The present ion physics program in the CERN accelerator complex is mainly based on Pb ion beams. The ALICE3 detector upgrade proposal at the Large Hadron Collider (LHC) requests significantly higher integrated nucleon-nucleon luminosity compared to the present Pb beams, which can potentially be achieved with lighter ion species. These lighter ion species have also been requested by the fixed-target experiment NA61/SHINE in the CERN North Area (NA). To assess the performance capabilities of the CERN Ion Injector chain (consisting of Linac3, LEIR, PS and SPS) for light ions, for which there is little or no operational experience at CERN, beam-brightness and intensity limitations need to be studied. This contribution presents tracking simulation results for the PS and SPS, compared against recent experimental beam data for Pb in the Ion Injectors. These simulations include limiting beam-dynamics effects such as space charge and intra-beam scattering, and their impact on the intensity and emittance evolution is discussed. These simulation models are used to predict the optimal ion species for maximum performance out of the Ion Injector Chain.

The luminosity of particle colliders depends, among other parameters, on the transverse profiles of the colliding beams. At the LHC at CERN, heavy-tailed transverse beam distributions are typically observed in routine operation. The luminosity is usually modelled with the assumption that the 𝑥-𝑦 planes are independent (i.e. statistically uncorrelated particle distributions between the planes) in each beam. Analytical calculations show that the solution of inverting 1D heavy-tailed beam profiles to transverse 4D phase-space distributions is not unique. For a given transverse beam profile, the distributions can be dependent (i.e. statistically correlated) or independent in the transverse planes, even in the absence of machine coupling. In this work, the effect of transverse 𝑥-𝑦 dependence of the 4D phase space distribution on the luminosity of a particle collider is evaluated for heavy-tailed beams.

The beam transverse emittances play a critical role in high-energy colliders. Various measurement techniques are employed to measure them. In particular, the so-called luminosity emittance scans (or Van der Meer scans) are used in order to evaluate the convoluted beam emittances. This method assumes different emittances in the two planes but identical emittances in the two beams. In this paper, we propose an approach to remove this constraint. After having presented the new measurement protocol, we will discuss its potential and limits, including the statistical measurement error of the luminosity value as obtained from numerical studies.

In 2023, about 2 months of the LHC operation were devoted to the Heavy Ions physics, after more than 5 years since the last ion run. In this paper, the results of the 2023 Ion optics commissioning are reported. Local corrections in Interaction Point (IP) 1 and 5 were reused from the regular proton commissioning, but the optics measurement showed the need for new local corrections in IP2. We observed that an energy trim of the level of 10e-4 helped to reduce the optics errors at top energy. The dedicated measurements during the energy ramp revealed a larger than expected beta-beat, which is consistent with an energy mismatch. Furthermore, global corrections were performed to reach a β-beating of about 5% for the collision optics.

Using a simplified multi spin resonances model we study the how the interference of spin resonances near a strong intrinsic spin resonance crossing effect the polarization transmission as a function of emittance for a lattice with more than two snakes.

The 2016 Relativistic Heavy Ion Collider (RHIC) Au-Au run took place from January 25 to June 27, 2016. Four so-called vernier scans were performed at 100 GeV per beam, with γ=107.396 at flattop at one of the interaction points, IP6. During this type of procedure, one beam is swept across the other, first horizontally and then vertically, recording the interaction rate as a function of the beam to beam separation. From that data, the effective cross section of the Zero Degree Calorimeter (ZDC) can be derived. This paper discusses the results of the scans, as well as the systematic uncertainties of the derived effective cross section.

The Relativistic Heavy Ion Collider (RHIC) was designed for head-on collisions in the Interaction Regions. However, RHIC operation in recent years necessitated crossing angles to limit collisions to a narrow longitudinal vertex region, which created operating conditions with a large Piwinski angle (LPA). The angles were implemented by adjusting the shunt currents of four dipoles, the D0 and DX magnets, near the IP. The longitudinal bunch profile often deviates from Gaussian due to the utilization of high-order RF cavities, adding complexity to calculating luminosity reduction with crossing angle. This paper introduces two methods for implementing crossing angles, discusses resultant aperture concerns, conducts numerical calculations of luminosity reduction, and compares these findings with experimental observations.

