collimation
MOPB037
Orbit alignment study in the collimation section at the European XFEL
142
Orbit alignment plays an important role in free-electron laser (FEL) facilities, particularly in the collimation section, where multipoles are strategically positioned near the collimators as part of the specialized optics design. At the European XFEL, a strong dependence of lasing performance on the orbit in the collimation section has been observed. This study focuses on calibrating the central positions of the collimators using an orbit bump scanning technique combined with beam loss detection. Additionally, the influence of orbit alignment in the collimation section on lasing performance was systematically investigated, offering valuable insights into optimizing FEL operation.
Paper: MOPB037
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB037
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPB063
Spatial polarization distribution measurements of gamma rays produced by inverse Compton scattering
194
Highly polarized MeV gamma rays, produced by Laser Compton Scattered (LCS) of a polarized laser with an electron beam, offer a unique probe for basic and applied physics research. As the polarization characteristics of these gamma rays vary with the position of the beam cross section, it is essential to understand the polarization properties when using polarized gamma rays * . However, detailed measurements of the two-dimensional spatial polarization distribution have not yet been conducted. In the UVSOR synchrotron facility, a polarimeter was developed to measure the spatial polarization distribution of linearly polarized gamma rays. The polarimeter is based on asymmetry measurements of the Compton scattering cross section. In this conference, we will report on measurement results of the spatial polarization distribution of linearly and circularly polarized LCS gamma-rays. The polarization axis of the polarized gamma rays was clearly measured to vary with scattering and azimuth angle. In the near future, we plan to use the developed polarimeter to also measure the spatial polarization distribution of gamma rays generated by an axially symmetric polarized laser ** .
Paper: MOPB063
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPB063
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 01 Jun 2025 — Issue date: 05 Nov 2025
MOPM008
Towards a High Luminosity LHC with even higher performance
278
The High Luminosity LHC (HL-LHC) project aims to increase the integrated luminosity of CERN’s Large Hadron Collider (LHC) over its exploitation era up to the end of 2041 by an order of magnitude compared to the initial LHC design value. This requires doubling the bunch intensity along with several other important changes to the LHC configuration. Dedicated beam experiments in the LHC and its injectors have already demonstrated the feasibility of reaching many of the HL-LHC project design parameters, and simulations show that some parameters could be pushed to further increase the integrated luminosity or used as mitigation measures against potential shortcomings. This paper presents a review of the latest experimental results and the possible reach of the final HL-LHC parameters.
Paper: MOPM008
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM008
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM014
Overview of power deposition profiles in the LHC off-momentum cleaning section in Run 3
302
Off-momentum losses at the start of the LHC acceleration ramp in proton runs gave rise to multiple beam dumps by exceeding Beam Loss Monitor (BLM) thresholds in the momentum cleaning insertion (IR3). Accurately estimating the power deposition profiles in IR3 is necessary to determine where BLM thresholds can be optimized, thereby reducing unnecessary beam dumps and improving machine availability and performance. Understanding the loss limits in IR3 is crucial for future High-Luminosity LHC (HL-LHC) performance. In this study, we present FLUKA power deposition results and introduce a newly developed simulation model for BLM benchmarking in IR3. We provide a comprehensive overview of the power deposition in magnets and collimators, identifying potential bottlenecks in the system. Our simulations were benchmarked against multiple fills from 2023 and 2024 that led to beam dumps. The obtained results provide a deeper understanding of the IR3 collimation performance in view of HL-LHC operation in IR3.
Paper: MOPM014
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM014
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM025
Advancing the feasibility study of the ALICE fixed-target experiment using crystal-assisted halo splitting with HL-LHC lead ion beams
346
The Large Hadron Collider (LHC) at CERN is the world’s most powerful particle accelerator, capable of colliding proton and lead ion beams at energies up to 7 ZTeV. ALICE, one of the LHC’s key experiments, is designed for studying heavy-ion collisions. A proposed fixed-target experiment within ALICE involves directing a portion of the beam halo, extracted using a bent crystal, onto an internal target positioned a few meters upstream of the detector. For proton beams, this configuration has already demonstrated effective particle flux delivery to the target while operating safely alongside standard beam-beam collisions. However, with lead ion beams, the beam halo comprises nuclei of varying charge, mass, and magnetic rigidity, posing additional operational challenges. This paper presents an analysis of the expected performance, based on multi-turn particle tracking simulations using a detailed LHC model.
Paper: MOPM025
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM025
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM032
Simulations of losses from fast instabilities in the FCC-ee
374
The electron-positron Future Circular Collider (FCC-ee) is a proposed high-energy lepton collider that aims to reach unprecedented luminosity and precision in the measurement of fundamental particles. To fully profit of such performance, it is crucial to keep detector backgrounds under control and operate the machine safely. Due to the high stored beam energy and to a number of complex operational features required at FCC-ee (e.g. the top-up injection scheme), controlling the backgrounds to the physics experiments becomes even more challenging. Recent studies on collective effects have shown that high impedance in the FCC-ee can lead to fast rise-time instabilities, where the beam amplitude grows exponentially, leading to beam loss within a few turns. Although a feedback system is being developed to mitigate this instability, failure scenarios of this feedback system need to be explored. This paper presents the study of the effects of this instability, in order to understand the possible implications for the machine and the experiments.
