Keyword: damping
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MOZZPLS2 Positron Driven Muon Source for a Muon Collider: Recent Developments target, emittance, collider, positron 49

• M.E. Biagini, M. Antonelli, O.R. Blanco-García, M. Boscolo, A. Ciarma, A. Giribono, S. Guiducci, C. Vaccarezza, A. Variola
INFN/LNF, Frascati, Italy
• A. Bacci
INFN-Milano, Milano, Italy
• M. Bauce, F. Collamati
INFN-Roma1, Rome, Italy
• G. Cesarini
INFN-Roma, Roma, Italy
• I. Chaikovska, R. Chehab
LAL, Orsay, France
• S.M. Liuzzo, P. Raimondi
ESRF, Grenoble, France
• D. Lucchesi
• N. Pastrone
INFN-Torino, Torino, Italy

The design of a future multi-TeV muon collider needs new ideas to overcome the technological challenges related to muon production, cooling, accumulation and acceleration. The Low Emittance Muon Accelerator (LEMMA) concept *,** presents in this paper an upgraded layout of a positron driven muon source. The positron beam, stored in a ring with high energy acceptance and low emittance, is extracted and driven in a push-pull configuration to a multi-target system, to produce muon pairs at threshold on the target’s electrons. This solution alleviates the issues related to the power deposited and the integrated Peak Energy Density Deposition on the targets. Muons produced in the multi-target system will then be accumulated in many parallel rings before acceleration and injection in the collider. A special multi-target line lattice has been designed to cope with the focusing of both the positron and muon beams. Studies on the number, material and thickness of the targets have been carried out. A general layout of the overall scheme and a description is presented, as well as plans for future R&D.
* M. Antonelli, P. Raimondi, INFN-13-22/LNF, 2013
** M. Boscolo, M. Antonelli, O.R. Blanco-Garcia, S. Guiducci, S. Liuzzo, P. Raimondi, F. Collamati, Phys. Rev. Accel. Beams, vol. 21, p. 061005, 2018

Slides MOZZPLS2 [4.360 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLS2
About • paper received ※ 14 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPGW070 Longitudinal Stability of the Hollow Ion Bunches After Momentum Slip-Stacking in the CERN SPS simulation, emittance, synchrotron, proton 254

• T. Argyropoulos, A. Lasheen, D. Quartullo, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Momentum slip-stacking is planned to be used for the lead ion beams in the CERN SPS to double the beam intensity for the High-Luminosity LHC project. During this RF manipulation two SPS batches, controlled by two independent RF systems, are going to be interleaved on an intermediate energy plateau, reducing the bunch spacing from 100 to 50 ns. However, there are limitations how close the frequencies of two RF systems can approach each other, resulting in a hole in the longitudinal bunch particle distribution due to the offset in energy of the recaptured bunches. After filamentation, these bunches should be further accelerated to the SPS top energy, before extraction to the LHC. Macro-particle simulations have shown that Landau damping is lost for the bunches with the smallest longitudinal emittances in the batch, causing un-damped oscillations of the bunch core after recapture. The standard application of an additional, fourth harmonic RF system, successfully used in proton operation, was not able to damp the oscillations at top energy, while it was necessary to switch it on from the moment of recapture. In this paper the longitudinal stability of the bunches after slip-stacking is studied in more details both by macro-particle simulations and analytical calculations.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW070
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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MOPGW076 Verification by RF Measurements of New HOM Mitigation Scheme Developed for Future SPS 33-Cell Accelerating Structures HOM, simulation, impedance, coupling 274

• P. Kramer, A. Farricker, C. Vollinger
CERN, Geneva, Switzerland

Longitudinal higher-order modes (HOMs) at a frequency of around 630 MHz in the 200 MHz travelling wave RF structures currently limit the beam intensities in the CERN SPS to less than that required by the High Luminosity (HL-) LHC. In the framework of the LHC Injectors Upgrade (LIU) project, the performance of the already existing HOM damping scheme for these standing wave modes must be improved. This involves improving the existing HOM-couplers as well as the possible use of a new mitigation technique via the insertion of resonant posts in some cells of the multi-cell structures. The development of the new damping scheme has been performed using theoretical analysis of the cavity-coupler interaction in conjunction with full-wave electromagnetic (EM) field simulations. This contribution will show the verification of the improved HOM damping performance by measurements on a single section with 11 cells and on the future 33-cell structures. The parasitic impact of the damping scheme on the travelling wave fundamental passband (FPB) will also be presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW076
About • paper received ※ 11 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPGW078 Change of Beam Distribution Due to Decoherence in the Presence of Transverse Feedback feedback, simulation, octupole, emittance 281

