WEPMW —  Poster Session   (11-May-16   16:00—18:00)

Paper	Title	Page
WEPMW001	End-to-End Beam Simulations for the New Muon G-2 Experiment at Fermilab	2408
	M. Korostelev, I.R. Bailey, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom I.R. Bailey Lancaster University, Lancaster, United Kingdom A. Herrod, A. Wolski The University of Liverpool, Liverpool, United Kingdom J.P. Morgan Fermilab, Batavia, Illinois, USA W. Morse, D. Stratakis, V. Tishchenko BNL, Upton, Long Island, New York, USA
	The aim of the new muon g-2 experiment at Fermilab is to measure the anomalous magnetic moment of the muon with an unprecedented uncertainty of 140 ppb. A beam of positive muons required for the experiment is created by pion decay. Detailed studies of the beam dynamics and spin polarization of the muons are important to predict systematic uncertainties in the experiment. In this paper, we present the results of beam simulations and spin tracking from the pion production target to the muon storage ring. The end-to-end beam simulations are developed in Bmad and include the processes of particle decay, collimation (with accurate representation of all apertures) and spin tracking.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW001
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WEPMW002	A CLIC Damping Wiggler Prototype at ANKA: Commissioning and Preparations for a Beam Dynamics Experimental Program	2412
	A. Bernhard, S. Casalbuoni, S. Gerstl, J. Gethmann, A.W. Grau, E. Huttel, A.-S. Müller, D. Saez de Jauregui, N.J. Smale KIT, Karlsruhe, Germany A.V. Bragin, S.V. Khrushchev, N.A. Mezentsev, V.A. Shkaruba, V.M. Tsukanov, K. Zolotarev BINP SB RAS, Novosibirsk, Russia P. Ferracin, L. Garcia Fajardo, Y. Papaphilippou, H. Schmickler, D. Schoerling, P. Zisopoulos CERN, Geneva, Switzerland
	Funding: This work is partially funded by the German Federal Ministry of Education and Research under grant 05K12VK1 In a collaboration between CERN, BINP and KIT a prototype of a superconducting damping wiggler for the CLIC damping rings has been installed at the ANKA synchrotron light source. On the one hand, the foreseen experimental program aims at validating the technical design of the wiggler, particularly the conduction cooling concept applied in its cryostat design, in a long-term study. On the other hand, the wiggler's influence on the beam dynamics particularly in the presence of collective effects is planned to be investigated. ANKA's low-alpha short-bunch operation mode will serve as a model system for these studies on collective effects. To simulate these effects and to make verifiable predictions an accurate model of the ANKA storage ring in low-alpha mode, including the insertion devices is under parallel development. This contribution reports on the first operational experience with the CLIC damping wiggler prototype in the ANKA storage ring and steps towards the planned advanced experimental program with this device.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW002
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WEPMW003	NONLINEAR OPTIMIZATION OF CLIC DRS NEW DESIGN WITH VARIABLE BENDS AND HIGH FIELD WIGGLERS	2416
	H. Ghasem, J. Alabau-Gonzalvo, F. Antoniou, S. Papadopouloupresenter, Y. Papaphilippou CERN, Geneva, Switzerland
	The new design of CLIC damping rings is based on longitudinal variable bends and high field superconducting wiggler magnets. It provides an ultra-low horizontal normalised emittance of 412 nm-rad at 2.86 GeV. In this paper, nonlinear beam dynamics of the new design of the damping ring (DR) with trapezium field profile bending magnets have been investigated in detail. Effects of the misalignment errors have been studied in the closed orbit and dynamic aperture.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW003
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WEPMW004	Progress in Detector Design and Installation for Measurements of Electron Cloud Trapping in Quadrupole Magnetic Fields at CesrTA	2420
	J.A. Crittenden, S. Barrett, M.G. Billing, K.A. Jones, Y. Li, T.I. O'Connell, K. Olear, S. Poprockipresenter, D. L. Rubin, J.P. Sikora Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by the US National Science Foundation PHY-1416318, PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538 Following up on our 2013 and 2014 measurements of electron cloud trapping in a quadrupole magnet with 7.4~T/m gradient in the 5.3~GeV positron storage ring at Cornell University, we have redesigned the shielded-stripline time-resolving electron detector and installed a wide-aperture quadrupole magnet at a location in the ring where its field can be compensated by a nearby quadrupole, thus allowing the first measurements of cloud trapping as a function of field gradient. The transverse acceptance of the electron detector has been tripled, allowing tests of model predictions indicating a dramatic cloud splitting effect which exhibits a threshold behavior as a function of bunch population. In addition, a vacuum chamber optimized for cloud buildup measurements using resonant microwave phenomena has been employed. We describe design considerations and modeling predictions for the upcoming 2016 data-taking run. This project is part of the CESR Test Accelerator program, which investigates performance limitations in low-emittance storage and damping rings.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW004
