sextupole
MOO7M03
Machine learning techniques for design of complex accelerator magnets
58
The design of multipole and other magnets for accelerators is typically an iterative process in which the magnet geometry is optimised for the required beam dynamics properties. Modelling the field for a given geometry can be computationally expensive, so exploring the parameter space can be a time-consuming procedure. The task is particularly challenging when complex field properties are needed (for example, in magnets with several multipole components or with longitudinal field variation). Combined function magnets with several multipole components are particularly useful in accelerators with tight spatial constraints such as an X-ray Free Electron Laser (XFEL). Surrogate models using neural networks can provide a way of rapidly generating possible magnet geometries for given field or beam dynamics requirements. In this contribution, we discuss how machine learning tools may be used to improve the efficiency of the design process for complex accelerator magnets, and present results from a case study based on a combined function magnet for the beam spreader in a future XFEL.
Paper: MOO7M03
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOO7M03
About: Received: 12 May 2026 — Revised: 15 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
MOP1039
FCC-ee Optics Tuning – Towards the reference design
144
The Future electron positron Circular Collider, FCC-ee, is a proposed next-generation facility designed to deliver very high luminosities across a broad beam-energy range, from the Z pole at 45.6 GeV up to 182.5 GeV. Achieving the target performance in the presence of realistic lattice imperfections represents a significant challenge. To address this, a comprehensive commissioning strategy is being developed, featuring dedicated optics configurations, robust beam-based alignment procedures, and advanced optics-correction techniques supported by refined beam-based measurements. In parallel, specifications for the main magnet families, corrector circuits, and required instrumentation are being explored to ensure compatibility with the expected tuning procedures. This contribution summarizes the current status of these developments and outlines the key steps and milestones envisioned on the path toward the reference design.
Paper: MOP1039
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP1039
About: Received: 13 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
MOP1045
Vertical deformation of the 10 TeV muon collider ring for neutrino flux mitigation
165
Muons offer several advantages for circular colliders: as leptons, they allow for high-precision and similar physics reach as larger hadron colliders, while their higher mass suppresses the synchrotron radiation that limits circular electron colliders. The main challenge of muon colliders is the short lifetime of muons. Muon decay generates an intense neutrino flux emitted in a narrow cone tangential to the beam trajectory. To keep the resulting radiation at the Earth’s surface negligible, dedicated mitigation strategies are required. Besides minimizing straight sections, the main mitigation measure under consideration is to periodically deform the beam trajectory and collider ring vertically to spread the neutrino flux over a larger area. This can be achieved by installing all ring magnets on a mechanical system allowing to move them regularly and adding horizontal magnetic field components. However, this affects the collider optics, especially since it introduces vertical dispersion that must be properly matched across the lattice. The present work presents the first studies on the impact of such vertical periodic deformation on beam dynamics and collider performance.
Paper: MOP1045
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP1045
About: Received: 13 May 2026 — Revised: 21 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
MOP7059
The SOLEIL II magnets
763
The SOLEIL II upgrade relies on a lattice combining 7BA and 4BA High-Order Achromat (HOA) cells. Strict compact- ness constraints and energy efficiency objectives have driven the adoption of permanent magnet based technology for the main bending and focusing elements, while quadrupole correctors, sextupoles, and octupoles remain resistive to pre- serve operational flexibility. This paper presents the latest progress in the design, optimization, and prototyping of the SOLEIL II magnet system.
Paper: MOP7059
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7059
About: Received: 13 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7061
Elettra 2.0 magnets and magnetic measurements results
771
The Elettra 2.0 project involves the installation of 648 new electromagnets for the upgrade of the existing light source [1]. Following the design and prototyping phase, the magnet series are currently being manufactured and delivered to Elettra to be suitably characterized before the installation. To this aim, a new magnetic measurement laboratory has been built and equipped during last year. The measurements currently being performed at Elettra consists of the magnetic field quality measurement (for acceptance tests), magnetic field excitation curves, the alignment of multipole magnet, and the 3D magnetic field mapping. This article presents the results of the magnetic measurements performed until now.
Paper: MOP7061
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7061
About: Received: 13 May 2026 — Revised: 15 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
MOP7068
Conceptual magnet designs for MAX 4U
786
The MAX 4U project aims to reduce the natural horizontal emittance of the MAX IV 3 GeV storage ring from 328 pm rad to less than 75 pm rad. A key constraint for the new lattice design is the preservation of the 7-bend achromat structure layout. Each cell is implemented as a single magnet block, which includes an integrated dipole, removable quadrupole pole tips, and stand-alone sextupoles and octupoles. This configuration imposes strict limitations on the level of intervention possible within each block. This contribution presents conceptual magnetic designs and initial crosstalk studies.
Paper: MOP7068
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7068
About: Received: 15 Apr 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
MOP7081
The Canted Cosine Theta HTS sextupole demonstrator of FCC-ee
812
A single-aperture, two-layer Canted-Cosine-Theta (CCT) sextupole magnet using high-temperature superconducting (HTS) ReBCO tape has been developed for the short straight sections (SSS) of FCC through the FCCee-HTS4 project. The magnet was designed, manufactured and tested under cryogenic conditions. Two HTS tapes from two manufacturers have been qualified for this specific application. Design and manufacturing details and cryogenic temperature measurements are presented. This demonstrator represents the first HTS CCT magnet ever constructed.
