IPAC2017 - List of Keywords (luminosity)

Paper	Title	Other Keywords	Page
MOYAA1	Approaching the Nominal Performance at the LHC	operation, emittance, experiment, injection	13
	J. Wenninger CERN, Geneva, Switzerland
	In 2015 the Large Hadron Collider (LHC) restarted for Run 2 after an almost two year long shutdown to consolidate the machine for operation at nominal beam energy. Following a month of recommissioning and training of the magnet system, the LHC operated for the first time at an energy of 6.5 TeV. The aim of this first year was to master operation at the higher energy and with beams of 25 ns spacing. In 2016 the performance could be pushed based on the experience of 2015, culminating with a luminosity 40% above the design value of 10³⁴ cm^-2s⁻¹. The status of the machine operation, performance and prospects for the rest of Run 2 and Run 3 will be discussed.
	Slides MOYAA1 [4.639 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOYAA1
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MOPAB004	Improved Protection of the Warm Magnets of the LHC Betatron Cleaning Insertion	shielding, radiation, operation, collimation	72
	C. Bahamonde Castro, F. Cerutti, P. Fessia, A. Lechner, A. Mereghetti, D. Mirarchi, S. Redaelli, E. Skordis CERN, Geneva, Switzerland E. Skordis The University of Liverpool, Liverpool, United Kingdom
	After the High Luminosity (HL) upgrade in 2024-2026, the LHC is anticipated to increase its integrated luminosity by a factor of 10 beyond its original design value of 300 fb-1. In preparation for this, several improvements to the equipment will already be implemented during the next Long Shutdown (LS2) starting in 2019. In the betatron cleaning insertion, the debris leaking out of several collimators will deposit energy in the downstream warm magnets, causing long-term radiation damage. A new layout has been proposed in which the most exposed magnet of each assembly is removed, reducing the assembly from 6 to 5 magnet units and gaining 2 spare magnets. New absorbers are therefore required to enhance the shielding of the remaining magnet string. In this paper, we present an evaluation of the dose to the warm magnets for post-LS2 operation, and we quantify the achievable reduction of the long-term radiation damage for different absorber configurations. A solution for an improved magnet protection that fulfills the HL-LHC requirements is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB004
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MOPAB027	Preparation of CVD Diamond Detector for fast Luminosity Monitoring of SuperKEKB	detector, simulation, monitoring, target	135
	C.G. Pang, P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault LAL, Orsay, France
	The SuperKEKB e⁺-e⁻ collider aims to reach a very high luminosity of 8×10 ³⁵ cm'2s'1, using highly focused ultra-low emittance bunches colliding every 4ns. To meet the requirement of the dithering feedback system used to stabilize the horizontal orbit at the IP (interaction point), a relative precision of 10 '3 in 1ms is specified for the fast luminosity monitoring, which can be in principle achieved thanks to the large cross section of the radiative Bhabha process. This paper firstly presents the fraction of detected Bhabha scattering positrons with a new beam pipe arrangement coupled with a Tungsten radiator to be installed in the Low Energy Ring; Then the characteristics of signals from a sCVD diamond detector with thickness of 140'm coupled with a broadband current amplifier were studied based on tests with a Sr-90 source; Finally, simulated results for the reconstructed luminosity and the relative precision with different assumed luminosities are also reported.
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MOPAB109	Operational Experience with Luminosity Scans for Beam Size Estimation in 2016 LHC Proton Physics Operation	emittance, operation, proton, simulation	374
	M. Hostettler LHEP, Bern, Switzerland K. Fuchsberger, G. Papotti CERN, Geneva, Switzerland
	Luminosity scans were regularly performed at the CERN Large Hadron Collider (LHC) as of 2015 as a complementary method for measuring the beam size. The CMS experiment provides bunch-by-bunch luminosities at sufficient rates to allow evaluation of bunch-by-bunch beam sizes, and the scans are performed in the horizontal and vertical plane separately. Closed orbit differences between bunches can also be derived by this analysis. During 2016 LHC operation, these scans were also done in an automated manner on a regular basis, and the analysis was improved to significantly reduce the systematic uncertainty, especially in the crossing plane. This contribution first highlights the recent improvements to the analysis and elaborates on their impact. The measured beam sizes during 2016 proton physics operation are then shown and compared to measurements from synchrotron light telescopes and estimates based on the absolute luminosities of the LHC experiments.