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WEPMW006	First Design of a Proton Collimation System for 50 TeV FCC-hh	2423
	M. Fiascaris, R. Bruce, D. Mirarchipresenter, S. Redaelli CERN, Geneva, Switzerland
	We present studies aimed at defining a first conceptual solution for a collimation system for the hadron-hadron option for the Future Circular Collider (FCC-hh). The baseline collimation layout is based on the scaling of the present LHC collimation system to the FCC-hh energy. It currently includes a dedicated betatron cleaning insertion as well as collimators in the experimental insertions to protect the inner triplets. An aperture model for the FCC-hh is defined and the geometrical acceptance is calculated at top energy taking into account mechanical and optics imperfections. Based on these studies the collimator settings needed to protect the machine are defined. The performance of the collimation system is then assessed with particle tracking simulation tools assuming a perfect machine.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW006
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WEPMW007	Validation of Off-momentum Cleaning Performance of the LHC Collimation System	2427
	B. Salvachua, P. Baudrenghien, R. Bruce, H. Garcia, P.D. Hermes, S. Jackson, M. Jaussi, A. Mereghetti, D. Mirarchipresenter, S. Redaelli, H. Timko, G. Valentino, A. Valloni CERN, Geneva, Switzerland R. Kwee-Hinzmann Royal Holloway, University of London, Surrey, United Kingdom
	The LHC collimation system is designed to provide effective cleaning against losses coming from off-momentum particles, either due to un-captured beam or to an unexpected RF frequency change. For this reason the LHC is equipped with a hierarchy of collimators in IR3: primary, secondary and absorber collimators. After every collimator alignment or change of machine configuration the off-momentum cleaning efficiency is validated with loss maps at low intensity. We describe here the improved technique used in 2015 to generate such loss maps without completely dumping the beam into the collimators. The achieved performance of the collimation system for momentum cleaning is reviewed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW007
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WEPMW008	Possible Beam Parameters in Double RF Operation of the CERN LHC	2430
	E.N. Shaposhnikova, J.F. Esteban Müller CERN, Geneva, Switzerland
	The LHC operates using a 400 MHz SC RF system. A 200 MHz NC RF system was foreseen in the LHC Design Report to improve beam capture and the bare resonators were manufactured, but never installed. Later the second harmonic RF system was proposed to cure longitudinal beam instabilities in the absence of a dedicated wideband feedback system in the LHC. For nominal intensities the longitudinal beam stability is ensured by controlled emittance blow-up during the acceleration ramp. Recently slow growing instabilities were observed at the end of long fills at 6.5 TeV as bunches shrink due to synchrotron radiation damping. For High Luminosity LHC twice higher intensities should be kept stable with new equipment installed in the ring. Additional motivations for a second RF system in the LHC have also been considered. Operation with an extra RF system is limited by the required RF configuration (phase between the two RF systems) and longitudinal beam stability. In this work requirements for the double RF systems are analyzed together with a possible range of longitudinal beam parameters.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW008
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WEPMW009	Towards a Mono-chromatization Scheme for Direct Higgs Production at FCC-ee	2434
SUPSS007	use link to see paper's listing under its alternate paper code
	M.A. Valdivia García, F. Zimmermann CERN, Geneva, Switzerland A. Faus-Golfe IFIC, Valencia, Spain
	Direct Higgs production in e+e− collisions at the FCC is of interest if the centre-of-mass energy spread can be reduced by at least an order of magnitude. A mono-chromatization scheme, to accomplish this, can be realized with horizontal dispersion of opposite sign for the two colliding beams at the interaction point (IP). We review approaches from historical mono-chromatization studies, then derive a set of IP parameters which would provide the required performance in FCC e+e− collisions at 63 GeV beam energy, compare these with the baseline optics parameters at neighbouring energies (45.6 and 80 GeV), comment on the effect of beamstrahlung, and, finally, discuss the modifications of the FCC-ee final-focus optics needed to obtain the required parameters.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW009