Paper: MOP7081
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7081
About: Received: 12 May 2026 — Revised: 22 May 2026 — Issue date: 22 May 2026
MOP7166
Advances in magnetic field quality for ZEPTO tunable permanent magnet quadrupole
1040
The Zero Power Tuneable Optics (ZEPTO) project at STFC Daresbury Laboratory has developed several prototype permanent magnet quadrupoles (PMQs) with the largest tuning range so far demonstrated for any PMQ. By moving permanent magnet blocks relative to fixed steel structures that define the flux path,gradient is adjusted whilst homogeneity remains defined by the steel shape. Maintaining stable field homogeneity and magnetic axis position during adjustment remains a challenge that requires extremely high precision in manufacture and assembly to achieve. Based on lessons learned from the latest ZEPTO prototype, which ran for 2 years on Diamond Light Source, we have developed a fourth prototype which will be installed on the CLARA linear accelerator. This has 2 key developments over the previous prototype to overcome difficulties in manufacturing and assembly precision. If measurements show poor magnet harmonics or axis shift as a function of gradient, these are correctable in the new prototype without re-assembling the magnet or re-machining components. We show that by magnetic steel shims in defined patterns we can correct higher order field components, and that by removing rods of material from the yoke in pre-defined patterns we can tune or add field saturation in one half of the magnet to correct magnetic axis movement. This represents the next step into bringing this technology into direct competition with electromagnets in terms of convenience and reliability.
Paper: MOP7166
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-MOP7166
About: Received: 07 May 2026 — Revised: 18 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP2308
Accuracy and stability of lattice correction for the pgraded APS
1295
A well-corrected lattice is essential for the performance of any modern synchrotron light source. Beyond the standard motivations -- such as preserving optimized nonlinear dynamics and maintaining sufficient dynamic and momentum acceptance -- accurate lattice correction is particularly important in APS-U for achieving the predicted emittance reduction associated with insertion-device radiation. In APS-U, lattice characterization relies on response-matrix fitting. Simulations performed during the design phase indicated that the achievable accuracy of such measurements would be limited to the few-percent level, thereby constraining the ultimate lattice correction precision. This paper presents the typical results of the APS-U lattice correction, examines approaches to improving lattice measurement accuracy, and discusses the long-term stability of the corrected lattice.
Paper: TUP2308
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2308
About: Received: 06 May 2026 — Revised: 19 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP2612
Preliminary lattice design to the 1 pico-meter level emittance for the Southern Advanced Photon Source
1382
The pursuit of diffraction-limited storage rings has driven emittance targets into the picometer regime. This paper presents a novel Single Hybrid Multi-Bend Achromat (SH-MBA) lattice design for the Southern Advanced Photon Source (SAPS), targeting an emittance at the 1 pm level. The compact SH‑16BA design, operating at 3.5 GeV with 36 periods and a 945 m circumference, employs high‑gradient quadrupoles, reverse bends, and longitudinal gradient bends. While collective effects such as Intra‑Beam Scattering allow the equilibrium emittance to reach the diffraction limit for hard X‑rays, the most critical challenge lies in nonlinear dynamics optimization. The required sextupole strengths are extremely high, generating nonlinear driving terms three orders of magnitude larger than in typical 4th‑generation sources and restricting the dynamic aperture to about 1 mm. This work demonstrates that achieving a reliable 1 pm-level design will require novel methods to suppress these severe nonlinearities.
Paper: TUP2612
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2612
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP2620
Design and magnetic measurement results of the HALF storage ring magnets
1399
The Hefei Advanced Light Facility (HALF) is a fourth generation synchrotron light source under construction, centered on a 2.2 GeV diffraction limited storage ring (DLSR) with a design natural emittance below 86 pm·rad. The storage ring has a circumference of nearly 480 m and contains 880 magnets in 20 lattice cells, including longitudinal gradient bends (LGB), reverse bends (RB), quadrupoles (Q), sextupoles (S), octupoles (O), and all corrector magnets (CR). As of early 2026, all magnet types except the octupoles had completed series production and factory magnetic measurements. This paper presents the physical design methodology and key magnetic measurement results of the HALF storage ring magnets, and also outlines ongoing studies on Preisach hysteresis modeling and on magnetic crosstalk in selected compact magnet assemblies through three dimensional simulations and stretched wire measurements.
Paper: TUP2620
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2620
About: Received: 15 Apr 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP2626
Dynamic aperture prediction based on machine learning
1406
The dynamic aperture(DA) is one of the most important parameters of nonlinear beam dynamics in storage rings. It describes the transverse phase space region where the motion of a particle can remain stable. In the design and optimization of storage rings, long-term particle tracking is usually required to ensure an sufficient DA. However this process is very time consuming. This study explores the possibility of using machine learning methods for DA prediction. Firstly, several regression models from magnet strengths to resonance driving terms are constructed using different machine learning methods, showing that the use of machine learning can be applied to the nonlinear performance analysis of storage ring lattice. Then predictive regression models from magnet strength to DA are constructed, and the results show that artificial neural network have better prediction accuracy. The method will be further developed for nonlinear analysis and optimization of storage ring.