Paper: MOPM032
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM032
About: Received: 21 May 2025 — Revised: 30 May 2025 — Accepted: 01 Jun 2025 — Issue date: 05 Nov 2025
MOPM035
Comparison of Xsuite simulations with measured backgrounds at SuperKEKB
386
Xsuite is a collection of packages developed to simulate beam dynamics in particle accelerators. It includes Python modules (Xobjects, Xpart, Xtrack, Xcoll, Xfields, Xdeps) that can be seamlessly integrated with one another and with both accelerator-specific and general-purpose Python tools, enabling the study of complex simulation scenarios. The Xcoll module, developed for collimation studies, allows the integration of beam-matter interaction simulations in the tracking through different available scattering models, including those in the BDSIM/Geant4 toolkit. Originally developed for the Future Circular e+e- Collider (FCC-ee) collimation simulation needs, the Xsuite-BDSIM/Geant4 interface is now deployed in full production for FCC-ee collimation studies. A key aspect of such studies relying on complex simulations is their benchmarking against measured data. This paper presents a first comparison of Xsuite collimation simulation results with measured data at the SuperKEKB e+e- collider.
Paper: MOPM035
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM035
About: Received: 28 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM036
Beam losses due to beam-residual gas interactions in the FCC-ee
390
The Future Circular electron-positron Collider, FCC-ee, is a design study for a luminosity-frontier and highest-energy e+e- collider with a 91 km circumference. In a circular machine, the interactions between the beam particles and the residual gas in the vacuum chamber may degrade the beam quality, potentially affecting the beam lifetime and the collider luminosity, and cause local beam losses. In addition, experimental backgrounds may be increased. Ideally, the vacuum system must be able to keep vacuum conditions sufficiently good so that beam-residual gas interaction effects are tolerable for collider operation. This paper presents a study of the beam loss distribution arising from beam-residual gas interactions in the FCC-ee, together with beam-gas lifetime estimates.
Paper: MOPM036
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM036
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM047
Laser Compton backscattering for precision beam intensity control in the FCC-ee electron-positron collider
429
In this study, we explore the application of laser-driven Compton backscattering (CBS) as a method to precisely adjust and regulate the intensity of colliding particle bunches in the Future Circular Collider (FCC-ee). Maintaining a tightly controlled charge balance between collision partner bunches within a 3–5% tolerance is critical for mitigating the impact of beamstrahlung on bunch length and preventing flip-flop instabilities. We present a realistic design for the CBS optical beamline and provide detailed simulation results that demonstrate its performance in the FCC-ee. Our analysis includes the distribution of scattered positrons, illustrating the feasibility of CBS for achieving the stringent intensity control requirements in this next-generation collider.
Paper: MOPM047
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM047
About: Received: 28 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPM063
Collimator damage study for the Diamond-II storage ring
462
To understand the risk of damage to the collimator blades and the permanent magnets in Diamond-II, the BDSIM code has been used to model the beam losses. To improve the accuracy, the engineering model and 3D field maps have been used to build the machine model. Energy deposition in the main storage ring components and the fluence of secondary particles (particularly neutrons) have been determined. This paper explains the simulation process and give the BDSIM tracking results.
Paper: MOPM063
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM063
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
MOPM069
Power deposition studies for the FCC-ee halo collimation system
486
The Future Circular Collider (FCC-ee) at CERN requires a betatron and momentum collimation system for reducing particle backgrounds in the detectors, and for protecting the machine in case of excessive beam losses. The system is composed of primary and secondary collimators, which will be housed in one of the technical insertions of the 91 km ring. In this paper, we present a first assessment of the beam-induced power deposition in the collimators using FLUKA Monte Carlo simulations. We show that dedicated shower absorbers are needed in the collimation insertion, which intercept secondary particles from the halo collimators and reduce the energy leakage to the environment. A first optimization of the shower absorber configuration is presented, considering different absorber positions and absorber lengths. We demonstrate that the power absorption of the betatron collimation system can be increased from about 50% to over 80% by adding two shower absorbers between primary and secondary collimators.
Paper: MOPM069
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM069
About: Received: 27 May 2025 — Revised: 22 Oct 2025 — Accepted: 22 Oct 2025 — Issue date: 05 Nov 2025
MOPM103
A proposal of a momentum collimator in RHIC warm section for controlling experimental background at sPHENIX
563
One of the issues that the AuAu 100 GeV physics program in 2024 in RHIC encountered was background in the sPHENIX MVTX detector, which causes autorecoveries and preventing continuous data taking. Beam studies and track simulations performed to understand the source of the background and potential measures to control it have led to the conclusion that off-momentum particle loss was an issue. This article will focus on a proposal of a momentum collimator in warm sections in RHIC to control the MVTX background. We will elaborate the selection of the locations for the collimator, the strategy of generating substantial horizontal dispersion there, the required additional powering scheme for selected quads and the optimization of the figure-of-merit for momentum collimation.
