TUPMW —  Poster Session   (10-May-16   16:00—18:00)

Paper	Title	Page
TUPMW001	SPPC Parameter Choice and Lattice Design	1400
	F. Su Institute of High Energy Physics (IHEP), People's Republic of China S. Bai, T.J. Bian, Y.K. Chen, J. Gao, J.Y. Tang, D. Wang, Y. Wangpresenter IHEP, Beijing, People's Republic of China
	In this paper we showed a systematic method of appropriate parameter choice for a circular pp collider by using analytical expression of beam-beam tune shift limit started from given design goal and technical limitations. Based on parameters scan, we obtain a set of parameters for SPPC with different circumferences like 54km, 78km or 100km and different energies like 70TeV or 100TeV. We also showed the first version of SPPC lattice although it needs lots of work to do and to be optimized.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW001
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TUPMW002	LHC Luminosity Modeling for RUNII	1403
	F. Antoniou, G. Arduinipresenter, 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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TUPMW003	Integration, Configuration and Coordination: from Project to Reality, at CERN	1407
	M. Barberan Marin, S. Bartolome-Jimenez, M. Bernardini, T.W. Birtwistle, S. Chemli, J.-P. Corso, J. Coupard, K. Foraz, S. Grillot, Y. Muttoni, A.-L. Perrot CERN, Geneva, Switzerland
	The rigorous process in place at CERN to approve and follow-up the implementation of any modification of the LHC machine and its Injectors is presented in this paper. Our methodology implies the support of three teams, in charge of the configuration management, the scheduling and safety coordination, and the 3D integration studies. At each stage of the project the support of the three teams evolves, to provide the adequate support in the preparation phase and during the technical stops and long shutdowns. The formal roles and the processes used to govern the interaction of the Integration, Configuration and Coordination teams, and their relation to the project teams during the preparation and implementation phases, for activities to be performed in LHC and its injector chain are described and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW003
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TUPMW004	Assessment and Mitigation of the Proton-Proton Collision Debris Impact on the FCC Triplet	1410
	M.I. Besana, F. Cerutti, S.D. Fartoukh, R. Martin, R. Tomás CERN, Geneva, Switzerland R. Martin Humboldt University Berlin, Berlin, Germany
	The Future Circular hadron Collider (FCC-hh), which is designed to operate at a centre-of-mass energy of 100 TeV and to deliver ambitious targets in terms of both instantaneous and integrated luminosity, poses extreme challenges in terms of machine protection during operation and with respect to long-term damages. Energy deposition studies are a crucial ingredient for its design. One of the relevant radiation sources are collision debris particles, which de- posit their energy in the interaction region elements and in particular in the superconducting magnet coils of the final focus triplet quadrupoles, to be protected from the risk of quenching and deterioration. In this contribution, the collision debris will be characterised and expectations obtained with FLUKA will be presented, including magnet lifetime considerations. New techniques including crossing angle gymnastics for peak dose deposition mitigation (as recently introduced in the framework of the LHC operation), will be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW004
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TUPMW005	Characterization of the Radiation Field in the FCC-hh Detector	1414
	M.I. Besana, F. Cerutti, A. Ferrari, W. Riegler, V. Vlachoudis CERN, Geneva, Switzerland
	As part of the post-LHC high-energy program, a study is ongoing to design a new 100 km long hadron collider, which is expected to operate at a centre-of-mass energy of 100 TeV and to accumulate up to 30 ab−1, with a peak instantaneous luminosity that could reach 30 1034cm−2s−1. In this context, the evaluation of the radiation load on the detector is a key step for the choice of materials and technologies. In this contribution, a first detector concept will be presented. At the same time, fluence distributions, relevant for detector occupancy, and accumulated damage on materials and electronics will be shown. The effectiveness of a possible shielding configuration, intended to minimise the background in the muon chambers and tracking stations, will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW005
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TUPMW006	Power Deposition in LHC Magnets Due to Bound-Free Pair Production in the Experimental Insertions	1418
	C. Bahamonde Castro, B. Auchmann, M.I. Besanapresenter, 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	1422