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MOPAB110	Comparison of Transverse Emittance Measurements in the LHC	emittance, experiment, detector, operation	377
	M. Hostettler, R. Alemany-Fernández, F. Alessio, M. Ferro-Luzzi, K. Fuchsberger, G. Iadarola, R. Matev, S. Papadopoulou, Y. Papaphilippou, G. Papotti, G. Trad CERN, Geneva, Switzerland F. Antoniou The University of Liverpool, Liverpool, United Kingdom G.R. Coombs University of Glasgow, Glasgow, United Kingdom T.B. Hadavizadeh Oxford University, Physics Department, Oxford, Oxon, United Kingdom
	Transverse emittance measurement in a collider is of crucial importance for understanding beam dynamics observations and evaluating the machine performance. Devices measuring the beam emittance face the challenge of dealing with considerable systematic errors that can compromise the quality of the measurement. Having different instruments or techniques that provide beam size estimations in order to compare the outcome and give an unbiased value of the emittance is very important in a collider. The comparison of the different results is as well very useful to identify possible problems in a given equipment which could remain unnoticed if such device is the only source of emittance reconstruction. In the LHC several of these instruments and techniques are available; wire scanners, synchrotron light monitors, emittance reconstruction from transverse convolved beam sizes extracted from luminosity scans at the LHC collision points and from beam-gas imaging in the vertex detector of the LHCb experiment. Those systems are briefly presented in this paper together with the comparison of the emittances reconstructed by each of them during physics production over the 2016 LHC run.
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MOPAB130	Cross-Calibration of the LHC Transverse Beam-Profile Monitors	emittance, optics, proton, experiment	437
	R. Alemany-Fernández, F. Alessio, A. Alexopoulos, C. Barschel, F.S. Carlier, J.M. Coello de Portugal, M. Ferro-Luzzi, A. Garcia-Tabares, M. Hostettler, O. Karacheban, E.H. Maclean, R. Matev, T. Persson, P.K. Skowroński, R. Tomás, G. Trad, S. Vlachos, B. Würkner CERN, Geneva, Switzerland G.R. Coombs EPFL, Lausanne, Switzerland T.B. Hadavizadeh Oxford University, Physics Department, Oxford, Oxon, United Kingdom M. Hofer TU Vienna, Wien, Austria L. van Riesen-Haupt University of Oxford, Oxford, United Kingdom
	Calibration of a transverse beam profile monitor is of fundamental importance to guarantee the best possible accuracy and reliability of the instrument over time. In LHC the calibration standard for transverse-profile measurements are the wire scanners. Other profile monitors such as beam synchrotron light telescopes and interferometers are calibrated with respect to them. Additional information about single-bunch sizes can be obtained from beam-gas imaging in the LHCb vertex detector, from the transverse convolved beam sizes extracted from luminosity scans at the collision points, and from the evolution of the luminous-region parameters as reconstructed by ATLAS and CMS inner tracker detectors during such scans. For the first time in LHC, a dedicated cross-calibration of all the above-mentioned systems was carried out with beam in 2016. Additionally, dedicated optics measurements were also performed in order to determine with the highest possible accuracy the amplitude function at the interaction points and at the position of the profile monitors. Results of these measurements are presented in this paper.
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MOPIK076	Optimization of Dynamic Aperture with Constraints on Linear Chromaticity	sextupole, coupling, simulation, lattice	705
	H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou KEK, Ibaraki, Japan
	This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.
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MOPIK077	Impact of Dynamical Stray Fields on CLIC	shielding, collimation, synchrotron, linear-collider	708
	E. Marín, D. Schulte CERN, Geneva, Switzerland B. Heilig MFGI, Budapest, Hungary J. Pfingstner University of Oslo, Oslo, Norway
	In this paper we estimate the tolerances of stray-fields variations on the Compact Linear Collider (CLIC), discuss possible sources and propose several solutions. The Beam Delivery System (BDS) is the most sensitive system of CLIC to unwanted magnetic field variations, already variations of 1 nT would reduce the luminosity by 10% at wavelengths comparable to the BDS without considering any correction mechanism. Two sources of magnetic field variations are considered, natural and man-made. Precise magnetic field measurements at Earth's surface under a typical geomagnetic storm are presented. Additionally, stray field measurements have been conducted at CERN, to inspect B-field variations due to technical equipment in an accelerator environment. Different solutions are proposed to minimise the impact of stray fields on the CLIC performance.
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MOPIK099	Tuning-Based Design Optimization of CLIC Final Focus System at 3 TeV	sextupole, lattice, collider, linear-collider	760
	F. Plassard, A. Latina, E. Marín, D. Schulte, R. Tomás CERN, Geneva, Switzerland P. Bambade LAL, Orsay, France
	The tuning aims to mitigate static imperfections of the Final Focus System (FFS) for emittance preservation at the Interaction Point (IP). A simulation campaign on the nominal CLIC FFS at 3 TeV have shown the need of rethink the design in order to ease the tuning of the machine. The goal is to optimize the lattice in order to make the FFS more tolerant to misalignments by reducing the strength of the sextupoles. The tuning efficiency is promoted as figure of merit to find the optimal layout of the FFS. A comparative study of the tuning performances have been performed for two L* options.
