01 Circular Colliders
A01 Hadron Colliders

Paper	Title	Page
MOYAA01	The LHC from Commissioning to Operation	11
	M. Lamont CERN, Geneva, Switzerland
	In 2011 the LHC moves from commissioning into the physics production phase with the aim of accumulating 1fb-1 by the end of 2011. The progress from commissioning to operation is described. Emphasis is put on the beam performance, but also on the performance of the different hardware systems. The role of collimation and machine protection is discussed, in view of the very high stored beam and magnet energy. Comment: Other invited presentations in this conference will cover the experience with beam instrumentation and the upgrade programmes.
	Slides MOYAA01 [7.410 MB]
TUYA01	Achievements and Lessons from the Tevatron	903
	V.D. Shiltsev Fermilab, Batavia, USA
	The Tevatron Run-2 will come to an end at the time of IPAC'11. This talk will concentrate on exploration of the accelerator physics issues that were dealt with in achieving the current (very high) level of performance in the Tevatron and will review achievements, challenges and lessons learned on the way.
	Slides TUYA01 [5.881 MB]
TUYA02	LHC Upgrade Plans: Options and Strategy	908
	L. Rossi CERN, Geneva, Switzerland
	Presentation of options for future luminosity and/or energy upgrades of the LHC ring. The presentation should cover the different ideas, short term, medium term and long term, and discuss the research programme that is needed to prepare the upgrades.
	Slides TUYA02 [5.139 MB]
TUYA03	Stochastic Cooling of a High Energy Collider	913
	M. Blaskiewicz, J.M. Brennan, R.C. Lee, K. Mernick BNL, Upton, Long Island, New York, USA
	Three dimensional stochastic cooling was successfully implemented at the Relativistic Heavy Ion Collider to overcome emittance growth from intra-beam scattering. The talk reports on the experience of operating a collider with continuous cooling. The application of such techniques to other hadron machine (e.g. LHC) will be discussed.
	Slides TUYA03 [1.350 MB]
TUPC137	UFOs in the LHC	1347
	T. Baer, M.J. Barnes, B. Goddard, E.B. Holzer, J.M. Jimenez, A. Lechner, V. Mertens, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, B. Velghe, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland
	One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (”Unidentified Falling Objects”). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns when they interact with the beam. In 2011, the diagnostics for such events was significantly improved which allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge and mitigation strategies are presented.
TUPZ001	90 m Optics Commissioning	1795
	S. Cavalier LAL, Orsay, France H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger CERN, Geneva, Switzerland
	Special β* = 90 m optics have been developed for the two very high luminosity insertions of the LHC, as a first step towards to allow for very low angle precision measurements of the proton-proton collisions in the LHC. These optics were developed to be compatible with the standard LHC injection and ramp optics. The target value of β* = 90 m is reached by an un-squeeze from the injection β* = 11 m. We describe the implementation of this optics in the LHC and the first experience in the commissioning of these optics.
TUPZ002	90 m β* Optics for ATLAS/ALFA	1798
	S. Cavalier, P.M. Puzo LAL, Orsay, France H. Burkhardt CERN, Geneva, Switzerland A. Peskov NNGU, Nizhny Novgorod, Russia
	We describe a high β* optics developed for the ATLAS detector at the LHC interaction regions (IR1), Roman Pots have been installed 240 m left and right of IR1 to allow to measure the absolute luminosity and the total elastic cross section for ATLAS with ALFA (Absolute Luminosity for ATLAS). Ultimately, it is planned to preform these measurements at a very high β* of 2625 m. Here we describe a new, intermediate β* = 90 m optics, which has been optimized for compatibility with the present LHC running conditions. We described the main features and expected performance of this optics for ALFA.
