Low Emittance Tuning of FCC-ee Charles, T.K.; Aumon, S.; Holzer, B. ...
Journal of physics. Conference series,
11/2019, Letnik:
1350, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The FCC-ee project studies the design of a future 100 km e+/e circular collider for precision studies and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities ...in the order of 1035 cm-2 s-1. In order to reach these luminosity requirements, strong focusing is needed in the interaction regions. Large maximum beta values (of 7736 m for the Z energy) and the small beta star values, make the FCC-ee lattices particularly susceptible to misalignments and field errors. FCC-ee therefore presents an appreciable challenge for emittance tuning. In this paper, we describe a comprehensive correction strategy used for the low emittance tuning. The strategy includes programs that have been developed to optimise the lattice based on Dispersion Free Steering, linear coupling compensation based on Resonant Driving Terms and beta beat correction utilising response matrices. One hundred misalignment and field error random seeds were introduced in MAD-X simulations and the final corrected lattices are presented.
Abstract
During 2022, a dedicated study was undertaken at CERN, together with the FCC Feasibility Study collaborators, to propose a robust configuration for the FCC-ee arc half-cell. The proposed ...layout considers integration aspects of the elements in the arc cross section, both for the booster and the collider, as well as aspects related to powering, cooling and ventilation, supporting and alignment, optics, instrumentation, handling and installation. The interfaces between the arc elements and the straight sections have also been analysed. This paper summarizes the main conclusions of the assessment and reports the preliminary engineering analyses performed to design the supporting system of the booster and of the collider. A proposal for a possible mock-up of the arc half-cell, to be built at CERN in the next years, is also presented.
The Future Circular e + e − Collider pre-injector chain consists of a 6 GeV S-Band linac, a damping ring at 1.54 GeV and pre-booster ring to reach 20 GeV for injection to the main booster. The ...electron and positron beams use the same accelerator chain alternatively. The e −beam is generated from a novel low level RF-gun providing 6.5 nC charge at 11 MeV with 0.5 micron geometric emittance. The e + beam is produced by the impact of a 4.46 GeV e − beam onto a hybrid target, accelerated in the linac up to 1.54 GeV, and injected to the damping ring for emittance cooling. Simulations on the performance of the DR are presented for reaching the required equilibrium emittances at the required damping time. As an alternative option, a 20 GeV linac is considered utilising C-Band cavities and simulations studies have been undertaken regarding the beam transport and transmission efficiency up to that energy.
The Future Circular e+ e- Collider (FCC-ee) requires two 180-degree turnaround loops to transport the positron beam from the damping ring to the lower energy section of the linac. In addition bunch ...compression is required to reduce the RMS bunch length from 5 mm to 0.5 mm, prior to injection into the linac. A dogleg bunch compressor comprised of two triple bend achromat (TBAs) can achieve this compression. Sextupole magnets are incorporated into the bunch compressor design for chromaticity correction as well as optimisation of the second-order longitudinal dispersion, T566, and to linearize the longitudinal phase space distribution. In this paper we present the design of the transport line and the bunch compressor. Measures to limit emittance growth due to coherent synchrotron radiation (CSR) are also discussed, because despite the relatively long bunch length, the large degree of bending required introduces cause for consideration of CSR.
SuperKEKB is an electron–positron asymmetric-energy double-ring collider, which was built in Japan. It has been operated to explore new phenomena in B-meson decays. Hence, extremely higher luminosity ...is required. A collision scheme of low emittance with a large Piwinski angle called a “nano-beam scheme” has been adopted to achieve higher luminosity by squeezing the vertical beta function at the interaction point to be smaller than the bunch length. A “crab waist collision scheme” proposed by P. Raimondi et al. has also been adopted to improve the luminosity performance. The article presents an overview of the operation of the nano-beam and crab waist collision schemes at SuperKEKB.
The design of a 100 km circular e+e− collider with extremely high luminosity is an important component of the global Future Circular Collider (FCC) study hosted by CERN. FCC-ee is being designed to ...serve as Z, W, H and top factory, covering beam energies from 45.6 to 175 GeV. For the injectors, the Z-operation is the most challenging mode, due to the high total charge and low equilibrium emittance in the collider at this energy. Thus, fulfilling the Z-mode will also meet the demands for all other modes of FCC-ee. This goal can be achieved by using a 6 GeV NC linac with an S-band RF frequency of 2.856 GHz and a repetition rate of 100 Hz. This linac will accelerate two bunches per RF pulse, each with a charge of 6.5 nC. Positrons will be generated by sending 4.46 GeV e− onto a hybrid target so that the e+ created can still be accelerated to 1.54 GeV in the remaining part of the same linac. The emittance of the e+ beam will then shrink to the nm level in a 1.54 GeV damping ring. After damping, the e+ will be reinjected into the linac and accelerated to 6 GeV. The e− and e+ will then be accelerated alternately to 45.6 GeV in the booster, before they are injected into the collider.
In the frame of the FCC study we are designing a 27 TeV hadron collider in the LHC tunnel, called the High Energy LHC (HE-LHC). The HE-LHC can be realized by replacing the LHC's 8.33 T ...niobium-titanium dipole magnets with 16 T niobium-tin magnets developed for FCC-hh. A high-quality beam available from the upgraded LHC injector complex and significant radiation damping allow achieving the challenging target values for both peak and integrated luminosity required by particle physics. Tunnel integration determines the maximum outer size of the magnet cryAPCostat. The HE-LHC arc optics maximizes the dipole filling factor and optimizes the dynamic aperture, while limiting the field strengths of quadrupoles and sextupoles. The low-beta optics for the experimental insertions features a shielded quadrupole triplet even longer than the HL-LHC's, which can support an interaction-point beta function of 25 cm, and survive an integrated luminosity above 10/ab. Other challenges include collimation and extraction. The choice of injection energy and injector is another important element, and so are various collective effects. We here report the HE-LHC design status.
Wrinkling during draw is typically a local instability problem. When the structural instability is localized, there will be a local transfer of strain energy from one part of the structure to ...neighboring parts, and global solution methods, which is typically represented by the arc length method, may not work. So, this type of problems has to be solved either dynamically or with the artificial damping. On the other hand, the essential nature of the buckling behavior can be regarded as a static problem, even though it may be possible to raise some side issues due to the inertia effect. In this study, we traced the local buckling behavior of anisotropic elasto-plastic thin shells in Numisheet2014 BM4 using the artificial damping method.
During 2008 and 2009 dedicated beam experiments with crab cavities were performed in the KEKB. The goal was to measure the impact of crab-cavity radio frequency (rf) noise on the beam quality. These ...experiments were performed as a validation of the crab-cavity beam dynamics models in view of the possible use of crab cavities in the upgrade of the CERN Large Hadron Collider (LHC). An unexpected strong beam-beam instability was observed during the course of the experiments as a kind of frequency response. Understanding this finding required extensive multiparticle and single particle simulations plus an extra experimental session to consolidate the observations.
PDF