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WEPMW010	Effect of Beamstrahlung on Bunch Length and Emittance in Future Circular e+e− Colliders	2438
	M.A. Valdivia García, F. Zimmermann CERN, Geneva, Switzerland
	In future circular e+e− colliders, beamstrahlung may limit the beam lifetime at high energies, and increase the energy spread and bunch length at low energies. If the dispersion or slop of the dispersion is not zero at the collision point, beamstrahlung will also affect the transverse emittance. In this paper, we first examine the beamstrahlung properties, and show that for the proposed FCC-ee, the radiation is fairly well modelled by the classical formulae describing synchrotron radiation in bending magnets. We then derive a set of equations describing the equilibrium beam parameters in the presence of a nonzero dispersion at the collision point. An example case from FCC-ee will serve as an illustration.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW010
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WEPMW011	Stable Spin Direction Investigations in RHIC	2442
	F. Méot, H. Huang, N. Tsoupas 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. Beam and spin dynamics investigations are part of the preparations and studies regarding RHIC collider runs, they are part as well of the efforts dedicated to improving stored beam polarization, and in view of the eRHIC EIC project. Some recent studies and their outcomes are discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW011
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WEPMW012	Injection Optics for the JLEIC Ion Collider Ring	2445
	V.S. Morozov, Y.S. Derbenev, F. Lin, F.C. Pilat, G.H. Wei, Y. Zhangpresenter JLab, Newport News, Virginia, USA Y. Cai, Y. Nosochkov, M.K. Sullivan, M.-H. Wang SLAC, Menlo Park, California, USA
	Funding: * Work supported by the U.S. DOE Contract DE-AC02-76SF00515. ** Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required to allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW012
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WEPMW013	Bunch Splitting Simulations for the JLEIC Ion Collider Ring	2448
	B.R.P. Gamage, T. Satogatapresenter ODU, Norfolk, Virginia, USA T. Satogatapresenter JLab, Newport News, Virginia, USA
	We describe the bunch splitting strategies for the proposed JLEIC ion collider ring at Jefferson Lab. This complex requires an unprecedented 9:6832 bunch splitting, performed in several stages. We outline the problem and current results, optimized with ESME including general parameterization of 1:2 bunch splitting for JLEIC parameters.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW013
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WEPMW014	Development of the Electron Cooling Simulation Program for JLEIC	2451
	H. Zhang, J. Chen, R. Li, Y. Zhangpresenter JLab, Newport News, Virginia, USA H. Huang, L. Luo ODU, Norfolk, Virginia, USA
	Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177 In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during collision at the collider ring. A new electron cooling process simulation program has been developed to fulfill the requirements of the JLEIC electron cooler design. The new program allows the users to calculate the electron cooling rate and simulate the cooling process with either DC or bunched electron beam to cool either coasting or bunched ion beam. It has been benchmarked with BETACOOL in aspect of accuracy and efficiency. In typical electron cooling process of JLEIC, the two programs agree very well and we have seen a significant improvement of computational speed using the new one. Being adaptive to the modern multicore hardware makes it possible to further enhance the efficiency for computationally intensive problems. The new program is being actively used in the electron cooling study and cooler design for JLEIC. We will present our models and some simulation results in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW014
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WEPMW015	Evaluation and Compensation of Detector Solenoid Effects in the JLEIC	2454
