Keyword: luminosity
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MOZA01 Simulated Beam-beam Limits for Circular Lepton and Hadron Colliders simulation, collider, lepton, hadron 27
 
  • K. Ohmi
    KEK, Ibaraki, Japan
  
  The beam-beam limit is one of the most important collider parameters. For lepton colliders the empirical tune shift limits are higher than for hadron colliders, which has been attributed to strong radiation damping. The beam-beam limit in hadron colliders, like the LHC, can be affected by noise. For future higher-energy colliders, like FCC-hh or SppC, the limit can be higher or lower, in the presence of still rather weak synchrotron radiation. For circular lepton colliders, like DAΦNE, SuperKEKB, FCC-ee or CepC, the effect of large Piwinski angle, and crab waist, as well as the dependence of the beam-beam limit on the number of interaction points are important questions. This presentation reviews the state of the art in weak-strong, quasi-strong-strong and strong-strong beam-beam simulations and reports the various dependencies of the simulated beam-beam limit on the aforementioned parameters.  
slides icon Slides MOZA01 [4.453 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOZA01  
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MOPMB006 First Tests of SuperKEKB Luminosity Monitors during 2016 Single Beam Commissioning vacuum, simulation, scattering, background 81
 
  • D. El Khechen, P. Bambade, A. Blin, P. Cornebise, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
    LAL, Orsay, France
  • Y. Funakoshi, Y. Ohnishi, S. Uehara
    KEK, Ibaraki, Japan
  
  The SuperKEKB e+e− collider aims to reach a very high luminosity of 8 1035 cm-2s−1, using highly focused ultra-low emittance bunches colliding every 4ns. Fast luminosity monitoring is required for luminosity feedback and optimisation in presence of dynamic imperfections. The aimed relative precision is about 10-3 in 1ms, which can be in principle achieved thanks to the very large cross-section of the radiative Bhabha process at zero degree scattering angle. Diamond, Cherenkov and scintillator sensors are to be placed just outside the beam pipe, downstream of the interaction point in both rings, at locations with event rates consistent with the aimed precision and small enough backgrounds from single-beam particle losses. The initial configuration installed for the 2016 "phase 1" single beam commissioning will be described, including the sensors, mechanical setup, readout electronics and first stage DAQ. Preliminary measurements and analysis of beam gas Bremsstrahlung loss data collected with the luminosity monitors will be reported and compared with a detailed simulation, for several experimental conditions during the SuperKEKB commissioning.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB006  
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MOPMR025 Beam Size Estimation from Luminosity Scans at the LHC During 2015 Proton Physics Operation emittance, proton, operation, experiment 290
 
  • M. Hostettler, G. Papotti
    CERN, Geneva, Switzerland
  • M. Hostettler
    LHEP, Bern, Switzerland
  
  As a complementary method for measuring the beam size for high-intensity beams at 6.5 TeV flat-top energy, beam separation scans were done regularly at the CERN Large Hadron Collider (LHC) during 2015 proton physics operation. The luminosities measured by the CMS experiment during the scans were used to derive the convoluted beam size and orbit offset bunch-by-bunch. This contribution will elaborate on the method used to derive plane-by-plane, bunch-by-bunch emittances from the scan data, including uncertainties and corrections. The measurements are then compared to beam size estimations from absolute luminosity, synchrotron light telescopes, and wire scanners. In particular, the evolution of the emittance over the course of several hours in collisions is studied and bunch-by-bunch differences are highlighted.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR025  
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MOPMR027 Employing Beam-Gas Interaction Vertices for Transverse Profile Measurements detector, vacuum, emittance, real-time 296
 
  • M.N. Rihl, A. Alexopoulos, V. Baglin, C. Barschel, E. Bravin, G. Bregliozzi, N. Chritin, B. Dehning, M. Ferro-Luzzi, C. Gaspar, M. Giovannozzi, R. Jacobsson, L.K. Jensen, O.R. Jones, N.J. Jurado, V. Kain, M. Kuhn, B. Luthi, P. Magagnin, R. Matev, N. Neufeld, J. Panman, V. Salustino Guimaraes, B. Salvant, R. Veness, S. Vlachos
    CERN, Geneva, Switzerland
  • A. Bay, F. Blanc, S. Gianì, G.J. Haefeli, P. Hopchev, T. Nakada, B. Rakotomiaramanana, O. Schneider, M. Tobin, Q.D. Veyrat, Z. Xu
    EPFL, Lausanne, Switzerland
  • R. Greim, W. Karpinski, T. Kirn, S. Schael, G. Schwering, M. Wlochal, A. von Dratzig
    RWTH, Aachen, Germany
  
  Interactions of high-energy beam particles with residual gas offer a unique opportunity to measure the beam profile in a non-intrusive fashion. Such a method was successfully pioneered* at the LHCb experiment using a silicon microstrip vertex detector. During the recent Large Hadron Collider shutdown at CERN, a demonstrator Beam-Gas Vertexing system based on eight scintillating-fibre modules was designed**, constructed and installed on Ring 2 to be operated as a pure beam diagnostics device. The detector signals are read out and collected with LHCb-type front-end electronics and a DAQ system consisting of a CPU farm. Tracks and vertices will be reconstructed to obtain a beam profile in real time. Here, first commissioning results are reported. The advantages and potential for future applications of this technique are discussed.
* LHCb collaboration, Journal of Instrumentation, 9, P12005
** P. Hopchev in Proc. of IPAC 2014, June 15-20, 2014, Dresden Germany 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR027  
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TUYA01 BEPCII Performance and Beam Dynamics Studies on Luminosity lattice, radiation, synchrotron, synchrotron-radiation 1014
 
  • C.H. Yu, Z. Duan, S. Gu, Y.Y. Guo, X.Y. Huang, D. Ji, H.F. Ji, Y. Jiao, Zh.C. Liu, Y.M. Peng, Q. Qin, Y.S. Sun, S.K. Tian, J.Q. Wang, N. Wang, X.H. Wang, Y. Wei, X.M. Wen, J. Wu, J. Xing, G. Xu, Y. Yue, C. Zhang, Y. Zhang
    IHEP, Beijing, People's Republic of China
  
