Conveners
FCC-ee accelerator: Baseline optics
- Ilya Agapov (Deutsches Elektronen-Synchrotron (DE))
FCC-ee accelerator: Alternative optics
- Angeles Faus-Golfe (IJClab IN2P3 CNRS-Université Paris-Saclay (FR))
FCC-ee accelerator: Tuning and Operations
- Rogelio Tomas Garcia (CERN)
FCC-ee accelerator: Collective Effects
- Lenny Rivkin (Paul Scherrer Institute (CH))
The collider beam optics (GHC) has been updated since FCC Week 2024 including several changes: longer $L^*$, smaller $\beta_x^*$ (Z), higher horizontal chromaticity (Z), longer space for the RF (Zh/$t\overline t$), wider beam separation in the technical straight, installation of vertical depolarization bump (Z/W), etc. The resulting luminosity and beam lifetime basically kept unchanged.
To maintain high circulating bunch charge despite the short beam lifetime and to maximize integrated luminosity, the FCC-ee requires top-up injection at all operation modes. The feasibility and efficiency of this scheme are therefore critical to the success of the FCC-ee program. Accurate simulation of the top-up injection process is essential and must account for collective effects and...
This talk gives an overview on the FCC-ee studies enabled by the development of the Xsuite beam-beam model. A summary of ongoing projects and a review of the computational needs and challenges are presented.
The Future Circular electron-positron Collider (FCC-ee) is being designed to explore physics beyond the present energy and luminosity frontiers for leptons. To achieve this goal, the FCC-ee must be capable of storing and colliding very high-intensity lepton beams. Handling such intensities poses unique challenges, including the need to safely manage stored beam energies of up to 17.5 MJ. A...
Two families of optics, GHC and LCC, are being developed for the FCC-ee collider; they are based on different designs, involving different requirements, sensitivities to errors and tuning strategies, which have an impact on hardware specification and procurement and operation. Comparing these two designs implies a multi-criteria evaluation, beyond the pure performance reach. The steps required...
Xsuite is a Python-based simulation framework for beam dynamics studies in circular accelerators, and is progressively becoming a core tool for several FCC design studies. Recent developments include the implementation of a Particle-in-Cell (PIC) beam-beam interaction model, a module for Intra Beam Scattering (IBS), and native support for wakefield effects. The optics toolkit has also been...
A major project such as the FCC-ee, with a circumference of 91.17 km, presents numerous challenges to guarantee the stability and performance of the machine. As part of the efforts to optimize energy consumption during its operation, the use of Nested Magnets has been explored as a potential method to reduce synchrotron radiation. This talk will address the challenges and solutions associated...
The Future electron-positron Circular Collider, FCC-ee, is a proposed next collider aiming, to provide unprecedented luminosities at beam energies ranging from 45.6 up to 182.5 GeV. One of the major challenges is delivering the ambitious design performance in the presence of realistic misalignment and field errors. A commissioning strategy has been developed including dedicated optics designs,...
The proposed electron-positron Future Circular Collider (FCC-ee) is planned to achieve unprecedented high luminosity, enabling answers to fundamental questions in high-energy physics. Magnets field imperfections and misalignments significantly impact beam dynamics and can strongly affect the collider’s performance. In this contribution, we present the current status of a developed correction...
This presentation provides a concise overview of recent integrated simulation studies conducted for the FCC-ee accelerator. It covers key performance aspects, including the impact of varying sextupole strengths during commissioning on particle dynamics, degradation effects due to imperfections in the -I transform, and sensitivity to different ground motion scenarios. Additional topics include...
The ambitious design goals of the Future electron-positron Circular Collider (FCC-ee) demand excellent orbit and optics control and, therefore, set strict limits on alignment tolerances. One approach to relax the mechanical alignment tolerances is Beam-Based Alignment (BBA), where corrector magnets steer the beam towards the magnetic centre. One of the key challenges of FCC-ee is developing an...
The performance of the Future Circular Collider - electron-positron (FCC-ee) relies critically on the precise alignment of its Interaction Region (IR) components. Small misalignments can significantly degrade the dynamic aperture and luminosity, demanding stringent control of mechanical tolerances. This study uses detailed tuning simulations developed in pyAT, to determine the acceptable...
The FCC-ee low-energy machine, operating at 45.6 GeV, is the most affected by the collective effects because of the lowest beam energy combined with the highest beam current, the lowest emittances and the longest damping times. The design of this machine is still in progress, and the coupling impedance budget is continuously evolving in parallel with the updates of the vacuum chamber...
A comprehensive impedance model is essential to ensure beam stability and optimize performance in the FCC-ee main rings. In this talk, we present the current status of the impedance budget, developed as part of the ongoing FCC-ee design studies. The model includes contributions from a wide range of components — including beam pipe, collimators, bellows, tapers, RF cavities and beam position...
Beam stability in the FCC-ee collider is critically influenced by both transverse and longitudinal beam coupling impedance. The development of a flexible and comprehensive impedance model is essential for accurately evaluating and mitigating instabilities as machine parameters evolve.
The collimation system has been identified as a dominant contributor to the total machine impedance. This...
This presentation discusses the various collective instabilities that arise in the FCC-ee at Z energy. Intensity limitations in both the vertical and horizontal planes are influenced by the combined effects of beam-beam interactions and impedance. In the vertical plane, the transverse mode repulsion instability, driven by impedance, is a limiting factor, while in the horizontal plane, the...
The FCC-ee may face significant challenges related to electron cloud effects. These effects are expected to be most pronounced in the Z configuration, due to the highest number of bunches, which leads to the smallest bunch spacing, which is a key parameter in the e-cloud formation process. A high electron density within the beam pipe can limit accelerator performance through several...
Xsuite enables detailed beam dynamics simulations including full lattice descriptions, synchrotron radiation, lattice errors, corrections and beam-beam effects. In this work we explore the interplay by these effects by systematically combining individual effects to produce and understand comprehensive simulations and complex behaviour. We also explore different dynamic indicators including...