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

For the 2024 100 GeV proton run at RHIC, the new sPHENIX detector will require a maximum amount of collisions within ±10 cm of its central Interaction Point (IP), and preferably few or no collisions outside this range. To maximize the collisions within the vertex, a large crossing angle of up to 2 mrad will be used, operating the Large Piwinski Angle (LPA) scheme. To compensate for the reduction in luminosity from the large Piwinski angle, a β=50 cm lattice has been designed and supported with dynamic aperture simulations. To further compensate the luminosity reduction, injector studies have been performed to support up to a 45% increase in the injected intensity relative to the previous 100 GeV run in 2015.1

The Relativistic Heavy Ion Collider (RHIC) Run 23 program consisted of collisions of 100 GeV gold beams at two collision points for the first time since 2016; the sPHENIX collaboration used the beam to commission their new detector systems while STAR took physics data. Completion of sPHENIX construction pushed the start of the run to May, forcing the collider complex to operate over the summer months and incurring lower than normal availability due to heat and power dip related problems. Issues with dynamic pressure rise during acceleration through transition resulted in a slower ramp up of intensity compared to prior years. Finally, a failure of a warm-to-cold current lead interface in the valve box for the Main Magnet power supply forced the run to end. This paper will discuss the progress made by each experiment and the failure mode, repair and mitigation efforts in preparation for Run 24.

The present ion physics program in the CERN accelerator complex is mainly based on lead (Pb82+) ion beams. Lighter ions have been considered both by the ALICE3 detector upgrade proposal at the Large Hadron Collider (LHC) --- as a potential way to achieve higher integrated nucleon-nucleon luminosity compared to the present Pb beams --- and also by the Super Proton Synchrotron (SPS) fixed-target experiment NA61/SHINE. However, there is little or no operational experience at CERN with ions species lighter than Pb. This calls for beam-brightness and intensity limitations studies to assess the performance capabilities of the CERN ion injector chain, which consists of LINAC3, the Low-Energy Ion Ring (LEIR), the Proton Synchrotron (PS) and the SPS. This paper presents tracking simulation resu lts for the SPS, compared against recent Pb beam emittance and beam loss measurements at the long injection plateau. The simulation models include limiting beam dynamics effects such as space charge and intra-beam scattering (IBS), whose impact on the future ion injector chain performance is discussed. Beam dynamics simulation results for the planned O8+ pilot physics run are also presented.

The luminosity of particle colliders depends, among other parameters, on the transverse profiles of the colliding beams. At the LHC at CERN, heavy-tailed transverse beam distributions are typically observed in routine operation. The luminosity is usually modelled with the assumption that the 𝑥-𝑦 planes are independent (i.e. statistically uncorrelated particle distributions between the planes) in each beam. Analytical calculations show that the solution of inverting 1D heavy-tailed beam profiles to transverse 4D phase-space distributions is not unique. For a given transverse beam profile, the distributions can be dependent (i.e. statistically correlated) or independent in the transverse planes, even in the absence of machine coupling. In this work, the effect of transverse 𝑥-𝑦 dependence of the 4D phase space distribution on the luminosity of a particle collider is evaluated for heavy-tailed beams.

Since the start of the Large Hadron Collider (LHC), dust-induced beam loss events resulted in more than hundred premature beam aborts and more than ten dipole quenches during proton physics operation. The events are presumably caused by micrometer-sized dust grains, which are attracted by the proton beams and consequently give rise to beam losses due to inelastic proton-nucleus collisions. Besides the events which trigger dumps or quenches, a large number of smaller dust events has been detected by the beam loss monitors every year. Although these events are not detrimental for physics operation, they are still carefully scrutinized as they give a better understanding about the correlation with beam parameters, about the long-term evolution of event rates, and about possible correlations with shutdown activities and the installation of new equipment. In this contribution, we present a summary of observations from the first three runs of the LHC.