TUPZ003	Simulation of Electron-cloud Build-Up for the Cold Arcs of the LHC and Comparison with Measured Data	1801
	G.H.I. Maury Cuna CINVESTAV, Mérida, Mexico G. Arduini, G. Rumolo, L.J. Tavian, F. Zimmermann CERN, Geneva, Switzerland
	The electron cloud generated by synchrotron radiation or residual gas ionization is a concern for LHC operation and performance. We report the results of simulations studies which examine the electron cloud build-up, at injection energy, 3.5 TeV for various operation parameters In particular we determine the value of the secondary emission yield corresponding to the multipacting threshold, and investigate the electron density, and heat as a function of bunch intensity for dipoles and field-free regions. We also include a comparison between simulations results and measured heat-load data from the LHC scrubbing runs in 2011
TUPZ004	The NICA Facility in Polarized Proton Operation Mode	1804
	A.D. Kovalenko, N.N. Agapov, Y. Filatov, V.D. Kekelidze, R.I. Lednicky, I.N. Meshkov, V.A. Mikhaylov, A.O. Sidorin, A. Sorin, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia
	Basic goal of the planned NICA facility at JINR is focused on the studying of heavy ion collisions over the energy range √s ~ 4 11 GeV/u. Capabilities of the proposed scheme were carefully analyzed in this case and reaching of the desired average luminosity, L = 1·1027 cm-2 s−1 for gold-gold collisions at √s = 9 GeV/u, have been confirmed. The other important NICA research domain is the experiments with polarized proton beams at the highest possible energy, the highest luminosity and polarization degree as well. The main aim is to provide √s ~ 25 GeV and L ~ 1·1031 cm-2 s−1. The unsolved aspects of the problem are discussed, possible solutions are analyzed and necessary modifications of the NICA scheme are considered as well.
TUPZ005	Design of the NICA Collider Rings	1807
	O.S. Kozlov, H.G. Khodzhibagiyan, S.A. Kostromin, I.N. Meshkov, A.O. Sidorin, N.D. Topilin, G.V. Trubnikov JINR, Dubna, Moscow Region, Russia
	The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex being constructed at JINR aimed to provide the collider experiments with ion-ion (Au79+) and ion-proton collisions at the energy range of 1-4.5 GeV/n and also the collisions of polarized proton-proton and deuteron-deuteron beams. Superconducting collider rings accumulate beam injected from Nuclotron and realize the conditions for beam-beam interactions to achieve the required luminosity. Each ring has the racetrack shape with two arcs and two long straight sections. Its circumference is about 500 m. The collider lattice design is subjected to have possibility of the gamma transition variation, mainly by the arcs retuning. The long straight sections contain the most of the insertion devices and are matched to the arcs, optimized to provide the final focusing of the beams in IP and accurate betatron tune adjustment.
TUPZ006	Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan	1810
	R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann CERN, Geneva, Switzerland M. Alabau IFIC, Valencia, Spain
	A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in σs of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.
TUPZ007	First Ion Collimation Commissioning Results at the LHC	1813
	G. Bellodi, R.W. Assmann, R. Bruce, M. Cauchi, J.M. Jowett, G. Valentino, D. Wollmann CERN, Geneva, Switzerland
	First commissioning of the LHC Pb ion beams to 1.38 A TeV energy was successfully achieved in November 2010. Ion collimation has been predicted to be less efficient than for protons at the LHC, because of the complexity of the physical processes involved: nuclear fragmentation and electromagnetic dissociation in the primary collimators creating fragments with a wide range of Z/A ratios, that are not intercepted by the secondary collimators but lost in the dispersion suppressor sections of the ring. In this article we present first comparisons of measured loss maps with theoretical predictions from simulation runs with the ICOSIM code. An extrapolation to define the ultimate intensity limit for Pb beams is attempted. The scope of possible improvements in collimation efficiency coming from the installation of new collimators in the cold dispersion suppressors and combined betatron and momentum cleaning is also explored.
TUPZ009	LHC Machine Protection against Very Fast Crab Cavity Failures	1816
	T. Baer, R. Tomás, J. Tückmantel, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland T. Baer Uni HH, Hamburg, Germany R. Calaga BNL, Upton, Long Island, New York, USA
	For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is essential to compensate the geometric luminosity loss due to the crossing angle. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a CC quench), the voltage and/or phase of a CC can change significantly with a fast time constant of the order of a LHC turn. This can lead to large, global betatron oscillations of the beam. Against the background of machine protection, the influence of a CC failure on the beam dynamics is discussed. The results from dedicated tracking studies, including the LHC upgrade optics, are presented. Necessary countermeasures to limit the impact of CC failures to an acceptable level are proposed.
