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Following new findings in beam dynamics and the latest HL-LHC project decisions, an operational scenario has been developed for the first HL-LHC run, Run 4. This new scenario is presented in this document along with the motivations for the proposed changes and performance estimates.

The Gamma Factory (GF) initiative proposes an innovative method of producing high-energy, high-intensity photon beams via the laser-excitation and subsequent decay of relativistic partially stripped ions stored in the CERN LHC. An initial proof-of-principle experiment in the CERN SPS (GF-SPS-PoP) was proposed in 2019 [3] and would demonstrate the key concepts of this method. Such an experiment would require good control and stability of the SPS beam position and momentum, this was investigated during Machine Development (MD) study 5044. The SPS beam stability at the proposed GF interaction point (IP) location was measured over the millisecond-to-second time-scale. To demonstrate control over the position and angle of the beam at the IP, four-corrector orbit bumps were implemented. The use of radial steering for varying the revolution frequency and, thus, the orbit radius was tested. Here we present the results from these studies towards demonstrating that the stability and control achievable in the CERN SPS would be suitable for the GF Proof-of-Principle experiment.

The CERN ion injectors, SPS and LEIR, operate in a strong space charge and intra-beam scattering regime, which can lead to degradation of their beam performance. To optimize machine performance requires thus to study the interplay of these two effects in combined space charge and intrabeam scattering tracking simulations. In this respect, the kinetic theory approach of intra-beam scattering has been implemented in pyORBIT and benchmarked against analytical models. First results of combined space charge and intra-beam scattering simulations for SPS and LEIR are presented in this contribution. The simulation results are compared with observations from beam measurements., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Innovative new magnets with longitudinally varying dipole field are being produced for installation in a few modern light-source storage rings. We investigate some of the associated beam-dynamics issues, in particular the photon spectrum and quantum fluctuation associated with such magnets, and we study whether the resulting equilibrium emittance may deviate from the value expected in the long-magnet limit., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

ELETTRA is a 2/2.4 GeV third-generation electron storage ring, located near Trieste, Italy. In view of a substantial increase of the machine performance in terms of brilliance, the so-called ELETTRA 2.0 upgrade is currently on-going. This upgrade is based on a 6-bends achromat, four dipoles of which having a longitudinally variable field. So far, those dipoles are foreseen to provide a field with a two step profile. The VAriable Dipole for the ELETTRA Ring (VADER) task, driven by the I.FAST European project, aims at developing a new dipole design based on a trapezoidal shape of the bending radius, which would allow for a further reduction of the horizontal emittance. A prototype of this magnet should be designed by the CIEMAT laboratory and built by KYMA company. This paper discusses the new dipole field specification and describes the corresponding optics optimization that was performed in order to reduce at best the emittance of the ELETTRA ring., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Harmonics of the mains frequency (50 Hz) have been systematically observed in the form of dipolar excitations in the transverse beam spectrum of the Large Hadron Collider (LHC) since the beginning of its operation. The power supply ripple, consisting of both fundamental and higher frequency components, is proven not to be the result of an artifact of the instrumentation systems with which they are observed. Potential sources of the perturbation have been identified through systematic analysis and experimental studies. Single-particle tracking simulations have been performed including a realistic power supply ripple spectrum, as acquired from experimental observations, to demonstrate the impact of such noise effects on beam performance., Proceedings of the 64\textsuperscript{th} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2021, Batavia, IL, USA

Crab Cavities are a key component of the High Luminosity LHC (HL-LHC) upgrade, as they aim to minimize the luminosity reduction caused by the crossing angle. Two superconducting crab cavities were installed in the Super Proton Synchrotron (SPS) at CERN in 2018 to test their operation in a proton machine for the first time. An important point to consider is the increase in transverse emittance induced by noise in the Low-Level RF (LLRF) system. During the first experimental campaign in 2018, the measured emittance growth was found to be a factor of 4 lower than predicted by the available analytical models. In this report, the effects of transverse beam impedance in the presence of CC LLRF noise on transverse emittance growth are presented and the results of the second experimental campaign, which took place in the SPS in 2021, are discussed., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

A new scenario for the first operational run of the HL-LHC era (Run 4) has been recently developed to accommodate a period of performance ramp-up to achieve an annual integrated luminosity close to the nominal HL-LHC design. The operational scenario in terms of beam parameters and machine settings, as well as the different phases, are described here along with the impact of potential delays on key hardware components., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