Power limitations are expected at injection energy for the main Radio Frequency (RF) system due to the doubled bunch intensity in the High Luminosity (HL-) Large Hadron Collider (LHC) era. One way to overcome these power limitations is to reduce the capture voltage. The smaller RF bucket, however, leads to increased beam losses at the start of the ramp. In practice, these beam losses, which contain both capture and flat-bottom losses, can trigger beam dumps if any of the Beam Loss Monitor (BLM) thresholds are reached. In this contribution, the correlation between start-of-ramp beam loss and beam observables before the ramp is investigated by analysing Beam Current Transformer (BCT) measurements from physics fills. Estimates of how the maximum ratio to BLM dump threshold scales with longitudinal losses are also made. The aim is to make predictions for operation at higher bunch intensities on the basis of these correlations in view of the intensity ramp up for the HL-LHC era.

The LHC machine configuration was changed in 2023 compared to previous years, requiring a new set of optics configurations to be measured and corrected. A telescopic optics was deployed in energy the ramp for the first time, which gave rise to a beta-beating of up to 25%. This was corrected using a global correction approach which reduced the beta-beat down to 10%. A change in the phase advance at injection was also applied to mitigate the negative effect of the main octupoles used to stabilize the beam. These measurements and corrections, coupled with the results from the 2024 commissioning, will be presented in this paper

During 2023, examination of the action dependence of sextupolar resonance driving terms (RDT) in the LHC at injection, as measured with an AC-dipole, demonstrated that a robust measurement of the RDTs could still be achieved even with very small amplitude kicks, typically used for linear optics studies. Consequently, analysis of optics measurements from 2022 and 2023 during the LHC energy ramp allowed a first measurement of the sextupole resonance evolution. A large asymmetry was observed between the two LHC beams, with the clockwise circulating beam (LHCB1) significantly worse than the counter-clockwise circulating beam (LHCB2), and a clear increase in the RDT strength during the ramp was observed. Results are presented and compared to MAD-X simulations, in this report.

The Future Circular Collider (FCC) study includes two accelerators, a high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh). Both machines share the same tunnel infrastructure. We present the current design status of FCC-hh, highlighting the most recent changes, including a new layout following updated tunnel dimensions, a change from 12 to 16 dipoles per cell increasing the dipole filling factor, implementation of the beam crossing scheme at experimental interaction points, and the optical solutions found for the eight experimental and technical insertions.

A new layout for the energy-frontier hadron collider (FCC-hh) under study at CERN has been designed, following the constraints imposed by the outcome of recent tunnel placement studies. The new lattice and the need to maximize the dipole filling factor triggered a deep revision of the corrector systems located in the regular arcs, such as orbit, tune, linear coupling, and chromaticity correctors. The system of octupoles aimed at providing Landau damping has also been reviewed. Furthermore, the corrector package in the experimental insertion aimed at compensating the field quality of the triplet quadrupoles has been reconsidered in view of the experience gained with the design of the corresponding system developed for the CERN HL-LHC. In this paper, an account of this review is presented and discussed in detail. These estimates will need confirmation when the magnet design of the various correctors will be studied.

The Large Hadron Collider (LHC) employs special optics and configurations, alongside low-beta* collision optics, to address specific experimental requirements. These include calibrating luminosity monitors (vdM) and facilitating forward physics measurements in TOTEM and ALFA experiments (high-beta). The special optics have been in use since Run 1, and for Run 3, they have been updated for compatibility with standard low-beta collision optics to ensure streamlined commissioning and reduced setup time. For vdM optics in Run 3, beam de-squeezing yields beta* values of 19 to 24 m, while in the high-beta optics, beams are de-squeezed to round beams with beta* of 120 m, followed by a second step to asymmetric optics with beta* of 3 km and 6 km in the horizontal and vertical planes. The 2023 high-beta optics run with the km beta* optics, incorporates tight collimation settings and the use of crystals at top energy for the first time, aiming to substantially reduce backgrounds in the experiments. This publication introduces and discusses the updated optics for Run 3, covering their validation, optics measurement results, and operational insights.

