| Paper | Title | Other Keywords | Page |
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| TUYAA04 | Study to Mitigate Electron Cloud Effect in SuperKEKB | electron, MMI, photon, solenoid | 95 |
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| During Phase-1 commissioning of the SuperKEKB from February to June 2016, electron cloud effects (ECE) were observed in the positron ring. The electron clouds were considered to exist in the beam pipes in the drift spaces of the ring, where the beam pipes have antechambers and titanium nitride (TiN) coating as countermeasures against ECE. Following this, permanent magnets and solenoids were attached to the beam pipes as additional countermeasures. Consequently, during Phase-2 commissioning from March to July 2018, experiments showed that the threshold beam current for exciting ECE increased by a factor of at least two relative to that during Phase-1 commissioning. While the countermeasures were strengthened, the effectiveness of the antechambers and TiN film coating was re-evaluated. From various simulations and experiments during Phase-2 commissioning, the antechamber was found to be less effective than expected with regard to reducing the number of photoelectrons in the beam channel. The TiN film coating, on the other hand, was considered to have a low secondary electron yield as expected. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYAA04 | ||
| About • | paper received ※ 27 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYBA01 | Benchmarking of Simulations of Coherent Beam-beam Instability | MMI, experiment, luminosity, synchrotron | 103 |
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| Coherent beam-beam nstability in head-tail mode has been predicted in collision with a large crossing angle. The instability is serious for design of future e+e− colliders based on the large crossing angle collision. It is possible to observe the instability in SuperKEKB commissioning. Horizontal beam size blow-up of both beams has been seen depending on the tune operating point. We report the measurement results of the instability in SuperKEKB phaseII commissioning. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA01 | ||
| About • | paper received ※ 25 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYBA03 | Beam-beam Blowup in the Presence of x-y Coupling Sources for FCC-ee | emittance, coupling, lattice, sextupole | 112 |
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| 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 fulfill 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. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA03 | ||
| About • | paper received ※ 11 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYBA04 | Some Issues on Beam-beam Interaction at CEPC | impedance, luminosity, dynamic-aperture, factory | 116 |
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Funding: Project 11775238 supported by NSFC In this paper, the beam-beam study in CEPC CDR is briefly introduced. Some issues related with beam-beam interaction will be emphasized. The bunch lengthening due to impedance and beamstrahlung is simulated in a more self-consistent method. It is found that there exist very narrow stable working point space at W-mode during the CDR design study. We’ll show wider tune scan result. It is found that there exist some disagreement between dynamic aperture and beam lifetime. We try to define the so-called diffusion rate map to explain the cause. Some initial result for different lattice solution is shown. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA04 | ||
| About • | paper received ※ 26 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEXBA02 | Machine Detector Interface for the e+e− Future Circular Collider | detector, background, luminosity, photon | 201 |
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| The international Future Circular Collider (FCC) study~[fccweb] aims at a design of p-p, \rm e+e-, e-p colliders to be built in a new 100~km tunnel in the Geneva region. The \rm e+e- collider (FCC-ee) has a centre of mass energy range between 90 (Z-pole) and 375~GeV (t\bar{t}). To reach such unprecedented energies and luminosities, the design of the interaction region is crucial. The crab-waist collision scheme~[ref:cw] has been chosen for the design and it will be compatible with all beam energies. In this paper we will describe the machine detector interface layout including the solenoid compensation scheme. We will describe how this layout fulfills all the requirements set by the parameters table and by the physical constraints. We will summarize the studies of the impact of the synchrotron radiation, the analysis of trapped modes and of the backgrounds induced by single beam and luminosity effects giving an estimate of the losses in the interaction region and in the detector. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEXBA02 | ||
| About • | paper received ※ 03 November 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEOAB04 | Single Bunch Instabilities and NEG Coating for FCC-ee | impedance, electron, collider, vacuum | 234 |
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| The high luminosity electron-positron collider FCC-ee is part of the Future Circular Collider (FCC) study at CERN and it has been designed to cover the beam energy range from 45.6 GeV to 182.5 GeV to study the properties of the Higgs boson and other particles. Electron cloud build up simulations on the Z resonance revealed the necessity of minimising the Secondary Electron Yield (SEY) of the pipe walls by applying a Ti-Zr-V Non-Evaporable Getter (NEG) coating in the entire ring. Beam dynamics simulations at 45.6 GeV pointed out that minimising the thickness of this layer is mandatory to reduce the resistive wall (RW) impedance, thus increasing the single bunch instability thresholds and ensuring beam stability during operation. However, reducing the coating thickness can affect the performance of the material and therefore the SEY. For this reason, an extensive measurement campaign was performed at CERN to characterise NEG thin films with thicknesses below 250 nm in terms of activation performance and SEY measurements. This paper also presents the FCC-ee longitudinal impedance model which includes all the current machine components. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEOAB04 | ||
| About • | paper received ※ 12 November 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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