• S.V. Furuseth, X. Buffat
CERN, Geneva, Switzerland
• S.V. Furuseth
EPFL, Lausanne, Switzerland

The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW078
About • paper received ※ 08 April 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019
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MOPGW100 Bypass Design for Testing Optical Stochastic Cooling at the Cornell Electron Storage Ring (CESR) optics, sextupole, radiation, wiggler 360

• W.F. Bergan, M.B. Andorf, M.P. Ehrlichman, V. Khachatryan, D. L. Rubin, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF-1734189 DGE-1650441
Optical Stochastic Cooling (OSC) is a promising method for cooling very dense stored particle beams through the interference of radiation created in an upstream ’pickup’ wiggler and a downstream ’kicker’ wiggler. By correlating a particle’s path length via a bypass between the two wigglers with its betatron coordinates in the pickup, the particle will receive a kick in energy which, through coupling introduced by non-zero horizontal dispersion in the kicker, can reduce its betatron amplitude, thus cooling the beam. A proof-of-principle test of this technique is being planned at the Cornell Electron Storage Ring (CESR). In addition to maintaining standard requirements such as a large dynamic aperture and acceptable lattice functions throughout the ring, the design of the bypass is guided by the mutually competing goals of maximizing the cooling rate while maintaining a sufficiently large cooling acceptance with properly-corrected nonlinearities. We present a design of such a bypass and ring optics so as to best achieve these objectives.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW100
About • paper received ※ 14 May 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019
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MOPGW104 Equilibria and Synchrotron Stability in Two Energy Storage Rings electron, storage-ring, simulation, focusing 364

• B. Dhital, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
• J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

In a dual energy storage ring, the electron beam passes through two loops at markedly different energies EL, and EH, i.e., energies for low energy loop and high energy loop respectively. These loops use a common beamline where a superconducting linac at first accelerates the beam from EL to EH and then decelerates the beam from EH to EL in the next pass. There are two basic solutions to the equilibrium problems possible, i.e., ’Storage Ring’ (SR) equilibrium and ’Energy Recovery Linac’ (ERL) equilibrium. SR equilibrium mode more resembles the usual single loop storage ring with strong synchrotron motion and ERL equilibrium mode is the case where RF in two beam passes nearly cancels. Calculations based on linear transfer matrix formalism show that longitudinal stability exists for both SR mode and ERL mode in two energy storage rings.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW104
About • paper received ※ 14 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019
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• F. Zimmermann, D. Amorim, S. A. Antipov, S. Arsenyev, M. Benedikt, R. Bruce, M.P. Crouch, S.D. Fartoukh, M. Giovannozzi, B. Goddard, M. Hofer, J. Keintzel, R. Kersevan, V. Mertens, J. Molson, Y. Muttoni, J.A. Osborne, V. Parma, V. Raginel, S. Redaelli, T. Risselada, I. Ruehl, B. Salvant, D. Schoerling, E.N. Shaposhnikova, L.J. Tavian, E. Todesco, R. Tomás, D. Tommasini, F. Valchkova-Georgieva, V. Venturi, D. Wollmann
CERN, Geneva, Switzerland
• J.L. Abelleira, A. Abramov, E. Cruz Alaniz, H. Pikhartova, A. Seryi, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
• A. Apyan
ANSL, Yerevan, Armenia
• J. Barranco García, L. Mether, T. Pieloni, L. Rivkin, C. Tambasco
EPFL, Lausanne, Switzerland
• F. Burkart
DESY, Hamburg, Germany
• Y. Cai, Y.M. Nosochkov
SLAC, Menlo Park, California, USA
• G. Guillermo Cantón
CINVESTAV, Mérida, Mexico
• K. Ohmi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