TUPZ010	Longitudinal Emittance Blow-up in the LHC	1819
	P. Baudrenghien, A.C. Butterworth, M. Jaussi, T. Mastoridis, G. Papotti, E.N. Shaposhnikova, J. Tückmantel CERN, Geneva, Switzerland
	The LHC relies on Landau damping for longitudinal stability. To avoid decreasing the stability margin at high energy, the longitudinal emittance must be continuously increased during the acceleration ramp. Longitudinal blow-up provides the required emittance growth. The method was implemented through the summer of 2010. We inject band-limited RF phase-noise in the main accelerating cavities during the whole ramp of about 11 minutes. Synchrotron frequencies change along the energy ramp, but the digitally created noise tracks the frequency change. The position of the noise-band, relative to the nominal synchrotron frequency, and the bandwidth of the spectrum are set by pre-defined constants, making the diffusion stop at the edges of the demanded distribution. The noise amplitude is controlled by feedback using the measurement of the average bunch length. This algorithm reproducibly achieves the programmed bunch length of about 1.2 ns (4 σ) at flat top with low bunch-to-bunch scatter and provides a stable beam for physics coast.
TUPZ012	Machine-induced Showers entering the ATLAS and CMS Detectors in the LHC	1825
	R. Bruce, R.W. Assmann, V. Boccone, H. Burkhardt, F. Cerutti, A. Ferrari, M. Huhtinen, W. Kozanecki, Y.I. Levinsen, A. Mereghetti, A. Rossi, Th. Weiler CERN, Geneva, Switzerland N.V. Mokhov Fermilab, Batavia, USA
	One source of experimental background in the LHC is showers induced by particles hitting the upstream collimators or particles that have been scattered on the residual gas. We estimate the flux and distribution of particles entering the ATLAS and CMS detectors through FLUKA simulations originating from tertiary collimator hits and inelastic beam-gas interactions. Comparisons to MARS results are also presented.
TUPZ013	Calculation Method for Safe Beta* in the LHC	1828
	R. Bruce, R.W. Assmann, W. Herr, D. Wollmann CERN, Geneva, Switzerland
	One way of increasing the peak luminosity in the LHC is to decrease the beam size at the interaction points by squeezing to smaller values of beta*. The LHC is now in a regime where safety and stability determines the limit in beta*, as opposed to traditional optics limits. In this paper, we derive a calculation model to determine the safe beta*-values based on collimator settings and operational stability of the LHC. This model was used to calculate the settings for the LHC run in 2011. It was found that beta* could be decreased from 3.5 m to 1.5 m, which has now successfully been put into operation.
TUPZ014	Luminosity Optimization for a Higher-Energy LHC	1831
	C.O. Domínguez, F. Zimmermann CERN, Geneva, Switzerland
	A Higher-Energy Large Hadron Collider (HE-LHC) is an option to further push the energy frontier of particle physics beyond the present LHC. A beam energy of 16.5 TeV would require 20-T dipole magnets in the existing LHC tunnel, which should be compared with 7 TeV and 8.33 T for the nominal LHC. Since the synchrotron radiation power increases with the fourth power of the energy, radiation damping becomes significant for the HE-LHC. It calls for transverse and longitudinal emittance control vis-à-vis beam-beam interaction and Landau damping. The heat load from synchrotron radiation, gas scattering, and electron cloud also increases with respect to the LHC. In this paper we discuss the proposed HE-LHC beam parameters; the time evolution of luminosity, beam-beam tune shifts, and emittances during an HE-LHC store; the expected heat load; and luminosity optimization schemes for both round and flat beams.
TUPZ015	Electron Cloud Parameterization Studies in the LHC	1834
	C.O. Domínguez, G. Arduini, V. Baglin, G. Bregliozzi, J.M. Jimenez, E. Métral, G. Rumolo, D. Schulte, F. Zimmermann CERN, Geneva, Switzerland
	During LHC beam commissioning with 150, 75 and 50-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. The main strategy to combat the LHC electron cloud relies on the surface conditioning arising from the chamber-surface bombardment with cloud electrons. In a standard model, the conditioning state of the beam-pipe surface is characterized by three parameters: 1. the secondary emission yield; 2. the incident electron energy at which the yield is maximum; and 3. the probability of elastic reflection of low-energy primary electrons hitting the chamber wall. Since at the LHC no in-situ secondary-yield measurements are available, we compare the relative local pressure-rise measurements taken for different beam configurations against simulations in which surface parameters are scanned. This benchmark of measurements and these simulations is used to infer the secondary-emission properties of the beam-pipe at different locations around the ring and at various stages of the surface conditioning. In this paper we present the methodology and first results from applying the technique to the LHC.
