IPAC2014 - Classification: 01 Circular and Linear Colliders / A01 Hadron Colliders

Paper	Title	Page
MOXAA01	Challenges for Highest Energy Circular Colliders	1
	F. Zimmermann, M. Benedikt, D. Schulte, J. Wenninger CERN, Geneva, Switzerland
	A new tunnel of 80-100 km circumference could host a 100 TeV centre-of-mass energy-frontier proton collider (FCC-hh/VHE-LHC), with a circular lepton collider (FCC-ee/TLEP) as potential intermediate step, and a lepton-hadron collider (FCC-he) as additional option. FCC-ee, operating at four different energies for precision physics of the Z, W, and Higgs boson and the top quark, represents a significant push in terms of technology and design parameters. Pertinent R&D efforts include the RF system, top-up injection scheme, optics design for arcs and final focus, effects of beamstrahlung, beam polarization, energy calibration, and power consumption. FCC-hh faces other challenges, such as high-field magnet design, machine protection and effective handling of large synchrotron radiation power in a superconducting machine. All these issues are being addressed by a global FCC collaboration. A parallel design study in China prepares for a similar, but smaller collider, called CepC/SppC.
	Slides MOXAA01 [27.493 MB]
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TUYA01	First Experience with Electron Lenses for Beam-beam Compensation in RHIC	913
	W. Fischer, Z. Altinbas, D. Bruno, M.R. Costanzo, X. Gu, J. Hock, A.K. Jain, Y. Luo, C. Mi, R.J. Michnoff, T.A. Miller, A.I. Pikin, T. Samms, Y. Tan, R. Than, P. Thieberger, S.M. White BNL, Upton, Long Island, New York, USA
	Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. The head-on beam-beam interaction is the dominant luminosity limiting effect in polarized proton operation in RHIC. To mitigate this effect two electron lenses were installed in the two RHIC rings. We summarize the hardware and electron beam commissioning results to date, and report on the first experience with the electron-hadron beam interaction. In 2014 RHIC is operating with gold beams only. In this case the luminosity is not limited by head-on beam-beam interactions and compensation is not necessary. The goals of this year’s commissioning efforts are a test of all instrumentation; the demonstration of electron and gold beam overlap; the demonstration of electron beam parameters that are sufficiently stable to have no negative impact on the gold beam lifetime; and the measurement of the tune footprint compression from the beam overlap. With these demonstrations, and a lattice with a phase advance that has a multiple of 180 degrees between the beam-beam interaction and electron lens locations, head-on beam-beam compensation can be commissioned in the following year with proton beams.
	Slides TUYA01 [11.776 MB]
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TUOBA01	Electron Lenses for the Large Hadron Collider	918
	G. Stancari, A. Valishev Fermilab, Batavia, Illinois, USA R. Bruce, S. Redaelli, A. Rossi, B. Salvachua CERN, Geneva, Switzerland
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404. Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in RHIC at BNL. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, hollow electron beam collimation was studied as an option to complement the collimation system for the LHC upgrades. This project is moving towards a technical design in 2014, with the goal to build the devices in 2015-2017, after resuming LHC operations and re-assessing needs and requirements at 6.5 TeV. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles.
	Slides TUOBA01 [9.709 MB]
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TUPRO001	Alternative High Luminosity LHC Matching Section Layout	990
	B. Dalena, A. Chancé CEA/IRFU, Gif-sur-Yvette, France R. De Maria CERN, Geneva, Switzerland J. Payet CEA/DSM/IRFU, France
	Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan. In the framework of the HL-LHC Upgrade project possible variants for the layout of the LHC matching section located in the high luminosity insertions are investigated. This layout is optimized to reduce the demand on the voltage of the crab cavities, it also improves the optics squeeze-ability, both in ATS[1] and non-ATS mode. Moreover the injection and transitions to collision optics are also discussed. [1] S. Fartoukh, ‘’An Achromatic Telescopic Squeezing (ATS) Scheme for LHC Upgrade’’, in proceedings of IPAC11, p. 2088.
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TUPRO002	Fringe Fields Modeling for the High Luminosity LHC Large Aperture Quadrupoles	993
	B. Dalena, A. Chancé, O. Gabouev CEA/IRFU, Gif-sur-Yvette, France R. Appleby, D.R. Brett UMAN, Manchester, United Kingdom R. De Maria, M. Giovannozzi CERN, Geneva, Switzerland J. Payet CEA/DSM/IRFU, France
	Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan. The HL-LHC Upgrade project relies on large aperture magnets (mainly the inner Triplet and the separation dipole D1). The beam is much more sensitive to non-linear perturbations in this region, such as those induced by the fringe fields of the low-beta quadrupoles. Analytical evaluations of detuning with amplitude and chromatic effects show that the effect is small, but not negligible. Therefore, the effect on long-term beam dynamics is evaluated via tracking simulations. Different tracking models are compared in order to provide a numerical estimate of this effect due to the proposed inner triplet quadrupoles. The implementation of the fringe fields in SixTrack, to be used for dynamic apertures studies, is also discussed.
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TUPRO003	Fast Crab Cavity Failures in HL-LHC	997
SUSPSNE004	use link to see paper's listing under its alternate paper code
	B. Yee-Rendón, R. Lopez-Fernandez CINVESTAV, Mexico City, Mexico J. Barranco García EPFL, Lausanne, Switzerland R. Calaga, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland
	Crab cavities (CCs) are a key ingredient of the High-Luminosity Large Hadron Collider (HL-LHC) to ensure head on collisions at the main experiments (ATLAS and CMS) and fully profit from the smaller β* provided by the ATS optics. At KEKB, CCs have exhibited abrupt changes of phase and voltage during a time period of few LHC turns and considering the large energy stored in the HL-LHC beam, CC failures represent a serious risk to the LHC machine protection. In this paper, we discuss the effect of CC voltage or phase changes on a time interval similar to, or longer than, necessary to dump the beam. The simulations assume a realistic steady-state distribution to assess the beam losses for the HL-LHC. Additionally, some strategies are studied to mitigate the damage caused by the failures.
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TUPRO004	Polarized Protons and Deuterons at NICA@JINR	1000
	A.D. Kovalenko, A.V. Butenko, V.D. Kekelidze, V.A. Mikhaylov JINR, Dubna, Moscow Region, Russia Y. Filatov MIPT, Dolgoprudniy, Moscow Region, Russia A.M. Kondratenko, M.A. Kondratenko Science and Technique Laboratory Zaryad, Novosibirsk, Russia
	Different aspects of the NICA facility operation in polarized proton and deuteron modes aimed at reaching the highest possible luminosity and polarization degree as well are analysed. The main aim is to provide average luminosity L ≥ 1•1032 cm^-2 s⁻¹ at √sNN ≥ 26-27 GeV for single-spin proton collisions. Optimal schemes of the Siberian Snake insertions to the Nuclotron and NICA collider rings were proposed. The results of simulations are presented and discussed.
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TUPRO005	Status of the NICA Project at JINR	1003
	G.V. Trubnikov, N.N. Agapov, A.V. Butenko, D.E. Donets, E.D. Donets, E.E. Donets, A.V. Eliseev, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, S.A. Kostromin, A.D. Kovalenko, O.S. Kozlov, V.A. Matveev, I.N. Meshkov, V.A. Mikhailov, V. Monchinsky, N. Shurkhno, A.O. Sidorin, I. Slepnev, V. Slepnev, A.V. Smirnov, A. Sorin, N.D. Topilin, A. Tuzikov, V. Volkov JINR, Dubna, Moscow Region, Russia O.I. Brovko, A.V. Philippov, N.V. Semin JINR/VBLHEP, Moscow, Russia
	Nuclotron-based Ion Collider fAcility (NICA) is the new accelerator complex being constructed in Joint Institute for Nuclear Research. General goal of the project is to provide experimental study of hot and dense strongly interacting QCD matter. The development of NICA injection complex is actively performed. Construction of new 3.2 MeV/u heavy-ion linear accelerator (HILac) is now under way in Germany. Construction of booster has been started. In this report the present status of the NICA accelerator complex are presented.
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TUPRO006	Strong-strong Beam-beam Simulation for the LHC Upgrade	1006
	J. Qiang, S. Paret LBNL, Berkeley, California, USA G. Arduini, T. Pieloni CERN, Geneva, Switzerland J. Barranco García EPFL, Lausanne, Switzerland
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 using computing resources at the NERSC. The LHC upgrade will significantly improve the performance of the current LHC operation with higher collision energy and luminosity. In the paper, we report on the progress in the strong-strong beam-beam simulation of the HL-LHC upgrade with crab cavity compensation. We will present the study of the effects of accelerator tune working points, dipole noise, and crab cavity noise on colliding beam emittance growth.
