the synchrotron radiation simulations within the interaction region, conducted with BDSIM using the GEANT4 toolkit. Special attention is turned to the complexity of the transverse beam tails, including their width and particle density, representing valuable perspectives for the design of an effective synchrotron radiation collimation system.

The Future Circular Collider (FCC-ee) is designed to explore the Z and W± bosons, along with the Higgs boson and top quark, achieving exceptionally high luminosity. In order to minimize the energy lost per turn due to Synchrotron Radiation (SR) we explore the use of Nested Magnets (NMs) into the arcs cell. For this, it is necessary to explore the possible combinations of the different magnet types in the cell, namely: dipoles, quadrupoles and sextupoles. Specifications in terms of strength and alignment tolerances are reviewed in this paper.

A significant project such as the FCC-ee (with 91.17 km circumference) entails numerous challenges to ensure the stability and performance of the machine. In the pursuit of contributing to the improvement of energy consumption during its operation, the exploration of Nested Magnets (NMs) as a means to reduce synchrotron radiation has been undertaken. This paper presents first studies on the Dynamic Aperture (DA) and the Momentum Acceptance (MA) of this novel design to guide the next developments.

The sixth International School on Beam dynamics and Accelerator technology (ISBA23) was held for 10 days from August 3rd to 12th, 2023 at Pohang in Korea. ISBA23 was jointly hosted by Korea Atomic Energy Reꠓsearch Institute (KAERI) and Korea Accelerator and Plasma Research Association (KAPRA). After screening 83 registrant’s resumes and letters of recommendation, 70 students from Korea, Japan, China, Taiwan, India, and Thailand were finally admitted to the school. For 10 days, 20 professional scientists from Korea, Japan, China, Taiwan, Thailand, Germany, and the USA gave 30 valuable lectures and 14 hands-on training sessions with ASTRA and ELEGANT accelerator codes. Thanks to the generous financial support from 14 sponsors, the school was successfully completed. This is the first time that ISBA has been held outside of Japan, and it is a big step toward becoming a truly international accelerator school. We report on ISBA23, which is the biggest international accelerator school in Asia.

High currents of bunched electron and positron beams plan to be used in the proposed FCC-ee collider to achieve a high luminosity. Naturally, the impedance of the interaction region of the FCC must be as small as possible. Previously, a very smooth beam pipe in the interaction region was designed, and now we add necessary elements important for the beam operation, reduced backgrounds, and assembly. Among these elements are BPMs, expansion bellows, extension of the common beam pipe, and an elliptical synchrotron radiation mask. These new elements will be analyzed to see if they increase the impedance and, then, followed by discussions how to mitigate any issue.

Synchrotron light sources often use higher-harmonic rf cavities for bunch lengthening to enhance Touschek lifetime. By adjusting the harmonic voltage, a flat-potential condition for the longitudinal voltage can be achieved, typically improving Touschek lifetime by 4 to 5 times. It is known that exceeding the flat-potential voltage results in double-peaked bunch profiles, referred to as overstretched conditions. Simulations suggest overstretched profiles can surpass flat-potential improvements on lifetime. In this paper we report on experimental results from the MAX IV 1.5 GeV storage ring, demonstrating a longer beam lifetime with a stable beam in overstretched conditions compared to the flat-potential case. Additionally, a remarkable agreement between measured bunch profiles using a streak camera and predictions from a semi-analytical equilibrium solver was obtained for all tested harmonic voltages.

In preparation for PIP2, there has been interest in running the Fermilab Booster at a higher current more indicative of the PIP2 era operation. In July 2023 an experiment was performed to study collective instabilities over the transition crossing at the Fermilab Booster. Over the transition crossing, the synchrotron tune becomes small and synchro-betatron instabilities become possible. During the experiment, an intensity threshold was observed, above which a dipole instability with losses concentrated in the tail of the bunch. These losses are consistent with the Convective Instability.