Funding: This work was supported in part by the European Commission under the HORIZON 2020 project ARIES no.730871, and by the Swiss Accelerator Research and Technology collaboration CHART.
We present updated design parameters for a future High-Energy LHC. A more realistic turnaround time has led to a revision of the target peak luminosity, as well as a choice of a larger IP beta function, and longer physics fills. Pushed parameters of the Nb3Sn superconducting cable together with a modified layout of the 16 T dipole magnets resulted in revised field errors, updated dynamic-aperture simulations, and an associated re-evaluation of injector options. Collimators in the dispersion suppressors help achieve satisfactory cleaning performance. Longitudinal beam parameters ensure beam stability throughout the cycle. Intrabeam scattering rates and Touschek lifetime appear benign.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP037
About • paper received ※ 10 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPRB006 HOM Damping Options for the Z-Pole Operating Scenario of FCC-ee HOM, cavity, impedance, dipole 590

Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
• R. Calaga
CERN, Meyrin, Switzerland
• T. Flisgen
FBH, Berlin, Germany
• U. van Rienen
University of Rostock, Rostock, Germany

The Z-pole option of FCC-ee is an Ampere class machine with a beam current of 1.39 A. Due to high HOM power and strong HOM damping requirements, the present baseline of FCC-ee considers a single cell cavity at 400 MHz. In this paper, different HOM damping schemes are compared for the Z-pole operating scenario with the aim of lowering the parasitic longitudinal and transverse impedance. The HOM power for each damping scheme is also calculated.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB006
About • paper received ※ 15 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPRB033 Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-Research Project of HALS HOM, cavity, impedance, simulation 649

• Y.G. Tang, L. Wang, C.-F. Wu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB033
About • paper received ※ 25 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPRB090 Simulation Challenges for eRHIC Beam-Beam Study electron, proton, simulation, emittance 785

• Y. Luo, F.J. Willeke
BNL, Upton, Long Island, New York, USA
• Y. Hao
FRIB, East Lansing, USA
• J. Qiang
LBNL, Berkeley, California, USA
• Y. Roblin, H. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 2015 Nuclear Science Advisory Committee Long Rang Plan identified the need for an electron-ion collider (EIC) facility as a gluon microscope with capabilities beyond those of any existing accelerator complex. To reach the required high energy, high luminosity, and high polarization, the eRHIC design, based on the existing heavy ion and polarized proton collider RHIC, adopts a very small \beta-function at the interaction points, a high collision repetition rate, and a novel hadron cooling scheme. A full crossing angle of 22 mrad and crab cavities for both electron and proton rings are required. In this article, we will present the high priority R\&D items related to the beam-beam interaction studies for the current eRHIC design, the simulation challenges, and our plans and methods to address them. Recent progresses on this project are reported too.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB090
About • paper received ※ 14 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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MOPTS090 Beam-Based Measurement of the Skew-Sextupolar Component of the Radio Frequency Field of a HL-LHC-Type Crab-Cavity cavity, betatron, sextupole, experiment 1066

• M. Carlà, A. Alekou, H. Bartosik, L.R. Carver
CERN, Geneva, Switzerland

Two High Luminosity Large Hadron Collider (LHC) type crab-cavities have been installed in the CERN SPS for testing purposes. An attempt to characterize the skew-sextupolar component of the radio frequency field of the crab-cavity (a3) has been carried out by means of beam-based techniques using turn-by-turn monitoring of the betatron motion. The skew nature of a3 couples the horizontal and vertical betatron motions through a non-linear term. Therefore by exciting the horizontal betatron motion it was possible to observe a spectral line in the vertical beam motion driven by the non-linear coupling at the characteristic frequency 2Qx. A measurement of the magnitude of a3 was thus obtained by characterizing amplitude and phase of such line. The results of the measurements are discussed here.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS090
About • paper received ※ 06 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019
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MOPTS097 Updates on Alternative Pre-Booster Ring Design and Wiggler Magnet Considerations of SPS for the FCC e+e Injector wiggler, emittance, injection, extraction 1094