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TUPRO007	LS1 “First Long Shutdown of LHC and its Injector Chains”	1010
	K. Foraz, S. Baird, M.B.M. Barberan Marin, M. Bernardini, J. Coupard, N. Gilbert, D. Hay, S. Mataguez, D.J. Mcfarlane CERN, Geneva, Switzerland
	The LHC and its injectors were stopped in February 2013, in order to maintain, consolidate and upgrade the different equipment of the accelerator chain, with the goal of achieving LHC operation at the design energy of 14 TeV in the centre-of-mass. Prior to the start of this Long Shutdown (LS1), a major effort of preparation was performed in order to optimize the schedule and the use of resources across the different machines, with the aim of resuming LHC physics in early 2015. The rest of the CERN complex will restart beam operation in the second half of 2014. This paper presents the schedule of LS1, describes the organizational set-up for the coordination of the works, the main activities, the different main milestones, which have been achieved so far, and the decisions taken in order to mitigate the issues encountered.
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TUPRO008	Specification of Field Quality of the Interaction Region Magnets of the High Luminosity LHC Based on Dynamic Aperture	1013
	Y. Nosochkov, Y. Cai, M.-H. Wang SLAC, Menlo Park, California, USA R. De Maria, S.D. Fartoukh, M. Giovannozzi, E. McIntosh CERN, Geneva, Switzerland
	Funding: Work partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404, and by the US LARP through US Department of Energy. The high luminosity LHC upgrade (HL-LHC) requires new magnets in the low-beta interaction regions with a larger aperture than in the existing LHC. These include the Nb3Sn superconducting (SC) inner triplet quadrupoles, Nb-Ti SC separation dipoles D1 and D2, and SC matching quadrupoles Q4 and Q5. The large aperture is necessary for accommodating the increased beam size caused by significantly higher beta functions in these magnets in the collision optics. The high beta functions also enhance the effects of field errors in these magnets leading to a smaller dynamic aperture (DA). It is, therefore, critical to determine the field quality specifications for these magnets which 1) satisfy an acceptable DA, and 2) are realistically achievable. The estimates of expected field quality obtained from magnetic field calculations and measurements were used as a starting point. Then, based on the DA study, the field errors were optimized in order to reach an acceptable DA. The DA calculations were performed using SixTrack. Details of the optimization process and summary of the field quality specifications for collision and injection energies are presented.
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TUPRO009	Simple Models Describing the Time-evolution of Luminosity in Hadron Colliders	1017
	M. Giovannozzi CERN, Geneva, Switzerland
	In recent years, several studies have been performed to describe the evolution of the losses in circular proton machines. Considerations based on single-particle, non-linear beam dynamics allowed building models that, albeit simple, proved to be in good agreement with measurements. These initial results have been generalised, thus opening the possibility to describe the luminosity evolution in a circular hadron collider. In this paper, the focus is on the derivation of scaling laws for the integrated luminosity, taking into account both burn off and additional pseudo-diffusive effects. The proposed models are applied to the analysis of the data collected during the LHC Run I and the outcome is discussed in detail.
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TUPRO010	Origins of Transverse Emittance Blow-up during the LHC Energy Ramp	1021
SUSPSNE003	use link to see paper's listing under its alternate paper code
	M. Kuhn, G. Arduini, V. Kain, A. Langner, Y. Papaphilippou, M. Schaumann, R. Tomás CERN, Geneva, Switzerland
	During LHC Run 1 about 30 % of the potential peak performance was lost due to transverse emittance blow-up through the LHC cycle. Measurements indicated that the majority of the blow-up occurred during the energy ramp. Until the end of LHC Run 1 this emittance blow-up could not be eliminated. In this paper the measurements and observations of emittance growth through the ramp are summarized. Simulation results for growth due to Intra Beam Scattering will be shown and compared to measurements. A summary of investigations of other possible sources will be given and backed up with simulations where possible. Requirements for commissioning the LHC with beam in 2015 after Long Shutdown 1 to understand and control emittance blow-up will be listed.
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TUPRO012	Optimisation and Implementation of the R2E Shielding and Relocation Mitigation Measures at the LHC during the LS1	1027
	A.-L. Perrot, O. Andujar, M.B.M. Barberan Marin, M. Brugger, J.-P. Corso, K. Foraz, M. Jeckel, M. Lazzaroni, B. Lefort, B. Mikulec, Y. Muttoni CERN, Geneva, Switzerland
	In the framework of the Radiation to Electronics (R2E) project, important mitigation actions are being implemented in the LHC during the first Long Shutdown (LS1) to reduce the Single Event Error (SEE) occurrence in standard electronics present in much of the equipment installed in LHC underground areas. Recent simulations have motivated additional actions to be performed in Point 4, in addition to those already scheduled in Points 1, 5, 7 and 8. This paper presents the organisation process carried out during LS1 to optimise the implementation of the R2E mitigation activities. It reports the challenges linked to civil engineering and to safe room relocation in Points 5 and 7. It highlights the reactivity needed to face the new mitigation requirements to be implemented in Point 4 before the end of LS1. It presents the advancement status of the R2E mitigation activities in the different LHC points with the main concerns and impact with the overall LHC LS1 planning.
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TUPRO013	Studies on Stochastic Cooling of Heavy Ions in the LHC	1030
	M. Schaumann, J.M. Jowett, B. Salvant, M. Wendt CERN, Geneva, Switzerland M. Blaskiewicz, S. Verdú-Andrés BNL, Upton, Long Island, New York, USA
	Future high luminosity heavy-ion operation of the LHC will be dominated by very rapid luminosity decay due to the large collision cross-section and, to a lesser extent, emittance growth from intra-beam scattering (IBS) due to the high bunch intensities. A stochastic cooling system could reduce the emittance far below its initial value and reduce the losses from debunching during collisions, allowing more of the initial beam intensity to be converted into integrated luminosity before the beams are dumped. We review the status of this proposal, system and hardware properties and potential locations for the equipment in the tunnel.
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TUPRO014	Semi-empirical Model for Optimising Future Heavy Ion Luminosity of the LHC	1033
	M. Schaumann CERN, Geneva, Switzerland
	The wide spectrum of intensities and emittances imprinted on the LHC Pb bunches during the accumulation of bunch trains in the injector chain result in a significant spread in the single bunch luminosities and lifetimes in collision. Based on the data collected in the 2011 Pb-Pb run, an empirical model is derived to predict the single-bunch peak luminosity depending on the bunch's position within the beam. In combination with this model, simulations of representative bunches are used to estimate the luminosity evolution for the complete ensemble of bunches. Several options are being considered to improve the injector performance and to increase the number of bunches in the LHC, leading to several potential injection scenarios, resulting in different peak and integrated luminosities. The most important options for after the long shutdown 1 and 2 are evaluated and compared.
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TUPRO015	Update on Predictions for Yearly Integrated Luminosity for HL-LHC based on Expected Machine Availability	1036
	A. Apollonio, M. Jonker, R. Schmidt, B. Todd, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	Machine availability is one of the key performance indicators to reach the ambitious goals for integrated luminosity in the post Long Shutdown 1 (LS1) era. Machine availability is even more important for the future High Luminosity LHC (HL-LHC) [1]. In this paper a Monte Carlo approach has been used to predict integrated luminosity as a function of LHC machine availability. The baseline model assumptions such as fault-time distributions and machine failure rate (number of fills with stable beams dumped after a failure / total number of fills with stable beams) were deduced from the observations during LHC operation in 2012. The predictions focus on operation after LS1 and its evolution towards HL-LHC. The extrapolation of relevant parameters impacting on machine availability is outlined and their corresponding impact on fault time distributions is discussed. Results for possible future operational scenarios are presented. Finally, a sensitivity analysis with relevant model parameters like fault time and machine failure rate is discussed.
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TUPRO016	Machine Protection Challenges for HL-LHC	1039