Paper: MOPM103
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPM103
About: Received: 29 May 2025 — Revised: 04 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPS018
Demonstrating the feasibility of a double-crystal fixed-target experimental physics setup through the TWOCRYST project in the LHC
627
The TWOCRYST proof-of-principle experiment at the LHC is an initiative to demonstrate the feasibility of a double-crystal setup for fixed-target physics experiments. Such a setup could enable spin precession studies of charmed baryons in the TeV energy range in the HL-LHC era. Major milestones in this project have recently been achieved, including the successful construction and testing of critical components such as the 4~mm and 7~cm long bent silicon crystals required, a new combined fixed-target and crystal goniometer for accurate angular positioning, and two Roman pot stations equipped with advanced tracking detectors. This contribution summarizes the status of the hardware, the results from the first machine development studies to prepare for the measurements with the crystals in 2025, and a detailed plan for the beam tests with the full TWOCRYST setup.
Paper: MOPS018
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS018
About: Received: 19 May 2025 — Revised: 03 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
MOPS019
Simulated beam performance of the TWOCRYST proof of principle experiment at the LHC
631
TWOCRYST is a machine test designed to demonstrate the feasibility of an in-vacuum fixed-target experiment for the first direct measurement of the magnetic and electric dipole moments of short-lived charm baryons. This setup exploits crystal channeling using two bent crystals. The first one is similar to the existing crystals used in the LHC for beam collimation, deflecting the beam halo particles from the proton beam onto a target. The second one - a 7 cm silicon crystal - induces spin precession in the secondary particles produced in the target. 2D detectors in movable Roman pots will track the distribution of these channeled particles. A new silicon pixel detector and a fiber tracker (formerly used by the LHC ATLAS-ALFA experiment) are planned for installation in the LHC along with the two crystals in early 2025. Xsuite simulations have been performed to reproduce the multi-turn beam dynamics of the channeled beam halo and the particle distribution expected at the detectors. The LHC configurations required for the planned measurements have also been simulated, with the results used to specify the required detector performance in preparation for benchmarking against real data.
Paper: MOPS019
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS019
About: Received: 20 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
MOPS020
The TWOCRYST fibre tracker: A detector to characterize precession crystals at the LHC
635
A fixed-target experiment using two bent crystals is proposed to study the magnetic and electric dipole moments of short-lived charm baryons with unprecedented precision in the LHC. This will be achieved exploiting crystal channeling into a first crystal to extract the beam halo and then into a 7 cm long silicon crystal capable of inducing a measurable spin precession to the particles of interest. TWOCRYST is a proof-of-principle machine test scheduled for 2025, to test this setup and address the feasibility of the final experiment under LHC beam conditions. One main goal is the study of the channeling efficiency in this long crystal at TeV energies, requiring a 2D detector in movable Roman pots. The TWOCRYST Fibre Tracker, coming from the LHC's ATLAS-ALFA experiment, is a high-precision tracking detector with ten layers of crossing scintillating fibers coupled to multi-anode photomultipliers, and read out using compact front-end electronics. Intense refurbishment work was required on to adapt the detector to the purposes of TWOCRYST. This contribution summarizes the tracker specifications as derived from beam dynamics simulations and the results of tests prior to its installation.
Paper: MOPS020
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS020
About: Received: 20 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
MOPS022
Investigation on injection-related beam loss at SuperKEKB
639
The current achieved highest luminosity at SuperKEKB is only one-tenth of the design value, and beam injection is one of the most serious issues in achieving the target luminosity. Recent operations in both the HER and LER rings have shown insufficient injection efficiencies and detector backgrounds. The achieved injection efficiency falls short of the required level, sometimes leading to difficulties in injecting the beam at high current values. Following each injection, significant signals from particle losses are detected in several Belle II detector components, particularly the vertex detector, resulting in saturating the data acquisition with a dead time exceeding 10ms. The complexity of the injection, and critical factors like injected beam quality, beam lifetime, dynamic aperture, machine errors, nonlinearity, as well as the collimation system, makes the optimization challenging. Detailed injection simulations are essential to understand the issues of the injection and guide adjustments to maximize the injection efficiency and mitigate the injection background. This paper presents the findings of HER injection simulations and their experimental validation.
Paper: MOPS022
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS022
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 06 Jun 2025 — Issue date: 05 Nov 2025
MOPS029
High Luminosity LHC collimation system performance for different optics configurations
663
The High Luminosity Large Hadron Collider (HL-LHC) presents significant collimation challenges due to its high stored beam energy. An effective collimation system is critical for ensuring stable operation, protecting the superconducting magnets and minimizing background to the experiments. This paper examines the current baseline collimation configuration and potential changes to the collimation insertion optics to improve the performance in various areas, for both proton and heavy ion beam operation. The study encompasses on- and off-momentum beam loss simulations across various stages of the operational cycle. Collimation performance is assessed based on leakage to superconducting magnets, as well as losses on the tertiary collimators, to probe this source of induced background to the experimental detectors.
Paper: MOPS029
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS029
About: Received: 28 May 2025 — Revised: 14 Jun 2025 — Accepted: 14 Jun 2025 — Issue date: 05 Nov 2025
MOPS030
Xcoll-BDSIM coupling for beam collimation
667
Xsuite is a comprehensive simulation toolkit for accelerator physics, with Xcoll serving as the dedicated module for collimation studies. These studies involve tracking particles through an accelerator and simulating their interactions with matter, taking into account non-linear elements and large betatron and off-momentum deviations. Particle-matter interactions can be modeled using an internal scattering model, Everest, or coupled to external codes. This paper presents the integration of Xcoll with the Geant4 libraries by utilizing the Beam Delivery Simulation (BDSIM) code. This coupling enables efficient tracking of diverse particle species through materials, along with realistic simulations of energy deposition and secondary particle production. The implementation is designed to be flexible, supporting the inclusion of detailed collimator geometries, beam-gas interactions, and crystal channeling effects.