Coherent synchrotron radiation (CSR) is one critical beam collective effect in high-energy accelerators, which impedes the generation of high-brightness beams. The Argonne Wakefield Accelerator (AWA) facility is unique in the experimental investigation of CSR effects in complex beams, offering a large parameter space for the bunch charge and size, various bunch profiles (round and flat beams), and the capability of generating shaped bunches through both laser shaping and the emittance exchange approach. This presentation will outline planned experiments at AWA and their designs, including a CSR shielding study using a dipole chamber with a variable gap size, and the effect of CSR on the beam phase space in a laser-shaped short electron bunch. This work is part of a comprehensive study involving self-consistent CSR code development and experimental investigation. The experimental component aims to provide benchmarking with the advanced codes under development, explore the boundaries of 1/2/3D CSR effects on beam dynamics, evaluate CSR effects in complex beams, and eventually propose CSR mitigation strategies.

A digital direct RF feedback (DDRF) has been implemented in the DLLRF of the ALBA synchrotron light source in order to mitigate the beam loading effects of the beam. Specifically, with the DDRF implemented in the main cavities, the tune shift due to beam loading can be minimized and therefore the DC-Robinson instability can be mitigated. It can also be used to minimize voltage drops in case of transients after a cavity loss during the operation. Also, for the next generation machine ALBA-II and applied to the active 3rd harmonic system, it can be used to fight against AC-Robinson instability induced by the harmonic cavities, increasing the damping rate of the fundamental CBI mode, and reducing the transient beam loading effects. In this contribution we present measurements with beam of the DDRF applied to ALBA main cavities, demonstrating a reduction of a factor two in the effective impedance of the cavity as seen by the beam.

A new Rapid Cycling Synchrotron (RCS) [1] is designed to accelerate the electron bunches from 400 MeV up to 18 GeV for the Electron Ion Collider (EIC) [2] being built at Brookhaven National Laboratory (BNL). One of the two Relativistic Heavy Ion Collider (RHIC) rings will serve as the Hadron Storage Ring (HSR) of the EIC. Beam physics simulations for the RCS demonstrate that the electron beam is sensitive to the outside magnetic field in the tunnel. Significant magnetic fields are expected due to the HSR and the Electron Storage Ring (ESR) being at full energy during the RCS operation. The earth magnetic field at the location of the RCS center was measured throughout the circumference of 3870 m tunnel without RHIC operation. In addition, the fringe magnetic field from RHIC magnets at several locations during RHIC operation was measured and compared with simulation at different ramping currents. A robotic technology is being developed to automatically measure the stray magnetic field at any location during the RHIC (or future EIC) operation.

The National Synchrotron Radiation Research Center (NSRRC) has conducted a study on the magnetic circuit design of a high-temperature superconducting undulator (HTSU). This study explores the potential use of second-generation high-temperature superconducting (2G-HTS) materials in undulator magnet, which offer advantages such as higher current density and operating temperature. To evaluate the feasibility of HTSU design, a preliminary magnetic circuit analysis has been conducted. The simulation of the HTSU involved the use of several commercial 2G-HTS tapes with different widths. Insulating and non-insulating HTS tapes were compared to evaluate their effects on current density and magnetic field. Additionally, the maximum field strength on the surface of the tape was determined to establish the optimal operating temperature and current density for the HTSU. These simulation results provide valuable insights for optimizing the design and performance of the HTSU, ultimately contributing to advancements in particle accelerator technologies.

Reduction of dynamic aperture encountered in 4th generation light sources presents a challenge for injection efficiency and commissioning. It’s possible that only after BBA and optics corrections are applied, will the dynamic aperture be sufficient for reasonable injection efficiency. Furthermore, it’s only after a circulating beam is established that BBA, BPM calibration, and other optics corrections can be applied. Limited dynamic aperture not only makes standard top-up operation more challenging; during commissioning this challenge is even greater. To address this problem, we have developed a lattice design that allows for both low emittance optics (for standard user beam operation) and what we have called “commissioning optics” which is a set of lattice parameters that allows for larger dynamic aperture and Touschek Lifetime at the (temporary) cost of larger horizontal emittance.