	R. Schmidt, T. Bär, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	LHC operation requires the flawless functioning of the machine protection systems. The energy stored in the beam was progressively increased beyond the 140 MJ range at the end of 2012 at 4 TeV/c. The further increase to 364 MJ expected for 2015 at 6.5 TeV/c should be possible with the existing protection systems. For HL-LHC, additional failure modes are considered. The stored beam energy will increase by another factor of two with respect to nominal and a factor of five more than experienced so far. The maximum beta function will increase. It is planned to install crab cavities in the LHC. With crab cavities, sudden voltage decays within 100 us after e.g. cavity quenches lead to large beam oscillations. Tracking simulations predict trajectory distortions of up to 1.5 σ in the first turn after a sudden drop of the deflecting voltage in a single cavity within 3 turns. The energy of several MJ stored in halo protons that could hit the collimator in case of such events is far above damage level, even if the collimator jaws are made of robust material. In this paper we discuss the challenges for machine protection in the HL-LHC era and possible mitigation strategies.
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TUPRO017	HL-LHC Performance with a 200 MHz RF System	1043
	R. Tomás, C.O. Domínguez CERN, Geneva, Switzerland S.M. White BNL, Upton, Long Island, New York, USA
	The HL-LHC performance could considerably benefit from having a 200 MHz RF system. This would allow to inject longer bunches with larger bunch intensity from the SPS and to perform bunch length leveling if required. We also consider the possibility of decreasing the crab cavity frequency to increase both virtual peak luminosity and luminous region. Performance estimates of various configurations are presented in this paper.
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TUPRO018	Prospects for the LHC Optics Measurements and Corrections at Higher Energy	1046
	R. Tomás, T. Bach, J.M. Coello de Portugal, V. Kain, M. Kuhn, A. Langner, Y.I. Levinsen, K.S.B. Li, E.H. Maclean, N. Magnin, V. Maier, M. McAteer, T. Persson, P.K. Skowroński, R. Westenberger CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom S.M. White BNL, Upton, Long Island, New York, USA
	LHC will resume operation in 2015 at 6.5 TeV. The higher energy allows for smaller IP beta functions, further enhancing the optics errors in the triplet quadrupoles. Moreover the uncertainty in the calibration of some quadrupoles will slightly increase due to saturation effects. The complete magnetic cycle of the LHC will take longer due to the higher energy and extended squeeze sequence. All these issues require more precise and more efficient optics measurements and corrections to guarantee the same optics quality level as in 2012 when a 7% peak beta-beating was achieved. This paper summarizes the on-going efforts for achieving faster and more accurate optics measurements and corrections.
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TUPRO020	Integration of a Neutral Absorber for the LHC Point 8	1052
	A. Santamaría García, R. Alemany-Fernández, H. Burkhardt, F. Cerutti, L.S. Esposito, N.V. Shetty CERN, Geneva, Switzerland
	The LHCb detector will be upgraded during the second long shutdown (LS2) of the LHC machine, in order to increase its statistical precision significantly. The upgraded LHCb foresees a peak luminosity of L = 1-2 . 10³³ cm^-2 s⁻¹, with a pileup of 5. This represents ten times more luminosity and five times more pile up than in the present LHC. With these conditions, the pp-collisions and beam losses will produce a non-negligeable beam-induced energy deposition in the interaction region. More precisely, studies have shown that the energy deposition will especially increase on the D2 recombination dipole, which could bring them close to their safety thresholds. To avoid this, the placement of a minimal neutral absorber has been proposed. This absorber will have the same role as the TAN in the high luminosity Interaction Regions (IR) 1 and 5. This study shows the possible dimensions and location of this absorber, and how it would reduce both the peak power density and total heat load.
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TUPRO021	Preliminary Study of Risks and Failure Scenarios for the High Luminosity Experiments in HL-LHC	1055
	F. Bouly LPSC, Grenoble Cedex, France R. Alemany-Fernández, H. Burkhardt, D. Wollmann CERN, Geneva, Switzerland B. Yee-Rendón CINVESTAV, Mexico City, Mexico
	For the HL-LHC it is planned to basically double the diameter of the triplet quadruple magnets around the high luminosity insertions of the LHC. The high luminosity experiments ATLAS and CMS would like to keep a small central chamber radius close the interaction point. In the context of collider-experiment studies for the high-luminosity upgrade of the LHC, we present a first study of the possible consequences of these changes for the experimental running conditions based on detailed simulations with tracking. We have started to implement crab cavity failures and discuss first results from these simulations.
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TUPRO023	Beam-beam Effects in Different Luminosity Levelling Scenarios for the LHC	1061
SUSPSNE001	use link to see paper's listing under its alternate paper code
	X. Buffat, D. Banfi, G.R. Coombs EPFL, Lausanne, Switzerland W. Herr, T. Pieloni CERN, Geneva, Switzerland
	Adjusting luminosity and optimizing the luminous region in each interaction point of the LHC according to the experiments needs has become a requirement to maximize the efficiency of the different detectors. Several techniques are envisaged, most importantly by varying β* or a transverse offset at the interaction point. Coherent and incoherent stability in the presence of beam-beam effects will be discussed in realistic luminosity levelling scenarios for the LHC.
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TUPRO024	Benchmarking Studies of Intra Beam Scattering for HL-LHC	1064
	D. Angal-Kalinin STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A. Wolski The University of Liverpool, Liverpool, United Kingdom A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404 The effects of Intra Beam Scattering (IBS) in the High Luminosity upgrade of the LHC (HL-LHC) will be stronger compared to effects in the present LHC because of the high intensity of the proton bunches and the new proposed optics. We present benchmarking studies carried out for the present LHC at injection and collision energies as well as HL-LHC at collision energy with the Achromatic Telescopic Squeezing optics. The results of IBS growth-rate calculations using the full Bjorken-Mtingwa formulae* are compared with simplified formulae, Bane’s high energy approximation, and the completely integrated modified Piwinski approximation**. The results of calculations based on these methods carried out in Mathematica are compared with results from the codes MAD-X and ZAP. J. Broken and S. Mtingwa, Part. Accel. 13, 115 (1983) K. Kubo et al, PRST-AB, 8, 081001 (2005) * K. Bane, EPAC2002 **** S. Mtingwa and A. Tollestrup, Fermilab-Pub-89/224, 1987.
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TUPRO025	Initial Estimate of Fringe Field Effects in HL-LHC using Frequency Map Analysis	1067
SUSPSNE002	use link to see paper's listing under its alternate paper code
	S. Jones, D. Newton, A. Wolski The University of Liverpool, Liverpool, United Kingdom S. Jones, D. Newton, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: Work supported by the Science and Technology Facilities Council, UK The planned High Luminosity upgrade to the LHC will require stronger focusing of the beam in the interaction regions. To achieve this, the inner triplet quadrupoles will be replaced with new magnets having larger gradient and aperture. In this new focusing regime the quadrupole fringe fields are expected to have a greater effect on the beam dynamics, due to their large aperture, as compared to the nominal LHC. In this preliminary study, simplified models are used in a tracking code to assess the impact of the fringe fields on the dynamics using frequency map analysis.
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TUPRO026	Possible Beam-beam and Levelling Scenarios for HL-LHC	1071
	M.P. Crouch, R. Appleby UMAN, Manchester, United Kingdom B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom T. Pieloni CERN, Geneva, Switzerland
	Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404 The upgrade of the LHC from the current set-up to high luminosity performances will provide new challenges from the point of view of beam-beam as well as other collective effects and luminosity levelling. We present the current possibilities for doing luminosity levelling for HL-LHC. We explore the merits and drawbacks of each option and briefly discuss the operational implications. The simplest option being levelling with an offset between the two beams. In particular, we look at the possibility of using flat beams in the IPs for all the available options and investigate their benefits and drawbacks, using the code COMBI. Flat beams would allow an additional degree of freedom, with the levelling only required in one of the planes at any given IP. To this end, various scenarios are looked at, both with and without crab cavities.
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TUPRO027	First Beam Background Simulation Studies at IR1 for High Luminosity LHC	1074