Paper: TUP2626
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP2626
About: Received: 15 Apr 2026 — Revised: 19 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
TUP7651
Magnet Measurements of the HALF Magnets
1885
The Hefei Advanced Light Facility (HALF), a fourth-generation light source based on a multi-bend achromat (MBA) lattice, is currently under construction. The storage ring consists of 20 cells and requires over 800 magnets. To assess the magnetic field quality and perform magnet fiducialization, several dedicated measurement systems have been developed. These include rotating-coil, stretched-wire, and Hall-probe systems. The field quality of multipole magnets is characterized using the rotating-coil system, while their magnetic centers are determined through single stretched-wire measurements. This paper presents the design of the measurement benches, outlines the corresponding measurement procedures, and reports measurement results.
Paper: TUP7651
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7651
About: Received: 11 May 2026 — Revised: 21 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP7654
Measurements of magnet prototypes for storage ring of Siam Photon Source II
1891
A series of magnet prototypes have been developed for the storage ring of Siam Photon Source II, the second synchrotron light source in Thailand. The prototypes include dipole, combined dipole, quadrupole, sextupole and octupole magnets for half of the Double Triple Bend Achromat (DTBA) lattice. To validate prototype performance, magnetic field characterization was carried out using stretched wire and Hall probe measurement systems. This work reports the measurement results and describes subsequent improvements to both the magnet design and the manufacturing processes.
Paper: TUP7654
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7654
About: Received: 28 Apr 2026 — Revised: 15 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
TUP7668
Development of a Modular Magnet Power Supply with Parallel Operation for the Korea-4GSR Storage Ring
1920
The storage ring of the Korea-4GSR (Korea 4th Generation Synchrotron Radiation) facility currently under construction consists of a total of 1184 magnets, of which 792 are large-capacity magnets requiring rated currents of 140A or 280A. To drive these large-capacity magnets, magnet power supplies (MPSs) are required to support parallel operation in order to minimize the number of MPS types, thereby improving maintenance efficiency and reducing manufacturing costs. In addition, to ensure beam stability and low-emittance beam performance, current stability of less than 10 ppm and accuracy of less than 100 ppm under long-term operation are required during the prototype development. This paper presents a storage ring modular magnet power supply (SR Modular MPS) rated at 140A, which is designed in a modular form with master–slave-based parallel operation capability, allowing the rated output current to be expanded up to 280A through two-unit parallel operation. The proposed MPS can supply both 140A and 280A rated currents to large-capacity magnets using a single MPS type, and satisfies the MPS performance requirements over the entire operating range through a compensation method applied based on operating-condition-dependent characteristics. Experimental results demonstrate that the developed SR Modular MPS achieves a stability of 2.28 ppm and an accuracy of 45.79 ppm in single-unit operation, and a stability of 5.1 ppm and an accuracy of 45.88 ppm in parallel operation.
Paper: TUP7668
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP7668
About: Received: 18 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
TUP8013
Evaluation of orbit correction methods for the Helium Light Ion Compact Synchrotron HeLICS
2056
Within the framework of the Next Ion Medical Machine Study (NIMMS) collaboration at CERN, closed orbit correction schemes are developed for the Helium Light Ion Compact Synchrotron (HeLICS) - a novel synchrotron design in development for cancer treatment. Different options for closed orbit correction are presented, including the possibility of applying beam-based quadrupole alignment without dedicated corrector magnets. The limitations and advantages of the different closed orbit correction methods are evaluated against each other in order to determine the best scheme for HeLICS.
Paper: TUP8013
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP8013
About: Received: 17 Apr 2026 — Revised: 19 May 2026 — Accepted: 22 May 2026 — Issue date: 22 May 2026
TUP8031
Joint Development of Superferric Corrector Magnets for HL-LHC
2079
The HL-LHC project is a major upgrade of CERN’s LHC, aiming to enhance the collider’s integrated luminosity by a factor ten within ten operational years. Endorsed as top priority for the European Strategy for Particle Physics in 2013, the project was formally approved by CERN’s Council in 2015. To achieve its performance goal, HL-LHC relies on several technology drivers. Among the new magnets for the interaction regions, the superferric – named so, because they combine superconducting NbTi coils with iron pole pieces to enhance the magnetic field near the aperture – high-order mode correctors are key in ensuring beam quality and stability, correcting field errors and compensating non-linearities in the magnet lattice. These magnets were the object of a collaboration between CERN and INFN-LASA Milan, first joint project to deliver its full scope to HL-LHC. INFN-LASA was tasked with design, prototyping, and industrialization. Key to the delivery of 54 correctors by 2023 was the early initiation via the INFN MAGIX project, followed by two agreements for prototyping and series production. The collaboration spanned over a decade and benefited from the early involvement of the industrial partner SAES-RIAL. The paper reviews the collaboration, detailing cost structure, schedule adherence, and industrialization process. Focus is on key factors that contributed to the success of the collaboration and lessons applicable to large-scale partnerships for future accelerator projects.
Paper: TUP8031
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-TUP8031
About: Received: 12 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEO1T01
First synchrotron injection attempt into the SuperKEKB HER
2132
A synchrotron injection scheme for the SuperKEKB high-energy ring (HER) was implemented and experimentally evaluated. The lattice at the HER injection point was configured to provide a large horizontal dispersion of –1.6 m, and the sextupoles were optimized accordingly. Because an abort system is located near the injection point, the optics design was constrained to ensure compatibility with the abort-system requirements. Optics solutions were developed to enlarge the dynamic aperture for interaction-point β_y* values of 81 mm, 8 mm, 3 mm, and 1 mm. A systematic procedure of the injection parameters has been established using a turn-by-turn BPM in the ring. The betatron components of the injected beam was successfully removed. Using the optimized optics, synchrotron injection into the HER was successfully demonstrated, followed by the establishment of stable beam–beam collisions and the production of luminosity. As the injection repetition rate was increased, however, an unexpected degradation in injection efficiency was observed, leading to the suspension of the study. These experimental results and possible mechanisms that contributed to the observed injection degradation will be reported.