TUPZ016	First Run of the LHC as a Heavy-ion Collider	1837
	J.M. Jowett, G. Arduini, R.W. Assmann, P. Baudrenghien, C. Carli, M. Lamont, M. Solfaroli Camillocci, J.A. Uythoven, W. Venturini Delsolaro, J. Wenninger CERN, Geneva, Switzerland
	A year of LHC operation typically consists of an extended run with colliding protons, ending with a month in which the LHC has to switch to its second role as a heavy ion collider and provide a useful integrated luminosity to three experiments. The first such run in November 2010 demonstrated that this is feasible. Commissioning was extremely rapid, with collisions of Pb nuclei achieved within 55 h of first injection. Stable beams for physics data-taking were declared a little over one day later and the final integrated luminosity substantially exceeded expectations.
TUPZ017	Luminosity and Beam Parameter Evolution for Lead Ion Beams in the LHC	1840
	J.M. Jowett, R. Bruce, T. Mertens CERN, Geneva, Switzerland
	Heavy ion beams in the LHC are subject to strong blow-up and debunching effects from intra-beam scattering and luminosity-driven beam losses. The large nuclear charge is at the origin of these effects, both in the cross sections for simple Coulomb scattering and the ultraperipheral interactions occurring in the collisions. We compare predictions from our models with data on luminosity, beam size and intensity evolution from the first heavy ion run of the LHC. This analysis has to take account of the varying capabilities of the LHC beam instrumentation between injection and collision energies.
TUPZ019	Transverse Emittance Preservation through the LHC Cycle	1843
	V. Kain, B. Goddard, B.J. Holzer, J.M. Jowett, M. Meddahi, T. Mertens, F. Roncarolo CERN, Geneva, Switzerland
	The preservation of the transverse emittance is crucial for luminosity performance. At the LHC design stage the total allowed emittance increase was set to 7% throughout the LHC cycle. The proton run in 2010 showed that the injectors can provide beams with smaller emittances than nominal and higher bunch intensities. The LHC parameters are well under control and the emittances are kept below nominal until physics. The LHC luminosity goals for the first year of running could therefore be achieved with fewer bunches than initially foreseen. This paper will report on the measured emittance growth at injection from the SPS and the evolution of the emittance through the entire LHC cycle. Sources and possible cures for the observed emittance growth will be discussed.
TUPZ020	Fill Analysis and Experimental Background Observations in the LHC	1846
	Y.I. Levinsen, H. Burkhardt, A. Macpherson, M. Pereira, S.X. Roe CERN, Geneva, Switzerland
	Funding: Presenting author funded by the University of Oslo In this work we look at experimental background under different conditions for the early 2011 running. We will discuss the observations in the context of the residual gas pressure, beam halo, and cross-talk between experiments. We have developed a modular fill analysis tool which automatically extracts data and analyses each fill in the LHC. All generated and extracted information is stored for outside use. The tool is applied to aid us in the work presented here.
TUPZ023	Observation of Bunch to Bunch Differences due to Beam-beam Effects	1855
	G. Papotti, R. Alemany-Fernandez, R. Giachino, W. Herr, T. Pieloni, M. Schaumann, G. Trad CERN, Geneva, Switzerland
	Due to the bunch filling schemes in the LHC the bunches experience a very different collision schedule and therefore different beam-beam effects. These differences and the effect on the performance have been observed and compared with the expectations. Possible limitations due to these effects are discussed.
TUPZ025	Experience with Offset Collisions in the LHC	1858
	G. Papotti, R. Alemany-Fernandez, F. Follin, R. Giachino, W. Herr, T. Pieloni, M. Schaumann CERN, Geneva, Switzerland R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA
	To keep the luminosity under control, some experiments require the adjustment of the luminosity during a fill, so-called luminosity leveling. One option is the separate the beams transversely and adjust the separation to the desired collision rate. The results from controlled experiments are reported and interpreted. The feasibility of this method for ultimate luminosities is discussed.