	R. Kwee-Hinzmann, S.M. Gibson JAI, Egham, Surrey, United Kingdom G. Bregliozzi, R. Bruce, F. Cerutti, L.S. Esposito, R. Kersevan, A. Lechner, N.V. Shetty CERN, Geneva, Switzerland S.M. Gibson Royal Holloway, University of London, Surrey, United Kingdom
	In the High-Luminosity Large Hadron Collider (HL-LHC) Project, the LHC will be significantly upgraded to attain a peak luminosity of up to 8.5 × 10³⁴ cm^-2s^-1, thus almost an order of magnitude higher compared to the nominal machine configuration in ATLAS at IP1 and CMS at IP5. In the view of a successful machine setup as well as a successful physics programme, beam induced background studies at IP1 were performed to investigate sources of particle fluxes to the experimental area. In particular as a start of the study, two sources forming the major contributions were simulated in detail: the first one considers inelastic interactions from beam particles hitting tertiary collimators, the second one from beam interactions with residual gas-molecules in the vacuum pipe close by the experiment, referred to as beam-halo and local beam-gas, respectively. We will present these first HL-LHC background studies based on SixTrack and FLUKA simulations, highlighting the simulation setup for the design case in the HL-LHC scenario. Results of particle spectra entering the ATLAS detector region are presented for the latest study version of HL-LHC machine layout (2013).
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TUPRO028	Energy Deposition Studies for the Hi-Lumi LHC Inner Triplet Magnets	1078
	N.V. Mokhov, I.L. Rakhno, S.I. Striganov, I.S. Tropin Fermilab, Batavia, Illinois, USA F. Cerutti, L.S. Esposito, A. Lechner CERN, Geneva, Switzerland
	Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy through the US LARP Program, and by the High Luminosity LHC project. After operation at the nominal luminosity, the LHC is planned to be upgraded to a 5-fold increased luminosity of 5×1034 cm^-2s⁻¹. The upgrade includes replacement of the IP1/IP5 inner triplet 70-mm NbTi quadrupoles with the 150-mm coil aperture Nb3Sn quadrupoles along with the new 150-mm coil aperture NbTi dipole magnet. A detailed model of the region with these new magnets, field maps, corrector packages, segmented tungsten inner absorbers was built and implemented into the FLUKA and MARS codes. Various aspects of the new design were studied: (i) thicknesses of tungsten absorbers; (ii) beam screen interruption in interconnects; (iii) crossing angle value and orientation, etc. In the optimized configuration, the peak power density averaged over the magnet inner cable width doesn’t exceed 2 mW/cm³, safely below the quench limit. For the integrated luminosity of 3000 fb-1, the highest peak dose of 35 MGy occurs in the corrector package CP, while for other magnets, the peak dose in the innermost insulators ranges from 20 to 30 MGy. Dynamic heat loads to the triplet magnet cold mass are calculated to be on a target 10 W/m level. FLUKA and MARS results agree within 10%.
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TUPRO031	RHIC Performance during the 7.5 GeV Low Energy Run in FY 2014	1087
	C. Montag, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, W. Fischer, C.J. Gardner, X. Gu, M. Harvey, T. Hayes, H. Huang, R.L. Hulsart, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, S. Nemesure, J. Piacentino, P.H. Pile, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, J.E. Tuozzolo, M. Wilinski, K. Yip, A. Zaltsman, K. Zeno, W. Zhang 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. As the last missing step in phase 1 of the beam energy scan (BES-I), aimed at the search for the critical point in the QCD phase diagram, RHIC collided gold ions at a beam energy of 7.3 GeV/nucleon during the FY 2014 run. While this particular energy is close to the nominal RHIC injection energy of 9.8 GeV/nucleon, it is nevertheless challenging because it happens to be close to the AGS transition energy, which makes longitudinal beam dynamics during transfer from the AGS to RHIC difficult. We report on machine performance, obstacles and solutions during the FY 2014 low energy run.
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TUPRO032	RHIC Performance for FY2014 Heavy Ion Run	1090
	G. Robert-Demolaize, J.G. Alessi, M. Bai, E.N. Beebe, J. Beebe-Wang, S.A. Belomestnykh, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, J.J. Butler, R. Connolly, T. D'Ottavio, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, M. Harvey, T. Hayes, H. Huang, P.F. Ingrassia, J.P. Jamilkowski, 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, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, A.I. Pikin, P.H. Pile, V. Ptitsyn, D. Raparia, T. Roser, P. Sampson, J. Sandberg, V. Schoefer, C. Schultheiss, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, J.E. Tuozzolo, B. Van Kuik, M. Wilinski, Q. Wu, A. Zaltsman, K. Zeno, W. Zhang 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. After running uranium-uranium and copper-gold collisions in 2012, the high energy heavy ion run of the Relativistic Heavy Ion Collider (RHIC) for Fiscal Year 14 (Run14) is back to gold-gold (Au-Au) collisions at 100 GeV/nucleon. Following the level of performance achieved in Run12, RHIC is still looking to push both instantaneous and integrated luminosity goals. To that end, a new 56 MHz superconducting RF cavity was installed and commissioned, designed to keep ions in one RF bucket and improve luminosity by allowing a smaller beta function at the interaction point (IP) due to a reduced hourglass effect. The following presents an overview of these changes and reviews the performance of the collider.
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TUPRO034	Beam-beam Interaction in the Asymmetric Energy Gold-gold Collision in RHIC	1093
	Y. Luo, M. Blaskiewicz, M.R. Costanzo, W. Fischer, X. Gu, V.H. Ranjbar, S.M. White 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. In this article, we study the beam-beam interaction in the possible future gold-gold collision with different particle energies in the Relativistic Heavy Ion Collider (RHIC). With different particle energies, the center-of-mass of collision is moving in the longitudinal direction during collision. Since the RF harmonic numbers are different for the two RHIC rings, bunches collide in 110 turns followed by 10 turns without collision. In this study, the stability of particles and the beam emittance growth are calculated through numeric simulations based on a 6-D weak-strong beam-beam interaction model.
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TUPME027	Analysis of the Electron Cloud Observations with 25 ns Bunch Spacing at the LHC	1410
	G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy G. Arduini, V. Baglin, D. Banfi, H. Bartosik, S.D. Claudet, C.O. Domínguez, J.F. Esteban Müller, G. Iadarola, T. Pieloni, G. Rumolo, E.N. Shaposhnikova, L.J. Tavian, C. Zannini, F. Zimmermann CERN, Geneva, Switzerland
	Electron Cloud (EC) effects have been identified as a major performance limitation for the Large Hadron Collider (LHC) when operating with the nominal bunch spacing of 25 ns. During the LHC Run 1 (2010 - 2013) the luminosity production mainly used beams with 50 ns spacing, while 25 ns beams were only employed for short periods in 2011 and 2012 for test purposes. On these occasions, observables such as pressure rise, heat load in the cold sections as well as clear signatures on bunch-by-bunch emittance blow up, particle loss and energy loss indicated the presence of an EC in a large portion of the LHC. The analysis of the recorded data, together with EC build up simulations, has led to a significant improvement of our understanding of the EC effect in the different components of the LHC. Studies were carried out both at injection energy (450 GeV) and at top energy (4 TeV) aiming at determining the energy dependence of the EC formation and its impact on the quality of the proton beam.
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TUPRI014	Modelling and Long Term Dynamics of Crab Cavities in the LHC	1578
	R. Appleby, D.R. Brett UMAN, Manchester, United Kingdom J. Barranco García, R. De Maria, A. Grudiev, R. Tomás CERN, Geneva, Switzerland
	Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan. The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) aims to achieve an integrated luminosity of 250-300 fb-1 per year. This upgrade includes the use crab cavities to mitigate the geometric loss of luminosity arising from the beam crossing angle. The tight space constraints at the location of the cavities leads to cavity designs which are axially non-symmetric and have a potentially significant effect on the long term dynamics and dynamic aperture of the LHC. In this paper we present the current status of advanced modelling of crab cavities.
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TUPRI022	Beam-Beam Studies in LHC- Beam Loss and Bunch Shortening	1603
	K. Ohmi KEK, Ibaraki, Japan
	In Hadron colliders, luminosity degrade various mechanism. Beam-beam related emittance growth is caused by resonances induced by crossing angle. Tune spread due to chromaticity enhances the resonances effect. A bunch shortening phenomenon related to beam-beam interaction has been observed in LHC. The bunch length has an anti-correlation with transverse emittance. This phenomenon has been studied using a weak-strong beam-beam simulation (BBWS code).
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Paper