Paper: MOPS030
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS030
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
MOPS031
Preliminary results of crystal channelling optimisation in the LHC using reinforcement learning
671
The Large Hadron Collider (LHC) can operate with high intensity proton and heavy ion beams, both of which require a collimation system to ensure an efficient operation and to protect against damage to sensitive equipment along the ring. The crystal collimation scheme using bent silicon crystals as primary collimators was therefore introduced to improve the collimation efficiency for heavy ion-beams. The first operational deployment of crystal-assisted collimation was achieved in the 2023 Pb run. This demonstrated the required performance gain to safely handle high intensity ion beams, but undesired crystal rotation led to the loss of optimal performance during physics fills. The cause of this is thought to be mechanical deformation of the goniometer due to heating related to beam impedance effects. Hence, a conventional numerical optimiser was deployed to monitor and compensate for crystal angular errors based on a set of beam-loss monitors. The problem at hand, allows for the use of machine learning techniques to ensure continuous optimal channelling, minimising convergence time and eventually the optimization of crystals in multiple planes in parallel.
Paper: MOPS031
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS031
About: Received: 24 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPS032
Operational deployment of automatic angular alignment for LHC collimators
675
The Large Hadron Collider (LHC) features a collimation system that protects the machine against beam losses that may induce the loss of superconductivity in some exposed lattice magnets. Thus, optimal cleaning performance must be ensured at all times. The collimation system encompasses more than 100 collimators whose settings are organised in a well-defined transverse multi-stage hierarchy. A collimator alignment toolset has been developed over the years to automate the alignment of the system during beam commissioning. During alignment, the collimator jaws used to be kept parallel to the central beam orbit. However, further tightening of the collimation hierarchy to improve the β* reach is only possible if the collimator jaw angles are precisely adjusted to compensate for any mechanical or orbit tilts. Advanced alignment procedures have therefore been developed to compensate for these effects. The first operational deployment of jaw angle has been achieved in the 2024 run. The commissioning results leading to this milestone are reported in this paper, together with the optimisation of parallel jaw alignment and an overview of the operational architecture.
Paper: MOPS032
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS032
About: Received: 23 May 2025 — Revised: 01 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
MOPS076
Coupling of codes for modeling high-energy-density conditions in fourth generation light sources
774
As previously described*, high-intensity beams of ultra-bright light sources present new machine protection concerns by creating high-energy-density (HED) conditions in beam-intercepting components. Simulating these HED conditions required us to develop a method for coupling three codes for particle dynamics (elegant), particle-matter interaction (MARS/FLUKA), and hydrodynamics (FLASH). This paper discusses the recent advancements made toward this effort including the use of phase and temperature dependent thermal properties such as thermal conductivity and specific heat, transition from MARS to FLUKA, and improved liquid phase dynamics. For benchmarking purposes we compare simulation results with experimental data collected during the final run of the Advanced Photon Source (APS) ring as well as observations of collimator surface damage following the first user run of the upgraded machine. This methodology is also used to make predictions of collimator damage in future APS-Upgrade (APS-U) runs and to examine locations where synchrotron radiation may lead to HED conditions.
Paper: MOPS076
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS076
About: Received: 30 May 2025 — Revised: 02 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
MOPS138
Simulation of machine-induced background to ALICE in the 2023 LHC ion run
825
During the 2023 ion run at the LHC, where crystal collimation was regularly adopted for the first time, strong background levels were observed at the Inner Tracking System (ITS) of the ALICE detector. Some of the readout chips became saturated, causing losses of angular acceptance. This background was mitigated using a dispersion knob in the beam optics, letting some residual background remain. Considering that the next upgrade of the ALICE ITS foresees a further reduction of the interaction chamber aperture, understanding the mechanisms leading to this background appears critical to envision appropriated mitigation solutions. Preliminary studies showed that this background was related to losses at the upstream tertiary collimator (TCT), impacted by 207Pb82+ ions issued from beam interaction with the crystals of the primary collimation stage. Based on FLUKA simulations, this paper investigates the propagation of the tertiary collimator showers towards the ALICE cavern.
Paper: MOPS138
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-MOPS138
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
TUPB027
Improving the SPS beam extraction efficiency by implementation of a crystal septum
1021
The third-integer resonant extraction of the proton beam from the Super Proton Synchrotron (SPS) at CERN is a technique used for slow extraction of the circulating beam, providing a constant spill of protons to the North Area experiments. Currently, this method employs an electrostatic septum (ZS) to separate the extracted particles from the proton beam circulating in the ring. However, a fraction of the protons is lost on the mechanical parts of the ZS causing its activation, thus, limiting the efficiency of the process. In this work, the first considerations for solving this problem are presented with the implementation of a non-resonant slow extraction scheme that enables the extraction of the particles without the use of the ZS. The extraction efficiency and beam quality are benchmarked using the Xsuite particle tracking framework for a new configuration, which is compared with the present setup.