Paper: WEO1T01
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEO1T01
About: Received: 13 May 2026 — Revised: 21 May 2026 — Issue date: 22 May 2026
WEO5M03
On the optimization of the non-linear performance of 4th-generation light sources
2170
The successful non-linear performance of 4th-generation light sources can be supported through a proper design of the linear lattice. However, important quantities like the injection efficiency and the beam lifetime depend on the optimization of non-linear magnetic fields like sextupoles, octupoles (and sometimes decapoles) in the lattice and therefore on numerical optimization. The underlying quantities to be maximized, are the limits of stable particle motion in the injection plane, the dynamic aperture, and the Touschek lifetime, i.e. the momentum acceptance of the ring. Commonly, multi-objective genetic algorithms are used for the optimization. Alternatively, the resonant driving terms can be minimized. Both approaches need to take the uncertainties introduced by manufacturing tolerances or jitters in the real machine, into account. Using the parameters of the BESSY III storage ring at HZB, Berlin, this paper compares both approaches and tries to develop an efficient optimization strategy for the upcoming technical design phase.
Paper: WEO5M03
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEO5M03
About: Received: 13 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEP1311
Investigations of Non-Linear Optics Control Knobs for the FCC-ee
2257
The non-linear effects that arise from misalignment and field errors have been shown to degrade both the dynamic aperture (DA) and (MA) in simulation of the Future Circular Collider electron-positron machine (FCC-ee). This study focuses on using multipoles, such as octupoles, to control the amplitude detuning and higher-order chromaticity as well as investigation of dedicated non-linear correctors to control affected resonance driving terms (RDTs). These non-linear parameters are often coupled and the relative strength with which lattice elements act on each non-linearity depends on the local optical parameters. Studies were performed on the placement and strength of non-linear lattice elements to develop orthogonal correction knobs and first attempts at higher-order corrections to recover the reduced DA and MA are explored.
Paper: WEP1311
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP1311
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
WEP1601
Nonlinear chromaticity correction for the interaction region of Super Tau-Charm Facility
2336
The Super Tau-Charm Facility is a new-generation electron-positron collider in the beam energy range of 1-3.5 GeV, with a target luminosity exceeding $5×10^{34}\ \text{cm}^{−2}\text{s}^{−1}$ at 2 GeV using a large Piwinski angle and crab-waist collision scheme. However, the required sub-millimeter vertical beta function ($\beta_y^*$ < 1 mm) induce strong nonlinear chromaticity, which severely limits the momentum aperture of the collider rings and leads to a very short Touschek lifetime. To achieve the necessary 1.5% momentum aperture, local correction of the nonlinear chromaticity from the final‑focus quadrupoles is essential. In this paper, we derive the theoretical origin of the nonlinear chromaticity and demonstrate dedicated measures to systematically mitigate these nonlinearities order by order. Specifically, we present an updated modular linear lattice for the interaction region to facilitate nonlinear chromaticity optimization. The second‑order dispersion at the crab sextupoles is also reduced to nearly zero. By implementing a local chromaticity correction scheme up to the third order, we obtain a momentum aperture of 2% for the interaction region.
Paper: WEP1601
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP1601
About: Received: 13 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEP1603
An updated physical design of the super Tau Charm Facility collider rings
2340
The Super Tau-Charm Facility (STCF), proposed by the University of Science and Technology of China, is a next-generation electron-positron collider designed to achieve a luminosity exceeding 5×10^34 cm^-2s^-1, approximately two orders of magnitude greater than that of BEPCII. Large Piwinski angle with the crab waist collision scheme is applied. However, the extremely small βy* (<1 mm) generates very large nature chromaticity. Local chromaticity corrections for both horizontal and vertical planes have been proposed. Touschek lifetime is very challenging due to its low-energy, low-emittance, and high-current. A two-folded lattice has been proposed for the collider rings, with the iterations of version 5. Nonlinear optimization has been carried out with Multi-Objective Genetic Algorithm (MOGA) to maximise the dynamic aperture and momentum acceptance, considering fringe fields and misalignment errors. This paper introduces the updated physical design of the STCF collider rings.
Paper: WEP1603
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP1603
About: Received: 15 Apr 2026 — Revised: 13 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEP4334
Investigations of betatron coupling and horizontal partial snake resonances at low energies in the AGS
2454
Compensation of depolarizing partial snake resonances using betatron coupling has been demonstrated at the Brookhaven AGS. At the nominal acceleration rate, the depolarization of the proton beam from any one of the 82 resonances is too small to optimize the compensation each individual resonance empirically. The compensation therefore requires accurate modeling of the accelerator lattice and accounting of both known sources of such resonance (the helical dipole and applied skew quadrupole fields) and unknown sources (e.g. sextupole feed-down effects). At low energies in the AGS these efforts are complicated by the large optical effects of the helical dipoles and the near-integer vertical tune requires to avoid strong vertical spin resonances. Individual resonances can be investigated by crossing the resonance more slowly, in this case at fixed energies with a slow tune ramp. We report here on progress in both the modeling and experimental investigations into these depolarizing mechanisms.