Title

Page

Challenges for Highest Energy Circular Colliders

1

F. Zimmermann, M. Benedikt, D. Schulte, J. Wenninger
CERN, Geneva, Switzerland

A new tunnel of 80-100 km circumference could host a 100 TeV centre-of-mass energy-frontier proton collider (FCC-hh/VHE-LHC), with a circular lepton collider (FCC-ee/TLEP) as potential intermediate step, and a lepton-hadron collider (FCC-he) as additional option. FCC-ee, operating at four different energies for precision physics of the Z, W, and Higgs boson and the top quark, represents a significant push in terms of technology and design parameters. Pertinent R&D efforts include the RF system, top-up injection scheme, optics design for arcs and final focus, effects of beamstrahlung, beam polarization, energy calibration, and power consumption. FCC-hh faces other challenges, such as high-field magnet design, machine protection and effective handling of large synchrotron radiation power in a superconducting machine. All these issues are being addressed by a global FCC collaboration. A parallel design study in China prepares for a similar, but smaller collider, called CepC/SppC.

Slides MOXAA01 [27.493 MB]

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TUYA01

First Experience with Electron Lenses for Beam-beam Compensation in RHIC

913

W. Fischer, Z. Altinbas, D. Bruno, M.R. Costanzo, X. Gu, J. Hock, A.K. Jain, Y. Luo, C. Mi, R.J. Michnoff, T.A. Miller, A.I. Pikin, T. Samms, Y. Tan, R. Than, P. Thieberger, S.M. White
BNL, Upton, Long Island, New York, USA

Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The head-on beam-beam interaction is the dominant luminosity limiting effect in polarized proton operation in RHIC. To mitigate this effect two electron lenses were installed in the two RHIC rings. We summarize the hardware and electron beam commissioning results to date, and report on the first experience with the electron-hadron beam interaction. In 2014 RHIC is operating with gold beams only. In this case the luminosity is not limited by head-on beam-beam interactions and compensation is not necessary. The goals of this year’s commissioning efforts are a test of all instrumentation; the demonstration of electron and gold beam overlap; the demonstration of electron beam parameters that are sufficiently stable to have no negative impact on the gold beam lifetime; and the measurement of the tune footprint compression from the beam overlap. With these demonstrations, and a lattice with a phase advance that has a multiple of 180 degrees between the beam-beam interaction and electron lens locations, head-on beam-beam compensation can be commissioned in the following year with proton beams.

Slides TUYA01 [11.776 MB]

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TUOBA01

Electron Lenses for the Large Hadron Collider

918

G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA
R. Bruce, S. Redaelli, A. Rossi, B. Salvachua
CERN, Geneva, Switzerland

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404.
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in RHIC at BNL. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, hollow electron beam collimation was studied as an option to complement the collimation system for the LHC upgrades. This project is moving towards a technical design in 2014, with the goal to build the devices in 2015-2017, after resuming LHC operations and re-assessing needs and requirements at 6.5 TeV. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles.

Slides TUOBA01 [9.709 MB]

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TUPRO001

Alternative High Luminosity LHC Matching Section Layout

990

B. Dalena, A. Chancé
CEA/IRFU, Gif-sur-Yvette, France
R. De Maria
CERN, Geneva, Switzerland
J. Payet
CEA/DSM/IRFU, France

Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan.
In the framework of the HL-LHC Upgrade project possible variants for the layout of the LHC matching section located in the high luminosity insertions are investigated. This layout is optimized to reduce the demand on the voltage of the crab cavities, it also improves the optics squeeze-ability, both in ATS[1] and non-ATS mode. Moreover the injection and transitions to collision optics are also discussed. [1] S. Fartoukh, ‘’An Achromatic Telescopic Squeezing (ATS) Scheme for LHC Upgrade’’, in proceedings of IPAC11, p. 2088.

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TUPRO002

Fringe Fields Modeling for the High Luminosity LHC Large Aperture Quadrupoles

993

B. Dalena, A. Chancé, O. Gabouev
CEA/IRFU, Gif-sur-Yvette, France
R. Appleby, D.R. Brett
UMAN, Manchester, United Kingdom
R. De Maria, M. Giovannozzi
CERN, Geneva, Switzerland
J. Payet
CEA/DSM/IRFU, France

Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan.
The HL-LHC Upgrade project relies on large aperture magnets (mainly the inner Triplet and the separation dipole D1). The beam is much more sensitive to non-linear perturbations in this region, such as those induced by the fringe fields of the low-beta quadrupoles. Analytical evaluations of detuning with amplitude and chromatic effects show that the effect is small, but not negligible. Therefore, the effect on long-term beam dynamics is evaluated via tracking simulations. Different tracking models are compared in order to provide a numerical estimate of this effect due to the proposed inner triplet quadrupoles. The implementation of the fringe fields in SixTrack, to be used for dynamic apertures studies, is also discussed.

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TUPRO003

Fast Crab Cavity Failures in HL-LHC

997

SUSPSNE004

use link to see paper's listing under its alternate paper code

B. Yee-Rendón, R. Lopez-Fernandez
CINVESTAV, Mexico City, Mexico
J. Barranco García
EPFL, Lausanne, Switzerland
R. Calaga, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland

Crab cavities (CCs) are a key ingredient of the High-Luminosity Large Hadron Collider (HL-LHC) to ensure head on collisions at the main experiments (ATLAS and CMS) and fully profit from the smaller β* provided by the ATS optics. At KEKB, CCs have exhibited abrupt changes of phase and voltage during a time period of few LHC turns and considering the large energy stored in the HL-LHC beam, CC failures represent a serious risk to the LHC machine protection. In this paper, we discuss the effect of CC voltage or phase changes on a time interval similar to, or longer than, necessary to dump the beam. The simulations assume a realistic steady-state distribution to assess the beam losses for the HL-LHC. Additionally, some strategies are studied to mitigate the damage caused by the failures.

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TUPRO004

Polarized Protons and Deuterons at NICA@JINR

1000

A.D. Kovalenko, A.V. Butenko, V.D. Kekelidze, V.A. Mikhaylov
JINR, Dubna, Moscow Region, Russia
Y. Filatov
MIPT, Dolgoprudniy, Moscow Region, Russia
A.M. Kondratenko, M.A. Kondratenko
Science and Technique Laboratory Zaryad, Novosibirsk, Russia

Different aspects of the NICA facility operation in polarized proton and deuteron modes aimed at reaching the highest possible luminosity and polarization degree as well are analysed. The main aim is to provide average luminosity L ≥ 1•1032 cm^-2 s⁻¹ at √sNN ≥ 26-27 GeV for single-spin proton collisions. Optimal schemes of the Siberian Snake insertions to the Nuclotron and NICA collider rings were proposed. The results of simulations are presented and discussed.

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TUPRO005

Status of the NICA Project at JINR

1003

G.V. Trubnikov, N.N. Agapov, A.V. Butenko, D.E. Donets, E.D. Donets, E.E. Donets, A.V. Eliseev, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, S.A. Kostromin, A.D. Kovalenko, O.S. Kozlov, V.A. Matveev, I.N. Meshkov, V.A. Mikhailov, V. Monchinsky, N. Shurkhno, A.O. Sidorin, I. Slepnev, V. Slepnev, A.V. Smirnov, A. Sorin, N.D. Topilin, A. Tuzikov, V. Volkov
JINR, Dubna, Moscow Region, Russia
O.I. Brovko, A.V. Philippov, N.V. Semin
JINR/VBLHEP, Moscow, Russia

Nuclotron-based Ion Collider fAcility (NICA) is the new accelerator complex being constructed in Joint Institute for Nuclear Research. General goal of the project is to provide experimental study of hot and dense strongly interacting QCD matter. The development of NICA injection complex is actively performed. Construction of new 3.2 MeV/u heavy-ion linear accelerator (HILac) is now under way in Germany. Construction of booster has been started. In this report the present status of the NICA accelerator complex are presented.