An upgrade to the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (JLAB) is anticipated to provide an electron beam of over 20 GeV using the existing superconducting-RF linear accelerator and new fixed-field alternating (FFA) gradient recirculation arcs made up of Halbach-style permanent magnets. In the current design, the FFA arcs will carry six beams with energies of approximately 11, 13, 16, 18, 20, and 22 GeV which will require horizontal splitter lines to match the beam from the preceding linac. In this paper, we describe two alternative splitter beamline designs that are tuned to match the beam's Twiss parameters, R56, time-of-flight, bend-plane offset, and dispersion into the FFA cells.

The demands of a higher brightness photon beam push the electron beam emittance of storage rings towards a diffraction-limited level. The concept of multi-bend achromat (MBA) structure and its variations, containing multiple dipoles in a cell, has been widely employed in the fourth-generation storage ring light sources. Recently, a novel concept of lattice structure, called complex bend lattice, extends the option for low emittance ring lattice design. This paper presents the developed low-emittance complex bend lattices. The benefits of using complex bends include low natural emittance, long straights for IDs, more free space for accelerator equipment, and reduced power consumption for magnets.

The SLRI Beam Test Facility (SLRI-BTF) is able to produce electron test beam with maximum energy of 1.2 GeV and various intensities from a few to millions of electrons per repetition. The main components of the SLRI-BTF are the Siam Photon Source (SPS) injector consisting of a 40-MeV linear accelerator, a low-energy transport beamline, a synchrotron booster increasing electron energy to 1.2 GeV, and a high-energy transport beamline. As the SLRI-BTF has successfully utilized the electron test beam to characterize pixel sensors for high-energy particle detectors and to perform high-energy electron irradiation, the test beam with lower energy ranges has also been requested by users. In this work, the test beam with lower energy can be obtained by changing the acceleration pattern of the SPS booster and adjusting high-energy transport beamline to match the extracted beam energy. Production of test beam with lower energy can be confirmed by test beam measurement at the SLRI-BTF experimental station.

MedAustron is a state-of-the-art synchrotron-based accelerator complex that provides irradiation with proton and carbon ion beams. The implemented DCCT feedback based control of the current provides good results for magnets of the accelerator in terms of precision and accuracy. However, since the B-Field of the main ring dipoles is not directly controlled, parasitic, time consuming effects cannot be compensated. Hence, the implementation of a B-Field control system offers a major improvement opportunity for the operation. This contribution presents the measurement chain of the proposed solution which is centered around a Hall probe located in the so-called B-train magnet. This approach requires an assessment of the applicability of local Hall probe measurements for this purpose, including the development of a model for relating the respective local measurement to the integral field. Ultimately, the Hall probe has shown characteristics of high accuracy and a measurement uncertainty that is below the overall field error target of 2 units. The model was tested under laboratory conditions and an accurate estimation of the integral field has been observed in the scope of simulations.

In the SIS18 heavy-ion synchrotron at GSI, RF beam phase feedback systems are developed and tested with beam for the damping of coherent longitudinal bunch oscillations. In particular, a beam phase control system is currently commissioned for the damping of longitudinal dipole oscillations. The feedback system has to cope with both, a large RF frequency span (400 kHz to 5.4 MHz) and synchrotron frequencies of up to 6 kHz. It has to be compatible with several beam manipulation schemes such as dual-harmonic, bunch merging, and bunch compression. The system relies on recent upgrades of the SIS18 LLRF topology including a newly developed multi-purpose DSP system that is used for the RF cavity synchronization as well as for RF beam feedback. This paper describes the LLRF concept of the RF beam phase feedback at SIS18 and presents results from machine experiments with beam where an adaptive feedback filter for damping longitudinal dipole oscillations during the whole SIS18 machine cycle was realized and successfully applied. Finally, an outlook will be given towards the full integration into the central control system and towards the SIS100 bunch-by-bunch longitudinal feedback system.