  The upgrade of the Beijing Electron Positron Collider, BEPCII, is now in a good performance for both high energy physics and synchrotron radiation experiments. The luminosity at the design energy of 1.89 GeV reached the design value 1.0*1033/cm2/s1 recently. A lot of work, including accelerator physics study and technical progress, has been done for the luminosity enhancement, not only at the design energy, but all the energy region run for HEP experiments from 1.0 to 2.3 GeV. The performance of BEPCII and the process of luminosity enhancement will be described in detail.  
slides icon Slides TUYA01 [5.801 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUYA01  
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TUPMB040 LHC Accelerator Fault Tracker - First Experience operation, cryogenics, hardware, ion 1190
 
  • A. Apollonio, L. Ponce, C. Roderick, R. Schmidt, B. Todd, D. Wollmann
    CERN, Geneva, Switzerland
  
  Availability is one of the key performance indicators of LHC operation, being directly correlated with integrated luminosity production. An effective tool for availability tracking is a necessity to ensure a coherent capture of fault information and relevant dependencies on operational modes and beam parameters. At the beginning of LHC Run 2 in 2015, the Accelerator Fault Tracking (AFT) tool was deployed at CERN to track faults or events affecting LHC operation. Information derived from the AFT is crucial for the identification of areas to improve LHC availability, and hence LHC physics production. For the 2015 run, the AFT has been used by members of the CERN Availability Working Group, LHC Machine coordinators and equipment owners to identify the main contributors to downtime and to understand the evolution of LHC availability throughout the year. In this paper the 2015 experience with the AFT for availability tracking is summarised and an overview of the first results as well as an outlook to future developments is given.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB040  
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TUPMB041 The SuperKEKB Interaction Region Corrector Magnets quadrupole, octupole, sextupole, optics 1193
 
  • B. Parker, M. Anerella, J. Escallier, A.K. Ghosh, A.K. Jain, A. Marone, P. Wanderer
    BNL, Upton, Long Island, New York, USA
  • Y. Arimoto, N. Higashi, M. Iwasaki, N. Ohuchi, K. Tsuchiya, X. Wang, H. Yamaoka, Z.G. Zong
    KEK, Ibaraki, Japan
  
  Work for the SuperKEKB luminosity upgrade of the KEKB asymmetric e+e− collider is near completion. In this paper we review the design, production and testing of superconducting correction coils, that are needed to achieve the desired IR optics performance, and are integrated with the final focus magnets. For SuperKEKB 43 coils were produced at BNL using Direct Wind techniques. These coils underwent preliminary warm field harmonic quality assurance measurements before shipment to KEK. At KEK final cold measurements of these coils were made prior to their ultimate integration with the SuperKEKB IR magnets. SuperKEKB corrector production was challenging due to the large number of coil types and configurations that had to be fitted into very limited available space. Also the nature of the SuperKEKB optics sets fairly stringent local field quality requirements for these coils.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB041  
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TUPMW002 LHC Luminosity Modeling for RUNII emittance, radiation, scattering, proton 1403
 
  • F. Antoniou, G. Arduini, M. Hostettler, M. Lamont, S. Papadopoulou, Y. Papaphilippou, G. Papotti, M. Pojer, B. Salvachua, M. Wyszynski
    CERN, Geneva, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project
After a long shut-down (LS1), LHC restarted its operation on April 2015 at a record energy of 6.5TeV, achieving soon a good luminosity performance. In this paper, a luminosity model based on the three main components of the LHC luminosity degradation (intrabeam scattering, synchrotron radiation and luminosity burn-off), is compared with data from runII. Based on the observations, other sources of luminosity degradation are discussed and the model is refined. Finally, based on the experience from runI and runII, the model is used for integrated luminosity projections for the HL-LHC beam parameters. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW002  
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TUPMW006 Power Deposition in LHC Magnets Due to Bound-Free Pair Production in the Experimental Insertions ion, dipole, simulation, heavy-ion 1418
 
  • C. Bahamonde Castro, B. Auchmann, M.I. Besana, K. Brodzinski, R. Bruce, F. Cerutti, J.M. Jowett, A. Lechner, T. Mertens, V. Parma, S. Redaelli, M. Schaumann, N.V. Shetty, E. Skordis, G.E. Steele, R. van Weelderen
    CERN, Geneva, Switzerland
  
  The peak luminosity achieved during Pb-Pb collisions in the LHC in 2015 (3x1027cm-2s−1) well exceeded the design luminosity and is anticipated to increase by another factor 2 after the next Long Shutdown (2019- 2020). A significant fraction of the power dissipated in ultra-peripheral Pb-Pb collisions is carried by ions from bound-free pair production, which are lost in the dispersion suppressors adjacent to the experimental insertions. At higher luminosities, these ions risk to quench superconducting magnets and might limit their operation due to the dynamic heat load that needs to be evacuated by the cryogenic system. In this paper, we estimate the power deposition in superconducting coils and the magnet cold mass and we quantify the achievable reduction by deviating losses to less sensitive locations or by installing collimators at strategic positions. The second option is considered for the dispersion suppressor next to the ALICE insertion, where a selective displacement of losses to a magnet-free region is not possible.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW006  
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TUPMW007 Impact of Long Range Beam-Beam Effects on Intensity and Luminosity Lifetimes from the 2015 LHC Run emittance, experiment, hadron, dynamic-aperture 1422
 
