The design of FCC-ee is relying on the accumulated experience of
e
+
e
-
colliders that have been designed, constructed and operated in the past 40 years. FCC-ee will surpass the 26.7 km long Large ...Electron Positron collider LEP by a factor 4 in size. Like for LEP the large size is justified by the need to control the synchrotron radiation losses that for both machines reach a few percent per turn. To that end LEP had the first large super-conducting (SC) RF system with around 3.8 GV of accelerating voltage. LEP achieved for the first time very large beam-beam parameters of around 0.08, and it relied on transversely polarized beams to determine accurately the beam energy for the experiments. The DA
Φ
NE collider, together with PEP II and KEKB split the two beams into separate vacuum chambers to reach much higher Ampere-level beam currents. To overcome beam-beam lifetime and performance issues DA
Φ
NE used for the first time the Crab Waist concept for the interaction region (IR) optics. The B-factories, PEP-II and KEKB have verified the double-ring
e
+
e
-
collider with multi-ampere stored currents for over 1000 bunches, small
β
∗
, top-up injection, and achieved then-highest luminosity. KEKB has applied 22-mrad crossing angle at the IP with crab crossing. Both machines inherited accelerator techniques from their predecessors, PEP and TRISTAN, which was a small-scale LEP. Currently the next generation SuperKEKB collider is starting up. It has already achieved some milestones required for FCC-ee such as small
β
∗
(0.8 mm) and virtual crab-waist scheme with a large Piwinski angle (>10).
Future Circular Colliders Benedikt, M; Blondel, A; Janot, P ...
Annual review of nuclear and particle science,
10/2019, Letnik:
69, Številka:
1
Journal Article
Recenzirano
Odprti dostop
After 10 years of physics at the Large Hadron Collider (LHC), the particle physics landscape has greatly evolved. Today, a staged Future Circular Collider (FCC), consisting of a luminosity-frontier ...highest-energy electron-positron collider (FCC-ee) followed by an energy-frontier hadron collider (FCC-hh), promises the most far-reaching physics program for the post-LHC era. FCC-ee will be a precision instrument used to study the
Z
,
W
, Higgs, and top particles, and will offer unprecedented sensitivity to signs of new physics. Most of the FCC-ee infrastructure could be reused for FCC-hh, which will provide proton-proton collisions at a center-of-mass energy of 100 TeV and could directly produce new particles with masses of up to several tens of TeV. This collider will also measure the Higgs self-coupling and explore the dynamics of electroweak symmetry breaking. Thermal dark matter candidates will be either discovered or conclusively ruled out by FCC-hh. Heavy-ion and electron-proton collisions (FCC-eh) will further contribute to the breadth of the overall FCC program. The integrated FCC infrastructure will serve the particle physics community through the end of the twenty-first century. This review combines key contents from the first three volumes of the FCC
Conceptual Design Report
.
Beam-based alignment of the SuperKEKB linac quadrupoles Ogur, S.; Iida, N.; Kamitani, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2019, Letnik:
925
Journal Article
Recenzirano
The positron linac of SuperKEKB contains accelerating structures surrounded by quadrupoles without nearby beam-position-monitors (BPMs) or steering magnets. In this situation, standard techniques for ...beam steering or beam-based-alignment are not efficient. We here present a method to determine the magnetic centers of individual SuperKEKB linac quadrupoles. This method is independent of any BPM offsets. The beam position at the quadrupole under study is scanned, and for each position the quadrupole strength is varied, so as to find the location of zero deflection. Unlike other method used in the past, this technique does not rely on any transfer matrices. Interpolation is possible even to quadrupoles without BPM by assigning ‘virtual BPMs’. We show that the misalignment of the quadrupoles with BPM in the bore can be determined with an rms error of ≤37μm; for quadrupoles without proper BPMs the error is σ≤112μm.
Optimized injector schemes for FCC-ee positron production Bai, B.; Faus-Golfe, A.; Han, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2021, Letnik:
1009
Journal Article
Recenzirano
Odprti dostop
Injectors and in particular the positron production systems are a crucial element in linear and circular colliders. The proposed FCC-ee injector linac accelerates both electrons and positrons up to 6 ...GeV in order to be injected into the Pre-Booster Ring (PBR) with a high intensity of 3.5 nC per bunch for the Z running mode. The current design baseline of the FCC-ee injector linac is based on the SuperKEKB scheme, in which the electron and the positron beams share the same linacs with a fixed target configuration on-axis hole for electron beam passage. One of the main drawbacks of this scheme is the positron production efficiency at the exit of the injector linac. In order to achieve a better performance and a higher positron yield, in this paper we study different bypass injection options. Start-to-end design and optimization for beam production, acceleration and transport from the feeding electron source to the positron damping ring are also being presented.