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MOPIK100	Beam Delivery System Optimization for CLIC 380 GeV	sextupole, lattice, quadrupole, optics	764
	F. Plassard, A. Latina, E. Marín, D. Schulte, R. Tomás CERN, Geneva, Switzerland P. Bambade LAL, Orsay, France
	In the framework of the CLIC rebaselining, the Beam Delivery System (BDS) have been re-optimized for its initial stage at 380 GeV. Two BDS designs with L=4.3 meters and L=6 meters have been investigated. The optimization of the lattices and the beam parameters at the interaction point (IP) have been performed by taking into account their energy upgrade to 3 TeV and the tuning feasibility of the BDS in presence of static imperfections.
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MOPIK108	Tuning Simulations for the CLIC Traditional Beam Delivery System	simulation, lattice, collider, linear-collider	788
	R.M. Bodenstein, P. Burrows JAI, Oxford, United Kingdom E. Marín, F. Plassard, R. Tomás CERN, Geneva, Switzerland
	As the design of the CLIC Beam Delivery System (BDS) evolves, tuning simulations must be performed on each of the proposed lattice designs to see which system achieves the highest luminosity in the most realistic manner. This work will focus on the tuning simulations performed on the so-called Traditional lattice design for the center-of-mass energy of 3 TeV. The lattice modifications required to target the most important aberrations and the latest tuning results will be presented.
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MOPVA023	Luminosity Increase in Laser-Compton Scattering by Crab Crossing Method	laser, electron, photon, scattering	902
	Y. Koshiba, D. Igarashi, S. Ota, T. Takahashi, M. Washio RISE, Tokyo, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan J. Urakawa KEK, Ibaraki, Japan
	In collider experiments such as KEKB, crab crossing method is a promising way to increase the luminosity. We are planning to apply crab crossing to laser-Compton scattering, which is a collision of electron beam and laser, to gain a higher luminosity leading to a higher flux X-ray source. It is well known that the collision angle between electron beam and laser affects the luminosity. It is the best when the collision angle is zero, head-on collision, to get a higher luminosity but difficult to construct such system especially when using an optical cavity for laser. Concerning this difficulty, we are planning crab crossing by tilting the electron beam using an rf-deflector. Although crab crossing in laser-Compton scattering has been already proposed, nowhere has demonstrated yet. We are going to demonstrate and conduct experimental study at our compact accelerator system in Waseda University. In this conference, we will report about our compact accelerator system, laser system for laser-Compton scattering, and expected results of crab crossing laser-Compton scattering. Variola Alessandro, et al. Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators. Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
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MOPVA102	Modeling the Low Level RF Response on the Beam during Crab Cavity Quench	cavity, simulation, SRF, klystron	1098
	R. Apsimon, G. Burt, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.B. Appleby UMAN, Manchester, United Kingdom P. Baudrenghien, K.N. Sjobak CERN, Geneva, Switzerland
	The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.
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MOPVA106	Experimental Studies of Asymmetric Dual Axis Cavity for Energy Recovery LINAC	cavity, electron, linac, radiation	1105
	I.V. Konoplev, A.J. Lancaster, K. Metodiev, A. Seryi JAI, Oxford, United Kingdom R. Ainsworth Fermilab, Batavia, Illinois, USA G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
	Funding: The Leverhulme Trust via International Network Grant (IN-2015-012). Increasing the beam charge and repetition rate leads to appearance of beam break-up instabilities in conventional ERLs. At this stage the highest current, from the SRF ERL, is around 300mA. A single turn, dual axis, compact Asymmetric Energy Recovery LINAC (AERL) was proposed. The concept assumes the use of electron beams with energies up to 300 MeV and peak currents >1A, enabling the generation of high flux EUV/X-rays and THz radiation using conventional approaches. System allows beam to be transported through each stage i.e. the acceleration, interaction and deceleration only once partially removing the feedback thus increasing the instability start current. This further improved by tuning the individual cells allowing only operating mode to be uniform inside the cavity. We present the studies of 7 cells, aluminium alloy prototype of the cavity and discuss the experimental results. We show that HOMs excited on the different axis have different R/Q factors and show the field structures of operating mode and HOMs. The experimental results observed are in good agreement with theoretical predictions and the full scale copper prototype is demonstrated.
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MOPVA135	Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade	cavity, dipole, HOM, cryogenics	1174
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA H. Park JLab, Newport News, Virginia, USA
	The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.