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TUPRO006

Strong-strong Beam-beam Simulation for the LHC Upgrade

1006

J. Qiang, S. Paret
LBNL, Berkeley, California, USA
G. Arduini, T. Pieloni
CERN, Geneva, Switzerland
J. Barranco García
EPFL, Lausanne, Switzerland

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 using computing resources at the NERSC.
The LHC upgrade will significantly improve the performance of the current LHC operation with higher collision energy and luminosity. In the paper, we report on the progress in the strong-strong beam-beam simulation of the HL-LHC upgrade with crab cavity compensation. We will present the study of the effects of accelerator tune working points, dipole noise, and crab cavity noise on colliding beam emittance growth.

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TUPRO007

LS1 “First Long Shutdown of LHC and its Injector Chains”

1010

K. Foraz, S. Baird, M.B.M. Barberan Marin, M. Bernardini, J. Coupard, N. Gilbert, D. Hay, S. Mataguez, D.J. Mcfarlane
CERN, Geneva, Switzerland

The LHC and its injectors were stopped in February 2013, in order to maintain, consolidate and upgrade the different equipment of the accelerator chain, with the goal of achieving LHC operation at the design energy of 14 TeV in the centre-of-mass. Prior to the start of this Long Shutdown (LS1), a major effort of preparation was performed in order to optimize the schedule and the use of resources across the different machines, with the aim of resuming LHC physics in early 2015. The rest of the CERN complex will restart beam operation in the second half of 2014. This paper presents the schedule of LS1, describes the organizational set-up for the coordination of the works, the main activities, the different main milestones, which have been achieved so far, and the decisions taken in order to mitigate the issues encountered.

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TUPRO008

Specification of Field Quality of the Interaction Region Magnets of the High Luminosity LHC Based on Dynamic Aperture

1013

Y. Nosochkov, Y. Cai, M.-H. Wang
SLAC, Menlo Park, California, USA
R. De Maria, S.D. Fartoukh, M. Giovannozzi, E. McIntosh
CERN, Geneva, Switzerland

Funding: Work partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404, and by the US LARP through US Department of Energy.
The high luminosity LHC upgrade (HL-LHC) requires new magnets in the low-beta interaction regions with a larger aperture than in the existing LHC. These include the Nb3Sn superconducting (SC) inner triplet quadrupoles, Nb-Ti SC separation dipoles D1 and D2, and SC matching quadrupoles Q4 and Q5. The large aperture is necessary for accommodating the increased beam size caused by significantly higher beta functions in these magnets in the collision optics. The high beta functions also enhance the effects of field errors in these magnets leading to a smaller dynamic aperture (DA). It is, therefore, critical to determine the field quality specifications for these magnets which 1) satisfy an acceptable DA, and 2) are realistically achievable. The estimates of expected field quality obtained from magnetic field calculations and measurements were used as a starting point. Then, based on the DA study, the field errors were optimized in order to reach an acceptable DA. The DA calculations were performed using SixTrack. Details of the optimization process and summary of the field quality specifications for collision and injection energies are presented.

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TUPRO009

Simple Models Describing the Time-evolution of Luminosity in Hadron Colliders

1017

M. Giovannozzi
CERN, Geneva, Switzerland

In recent years, several studies have been performed to describe the evolution of the losses in circular proton machines. Considerations based on single-particle, non-linear beam dynamics allowed building models that, albeit simple, proved to be in good agreement with measurements. These initial results have been generalised, thus opening the possibility to describe the luminosity evolution in a circular hadron collider. In this paper, the focus is on the derivation of scaling laws for the integrated luminosity, taking into account both burn off and additional pseudo-diffusive effects. The proposed models are applied to the analysis of the data collected during the LHC Run I and the outcome is discussed in detail.

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TUPRO010

Origins of Transverse Emittance Blow-up during the LHC Energy Ramp

1021

SUSPSNE003

use link to see paper's listing under its alternate paper code

M. Kuhn, G. Arduini, V. Kain, A. Langner, Y. Papaphilippou, M. Schaumann, R. Tomás
CERN, Geneva, Switzerland

During LHC Run 1 about 30 % of the potential peak performance was lost due to transverse emittance blow-up through the LHC cycle. Measurements indicated that the majority of the blow-up occurred during the energy ramp. Until the end of LHC Run 1 this emittance blow-up could not be eliminated. In this paper the measurements and observations of emittance growth through the ramp are summarized. Simulation results for growth due to Intra Beam Scattering will be shown and compared to measurements. A summary of investigations of other possible sources will be given and backed up with simulations where possible. Requirements for commissioning the LHC with beam in 2015 after Long Shutdown 1 to understand and control emittance blow-up will be listed.

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TUPRO012

Optimisation and Implementation of the R2E Shielding and Relocation Mitigation Measures at the LHC during the LS1

1027

A.-L. Perrot, O. Andujar, M.B.M. Barberan Marin, M. Brugger, J.-P. Corso, K. Foraz, M. Jeckel, M. Lazzaroni, B. Lefort, B. Mikulec, Y. Muttoni
CERN, Geneva, Switzerland

In the framework of the Radiation to Electronics (R2E) project, important mitigation actions are being implemented in the LHC during the first Long Shutdown (LS1) to reduce the Single Event Error (SEE) occurrence in standard electronics present in much of the equipment installed in LHC underground areas. Recent simulations have motivated additional actions to be performed in Point 4, in addition to those already scheduled in Points 1, 5, 7 and 8. This paper presents the organisation process carried out during LS1 to optimise the implementation of the R2E mitigation activities. It reports the challenges linked to civil engineering and to safe room relocation in Points 5 and 7. It highlights the reactivity needed to face the new mitigation requirements to be implemented in Point 4 before the end of LS1. It presents the advancement status of the R2E mitigation activities in the different LHC points with the main concerns and impact with the overall LHC LS1 planning.

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TUPRO013

Studies on Stochastic Cooling of Heavy Ions in the LHC

1030

M. Schaumann, J.M. Jowett, B. Salvant, M. Wendt
CERN, Geneva, Switzerland
M. Blaskiewicz, S. Verdú-Andrés
BNL, Upton, Long Island, New York, USA

Future high luminosity heavy-ion operation of the LHC will be dominated by very rapid luminosity decay due to the large collision cross-section and, to a lesser extent, emittance growth from intra-beam scattering (IBS) due to the high bunch intensities. A stochastic cooling system could reduce the emittance far below its initial value and reduce the losses from debunching during collisions, allowing more of the initial beam intensity to be converted into integrated luminosity before the beams are dumped. We review the status of this proposal, system and hardware properties and potential locations for the equipment in the tunnel.

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TUPRO014

Semi-empirical Model for Optimising Future Heavy Ion Luminosity of the LHC

1033

M. Schaumann
CERN, Geneva, Switzerland

The wide spectrum of intensities and emittances imprinted on the LHC Pb bunches during the accumulation of bunch trains in the injector chain result in a significant spread in the single bunch luminosities and lifetimes in collision. Based on the data collected in the 2011 Pb-Pb run, an empirical model is derived to predict the single-bunch peak luminosity depending on the bunch's position within the beam. In combination with this model, simulations of representative bunches are used to estimate the luminosity evolution for the complete ensemble of bunches. Several options are being considered to improve the injector performance and to increase the number of bunches in the LHC, leading to several potential injection scenarios, resulting in different peak and integrated luminosities. The most important options for after the long shutdown 1 and 2 are evaluated and compared.

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TUPRO015

Update on Predictions for Yearly Integrated Luminosity for HL-LHC based on Expected Machine Availability

1036

A. Apollonio, M. Jonker, R. Schmidt, B. Todd, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

Machine availability is one of the key performance indicators to reach the ambitious goals for integrated luminosity in the post Long Shutdown 1 (LS1) era. Machine availability is even more important for the future High Luminosity LHC (HL-LHC) [1]. In this paper a Monte Carlo approach has been used to predict integrated luminosity as a function of LHC machine availability. The baseline model assumptions such as fault-time distributions and machine failure rate (number of fills with stable beams dumped after a failure / total number of fills with stable beams) were deduced from the observations during LHC operation in 2012. The predictions focus on operation after LS1 and its evolution towards HL-LHC. The extrapolation of relevant parameters impacting on machine availability is outlined and their corresponding impact on fault time distributions is discussed. Results for possible future operational scenarios are presented. Finally, a sensitivity analysis with relevant model parameters like fault time and machine failure rate is discussed.

