Conveners
FCC-ee accelerators: FCC-ee parameters, layout, overview, with booster
- Evgeny Levichev (Budker Institute of Nuclear Physics (RU))
FCC-ee accelerators: FCC-ee optics, correction, beam stay-clear, dynamic aperture, collimation
- Eliana Gianfelice-Wendt (FNAL)
FCC-ee accelerators: FCC-ee electron cloud & vacuum
- kyo shibata (KEK)
FCC-ee accelerators: FCC-ee injector complex
- Tor Raubenheimer (SLAC)
FCC-ee accelerators: FCC-ee IR and MDI
- Wolfgang Hillert (University of Hamburg)
FCC-ee accelerators: FCC-ee impedance & collective effects
- Ursula Helga Van Rienen
FCC-ee accelerators: FCC-ee other applications & upgrades
- Mike Seidel (PSI)
The main parameters of the FCC-ee collider are fixed in the CDR, but this does not mean that they will not change anymore. Further and deeper consideration of this project reveals new problems, both physical and technical, and new ideas appear. This mainly concerns the operation at low energy, where a large total beam current can lead to various collective instabilities. We will discuss some...
A comparison is made on the beam optics, dynamic aperture and luminosity performance for several layouts of the collider ring. If the periodicity of the lattice is preserved, no exceptional issue has been found; the luminosity is simply limited by the synchrotron radiation corresponding to the ring circumference.
Some studies on the lattice periodicity and shortening the distance between...
Possible circular colliders for the post-LHC era at CERN are being explored within the framework of the Future Circular Collider (FCC) feasibility study. The first stage of the FCC integrated project is the FCC-ee, an ambitious electron-positron collider with a circumference of approximately 100 km. Certain key concepts of the FCC-ee design can be demonstrated and tested at existing...
Top-up operation is essential for FCC-ee to maximize the integrated luminosity. Numerous constraints and requirements have to be met: limited dynamic aperture, transparency of the injection process, compatibility with four operation modes, reliability, availability, machine protection, etc. This presentation first summarizes the status of the design study, and then important next steps are...
To achieve ultra-low vertical emittance a highly effective emittance tuning scheme is required. We will describe a comprehensive correction strategy used for the low emittance tuning. The strategy includes Dispersion Free Steering, linear coupling compensation based on Resonant Driving Terms and beta beat correction utilising response matrices.
We present the latest results obtained from comparing various codes used for simulating the FCC-ee optics. The three codes used for this study are SAD, MADX and the MADX PTC implementation. The aim of the comparisons is to determine how reliably the codes can simulate various aspects of the accelerator, including the emittance, the linear optics and the dynamic aperture. We will also present...
The FCC-ee project faces new challenges specific to larges scale lepton colliders, which requires new developments of simulation tools. While many different codes exist that address key aspects of the FCC-ee project, it is often complicated, if not impossible, to combine these and merge functionalities.
This talk presents a comparison and benchmarking of several optics codes for the FCC-ee,...
The FCC-ee design pushes parameters such as the beam energy, the stored beam energy, and the total synchrotron radiation power beyond the values achieved at existing machines. Ensuring safe machine operation and minimising background to detectors are important requirements. The first studies of the aperture limitations and the first considerations for a collimation system in the FCC-ee are...
The design parameters of the FCC-ee foresee operation with a total stored beam energy of about 20MJ, exceeding those of previous lepton colliders by almost two orders of magnitude. Given the inherent damage potential, a halo collimation system is studied to protect the machine hardware, in particular superconducting equipment such as the final focus quadrupoles, from sudden beam loss. In this...
An analysis of the synchrotron radiation spectra and photon power and flux distribution along one sample sector of 140 m length representative of the FCC-ee arcs has been carried out using the raytracing montecarlo code SYNRAD+. The results of these simulations have then been used to derive the photon stimulated desorption (PSD) for different conditioning times, for the Z-pole machine. The...
The FCC-ee arc region is significantly impacted by the synchrotron radiation (SR) emitted by the electron and positron beams. In order to assess its actual effect on the magnets and tunnel environment, FLUKA simulations were performed for the most challenging case of top-pole operation at 182.5GeV. In this presentation, the advantages and disadvantages of two different solutions are discussed....
FCC-ee has an unprecedented design and operational parameters. For this reason, it is prone to suffer from beam-vacuum chamber detrimental interaction potentially affecting its performance. Vacuum, impedance, e-cloud instabilities are some of the issues that need to be mitigated from the design phase. This contribution analyses some of the requirements accelerator vacuum walls must obey to be...
In high-energy particle accelerators, electron clouds may occur due to high synchrotron radiation-related photoemissions, residual gas ionization, and secondary emissions during positively charged beam circulations in the vacuum chambers. The electron cloud formation could cause beam losses, trajectory changes, and wakefields. This study presents electron cloud build-up investigations for...
The electron cloud is one of the critical issues to be addressed due to its capability to affect the FCC-ee accelerator performance and degrade beam quality, in particular, for the arcs of the machine. In this work, we report the first part of a series of studies on electron cloud build-up for the arc quadrupole sections. Variations mainly on beam energies, beam pipe radii, and secondary...
The FCC-ee injector complex has to deliver the beam for top up injection in the two collider rings supporting a beam duration of about one hour on the Z-pole and up to 12 minutes for higher energy modes of operation. In addition, the injector also has to allow a fairly rapid fill-up from zero within half an hour at most. The high beam current of this collider create challenging requirements on...