	M.P. Crouch, R.B. Appleby UMAN, Manchester, United Kingdom D. Banfi, C. Tambasco EPFL, Lausanne, Switzerland J. Barranco, R. Bruce, X. Buffatpresenter, 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	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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TUPMW009	Simulation of Head-on Beam-Beam Limitations in Future High Energy Colliders	1430
	X. Buffat, T. Pieloni, C. Tambasco CERN, Geneva, Switzerland J. Barranco, A. Florio EPFL, Lausanne, Switzerland
	The Future Circular Hadron Collider (FCC-hh) project calls for studies in a new regime of beam-beam interactions. While the emittance damping due to synchrotron radiation is still slower than in past or existing lepton colliders, it is significantly larger than in other hadron colliders. The slow reduction of the emittance is profitable for higher luminosity in term of transverse beam size at the interaction points and also to mitigate long-range beam-beam effects, potentially allowing for a reduction of the crossing angle between the beams during the operation. In such conditions, the strength of head-on beam-beam interactions increases, potentially limiting the beam brightness. 4D weak-strong and strong-strong simulations are performed in order to assess these limitations.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW009
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TUPMW011	Current Status of Instability Threshold Measurements in the LHC at 6.5 TeV	1434
	L.R. Carver, J. Barranco, N. Biancacci, X. Buffatpresenter, W. Höfle, G. Kotzian, T. Lefèvre, T.E. Levens, E. Métral, T. Pieloni, B. Salvant, C. Tambasco CERN, Geneva, Switzerland N. Wang IHEP, Beijing, People's Republic of China M. Zobov INFN/LNF, Frascati (Roma), Italy
	Throughout 2015, many measurements of the minimum stabilizing octupole current required to prevent coherent transverse instabilities have been performed. These measurements allow the LHC impedance model at flat top to be verified and give good indicators of future performance and limitations. The results are summarized here, and compared to predictions from the simulation code DELPHI.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW011
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TUPMW012	Beam Offset Stabilization Techniques for the LHC Collision Points	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	1442
SUPSS001	use link to see paper's listing under its alternate paper code
	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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TUPMW014	Improved Aperture Measurements at the LHC and Results from their Application in 2015	1446
	P.D. Hermes, R. Bruce, M. Fiascaris, H. Garcia, M. Giovannozzi, A. Mereghetti, D. Mirarchi, E. Quaranta, S. Redaelli, B. Salvachua, G. Valentino CERN, Geneva, Switzerland R. Kwee-Hinzmann Royal Holloway, University of London, Surrey, United Kingdom E. Quaranta Politecnico/Milano, Milano, Italy
	A good knowledge of the available aperture in the LHC is essential for a safe operation due to the risk of magnet quenches or even damage in case of uncontrolled beam losses. Experimental validations of the available aperture are therefore crucial and were in the past carried out by either a collimator scan combined with beam excitations or through the use of local orbit bumps. In this paper, we show a first comparison of these methods in the same machine configuration, as well as a new very fast method based on a beam-based collimator alignment and a new faster variant of the collimator scan method. The methods are applied to the LHC operational configuration for 2015 at injection and with squeezed beams and the measured apertures are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW014
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TUPMW015	Symplectic Tracking of Multi-Isotopic Heavy-Ion Beams in SixTrack	1450
	P.D. Hermes, R. Bruce, R. De Maria CERN, Geneva, Switzerland
	Funding: Work suppported by the Wolfgang Gentner Programme of the German BMBF The software SixTrack provides symplectic proton tracking over a large number of turns. The code is used for the tracking of beam halo particles and the simulation of their interaction with the collimators to study the efficiency of the LHC collimation system. Tracking simulations for heavy-ion beams require taking into account the mass to charge ratio of each particle because heavy ions can be subject to fragmentation at their passage through the collimators. In this paper we present the derivation of a Hamiltonian for multi-isotopic heavy-ion beams and symplectic tracking maps derived from it. The resulting tracking maps were implemented in the tracking software SixTrack. With this modification, SixTrack can be used to natively track heavy-ion beams of multiple isotopes through a magnetic accelerator lattice.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW015
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TUPMW016	Effect of the LHC Beam Screen Baffle on the Electron Cloud Buildup	1454
	A. Romano, G. Iadarola, K.S.B. Lipresenter, G. Rumolo CERN, Geneva, Switzerland