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

The Future Circular e+e Collider (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 designing a completely new ring. The purpose of this paper is to explore the needs and parameters of the existing SPS, to investigate wiggler magnet options for SPS, and provide an updated study of alternative accelerator ring design with injection and extraction energies of 6 and 20 GeV, respectively. In this study, the parameters of both choices are established, including the optics design, layout update and considerations for non-linear dynamics optimization.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS097
About • paper received ※ 06 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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TUPMP013 New Design of Vacuum Chambers for Radiation Shield Installation at Beam Injection Area of J-PARC RCS vacuum, injection, radiation, flattop 1255

• J. Kamiya, K. Kotoku, Y. Shobuda, T. Takayanagi, K. Yamamoto, T. Yanagibashi
JAEA/J-PARC, Tokai-mura, Japan
• K. Horino, N. Miki
Nippon Advanced Technology Co., Ltd., Tokai, Japan

One of the issues in the J-PARC 3 GeV rapid cycling synchrotron is the high residual radiation dose around the beam injection point. A radiation shield is necessary to reduce radiation exposure of workers when maintenance is performed there. A space to install the radiation shield should be secured by newly designing a structure of the vacuum chamber at the injection point and the alumina ceramics beam pipes for the shift bump magnets. To make the space for the shield, the chamber is lengthened along the beam line and the cross-sectional shape is changed from circle to rectangle. The displacement and inner stress of the vacuum chamber due to atmospheric pressure was evaluated to be enough small by the calculation. For the ceramics beam pipe’s rf-shield, the damping resistor was effective to reduce the induced modulation voltages by the pulsed magnetic field.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP013
About • paper received ※ 29 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019
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TUPGW042 Study of the Intra-beam Scattering Effects in the HALS Storage Ring emittance, wiggler, storage-ring, lattice 1501

• W. Li, Z.H. Bai, W. Li, D.R. Xu, T. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: This work was supported by the Fundamental Research Funds for the Central Universities (Grant No.WK2310000082 and WK2310000077).
The Hefei Advanced Light Source (HALS) is designed to be a dedicated 4th generation diffraction limited light source. In 2018, the baseline lattice of the HALS storage ring has been proposed, with an ultra-low natural emittance of about 25 pm-rad. The preliminary study of intra-beam scattering effects on the beam emittance growth in the HALS storage ring has been performed with this baseline lattice. Due to the limited synchrotron radiation in this storage ring, damping wigglers are expected in this storage ring to reduce the damping time and reduce the emittance. In this paper, we will present the simulation results of the IBS effects, estimated effectiveness of damping wiggler and the corresponding linear optics calibration of the perturbation due to insertion device, and finally the estimated Touschek lifetime will be shown.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW042
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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TUPGW052 STUDY OF THE RAMPING PROCESS FOR HEPS BOOSTER booster, storage-ring, lattice, injection 1521

• Y.M. Peng, J.Y. Li, C. Meng, H.S. Xu
IHEP, Beijing, People’s Republic of China

The High Energy Photon Source (HEPS) is a 6-GeV, ul-tralow-emittance storage ring light source to be built in Huairou District, Beijing, China. The beam energy ramps from 500 MeV to 6 GeV in 400 ms, during which the RF voltage increases accordingly to keep the momentum acceptance large enough. The booster is designed to operate at 1 Hz repetition frequency. In this paper the energy ramping curve, RF choice, beam parameters changing curves and eddy current effect in HEPS booster will be presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW052
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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TUPGW066 Exploring the Potential of the Swiss Light Source emittance, storage-ring, operation, cavity 1554

• M. Aiba, M. Böge, A. Citterio, M.M. Dehler, A. Lüdeke, C. Ozkan Loch, L. Stingelin, A. Streun
PSI, Villigen PSI, Switzerland