Paper: TUPB027
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB027
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
TUPB029
Simulations of beam halo distributions for a feasibility study of in-vacuum gravitational experiments at the LHC
1029
Within the realm of general relativity, the measurement of signals coming from relativistic celestial bodies have offered great insights. However, the relatively low frequency of these signals and the lack of control over their source may make the creation of well-controlled laboratory environments desirable. One possibility is to measure the relativistic beams in the Large Hadron Collider (LHC) at CERN using a milligram-scale monolithic pendulum. This would offer the possibility to test general relativity and alternative theories of gravity in an entirely new parameter regime, where the source of gravity is the almost pure kinetic energy of the ultra-relativistic particles. The low-bandwidth of the source, combined with the controllability of the setup, may offer new opportunities and insights in gravity-related research. To design the experiment, it is necessary to analyze the factors that contribute to the deterioration of the signal-to-noise ratio. One of the contributors is the impact on the pendulum of beam halo particles. This paper presents an initial assessment of the impact of beam halo on the detection of gravitational signal.
Paper: TUPB029
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB029
About: Received: 26 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
TUPB030
Characterisation of transverse proton beam losses at the CERN Super Proton Synchrotron
1033
The High-Luminosity LHC (HL-LHC) project foresees nearly doubling the design beam intensity of CERN's Large Hadron Collider (LHC). A particularly pressing issue is the observation of significant beam losses at the flat bottom in the Super Proton Synchrotron (SPS) that delivers these beams to the LHC. These losses arise from multiple factors: uncaptured beam losses that are generated during the bunch rotation in the Proton Synchrotron (PS) before the transfer to the SPS; large transient beam loading effects in the RF system during multi-turn SPS injections; and the diffusion of over-populated transverse tails, which reach aperture limitations. Dedicated beam measurements were carried out in the SPS as a first step towards untangling these losses. These studies aimed to disentangle the various loss mechanisms, with a focus on the halo population and potential correlations between transverse and off-momentum tails.
Paper: TUPB030
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB030
About: Received: 25 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
TUPB031
Overview of seven-unit collimator system and its operation for J-PARC main ring
1037
The J-PARC main ring has three linear sections, and one have a beam collimator system downstream of the injection devices to localise beam losses. In September 2024, the seventh collimator unit was installed, completing an upgrade of the collimator system that has been underway since 2012. The system was changed from one that scatters and captures the beam halo to one that draws the jaw close to the beam core and directly removes its halo. This allowed a number of collimator units to be placed in a limited area. The original beam loss capacity in the collimator area was 450 W. Seven collimator units allow a beam loss of 3.5 kW. Currently, six collimator units are used to deliver 800 kW beams to neutrino experiments with losses of less than 500 W. By using seven collimator units, a beam of 1.3 MW can be delivered with a reasonable loss amount. The combination of units effectively removes the halo component of the beam and localises the beam losses. However, the direct removal method can create loss spots downstream of the collimator according to phase advance. This paper describes the operation of collimators in actual beam operation.
Paper: TUPB031
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-TUPB031
About: Received: 29 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
WEPM001
High Luminosity LHC optics: Machine development results
1948
As the High Luminosity LHC (HL-LHC) era approaches, precise control of the accelerator becomes increasingly critical. Machine studies are essential to address the forthcoming challenges and develop correction strategies based on experimental measurements. Although the upgraded inner triplets are not yet available, key features of the HL-LHC optics can still be investigated. This includes exploring the high Achromatic Telescopic Squeeze (ATS) factors in the neighboring arcs of the high-luminosity interaction regions, particularly under flat optics configurations. A beta blow-up is also implemented in the long straight section containing most of the beam instrumentation to improve their sensitivity at top energy. This paper presents experimental measurements, evaluates arc phase errors, and discusses the implementation of local corrections. Sextupole bumps in the arcs were employed to mitigate these errors, demonstrating their effectiveness in optimizing machine performance.
Paper: WEPM001
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM001
About: Received: 27 May 2025 — Revised: 03 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
WEPM013
Impact of the inner triplet polarity on the optics commissioning of the LHC in 2024 and 2025
1976
To mitigate the risk of radiation damage induced failure while operating the LHC beyond its initial integrated luminosity target, changes to the triplet polarity and crossing angles have been applied in the two main experimental interaction regions of the LHC. This allows for a more distributed radiation deposition in the insertion region magnets, which should allow their survival until they are replaced as part of the High Luminosity LHC upgrade from 2026-2030. These changes in the optics during 2024 and 2025 came with important challenges regarding machine commissioning and optics correction. In this paper, we discuss our experience of linear optics correction for the various triplet polarity configurations and review the implications for nonlinear optics corrections.
Paper: WEPM013
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM013
About: Received: 26 May 2025 — Revised: 02 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
WEPM043
Impact of non-linearities on collimation losses at the CERN Large Hadron Collider
2065
Since the start of the third operational run of the CERN Large Hadron Collider (LHC) in 2022, multiple observations have highlighted the significant influence of non-linearities within the accelerator on the collimation loss patterns of circulating beams. Understanding this phenomenon is particularly relevant for qualifying and validating collimation performance for machine operation at high intensity. In this study, we explore the capability of advanced numerical simulations to reproduce the observed loss patterns, incorporating a detailed representation of various nonlinearities. These include strong octupole fields and high chromaticity. An in-depth analysis comparing the simulation results to experimental measurements was conducted. These findings provide valuable insights into the interplay between machine non-linearities and beam losses.