Top-up injection schemes for future circular lepton collider Aiba, M.; Goddard, B.; Oide, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2018, Letnik:
880
Journal Article
Recenzirano
Odprti dostop
Top-up injection is an essential ingredient for the future circular lepton collider (FCC-ee) to maximize the integrated luminosity and it determines the design performance. In ttbar operation mode, ...with a beam energy of 175 GeV, the design lifetime of ∼1 h is the shortest of the four anticipated operational modes, and the beam lifetime may be even shorter in actual operation. A highly robust top-up injection scheme is consequently imperative. Various top-up methods are investigated and a number of suitable schemes are considered in developing alternative designs for the injection straight section of the collider ring. For the first time, we consider multipole-kicker off-energy injection, for minimizing detector background in top-up operation, and the use of a thin wire septum in a lepton storage ring, for maximizing the luminosity.
The Future Circular Collider (FCC) e^{+}e^{-} injector complex needs to produce and transport high-intensity e^{+} and e^{-} beams at a fast repetition rate for topping up at collision energy. Two ...options are considered for a preaccelerator ring, to be used for an intermediate accumulation and acceleration before the bunches are transferred to the high-energy booster. One option is a slightly modified Super Proton Synchrotron (SPS), and the other is designing a new ring. We explore the needs and parameters of the existing SPS as prebooster ring and also develop a conceptual design of an alternative accelerator ring. After establishing the basic parameters, we describe the optics design and layout and discuss the single-particle linear and nonlinear dynamics optimization, including magnetic and alignment errors. In addition, we present synchrotron radiation power studies and analytical estimates of various collective effects for both prebooster ring design options, including space charge, intrabeam scattering, longitudinal microwave instability, transverse mode coupling instability, ion effects, electron cloud, and coherent synchrotron radiation.
A beam optics scheme has been designed for the future circular collider-e+e− (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction ...points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme P. Raimondi, D. Shatilov, and M. Zobov, arXiv:physics/0702033; P. Raimondi, M. Zobov, and D. Shatilov, in Proceedings of the 22nd Particle Accelerator Conference, PAC-2007, Albuquerque, NM (IEEE, New York, 2007), p. TUPAN037. with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called “tapering” of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) A. Chancé et al., Proceedings of IPAC’16, 9–13 May 2016, Busan, Korea, TUPMW020 (2016). as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than ±2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets. The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study.
Many yield functions have been proposed in academia to describe the complicated shapes of yield surfaces of metals. However, many of the commercial FEM codes provide only classical yield functions. ...Moreover, it takes a long time for engineers to implement newly proposed yield functions to commercial FEM codes. The Japan Association for Nonlinear CAE (JANCAE), a non-profit organization, developed the Unified Material Model Driver for plasticity (UMMDp) subroutine suite with the cooperation of industry users of CAE and the engineers of software venders. This subroutine provides several anisotropic yield functions, and is applicable to most of the commercial FEM codes. The users can implement their own anisotropic yield functions easily using the UMMDp. This paper presents the basic framework of UMMDp and the development activities performed with many volunteers.
To implement new yield functions into the user subroutines of advanced FE codes, professional skills and knowledge are required. The Japan Association for Nonlinear Computer Aided Engineering ...(JANCAE) has been acting as an organization that provides information and knowledge on finite element analysis (FEA) to the researchers and engineers in various positions involved in CAE. Since 2009, as one of the subcommittee activities for applying FEA to practical metal-forming problems, we have not only studied elastoplastic theory, but have also developed the Unified Material Model Driver for Plasticity (UMMDp), a user subroutine library. Basic yield functions, such as the von Mises and Hill's quadratic yield functions, which almost all advanced FE code already has, were implemented in the UMMDp as a basic study at its beginning of the development. Up to now, many anisotropic yield functions, including Yoshida's 6th-order polynomial, Barlat's Yld2000 and Yld2004, Comsa and Banabic's BBC2008, Cazacu's CPB2006, and Vegter's spline yield functions, have been implemented in the UMMDp, and it is possible to add a new yield function. In this presentation, the techniques for implementing yield functions in the UMMDp are explained. Moreover, the problem of BM1 in NUMISHEET 2016 is discussed as an example applying selected yield functions to the implementation procedure.
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