TUPZ026	Alternative Working Point(s) at Injection for the LHC	1861
	R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP). At present, the LHC operates with a different fractional tunes at injection and at collision energy due to improved dynamic aperture indicated by tracking studies. Therefore, a tune swing crossing the 10th order resonance is needed during the beta-squeeze. A new proposal to alter the working point to collision tunes already at injection and during an energy ramp is foreseen to avoid the tune jump. Simulations and measurements of the optics along with the beam emittances and lifetime are compared to the nominal injection tunes. Feasibility for a working point close to the 1/2 integer is also attempted.
TUPZ027	Beta* Measurement in the LHC Based on K-modulation	1864
	R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP). Accurate knowledge of the collision point optics is crucial to equalize the luminosities at the different experiments. K-modulation was successfully applied at several accelerators for measuring the lattice beta functions. In the LHC, it was proposed as an alternative method to compute the beta* at the collision points. Results of beta* measurements in the LHC based on the K-modulation technique are presented with comparisons to nominal segment-by-segment method.
TUPZ028	Beam Based Optimization of the Squeeze at the LHC	1867
	X. Buffat EPFL, Lausanne, Switzerland M. Lamont, S. Redaelli, J. Wenninger CERN, Geneva, Switzerland
	The betatron squeeze is a critical operational phase for the LHC because it is carried out at top energy, with the maximum stored energy and with reduced aperture margins in the superconducting triplets. A stable operation with minimum beam losses must be achieved in order to ensure a safe and efficient operation. The operational experience at the LHC showed that this is possible. The operation in 2010 is reviewed. In particular, orbit, tune and chromaticity measurements are investigated and correlated to beam losses. Different optimizations are then proposed towards a more efficient and robust operation. The improvements obtained for the operation in 2011 are presented.
TUPZ029	Observation of Coherent Beam-beam Effects in the LHC	1870
	X. Buffat EPFL, Lausanne, Switzerland R. Calaga, S.M. White BNL, Upton, Long Island, New York, USA R. Giachino, W. Herr, G. Papotti, T. Pieloni CERN, Geneva, Switzerland
	Early collisions in the LHC with a very limited number of bunches with high intensities indicated the presence of coherent beam-beam driven oscillations. Here we discuss the experimental results and compare with the expectations.
TUPZ030	Simulation of Linear Beam Parameters to Minimize the Duration of the Squeeze at the LHC	1873
	X. Buffat EPFL, Lausanne, Switzerland G.J. Müller, S. Redaelli, M. Strzelczyk CERN, Geneva, Switzerland
	The betatron squeeze allows to increase the luminosity of a collider by reducing the β function at the interaction points. This operation has shown to be very critical in previous colliders. In this state of mind, the squeezing was performed extremely safely during the first year of operation of the Large Hadron Collider, at the expense of the duration of the process. As the turnaround time is a relevant parameter for the integrated luminosity, a squeeze of shorter duration is proposed for 2011 and further. MadX simulation of linear beam parameters based on settings extracted from the LHC control system are used to justify the proposal. Further optimization of the squeeze setting generation is also discussed.
TUPZ031	Near Beam-gas Backgrounds for LHCb at 3.5 TeV	1876
	D.R. Brett, R. Appleby UMAN, Manchester, United Kingdom F. Alessio, G. Corti, R. Jacobsson CERN, Geneva, Switzerland M.H. Lieng UNIDO, Dortmund, Germany V. Talanov IHEP Protvino, Protvino, Moscow Region, Russia
	Funding: STFC We consider the machine induced backgrounds for LHCb arising from collisions of the beam with residual gas in the long straight sections of the LHC close to the experiment. We concentrate on the background particle fluxes initiated by inelastic beam-gas interactions with a direct line of sight to the experiment, with the potential impact on the experiment increasing for larger beam currents and changing gas pressures. In this paper we calculate the background rates for parameters foreseen with LHC running in 2011, using realistic residual pressure profiles. We also discuss the effect of using a pressure profile formulated in terms of equivalent hydrogen, through weighting of other residual gases by their cross section, upon the radial fluxes from the machine and the detector response. We present the expected rates and the error introduced through this approximation.