Swiss Light Source (SLS) has been on-line since 2001. Although its performance meets the specifications, it still has a potential to achieve better storage ring beam parameters. We explore two possible improvements. The first one is for the beam lifetime. There are 480 rf buckets while normally 390 bunches are stored. The gap in filing pattern (90 empty buckets) is held to suppress ion instability. After many years of operation, however, the vacuum condition is much better than that of the time when the SLS was turned on. Hence it is possible to shorten the gap. The beam lifetime can then be prolonged due to less bunch current while keeping the net beam current. The study may be also useful to predict possible filling patter in SLS2, which is the SLS upgrade planned. The second one is for the beam emittance. The nominal energy closed orbit coincides with the axes of quadrupole magnets. An off-momentum closed orbit is therefore off-centered through quadrupoles, resulting in a damping partition shift. The beam emittance can be decreased at the expense of a larger energy spread. This was successfully achieved in the ESRF booster. We study whether it is applicable to the SLS storage ring.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW066
About • paper received ※ 13 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019
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TUPGW082 Impedance of the Flange Joints With the RF Contact Spring in NSLS-II impedance, storage-ring, vacuum, cavity 1597

• A. Blednykh, B. Bacha, G. Bassi, C. Hetzel, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Department of Energy Contract No. DE-SC0012704
Since the beginning of the NSLS-II commissioning, temperature of the vacuum components has been moni-tored by the Resistance Temperature Detectors located predominantly outside of the vacuum enclosure and at-tached to the chamber body. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o harmonic cavities. Effect of the RF shielded flanges on local heat and on the longitu-dinal beam dynamics is discussed in details.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW082
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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TUPGW107 Overview of Collective Effects in SLS 2.0 cavity, impedance, operation, simulation 1658

• M.M. Dehler, M. Aiba, A. Citterio, L. Stingelin
PSI, Villigen PSI, Switzerland

At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 40 fold smaller emittance and a corresponding increase of the spectral brightness from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchrotron frequency. We give an overview of the latest results for the ring. Most critical is the threshold for the longitudinal single bunch instability. Taking into account the combined effect of wake impedances and CSR, we have to rely on bunch stretching by a higher harmonic system to achieve stable operation at nominal current.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW107
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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TUPRB101 Damping Trapped Modes in an in-Vacuum Undulator at a Synchrotron Radiation Light Source simulation, vacuum, HOM, impedance 1895

• K. Tian, Z. Li, A. Ringwall, J.J. Sebek
SLAC, Menlo Park, California, USA

Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
In this paper, we report the efforts in solving the problem of coupled-bunch instabilities caused by an in-vacuum undulator in the SPEAR3 storage ring. After exploring several approaches to reduce the strength of the trapped modes, we found that ferrite dampers were the most effective and simplest way for mode damping in our SPEAR3 in-vacuum undulator. The results of the first RF cold measurement on an in-vacuum undulator equipped with these ferrite dampers agree well with numerical simulations.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB101
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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WEPMP041 Damping Bunch Oscillations Due to Off-Axis Injection optics, injection, wiggler, radiation 2422

• F. Zimmermann, O. Etisken, N. Mounet, A. Oeftiger, S. Ogur, Y. Papaphilippou, B. Salvant
CERN, Geneva, Switzerland
• K. Oide
KEK, Ibaraki, Japan

Funding: This work was supported by the European Commission under the HORIZON 2020 project ARIES, grant agreement no. 730871.
In the FCC-ee pre-injector complex, a slightly modified SPS can serve as pre-booster. The baseline design foresees injecting the low-emittance electron and positron bunches off-axis into the SPS, and deploying strong wigglers to greatly enhance the radiation damping at the injection energy. We here compare the damping of large injection oscillations by means of radiation damping with the effect of other possible damping mechanisms such as a fast bunch-by-bunch feedback system and/or head-tail damping via nonzero chromaticity. As a by-product, we investigate the transverse beam stability.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP041
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019
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WEPGW064 Machine Learning Application in Bunch Longitudinal Phase Measurement network, synchrotron, SRF, injection 2625

• X.Y. Xu, Y.M. Zhou
SINAP, Shanghai, People’s Republic of China
• Y.B. Leng
SSRF, Shanghai, People’s Republic of China

High resolution bunch-by-bunch longitudinal phase measurement has been realized at Shanghai Synchrotron Radiation Facility (SSRF). In order to fully exploit the potency of the bunch phase monitor, the transient state during injection is being further studied. A longitudinal phase fitting method was used to study the synchrotron damping oscillation in injection events, where we can get the energy offsets between the injector and the storage ring, refilled bunch arrived time and the synchrotron damping time. However, manual multi-parameter fitting of nonlinear functions is awfully complex and slow. Machine learning algorithms, such as gradient descent and artificial neural network (ANN) is more suitable to do this fitting. Through these methods, we can quickly obtain more accurate fitting parameters and further realize online measurement of the refilled charge arrived time, energy offsets between the injector and storage ring, and the synchrotron damping time.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW064
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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WEPRB034 Study on the Design of the X-band Waveguide-damped Structure wakefield, GUI, HOM, simulation 2886