The SIS100 heavy ion synchrotron is the central machine of the FAIR (Facility for Antiprotons and Ions Research) project at GSI. It presents complex challenges due to its features handling high-intensity ion beams from protons up to uranium. It demands sensitive beam diagnostics with robust Machine Protection Systems (MPS). Due to anticipated extreme conditions, one safety subsystem includes LHC-type Beam-Loss Monitors (BLMs). These BLMs play a critical role in beam diagnostics and machine safety, strengthening protection measures by enhancing monitoring capabilities for severe beam losses and triggering safe beam dump requests. These BLMs are gas chamber detectors which aim to prevent beam-induced quenching superconducting magnets and protect other machine components from damage. This document outlines a conceptual study of a Machine Protection System, integrating 168 LHC-type BLMs to safeguard the SIS100 synchrotron. The integration involves upgrading the readout electronic chain and adopting FPGA-based logic firmware to handle intricate rate counting requirements over specified time windows. Additionally, hardware sanity checks are carried out to prevent non-conformities and ensure reliability alongside beam loss rate counting. Overall, the focus on beam loss monitoring for the SIS100 within the FAIR project underscores the necessity for sophisticated diagnostic tools and protective measures to ensure the safe and efficient operation of this state-of-the-art synchrotron.

SIRIUS is a 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS). Recently, investigations of noise sources and the storage ring RF plant identification enabled a fine-tuning of the Digital Low-Level Radio Frequency (DLLRF) parameters. This paper presents the main improvements implemented, which include the mitigation of 60Hz noise from the LLRF Front End and the optimization of the control system parameters. Optimizations in the machine were based on an adjusted model of the SIRIUS storage ring RF plant. Tests with the model's parameters showed that the system's stability was strongly dependent on phase shifts introduced by nonlinearities from the high power RF sources. The new parameters significantly improved the control performance, increasing the bandwidth of the system and reducing longitudinal oscillations. BPM (Beam Position Monitor) and BbB (Bunch-by-Bunch) systems were employed to quantify longitudinal beam stability improvements.

The temporal characteristics of ultra-high dose rate beams delivered for FLASH research are often dictated by machine constraints, making it challenging to compare the outcomes across studies performed at different facilities. To broaden the opportunities for systematic, non-clinical FLASH research, this study explores methods to deliver beams with customizable time structures from a medical synchrotron. The studies are being performed at the center for ion beam therapy and research MedAustron and aim at extracting ultra-high dose rate proton beams in a series of pulses with adjustable dose per pulse, pulse length and pulse separation down to sub-ms levels. This contribution describes the implementation of the extraction methods explored for this application, phase displacement and radio frequency knockout extraction, and presents first measurement results. The measurement setup employs a silicon carbide detector in conjunction with a 20 MHz bandwidth amplifier, enabling intensity measurements with a resolution exceeding the synchrotron revolution period.

With a very low relative charge-to-mass ratio offset of approximately 0.065%, helium (⁴He²⁺) and carbon ions (¹²C⁶⁺) are interesting candidates for being simultaneously accelerated in hadron therapy accelerators. At the same energy per nucleon, helium ions exhibit a stopping range approximately three times greater than that of carbon ions. They can therefore be exploited for online range verification in a detector downstream of the patient during carbon ion therapy. The synchrotron-based MedAustron Ion Therapy Center provides the opportunity to study the feasibility of such a mixed beam-based in-vivo range verification system due to the availability of 120-402.8 MeV/u carbon beams and the ongoing commissioning of 39.8-402.8 MeV/u helium beams. One possibility for creating this mixed beam is accelerating ⁴He²⁺ and ¹²C⁶⁺ sequentially through the LINAC and subsequently “mixing” the ion species at injection energy in the synchrotron with a double injection scheme. This contribution introduces this newly proposed injection scheme, outlines challenges and presents first feasibility estimates obtained through measurements and particle tracking simulations.

In recent years, mixed helium and carbon ion irradiation schemes have been proposed to facilitate in-vivo range verification in ion beam therapy. Such a scheme proposes to deliver both ion species simultaneously, with the idea of performing the treatment with carbon ions, while exploiting helium for online dosimetry downstream of the patient. The center for ion beam therapy and research MedAustron supplies protons and carbon ions for clinical treatment. It is currently being commissioned to additionally provide helium ions for non-clinical research, opening the opportunity for exploring the feasibility of mixed beam irradiation. A key aspect in this context is the slow extraction of the ion mix, which is affected by the relative charge-to-mass ratio offset between the two ions of approximately 6e-4. This contribution analyses differences in the transverse phase space and tune distributions of the two ion species and subsequently discusses first simulation results of the extraction process.