TUPZ032	LHC Luminosity Upgrade with Large Piwinski Angle Scheme: A Recent Look	1879
	C.M. Bhat Fermilab, Batavia, USA F. Zimmermann CERN, Geneva, Switzerland
	Funding: Work is supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and US LARP. Luminosity upgrade at the LHC collider using bunches with constant line charge density (longitudinally flat bunches) but with same beam-beam tune shift at collision, the so called large Piwinski angle scheme* is being studied with renewed interest in recent years**. By design the total beam-beam tune shift at the LHC is less than 0.015. But the initial operational experience at the LHC indicates the possibility of operating with beam-beam tune shifts as high as 0.02. In view of this development we have revisited the requirements for the Large Piwinski Angle scheme at the LHC. In this paper we present a new parameter list supported by 1) calculations on the luminosity gain, 2) reduction of e-cloud issues on nearly flat bunches and 3) longitudinal beam dynamics simulations. We also make some remarks on the needed upgrades on the LHC injector accelerators. * F. Ruggiero and F. Zimmermann, PRST-AB 5, 061001 (2002). ** C. M. Bhat, CERN-2009-004, pp. 106-114. Thanks to O.Bruning, E.Shaposhnikova, H.Damerau, E.Mahner, F.Caspers & CERN BE/ABP & RF Depts.
TUPZ033	Measurements of Transverse Beam Diffusion Rates in the Fermilab Tevatron Collider	1882
	G. Stancari, G. Annala, T.R. Johnson, D.A. Still, A. Valishev Fermilab, Batavia, USA
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. This work was partially supported by the US LHC Accelerator Research Program (LARP). The transverse beam diffusion rate vs. particle oscillation amplitude was measured in the Tevatron using collimator scans. All collimator jaws except one were retracted. As the jaw of interest was moved in small steps, the local shower rates were recorded as a function of time. By using a diffusion model, the time evolution of losses could be related to the diffusion rate at the collimator position. Preliminary results of these measurements are presented.
	Poster TUPZ033 [1.036 MB]
TUPZ034	Impact of Arc Phase Advance on Chromatic Optics in RHIC	1885
	R. Calaga, R. Miyamoto, G. Robert-Demolaize, S.M. White BNL, Upton, Long Island, New York, USA R. De Maria, R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work is partially supported by the US Department of Energy through the LHC Accelerator Research program (LARP). The phase advance between the two interaction points in RHIC is optimized for dynamic aperture for a initial design beta-star. This may not hold true as RHIC presently operates with a considerably reduced beta-star. Additionally the reduction of the available beam aperture due to an enlarged chromatic beta-beating is evident. Results from phase advance scans between the two IPs to reduce the chromatic beta-beating in model and measurements are presented. Impact on the single beam lifetime and momentum aperture is compared to the nominal optics.
TUPZ035	RHIC Polarized Proton Status and Operation Highlights	1888
	H. Huang, L. A. Ahrens, I.G. Alekseev, E.C. Aschenauer, G. Atoian, M. Bai, A. Bazilevsky, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, A. Dion, K.A. Drees, W. Fischer, J.W. Glenn, X. Gu, L.T. Hoff, C. Liu, Y. Luo, W.W. MacKay, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, M.G. Minty, C. Montag, J. Morris, A. Poblaguev, V. Ptitsyn, G. Robert-Demolaize, T. Roser, W.B. Schmidke, V. Schoefer, D. Smirnov, S. Tepikian, J.E. Tuozzolo, G. Wang, K. Yip, A. Zaltsman, A. Zelenski, S.Y. Zhang BNL, Upton, Long Island, New York, USA D. Svirida ITEP, Moscow, Russia
	RHIC op­er­a­tion as the po­lar­ized pro­ton col­lid­er pre­sents unique chal­lenges since both lu­mi­nos­i­ty and spin po­lar­iza­tion are im­por­tant. A lot of up­grades and mod­i­fi­ca­tions have been made since last po­lar­ized pro­ton op­er­a­tion. A 9 MHz rf sys­tem has been in­stalled to im­prove lon­gi­tu­di­nal match at in­jec­tion and to in­crease lu­mi­nos­i­ty. A ver­ti­cal sur­vey of RHIC was per­formed be­fore the run to get bet­ter mag­net align­ment. The orbit con­trol has also been im­proved this year. AGS po­lar­iza­tion trans­fer ef­fi­cien­cy is improved by a horizontal tune jump system. To pre­serve po­lar­iza­tion on the ramp, a new work­ing point was cho­sen with the ver­ti­cal tune near a third order res­o­nance. The orbit and tune control are essential for polarization preservation. To calibrate the polarization level at 250 GeV, polarized protons were accelerated up to 250GeV and decelerated back to 100GeV. The tune, orbit and chromaticity feedback is essential for this operation. The new record of luminosity was achieved with higher polarization at 250 GeV in this run. The overview of the changes and op­er­a­tion re­sults are pre­sent­ed in this paper.