	G.H. Wei, F. Lin, V.S. Morozov, F.C. Pilat, Y. Zhangpresenter JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported also by the U.S. DOE Contract DE-AC02-76SF00515. The JLEIC detector solenoid has a strong 3 T field in the IR area, and its tails extend over a range of several meters. One of the main effects of the solenoid field is coupling of the horizontal and vertical betatron motions which must be corrected in order to preserve the dynamical stability and beam spot size match at the IP. Additional effects include influence on the orbit and dispersion caused by the angle between the solenoid axis and the beam orbit. Meanwhile it affects ion polarization breaking the figure-8 spin symmetry. Crab dynamics further complicates the picture. All of these effects have to be compensated or accounted for. The proposed correction system is equivalent to the Rotating Frame Method. However, it does not involve physical rotation of elements. It provides local compensation of the solenoid effects independently for each side of the IR. It includes skew quadrupoles, dipole correctors and anti-solenoids to cancel perturbations to the orbit and linear optics. The skew quadrupoles and FFQ together generate an effect equivalent to adjustable rotation angle to do the decoupling task. Details of all of the correction systems are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW015
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WEPMW016	Towards a Small Emittance Design of the JLEIC Electron Collider Ring	2457
	F. Lin, Y.S. Derbenev, A. Hutton, V.S. Morozov, F.C. Pilat, Y. Zhangpresenter JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The electron collider ring of the Jefferson Lab Electron-Ion Collider (JLEIC) is designed to provide an electron beam with a small beam size at the IP for collisions with an ion beam in order to reach a desired high luminosity. For a chosen beta-star at the IP, electron beam size is determined by the equilibrium emittance that can be obtained through a linear optics design. This paper briefly describes the baseline design of the electron collider ring reusing PEP-II components and considering their parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and reports a few approaches to reducing the equilibrium emittance in the electron collider ring.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW016
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WEPMW017	Ion Beam Polarization Dynamics in the 8 Gev Booster of the Jleic Project at Jlab	2460
	V.S. Morozov, Y.S. Derbenev, F. Lin, Y. Zhangpresenter JLab, Newport News, Virginia, USA Y. Filatov MIPT, Dolgoprudniy, Moscow Region, Russia A.M. Kondratenko, M.A. Kondratenko Science and Technique Laboratory Zaryad, Novosibirsk, Russia
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. In the Jefferson Lab's Electron-Ion Collider (JLEIC) project, an injector of polarized ions into the collider ring is a superconducting 8 GeV booster. Both figure-8 and racetrack booster versions were considered. Our analysis showed that the figure-8 ring configuration allows one to preserve the polarization of any ion species during beam acceleration using only small longitudinal field with an integral less than 0.5 Tm. In the racetrack booster, to preserve the polarization of ions with the exception of deuterons, it suffices to use a solenoidal Siberian snake with a maximum field integral of 30 Tm. To preserve deuteron polarization, we propose to use arc magnets for the race-track booster structure with a field ramp rate of the order of 1 T/s. We calculate deuteron and proton beam polarizations in both the figure-8 and racetrack boosters including alignment errors of their magnetic elements using the Zgoubi code.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW017
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WEPMW019	Study of Beam Synchronization at JLEIC	2463
	V.S. Morozov, Y.S. Derbenev, J. Guo, A. Hutton, Y. Zhangpresenter JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The ion collider ring of Jefferson Lab's Electron-Ion Collider (JLEIC) accommodates a wide range of ion energies, from 20 to 100 GeV for protons or from 8 to 40 GeV per nucleon for lead ions. In this medium energy range, ions are not fully relativistic, which means values of their relativistic beta are slightly below 1, leading to an energy dependence of revolution time of the collider ring. On the other hand, electrons with energy 3 GeV and above are already ultra-relativistic such that their speeds are effectively equal to the speed of light. The difference in speeds of colliding electrons and ions in JLEIC, when translated into a path-length difference necessary to maintain the same timing between electron and ion bunches, is quite large. In this paper, we explore schemes for synchronizing the electron and ion bunches at a collision point as the ion energy is varied.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW019
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WEPMW020	Storage-ring Electron Cooler for Relativistic Ion Beams	2466