  • M.P. Crouch, R.B. Appleby
    UMAN, Manchester, United Kingdom
  • D. Banfi, C. Tambasco
    EPFL, Lausanne, Switzerland
  • J. Barranco, R. Bruce, X. Buffat, T. Pieloni, M. Pojer, B. Salvachua, G. Trad
    CERN, Geneva, Switzerland
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Funding: Research supported by the High Luminosity LHC project
Luminosity is one of the key parameters that determines the performance of colliding beams in the Large Hadron Collider (LHC). Luminosity can therefore be used to quantify the impact of beam-beam interactions on the beam lifetimes and emittances. The High Luminosity Large Hadron Collider (HL-LHC) project aims to reach higher luminosities, approximately a factor of 7 larger than the nominal LHC at peak luminosity without crab cavities. Higher luminosities are achieved by increasing the bunch populations and reducing the transverse beam sizes. This results in stronger beam-beam effects. Here the LHC luminosity and beam intensity decay rates are analysed as a function of reducing beam separation with the aim of characterising the impact of beam-beam effects on the luminosity and beam lifetime. The analysis and results are discussed with possible application to the HL-LHC upgrade. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW007  
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TUPMW008 Evolution of the Beam Parameters during Luminosity Production in the Future Circular Hadron Collider emittance, collider, scattering, damping 1426
 
  • X. Buffat, D. Schulte
    CERN, Geneva, Switzerland
  
  The evolution of the beam parameters during luminosity production in the Future Circular Hadron Collider (FCC-hh) is described based on basic models of the effect of synchrotron radiations, intra-beam scattering, luminosity burn-off and beam-beam limitations, allowing for an estimation of the luminosity performance in different running scenarios. It is shown that a large variations of the beam parameters is expected during a cycle. Potential operational schemes adapting to these variations are considered.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW008  
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TUPMW012 Beam Offset Stabilization Techniques for the LHC Collision Points experiment, optics, ground-motion, operation 1438
 
  • A.A. Gorzawski, R. Jacobsson, J. Wenninger
    CERN, Geneva, Switzerland
  
  Maintaining head-on collisions over many hours is an important aspect of optimizing the performance of a collider. For current LHC operation where the beam optics is fixed during periods of colliding beam, mainly ground motion induced perturbations have to be compensated. The situation will become significantly more complex when luminosity leveling will be applied following the LHC luminosity upgrades. During β* leveling the optics in the interaction region changes significantly, feed-downs from quadrupole misalignment may induce significant orbit changes that may lead to beam offsets at the collision points. Such beam offsets induce a loss of luminosity and reduce the stability margins for collective effects that is provided by head-on beam-beam. It is therefore essential that the beam offsets at the collision points are minimized during the leveling process. This paper will review sources and mitigation techniques for the orbit perturbation at the collision points during β* leveling, and present results of experiments performed at the LHC to mitigate and compensate such offsets.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW012  
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TUPMW013 Experimental Demonstration of β* Leveling at the LHC betatron, controls, experiment, emittance 1442
 
  • A.A. Gorzawski, D. Mirarchi, B. Salvachua, J. Wenninger
    CERN, Geneva, Switzerland
  
  The HL-LHC project foresees to boost the LHC peak luminosity beyond the capabilities of the LHC experimental detectors. Leveling the luminosity down to a constant value that is sustainable for the experiments is therefore the operational baseline of HL-LHC. Various luminosity leveling techniques are available at the LHC. Leveling by adjusting β*, the betatron function at the interaction point, to maintain a constant luminosity is favorable because the beams remain head-on which provides optimal stability from the point of view of collective effects. Smooth leveling by β* requires however excellent control of the beam orbits and beam losses in the interaction regions since the beam offsets should not vary by more than around one r.m.s. beam size during the process. This leveling scheme has been successfully tested and experimentally demonstrated during the LHC machine development program in 2015. This paper presents results on luminosity leveling over a β* range from 10 m to 0.8 m and provides an outlook on future developments and use of this technique at the LHC.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW013  
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TUPMW018 Radiation Load Optimization in the Final Focus System of FCC-hh shielding, radiation, quadrupole, optics 1462
 
  • R. Martin, M.I. Besana, F. Cerutti, R. Tomás
    CERN, Geneva, Switzerland
  
  With a center-of-mass energy of up to 100 TeV, FCC-hh will produce highly energetic collision debris at the Interaction Point (IP). Protecting the final focus quadrupoles from this radiation is challenging, since the required amount of shielding placed inside the magnets will reduce the free aperture, thereby limiting the β* reach and luminosity. Hence, radiation mitigation strategies that make best use of the available aperture are required. In this paper, we study the possibility to split the first quadrupole Q1 into two quadrupoles with individual apertures, in order to distribute the radiation load more evenly and reduce the peak dose.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW018  
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TUPMW021 Roman Pot Insertions in High-Intensity Beams for the CT-PPS Project at LHC insertion, impedance, proton, vacuum 1473
 
  • M. Deile, R. Bruce, A. Mereghetti, D. Mirarchi, S. Redaelli, B. Salvachua, B. Salvant, G. Valentino
    CERN, Geneva, Switzerland
  
  The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) at the LHC IP5 aims at exploring diffractive physics at high luminosity in standard LHC fills. It is based on 14 Roman Pots (RPs), designed to host tracking and time-of-flight detectors for measuring the kinematics of leading protons. To reach the physics goals, the RPs will finally have to approach the beams to distances of 15 beam σs (i.e. ~1.5 mm) or closer. After problems with showers and impedance heating in first high-luminosity RP insertions in 2012, the LS1 of LHC was used for upgrades in view of impedance minimisation and for adding new collimators to intercept RP-induced showers. In 2015 the effectiveness of these improvements was shown by successfully inserting the RPs in all LHC beam intensity steps to a first-phase distance of ~25 σs. This contribution reviews the measurements of debris showers and impedance effects, i.e. the data from Beam Loss Monitors, beam vacuum gauges and temperature sensors. The dependences of the observables on the luminosity are shown. Extrapolations to L=1034 cm-2 s-1 and smaller distances to the beam do not indicate any fundamental problems. The plans for 2016 are outlined.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW021  
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TUPMW023 Macroparticle-Induced Losses During 6.5 TeV LHC Operation operation, proton, electron, beam-losses 1481
 
