01 Circular and Linear Colliders
A24 Accelerators and Storage Rings, Other
Paper Title Page
MOPMF002 Pre-Booster Ring Considerations for the FCC e+e Injector 83
SUSPF004   use link to see paper's listing under its alternate paper code

• O. Etisken
Ankara University, Faculty of Sciences, Ankara, Turkey
• F. Antoniou, Y. Papaphilippou
CERN, Geneva, Switzerland
• A.K. Çiftçi
Izmir University of Economics, Balçova/Izmir, Turkey

The FCC-e+e injector complex needs to produce and to transport a high-intensity e+/e beam at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: using the existing SPS and a completely new ring. The purpose of this paper is to explore the needs and parameters of the existing SPS and the conceptual design of an alternative accelerator ring with injection and extraction energies of 6 and 20 GeV, respectively. In this study, the basic parameters of both choices are established, including the optics design and layout updates. Consideration for non-linear dynamics optimization and the impact of intra beam scattering are also presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF002
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MOPMF004 Spin Dynamics in the JLEIC Alternative Pre-Booster Ring 87

• J.L. Martinez Marin, B. Mustapha
ANL, Argonne, USA

In order to reduce the foot-print of the JLEIC ion complex, we have designed a more compact and cost-effective octagonal 3-GeV pre-booster ring half the size of the orig-inal figure-8 design. However, this new ring does not preserve ion polarization by design as the figure-8 shape, making it necessary to study the spin dynamics to find the best solution for spin correction. Different codes, Zgoubi and COSY, are used to model and simu-late the spin dynamics in the octagonal 3 GeV ring, in-cluding spin correction with Siberian snakes.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF004
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MOPMF018 Numerical Simulation of Spin Dynamics with Spin Flipper in RHIC 118

• P. Adams, H. Huang, J. Kewisch, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Spin flipper experiments during RHIC Run 17 were performed to study its effectiveness as a method for polarization sign reversal during stores. Numerical simulations are reported here, which were performed in accompaniment of these, and are being pursued with the aim of accurately reproducing the experimental conditions and providing thorough insight in the role of various key parameters participating in the dynamics of the spin flip, such as the sweep rate of the AC dipole, chromatic orbit control at RHIC snakes, RF parameters, possible effects of non-linear spin resonances, mirror resonance, tolerance on flipper magnet parameters, etc. The ultimate goal is for these simulations to serve as a guidance toward perfect flip to allow routine use during physics Runs.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF018
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MOPMF021 Ground Motion Measurement and Analysis for HEPS 125

• F. Yan, Z. Duan, D. Ji, Y. Jiao, Z.Z. Wang, Y. Wei, G. Xu
IHEP, Beijing, People's Republic of China

HEPS have very challenging beam stability require-ments. Special cares are mandatory in developing site vibration specifications, stable building design concepts, and passive and active ways to minimize effects on the stability of the photon beam and critical accelerator and beamline components caused by ambient ground motion sources. However, among all these work, reasonable as-sessment of the vibration induced beam instability has to be the first step. This paper will focuses on the measure-ment results of the ground motion on HEPS site, the es-tablishment of reasonable beam dynamic models, the influences of ground motion to the beam of main ring.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF021
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MOPMF028 A Superconvergent Algorithm for Invariant Spin Field Stroboscopic Calculations 145

• D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: National Science Foundation and the Department of Energy
Stroboscopic averaging can be used to calculate the invariant spin field \bfn for particles with a finite oscillation amplitude in phase space. The standard technique starts with making a guess for \bfn(\bfr), which is a function of the phase space position \bfr. By tracking a particle's orbital position forward in time and then projecting the guessed \bfn backwards to the starting phase space point, the average of the backward projected spins will converge to the invariant spin direction linearly as 1/N where N is the number of turns tracked. The convergence can be accelerated by an iterative method that uses an approximate invariant spin field constructed by averaging the calculated spin field over points that are close in orbital phase space. This superconvergent algorithm has been built into a new program based upon the Bmad toolkit for charged particle and X-ray simulations.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF028
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MOPMF039 First Xenon-Xenon Collisions in the LHC 180

• M. Schaumann, R. Alemany-Fernández, P. Baudrenghien, T. Bohl, C. Bracco, R. Bruce, N. Fuster-Martínez, M.A. Jebramcik, J.M. Jowett, T. Mertens, D. Mirarchi, S. Redaelli, B. Salvachua, M. Solfaroli, H. Timko, J. Wenninger
CERN, Geneva, Switzerland

In 2017, the CERN accelerator complex once again demonstrated its flexibility by producing beams of a new ion species, xenon, that were successfully injected into LHC. On 12 October, collisions of fully stripped xenon nuclei were recorded for the first time in the LHC at a centre-of-mass energy per colliding nucleon pair of 5.44 TeV. Physics data taking started 9.5 h after the first injection of xenon beams and lasted a total of 6 h. The integrated luminosity delivered to the four LHC experiments was sufficient that new physics results can be expected soon. We provide a general overview of this Xe-Xe pilot run before focussing on beam data at injection energy and at flat-top.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF039
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MOPMF059 Status of the FCC-ee Top-Up Booster Synchrotron 250

• B. Härer, B.J. Holzer, Y. Papaphilippou, T. Tydecks
CERN, Geneva, Switzerland

This contribution presents the status of the top-up booster synchrotron for the FCC electron-positron collider FCC-ee, which is a 100 km electron-positron collider being designed for precision studies and rare decay observations in the range of 90 to 365 GeV centre-of-mass energy. In order to keep the luminosity at a level of the order of 1035 cm-2s-1 continuous top-up injection is required, because of the short beam lifetime of less than one hour. The top-up booster synchrotron will be housed in the same tunnel as the collider rings and will ramp up the beam energy from 20 GeV at injection to the full energy between 45.5 GeV and 182.5 GeV depending on operation mode. The lattice design and two possible optics will be presented. The dynamic aperture was investigated for different sextupole schemes with and without misalignments of the lattice components. In addition, wigglers were installed to decrease the damping time and mitigate intra-beam-scattering.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF059
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MOPMK017 Transient Beam Loading Due to the Bunch Train Gap and Its Compensation Experiments at BEPC-II and ALS 390

• H. Wang, R.A. Rimmer, S. Wang
JLab, Newport News, Virginia, USA
• J.P. Dai, Q. Qin, J. Xing, J.H. Yue, Y. Zhang
IHEP, Beijing, People's Republic of China
• D. Teytelman
Dimtel, San Jose, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Non-uniform bunch fill patterns in storage rings, driven by the need to provide gaps for beam aborting and ion clearing cause a large beam loading change in the RF cavities. The induced turn-periodic transient in the cavity voltage modulates longitudinal beam properties along the train, such as synchronous position and bunch length. In the EIC design, due to the asymmetric bunch train structure between the electron and the ion beam, such modulation results in shifting collision point and leads to reduced luminosity. We have carried out the beam based experiments at BEPC-II and ALS using bunch-by-bunch diagnostic capabilities of the coupled-bunch feedback systems to study this transient effect. A modulated bunch filling pattern with higher charge density around the gap has been demonstrated to be effective in partially compensating this transient modulation. Details of the experimental setups and the data analysis will be presented to this conference.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK017
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