We present a design of the proton FLASH radiation therapy facility using the Brag peak to be built at Stony Brook University Hospital at the Radiation Oncology Department. It includes an injector using a commercially available injector cyclotron (10-30 MeV), fixed field alternating (FFA) gradient beam lines, permanent magnet Fixed Field Alternating Gradient non-scaling variable transverse field fast-cycling synchrotron accelerator with unprecedented kinetic energy range between 10-250 MeV, and a permanent magnet delivery system the FFA gantry. This facility removes limitations of the present proton cancer therapy facilities allowing FLASH radiation to be performed with 40 Gy/s in 100 ms. This allows treatment with the FLASH therapy without magnet adjustments for any proton kinetic energy between 70-250 MeV. The proposal is based on already experimentally proven FFA concept at the Energy Recovery linac 'CBETA' built and commissioned at Cornell University.

An exact solution for the radiation field of a particle in a helical undulator, valid for an arbitrary point in space and an arbitrary particle energy, was obtained by the partial domain method, generalized for the case of spiral motion of a particle. The interface between the regions is a cylindrical surface containing the spiral trajectory of the particle. A comparison is made with the existing solution, which is valid in the far zone at high particle energies.

The National Synchrotron Radiation Research Center houses two accelerators, namely the Taiwan Light Source and the Taiwan Photon Source. It also includes approxi-mately 40 end stations. The center has an information display board system that integrates information from the Instrumentation and Control Group, Experimental Facilities Division, Scien-tific Research Division, Radiation and Operation Safety Division, and User Administration and Promotion Office in the form of interactive display pages. It provides cru-cial information, such as source status, beamline details, and user sign-in data, as well as useful resources, such as end-station training courses and experimental safety approval forms. The system offers diverse use cases tailored to the spe-cific needs of different users. This paper describes how we use the information display board system to improve safety management at the center.

The synchrotron facility and experimental station in the National Synchrotron Radiation Research Center (NSRRC) uses many electrical appliances, the improper use of which can cause fires, resulting in property damage and personal injury. Therefore, the usage of these electri-cal appliances must be assessed. This study conducted a comprehensive inspection and evaluation of the electrical appliances used in NSRRC, including extension cords and electrical connections; this was done to not only reduce the risk of fire but also emphasize the importance of electrical safety habits. We connected an extension cord reel in the NSRRC to a pump or a dehumidifier and used a thermal imaging cam-era to measure the temperature of the cord and these two appliances. We tested the extension cord reel when it was coiled up in the reel and straightened to determine which electrical appliances or extension cord states were prone to high temperatures and fires. The results showed that the extension cord was 18–20°C hotter when it was coiled than when it was straight. Therefore, we recommend that at least two-thirds of the length of the extension cord should be extended out of the reel when it is used.

The Taiwan Photon Source (TPS) BL-02A beamline at the National Synchrotron Radiation Research Center is a curved magnet beamline designed for white light mi-crotomography experiments, wherein biological samples are irradiated with high-energy white light for structural analysis. Experimenters frequently complain of odors when entering the end-station Hutch to change samples, which may be attributed to high concentrations of ozone. Ozone is a toxic gas that is produced when white light radiation reacts with oxygen in the air. Therefore, analyz-ing the ozone concentration distribution within the Hutch is necessary to evaluate safe windows of time for personnel to enter and the type of personal protective equipment that should be used. The TPS operates at a stored energy and current of 3.0 GeV and 500 mA, respectively, with ventilation air condi-tioning turned off in the beamline Hutch. We measured ozone concentrations in regions of white light exposure at the front end (15 cm) and rear end (13.5 cm) of the Hutch, with the light source turned on for 300 s and off for 300 s. We placed the detector at different distances above, below, and to the right of the beam center. Our results demonstrated that more ozone was produced when white light was exposed for a longer duration. At any given distance, the highest amount of ozone was generat-ed above the beam center, followed by to the right side and below the beam center. These findings can serve as a reference for evaluating the health and safety of research-ers exposed to ozone in their work environments.

