Beam-beam Blowup in the presence of x-y coupling sources at FCC-ee

FCC-ee, the lepton version of the Future Circular Collider (FCC), is a 100 Km future machine under study to be built at CERN. It acquires two experiments with a highest beam energy of 182.5 GeV. FCC-ee aims to operate at four different energies, with different luminosities to fulfil physics requirements. Beam-beam effects at such a high energy/luminosity machine are very challenging and require a deep understanding, especially in the presence of x-y coupling sources. Beam-beam effects include the beamstrahlung process, which limits the beam lifetime at high energies, as well as dynamic effects at the Interaction point (IP) which include changes in the beta functions and emittances. In this report, we will define the beam-beam effects and their behaviours in the FCC-ee highest energy lattice after introducing x-y coupling in the ring

The electron cloud instability: summary of measurements and understanding

Electron-cloud effects presently limit the performance of several accelerators operating with high beam current, notably the SLAC and KEK B factories, the CERN SPS, the CERN PS, and the Los Alamos PSR. They are a major concern for many future projects, e.g. the CERN LHC and the SNS. An electron cloud is generated in the vacuum chamber by photoemission or beam-induced multipacting and subsequent electron accumulation during a bunch or bunch-train passage. Both coupled and single bunch instabilities, pressure rise, malfunctioning of beam diagnostics and failures of multi-bunch feedback systems have all been attributed to the cloud of electrons. We compare observations from various laboratories with computer simulations and analytical estimates, and we address mechanisms by which the electrons may dilute the beam emittance. Possible cures and future research directions are also discussed

Considerations on Tevatron Luminosity and Performance: Fnal, November 7 - December 17, 2002

This report contains a loose collection of studies and considerations on various limitations of Tevatron luminosity and performance. These are either analytical calculations, computer simulations, or studies based on an Offline Shot Data Analysis (OSDA) of many stores, using JAVA packages provided by P. Lebrun, S. Panacek, et al. The results of six dedicated or end of-the-store machine studies performed during my stay at Fermilab are not included and will be published separately. Specifically, the topics we address here comprise the expected and measured luminosity, hourglass effect, dynamic beta function, beam lifetime at injection and in collision, beam losses at the start of the ramp, electron-cloud build up for uncoalesced beams and for Run-IIb, potential-well distortion, intrabeam scattering, and Touschek effect. The treatments of the various subjects strongly difer in completeness and maturity. For example, the results on intrabeam scattering and Touschek scattering look definitive, whereas studies of beam loss and lifetime have not reached a final conclusion

Tutorial on Linear Colliders

Proceeding from the collision point towards the source, we discuss purpose and design concepts of the various linear-collider subsystems, as well as important mechanisms of emittance dilution, beam diagnostics, and advanced tuning methods. In particular, we address beamstrahlung, linac emittance degradation due to dispersion and wake fields, scaling of damping-ring parameters with collider energy, fast beam-ion and electron-cloud instabilities, coherent synchrotron radiation, and rf guns. Five case studies are examined in detail

CERN Upgrade Plans for the LHC and its Injectors

The primary goal of CERN and the Large Hadron Collider (LHC) community is to ensure that LHC is operated efficiently, that it achieves nominal performance in the shortest term, and that its performance steadily improves. Since several years the community has been discussing the directions for maximizing the physics reach of the LHC by upgrading the experiments, in particular ATLAS and CMS, the LHC machine and the CERN proton injectors, in a phased approach. The first phase comprises construction of a new proton linac, LINAC4 and an LHC interaction-region (IR) upgrade, with the goal of increasing the LHC luminosity to 2 − 3 × 1034 cm−2s−1, while maximizing the use of mature magnet technologies and of the existing infrastructure. These two projects were approved by the CERN Council in December 2007 and are scheduled for completion in 2014. The second phase foresees further substantial improvements in the injector chain, with a proposed replacement of the aging PS and its booster, by a superconducting proton linac (SPL) and a new higher-energy storage ring, PS2, complemented by modifications in the existing SPS, together with major upgrades of the ATLAS and CMS detectors, and, possibly, including another upgrade of the interaction regions based on a different magnet technology, as well as complementary measures such as crab cavities, or a new beam structure. Completion of this second phase around 2018-2020 should allow further increasing the luminosity of the LHC towards 1035 cm−2s−1. On an even longer time scale, the magnet technology developed for the second phase could provide the route towards an ultimate energy upgrade of the LHC. In this report, I first recall a few key challenges inherent in the LHC baseline design, and then describe phased upgrade scenarios for the LHC and its injectors which overcome the design limitations and may ultimately lead to a 10-fold luminosity increase

Fringe Fields, Dynamic Aperture and Transverse Depolarisation in the CERN Muon Storage Ring

We evaluate the dynamic aperture for the CERN muon storage ring, and, in particular, study the effect of magnet fringe fields. The detuning with amplitude is computed via normal-form analysis. Particle tracking reveals the dependence of the dynamic aperture on betatron tune and momentum offset, and demonstrates satisfactory performance. The depolarisation in transverse phase space is estimated from a spin normal form. All calculations are performed with the computer codes COSY INFINITY and MAD

Tune Shift with Amplitude Induced by Quadrupole Fringe Fields

Using Lie algebra techniques, we derive an analytical expression for the nonlinear Hamiltonian and the linear tune shift with amplitude due to quadrupole fringe fields. Numerical examples for the FNAL muon storage ring is compared with results from the computer code COSY INFINITY