Paper: WEP4334
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP4334
About: Received: 13 May 2026 — Revised: 19 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026
WEP5018
Ultralow-Alpha Operation with three Families of Sextupoles at the KARA Ring
2599
For more than two decades, the Karlsruhe Research Accelerator (KARA) — KIT’s synchrotron radiation source and accelerator test facility — has been routinely operated in short-pulse mode, which involves reducing the momentum compaction factor. Recent advancements, such as enhanced stability provided by new magnet power supplies, have enabled us to surpass previous limitations in achieving extremely small momentum compaction factors. Based on lattice simulations and the introduction of a single additional sextupole magnet we successfully suppressed the longitudinal chromaticity, allowing the “zero-current” bunch length at KARA to be reduced from the previous 2 ps to below 1 ps. We further report on characterization measurements of this improved operating mode.
Paper: WEP5018
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5018
About: Received: 13 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
WEP5036
Sextupole Beam-Based Alignment for FCC-ee
2640
Designed to succeed the High-Luminosity Large Hadron Collider (HL-LHC), the Future electron-positron Circular Collider (FCC-ee) is a proposed next-generation collider focused on lepton collisions for high-energy physics experiments. Achieving ambitious design goals requires excellent control of the orbit and optics. Off-centre beam passage through the sextupoles results in additional focusing and defocusing, together with coupling due to feed-down effects. The sextupole BBA is considered as an addendum to the quadrupole BBA because it reduces both the dipole kicks in the magnet and the optics perturbations from feed-down effects by reducing the beam offset in the sextupole. Various approaches for the individual and parallel sextupole beam-based alignment (BBA) are considered and compared.
Paper: WEP5036
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5036
About: Received: 13 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
WEP5039
Optics Characterization and Resonance Driving Term Studies for the SPS Crab Cavity Tests in 2025
2652
Following the SPS crab cavity tests in 2025, dedicated machine studies were carried out to investigate optics perturbations introduced by the cavity module and their relation to resonance driving terms. Particular emphasis was placed on identifying possible sextupolar components and assessing their impact on the betatron tune. Measurements using controlled orbit bumps were performed to isolate the cavity’s contribution and to benchmark model predictions. The results provide valuable input for the interpretation of beam dynamics observations during the tests and for the refinement of the SPS optics model in view of future crab cavity operation.
Paper: WEP5039
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5039
About: Received: 12 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
WEP5047
Final Focus Systems at 550 and 1500 GeV
2680
The Final Focus System (FFS) results for CLIC at 1.5 TeV have thus far been estimated using a 3 TeV system operated at reduced energy. Here, we present a dedicated design for the 1.5 TeV stage, where we exploit reduced radiation effects to allow stronger dispersion and weaker chromaticity-correcting sextupoles, thereby mitigating beam transport nonlinearities. The resulting design is 220 m shorter and offers a 50% luminosity gain. The performance of both normal-conducting and superconducting beams at 550 GeV are evaluated using the CLIC FFS, addressing the goals defined by the CLIC and Linear Collider Facility at CERN inputs to the European Strategy for Particle Physics Update.
Paper: WEP5047
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5047
About: Received: 17 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
WEP5071
Measurement of local chromaticity in the LHC
2708
Local chromaticity can be defined as the local variation of the total betatron phase advance with momentum deviation $\delta$, and it can be interpreted as a measurement of the chromaticity generated over a limited segment of the lattice, rather than for the entire ring. It can be a useful tool to understand various insights of the beam operation, in particular how the phase is locally modulated by $\delta$ and how the overall chromaticity builds up along the lattice. The local chromaticity was first evaluated in the Large Hadron Collider (LHC) during the Run 3 commissioning in 2025, when a large RF frequency scan was performed up to $\pm \, $350 Hz, revealing a very large discrepancy with respect to the LHC optics model. This paper presents the methods and the results of the analysis.
Paper: WEP5071
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5071
About: Received: 11 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
WEP5073
Measurement of chromatic resonance driving terms in the LHC
2716
The $3Q_y$ resonance is of particular concern at LHC injection given its potential to degrade the lifetime and the machine dynamic aperture. During measurements of the chromatic linear optics for the 2025 LHC commissioning, a large variation of the $3Q_y$ resonance strength at different momentum deviations $\delta$ was noticed. Further studies have been performed in order to assess the contribution to this variation from higher order multipoles, in particular from octupole and decapole fields. Benchmarking has been performed to the LHC magnetic model pointing to a large discrepancy in the skew-octupole sources present at injection. Methods and results of this analysis are presented in this work.
Paper: WEP5073
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5073
About: Received: 11 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
WEP5075
Optimization with the PETRA IV lattice sextupoles for the mitigation of magnetic field imperfections
2724
As is typical for a design of a 4th generation light source, that of PETRA IV includes strong quadrupolar and sextupolar magnets which makes the beam dynamics of the storage ring sensitive to magnetic field imperfections. In particular, we show that field imperfections in the quadrupoles can drive non-linear resonances which can limit the efficiency of the top-up injection scheme in PETRA IV through a reduction of dynamic aperture. This work explores different strategies, which can be used in operation, of modifying the strengths of the sextupolar magnets to recover a potential loss in the dynamic aperture and injection efficiency.