• X.X. Huang, W. Fang, Z.T. Zhao
SSRF, Shanghai, People’s Republic of China
• A. Grudiev
CERN, Meyrin, Switzerland

The design of waveguide-damped structure is optimized to reduce the magnitudes of surface electromagnetic fields and strongly suppress long-range transverse wakefields of the 380 GeV Compact Linear Collider facility currently under study. The optimization is mainly discussed with the elliptical shape of the iris, the wall shape of the damping waveguides, the position of the high-order-mode damping loads and the widths of the waveguide openings of the entire sequence of damping waveguides.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB034
About • paper received ※ 13 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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WEPRB043 Wakefield Suppression in the Main LINAC of the Klystron-Based First Stage of CLIC at 380 GeV wakefield, HOM, GUI, linac 2899

• J.Y. Liu, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People’s Republic of China
• A. Grudiev
CERN, Meyrin, Switzerland

An alternative klystron-based scenario for the first stage of Compact Linear Collider (CLIC) at 380 GeV centre-of-mass energy was proposed. To preserve the beam stability and luminosity of CLIC, the beam-induced transverse long-range wakefield in main linac must be suppressed to an acceptable value. The design of klystron-based accelerating structure is based on waveguide damping structure (WDS). The high-order modes (HOMs) propagating into four waveguides are absorbed by HOM damping loads. In this paper, the wakefield suppression in CLIC-K based on GdfidL code simulations are presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB043
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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WEPRB066 Utilizing the High Shunt Impedance TM020-Mode Cavity in the Double RF Systems for the Storage Ring of the Thailand New Light Source cavity, storage-ring, impedance, coupling 2972

• N. Juntong, T. Phimsen
SLRI, Nakhon Ratchasima, Thailand
• N. Chulakham, S. Malichan
Udon Thani Rajabhat University, Udon Thani, Thailand

The utilization of the TM020-mode cavity for the storage ring based light source was pioneered by SPring-8 with its high quality factor and hence its high shunt impedance. KEK-LS has also studied the possibility of using this type of cavity for their storage ring. The TM020-mode cavity has larger transverse dimension compared to the traditional TM010-mode cavity, but with its higher shunt impedance it can be designed to fit in the new low emittance storage ring regardless. The new storage ring based light source project in Thailand aims to optimum the low emittance beam in nano-meters region with the energy of 3 GeV. The TM020-mode cavity was considered as the main cavity and the harmonic cavity for the storage ring. They have been designed to have their pipe aperture fits the storage ring beam ducts. The main cavity has a high shunt impedance of 8.3 Mega Ohms with the 51,000 unloaded quality factor. The harmonic cavity has a high shunt impedance and an unloaded quality factor of 2.45 Mega Ohms and 36,000, respectively. The damping mechanism of the parasitic modes and the tuning mechanism of the operating mode of these cavities were also studied. There will be four main cavities and six harmonic cavities in the new storage ring. Detailed design and study of these cavities will be presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB066
About • paper received ※ 29 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019
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WEPRB069 Wakefield Suppression in a Manifold Damped and Detuned Structure for a 380 GeV CLIC Staged Design wakefield, dipole, accelerating-gradient, collider 2980