	F. Lin, Y.S. Derbenev, D. Douglas, J. Guo, G.A. Krafft, V.S. Morozov, Y. Zhangpresenter JLab, Newport News, Virginia, USA R.P. Johnson Muons, Inc, Illinois, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357 Application of electron cooling at ion energies above a few GeV has been limited due to reduction of electron cooling efficiency with energy and difficulty in producing and accelerating a high-current high-quality electron beam. A high-current storage-ring electron cooler offers a solution to both of these problems by maintaining high cooling beam quality through naturally-occurring synchrotron radiation damping of the electron beam. However, the range of ion energies where storage-ring electron cooling can be used has been limited by low electron beam damping rates at low ion energies and high equilibrium electron energy spread at high ion energies. This paper reports a development of a storage ring based cooler consisting of two sections with significantly different energies: the cooling and damping sections. The electron energy and other parameters in the cooling section are adjusted for optimum cooling of a stored ion beam. The beam parameters in the damping section are adjusted for optimum damping of the electron beam. The necessary energy difference is provided by an energy recovering SRF structure. A prototype linear optics of such storage-ring cooler is presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW020
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WEPMW022	Multi-Cell RF-Dipole Deflecting and Crabbing Cavity	2469
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA
	Single cell superconducting rf-dipole cavities operating at 400 MHz, 499 MHz and 750 MHz have been designed, fabricated and successfully tested at cryogenic temperatures. These cavities have been shown to have attractive rf properties: high deflecting gradients, low electric and magnetic peak surface fields, and high shunt impedance. The single cell rf-dipole geometry has no lower order modes and has widely separated higher order mode spectrum. In this study we are investigating a multi-cell superconducting rf-dipole cavity operating at 952.6 MHz intended for the Jefferson Lab Energy Electron-Ion Collider. The analysis investigates the dependence of beam aperture variation and other cavity parameters on rf properties including cavity gradient, surface fields, shunt impedance and higher order mode separation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW022
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WEPMW023	Higher Luminosity eRHIC Ring-Ring Options and Upgrade	2472
	R.B. Palmer, J.S. Bergpresenter, M. Blaskiewicz, A.V. Fedotov, C. Montag, B. Parker, H. Witte BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. Lower risk ring-ring alternatives to the BNL linac-ling~[linacring] eRHIC electron ion collider (EIC) are discussed. The baseline from the Ring-Ring Working Group~[ringring] has a peak proton-electron luminosity of ≈§I{1.2e33}{cm-2.s-1}. An option has final focus quadrupoles starting immediately after the detector at 4.5~m, instead of at 32~m in the baseline. This allows the use of lower β*s. It also uses more, 720, lower intensity, bunches, giving reduced IBS emittance growth and requiring only low energy pre-cooling. It has a peak luminosity of ≈§I{7e33}{cm-2.s-1}. An upgrade of this option, requiring magnetic, or coherent, electron cooling, has 1440 bunches and peak luminosity of ≈§I{15e33}{cm-2.s-1}.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW023
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WEPMW025	Optimizing the Design of Linear Non-scaling Fixed Field Alternating Gradient Arcs for the Electron Rings of eRHIC	2475
	J.S. Berg BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. I describe a process for producing optimal linear non-scaling fixed field alternating gradient (FFAG) arc designs for the electron rings of eRHIC, an electron-ion collider in the RHIC tunnel at Brookhaven National Laboratory. The electrons are accelerated in two FFAG rings (low and high energy), which in addition to the arcs optimized here, contain straight sections, splitter/combiner sections, and a linac shared between the rings. The optimization process I use has two layers, an inner one meeting constraints and an outer optimization that minimizes a target function. The target function is an approximation to the FFAG arc cost, for which I give the function used and the basis for that choice. While reducing synchrotron radiation is important, I show that optimizing for synchrotron radiation alone leads to significant cost an performance penalties for the rest of the machine design for very little reduction in synchrotron radiation. I describe important constraints on the design, in particular minimum drift lengths, maximum and minimum tunes, and clearance from the beam to the beam pipe. Finally, I present possible eRHIC FFAG parameters resulting from this optimization.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW025
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WEPMW026	Beam-Beam Simulation With Crab-Cavities for Erhic	2479