After its second successful run period, the Large Hadron Collider (LHC) shut down for three years with the plan of being recommissioned in 2022 for a three-year physics production period, the Run 3. The future restart of the machine coincides with the completion of the LHC Injectors Upgrade (LIU) project, offering to the LHC the opportunity and the challenge to operate with up to two times higher beam brightness, pending the complete installation of the High-Luminosity LHC (HL-LHC), which should take place in Long Shutdown 3 (LS3). In this context, Run 3 is clearly a transition between the LHC and the HL-LHC, with key ingredients which will be made available, either gradually (LIU beam) or immediately (ATS optics). Run 3 shall therefore be exploited not only for performance, but also as a full scale demonstrator of the HL-LHC in terms of beams, optics and beam manipulation (e.g. β∗ levelling over a very large dynamic range). To this aim, the so-called LHC configuration, namely the optics, needs to be adapted in order to cope or mitigate constraints of different nature, from beam brightness limitations due to the machine impedance, to specific desiderata of some LHC experiments. After reviewing these constraints, including the intensity limitations coming from the existing hardware, the beam parameters targeted for the LHC in Run 3 are given. A possible solution for the machine configuration will then be described, and analyzed from various perspectives, which should not limit the machine performance over the full Run 3, and should enable to double the integrated luminosity delivered so far to the two high luminosity insertions of the LHC.

After the successful experiments performed during the LHC Run 2 with the Beam-Beam Wire demonstrators installed, on Beam 2, in the frame of the HL-LHC project, two of the four wire demonstrators were moved to Beam 1. The objective is to gain operational experience with the wire compensation also on that beam and therefore fully exploit the demonstrators’ potential. This paper proposes a numerical validation of the wire implementation using Run 3 scenarios and explores the optimization of those devices in that respect., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The FCC-e⁺e⁻ injector complex needs to produce and to transport high-intensity e⁺ and e⁻ beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS)., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The LHC is designed to collide intense bunches of protons with tightly defined conditions, aimed to maximize the delivered recorded integrated luminosity to the experiments. One of these conditions is the maximum level of bunch-to-bunch fluctuation in the luminosity, in particular when levelling at maximum acceptable event rate at the experiments. Analysis results of the bunch-to-bunch luminosity variations in LHC Run 2 are presented here. In particular, the observed correlations with the LHC filling pattern that can enhance the effects introducing bunch-dependent losses or emittance blow-up from injection to collisions are discussed. In Run 2 conditions, bunch-by-bunch luminosity fluctuations reached 10% at the start of collisions and gradually increased with time, without affecting the experiments as the luminosity was not levelled. Projections for Run 3 and HL-LHC operation are discussed along with envisaged mitigation measures., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Crab cavities will be installed at the two main interaction points (IP1 and IP5) of the High Luminosity LHC (HL-LHC) in order to minimize the geometric reduction of the luminosity due to the crossing angle. Two prototype crab cavities have been installed into the SPS machine and were tested with a proton beam in 2018, to study the expected emittance growth induced by RF noise. The measured emittance growth was found to be a factor 2-3 lower than predicted from the available analytical and computational models. Damping mechanisms from the transverse impedance, which is not included in the available theories, are studied as a possible explanation for the observed discrepancy., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The objective of this research is to study the interplay of synchrotron radiation, intra-beam scattering, and space charge in the vicinity of excited resonances. In this respect, two modules were developed to simulate intra-beam scattering and synchrotron radiation effects and plugged into pyORBIT to be used together with its space charge module. Different regimes of synchrotron motion were used to study the response of the beam to a lattice resonance when space charge, intra-beam scattering and synchrotron radiation are present., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

During the last physics run of the Large Hadron Collider (LHC), Dynamic Aperture (DA) studies have been successfully employed to optimize the accelerator’s performance by guiding the selection of the beam and machine parameters. In this paper, we present a framework for single-particle tracking simulations aiming to refine the envisaged operational scenario of the future LHC upgrade, the High-Luminosity LHC (HL-LHC), including strong non-linear fields such as beam-beam interactions. The impact of several parameters and beam processes during the cycle is initially illustrated with frequency maps and then quantified with DA studies., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The main aspects linked to Landau damping of head-tail instabilities at top energy in the HL-LHC are discussed, in particular the interplay between the arc octupoles and long-range, offset or head-on beam-beam interactions as well as lattice imperfections. When possible, the models are compared with the operational experience of Runs 1 and 2 of the LHC. Based on these considerations, various operational scenarios are discussed identifying their strengths and limitations.

This note gives the steps to be followed in order to include the crab cavities module in MAD-X for tracking simulations in SixTrack. Examples of checks that aim to verify that the system is implemented as expected are provided; these checks are important to be done before launching large simulations using, for example, SixDesk.