In 2016 the Australian Synchrotron embarked on the BRIGHT program to build four new insertion device beamlines: Biological Small Angle X-ray Scattering (BioSAX), High Performance Macromolecular Crystallography, Advanced Diffraction and Scattering and Nanoprobe beamlines. To maximize the flux for these very demanding beamlines, cryogenic and short period devices have been selected. In particular a 1.6 m long 16 mm period superconducting undulator, a 3 m long 18 mm period cryogenic undulator (CPMU), 3 m long 17 mm in-vacuum undulator and a 2 m long 48 mm period superconducting wiggler. This report will discuss some of the design considerations and overall parameters of the new insertion devices.

It has been seven years since the Taiwan Photon Source (TPS) started to serve users in 2016. Sixteen beamlines had been installed in the first and second phases of TPS beamline project. The third phase project was also launched in 2021. Considering the experimental hall is more compact and power saving issue, our research aimed to analyze a modified air conditioning system with better cooling efficiency through Computational Fluid Dynamic (CFD) simulation. One twelfth of the TPS experimental hall and two beamlines are modeled.

In late 2023, Thomas Jefferson National Accelerator Facility (Jefferson Lab) funded a Laboratory Directed Research and Development (LDRD) grant dedicated to investigating the impact of radiation on permanent magnet materials. This research initiative is specifically geared towards assessing materials slated for use in the CEBAF energy upgrade. The experimental approach involves strategically placing permanent magnet samples throughout the accelerator, exposing them to varying radiation doses. The simulation code BDSIM is used to first validate the data and then to simulate the effects on future higher energy passes to study the degradation effects on the permanent magnets. In this paper we present the progress of that work.

Beam instrumentation is of critical importance for the operation and optimization of modern particle accelerators. With advancing accelerator technology and the increasing requirements for higher quality beams, it is an ever-present challenge that beam diagnostics must similarly progress. In this talk the instrumentation considered most impactful for the progress of 4th generation storage ring light sources is presented with reference to possible lessons learned, applicability to other accelerators and potential future directions.

The world's smallest carbon ion treatment facility has been commissioned at Yamagata University. The treatment system consists of an ECR ion source, a linac cascade of 0.6 MeV/u RFQ and 4 MeV/u IH-DTL, a 430 MeV/u slow extraction synchrotron, and irradiation systems of a fixed horizontal beamline and a compact rotating gantry using superconducting combined function magnets. The size of the building is 45 x 45 m, realized by placing the irradiation rooms not on the same level as the synchrotron, but above it, connected by a vertical beam transport. The most advanced accelerator technology of this machine is to control the beam range up to 300 mm in 0.5 mm steps without any physical block range shifter. To achieve this range step, 600 beam energies were provided in the synchrotron and in the beam transport and tuned to control the beam size in the treatment room. Initial commissioning and daily/monthly quality assurance were carried out by interpolation of beam energy and gantry angle. After tuning the beam size and correcting the beam axis in the treatment rooms, precise dose measurement was performed for clinical irradiation. After the clinical commissioning, the facility started treatment irradiation in February 2021 with a fixed beam port and in March 2022 with a gantry beam port. After March 2023, the gantry angle was operated with a 15-degree step. By November 2023, 1330 patients had been treated.

The 4th generation synchrotron light sources and energy recovery linacs progress greatly in Japan. The first 4th generation synchrotron light source in Asia, NanoTerasu, has been constructed through a public-private regional partnership, whereas soon SPring-8 is to be upgraded. The energy recovery linac, which features not only high brightness but also sustainability as the cERL, and its related technology such as DC gun injectors have been developed, also. The talk will present an overview and future direction of synchrotron radiation light sources in Japan, with a particular focus on recent advances in NanoTerasu.