	Y. Luo, Y. Hao, Y.C. Jing, V. Ptitsyn, D. Trbojevic 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. To avoid the luminosity loss due to cross-angle collision, crab cavities are being considered for the electron-ion collider designs at Brookhaven National Laboratory. In this article, we study the effects of crab cavities on the proton beam dynamics without and with beam-beam interactions. Dynamic apertures are to be calculated with various parameters of crab cavities. To minimize the distortion from a single crab cavity, harmonic crab cavities are also considered.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW026
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WEPMW027	The ERL-based Design of Electron-Hadron Collider eRHIC	2482
	V. Ptitsyn, E.C. Aschenauer, I. Ben-Zvi, J.S. Berg, M. Blaskiewicz, S.J. Brooks, K.A. Brown, J.C. Brutus, O.V. Chubar, A.V. Fedotov, D.M. Gassner, H. Hahn, Y. Hao, A. Hershcovitch, H. Huang, W.A. Jackson, Y.C. Jing, R.F. Lambiase, V. Litvinenko, C. Liu, Y. Luo, G.J. Mahler, B. Martin, G.T. McIntyre, W. Meng, F. Méot, T.A. Miller, M.G. Minty, B. Parker, I. Pinayev, V.H. Ranjbar, T. Roser, J. Skaritka, R. Than, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, E. Wang, G. Wang, H. Witte, Q. Wu, C. Xu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 1033 cm-2 s-1) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 1034 cm-2 s-1) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW027
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WEPMW028	First Attempts at using Active Halo Control at the LHC	2486
	J.F. Wagner Goethe Universität Frankfurt, Frankfurt am Main, Germany R. Bruce, H. Garcia Morales, W. Höfle, G. Kotzian, R. Kwee-Hinzmann, A. Langner, A. Mereghetti, E. Quaranta, S. Redaelli, A. Rossi, B. Salvachua, R. Tomás, G. Valentino, D. Valuch, J.F. Wagner CERN, Geneva, Switzerland G. Stancari Fermilab, Batavia, Illinois, USA
	Funding: Research supported by the High Luminosity LHC project. The beam halo population is a non-negligible factor for the performance of the LHC collimation system and the machine protection. In particular this could become crucial for aiming at stored beam energies of 700 MJ in the High Luminosity (HL-LHC) project, in order to avoid beam dumps caused by orbit jitter and to ensure safety during a crab cavity failure. Therefore several techniques to safely deplete the halo, i.e. active halo control, are under development. In a first attempt a novel way for safe halo depletion was tested with particle narrow-band excitation employing the LHC Transverse Damper (ADT). At an energy of 450 GeV a bunch selective beam tail scraping without affecting the core distribution was attempted. This paper presents the first measurement results, as well as a simple simulation to model the underlying dynamics.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW028
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WEPMW029	Simulation of Heavy-Ion Beam Losses with the SixTrack-FLUKA Active Coupling	2490
SUPSS008	use link to see paper's listing under its alternate paper code
	P.D. Hermes, R. Bruce, F. Cerutti, A. Ferrari, J.M. Jowett, A. Lechner, A. Mereghetti, D. Mirarchi, P.G. Ortega, S. Redaelli, B. Salvachua, E. Skordis, G. Valentino, V. Vlachoudis CERN, Geneva, Switzerland
	Funding: Work suppported by the Wolfgang Gentner Programme of the German BMBF The LHC heavy-ion program aims to further increase the stored ion beam energy, putting high demands on the LHC collimation system. Accurate simulations of the ion collimation efficiency are crucial to validate the feasibility of new proposed configurations and beam parameters. In this paper we present a generalized framework of the SixTrack-FLUKA coupling to simulate the fragmentation of heavy-ions in the collimators and their motion in the LHC lattice. We compare heavy-ion loss maps simulated on the basis of this framework with the loss distributions measured during heavy-ion operation in 2011 and 2015.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW029
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WEPMW030	Cleaning Performance of the Collimation System of the High Luminosity Large Hadron Collider	2494
	D. Mirarchi, A. Bertarelli, R. Bruce, F. Cerutti, P.D. Hermes, A. Lechner, A. Mereghetti, E. Quaranta, S. Redaelli CERN, Geneva, Switzerland R.B. Appleby UMAN, Manchester, United Kingdom H. Garcia Morales, R. Kwee-Hinzmann Royal Holloway, University of London, Surrey, United Kingdom
	Different upgrades of the LHC will be carried out in the framework of the High Luminosity project (HL-LHC), where the total stored energy in the machine will increase up to about 700 MJ. This unprecedented stored energy poses serious challenges for the collimation system, which was designed to handle safely up to about 360 MJ. In this paper the baseline collimation layout for HL-LHC is described, with main focus on upgrades related to the cleaning of halo and physics debris, and its expected performance is discussed. The main upgrade items include the presence of new collimators in the dispersion suppressor of the betatron cleaning insertion installed between two 11 T dipoles, and two additional collimators for an improved local protection of triplet magnets. Thus, optimized settings for the entire and upgraded collimation chain were conceived and are shown here together with the resulting cleaning performance. Moreover, the cleaning performance taking into account crab cavities it is also discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW030