  • G. Papotti, M. Albert, B. Auchmann, E.B. Holzer, M.K. Kalliokoski, A. Lechner
    CERN, Geneva, Switzerland
  
  One of the major performance limitations for operating the LHC at high energy was feared to be the so called UFOs (Unidentified Falling Objects, presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam). Indeed much higher rates were observed in 2015 compared to Run 1, and about 20 fills were prematurely terminated by too high losses caused by such events. Additionally they triggered a few beam induced quenches at high energy, the first in the history of the LHC. In this paper we review the latest update on the analysis of these events, e.g. the conditioning observed during the year and possible correlations with beam and machine parameters. At the same time we also review the optimization of beam loss monitor thresholds in terms of machine protection and availability.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW023  
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TUPMW025 Machine Protection from Fast Crab Cavity Failures in the High Luminosity LHC cavity, collimation, proton, simulation 1485
 
  • A. Santamaría García, R. Bruce, H. Burkhardt, F. Cerutti, R. Kwee-Hinzmann, A. Lechner, K.N. Sjobak, A. Tsinganis
    CERN, Geneva, Switzerland
  • R. Kwee-Hinzmann
    Royal Holloway, University of London, Surrey, United Kingdom
  
  The time constant of a crab cavity (CC) failure can be faster than the reaction time of the active protection system. In such a scenario, the beams cannot be immediately extracted, making the the protection of the machine rely on the passive protection devices. At the same time, the energy stored in the High Luminosity (HL) LHC beams will be doubled with respect to the LHC to more than 700 MJ, which increases the risk of damaging the machine and the experiments in a failure scenario. In this study we estimate the impact that different CC failures have on the collimation system. We also give a first quantitative estimate of the effect of these failures on the elements near the experiments based on FLUKA simulations, using an updated HL-LHC baseline.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW025  
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TUPMW027 The 2015 Heavy-Ion Run of the LHC ion, experiment, heavy-ion, operation 1493
 
  • J.M. Jowett, R. Alemany-Fernandez, R. Bruce, M. Giovannozzi, P.D. Hermes, W. Höfle, M. Lamont, T. Mertens, S. Redaelli, M. Schaumann, J.A. Uythoven, J. Wenninger
    CERN, Geneva, Switzerland
  
  In late 2015 the LHC collided lead nuclei at a beam energy of 6.37 Z TeV, chosen to match the 5.02 TeV per colliding nucleon pair of the p-Pb collision run in 2013. In so doing, it surpassed its design luminosity by a factor of 2. Besides the higher energy, the operational configuration had a number of new features with respect to the previous Pb-Pb run at 3.5 Z TeV in 2011; unusual bunch patterns providing collisions in the LHCb experiment for the first time, luminosity levelling and sharing requirements, a vertical displacement of the interaction point in the ALICE experiment, and operation closer to magnet quench limits with mitigation measures. We present a summary of the commissioning and operation and what has been learned in view of future heavy-ion operation at higher luminosity.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW027  
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TUPMW028 Bound-Free Pair Production in LHC Pb-Pb Operation at 6.37 Z TeV per Beam experiment, ion, dipole, simulation 1497
 
  • J.M. Jowett, B. Auchmann, C. Bahamonde Castro, M.K. Kalliokoski, A. Lechner, T. Mertens, M. Schaumann, C. Xu
    CERN, Geneva, Switzerland
  
  In the 2015 Pb-Pb collision run of the LHC, the power of the secondary beams emitted from the interaction point by the bound-free pair production process reached new levels while the propensity of the bending magnets to quench is higher at the new magnetic field levels. This beam power is about 70 times greater than that contained in the luminosity debris and is focussed on a specific location. As long foreseen, orbit bumps were introduced in the dispersion suppressors around the highest luminosity experiments to mitigate the risk by displacing and spreading out these losses. An experiment designed to induce quenches and determine the quench levels and luminosity limit was carried out to assess the need for special collimators to intercept these secondary beams.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW028  
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TUPMW034 A 200 MHz SC-RF System for the HL-LHC cavity, emittance, injection, impedance 1513
 
  • R. Calaga, R. Tomás
    CERN, Geneva, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project
A quarter wave β=1 superconducting cavity at 200 MHz is proposed for the LHC as an alternative to the present 400 MHz RF system. The primary motivation of such a system would be to accelerate higher intensity and longer bunches with improved capture efficiency. Advantages related to minimizing electron cloud effects, intra-beam scattering, heating and the possibility of luminosity levelling with bunch length are described. Some considerations related to cavity optimization, beam loading and technological challenges are addressed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW034  
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TUPMW035 Performance and Operational Aspects of HL-LHC Scenarios optics, simulation, emittance, electron 1516
 
  • L.E. Medina Medrano
    DCI-UG, León, Mexico
  • R. Tomás
    CERN, Geneva, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project. Work supported by the Beam Project (CONACYT, Mexico).
Several alternatives to the present HL-LHC baseline configuration have been proposed, aiming either to improve the potential performance, reduce its risks, or to provide options for addressing possible limitations or changes in its parameters. In this paper we review and compare the performance of the HL-LHC baseline and the main alternatives with the latest parameters set. The results are obtained using refined simulations of the evolution of the luminosity with β*-levelling, for which new criteria have been introduced, such as improved calculation of the intrabeam scattering and the addition of penalty steps to take into account the necessary time to move between consecutive optics during the process. The features of the set of optics are discussed for the nominal baseline. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW035  
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TUPMW037 Luminosity Targets for FCC-hh collider, hadron, proton, detector 1523
 
  • F. Zimmermann, M. Benedikt, X. Buffat, D. Schulte
    CERN, Geneva, Switzerland
  