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TUPAB016	The CLIC Main Linac Module Updated Design	alignment, linac, klystron, operation	1345
	C. Rossi, M. Aicheler, N. Catalán Lasheras, R. Corsini, S. Döbert, A. Grudiev, A. Latina, H. Mainaud Durand, M. Modena, H. Schmickler, D. Schulte, S. Stapnes, I. Syratchev, A.L. Vamvakas, W. Wuensch CERN, Geneva, Switzerland M. Aicheler HIP, University of Helsinki, Finland
	In 2016, CLIC implementation working groups have started their reflection on how to finalize the CLIC design work in the different areas of the project, aiming for a technical design and an overall implementation plan for CLIC being available for the next European Strategy Update around 2019. One of the working groups has focused its attention on the Main Linac hardware, which has brought together the different competences of the study with the aim of producing an advanced set of specifications for the design, installation and operation of the CLIC module. As the fundamental unit for the construction of the Main Beam linac, the CLIC module needs to move from the existing prototypes exploring its performance into an advanced and functional unit where the full life cycle of the module is considered. The progress of the working group activity is summarized in this paper, with considerations on the requirements for the design of the next-phase CLIC module.
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TUPAB060	Development of the Laser System for the Proof-of-Principle Experiment of Crab Crossing Laser-Compton Scattering	laser, scattering, electron, experiment	1460
	T. Takahashi, D. Igarashi, Y. Koshiba, S. Ota, M. Washio RISE, Tokyo, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan J. Urakawa KEK, Ibaraki, Japan
	An X-ray source via laser-Compton scattering has the advantage of small source, energy tunability and quasi-monochromaticity and is expected to be applied in a wide range of fields such as the industry and medical care. In laser-Compton scattering, the luminosity, which represents the collision frequency between the electrons and the photons, is very important. Increasing the luminosity is strongly required for increasing the scattered photon flux. One way to increase the luminosity is tilting electron bunches at the collision point, which is called crab crossing. It is the way to create the head-on collision artificially. The purpose of this study is the proof-of-principle of the crab crossing laser-Compton scattering. In this conference, we will report the design optimization and construction of the laser system for the collision and future prospects. Variola Alessandro, et al. Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators. Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
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TUPIK037	Proton Cross-Talk and Losses in the Dispersion Suppressor Regions at the FCC-hh	proton, simulation, collimation, quadrupole	1763
	H. Rafique, R.B. Appleby UMAN, Manchester, United Kingdom J.L. Abelleira JAI, Oxford, United Kingdom A.M. Krainer, A. Langner CERN, Geneva, Switzerland
	Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305 Protons that collide at the interaction points of the FCC-hh may contribute to the background in the subsequent detector. Due to the high luminosity of the proton beams this may be of concern. Using DPMJET-III to model 50 TeV proton-proton collisions, tracking studies have been performed with PTC and MERLIN in order to gauge the elastic and inelastic proton cross-talk. High arc losses, particularly in the dispersion suppressor regions, have been revealed. These losses originate mainly from particles with a momentum deviation, either from interaction with a primary collimator in the betatron cleaning insertion, or from the proton-proton collisions. This issue can be mitigated by introducing additional collimators in the dispersion suppressor region. The specific design, lattice integration, and the effect of these collimators on cross-talk is assessed.
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TUPIK059	Recent Progress of Dithering System at SuperKEKB	feedback, background, optics, electronics	1827
	Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, S. Nakamura, K. Ohmi, T. Oki, S. Uehara KEK, Ibaraki, Japan P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault LAL, Orsay, France A.S. Fisher SLAC, Menlo Park, California, USA U. Wienands ANL, Argonne, Illinois, USA
	Recent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described.
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TUPIK089	Studies on Luminous Region, Pile-up and Performance for HL-LHC Scenarios	operation, simulation, optics, detector	1908
	L.E. Medina Medrano, G. Arduini, R. Tomás CERN, Geneva, Switzerland L.E. Medina Medrano UGTO, Leon, Mexico
	Funding: Research supported by the HL-LHC project and the Beam project (CONACYT, Mexico). Studies on luminous region and pile-up density are of great interest for the experiments at the future High Luminosity LHC (HL-LHC) in order to optimize the detector performance. The evolution of these parameters at the two main interaction points of the HL-LHC along optimum physics fills is studied for the baseline and alternative operational scenarios with the latest set of parameters, including a refined description of the longitudinal bunch profile. Results are discussed in terms of a new figure-of-merit, the effective pile-up density.