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TUPRO016

Machine Protection Challenges for HL-LHC

1039

R. Schmidt, T. Bär, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

LHC operation requires the flawless functioning of the machine protection systems. The energy stored in the beam was progressively increased beyond the 140 MJ range at the end of 2012 at 4 TeV/c. The further increase to 364 MJ expected for 2015 at 6.5 TeV/c should be possible with the existing protection systems. For HL-LHC, additional failure modes are considered. The stored beam energy will increase by another factor of two with respect to nominal and a factor of five more than experienced so far. The maximum beta function will increase. It is planned to install crab cavities in the LHC. With crab cavities, sudden voltage decays within 100 us after e.g. cavity quenches lead to large beam oscillations. Tracking simulations predict trajectory distortions of up to 1.5 σ in the first turn after a sudden drop of the deflecting voltage in a single cavity within 3 turns. The energy of several MJ stored in halo protons that could hit the collimator in case of such events is far above damage level, even if the collimator jaws are made of robust material. In this paper we discuss the challenges for machine protection in the HL-LHC era and possible mitigation strategies.

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TUPRO017

HL-LHC Performance with a 200 MHz RF System

1043

R. Tomás, C.O. Domínguez
CERN, Geneva, Switzerland
S.M. White
BNL, Upton, Long Island, New York, USA

The HL-LHC performance could considerably benefit from having a 200 MHz RF system. This would allow to inject longer bunches with larger bunch intensity from the SPS and to perform bunch length leveling if required. We also consider the possibility of decreasing the crab cavity frequency to increase both virtual peak luminosity and luminous region. Performance estimates of various configurations are presented in this paper.

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TUPRO018

Prospects for the LHC Optics Measurements and Corrections at Higher Energy

1046

R. Tomás, T. Bach, J.M. Coello de Portugal, V. Kain, M. Kuhn, A. Langner, Y.I. Levinsen, K.S.B. Li, E.H. Maclean, N. Magnin, V. Maier, M. McAteer, T. Persson, P.K. Skowroński, R. Westenberger
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom
S.M. White
BNL, Upton, Long Island, New York, USA

LHC will resume operation in 2015 at 6.5 TeV. The higher energy allows for smaller IP beta functions, further enhancing the optics errors in the triplet quadrupoles. Moreover the uncertainty in the calibration of some quadrupoles will slightly increase due to saturation effects. The complete magnetic cycle of the LHC will take longer due to the higher energy and extended squeeze sequence. All these issues require more precise and more efficient optics measurements and corrections to guarantee the same optics quality level as in 2012 when a 7% peak beta-beating was achieved. This paper summarizes the on-going efforts for achieving faster and more accurate optics measurements and corrections.

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TUPRO020

Integration of a Neutral Absorber for the LHC Point 8

1052

A. Santamaría García, R. Alemany-Fernández, H. Burkhardt, F. Cerutti, L.S. Esposito, N.V. Shetty
CERN, Geneva, Switzerland

The LHCb detector will be upgraded during the second long shutdown (LS2) of the LHC machine, in order to increase its statistical precision significantly. The upgraded LHCb foresees a peak luminosity of L = 1-2 . 10³³ cm^-2 s⁻¹, with a pileup of 5. This represents ten times more luminosity and five times more pile up than in the present LHC. With these conditions, the pp-collisions and beam losses will produce a non-negligeable beam-induced energy deposition in the interaction region. More precisely, studies have shown that the energy deposition will especially increase on the D2 recombination dipole, which could bring them close to their safety thresholds. To avoid this, the placement of a minimal neutral absorber has been proposed. This absorber will have the same role as the TAN in the high luminosity Interaction Regions (IR) 1 and 5. This study shows the possible dimensions and location of this absorber, and how it would reduce both the peak power density and total heat load.

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TUPRO021

Preliminary Study of Risks and Failure Scenarios for the High Luminosity Experiments in HL-LHC

1055

F. Bouly
LPSC, Grenoble Cedex, France
R. Alemany-Fernández, H. Burkhardt, D. Wollmann
CERN, Geneva, Switzerland
B. Yee-Rendón
CINVESTAV, Mexico City, Mexico

For the HL-LHC it is planned to basically double the diameter of the triplet quadruple magnets around the high luminosity insertions of the LHC. The high luminosity experiments ATLAS and CMS would like to keep a small central chamber radius close the interaction point. In the context of collider-experiment studies for the high-luminosity upgrade of the LHC, we present a first study of the possible consequences of these changes for the experimental running conditions based on detailed simulations with tracking. We have started to implement crab cavity failures and discuss first results from these simulations.

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TUPRO023

Beam-beam Effects in Different Luminosity Levelling Scenarios for the LHC

1061

SUSPSNE001

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X. Buffat, D. Banfi, G.R. Coombs
EPFL, Lausanne, Switzerland
W. Herr, T. Pieloni
CERN, Geneva, Switzerland

Adjusting luminosity and optimizing the luminous region in each interaction point of the LHC according to the experiments needs has become a requirement to maximize the efficiency of the different detectors. Several techniques are envisaged, most importantly by varying β* or a transverse offset at the interaction point. Coherent and incoherent stability in the presence of beam-beam effects will be discussed in realistic luminosity levelling scenarios for the LHC.

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TUPRO024

Benchmarking Studies of Intra Beam Scattering for HL-LHC

1064

D. Angal-Kalinin
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A. Wolski
The University of Liverpool, Liverpool, United Kingdom
A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404
The effects of Intra Beam Scattering (IBS) in the High Luminosity upgrade of the LHC (HL-LHC) will be stronger compared to effects in the present LHC because of the high intensity of the proton bunches and the new proposed optics. We present benchmarking studies carried out for the present LHC at injection and collision energies as well as HL-LHC at collision energy with the Achromatic Telescopic Squeezing optics. The results of IBS growth-rate calculations using the full Bjorken-Mtingwa formulae* are compared with simplified formulae**, Bane’s high energy approximation***, and the completely integrated modified Piwinski approximation****. The results of calculations based on these methods carried out in Mathematica are compared with results from the codes MAD-X and ZAP.
* J. Broken and S. Mtingwa, Part. Accel. 13, 115 (1983)
** K. Kubo et al, PRST-AB, 8, 081001 (2005)
*** K. Bane, EPAC2002
**** S. Mtingwa and A. Tollestrup, Fermilab-Pub-89/224, 1987.

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TUPRO025

Initial Estimate of Fringe Field Effects in HL-LHC using Frequency Map Analysis

1067

SUSPSNE002

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S. Jones, D. Newton, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
S. Jones, D. Newton, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by the Science and Technology Facilities Council, UK
The planned High Luminosity upgrade to the LHC will require stronger focusing of the beam in the interaction regions. To achieve this, the inner triplet quadrupoles will be replaced with new magnets having larger gradient and aperture. In this new focusing regime the quadrupole fringe fields are expected to have a greater effect on the beam dynamics, due to their large aperture, as compared to the nominal LHC. In this preliminary study, simplified models are used in a tracking code to assess the impact of the fringe fields on the dynamics using frequency map analysis.

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TUPRO026

Possible Beam-beam and Levelling Scenarios for HL-LHC

1071

M.P. Crouch, R. Appleby
UMAN, Manchester, United Kingdom
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T. Pieloni
CERN, Geneva, Switzerland

Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404
The upgrade of the LHC from the current set-up to high luminosity performances will provide new challenges from the point of view of beam-beam as well as other collective effects and luminosity levelling. We present the current possibilities for doing luminosity levelling for HL-LHC. We explore the merits and drawbacks of each option and briefly discuss the operational implications. The simplest option being levelling with an offset between the two beams. In particular, we look at the possibility of using flat beams in the IPs for all the available options and investigate their benefits and drawbacks, using the code COMBI. Flat beams would allow an additional degree of freedom, with the levelling only required in one of the planes at any given IP. To this end, various scenarios are looked at, both with and without crab cavities.