• N.Y. Joshi, R.M. Jones
UMAN, Manchester, United Kingdom

The first stage of the Compact Linear Collider (CLIC) project aims to collide electrons and positrons at a 380 GeV center of mass energy. In the baseline design the main linacs for this staged approach are required to achieve a gradient of 72 MeV/m, with the surface electromagnetic fields (EM) and the transverse long-range wakefields bound by beam dynamics constraints. The baseline design utilizes heavy damping in a traveling wave (TW) structure. Here we report on an alternate design, which adopts moderate damping along with strong detuning of the individual cell frequencies. In the context of this Damped and Detuned Structure (DDS) design, we study Gaussian and hyperbolic secant dipole distributions, together with interleaving of successive structures, to effect long-range transverse wakefield suppression. Both analytic and modal summation approaches, in the quasi-coupled approximation, produce consistent results. In the optimisation scheme we opt for a dipole frequency bandwidth of 17.7 % (2.92 GHz)
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB069
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019
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WEPRB077 Simulation and Measurements of HOM Filter of the LARP Prototype RF-Dipole Crabbing Cavity Using an RF Test Box HOM, cavity, dipole, luminosity 2999

• S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
• Z. Li
SLAC, Menlo Park, California, USA

The RF-Dipole Crabbing Cavity designed for the LHC High Luminosity Upgrade includes two higher order mode (HOM) couplers. One of the HOM couplers is an rf filter, which is a high pass filter designed to couple to the horizontal dipole modes and accelerating modes up to 2 GHz, while rejecting the fundamental operating mode at 400 MHz. The coupler consists of a high pass filter circuit where the rejection of the operating mode and transmission of HOMs are sensitive to dimensional deviations. An rf test box has been designed to measure the transmission of the rf filter in order to qualify the fabricated HOM coupler and to tune the coupler. This paper presents the measurements of the HOM coupler with the rf test box.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB077
About • paper received ※ 20 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019
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WEPTS044 Instability Latency in the LHC octupole, experiment, feedback, simulation 3204

• S.V. Furuseth, D. Amorim, S. A. Antipov, X. Buffat, N. Mounet, E. Métral, B. Salvant
CERN, Geneva, Switzerland
• S.V. Furuseth, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland

The Large Hadron Collider (LHC) has experienced multiple instabilities that occur between minutes and hours after the last modification of the machine settings. The existence of instabilities with high latency has been reproduced also in simulations. Dedicated experiments, injecting a controlled noise into the beam, have now been performed to discover the dependence of this latency on key parameters. The results seem compatible with a mechanism linked to a steady and slow modification of the transverse beam distribution leading to a loss of Landau damping.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS044
About • paper received ※ 30 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019
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WEPTS070 First Measurements of Nonlinear Decoherence in the IOTA Ring lattice, kicker, experiment, optics 3286

• C.C. Hall, D.L. Bruhwiler, J.P. Edelen
• N. Kuklev
University of Chicago, Chicago, Illinois, USA
• A.L. Romanov, A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: This work has been supported by the U.S. Department of Energy Office of Science, Office of High Energy Physics under Award No. DE-SC00111340
The Integrable Optics Test Accelerator (IOTA), at Fermi National Laboratory is aimed at testing nonlinear optics for the next generation of high intensity rings. Through use of a special magnetic element the ring is designed to induce a large tune spread with amplitude while maintaining integrable motion. This will allow for the suppression of instabilities in high-intensity beams without significant reduction in dynamic aperture. One important aspect of this is the nonlinear decoherence that occurs when a beam is injected off axis or receives a transverse kick while circulating in the ring. This decoherence has been studied in detail, with simulations, for protons in IOTA both with and without space-charge. However, it has yet to be demonstrated experimentally. During the first phase of the IOTA experimental program, the ring is operated with 100 MeV electrons, allowing for the study of nonlinear optics without the complications introduced by space charge. Here we present measurements taken during the IOTA commissioning, and an analysis of the results.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS070
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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THPRB036 Development of Injection and Extraction Kickers for SuperKEKB Damping Ring kicker, extraction, injection, power-supply 3890

• M. Tawada, M. Kikuchi, Y. Sakamoto, H. Someya
KEK, Ibaraki, Japan
• K. Tenjin, A. Tokuchi
Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan