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TUPIK111	IP Feedback Ground Motion Simulation Studies for the ILC	feedback, ground-motion, simulation, collider	1983
	R.M. Bodenstein, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan JAI, Oxford, United Kingdom J. Pfingstner CERN, Geneva, Switzerland
	The International Linear Collider (ILC), as described in its Technical Design Report (TDR), must maintain strict control of its electron and positron beams in order to achieve the desired luminosity at each of its proposed center-of-mass energies. Controlling the beam parameters requires a dynamic system, capable of adjusting to a myriad of perturbations and errors. One of the components used to control the beam is the Interaction Point (IP) feedback system, which is used to dynamically steer the beams back into collision within nanoseconds. This work will show the simulation of the IP Feedback system's compensation for ground motion model K at the ILC.
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TUPVA005	Impact of the Crossing Angle on Luminosity Asymmetries at the LHC in 2016 Proton Physics Operation	experiment, emittance, operation, proton	2035
	M. Hostettler LHEP, Bern, Switzerland F. Antoniou, I. Efthymiopoulos, K. Fuchsberger, G. Iadarola, N. Karastathis, M. Lamont, Y. Papaphilippou, G. Papotti, J. Wenninger CERN, Geneva, Switzerland
	During 2016 proton physics operation at the CERN Large Hadron Collider (LHC), an asymmetry of up to 10% was observed between the luminosities measured by the ATLAS and CMS experiments. As the same bunch pairs collide in both experiments, a difference in luminosities must be of either geometric or instrumental origin. This paper quantifies the impact of the crossing angle on this asymmetry. As the beams cross in different planes in the two experiments, non-round beams are expected to yield an asymmetry due to the crossing angle. Results from crossing angle measurements at both experiments are also shown and the impact on the luminosities is evaluated.
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TUPVA006	Lessons Learnt from the 2016 LHC Run and Prospects for HL-LHC Availability	proton, target, radiation, operation	2039
	A. Apollonio, O. Rey Orozko, R. Schmidt, M. Valette, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	The LHC exhibited unprecedented availability during the 2016 proton run, producing about 40 fb-1 of integrated luminosity, surpassing the sum of production during the 4 previous years. This was achieved while running steadily with a peak luminosity above the design target of 1034 cm- 2s⁻¹. Individual system performance and an increased experience operating the LHC were fundamental for these achievements, following the consolidations and improvements deployed during the Long Shutdown 1 and the Year End Technical Stop in 2015. The implications of this excellent performance in the context of the High Luminosity LHC are discussed in this paper, with the goal of defining the possible integrated luminosity reach of HL-LHC when considering the different operating conditions and the newly developed systems and technologies.
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TUPVA007	Impact of LHC and SPS Injection Kicker Rise Times on Lhc Filling Schemes and Luminosity Reach	injection, kicker, emittance, timing	2043
	W. Bartmann, M.J. Barnes, J. Boyd, E. Carlier, A. Chmielinska, B. Goddard, G. Kotzian, C. Schwick, L.S. Stoel, D. Valuch, F.M. Velotti, V. Vlachodimitropoulos, C. Wiesner CERN, Geneva, Switzerland
	The 2016 LHC proton filling schemes generally used a spacing between injections of batches of bunches into SPS and LHC corresponding to the design report specification for the SPS and LHC injection kicker rise times, respectively. A reduction of the batch spacing can be directly used to increase luminosity without detrimental effects on beam stability, and with no increase in the number of events per crossing seen by the experiments. Measurements and simulations were performed in SPS and LHC to understand if a shorter injection kicker rise time and associated tighter batch spacing would lead to increased injection oscillations of the first and last bunches of a bunch train and eventually also a systematic growth of the transverse emittance. The results were used to define the minimum possible batch spacing for an acceptable emittance growth in LHC, with gains of reductions of about 10% possible in both machines. The results are discussed, including the potential improvement of the LHC luminosity for different filling schemes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA007
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TUPVA009	Multiparametric Response of the LHC Dynamic Aperture in Presence of Beam-Beam Effects	emittance, simulation, optics, octupole	2051
	D. Pellegrini, F. Antoniou, S.D. Fartoukh, G. Iadarola, Y. Papaphilippou CERN, Geneva, Switzerland
	We performed extended simulations of LHC dynamic aperture (DA) in the presence of beam-beam effects in the weak-strong approximation, evaluating the contributions of parameters such as: tunes, optics, bunch intensity, crossing angle, emittance, chromaticity and current in the Landau octupoles. Here we present a summary of these studies, giving an overview of the amplitude of the LHC operational space and pointing out the remaining margins for mitigation of instabilities. These studies supported the actions deployed during the 2016 run of the LHC, which aimed at maximising its performances. Examples of such actions are the switch to lower emittance beams, the reduction of crossing angle and tune trims. More recently, DA scans have been used to help the definition of the operational scenarios for the 2017 run. Additional room for improvements, for instance by deploying crossing angle levelling, will be explained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA009