Paper: WEPM043
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM043
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
WEPM054
Beam loss simulations for space charge mitigation in J-PARC MR
2097
The main ring synchrotron (MR) of the Japan Proton Accelerator Research Complex (J-PARC) provides high power proton beams to neutrino and hadron experiments. Since we are planning to increase the beam intensity from current $2.3 \times 10^{14}~$protons per pulse (ppp) to $3.3 \times 10^{14}~$ppp, we need to reduce the beam loss. In the J-PARC MR, the space charge is one of the main causes of beam loss. As a first step, we developed a new beam optics suppressing the space-charge-induced resonance which is the primary cause of the beam loss. In this paper, we report details of the beam loss mechanism in J-PARC MR by comparing the tune scan results of the present and new beam optics.
Paper: WEPM054
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM054
About: Received: 31 May 2025 — Revised: 02 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
WEPM074
Impact of the geometric impedance of collimators on beam stability in FCC-ee
2137
Beam stability in the FCC-ee collider is strongly influenced by transverse and longitudinal beam coupling impedance. Developing a flexible and comprehensive impedance model is crucial for accurately evaluating and mitigating instabilities as machine parameters evolve. This study investigates the effect of the FCC-ee collimation system, identifying it as a dominant source of total machine impedance. Both resistive and geometric contributions are analyzed, with geometric effects found to play a critical role in shaping the overall impedance landscape. Accurately modeling collimators’ geometric impedance is essential for beam stability assessment. Such modeling enables global impedance considerations, accounting for the interplay between different accelerator elements and guiding the definition of critical design parameters.
Paper: WEPM074
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPM074
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
WEPS039
Progress & developments of beam delivery simulation (BDSIM)
2325
BDSIM (Beam Delivery Simulation) is a Monte Carlo particle tracking tool for accelerator beamline modelling. It integrates particle transport with detailed geometry and physics using Geant4 for precise modelling of particle-matter interactions in 3D models of particle accelerators. Primarily for energy deposition studies and beam loss simulations, BDSIM allows a high degree of control and customisation, and is ideal for understanding and enhancing the performance of beamline designs. BDSIM has numerous modelling applications, including high-energy physics facilities, particle detection experiments, synchrotron light sources, medical accelerators, and novel acceleration experiments. Here, we present recent developments of BDSIM. This includes improved custom inverse-Compton scattering processes for laserwire and polarimeter simulations and extending the process to model polarization & electron spin; improved acceleration including transverse focussing in RF elements with implementation of 3D transverse magnetic and electric modes; custom elements for modelling muon cooling channels; and updates to interfacing with Xsuite via improved code couplings and BDSIM distribution methods.
Paper: WEPS039
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS039
About: Received: 28 May 2025 — Revised: 01 Jun 2025 — Accepted: 02 Jun 2025 — Issue date: 05 Nov 2025
WEPS070
Analysis of coupled-bunch instabilities in Diamond-II
2388
The low-frequency components of the impedance drive coupled-bunch instabilities in electron synchrotrons. In the Diamond-II storage ring, the geometric component of the impedance of some vacuum vessels is comparable in strength to the resistive-wall impedance. This study compares the growth rates of all coupled-bunch modes obtained through simulations and analytical calculations. Self-consistent simulations, incorporating the harmonic cavity along with short-range wakefields and higher-order cavity modes, show that the beam can be stabilised with and without multi-bunch feedback by adjusting the chromaticity.
Paper: WEPS070
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS070
About: Received: 28 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
WEPS110
An updated HL-LHC halo population model based on recent experimental measurements
2435
The transverse beam halo population in the Large Hadron Collider (LHC) has been found to carry a significant fraction of the total stored beam energy, potentially reaching several percent. With the anticipated increase in beam brightness for the High Luminosity LHC (HL-LHC), this poses an increasing risk to machine safety, particularly during abrupt orbit shifts or critical component failures. A comprehensive understanding and an accurate modelling of the transverse beam halo are crucial for simulations of beam losses around the ring as a consequence of such failure scenarios in the HL-LHC era. Various models, including Gaussian, double-Gaussian, and q-Gaussian distributions, have been used to describe the LHC beam halos for fitting the measured distributions. This paper provides an in-depth analysis of halo modelling based on collimator scraping measurements from the LHC operational Run 2 and Run 3, and evaluates the accuracy and representativeness of these different distribution models.
Paper: WEPS110
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-WEPS110
About: Received: 27 May 2025 — Revised: 02 Jun 2025 — Accepted: 03 Jun 2025 — Issue date: 05 Nov 2025
THAN1
Assessing the origin of the LHC beam halo
2473
Measurements of the transverse beam-halo population at large amplitudes in the Large Hadron Collider (LHC) provide crucial insights into the stored beam energy near the LHC collimators. These particles do not contribute significantly to the luminosity but their loss could impose limitations on accelerator performance through sudden loss spikes or even collimator damage in case of fast beam failures. A thorough understanding of the beam halo formation, along with the physical mechanisms driving its behaviour and evolution throughout the final stage of the LHC injection chain and during the acceleration cycle, is essential to define appropriate mitigation strategies to ensure reliable operation in view of High Luminosity LHC beam parameters. In this study, we explore potential origins of the transverse beam halo by examining experimentally multiple contributing factors to halo formation, including electron cloud effects, beam injection dynamics from the Super Proton Synchrotron (SPS), and the energy ramping process within the LHC.