	Funding: Research supported by the High Luminosity LHC project Electron Cloud (EC) has been identified as one of the major intensity-limiting factors in the CERN Large Hadron Collider (LHC). Due to the EC, an additional heat load is deposited on the perforated LHC beam screen, for which only a small cooling capacity is available. In order to preserve the superconducting state of the magnets, pumping slots shields were added on the outer side of the beam screens. In the framework of the design of the beam screens of the new HL-LHC triplets, the impact of these shields on the multipacting process was studied with macroparticle simulations. For this purpose multiple new features had to be introduced in the PyECLOUD code. This contribution will describe the implemented simulation model and summarize the outcome of this study.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW016
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TUPMW017	Electron Cloud Observations during LHC Operation with 25 ns Beams	1458
	K.S.B. Li, H. Bartosik, G. Iadarola, L. Mether, A. Romano, G. Rumolo, M. Schenk CERN, Geneva, Switzerland
	While during the Run 1 (2010-2012) of the Large Hadron Collider (LHC) most of the integrated luminosity was produced with 50 ns bunch spacing, for the Run 2 start-up (2015) it was decided to move to the nominal bunch spacing of 25 ns. As expected, with this beam configuration strong electron cloud effects were observed in the machine, which had to be mitigated with dedicated 'scrubbing' periods at injection energy. This enabled to start the operation with 25 ns beams at 6.5 TeV, but e-cloud effects continued to pose challenges while gradually increasing the number of circulating bunch trains. This contribution will review the encountered limitations and the mitigation measures that where put in place and will discuss possible strategies for further performance gain.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW017
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TUPMW018	Radiation Load Optimization in the Final Focus System of FCC-hh	1462
SUPSS003	use link to see paper's listing under its alternate paper code
	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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TUPMW019	First Evaluation of Dynamic Aperture at Injection for FCC-hh	1466
	B. Dalena, D. Boutin, A. Chancé, J. Payet CEA/IRFU, Gif-sur-Yvette, France B.J. Holzer, R. Martinpresenter, D. Schulte CERN, Geneva, Switzerland
	Funding: This Research and Innovation Action project submitted to call H2020-INFRADEV-1-2014-1 receives funding from the European Union's H2020 Framework Programme under grant agreement no. 654305. In the hadron machine option, proposed in the context of the Future Circular Colliders (FCC) study, the dipole field quality is expected to play an important role, as in the LHC. A preliminary evaluation of the field quality of dipoles, based on the Nb3Sn technology, has been provided by the magnet group. The effect of these field imperfections on the dynamic aperture, using the present lattice design, is presented and first tolerances on the main multipole components are evaluated.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW019
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TUPMW020	Status of the Beam Optics of the Future Hadron-Hadron Collider FCC-hh	1470
	A. Chancé CEA/DSM/IRFU, France D. Boutin, B. Dalena, J. Payet CEA/IRFU, Gif-sur-Yvette, France B.J. Holzer, R. Martinpresenter, D. Schulte CERN, Geneva, Switzerland
	Funding: This work was supported by the HORIZON 2020 project EuroCirCol, grant agreement 654305. Following the recommendations of the European Strategy Group for High Energy Physics, CERN launched a design study for possible future circular collider projects, FCC, to investigate their feasibility for high energy physics research. The study covers three options, a proton-proton collider, a circular e+/e− collider and a scenario for e-p collisions to study deep inelastic scattering. The present paper describes the beam optics and the lattice design of the Future Hadron-Hadron Collider (FCC-hh). The status of the first order and second order optics of the ring will be shown for collisions at the required centre-of-mass energy of 100 TeV cm.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW020
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TUPMW021	Roman Pot Insertions in High-Intensity Beams for the CT-PPS Project at LHC	1473
	M. Deile, R. Bruce, A. Mereghetti, D. Mirarchipresenter, 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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TUPMW022	Modelling and Measurements of Bunch Profiles at the LHC Flat Bottom	1477
SUPSS004	use link to see paper's listing under its alternate paper code
	S. Papadopoulou, F. Antoniou, J.E. Muller, Y. Papaphilippou, G. Trad CERN, Geneva, Switzerland