The crab cavities to be installed in the High-Luminosity LHC (HL-LHC) aim to provide an increase in luminosity by restoring head-on collisions and therefore reducing the loss of luminosity due to the crossing angle. The crab cavities rotate the beam by providing z-dependent kicks near the interaction point. Two designs have been cast for this task: the RF dipole (RFD) and the Double Quarter Wave (DQW); a prototype of the latter one has been installed in the SPS and in 2018 the first successful crabbing of proton beams was achieved. As the design of both these crab cavities has to be very compact to be able to fit between the two beams, this causes a loss of axial symmetry that gives rise to high order multipoles. This study aims to explore the impact and tolerances of the high order multipoles on beam dynamics by performing DA studies on the HL-LHC lattice.

Following the success of the previous Space Charge Workshop at CERN in 2013, in Oxford in 2015 and in Darmstadt in 2017, CERN has hosted the 4th workshop in this series from the 4th - 6th November 2019, and it has been held under the auspices of ICFA, LIU and ARIES.

The High Luminosity LHC will have the challenge to operate in a high brightness regime. In these conditions, the intensity dependent collective effects dominate the operation and can significantly degrade the quality of the circulating beams. long-term single particle stability is crucial for defining the operational configurations, as it is directly correlated to beam lifetime. In this paper, the proton physics performance of the High Luminosity Large Hadron Collider is studied in terms its Dynamic Aperture in the presence of machine imperfections and including highly non-linear beam-beam interactions. For both the injection and top energy plateaus, several configurations are explored to further increase the beam lifetime thus refining the operational scenario at collisions. This assumes operation close the beam-beam limit in order to improve the pile-up conditions at the experimental detector insertions. The integrated performance of the baseline and proposed scenarios are also assessed. Furthermore, possible future upgrades such as the pact of delivering high luminosity to the Phase-II upgraded LHCb experiment well as the use of achromatic telescopic optics for mitigating the coherent stability bottleneck of the cycle are addressed and a set of optimal settings introduced.

A recurrent issue of the LHC operation, observed both during Run1 and Run2 is the asymmetric behaviour of the two beams in terms of particle losses. The fact that Beam 1 shows higher losses when compared to Beam 2 is not intuitive, especially when compared to the symmetric design of the two rings. The beam-beam effects induced by the interaction of the two beams in the experimental inserts, as well as noise sources contribute to the degradation of the beam lifetime,possibly asymmetrically between the two beams. In this Machine Development study, several machine and beam configurations are considered to identify or discard some of the possible sources of this behaviour. The impact of the active filters of the main bends in the beam spectrum is tested at injection energy as a possible source of 50 Hz harmonics. A variation in the beam-beam separation induced by a crossing angle bias, and the impact of the optics choice of different phase advances between the two high-luminosity interaction points are scrutinized as source of lifetime asymmetry. Finally, the wire beam-beam compensator is tested for the first time with full beam in a suboptimal configuration and its impact is assessed.

The Crab Cavities (CCs) may induce emittance growth, driven by phase and amplitude jitter, and lead to a degradation of the High Luminosity LHC (HL-LHC) beam. Furthermore, the tight HL-LHC space constraints call for non-axially symmetric cavity designs that come with higher order non-linearities which can affect the long-term dynamic aperture (DA). In order to study the effect the CCs have on the beam and the engineering challenges to validate the pre-series design, a prototype HL-LHC CC set was installed in the SPS machine in the year-end technical stop (YETS) of 2017-2018, and the first ever CC tests with protons were performed in 2018. This note is a collection of the reports and work done on the emittance growth measurements prior and after the CC installation, as well as simulations and measurements performed to study the CC and SPS non linearities effect. Finally, a summary of the instrumentation observations of the SPS CC experimental measurements is presented.

Over the course of 2018, 7 machine developments were conducted for dedicated crab cavity measurements with each measurement slot consisting of 10 hours of SPS machine time. During this period,many different sets of measurements and studies were performed to improve the understanding of the interaction between protons and crab cavities. This note describes the main results relating to beam dynamics. Additionally, the considerations on crab cavity related instrumentation required for HL-LHC are presented.

Since the beginning of the LHC commissioning, harmonics of 50 Hz have been observed in the beam spectrum. Several observations during the 2018 proton run show that these harmonics are the result of a real beam excitation, rather than an artifact of the instrumentation system. As many of these components reside in the vicinity of the betatron tune, their presence can complicate the tune measurement and tracking during operation and potentially lead to beam losses and emittance growth. This note summarizes the program of the first LHC Machine Development (MD) (Fills 7342 and 7343) dedicated to the investigation of this effect. The aim of this study is to reproduce some of the observations acquired during End-of-Fill experiments and parasitic observations, as well as to simulate the impact of dipolar noise on the beam with controlled ADT excitations.