Paper: THAN1
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THAN1
About: Received: 27 May 2025 — Revised: 05 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025
THPB015
An evaluation of collimation settings for the High Luminosity LHC baseline
2532
In the context of the High Luminosity Large Hadron Collider (HL-LHC) project, two configurations of collimator settings are being considered. A set of relaxed settings were conceived to address potential limitations due to the impedance contribution of the collimation system with the initially foreseen settings, and to increase the primary betatron cut in case of over-populated beam tails. A significant simulation campaign has been conducted, utilising Xsuite-FLUKA coupling for the first time, to estimate the cleaning performance for each of these settings with the latest optics and layout scenarios. In addition, experiments in the current LHC have been carried out to experimentally study the cleaning performance with HL-LHC settings and to validate the simulated predictions. This paper presents and examines the results of these studies, aiming to determine which collimation settings are more suitable for implementation.
Paper: THPB015
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB015
About: Received: 28 May 2025 — Revised: 30 May 2025 — Accepted: 30 May 2025 — Issue date: 05 Nov 2025
THPB019
Lifecycles and workflows for 3D integration studies at CERN
2544
The implementation of a new product data management (PDM) and product lifecycle management (PLM) system at CERN has significantly improved lifecycles and workflows for 3D integration studies, thanks to the advanced features and tools of the platform. This new PDM/PLM system has provided an opportunity to reassess and optimize user methodologies, focusing on better organization of 3D CAD data, improved collaboration with mechanical and services design offices, and more effective validation processes. Additionally, enhanced traceability throughout workflows is expected to boost overall process quality. This paper examines the challenges encountered during the transition as well as the benefits of the new PDM/PLM, highlighting its contribution to increased efficiency and quality.
Paper: THPB019
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB019
About: Received: 27 May 2025 — Revised: 13 Oct 2025 — Accepted: 13 Oct 2025 — Issue date: 05 Nov 2025
THPB086
New analysis tools for LHC aperture measurements
2650
Aperture measurements at the Large Hadron Collider (LHC) are routine procedures conducted during the early stages of beam commissioning, prior to the injection of high-intensity beams. This is to ensure that the aperture, defining the clearance for the circulating beams, is protected by the LHC collimation system. Local aperture measurements are performed to probe the available aperture at specific locations. Such measurements are carried out by applying a local orbit bump in the area of interest. The bump amplitude is increased until the beam touches the aperture, visible through signals in the local Beam Loss Monitors. This contribution introduces a refined approach to analyse local aperture measurements by incorporating measured beam position monitor (BPM) signals to enhance the precision of the analysis. Using the Xsuite package, the orbit bump is simulated and rematched to the measured BPM signal to enhance the analysis and quantify the uncertainties with respect to the theoretical beam orbit. Using past measurement data, we compare the results obtained using the established and revised methodologies and conclude on derived measurement uncertainties.
Paper: THPB086
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB086
About: Received: 14 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
THPB099
Design overview of the medium energy beam transport line for the ANTHEM project
2680
The ANTHEM (Advanced Technologies for Human-centered Medicine) research project will establish a Research and Clinical Center in Caserta, Italy, for the study and application of Boron Neutron Capture Therapy (BNCT). The Radio-Frequency Quadrupole (RFQ), designed by INFN, produces proton beam of 30 mA at 5 MeV, impinging on a beryllium target. A 12 m long Medium Energy Beam Transport (MEBT) line, located after the RFQ, is responsible for transporting the beam to the target for optimal neutron production. This paper gives an overview of the design of MEBT line and details its main characteristics about beam dynamics, vacuum system and its mechanical layout.
Paper: THPB099
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPB099
About: Received: 25 May 2025 — Revised: 14 Oct 2025 — Accepted: 14 Oct 2025 — Issue date: 05 Nov 2025
THPM012
Optimizing collimator positions using bayesian optimization in the Fermilab MI-8 transfer line
2711
Collimators are used to minimize losses and to remove particles that would otherwise get lost downstream and irradiate the machine. Finding the optimal jaw positions is time consuming and with the upstream beam properties changing, the collimation settings would need to be readjusted each time. Therefore, a method to optimize collimator positions and to operate them at full capacity in a short time is required for loss control downstream. A study of collimator positions was conducted and a machine learning (ML) model was developed to predict optimal collimator positions. Bayesian Optimization (BO) was used to calculate new jaw positions from the ML model. The results of BO and usage of ML for better performance of the collimation system are presented in this paper.