  Funding: Supported by the European Commission under the Capacities 7th Framework Programme project EuCARD-2, grant agreement 312453, and under the HORIZON 2020 project EuroCirCol, grant agreement 654305.
We discuss the choice of target values for the peak and integrated luminosity of a future high-energy frontier circular hadron collider (FCC-hh). We review the arguments on the physics reach of a hadron collider. Next we show that accelerator constraints will limit the beam current and the turnaround time. Taking these limits into account, we derive an expression for the ultimate integrated luminosity per year, depending on a possible pile-up limit imposed by the physics experiments. We finally benchmark our result against the planned two phases of FCC-hh. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW037  
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TUPMW039 Measurement of the Total Cross Section of Gold-Gold Collisions at sqrt {sNN}=200 GeV ion, heavy-ion, collider, emittance 1530
 
  • W. Fischer, A.J. Baltz, M. Blaskiewicz, K.A. Drees, D.M. Gassner, Y. Luo, M.G. Minty, P. Thieberger
    BNL, Upton, Long Island, New York, USA
  • I.A. Pshenichnov
    RAS/INR, Moscow, Russia
  
  Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
Heavy ion collision cross sections totaling several hundred barns have been calculated previously for the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). These total cross sections are more than one order of magnitude larger than the geometric ion-ion cross sections, primarily due to Bound-Free Pair Production (BFPP) and Electro-Magnetic Dissociation (EMD). Apart from a general interest in verifying the calculations experimentally, an accurate prediction of the losses created in the heavy ion collisions is of practical interest for RHIC and the LHC, where some collision products are lost in cryogenically cooled magnets. These losses have the potential to affect power and signal electronic devices and quench superconducing magnets. We have previously reported the total cross section measurement of U+U collisions at a center-of-mass energy of 192.8 GeV per nucleon-pair. Here we present the equivalent analysis for Au+Au collisions with the data available from a low-intensity store of RHIC Run in 2014. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW039  
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TUPOR017 Beam-beam Simulation of Crab Cavity with Frequence Dependent Noise for LHC Upgrade cavity, simulation, emittance, feedback 1691
 
  • J. Qiang
    LBNL, Berkeley, California, USA
  • G. Arduini, Y. Papaphilippou, T. Pieloni
    CERN, Geneva, Switzerland
  • J. Barranco
    EPFL, Lausanne, Switzerland
  
  High luminosity LHC upgrade will improve the luminosity of the current LHC operation by an order of magnitude. Crab cavity as a critical component for compensating luminosity loss from large crossing angle collision and also providing luminosity leveling for the LHC upgrade is being actively pursued. In this paper, we will report on the study of potential effects of the frequence-dependent crab cavity noise on the beam luminosity lifetime using strong-strong beam-beam simulations.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR017  
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WEZA01 RHIC Performance with Stochastic Cooling for Ions and Head-on Beam-beam Compensation for Protons operation, electron, proton, ion 2055
 
  • W. Fischer, J.G. Alessi, Z. Altinbas, E.C. Aschenauer, G. Atoian, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, M.R. Costanzo, T. D'Ottavio, K.A. Drees, A.V. Fedotov, C.J. Gardner, D.M. Gassner, X. Gu, C.E. Harper, M. Harvey, T. Hayes, J. Hock, H. Huang, R.L. Hulsart, J.P. Jamilkowski, T. Kanesue, N.A. Kling, J.S. Laster, C. Liu, Y. Luo, D. Maffei, Y. Makdisi, M. Mapes, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, T.A. Miller, M.G. Minty, C. Montag, J. Morris, G. Narayan, C. Naylor, S. Nemesure, M. Okamura, S. Perez, A.I. Pikin, P.H. Pile, A. Poblaguev, V. Ptitsyn, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, W.B. Schmidke, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, S. Tepikian, R. Than, P. Thieberger, J.E. Tuozzolo, B. Van Kuik, G. Wang, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, W. Zhang
    BNL, Upton, Long Island, New York, USA
  • M. Bai, Y. Dutheil
    FZJ, Jülich, Germany
  • S.M. White
    ESRF, Grenoble, France
  
  Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The Relativistic Heavy Ion Collider (RHIC) has two main operating modes with heavy ions and polarized protons respectively. In addition to a continuous increase in the bunch intensity in all modes, two major new systems were completed recently mitigating the main luminosity limit and leading to significant performance improvements. For heavy ion operation stochastic cooling mitigates the effects of intrabeam scattering, and for polarized proton operation head-on beam-beam compensation mitigated the beam-beam effect. We present the performance increases with these upgrades for heavy ions and polarized protons, as well as an overview of all operating modes past and planned. 		 
slides icon Slides WEZA01 [12.687 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEZA01  
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WEOCA01 Operation of the LHC with Protons at High Luminosity and High Energy operation, proton, emittance, cryogenics 2066
 
  • G. Papotti, M. Albert, R. Alemany-Fernandez, G.E. Crockford, K. Fuchsberger, R. Giachino, M. Giovannozzi, G.H. Hemelsoet, W. Höfle, D. Jacquet, M. Lamont, D. Nisbet, L. Normann, M. Pojer, L. Ponce, S. Redaelli, B. Salvachua, M. Solfaroli Camillocci, R. Suykerbuyk, J.A. Uythoven, J. Wenninger
    CERN, Geneva, Switzerland
  
  In 2015 the Large Hadron Collider (LHC) entered the first year in its second long Run, after a 2-year shutdown that prepared it for high energy. The first two months of beam operation were dedicated to setting up the nominal cycle for proton-proton operation at 6.5 TeV/beam, and culminated with the first physics with 3 nominal bunches/ring at 13 TeV CoM on 3 June. The year continued with a stepwise intensity ramp up that allowed reaching 2244 bunches/ring for a peak luminosity of ~5·1033 cm-2s−1 and a total of just above 4 fb-1 delivered to the high luminosity experiments. Beam operation was shaped by the high intensity effects, e.g. electron cloud and macroparticle-induced fast losses (UFOs), which on a few occasions caused the first beam induced quenches at high energy. This paper describes the operational experience with high intensity and high energy at the LHC, together with the issues that had to be tackled along the way.  
slides icon Slides WEOCA01 [4.013 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOCA01  
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WEPMB058 LHC Crab Cavity Coupler Test Boxes HOM, cavity, operation, higher-order-mode 2248
 