Paper: WEP5075
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5075
About: Received: 13 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
WEP5303
Data-driven reconstruction of accelerator lattice errors using three beam position monitors
2913
There are numerous experimental techniques to quantify errors in a particle accelerator so that they can be corrected to improve the performance of the accelerator. However, these techniques are often limited in scope, for example, identifying only the errors in quadrupole strengths, sextupole strengths, or the centers of these magnets. In this paper, we propose a data-driven method that can estimate many parameters of lattice elements, including those mentioned above, based solely on many sets of transverse position readings in a section that spans three beam position monitors. Preliminary simulation results will be reported.
Paper: WEP5303
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-WEP5303
About: Received: 13 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
THP2010
Radiation-inclusive kickmap analysis of insertion devices and mitigation strategies for MAX4U
3438
Multi-bend achromat lattices allow for the design of extremely low-emittance electron storage rings and are a cornerstone of the performance of storage-ring-based synchrotron light sources. As part of the proposed MAX IV upgrade, MAX4U, we revise the impact of the insertion devices (IDs) on the beam. We extend the kickmap-based tracking analysis by including the effects of radiation and quantify the resilience of the proposed achromats to the different ID settings and configurations. Finally, we present mitigation strategies, both local to each ID and global, that may be tested experimentally in the current MAX IV 3 GeV ring.
Paper: THP2010
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2010
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP2016
Initial commissioning simulations for the Diamond-II booster
3453
The Diamond-II booster ring is designed to reduce the emittance and the bunch length for efficient injection into the storage ring. Non-optimal commissioning of the injector might increase the dark-time period and the impact on the existing scientific program. This work explores the strategies for booster commissioning to predict and resolve possible issues. The results include tracking simulations with realistic errors such as alignment of magnets and precision of beam diagnostic devices, errors in the magnet gradients, eddy-current effects, measured multipole errors in magnets, pulsed-magnet and injected beam-jitter.
Paper: THP2016
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2016
About: Received: 12 May 2026 — Revised: 19 May 2026 — Issue date: 22 May 2026
THP2029
Towards nonlinear modeling of the combined sextupole-corrector magnets at SOLEIL II
3487
The SOLEIL II sextupoles are equipped with additional windings to provide normal and skew dipole corrections. Accurate modeling of these combined-function sextupole magnets are particularly challenging due to magnetic saturation, hysteresis, and internal cross-talk between channels. Based on 3D magnetic simulations, polynomial, interpolation-based, and neural-network models were developed to reproduce the saturation and cross-talk effects. These nonlinear models were validated on the first prototype magnet, providing preliminary confirmation of their reliability and demonstrating the feasibility of implementing sextupole-corrector magnets in the SOLEIL II storage ring.
Paper: THP2029
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2029
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP2035
Simulated commissioning and lattice robustness studies for BESSY III
3499
BESSY III will be a fourth-generation synchrotron light source that aims to deliver diffraction-limited, extremely brilliant soft X-rays, with the goal of becoming a key instrument for discoveries in materials and energy research. During the current design phase, extensive simulation studies are being performed to evaluate and improve the robustness and reliability of the candidate storage ring lattice. The robustness analysis allows a direct comparison of the expected lattice performance and sensitivity with that of other fourth-generation facilities under realistic error conditions. Building on this, the simulated commissioning process aims to recover optimal machine performance by mitigating the impact of imperfections originating from magnet misalignments and magnetic field errors. This work quantifies the achievable performance of the machine by simulating the full commissioning sequence, including beam-transmission optimisation, sextupole ramp-up, RF-cavity correction, beam-based alignment (BBA), orbit correction, and LOCO-based optics correction. After carrying out the lattice correction, the off-axis injection possibility and the Touschek lifetime are evaluated. Although the preliminary results provide essential feedback for defining the commissioning strategy and enhancing the overall resilience of the BESSY III lattice design, they do not yet include the complete error set.
Paper: THP2035
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2035
About: Received: 11 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP2051
Insertion devices characterization at the SLS 2.0
3544
Accurate measurement of high-order multipoles in insertion devices is crucial for meeting the beam-dynamics requirements of Swiss Light Source 2.0. A beam-based method using transverse tune-shift measurements can effectively identify sextupole, octupole, and higher-order magnetic components under normal operating conditions, avoiding the need for dedicated magnetic tests. Among the upgraded insertion devices—planar, in-vacuum, and knot-type—only the knot-type device shows significant multipole components beyond sextupole, reaching octupole order. This study focuses on the knot-type device, which is expected to be used in SLS 2.0 and in other modern synchrotron facilities, presenting measurements and comparisons with simulation results.
Paper: THP2051
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2051
About: Received: 22 Apr 2026 — Revised: 06 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
THP2053
STATUS OF HIGH BRIGHTNESS OPTICS FOR THE DIAMOND-II STORAGE RING UPGRADE
3548
We report the status of the high-brightness, low-beta optics for the Diamond-II storage ring upgrade. Investigations into the dependence of lifetime and injection efficiency on betatron tunes will be presented. MOGA optimisation studies have been conducted to improve the nonlinear performance, including by increasing the number of sextupole families and varying the octupoles strengths. We present complementary methods to improve the nonlinear dynamics by optimizing second and third order tune-shifts as well as the nonlinear chromaticity. Finally, we report the impact of insertion devices on lifetime and dynamic aperture and present studies of the injection process.