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WEPMW031	Towards Optimum Material Choices for the HL-LHC Collimator Upgrade	2498
	E. Quaranta, A. Bertarelli, N. Biancacci, R. Bruce, F. Carra, E. Métral, S. Redaelli, A. Rossi, B. Salvant CERN, Geneva, Switzerland F. Carra Politecnico di Torino, Torino, Italy
	The first years of operation at the LHC showed that collimator material-related concerns might limit the performance. In addition, the HL-LHC upgrade will bring the accelerator beyond the nominal performance through more intense and brighter proton beams. A new generation of collimators based on advanced materials is needed to match present and new requirements. After several years of R&D on collimator materials, studying the behaviour of novel composites with properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW031
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WEPMW032	Radiation-induced Effects on LHC Collimator Materials under Extreme Beam Conditions	2502
	E. Quaranta, A. Bertarelli, F. Carra, P.D. Hermes, S. Redaelli, A. Rossi CERN, Geneva, Switzerland K. Bunk Goethe Universität Frankfurt, Frankfurt am Main, Germany F. Carra Politecnico di Torino, Torino, Italy J. Guardia Valenzuela Universidad de Zaragoza, Zaragoza, Spain P.D. Hermes Westfaelische Wilhelms-Universität Muenster, Muenster, Germany C.L. Hubert, M. Tomut GSI, Darmstadt, Germany P. Nocera Università di Roma I La Sapienza, Roma, Italy C. Porth TU Darmstadt, Darmstadt, Germany N. Simos BNL, Upton, Long Island, New York, USA
	Over the last years, several samples of present and novel LHC collimator materials were irradiated under various beam conditions (using protons, fast neutrons, light and heavy ions at different energies and fluences) in different facilities around the world. This was achieved through an international collaboration including many companies and laboratories over the world. The main goal of the beam tests and the post-irradiation campaign is the definition of a threshold for radiation damage above which LHC collimators need to be replaced. In this paper, highlights of the measurements performed will be presented. First conclusions from the available data are also discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW032
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WEPMW033	Validation of Simulation Tools for Fast Beam Failure Studies in the LHC	2506
	E. Quaranta, C. Bracco, R. Bruce, S. Redaelli CERN, Geneva, Switzerland
	The LHC collimation system protects passively the most sensitive machine equipment against beam losses. In particular, collimators are the last line of defense in case of single-turn failures that cannot be caught by the standard interlock system. The collimator settings are conceived to protect the machine even for very rare events, like beam abort failures with a full machine. Collimator settings are established in simulations through a dedicated tracking setup but also empirically validated by beam measurements at low intensities. A benchmark of simulations is essential for reliably estimating the response of the system for future machine configurations and beam parameters. In the paper, results are presented of tracking simulations for different optics deployed in the LHC Run II at 6.5 TeV and compared with data.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW033
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WEPMW034	First Operational Experience with Embedded Collimator BPMs in the LHC	2510
	G. Valentino, G. Baud, R. Bruce, M. Gąsior, J. Olexa, S. Redaelli, A. Vallonipresenter, J. Wenninger CERN, Geneva, Switzerland
	During Long Shutdown 1, 18 Large Hadron Collider (LHC) collimators were replaced with a new design, in which beam position monitor (BPM) pick-up buttons are embedded in the collimator jaws. The BPMs provide a direct measurement of the beam orbit at the collimators, and therefore can be used to align the collimators more quickly than using the standard technique which relies on feedback from beam losses. Online orbit measurements also mean that margins in the collimation hierarchy placed specifically to cater for unknown orbit drifts can be reduced, therefore increasing the beta-star and luminosity reach of the LHC. In this paper, the first operational results are presented, including a comparison with the standard alignment technique and a fill-to-fill analysis of the measured orbit in different machine modes in the first year of running after the shutdown.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW034
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WEPMW036	MERLIN Cleaning Studies with Advanced Collimator Materials for HL-LHC	2514