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TUPVA010	Multiparametric Response of the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects	octupole, simulation, beam-beam-effects, emittance	2055
	D. Pellegrini, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou CERN, Geneva, Switzerland
	We performed extended simulations of HL-LHC dynamic aperture in the presence of beam-beam effects in the weak- strong approximation, evaluating the contributions of param- eters such as: bunch intensity, crossing angle, chromaticity, current in the Landau octupoles and multipole errors. From the beam dynamics point of view, the main differ- ence between the LHC (until 2017) and the HL-LHC is the deployment of the achromatic telescopic squeezing (ATS) optics, allowing not only for a smaller '' reach, but also modifying the phase advances between the lattice correctors (sextupoles, octupoles) and the main IPs, and increasing the peak ' functions in the arcs. These correctors become therefore more efficient for the chromatic correction, but also a mitigation of the beam-beam long range interactions using the Landau octupoles is enabled, resulting in a possible reduction of the normalised crossing angle. The limits have been investigated in a tracking simulation campaign aimed at exploring the operational space for the HL-LHC and two possible options for luminosity levelling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA010
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TUPVA013	Lifetime of Asymmetric Colliding Beams in the LHC	simulation, proton, coupling, ion	2067
	J.M. Jowett, R. Alemany-Fernández, M.A. Jebramcik, T. Mertens, M. Schaumann CERN, Geneva, Switzerland
	In the 2013 proton-nucleus (p-Pb) run of the LHC, the lifetime of the lead beam was significantly shorter than could be accounted for by luminosity burn-off. These effects were observed at a lower level in 2016 and studied in more detail. The beams were not only asymmetric but the differences in the bunch filling schemes between protons and Pb nuclei led to a wide variety of beam-beam interaction sequences in the bunch trains. The colliding bunches were also of different sizes. We present an analysis of the data and an interpretation in terms of theoretical models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA013
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TUPVA014	The 2016 Proton-Nucleus Run of the LHC	proton, experiment, operation, ion	2071
	J.M. Jowett, R. Alemany-Fernández, G. Baud, P. Baudrenghien, R. De Maria, R. De Maria, D. Jacquet, M.A. Jebramcik, A. Mereghetti, T. Mertens, M. Schaumann, H. Timko, M. Wendt, J. Wenninger CERN, Geneva, Switzerland
	For five of the LHC experiments the second p-Pb collision run planned in 2016 offered the opportunity to answer a range of important physics questions arising from the surprise discoveries (e.g., flow-like collective phenomena in small systems) made in earlier Pb-Pb, p-Pb and p-p runs. However the diversity of the physics and their respective capabilities led them to request very different operating conditions, in terms of collision energy, luminosity and pile-up. These appeared mutually incompatible within the available one month of operation. Nevertheless, a plan to satisfy most requirements was developed and implemented successfully. It exploited different beam lifetimes at two beam energies of 4 Z TeV and 6.5 Z TeV, a variety of luminosity sharing and bunch filling schemes, and varying beam directions. The outcome of this very complex strategy for repeated re-commissioning and operation of the LHC included the longest ever LHC fill with luminosity levelled for almost 38 h. The peak luminosity achieved exceeded the design value by a factor 7.8 and integrated luminosity substantially exceeded the experiments' requests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA014
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TUPVA015	Radiation Levels at the LHC: 2012, 2015 and 2016 Proton Physics Operations in View of HL-LHC requirements	radiation, operation, proton, insertion	2075
	C. Martinella, M. Brugger, S. Danzeca, R. Garcia Alia, Y. Kadi, O. Stein, C. Xu CERN, Geneva, Switzerland
	The variety of beam losses produced in the Large Hadron Collider (LHC) creates a mixed and complex radiation field. During 2012, 2015 and 2016, Beam Loss Monitors and RadMons were used to monitor the inte-grated dose and the High Energy Hadrons fluence in order to anticipate the electronics degradation and inves-tigate the cause of failures. The annual radiation levels are compared; highlighting the mechanisms in the pro-duction of beam losses and the impact of the different squeeze and crossing angle. In addition, the increase of beam-gas interaction is discussed comparing operations at 25 ns and 50 ns bunch spacing. A strategy is presented to allow for a continuous respective evaluation during the upcoming LHC and future High Luminosity LHC (HL-LHC) operations.