TUPZ037	Momentum Aperture for the Low Beta* Lattices in RHIC Au-Au Runs	1891
	Y. Luo, K.A. Brown, W. Fischer, X. Gu, G. Robert-Demolaize, T. Roser, V. Schoefer, S. Tepikian, D. Trbojevic BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In this article we calculate the momentum apertures with the low beta* lattices of 100 GeV RHIC Au-Au run. With RF re-bucketing, the maximum off-momentum spread reaches 1.7 ·10-03 at store. To improve the momentum aperture, we need to reduce the nonlinear chromaticities. The methods to correct second order chromaticities in RHIC rings are presented. We also scan beta* at IP6 and IP8 and working point. The challenges to further reduce beta* in the RHIC Au-Au operation are discussed.
TUPZ038	RHIC Performance for FY2011 Au+Au Heavy Ion Run	1894
	G.J. Marr, L. A. Ahrens, M. Bai, J. Beebe-Wang, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, J.J. Butler, C. Carlson, R. Connolly, T. D'Ottavio, K.A. Drees, A.V. Fedotov, W. Fischer, W. Fu, C.J. Gardner, D.M. Gassner, J.W. Glenn, X. Gu, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, P.F. Ingrassia, J.P. Jamilkowski, N.A. Kling, M. Lafky, J.S. Laster, C. Liu, Y. Luo, M. Mapes, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, S. Polizzo, V. Ptitsyn, G. Robert-Demolaize, T. Roser, P. Sampson, J. Sandberg, V. Schoefer, C. Schultheiss, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, B. Van Kuik, G. Wang, M. Wilinski, A. Zaltsman, K. Zeno, S.Y. 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. Following the Fiscal Year (FY) 2010 (Run-10) Relativistic Heavy Ion Collider (RHIC) Au+Au run [1], RHIC experiment upgrades sought to improve detector capabilities. In turn, accelerator improvements were made to improve the luminosity available to the experiments for this run (Run-11). These improvements included: a redesign of the stochastic cooling systems for improved reliability; a relocation of “common” RF cavities to alleviate intensity limits due to beam loading; and an improved usage of feedback systems to control orbit, tune and coupling during energy ramps as well as while colliding at top energy. We present an overview of changes to the Collider and review the performance of the collider with respect to instantaneous and integrated luminosity goals.
TUPZ039	Modelling of the AGS Using Zgoubi - Status	1897
	F. Méot, L. A. Ahrens, Y. Dutheil, J.W. Glenn, H. Huang, T. Roser, N. Tsoupas BNL, Upton, Long Island, New York, USA
	Models of the Alternating Gradient Synchrotron, based on stepwise ray-tracing methods using both mathematical modelling or field maps so to represent the optical elements, including the siberian snakes, are being developed based on stepwise ray-tracing numerical tools. The topic is introduced in earlier PAC and IPAC publications, a status is given here.
WEODA01	Observations of Beam-beam Effects at High Intensities in the LHC	1936
	W. Herr, R. Alemany-Fernandez, R. Giachino, G. Papotti, T. Pieloni CERN, Geneva, Switzerland R. Calaga BNL, Upton, Long Island, New York, USA E. Laface ESS, Lund, Sweden M. Schaumann RWTH, Aachen, Germany
	First observations with colliding beams in the LHC with bunch intensities close to nominal and above are reported. In 2010 the LHC initially operated with few bunches spaced around the circumference. Beam-beam tune shifts exceeding significantly the design value have been observed. In a later stage crossing angles were introduced around the experiments to allow the collisions of bunch trains. We report the first experience with head-on as well as long range interactions of high intensity bunches and discuss the possible performance reach.
	Slides WEODA01 [0.409 MB]