Paper: THPM012
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM012
About: Received: 29 May 2025 — Revised: 01 Jun 2025 — Accepted: 01 Jun 2025 — Issue date: 05 Nov 2025
THPM089
Disentangling sudden beam loss events and fast beam abort system with the RFSoC-BPM at SuperKEKB
2870
In the SuperKEKB/Belle-II experiment, various new physics searches are conducted by colliding 4 GeV positrons and 7 GeV electrons. Future plans aim to significantly increase luminosity, targeting an integrated luminosity 100 times higher than current levels. However, the realization of this goal is challenged by the phenomenon of "Sudden Beam Loss" (SBL), characterized by the abrupt disappearance of the beam within tens of microseconds. As presented at IPAC'24, we developed the RFSoC-BOR (Bunch Oscillation Recorder) system, based on the AMD/Xilinx RF System on Chip (RFSoC). This system enables bunch-by-bunch beam position monitoring and detailed SBL data acquisition. Using the RFSoC-BOR, we analyzed SBL events, identified key contributing factors, and gained insight into strategies for mitigation. Our findings have advanced the understanding of SBL, bringing SuperKEKB closer to higher luminosity operation. Additionally, we are extending the functionality of the RFSoC-BOR to develop a fast beam abort system that improves accelerator component protection. This presentation will cover the role of the RFSoC-BOR in SBL analysis, key insights, and progress on the fast beam abort system.
Paper: THPM089
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPM089
About: Received: 27 May 2025 — Revised: 31 May 2025 — Accepted: 01 Jun 2025 — Issue date: 05 Nov 2025
THPS058
Cryogenic inserts in the room temperature synchrotron SIS18 at GSI
3094
The existing room temperature heavy ion synchrotron SIS18 at GSI will be used as booster for the future SIS100 at FAIR. One of its features the the generation of high intensity heavy ion beams. In order to create such beams, medium charge states are used, which have a lower space charge limit and can be created with less stripping losses. Unfortunately, such heavy ions have very high ionization cross sections in collisions with residual gas particles, yielding in beam loss and subsequent pressure rises via ion impact stimulated gas desorption. Although an extensive upgrade plan, including NEG-coated magnet chambers and an ion-catcher system, has been realized, the required intesity goals will not yet be reached. Simulations including cryogenic surfaces around the ion catchers show, that their high sticking probability prevents from pressure built-ups during operation. A prototype ion catcher, including such cryogenic surfaces cooled by a commercial cold-head has been developed, built, and tested. It has recently been installed in SIS18 and will undergo further tests, including measurements with heavy ion beams. Findings for the operation and further cryogenic inserts are presented.
Paper: THPS058
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS058
About: Received: 20 May 2025 — Revised: 30 May 2025 — Accepted: 31 May 2025 — Issue date: 05 Nov 2025
THPS078
Measuring single-pass dispersion in the LHC
3121
During the LHC Ion Run in 2023, the ALICE detector observed a high level of background that prevented efficient data taking. This background was caused by different ion species generated in the betatronic collimation region that were intercepted by the Tertiary collimator near ALICE Interaction Point. The mass-to-charge ratio of these generated ions causes them to follow a different trajectory to the main ion beam, similar to off momentum particles. Since this is a single-pass effect, the closed dispersion does not describe the trajectory of these ions. Instead, the single-pass or one-pass dispersion is the relevant quantity to measure. In this paper two methods for reconstructing the single-pass dispersion based on the closed orbit and optics data are described. The methods are validated through simulations and applied to real data from the LHC 2023 Ion Run.
Paper: THPS078
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS078
About: Received: 27 May 2025 — Revised: 04 Jun 2025 — Accepted: 04 Jun 2025 — Issue date: 05 Nov 2025
THPS084
LHC BLM-based beam loss pattern recognition algorithm for off-momentum losses
3137
The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) protects the accelerator against energy deposition from beam losses. One of the most critical moments regarding beam losses is the start of the beam acceleration. During this process, particles outside the bucket will not be captured in the first seconds of the start of ramp thus being lost at the machine aperture. This is expected to be the moment of minimum beam lifetime in the LHC cycle. During Run 3, losses from these off-momentum particles triggered some beam dumps. Several studies are on-going to assess a possible limitation from this loss scenario. This contribution quantifies the beam power lost at that moment and how the losses are distributed along the accelerator by the use of a dedicated BLM loss pattern recognition algorithm.
Paper: THPS084
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS084
About: Received: 28 May 2025 — Revised: 31 May 2025 — Accepted: 01 Jun 2025 — Issue date: 05 Nov 2025
THPS089
Measurements for beam size blowup in sudden beam loss events and analysis of the beam loss evolution mechanism
3144
The SuperKEKB electron-positron collider, which aims to achieve the world's highest luminosity, has suffered from "Sudden Beam Loss events (SBL)," in which several tens of percent of the beam current is lost and aborted within a few turns (20-30 µs). We have developed a new turn-by-turn beam size monitor to elucidate the cause and time evolution mechanism of the SBL events from a beam size variation point of view. The beam size monitor has two features: 1) it can measure the beam size variation over dozens of turns just before an SBL-induced beam aborts, and 2) it can measure independently in two different wavelength regions, X-ray and visible light, to ensure redundancy. In the SuperKEKB operation in 2024, we found that the vertical beam size blew up rapidly before a few turns of the abort, up to about ten times larger than the usual beam size. We also found that the size blowup started earlier than the beam position oscillation. In this presentation, we will discuss the mechanism of the beam size monitor we have developed, the analysis results of the measured beam size blowup, and finally, the possible cause and time evolution mechanism of the SBL events.
Paper: THPS089
DOI: reference for this paper: 10.18429/JACoW-IPAC2025-THPS089
About: Received: 28 May 2025 — Revised: 03 Jun 2025 — Accepted: 05 Jun 2025 — Issue date: 05 Nov 2025