Paper: THP2053
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2053
About: Received: 11 May 2026 — Revised: 17 May 2026 — Accepted: 17 May 2026 — Issue date: 22 May 2026
THP2056
Linear and non-linear optics optimisation for the Diamond-II storage ring
3560
The design performance of the 3.5 GeV Diamond-II low-emittance electron storage ring has been studied as a function of the linear and non-linear lattice tuning parameters. A Multi-Objective Genetic Algorithm (MOGA) has been implemented and refined to optimise both the beam lifetime and the injection efficiency for off-axis injection. The sextupole magnets have been further split into ten families, according to their local linear optics, with each family varied independently as part of the MOGA optimisation; if necessary, the resulting chromaticity is corrected with a subset of the sextupoles to be within an operational range. In addition, the tune and the strengths of the two families of octupoles have been varied as part of the MOGA search. The simulations have been run on 5 machine error seeds, including misalignment, field strength and multipole errors, to obtain a solution which is robust against machine imperfections. The results of the optimisation are presented alongside a comparison of the baseline performance.
Paper: THP2056
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP2056
About: Received: 13 May 2026 — Revised: 18 May 2026 — Issue date: 22 May 2026
THP4011
Absolute energy and machine length calibration in the SPS
3873
This contribution presents the results of a recent absolute-energy and machine-length calibration of the CERN Super Proton Synchrotron (SPS) using two different particle species on the same magnetic cycle. A recent review of the SPS ring geometry and magnet alignments resulted in a change of machine circumference in the optics models to better approach the as-built machine. This measurement aims at measuring the real machine circumference based on the absolute energy calibrations, which then allow to accurately determine the circumference from the revolution period. The measurement repeats a similar exercise performed in the early 2000s, using the magnetic center of the sextupole as a reference, and complements using BPMs centers as well. Comparison between new and old measurements as well as models is shown.
Paper: THP4011
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP4011
About: Received: 11 May 2026 — Revised: 20 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
THP4090
Implementation of multi-energy extraction configurations at MedAustron
4071
Moving from extracting one single energy per cycle to multiple energies promises improvements in time and power budgets of medical synchrotrons. To ensure reproducible and accurate beams for treatment, hysteresis effects must be considered. To avoid losses during energy changes, the beam has to be moved away from the extraction resonance. Different methods of moving the working point were compared regarding their robustness, adaptability and speed by means of measurements and Xsuite simulations. The measurements were taken at the synchrotron facility MedAustron. The methods are devised for the PIMMS-based lattice with one resonant sextupole and off-momentum operation, and differ in how the working point is shifted during the energy change regarding the timing of element ramps and off-momentum contributions.
Paper: THP4090
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP4090
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP4095
Automated minimization of uncontrolled beam loss for slow extraction from SIS18
4087
The GSI heavy ion synchrotron SIS18 delivers ion beams via slow extraction to various experiments, for a wide range of ion species, beam energies, and spill lengths. For the upcoming FAIR Early Science program, extraction intensities of more than 1E9 uranium ions per second are required at energies up to about 1 GeV/u. One of the most important tasks for the slow extraction is limiting uncontrolled particle losses. Limits arise from the requirement to avoid damage of the extraction septa and to minimize the activation of accelerator components. For the highest expected intensities, the limits are a few percent only. That requires a robust optimization of the machine settings. Therefore, automated schemes using numerical optimizers are developed at GSI and tested for quadrupole driven and rf ko slow extraction, in simulation as in measurements. We will report on first results that demonstrate the fast convergence of the observed transmission toward similar values, both in the simulation model and in the measurements.The validated simulation model allows for important insights into the optimized settings.
Paper: THP4095
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP4095
About: Received: 11 May 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
THP5303
Application of the nonlinear optics from off-energy orbits method at the SIRIUS Storage Ring
4188
The applicability of the Nonlinear Optics from Off-Energy Closed Orbits (NOECO) method to the SIRIUS storage ring is investigated. Off-energy orbit response matrices (OEORMs) were measured and used for sextupole strength calibration through a Levenberg-Marquardt (LM) fitting procedure with Tikhonov regularization. The fitted strengths reproduced the measured chromaticities with reasonable accuracy and were consistent with control system estimates. Analysis of the OEORM Jacobian revealed strong correlations among sextupole family signatures, indicating significant quasi-degeneracies in the inverse problem. Machine experiments and model-based simulations showed that localized perturbations are redistributed across correlated families, especially in the presence of small optics mismatches. The results indicate that OEORM-based calibration is feasible at SIRIUS, although its resolving power is fundamentally limited by parameter correlations and model imperfections.
Paper: THP5303
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5303
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP5319
Beam-based alignment for sextupoles via parallel optimization
4207
We propose a method to perform beam-based alignment measurement for multiple sextupoles simultaneously by minimizing the induced orbit shifts from sextupole modulation through parallel local orbit optimizations. The parallel optimization is made possible by using local orbit bumps as knobs and separating the induced orbit kicks through model-based response matrices. The approach reduces slow, multi-knob optimization problems into multiple fast, single-knob optimization problems. The method is demonstrated in simulation.