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TUPVA016	Identification and Analysis of Prompt Dose Maxima in the Insertion Regions IR1 and IR5 of the Large Hadron Collider	radiation, operation, dipole, quadrupole	2078
	O. Stein, M. Brugger, S. Danzeca, R. Garcia Alia, Y. Kadi, M. Kastriotou, C. Martinella, C. Xu CERN, Geneva, Switzerland
	During the operation of the LHC the continuous particle losses create a radiation field in the LHC tunnel and the adjacent caverns. Exposed electronics and accelerator components show dose dependent accelerated aging effects and stochastic Single Event Effects which can lead to faults and downtime of the LHC. In order to achieve an optimal life duration, the position of the equipment is chosen in dependency of the amplitude of the radiation fields. Therefore, it is crucial to monitor the prompt dose distributions along the whole LHC. By using the LHC beam loss monitor and RadMon systems, the prompt dose during the accelerator operation is continuously monitored. Measurements in the long straight sections and the dispersion suppressors in IR1 (ATLAS) and in IR5 (CMS) have shown that the radiation levels have localised maxima which exceed the base line by 1 to 2 orders of magnitude. The analysis of these radiation peaks will be presented and the underlying loss mechanisms will be discussed. The results will help to identify areas not suitable for radiation sensitive electronics. Implications on the expected radiation levels for High-Luminosity LHC are also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA016
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TUPVA020	The LHC Injectors Upgrade (LIU) Project at CERN: Ion Injector Chain	ion, injection, extraction, kicker	2089
	H. Bartosik, S.C.P. Albright, M.E. Angoletta, G. Bellodi, N. Biancacci, T. Bohl, J. Coupard, H. Damerau, A. Funken, B. Goddard, S. Hancock, K. Hanke, A. Huschauer, J.M. Jowett, V. Kain, D. Küchler, D. Manglunki, M. Meddahi, G. Rumolo, R. Scrivens, E.N. Shaposhnikova, V. Toivanen, F.J.C. Wenander CERN, Geneva, Switzerland
	The LHC injector chain for Pb-ion beams at CERN consists of Linac3, the accumulator ring LEIR, the PS and the SPS. In the context of the LHC injectors upgrade (LIU) project an intense program of machine development studies has been performed in the last two years to maximise the intensity of Pb-ion beams at LHC injection. In this paper we present an analysis of the operational performance achieved so far, with the goal of 1) identifying the remaining performance bottlenecks along the chain and possible areas for improvement, and 2) to optimize the Pb-ion beam production scheme for the High Luminosity (HL-) LHC era. A consistent set of beam parameters for the HL-LHC era has been established taking into account the already achieved improvements as well as foreseen upgrades still to be implemented, such as slip stacking in the SPS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA020
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TUPVA021	Impact of Collision Debris in the HL-LHC ATLAS and CMS Insertions	proton, optics, insertion, radiation	2093
	A. Tsinganis, F. Cerutti CERN, Geneva, Switzerland
	The High Luminosity upgrade of the LHC (HL-LHC) foresees the baseline operation of the accelerator at a 5 times higher peak luminosity (5.0x1034cm^-2s⁻¹). The impact of collision debris on the magnets and other equipment in the triplet region and matching section of the ATLAS and CMS insertions has been evaluated by means of detailed FLUKA models implementing the latest optics and layout version. Qualitative and quantitative differences between the vertical and horizontal beam crossing schemes are highlighted. With measures in place to mitigate the effects of the interruption of the beam screen in the triplet interconnections and the Q4 aperture reduction, peak dose values in the superconducting coils remain below 30MGy in the triplet-D1 and below 12MGy in the matching section magnets for an integrated luminosity of 3000fb-1. Peak power density values are lower than 3mW/cm³ and 1mW/cm³ in the triplet and matching section respectively. Total heat loads in magnets, collimators, masks and absorbers were also estimated, along with dose and particle fluence maps relevant for Radiation to Electronics (R2E) aspects. The effect of a displacement of the interaction point is also addressed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA021
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TUPVA022	Requirements for Crab Cavity System Availability in HL-LHC	cavity, optics, operation, proton	2097
	M. Valette, A. Apollonio, J.A. Uythoven, D. Wollmann CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project. Crab Cavities will be installed in the High Luminosity LHC in order to increase the effective peak luminosity through a partial compensation of the geometric factor. This will allow extending the levelling time resulting in an increased production of integrated luminosity. Based on the availability of the LHC during 2016 operation, the expected yearly-integrated luminosity of the future HL-LHC was estimated using a Monte Carlo model. Crab cavity faults were added to the observed failure distribu-tions and their impact on integrated luminosity produc-tion as a function of fault time and fault frequency was studied. This allows identifying a breakeven point in luminosity production and defining minimum system availability requirements for the crab cavities to reach the design goal of 250 fb-1 of integrated luminosity per year.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA022