In 2023 the LHC restarted after the yearly winter shutdown with a new machine configuration optimized for intensities of up to 1.8e+11 protons per bunch. In the first two months of the 2023 run the bunch intensities were pushed up to 1.6e+11 protons per bunch until a severe vacuum degradation, caused by a damaged RF bridge, occurred close to the ATLAS experiment. Following repair, the decision was taken to stop the intensity increase. After a period of smooth operation, a leak developed between the cold mass and insulation vacuum of a low-beta quadrupole, leading to an abrupt stop of the LHC. Thanks to a rapid intervention, the leak could be repaired without warning up large parts of the machine, and the LHC was ready for beam again early September. Special runs at very large beta* were completed in the remaining time before switching to Lead ion operation. The performance achievements and limitations as well as the issues that were encountered over the year will be discussed in this paper.

In the High Luminosity Large Hadron Collider (HL-LHC) era, the intensity of the circulating bunches will increase to 2.2e+11 protons per bunch, almost twice the nominal LHC value. Besides detailed studies of known and new failure cases for HL-LHC, it is also required to investigate failures beyond nominal design. A consequence of such failures can be the impact of a large number of high-energy particles in one location, resulting in a significantly increased dam- age range due to an effect called hydrodynamic tunnelling. This phenomenon is studied by coupling FLUKA, an energy deposition code, and Autodyn, a hydrodynamic code. This paper presents the simulated evolution of the deposited energy, density, temperature and pressure for the impact of the HL-LHC beam on a graphite target. It then computes the resulting tunnelling range and finally compares the outcome with previous studies using LHC intensities.

The beam transverse emittances play a critical role in high-energy colliders. Various measurement techniques are employed to measure them. In particular, the so-called luminosity emittance scans (or Van der Meer scans) are used in order to evaluate the convoluted beam emittances. This method assumes different emittances in the two planes but identical emittances in the two beams. In this paper, we propose an approach to remove this constraint. After having presented the new measurement protocol, we will discuss its potential and limits, including the statistical measurement error of the luminosity value as obtained from numerical studies.

In 2023, about 2 months of the LHC operation were devoted to the Heavy Ions physics, after more than 5 years since the last ion run. In this paper, the results of the 2023 Ion optics commissioning are reported. Local corrections in Interaction Point (IP) 1 and 5 were reused from the regular proton commissioning, but the optics measurement showed the need for new local corrections in IP2. We observed that an energy trim of the level of 10e-4 helped to reduce the optics errors at top energy. The dedicated measurements during the energy ramp revealed a larger than expected beta-beat, which is consistent with an energy mismatch. Furthermore, global corrections were performed to reach a β-beating of about 5% for the collision optics.

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) is the world's largest and most powerful particle accelerator, colliding beams of protons and lead ions at energies up to 7 ZTeV. ALICE is one of the detector experiments optimized for heavy-ion collisions. A fixed-target experiment in ALICE is considered to collide a portion of the beam halo, split using a bent crystal, with an internal target placed a few meters upstream of the detector. For proton beams, we have already demonstrated that such a setup provides satisfactory performance in terms of particle flux on target and that it can be safely operated in parallel to regular beam-beam collisions. On the other hand, in the case of lead ion beams, a beam halo is populated with nuclei of many species that may differ in charge, mass and magnetic rigidity, making such a scenario more challenging to operate. This paper summarizes our first considerations of the feasibility of a fixed-target layout at ALICE to be operated with lead ion beams in the LHC.

In 2023, the Pb-Pb run in the Large Hadron Collider (LHC) took place during the last five weeks of operation at a record beam energy of 6.8 Z TeV. It marked the first heavy-ion run of Run 3, following a two-day test that took place in 2022 to verify some key machine and beam upgrades. The 2023 run profited for the first time of higher beam intensities than the previous runs and of machine upgrades that enable higher peak luminosities in the ion-dedicated ALICE experiment. This paper addresses two important performance aspects: firstly, it compares the achieved operational efficiency for the different filling schemes employed during the run, and secondly, it quantifies the main factors contributing to performance loss.