	A. Valloni, R. Bruce, A. Mereghetti, E. Quaranta, S. Redaelli CERN, Geneva, Switzerland R.B. Appleby UMAN, Manchester, United Kingdom J. Molson LAL, Orsay, France H. Rafique University of Huddersfield, Huddersfield, United Kingdom
	The challenges of the High-Luminosity upgrade of the Large Hadron Collider require improving the beam collimation system. An intense R&D program has started at CERN to explore novel materials for new collimator jaws to improve robustness and reduce impedance. Particle tracking simulations of collimation efficiency are performed using the code MERLIN which has been extended to include new materials based on composites. After presenting two different implementations of composite materials tested in MERLIN, we present simulation studies with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW036
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WEPMW037	MERLIN Simulations of the LHC Collimation System with 6.5 TeV Beams	2518
	A. Valloni Rome University La Sapienza, Roma, Italy R.B. Appleby, S.C. Tygier UMAN, Manchester, United Kingdom R. Bruce, A. Mereghetti, S. Redaelli CERN, Geneva, Switzerland J. Molson LAL, Orsay, France H. Rafique University of Huddersfield, Huddersfield, United Kingdom
	The accelerator physics code MERLIN has been extended in many areas to make detailed studies of the LHC collima- tion system and calculate loss maps from beam halo losses. Large scale tracking simulations have been produced for the 2015 run configuration at 6.5 TeV. We present results of cleaning inefficiency simulations of the LHC's multi-stage collimation system along with a detailed comparison be- tween MERLIN, SixTrack, and measured beam losses.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW037
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WEPMW039	JLEIC SRF Cavity RF Design	2522
	S. Wang, J. Guo, R.A. Rimmerpresenter, H. Wang JLab, Newport News, Virginia, USA
	The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW039
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WEPMW041	Multiple Bunch HOM Evaluation for eRHIC Main Linac Cavities	2525
	C. Xu, I. Ben-Zvi, M. Blaskiewicz, Y. Haopresenter, V. Ptitsyn BNL, Upton, Long Island, New York, USA
	Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. High current Superconducting Radiofrequency (SRF) 5-cell cavities are essential for the proposed ERL-based electron-ion collider eRHIC in BNL. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the ERL create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in the eRHIC 5-cell cavity with different ERL bunch patterns using both methods. We also discuss possible solutions to reduce this HOM power.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW041
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WEPMW042	Trapped Modes Study and BBU Analysis in the 5-Cell 650 MHz Cavity	2529
	C. Xu, I. Ben-Zvi, Y. Haopresenter, V. Ptitsyn, W. Xu BNL, Upton, Long Island, New York, USA I. Petrushina SUNY SB, Stony Brook, New York, USA
	Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. #chenxu@bnl.gov eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 1033- 1034 cm-2 ses−1. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW042
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WEPMW043	Frequency Scaling Study of Crab Cavity for Future Colliders with Crab Crossing	2532
	Y. Hao, V. Ptitsyn 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. Crab crossing is an essential concept in the newly proposed colliders or the upgrades. It enables crossing angles to achieve lower β* without a loss of luminosity. The frequency of the crab cavity shall be chosen with various considerations, including the luminosity degradation, emittance growth due to synchro-beta resonances and RF noises. We use the figure of merits and related simulation to establish the frequency scaling relations with important beam parameters, which guide the choice of crab cavity frequency for new designs.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW043
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WEPMW044	Start-to-End Simulation of eRHIC ERL	2535
	Y. Hao, S.J. Brooks, Y.C. Jing, F. Méot, V. Ptitsyn, D. Trbojevic, N. Tsoupas 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. The ERL-ring eRHIC adopts the electron accelerator design of a multi-pass energy recovery linac (ERL), with fixed field alternating gradient (FFAG) recirculating passes. To ensure the beam quality in the accelerating and decelerating stage and the energy recovery efficiency, detailed start-to-end simulation is required to evaluate the various beam dynamics effects, such as synchrotron radiation, wake fields, coherent synchrotron radiation. In this paper, we present the eRHIC ERL start-to-end simulation strategy with various simulation codes and the current status.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW044
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