Keyword: damping
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TUT1BH2 Study of Coherent Head-tail Instablility Due to Beam-beam Interaction in Cirular Colliders Based on Crab Waist Scheme ion, simulation, luminosity, emittance 61
 
  • K. Ohmi
    KEK, Ibaraki, Japan
  
  FCC-ee is being studied various collision schemes, head-on and large Piwinski angle/ crab waist schemes. We discuss beam-beam limit in the collision schemes using weak-strong and strong-strong models.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT1BH2  
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TUT2H5 Towards a Preliminary FCC-ee Injector Design ion, emittance, linac, positron 90
 
  • S. Ogur, Y. Papaphilippou, F. Zimmermann
    CERN, Geneva, Switzerland
  • A.M. Barnyakov, A.E. Levichev, D.A. Nikiforov
    BINP SB RAS, Novosibirsk, Russia
  • K. Furukawa, N. Iida, F. Miyahara, K. Oide
    KEK, Ibaraki, Japan
  
  The Future Circular Collider-ee aims to get high luminosity which mainly relies upon high charge and low geometric emittance in the collider. The FCC-ee is a future project of CERN to operate as Z, W, H and tt factories with varying energies between 45.6 to 175 GeV. Among those, the total charge requirement is peaked for Z-operation (i.e. 91500 bunches of electron and positron with 3.3·1010 particles per bunch) meanwhile this mode targets the smallest geometric emittance in the Collider. To reach the goal, the normal conducting S-band Linac has been designed to accelerate 4·1010 particles in a bunch to 6 GeV and send two bunches per RF pulse within a repetition of 100 Hz. The FCC-ee positrons will also be created inside the linac at 4.46 GeV and accelerated to 1.54 GeV. These positrons are damped at the designed Damping Ring at that energy, and then transferred back to the Linac to meet the same characteristics of electrons. Therefore, in this paper, we'd like to discuss the transmission and robustness of the Linac and the dynamic aperture of the Damping Ring which has to be large enough to accept the incoming beam and cover the probable shrink due to the misalignments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT2H5  
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TUT3AH2 Instability Issues in CEPC ion, impedance, cavity, coupling 108
 
  • N. Wang, W. Chou, J. Gao, D.J. Gong, J. He, Q. Qin, Y.S. Sun, D. Wang, Y. Wang, G. Xu, Y. Zhang, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  • K. Ohmi, D. Zhou
    KEK, Ibaraki, Japan
  
  The CEPC is a high energy circular electron-positron collider under design. Large bunch population is required to achieve the design luminosity. Instabilities driven by the coupling impedance are possible limitations for reaching high machine performance. An updated impedance model, including the resistive wall and the main vacuum components, has been obtained for the main ring. Based on the impedance model, the collective instability issues of the beam with the partial-double ring design are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH2  
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TUT3AH3 Beam-based Impedance Measurement Techniques ion, impedance, vacuum, simulation 112
 
  • V.V. Smaluk
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by DOE under contract No.DE-AC02- 98CH10886
Characterization of a vacuum chamber impedance is necessary to estimate stability conditions of a particle beam motion, to find a limit of the beam intensity and characteristic times of single-bunch and multi-bunch instabilities. For new accelerator projects, minimization of the vacuum chamber impedance is now the mandatory requirement. For an accelerator in operation, the impedance can be measured experimentally using various beam-based techniques. The beam-impedance interaction manifests itself in measurable beam parameters, such as betatron tunes, closed orbit, growth rates of instabilities, bunch length and synchronous phase. The beam-based techniques developed for measurement of the longitudinal and transverse impedance are discussed, including theoretical basics and experimental results. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH3  
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TUT3AH5 Electron Cloud and Ion Effects and Their Mitigation in FCC-ee ion, electron, feedback, simulation 120
 
  • K. Ohmi, H. Fukuma, M. Tobiyama
    KEK, Ibaraki, Japan
  
  Electron cloud and fast-ion instabilities are serious issues for colliders operated with high current and many bunches. We discuss the instabilities in FCC-ee/hh based on simulations and experiences of KEKB/SuperKEKB.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH5  
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TUT3AH9 Feedback Systems for FCC-ee ion, feedback, kicker, pick-up 136
 
  • A. Drago
    INFN/LNF, Frascati (Roma), Italy
  
  In this paper, some preliminary considerations on the feedback systems for FCC-ee are developed. Bunch-by-bunch feedback systems have been de-signed in the last years for other e+/e− colliders like PEP-II, KEKB, DAΦNE, SuperB and SuperKEKB. In all these cases, similar approaches have been implement-ed, even if some design variations have been suitable or necessary for different reasons. Bunch-by-bunch feedback systems are based on the concept that the barycenter of each bunch moves with harmonic motion around the equilibrium point in three planes (L, H, V). The feedback copes with the forcing excitation by producing damping correction for each individual bunch. This is possible managing every single bunch by a dedicated processing channel in real time. For FCC-ee the very high number of stored bunches re-quires much more power in terms of processing capa-bility for the feedback systems. Ring length (100 Km) and very low fractional tunes must be also considered requiring for a more effective strategy in the feedback system design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH9  
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THS2H4 SRF Working Group Summary cavity, ion, HOM, SRF 223
 
  • R.A. Rimmer
    JLab, Newport News, Virginia, USA
  
  Summary of Superconducting RF: This working group focused on the status and challenges of superconducting Radio Frequency (SRF) cavities and systems for present and future high luminosity lepton colliders, the so-called 'factories'. Submissions covered the state of the art of SRF cavity designs, HOM damping, high power couplers, operational experiences and the needs of future colliders. Active work on similar SRF systems for the electron complex of a future electron ion collider (EIC) was presented. Much of this technology is also useful for next generation high brightness light sources and other applications.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-THS2H4  
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