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • R. Apsimon, G. Burt, A.R.J. Tutte
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga, A. Macpherson, E. Montesinos
    CERN, Geneva, Switzerland
  • S.D. Silva
    ODU, Norfolk, Virginia, USA
  • B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  The LHC double quarter wave (DQW) crab cavities have two different types of Higher Order Mode (HOM) couplers in addition to a fundamental power coupler (FPC). The FPC requires conditioning, so to achieve this we have designed a radio-frequency (RF) quarter wave resonator to provide high transmission between two opposing FPCs. For the HOM couplers we must ensure that the stop-band filter is positioned at the cavity frequency and that peak transmission occurs at the same frequencies as the strongest HOMs. We have designed two test boxes which preserve the cavity spectral response in order to test the couplers.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB058  
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WEPMR036 Crab Cavities for eRHIC - A Preliminary Design cavity, electron, proton, linac 2351
 
  • Q. Wu, I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The proposed eRHIC electron ion collider at BNL must use a relatively large crossing angle between the ion and electron beams for various reasons, including the reduction of long-range beam-beam effects and minimization of synchrotron radiation noise in the detector. To prevent significant loss of the luminosity due to this large crossing angle, the design of the collider requires the use of groups of crab cavities to provide local crabbing for both proton/ion and electron beams. We will base our design for eRHIC crab cavities based on our experience in the design of the 400 MHz double quarter wave crab cavity (DQWCC) for the Hi-Lumi upgrade of the Large Hadron Collider at CERN. This DQWCC design is scaled to different frequencies of a main crab cavity and its higher harmonics for eRHIC. In this paper, we discuss the preliminary designs of the eRHIC crab cavities and their major parameters. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR036  
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WEPMW009 Towards a Mono-chromatization Scheme for Direct Higgs Production at FCC-ee emittance, optics, collider, synchrotron 2434
 
  • 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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WEPMW023 Higher Luminosity eRHIC Ring-Ring Options and Upgrade electron, emittance, quadrupole, linac 2472
 
  • R.B. Palmer, J.S. Berg, 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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WEPMW026 Beam-Beam Simulation With Crab-Cavities for Erhic proton, electron, dynamic-aperture, cavity 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 electron, hadron, linac, proton 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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WEPMW030 Cleaning Performance of the Collimation System of the High Luminosity Large Hadron Collider collimation, ion, insertion, simulation 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 impedance, collimation, beam-losses, simulation 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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WEPMW043 Frequency Scaling Study of Crab Cavity for Future Colliders with Crab Crossing cavity, ion, collider, electron 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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WEPOR009 Intra-beam IP Feedback Studies for the 380 GeV CLIC Beam Delivery System feedback, ground-motion, kicker, simulation 2683
 
  • R.M. Bodenstein, P. Burrows, J. Snuverink
    JAI, Oxford, United Kingdom
  • F. Plassard
    CERN, Geneva, Switzerland
  
  In its currently-envisaged initial stage, the Compact Linear Collider (CLIC) will collide beams with a 380 GeV center of mass energy. To maintain the luminosity within a few percent of the design value, beam stability at the interaction point (IP) must be controlled at the sub-nanometer level. To help achieve such control, use of an intra-pulse IP feedback system is planned. With CLIC's very short bunch spacing of 0.5 ns, and nominal pulse duration of 176 ns, this feedback system presents a significant technical challenge. Furthermore, as part of a study to optimize the design of the beam delivery system (BDS), several L* configurations have been studied. In this paper, we will review the IP feedback simulations for the 380 GeV machine for two L* configurations, and compare luminosity recovery performance with that of the original L* configuration in the 3 TeV machine.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR009  
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WEPOY056 Beam-beam Simulations with Realistic Crab Crossing for the eRhic Ring-Ring Electron Beam electron, proton, cavity, hadron 3123
 
  • C. Montag
    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 15mrad beam crossing angle in the eRHIC ring-ring interaction region requires crab crossing of the 250GeV proton beam to restore the luminosity. Since the product of the RF voltage and the RF frequency of the crab cavities is constant for a given crossing angle, higher frequencies are preferred in order to limit the require voltage. However, the 20cm RMS proton bunch length provides an upper limit of the useable frequencies due to the significant curvature of the RF waveform over this bunch length. To study the effectof realistic crab cavities with a finite wavelength on electron beam-beamdynamics and to determine the potential need for higher harmonic crab cavities to linearize the kick a simulation code has been developed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY056  
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WEPOY057 The 2015 eRHIC Ring-Ring Design electron, proton, polarization, emittance 3126
 
  • C. Montag, E.C. Aschenauer, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, W. Fischer, V. Litvinenko, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, S. Tepikian, D. Trbojevic, F.J. Willeke
    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 reduce the technical risk of the future electron-ion collider eRHIC currently under study at BNL, the ring-ring scheme has been revisited over the summer of 2015. The goal of this study was a design that covers the full center-of-mass energy range from 32 to 141 GeV with an initial luminosity around 1033 cm-2 sec-1, upgradeable to 1034 cm-2 sec-1 later on. In this presentation the baseline design will be presented, and future upgrades will be discussed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY057  
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THPMB044 Limitations on Optics Measurements in the LHC optics, dipole, injection, hadron 3339
 
  • P.K. Skowroński, F.S. Carlier, J.M. Coello de Portugal, A. Garcia-Tabares, A. Langner, E.H. Maclean, L. Malina, M. McAteer, T. Persson, R. Tomás
    CERN, Geneva, Switzerland
  • A. Langner
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • L. Malina
    University of Oslo, Oslo, Norway
  