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TUPRO027

First Beam Background Simulation Studies at IR1 for High Luminosity LHC

1074

R. Kwee-Hinzmann, S.M. Gibson
JAI, Egham, Surrey, United Kingdom
G. Bregliozzi, R. Bruce, F. Cerutti, L.S. Esposito, R. Kersevan, A. Lechner, N.V. Shetty
CERN, Geneva, Switzerland
S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom

In the High-Luminosity Large Hadron Collider (HL-LHC) Project, the LHC will be significantly upgraded to attain a peak luminosity of up to 8.5 × 10³⁴ cm^-2s^-1, thus almost an order of magnitude higher compared to the nominal machine configuration in ATLAS at IP1 and CMS at IP5. In the view of a successful machine setup as well as a successful physics programme, beam induced background studies at IP1 were performed to investigate sources of particle fluxes to the experimental area. In particular as a start of the study, two sources forming the major contributions were simulated in detail: the first one considers inelastic interactions from beam particles hitting tertiary collimators, the second one from beam interactions with residual gas-molecules in the vacuum pipe close by the experiment, referred to as beam-halo and local beam-gas, respectively. We will present these first HL-LHC background studies based on SixTrack and FLUKA simulations, highlighting the simulation setup for the design case in the HL-LHC scenario. Results of particle spectra entering the ATLAS detector region are presented for the latest study version of HL-LHC machine layout (2013).

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TUPRO028

Energy Deposition Studies for the Hi-Lumi LHC Inner Triplet Magnets

1078

N.V. Mokhov, I.L. Rakhno, S.I. Striganov, I.S. Tropin
Fermilab, Batavia, Illinois, USA
F. Cerutti, L.S. Esposito, A. Lechner
CERN, Geneva, Switzerland

Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy through the US LARP Program, and by the High Luminosity LHC project.
After operation at the nominal luminosity, the LHC is planned to be upgraded to a 5-fold increased luminosity of 5×1034 cm^-2s⁻¹. The upgrade includes replacement of the IP1/IP5 inner triplet 70-mm NbTi quadrupoles with the 150-mm coil aperture Nb3Sn quadrupoles along with the new 150-mm coil aperture NbTi dipole magnet. A detailed model of the region with these new magnets, field maps, corrector packages, segmented tungsten inner absorbers was built and implemented into the FLUKA and MARS codes. Various aspects of the new design were studied: (i) thicknesses of tungsten absorbers; (ii) beam screen interruption in interconnects; (iii) crossing angle value and orientation, etc. In the optimized configuration, the peak power density averaged over the magnet inner cable width doesn’t exceed 2 mW/cm³, safely below the quench limit. For the integrated luminosity of 3000 fb-1, the highest peak dose of 35 MGy occurs in the corrector package CP, while for other magnets, the peak dose in the innermost insulators ranges from 20 to 30 MGy. Dynamic heat loads to the triplet magnet cold mass are calculated to be on a target 10 W/m level. FLUKA and MARS results agree within 10%.

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TUPRO031

RHIC Performance during the 7.5 GeV Low Energy Run in FY 2014

1087

C. Montag, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, K.A. Drees, W. Fischer, C.J. Gardner, X. Gu, M. Harvey, T. Hayes, H. Huang, R.L. Hulsart, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, S. Nemesure, J. Piacentino, P.H. Pile, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, J.E. Tuozzolo, M. Wilinski, K. Yip, A. Zaltsman, K. Zeno, W. Zhang
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.
As the last missing step in phase 1 of the beam energy scan (BES-I), aimed at the search for the critical point in the QCD phase diagram, RHIC collided gold ions at a beam energy of 7.3 GeV/nucleon during the FY 2014 run. While this particular energy is close to the nominal RHIC injection energy of 9.8 GeV/nucleon, it is nevertheless challenging because it happens to be close to the AGS transition energy, which makes longitudinal beam dynamics during transfer from the AGS to RHIC difficult. We report on machine performance, obstacles and solutions during the FY 2014 low energy run.

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TUPRO032

RHIC Performance for FY2014 Heavy Ion Run

1090

G. Robert-Demolaize, J.G. Alessi, M. Bai, E.N. Beebe, J. Beebe-Wang, S.A. Belomestnykh, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, J.J. Butler, R. Connolly, T. D'Ottavio, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, M. Harvey, T. Hayes, H. Huang, P.F. Ingrassia, J.P. Jamilkowski, 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, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, A.I. Pikin, P.H. Pile, V. Ptitsyn, D. Raparia, T. Roser, P. Sampson, J. Sandberg, V. Schoefer, C. Schultheiss, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, J.E. Tuozzolo, B. Van Kuik, M. Wilinski, Q. Wu, A. Zaltsman, K. Zeno, W. Zhang
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.
After running uranium-uranium and copper-gold collisions in 2012, the high energy heavy ion run of the Relativistic Heavy Ion Collider (RHIC) for Fiscal Year 14 (Run14) is back to gold-gold (Au-Au) collisions at 100 GeV/nucleon. Following the level of performance achieved in Run12, RHIC is still looking to push both instantaneous and integrated luminosity goals. To that end, a new 56 MHz superconducting RF cavity was installed and commissioned, designed to keep ions in one RF bucket and improve luminosity by allowing a smaller beta function at the interaction point (IP) due to a reduced hourglass effect. The following presents an overview of these changes and reviews the performance of the collider.

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TUPRO034

Beam-beam Interaction in the Asymmetric Energy Gold-gold Collision in RHIC

1093

Y. Luo, M. Blaskiewicz, M.R. Costanzo, W. Fischer, X. Gu, V.H. Ranjbar, S.M. White
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.
In this article, we study the beam-beam interaction in the possible future gold-gold collision with different particle energies in the Relativistic Heavy Ion Collider (RHIC). With different particle energies, the center-of-mass of collision is moving in the longitudinal direction during collision. Since the RF harmonic numbers are different for the two RHIC rings, bunches collide in 110 turns followed by 10 turns without collision. In this study, the stability of particles and the beam emittance growth are calculated through numeric simulations based on a 6-D weak-strong beam-beam interaction model.

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TUPME027

Analysis of the Electron Cloud Observations with 25 ns Bunch Spacing at the LHC

1410

G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy
G. Arduini, V. Baglin, D. Banfi, H. Bartosik, S.D. Claudet, C.O. Domínguez, J.F. Esteban Müller, G. Iadarola, T. Pieloni, G. Rumolo, E.N. Shaposhnikova, L.J. Tavian, C. Zannini, F. Zimmermann
CERN, Geneva, Switzerland

Electron Cloud (EC) effects have been identified as a major performance limitation for the Large Hadron Collider (LHC) when operating with the nominal bunch spacing of 25 ns. During the LHC Run 1 (2010 - 2013) the luminosity production mainly used beams with 50 ns spacing, while 25 ns beams were only employed for short periods in 2011 and 2012 for test purposes. On these occasions, observables such as pressure rise, heat load in the cold sections as well as clear signatures on bunch-by-bunch emittance blow up, particle loss and energy loss indicated the presence of an EC in a large portion of the LHC. The analysis of the recorded data, together with EC build up simulations, has led to a significant improvement of our understanding of the EC effect in the different components of the LHC. Studies were carried out both at injection energy (450 GeV) and at top energy (4 TeV) aiming at determining the energy dependence of the EC formation and its impact on the quality of the proton beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME027

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TUPRI014

Modelling and Long Term Dynamics of Crab Cavities in the LHC

1578

R. Appleby, D.R. Brett
UMAN, Manchester, United Kingdom
J. Barranco García, R. De Maria, A. Grudiev, R. Tomás
CERN, Geneva, Switzerland

Funding: The research leading to these results has received funding from the European Commission under the FP7 project HiLumi LHC, GA no. 284404, co-funded by the DoE, USA and KEK, Japan.
The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) aims to achieve an integrated luminosity of 250-300 fb-1 per year. This upgrade includes the use crab cavities to mitigate the geometric loss of luminosity arising from the beam crossing angle. The tight space constraints at the location of the cavities leads to cavity designs which are axially non-symmetric and have a potentially significant effect on the long term dynamics and dynamic aperture of the LHC. In this paper we present the current status of advanced modelling of crab cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI014

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TUPRI022

Beam-Beam Studies in LHC- Beam Loss and Bunch Shortening

1603

K. Ohmi
KEK, Ibaraki, Japan

In Hadron colliders, luminosity degrade various mechanism. Beam-beam related emittance growth is caused by resonances induced by crossing angle. Tune spread due to chromaticity enhances the resonances effect. A bunch shortening phenomenon related to beam-beam interaction has been observed in LHC. The bunch length has an anti-correlation with transverse emittance. This phenomenon has been studied using a weak-strong beam-beam simulation (BBWS code).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI022

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