| Paper | Title | Other Keywords | Page |
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| MOXAA02 | Highlights from SuperKEKB Commissioning | luminosity, MMI, optics, detector | 1 |
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| SuperKEKB is an electron-positron double-ring asymmetric-energy collider to search new physics phenomena appeared in B-boson decays. In order to accomplish this purpose, the huge statics, it is necessary for 40 times the luminosity as high as the predecessor KEKB collider. The strategy is that the vertical beta function at the IP is squeezed down to 1/20 and the beam currents doubles those of KEKB while keeping the same beam-beam parameter. The vertical beta function at the IP will be much smaller than the bunch length, however, the hourglass effect which degrades the luminosity will be reduced by adopting a novel ‘‘nano-beam’ scheme. First of all, the Phase 2 commissioning was focused on the verification of nano-beam scheme. Secondary, beam related background at the Belle II detector was also studied for the preparation of the pixel vertex detector installed before the Phase 3 operation. The preliminary results and accomplishments of the commissioning in Phase 2 will be reported in this article. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-MOXAA02 | ||
| About • | paper received ※ 12 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUOAB02 | Low-emittance Tuning for Circular Colliders | emittance, sextupole, quadrupole, alignment | 57 |
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| The 100 km FCC-ee e+/e− circular collider requires luminosities in the order of 1035 cm-2 s-1 and very low emittances of 0.27 nm·prad for the horizontal plane and 1 pm·prad in the vertical. In order to reach these requirements, extreme focusing of the beam is needed in the interaction regions, leading to a vertical beta function of 0.8 mm at the IP. These challenges make the FCC-ee design particularly susceptible to misalignment and field errors. This paper describes the tolerance of the machine to magnet alignment errors and the effectiveness of optics and orbit correction methods that were implemented in order to bring the vertical dispersion to acceptable values, which in turn limits the vertical emittance. Thousands of misalignment and error seeds were introduced in MADX simulations and a comprehensive correction strategy, which includes macros based upon Dispersion Free Steering (DFS), linear coupling correction based on Resonant Driving Terms (RDTs) and response matrices, was implemented. The results are summarized in this paper. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOAB02 | ||
| About • | paper received ※ 11 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUOAB04 | Optics Corrections including IP Local Coupling at SuperKEKB | luminosity, MMI, optics, operation | 63 |
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| The phase-2 commissioning of the SuperKEKB accelerator with the interaction point(IP) has been performed from March 19 to July 17. In the collision operation during this commissioning, the vertical beta function at the IP was squeezed down to 3mm. In order to achieve such low beta collision operation, many optics corrections were performed. We present the result of those optics measurement and correction. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOAB04 | ||
| About • | paper received ※ 12 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUOBB01 | Optics Aberration at IP and Beam-beam Effects | luminosity, emittance, MMI, optics | 66 |
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| Collision in SuperKEKB phase II commissioning has started in April 2018. Luminosity was lower than the geomterical value even in very low bunch current. Linear x-y coupling at IP caused by skew of QCS was conjectured as error source. x-y coupling correction using skew corrector of QCS resulted in luminosity recover of 2 times. After the QCS skew correction, luminosity is still limited at relatively low bunch current. Nonlinear x-y coupling at IP is conjectured as a source of the luminosity limitation. We discuss effects of linear and nonlinear x-y coupling at IP on the beam-beam performance. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOBB01 | ||
| About • | paper received ※ 25 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUOBB02 | Off-momentum Optics at SuperKEKB | sextupole, lattice, optics, dynamic-aperture | 71 |
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| The nano-beam scheme can squeeze the vertical beta function at the IP much smaller than the bunch length. It implies that the large chromaticity is generated in the vicinity of the final focus quadrupole magnets and the strong sextupoles are adopted to correct the chromaticity, for instance the local chromaticity corrections. While understanding of the off-momentum optics is important to optimize the dynamic aperture to make Touschek lifetime long and to reduce the luminosity degradation due to chromatic behaviors. In general, there is a discrepancy between measurements and those obtained from the optics model. The chromatic phase-advance is introduced to measure the off-momentum optics and correct by using sextupole magnets. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOBB02 | ||
| About • | paper received ※ 12 October 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, lattice, sextupole, simulation | 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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| WEXBA03 | Beam Blowup due to Lattice Coupling/Dispersion with/without Beam-beam | emittance, resonance, lattice, synchrotron | 207 |
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Funding: Work supported by JSPS KAKENHI Grant Number 17K05475. Also supported by the European Commission under project EuCARD–2, grant agreement 312453, and under the Horizon 2020, grant agreement 654166. A significant blowup of the vertical emittance is observed in particle tracking in lattices with random skew quadrupoles, even without beam-beam effects with the FCC-ee lattice at ttbar. A Vlasov model well explains the blowup, and agrees with the tracking. This effect will set an additional limit on the goal of tuning of the vertical emittance of the lattice of colliders, well below the value at the collision. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEXBA03 | ||
| About • | paper received ※ 25 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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