  In preparation of the optics commissioning at an energy of 6.5 TeV, many improvements have been done to cope with the expected reduced signal to noise ratio due to lowered bunch intensities imposed by machine protection considerations. This included, among others, an increase of the flat top duration of the AC dipole excitations, which allowed to use more turn-by-turn data for the analysis. The longer data acquisition revealed slow drifts of the optics, which limited the increased measurement precision. Furthermore, we will present how orbit drifts influenced dispersion measurements and, as a consequence, posed another limitation for the optics correction. In this paper we will discuss the implications of these observations for the measurement and correction of the optics.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB044  
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THPMR045 CLIC Beam Delivery System Rebaselining and Long L* Lattice Optimization lattice, sextupole, synchrotron-radiation, radiation 3500
 
  • F. Plassard, D. Schulte, R. Tomás
    CERN, Geneva, Switzerland
  • P. Bambade
    LAL, Orsay, France
  
  This paper summarizes the re-optimization study made on the CLIC Beam Delivery System (BDS) in the framework of the rebaselining for beam collisions at 380 GeV for the initial energy stage. It describes the optimization process applied for the beam parameters as well as for the Final Focus system (FFS) lattice design with respect to the energy upgrade transition to 3 TeV. Both initial and final energy stages were optimized for a short (nominal) and a long L* (6 meters). The long L* option allows the last quadrupole (QD0) to be be located outward of the detector solenoid field influence. FFS optics designs based on the Local chromaticity correction and performance comparisons for both L* options are shown.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR045  
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THPMR046 Advanced BBA Techniques for the Final Focuses of Future Linear Colliders sextupole, collider, linear-collider, alignment 3504
 
  • J. Snuverink, A. Latina, D. Schulte, R. Tomás
    CERN, Geneva, Switzerland
  • R.M. Bodenstein
    JAI, Oxford, United Kingdom
  
  Tuning the Final-Focus System of future linear colliders is one of the open challenges the linear collider community is undertaking. Future colliders like ILC and CLIC will feature complex lattice design to focus the beams to nanometer level at the Interaction Point. Standard Beam-Based Alignment (BBA) techniques have proven to hardly meet the requirements in terms of acceptable emittance growth, in both machines. A set of new techniques, respectively called: nonlinear Dispersion-Free Steering (DFS), DFS-knobs scan, and hybrid DFS-knobs with beamsize measurements, have been put in place to cope with the challenge. This paper will reveal the key ideas behind the new techniques, and compare their effectiveness w.r.t. the conventional BBA tuning procedures.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR046  
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THPMR047 Two-beam Tuning in the CLIC BDS collider, sextupole, linear-collider, simulation 3508
 
  • J. Snuverink, R.M. Bodenstein
    JAI, Egham, Surrey, United Kingdom
  • R. Tomás
    CERN, Geneva, Switzerland
  
  Beam tuning in the beam delivery system (BDS) is one of the major challenges for the future linear colliders. In those colliders, due to fast detuning of the final focus optics both beamlines will need to be tuned simultaneously. An initial two-beam tuning study for the Compact Linear Collider (CLIC) BDS had been performed, but was not fully satisfactory. In this paper a more extensive study is presented, as well as several improvements to the tuning algorithm. A comparative study between two competing CLIC final focus systems (FFS), the traditional and the compact FFS, will be discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR047  
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THPMW003 Prototype Power Supply for SuperKEKB Final Focus Superconducting Corrector Magnets power-supply, superconducting-magnet, controls, impedance 3537
 
  • T. Oki, T. Adachi, S. Nakamura, N. Ohuchi, N. Tokuda
    KEK, Ibaraki, Japan
  
  A prototype power supply for the SuperKEKB final focus superconducting corrector magnets was developed. The aiming specifications of the power supply are a DC rated output of ± 60 A ± 5 V bipolar, current setting resolution < 1 ppm, current stability < 5 ppm/8 h, temperature coefficient < 1 ppm/degree, and current ripple < 5 ppm, where the assumed magnet inductance and cable resistance are 0.2'8.7 mH and 75 mohms, respectively. High power tests were performed and expected results were obtained.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW003  
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THPMY010 LHC Beam Vacuum Evolution During 2015 Machine Operation electron, operation, proton, solenoid 3673
 
  • C. Yin Vallgren, G. Bregliozzi, P. Chiggiato
    CERN, Geneva, Switzerland
  
  The LHC successfully returned to operation in April, 2015 after almost 2 years of Long Shutdown 1 (LS1) for various upgrade and consolidation programs. During 2015 operation, the LHC operated for more than 1000 fills. The 2015 LHC proton physics ended with 2244 bunches per beam circulating with 25 ns bunch spacing at top energy of 6.5 TeV. This paper summarizes the dynamic vacuum observations in different locations along the LHC during dedicated fills as well as during physics runs with both 50 ns and 25 ns bunch spacing. The causes for the dynamic pressure rises are investigated and are presented. A clear beam conditioning effect is observed, as well as a so-called de-conditioning effect. Furthermore, for the experimental areas, the dynamic pressure evolution is also presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY010  
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THPOR004 Magnetic Measurement for Superconducting-Quadrupole-Magnets of Final-Focus System for SuperKEKB quadrupole, sextupole, octupole, radiation 3771
 
  • Y. Arimoto, M. Iwasaki, N. Ohuchi, K. Tsuchiya, X. Wang, H. Yamaoka, Z.G. Zong
    KEK, Ibaraki, Japan
  
  SuperKEKB is an upgrade project of KEKB to increase its luminosity to 8 x 1035 cm-2 s-1 based on the nano-beam scheme. In SuperKEKB, one of a key element is a final-focus system; it reduces e−/e+ beam size to 50 nm in vertical and 10 μm in horizontal direction at an interaction point (IP). The system consists of eight superconducting quadrupole magnets and four quadrupoles are aligned on the each beam line. The quadrupole, QC1P(QC1E), which is located at the closest position to the IP on the e+(e−) beam line, generates a field gradient of about 70 T/m. An inner diameter of coil and a magnetic length for QC1P(QC1E) are 25(33) mm and 334(373) mm, respectively. The production of all quadrupole magnets are completed. To confirm their field qualities, we performed magnetic measurement for each magnet in advance to be integrated into cryostats on the beam lines. In the measurement, the quadrupoles were cooled down to 4.2 K in a test vertical cryostat and field harmonic components were measured with harmonic coils. The magnitude of error multipole components for all magnets met requirements from beam optics design. In this paper we describe the measurement results.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR004  
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THPOR005 Tunnel Level Variation in the SuperKEKB Interaction Region radiation, alignment, operation, feedback 3774
 