	At the LHC flat bottom the interplay between a series of effects (i.e. intrabeam scattering, longitudinal beam manipulations, non-linearities of the machine, etc) can lead to a population of the tails of the beam distributions, which may become non-Gaussian. This paper presents observations of the evolution of particle distributions in the LHC flat bottom. Novel distribution functions are employed to represent the beam profiles, and used as a guideline for generalising emittance growth rate estimations due to IBS. Finally, an attempt is made to benchmark an IBS Monte-Carlo simulation code, able to track 3D particle distributions, with the measured beam profile evolutions.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW022
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TUPMW023	Macroparticle-Induced Losses During 6.5 TeV LHC Operation	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	1485
SUPSS005	use link to see paper's listing under its alternate paper code
	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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TUPMW026	Feed-Forward Corrections for Tune and Chromaticity Injection Decay During 2015 LHC Operation	1489
	M. Solfaroli Camillocci, M. Juchno, M. Lamont, M. Schaumannpresenter, E. Todesco, J. Wenninger CERN, Geneva, Switzerland
	After two years of shutdown, the Large Hadron Collider (LHC) has been operated in 2015 at 6.5 TeV, close to its designed energy. When the current is stable at low field, the harmonic components of the main circuits are subject to a dynamic variation induced by current redistribution on the superconducting cables. The Field Description of the LHC (FiDel) foresaw an increase of the decay at injection of tune (quadrupolar components) and chromaticity (sextupolar components) of about 50% with respect to LHC Run1 due to the higher operational current. This paper discusses the beam-based measurements of the decay during the injection plateau and the implementation and accuracy of the feed-forward corrections as present in 2015. Moreover, the observed tune shift proportional to the circulating beam intensity and it's foreseen feed-forward correction are covered.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW026
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TUPMW027	The 2015 Heavy-Ion Run of the LHC	1493
	J.M. Jowett, R. Alemany-Fernandez, R. Bruce, M. Giovannozzi, P.D. Hermes, W. Höfle, M. Lamont, T. Mertens, S. Redaelli, M. Schaumannpresenter, 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	1497
	J.M. Jowett, B. Auchmann, C. Bahamonde Castro, M.K. Kalliokoski, A. Lechner, T. Mertens, M. Schaumannpresenter, 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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TUPMW029	Tune and Chromaticity Control During Snapback and Ramp in 2015 LHC Operation	1501
	M. Schaumann, M. Juchno, M. Lamont, M. Solfaroli Camillocci, E. Todesco, J. Wenninger CERN, Geneva, Switzerland
	Because of current redistribution on the superconducting cables, the harmonic components of the magnetic fields of the superconducting magnets in the Large Hadron Collider (LHC) show decay during the low field injection plateau. This results in tune and chromaticity variations for the beams. In the first few seconds of the ramp the original hysteresis state of the magnetic field is restored - the field snaps back. These fast dynamic field changes lead to strong tune and chromaticity excursions that, if not properly controlled, induce beam losses and potentially trigger a beam dump. A feed-forward system applies predicted corrections during the injection plateau and to the first part of the ramp to avoid violent changes of beam conditions. This paper discusses the snapback of tune and chromaticity as observed in 2015, as well as the control of beam parameters during the ramp. It also evaluates the quality of the applied feed-forward corrections and their reproducibility.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW029
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TUPMW030	Review of LHC On-line Model Implementation and of its Applications	1505
	T. Persson, J.M. Coello de Portugal, M. Fjellstrom, L. Malina, J. Roy, P.K. Skowronskipresenter, A. Szczotka CERN, Geneva, Switzerland J.S. Moeskops RID, Delft, The Netherlands
	The online model of the LHC aims to provide an accurate description of the machine at any given time. In order to do so it extracts the current optics in the machine along with other crucial parameters. It also provides the functionality to match the measured orbit using virtual correctors and the measured beta functions using virtual quadrupoles. In this way an accurate effective model can be created. In order to facilitate the use of the online model a graphical user interface has been developed. In this article we describe the design of the online model and its application in different studies. We give examples how it has been used to predict the influence of changes before they were applied to the machine.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW030