SuperKEKB is a double ring asymmetric collider to study the B meson physics, which is an upgrade project of KEKB. The 7 GeV electron (HER) and the 4 GeV positron ring (LER) collides at an interaction point. The positron beam produced by linac cannot meet the dynamic aperture restrictions of LER. Damping ring (DR) is required to reduce its injection emittance. Damping ring (DR) for SuperKEKB has two kicker magnets for the injection and the extraction, respectively. These kickers are required to meet the following specifications: (1) rise and fall time does not exceed 100 ns, (2) two bunches which are 96 ns apart must be kicked by single pulse, (3) the stability of peak current for the extraction kickers must be less than 0.1 %. Kicker magnets are designed as a conventional kicker with a ferrite core. The pulse shape is a double half sine for the two bunch injection. In order to achieve short rise time, a saturable inductance is used. The design and performance of kicker magnets and the power supplies are reported.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB036
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019
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THPRB071 Beam-Based Measurements on Two ±12.5 kV Inductive Adders, together with Striplines, for CLIC Damping Ring Extraction Kickers kicker, flattop, extraction, storage-ring 3970

• J. Holma, M.J. Barnes, M. Carlà, N. Catalán Lasheras, Y. Papaphilippou
CERN, Geneva, Switzerland
• U. Iriso, Z. Martí, F. Pérez, M. Pont
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The CLIC study is investigating the technical feasibil-ity of an electron-positron linear collider with high lumi-nosity and a nominal centre-of-mass energy of 3 TeV. Pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. The DR kicker systems, each of which consists of a set of striplines and two inductive adders, must provide ex-tremely stable field pulses. The DR extraction kicker system is the most demanding: specifications require a field uniformity within ±0.01% and pulses up to 900 ns flattop duration, at ±12.5 kV and 309 A, with ripple and droop of not more than ±0.02 % (±2.5 V), with respect to a reference waveform. Two prototype inductive adders have been designed and built at CERN, and have been tested with prototype striplines installed in the storage ring of the ALBA Synchrotron Light Source, in Spain. The stability of the kicker system, including the modulators, has been evaluated from the beam-based measure-ments and is reported in this paper.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB071
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019
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THPRB073 Laboratory Measurements on Two ±12.5 kV Inductive Adders with ±0.02% Waveform Stability for CLIC Damping Ring Extraction Kickers kicker, flattop, extraction, collider 3978

• J. Holma, M.J. Barnes, A. Chmielinska
CERN, Geneva, Switzerland
• M. Pont
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The CLIC study is investigating the technical feasibil-ity of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. Pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. The DR kicker systems must provide extremely stable field pulses to avoid beam emittance increase. Each DR extrac-tion kicker system consists of a set of striplines and two pulse modulators. Specifications for this system require that the modulator produce pulses of 900 ns flattop dura-tion, ±12.5 kV and 305 A, with ripple and droop of not more than ±0.02 % (±2.5 V) with respect to a reference waveform. Inductive adder topology has been chosen for the pulse modulators. Two full-scale, 20-layer, 12.5 kV prototype inductive adders have been designed, built and tested at CERN. This paper presents the measurements of the stability of these adders for two different waveforms: a flat-top waveform and a controlled decay waveform, the latter of which is required to generate flat-top total field for the CLIC DR extraction stripline kicker.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB073
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019
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THPRB092 Reduction of Beam Induced RF-Heating in the Horizontal Stripline Kicker at the TPS kicker, impedance, storage-ring, feedback 4035

• P.J. Chou, C.K. Chan, C.-C. Chang, K.T. Hsu, K.H. Hu, C.K. Kuan, I.C. Sheng
NSRRC, Hsinchu, Taiwan

In preparation for 500 mA operation at the Taiwan Pho-ton Source (TPS), we redesigned the horizontal stripline kicker for the beam feedback system to gain a smaller loss factor with higher shunt impedance. We introduced ground fenders (see Fig. 1) to this new design which resulted in the reduction of the loss factor and substantial increase of the kicker shunt impedance. The transverse profile of the kicker electrodes was matched to the race-track beam pipe in the straight sections to minimize broadband impedance. The ground fenders can reduce the leakage of image currents through the gaps between the two strip line electrodes and also help to achieve a better impedance matching for the TEM modes in the transmission lines formed by the stripline electrodes and beam pipe in the kicker. The RF design and analysis of trapped resonant modes in the kicker were simulated by the 3-D electromagnetic code GdfidL [1]. Results of the RF design and analysis of trapped resonant modes will be discussed together with analytical estimates of coupled bunch instabilities at a beam current of 500 mA.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB092
About • paper received ※ 17 April 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019
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