This note summarizes the experimental results obtained during the 2018 LHC Machine Development program during the measurements campaign of the Beam-Beam Long-Range compensation using DC wires (MD3263). After the promising results obtained with the prototypes installed in IR5 in 2017, two new ones have been installed in IR1 during the EYETS 2017-18. They were commissioned with beam during the two first blocks of 2018 MDs (MD#1 and MD#2). More complex configurations were tested in the second part of the year: (i) compensation while reducing the crossing angle (MD#3) and (ii) compensation with trains in a configuration compatible with operation (MD#4).

his note summarizes the program of the LHC Machine Development to assess the potential and limits of the long-range beam-beam compensators held in 2017 (MD2202). Two compensator prototypes were installed in the machine during the EYETS16-17 and the first evidence of compensation were observed during the MD block 1 (FILLS 5898 and 5900, 9 h assigned on 1st July 2017).This study was also scheduled for the MD block 3 but could not be performed due to the machine unavailability (9 h assigned, 2 h available but unfortunately not exploitable for measurements). In MD block 4 an additional slot was scheduled (FILLS 6434 and 6435, 10 h on 29th November 2017)

The compensation of the long-range beam-beam interactions using DC wires is presently under study as an option for enhancing the machine performance in the frame of the High-Luminosity LHC project (HL-LHC). The original idea dates back more than 15 years. After the installation of four wire prototypes in the LHC in 2018, a successful experimental campaign was performed during the last months. The experimental setup and the main results are reported in this paper., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

We report the design of the pre-injector chain for the Future Circular e⁺ e⁻ Collider (FCC-ee) system. The electron beam from a low-emittance RF gun is accelerated by an S-band linac up to 6 GeV. A damping ring at 1.54 GeV is required for emittance cooling of the positron beam. The intermediate energy step from the exit of the S-band linac at 6 GeV to the 20 GeV injection energy of the top-up booster can be provided by the modified Super Proton Synchrotron (SPS), serving as a pre-booster ring (PBR). An alternative option to reach 20 GeV energy would be to extend the S-band linac with a C- or X-band linac. An overall cost optimisation will determine the choice of the final configuration. Beam loss and emittance dilution in the linac due to space charge effects, wakefields, and misalignment of accelerator components can be mitigated by RF phasing and orbit steering. Start-to-end simulations examine the beam transport through the linac up to either 6 GeV or 20 GeV. The results indicate large design margins. Simulations of the beam dynamics in the damping ring (DR) demonstrate a sufficiently large momentum acceptance. Effects of intrabeam scattering and electron cloud instability in the DR are also studied., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The FCC-ee is a high-luminosity, high-precision circular collider to be constructed in a new 100 km tunnel in the Geneva area. The physics case is well established and the FCC-ee operation is foreseen at 91 GeV (Z-pole), 160 GeV (W pair production threshold), 240 GeV (Higgs resonance) and 365 GeV (t-tbar threshold). Due to the large 6D production emittance and important thermal load in the production target, the positron injector, in particular the positron source, is one of the key elements of the FCC-ee, requiring special attention. To ensure high reliability of the positron source, conventional and hybrid targets are currently under study. The final choice of the positron target will be made based on the estimated performances. In this framework, we present a preliminary design of the FCC-ee positron source, with detailed simulation studies of positron production, capture and primary acceleration., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

This report discusses the feasibility and limitations for operating the LHC and HL-LHC at the ultimate beam energy of 7.5 TeV, corresponding to a main dipole magnetic field of 8.93 T and an operating current of 12748 A.

This report contains the description of a novel research infrastructure based on a highest-luminosity energy frontier electron-positron collider (FCC-ee) to address the open questions of modern physics. It will be a general precision instrument for the continued in-depth exploration of nature at the smallest scales, optimised to study with high precision the Z, W, Higgs and top particles, with samples of 5·10^12 Z bosons, 10^8 W pairs, 10^6 Higgs bosons and 10^6 top quark pairs. FCC-ee offers unprecedented sensitivity to signs of new physics, appearing in the form of small deviations from the Standard Model, of forbidden decay processes or of production of new particles with very small couplings. This collider will be implemented in stages, successively spanning the entire energy range from the Z pole over the WW threshold and H production peak to the tt ̅threshold. Most of the infrastructure (e.g. underground structures, surface sites, electrical distribution, cooling & ventilation, RF systems) can be directly reused for a subsequent energy-frontier hadron collider (FCC-hh, see FCC conceptual design report volume 3), serving the world-wide particle-physics community in a highly synergetic and cost-effective manner throughout the 21st century.