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TUPMW031	Combined Ramp and Squeeze to 6.5 TeV in the LHC	1509
	M. Solfaroli Camillocci, S. Redaelli, R. Tomás, J. Wenninger CERN, Geneva, Switzerland
	The cycle of the LHC is composed of an energy ramp followed by a betatron squeeze, needed to reduce the beta- star value in the interaction points. Since Run 1, studies have been carried out to investigate the feasibility of combining the two operations, thus considerably reducing the duration of the operational cycle. In Run 2, the LHC is operating at the energy of 6.5 TeV that requires a much longer cycle than that of Run 1. Therefore, the performance gains from a Combined Ramp and Squeeze (CRS) is more interesting. Merging the energy ramp and the betatron squeeze could result in a gain of several minutes for each LHC cycle. With increasing maturity of LHC operation, it is now possible to envisage more complex beam manipulations; this paper describes the first machine experiment with beam, aiming at validating the combination of ramp and squeeze, which was performed in 2015, during a machine development phase. The operation experience with the LHC run at 2.51 TeV, when CRS down to 4 meters was deployed and a the first results of 2016 run are also reviewed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW031
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TUPMW034	A 200 MHz SC-RF System for the HL-LHC	1513
	R. Calaga, R. Tomaspresenter 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	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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TUPMW036	Optimizing Chromatic Coupling Measurement in the LHC	1520
	T. Persson, R. Tomaspresenter CERN, Geneva, Switzerland
	Optimizing chromatic coupling measurement in the LHC Chromatic coupling introduces a dependency of transverse coupling with energy. LHC is equipped with skew sextupoles to compensate the possible adverse effects of chromatic coupling. In 2012 a beam-based correction was calculated and applied successfully for the fist time. However, the method used to reconstruct the chromatic coupling was dependent on stable tunes and equal chromaticities between the horizontal and vertical planes. In this article an improved method to calculate the chromatic coupling without these constraints is presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW036
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TUPMW037	Luminosity Targets for FCC-hh	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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TUPMW038	RHIC Operation with Asymmetric Collisions in 2015	1527
	C. Liu, E.C. Aschenauer, G. Atoian, M. Blaskiewicz, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, W. Fischerpresenter, C.J. Gardner, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, J.S. Laster, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, G. Narayan, S.K. Nayak, S. Nemesure, P.H. Pile, A. Poblaguev, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, G. Wang, K. Yip, A. Zaltsman, K. Zeno, S.Y. Zhang BNL, Upton, Long Island, New York, USA S.M. White ESRF, Grenoble, France
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Collisions with beams of highly asymmetric rigidities (proton-Gold and proton-Aluminum) were provided for the RHIC physics programs in 2015. Magnets were moved for the first time in RHIC prior to the run to accommodate the asymmetric beam trajectories during acceleration and at store. A special ramping scheme was designed to keep the revolution frequencies of the beams in the two rings equal. The unique operational experience of the asymmetric run will be reviewed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW038
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TUPMW039	Measurement of the Total Cross Section of Gold-Gold Collisions at sqrt {sNN}=200 GeV	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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TUPMW040	Beam-beam Simulation for the 2015 RHIC Proton Run with Electron Lenses	1533
	Y. Luo, W. Fischer, X. Gu, G. Robert-Demolaize, V. Schoefer BNL, Upton, Long Island, New York, USA S.M. White ESRF, Grenoble, France
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Electron lenses were used for head-on beam-beam compensation for the first time in the 2015 Relativistic Heavy Ion Collider (RHIC) 100~GeV polarized proton run. Lattices with the achromatic telescopic squeeze (ATS) scheme of β* are adopted to improve the off-momentum dynamic aperture. The phase advances between the electron lenses to one of the two collisional points are set to kπ to minimize the beam-beam resonance driving terms. In this article, we present the results from weak-strong and strong-strong beam-beam simulations with head-on beam-beam compensations for these lattices. Simulations are also carried out aiming to explain the observations from operation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW040
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