Progress in the design of the linacs and electron sources for the FCC-ee injector complex will be reported
In the framework of the design and realization of a lepton collider, positron sources are essential due to the challenging critical requirements of high-beam intensity and low emittance necessary to achieve high luminosity. In the case of positron beams to be injected into circular colliders, the main concern is an optimized 6D emittance, whereas very high intensities are required for linear...
FCC-ee aims extremely high luminosities during its all operational modes: Z, W, H and top quark. Especially, the Z run steps forward amongst the other stages due to the very high stored charge, i.e. 1.4 A, in the collider. Therefore, the injectors need to provide the collider fill from the scratch as well as maintain the luminosity at the peak thru operation by making use of the...
The high-energy booster is the last part of the accelerator complex before the FCC-ee collider.
The booster has to handle several challenges common to the FCC-ee collider like fitting the 100-km-long tunnel, reaching low equilibrium emittances, or longitudinal stability because of a very small momentum compaction.
Nevertheless, the booster has also specific challenges. At injection, magnetic...
The design of the interaction region of the positron-electron future circular collider must comply with various important constraints, imposed by high beam energy, high luminosity, need for polarization, and crossing scheme. An overview of the MDI design will be presented with a picture of the recent results and ongoing studies. In particular, the mechanical model of the MDI has been started...
The study of unavoidable backgrounds of various sources that may affect the quality of the useful collider data is essential to assess its success. The design and optimization of both the detector and the machine therefore require realistic estimations of beam induced backgrounds. The development of interfaces for the relevant existing codes with the detector and physics simulation software...
A first, single aperture, final focus quadrupole prototype has been designed, constructed and tested at warm. It is a canted cosine theta (CCT) design with the novel feature of eliminating edge effects in field quality. The measurements at warm show that the edge effects correction works beautifully and the overall field quality is excellent with errors not exceeding 0.15 units for all multipoles.
The presentation concerns: the preliminary assembly of the MDI, including vacuum chamber, quadrupoles and solenoids; a parametric mechanical analysis of the vacuum chamber and the preliminary study of heat removal in the central beam pipe.
The mechanical study examines the structural behaviour of the chamber at many thickness values, using FEA techniques.
The preliminary heat transfer...
The alignment of the Machine Detector Interface (MDI) is crucial to obtain the desired luminosity but also extremely challenging due to the complexity of this region.
This presentation will highlight the different challenges and difficulties encountered so far in the FCC-ee MDI. Then it will give an overview of the existing systems in other similar MDI but also ideas proposed in projects of...
Collective effects generated by the high beam intensities for FCC-ee, in particular for the Z-pole configuration, have to be carefully analyzed. We have found that the resistive wall represents a major source of impedance, but also the bellows with RF fingers make another important contribution. With the impedance model evaluated so far for this machine, thresholds for single bunch...
Improving the accuracy of the impedance model of an accelerator is important for keeping beam instabilities and power loss under control. Here, by means of the PyHEADTAIL tracking code, we first review the longitudinal microwave instability threshold for FCC-ee by taking into account the longitudinal impedance model evaluated so far. Moreover, we present the results of beam dynamics...
In the framework of the FCC project, the development of an accurate beam coupling impedance model of the accelerator elements represents an important aspect for reaching the machine design performances.
A significant contribution to the total coupling impedance is provided by bellows and vacuum flanges, for which an accurate electromagnetic characterization is required.
In this work a...
With large Piwinski angle collision, both luminosity and beam-beam tune shifts depend on the bunch length. The longitudinal beam dynamics also plays an essential role for several new effects, such as beamstrahlung, coherent X-Z instability and 3D flip-flop. The combined effect of longitudinal impedance and beam-beam interaction should be taken into account for the collider luminosity...
In the SuperKEKB, which is a two-ring collider consisting of 4 GeV positron and 7 GeV electron storage ring, movable collimators have been installed in order to reduce the backgrounds in the detector and avoid quenches in superconducting final focusing magnets. Therefore, the movable collimators are one of the indispensable components in SuperKEKB for the machine operations. We developed...
Many synchrotrons are upgrading their lattice to reach lower horizontal emittances below 100 pm rad. The project foreseeing the lowest emittance is PETRA IV with the aim of reaching about 10 pm rad. The very large circumference of the FCC-ee booster combined with damping wigglers allows to reach a horizontal beam emittance down to 0.5 pm rad. This would push the diffraction limit from 10 keV...
I will present the case for performing experiments with hard X-ray synchrotron radiation. The spectral brightness of existing undulator-based storage rings in the hard X-rays regime is limiting the applications above ~30 keV where the beam coherence becomes small. This results in limitations of the flux available for many experiments. In particular, X-ray imaging could benefit from the...
We report on the possible use cases for an highly intense low energy positron source in the light of the FFC-ee project. Slow positrons can be used to create the purely leptonic hydrogen-like positronium (Ps) atom, the bound state of an electron and a positron. Since it does not contain a hadronic nucleus, it is a privileged system to research bound-state QED. Notably, theoretical results...
We presenting recent development of concept for future the energy-efficient ERL-based high-energy high-luminosity e+e- collider. This collider can be placed in 100 km tunnel for future FCC and collide highly polarized electron and position beam with c.m. energy up to 600 GeV.
A new muon collider collaboration is forming with the aim to develop this unique concept for a very high energy lepton collider. The presentation will introduce the collider and its challenges. It will also comment on options to use the FCC infrastructure for this purpose.
