| Paper | Title | Other Keywords | Page |
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| MOXBA01 | Challenges for Circular e+e− Colliders | collider, operation, luminosity, positron | 7 |
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Funding: This work was supported by the European Commission under the HORIZON 2020 project ARIES no.~730871. This paper sketches the glorious past and the tantalizing future of circular e+e− colliders, highlighting some of the key issues. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-MOXBA01 | ||
| About • | paper received ※ 13 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| MOYBA01 | Round Colliding Beams at Vepp-2000 with Extreme Tuneshifts | luminosity, collider, positron, emittance | 34 |
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| VEPP-2000 is the only electron-positron collider operating with round beams that allow to enhance beam-beam limit. VEPP-2000 with SND and CMD-3 detectors carried out two successful data-taking runs after new BINP injection complex was commissioned. The 2016/2017 run was dedicated to high energy range (640-1000 MeV per beam) while the 2017/2018 run was focused at 275-600 MeV/beam energies. With sufficient positron production rate and upgraded full-energy booster the collider luminosity was limited by beam-beam effects, namely flip-flop effect. Thorough machine tuning together with new ideas introduced to suppress flip-flop allowed to achieve high beam-beam tuneshift and bunch-by-bunch luminosity values at specific beam energies. The achieved luminosity increased 2-5 times in a whole energy range in comparison to phase-1 operation (2010-2013). | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-MOYBA01 | ||
| About • | paper received ※ 11 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUOBB03 | Progress of Preliminary Work for the Accelerators of a 2-7GeV Super Tau Charm Facility at China | collider, factory, positron, luminosity | 76 |
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Funding: Work supported by National Natural Science Foundation of China U1832169 and the Fundamental Research Funds for the Central Univer-sities, Grant No WK2310000046 As the most successful tau-charm factory of the world, BEPC II will celebrate its 10th birthday this year and will finish its historical mission in the next decade. Because of its very important role in high energy phys-ics study, BEPC II will certainly need a successor, a new tau-charm collider. This paper discusses the feasi-bility of a greenfield next generation tau-charm collid-er named HIEPA. The luminosity of this successor is about 5×1034 cm−2s−1 pilot and 1×1035cm-2s−1 nominal, with the electron beam longitudinally polarized at the IP. The general scheme of the accelerators and the beam parameters are shown. Several key technologies such as beam polarization and beam emittance diag-nostics are also discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOBB03 | ||
| About • | paper received ※ 16 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYAA01 | High Currents Effects in DAΦNE | vacuum, impedance, feedback, cavity | 82 |
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| DAΦNE, the Italian lepton collider, operates routinely with high intensity electron and positron colliding beams. The high current multi-bunch beams are stored in two independent rings, each of them 97 m long, and are distributed in 100 ’ 110 contiguous buckets out of the 120 available, spaced by only 2.7 ns. Since its construction, DAΦNE has been operated in different configurations which, overall, allowed to store current up to 1.4 A and 2.45 A in the positron and in the electron beam respectively. Still today DAΦNE holds the record for the highest electron beam current ever stored in particle factories and modern synchrotron radiation sources. The DAΦNE experience in terms of beam dynamics optimization aimed at achieving the high intensity beams is presented, with special emphasis on the e-cloud related issues, which represent the dominant effect limiting the positron beam current. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYAA01 | ||
| About • | paper received ※ 24 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYAA03 | Impedances and Collective Effects for JLEIC | impedance, cavity, dipole, proton | 90 |
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Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. JLEIC is the high luminosity and high polarization electron-ion collider (EIC) currently under design at Jefferson Lab. Its luminosity performance relies on the beam stability under high-intensity electron and ion beam operation. The impedance budget analysis and the estimations of beam instabilities are currently underway. In this paper, we present the update status of our back-of-envelope estimations for these collective instabilities, and identify area or parameter regimes where special attentions for instability mitigations are required. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYAA03 | ||
| About • | paper received ※ 22 October 2018 paper accepted ※ 08 March 2019 issue date ※ 21 April 2019 | ||
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| TUYAA04 | Study to Mitigate Electron Cloud Effect in SuperKEKB | MMI, photon, simulation, 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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| TUPAB02 | Low Emittance Beam Transport for e−/e+ LINAC | emittance, linac, positron, gun | 126 |
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| Design luminosity of SuperKEKB is 8 x 1035 cm-2s-1, which is 40 times higher than that of KEKB achieved. To achieve the design luminosity, the beam have to be transported to the SuperKEKB main ring with the high bunch charge (4 nC) and low emittance: 40/20 um for horizontal/vertical electron beam emittance and 100/15 um for positron beam emittance in Phase 3 final. In the LINAC and the beam transport line, the emittance growth is mainly induced by residual dispersion, beam phase space jitter, wakefield in acceleration structure, and radiation excitation. In the Phase 2 operation, we have evaluated and, if possible, corrected these effects on the emittance. Results of the emittance measurement is described. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUPAB02 | ||
| About • | paper received ※ 19 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUPAB04 | Overall Design of the CEPC Injector LINAC | linac, positron, emittance, damping | 139 |
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| The CEPC injector consists of linac and booster. To meet the requirement of the booster, the linac should provide 10 GeV electron and positron beam at a repetition frequency of 100 Hz. In this paper, the overall design of the linac has introduced. For the linac one-bunch-per-pulse is adopted and bunch charge should be larger than 3 nC in the design. A 1.1 GeV damping ring with 75.4 m circumference has adopted to reduce the transverse emittance of positron beam to suitably small value. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUPAB04 | ||
| About • | paper received ※ 26 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUPBB03 | Performance of the FCC-ee Polarimeter | laser, photon, polarization, scattering | 157 |
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| Inverse Compton scattering is the classical way to measure the electron beam polarization. Eligibility of the approach at high energy domain has been demonstrated by LEP, HERA and SLD experiments. Fast measurement of beam polarization allows to apply the resonant depolarization technique for precise beam energy determination. The distinctive feature of the FCC-ee polarimeter is the registration of scattered electrons along with scattered photons. Polarimeter is designed to measure the transverse polarization of the non-colliding pilot bunch with 1 % accuracy every second. Furthermore the same apparatus allows to measure the beam energy, longitudinal beam polarization (if any) and transverse beam positions/sizes at the place of installation. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUPBB03 | ||
| About • | paper received ※ 18 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEXAA02 | Polarization Issues at CEPC | polarization, resonance, wiggler, booster | 182 |
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| We study a possibility of obtaining transversely polarized electron-positron beams at the CEPC collider. At the beam energy of 45 GeV, this requires the use of the special wigglers to speed up the radiative self-polarization process. A numerical estimation of the depolarizing effect of the collider field errors is made, taking into account the modulation of the spin precession frequency by synchrotron oscillations. In addition, we consider an alternative possibility of obtaining polarization by accelerating the polarized particles in the booster and then injecting them into the main ring. This option saves time spent on the polarization process, and is also crucial for obtaining longitudinal polarization. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEXAA02 | ||
| About • | paper received ※ 19 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEXBA04 | Early Commissioning of the Luminosity Dither System for SuperKEKB | luminosity, feedback, controls, MMI | 212 |
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| SuperKEKB is an electron-positron double ring collider at KEK which aims at a peak luminosity of 8 x 1035 cm-2s-1 by using what is known as the ’nano-beam’ scheme. A luminosity dither system is employed for collision orbit feedback in the horizontal plane. This paper reports a system layout of the dither system and algorithm tests during the SuperKEKB Phase 2 commissioning. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEXBA04 | ||
| About • | paper received ※ 15 October 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, collider, simulation, 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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