  • M. Masuzawa, T. Adachi, T. Kawamoto
    KEK, Ibaraki, Japan
  
  SuperKEKB is an electron-positron collider, which aims to achieve a peak luminosity 40 times higher than that of KEKB. The vertical beam sizes of both rings are squeezed down to 50 - 60 nm at the interaction point (IP), which accounts for a factor of 20 in the luminosity increase, and the beam currents are doubled from those of KEKB. Tunnel motion can be critical for realizing the collisions of such small beams. A Hydrostatic Leveling System (HLS), which consists of 18 sensors, was installed on both sides of the IP to monitor tunnel level variations continuously. Effects of heavy rain and installation of the radiation shield blocks on the tunnel floor level are clearly seen. The HLS data during construction and SuperKEKB commissioning are reported.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR005  
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THPOR009 Cepc Partial Double Ring Lattice Design lattice, dynamic-aperture, dipole, factory 3785
 
  • F. Su
    Institute of High Energy Physics (IHEP), People's Republic of China
  • S. Bai, T.J. Bian, Z. Duan, J. Gao, H. Geng, D. Wang, Y. Wang, M. Xiao, G. Xu, Y. Zhang
    IHEP, Beijing, People's Republic of China
  
  In this paper, we introduced the layout and lattice design of Circular-Electron-Positron-Collider (CEPC) partial double ring (PDR) scheme. The baseline design of CEPC is a single beam-pipe electron positron collider, which has to adopt pretzel orbit scheme. And it is not suitable to serve as a high luminosity Z factory. If we choose partial double ring scheme, we can get a higher luminosity with lower power and be suitable to serve as a high luminosity Z factory. In this paper, we discussed the details of CEPC partial double ring lattice design and showed the dynamic aperture study and optimization.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR009  
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THPOR010 CEPC Parameter Choice and Partial Double Ring Design sextupole, emittance, dynamic-aperture, optics 3788
 
  • D. Wang, S. Bai, T.J. Bian, X. Cui, Z. Duan, J. Gao, H. Geng, Y.Y. Guo, Q. Qin, N. Wang, Y. Wang, M. Xiao, J.Y. Zhai, C. Zhang, Y. Zhang
    IHEP, Beijing, People's Republic of China
  • W. Chou
    Fermilab, Batavia, Illinois, USA
  • F. Su
    Institute of High Energy Physics (IHEP), People's Republic of China
  
  Funding: Work supported by the National Foundation of Natural Sciences (11505198 and 11575218)
In order to avoid the pretzel orbit, CEPC is proposed to use partial double ring scheme in CDR. Based on crab waist scheme, we hope to either increase the luminosity with same beam power as Pre-CDR, or reduce the beam power while keeping the same luminosity in Pre-CDR. FFS with crab sextupoles has been developed and the arc lattice was redesigned to acheive the lower emittance for crab waist scheme. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR010  
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THPOR019 Momentum Acceptance Optimization in FCC-ee Lattice (CERN) sextupole, quadrupole, lattice, dipole 3814
 
  • A.V. Bogomyagkov, E.B. Levichev
    BINP SB RAS, Novosibirsk, Russia
  
  Funding: Work is supported by the Ministry of Education and Science of the Russian Federation.
The part of the ongoing study of the future circular collider (FCC) is an electron positron machine with center of mass energy from 90 to 350 GeV. Crab waist collision scheme and small (1 mm) vertical beta function at the interaction point (IP) provide superior luminosity. At the top energy, radiation in the field of the opposite bunch (beamstrahlung) limits the beam lifetime and therefore achievable luminosity. Beamstrahlung influence depends on momentum acceptance of the lattice, the value of 2% provides acceptable lifetime. The small value of vertical beta function enhances effects of nonlinear chromaticity. The present work describes principles used in design and optimization of FCC-ee momentum acceptance optimization and are based on chromatic variations of beta function. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR019  
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THPOR047 Preliminary Concept and Key Technologies of HIEPA Accelerator collider, synchrotron, brightness, emittance 3895
 
  • Z.R. Zhou, Q. Luo, L. Wang, W. Xu, B. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Supported by National Natural Science Foundation of China (11375178 and 11575181) and the Fundamental Research Funds for the Central Universities, Grant No WK2310000046
High energy physicists proposed a new collider: super tau-charm factory. The name of the project is high intensity electron positron accelerator facility. As high intensity electron positron collider, it runs in an energy range of 2-7 GeV. As an advanced light source, it can also provide high quality synchrotron radiation from VUV to soft X-ray. The facility will be a symmetrical two-ring collider located at Hefei. This paper shows preliminary conception of the storage rings. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR047  
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THPOY043 Time Scale of Crab Cavity Failures Relevant for High Luminosity LHC cavity, damping, resonance, simulation 4196
 
  • K.N. Sjobak, R. Bruce, H. Burkhardt, A. Macpherson, A. Santamaría García
    CERN, Geneva, Switzerland
  • R. Kwee-Hinzmann
    Royal Holloway, University of London, Surrey, United Kingdom
  • A. Santamaría García
    EPFL, Lausanne, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project
A good knowledge of the effects of the crab cavities, required for the baseline High Luminosity LHC (HL-LHC), is needed before the results of the first tests of crab cavity prototypes in the SPS, planned for 2018, will be available. In case of crab cavity failures, we have to make sure that time scales are long enough so that the beams can be cleanly dumped before damage by beam loss occurs. We discuss our present knowledge and modeling of crab cavity induced beam losses, combined with mechanical deformation. We discuss lower limits on the time scales required for safe operation, and possible failure mitigation methods. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY043  
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