Paper: THP5319
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5319
About: Received: 10 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP5329
Dynamic aperture optimization for the Ring-based Electron Cooler
4232
Electron Ion Collider (EIC) will benefit from cooling protons at the highest collision energy (γ=294). The required cooling can be provided by the Ring Electron Cooler (REC) - an RF-based non-magnetized electron cooler employing an electron storage ring. As stored electrons cool the EIC protons, their emittance is gradually increased by both the intra-beam and beam-beam scattering. To counteract the heating of electron bunches, eighteen dedicated damping wigglers are utilized. These wigglers require substantially non-linear field with peak value of 2.4 T, occupy a large portion of the electron storage ring, and dominate beam dynamics in the REC. In this paper we describe our approach to maximizing dynamic aperture in the REC, which includes careful optimization of wigglers parameters and development of an elaborate correction scheme for non-linear beam dynamics.
Paper: THP5329
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5329
About: Received: 12 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP5609
Dynamic aperture optimization based on the convexity of third-order resonance driving term variations
4291
Reducing the longitudinal variation of third-order resonance driving terms (RDTs) is much more effective in enlarging storage ring dynamic aperture (DA) than minimizing third-order one-turn RDTs. Recently, we proved the convexity of the quantitative expression for third-order RDT variations. Then, an efficient numerical method for DA optimization was developed, where a high-quality initial population for an intelligent algorithm is generated with a Gaussian distribution based on this convexity. In this paper, we study the impact of the variance of the Gaussian distribution on the optimization performance of this method. It is found that the method shows good optimization performance for small variances, and that the performance remains robust even at a very small variance. In addition, different intelligent algorithms perform well with a small Gaussian variance.
Paper: THP5609
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5609
About: Received: 15 Apr 2026 — Revised: 15 May 2026 — Accepted: 16 May 2026 — Issue date: 22 May 2026
THP5610
Storage ring nonlinear optics correction based on closed orbit bump
4294
This paper presents a new method for nonlinear optics correction of storage ring lattices, which is based on locally generated orbit bumps and the corresponding response matrices. This method is conceptually similar to nonlinear optics from off-energy closed orbits (NOECO), but can be applied to the situation with harmonic sextupoles. Instead of off-energy closed orbits, it exploits the feed-down effects of sextupoles with generated local bumps to directly probe the sextupole components of a lattice. A second-order bump response matrix is constructed from the difference between orbit response matrices measured with positive and negative local bumps. A least-squares fitting procedure is then applied to minimize the difference between measured and model second-order bump response matrices, from which sextupole strength correction can be obtained. Preliminary simulations on the Hefei Advanced Light Source lattice demonstrate the theoretical viability of the method, though high sensitivity to realistic residual errors poses practical challenges that require further investigation.
Paper: THP5610
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5610
About: Received: 13 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THP5623
Toward a robust TPS-II 6BA lattice
4319
The Taiwan Photon Source upgrade (TPS-II) study aims to realize an ultralow emittance lattice compatible with the existing TPS tunnel. This work presents an updated 6BA lattice design with a natural emittance of 67 pm-rad at 3 GeV, followed by an preliminary evaluation of its robustness study under machine errors. A key innovation in this design is the strategic integration of sextupole components within the dipole magnets. This approach effectively flattens the amplitude-dependent tune shift (ADTS) and expands the dynamic aperture (DA) while preserving the momentum acceptance (MA). The results establish a feasible and robust path toward the next phase of TPS-II lattice development and engineering integration.
Paper: THP5623
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5623
About: Received: 06 May 2026 — Revised: 19 May 2026 — Accepted: 20 May 2026 — Issue date: 22 May 2026
THP5632
Theoretical assessment of steady-state microbunching (SSMB) for PAL-EUV
4333
This study presents a theoretical investigation of steady-state microbunching (SSMB) within the design framework of the PAL-EUV ring. An analytic longitudinal dynamics model that includes laser-induced energy modulation, radiation damping and quantum excitation, and nonlinear momentum compaction is formulated to examine whether the baseline ring parameters can support sustained microbunch formation. Using this framework, we evaluate the required energy-chirp strength, the stability conditions for microbucket formation, and the expected radiation power under laser modulation. The analysis further identifies the conditions under which SSMB can be sustained, and provides key guidance for assessing its applicability to the PAL-EUV. These results establish a foundation for subsequent feasibility studies and future experimental development.
Paper: THP5632
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THP5632
About: Received: 18 May 2026 — Revised: 20 May 2026 — Issue date: 22 May 2026
THV5301
Design of NSLS-II lattice with complex bend replacement
4422
The demands of a higher-brightness photon beam push the electron beam emittance of storage rings toward a diffraction-limited level. The complex bend lattice offers a new approach to achieve low beam emittance. To pave the way for a full lattice upgrade, NSLS-II is planning to replace two existing dipoles with complex bends as a feasibility demonstration. This paper presents the design of the NSLS-II lattice with high-gradient complex bend replacement. Nonlinear beam dynamics are optimized to provide sufficient dynamic and momentum apertures for off-axis injection and reliable operation. In addition, the robustness of the optimized lattice to realistic errors is also evaluated.
Paper: THV5301
DOI: reference for this paper: 10.18429/JACoW-IPAC2026-THV5301
About: Received: 13 May 2026 — Revised: 18 May 2026 — Accepted: 21 May 2026 — Issue date: 22 May 2026