| Paper | Title | Other Keywords | Page |
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| TUOAB01 | Dynamic Aperture Limitation Due to the Synchrotron Radiation from Quadrupole Magnets in very High Energy Colliders | synchrotron, radiation, quadrupole, betatron | 46 |
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| In a lepton storage ring of very high energy (e.g. in the e+e- Higgs factory) synchrotron radiation from quadrupoles constraints transverse dynamic aperture even in the absence of any magnetic nonlinearities. This was observed in LEP and the Future Circular e+e- Collider (FCC-ee). Synchrotron radiation in the quadrupoles modulates the particle energy at the double betatron frequency. Energy modulation varies transverse focusing strength at the same frequency and creates a parametric resonance of the betatron oscillations. Starting from 6d equations of motion we derive and solve the relevant differential equation describing the resonance, and show good agreement between analytical results and numerical simulation. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOAB01 | ||
| About • | paper received ※ 11 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUYBA02 | Beam-beam Effects at High Energy e+e− Colliders | luminosity, betatron, ECR, collider | 106 |
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Funding: Russian Science Foundation, project N14-50-00080. One of the main requirements for future e+e− colliders is high luminosity. If the energy per beam does not exceed 200 GeV, the optimal choice will be a circular collider with "crab waist" collision scheme. Here, to achieve maximum luminosity, the beams should have a very high density at the IP. For this reason, radiation in the field of a counter bunch (BS - beamstrahlung) becomes an appreciable factor affecting the dynamics of particles. In particular, in the simulation for FCC-ee, new phenomena were discovered: 3D flip-flop and coherent X-Z instability. The first is directly related to BS. The second can manifest itself at low energy (where BS is negligible), but at high energies BS substantially changes the picture. In the example of FCC-ee, we will consider the features of beam-beam interaction at high-energy crab waist colliders, and optimization of parameters for high luminosity. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA02 | ||
| About • | paper received ※ 19 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| TUPBB04 | Resonant Depolarization at Z and W at FCC-ee | synchrotron, polarization, ECR, collider | 165 |
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| Both future 100 km in circumference electron-positron colliders CEPC and FCC-ee need know beams energies with the extreme precision of 1-2 ppm. This can be done only with the help of Resonant Depolarization (RD) technique. Still, some beam parameters of these machines, like energy spread and damping decrements, are so high near 80 GeV per beam, that it is required special consideration and tricks to overcome the difficulties. The author has written simple spin tracking code, which simulates main features of the RD process in presence of continuous energy diffusion due to synchrotron radiation fluctuations. It was shown by this study, that the applicability of the RD method is limited by the effect of widening of a width of the central peak of the spin precession spectrum when the synchrotron tune is chosen too low, say below 0.05. In this case spin precession lost its resonant nature due to overlap of the wide central spectrum peak with nearby synchrotron side bands. Dependencies of the spectrum peaks width from various beam parameters and a new RD-procedure recipe are presented. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUPBB04 | ||
| About • | paper received ※ 12 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEXAA01 | High Precision Experiments in the J/psi, Psi(2S) and Tau Sector | polarization, scattering, detector, storage-ring | 179 |
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| High precision experiments in charmonium sector require beam energy calibration. VEPP-4M storage ring with energy measurement by resonant depolarization (RD) method provided high precision mass measurement of J/ψ- and ψ(2S)- mesons with KEDR detector with accuracy 2×10-6. This narrow resonances can be used for calibration of energy scale of other accelerators such as BEPC-II or future Super Charm-Tau Factories equipped with Compton backscattering (CBS) energy measurement system. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-WEXAA01 | ||
| About • | paper received ※ 12 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 | ||
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| WEXAA02 | Polarization Issues at CEPC | polarization, wiggler, booster, electron | 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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| WEXBA03 | Beam Blowup due to Lattice Coupling/Dispersion with/without Beam-beam | emittance, lattice, synchrotron, coupling | 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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