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TUPVA025	Observations of Beam Losses at the LHC During Reduction of Crossing Angle	experiment, beam-losses, proton, beam-beam-effects	2105
	B. Salvachua, X. Buffat, A.A. Gorzawski, T. Pieloni, S. Redaelli, C. Tambasco, J. Wenninger CERN, Geneva, Switzerland J. Barranco García, A.A. Gorzawski EPFL, Lausanne, Switzerland M.P. Crouch UMAN, Manchester, United Kingdom
	Several machine development studies have been performed in 2016 at the LHC in order to evaluate the effects of reducing the crossing angles in favor of defining the maximum achievable luminosity in the ATLAS and CMS experiments. At the end of the LHC proton-proton run at 6.5TeV the reduction of the crossing angle from 185urad to 140urad was operationally implemented. The observation of beam losses and lifetimes during this process are analysed and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA025
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TUPVA026	Beam-Beam Studies for FCC-hh	optics, simulation, dynamic-aperture, resonance	2109
	J. Barranco García, T. Pieloni, C. Tambasco EPFL, Lausanne, Switzerland X. Buffat, S.V. Furuseth, C. Tambasco CERN, Geneva, Switzerland S.V. Furuseth NTNU, Trondheim, Norway
	Funding: This works was performed in the framework of the European Circular 'Energy Fr'ontier Collider Study, H2020 Framework Programme under grant agreement no. 654305. We acknowledge support from the Swiss State Secretariat for Education, Research and Innovation SERI. The Future Circular Collider hadron-hadron (FCC-hh) design study is currently exploring different IR design possibilities including round and flat optics or different crossing schemes. The present study intends to evaluate each scenario from the beam-beam effects point of view. In particular the single particle long term stability to maximize beam lifetimes and luminosity reach is used to quantify the differences. The impact of strong head on interactions on the beam quality and lifetime is addressed by means of GPU accelerated simulations code featuring a weak-strong 6-dimensional beam-beam interaction.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA026
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TUPVA032	Beam-Gas Background Observations at LHC	background, experiment, detector, simulation	2129
	S.M. Gibson Royal Holloway, University of London, Surrey, United Kingdom R. Alemany-Fernández, F. Alessio, G. Bregliozzi, H. Burkhardt, G. Corti, A. Di Mauro, M. Guthoff, A. Manousos, K.N. Sjobak, C. Yin Vallgren CERN, Geneva, Switzerland A. Alici Bologna University, Bologna, Italy S. D'Auria University of Glasgow, Glasgow, United Kingdom S.M. Gibson JAI, Egham, Surrey, United Kingdom D. Lazic BUphy, Boston, Massachusetts, USA
	Observations of beam-induced background at LHC during 2015 and 2016 are presented in this paper. The four LHC experiments use the non-colliding bunches present in the physics-filling pattern of the accelerator to trigger on beam-gas interactions. During luminosity production the LHC experiments record the beam-gas interactions using dedicated background monitors. These data are sent to the LHC control system and are used to monitor the background levels at the experiments during accelerator operation. This is a very important measurement, since poor beam-induced background conditions can seriously affect the performance of the detectors. A summary of the evolution of the background levels during 2015 and 2016 is given in these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA032
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TUPVA034	SPS Studies in Preparation for the Crab Cavity Experiment	emittance, experiment, cavity, simulation	2133
	A. Alekou, A. Alekou, F. Antoniou, F. Antoniou, G. Arduini, G. Arduini, H. Bartosik, H. Bartosik, R. Calaga, R. Calaga, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou CERN, Geneva, Switzerland A. Alekou, R.B. Appleby, R.B. Appleby UMAN, Manchester, United Kingdom R.B. Appleby, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	A local Crab Cavity (CC) scheme will recover head-on collisions at the Interaction Points (IPs) of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The first time that CC will ever be tested with proton beams will be in 2018 in the SPS machine. The available dedicated Machine Development (MD) time after the installation of the cavities will be limited and therefore good preparation is essential in order to ensure that the MDs are as efficient as possible. This paper presents the simulations and experimental studies performed in preparation for the future MDs and discusses the next steps.
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TUPVA037	FCC-hh Final-Focus for Flat-Beams: Parameters and Energy Deposition Studies	optics, collider, quadrupole, hadron	2139
	J.L. Abelleira, E. Cruz Alaniz, A. Seryi, L. van Riesen-Haupt JAI, Oxford, United Kingdom M.I. Besana CERN, Geneva, Switzerland
	Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305. The international Future Circular Collider (FCC) study comprises the study of a new scientific structure in a tunnel of 100 km. This will allow the installation of two accelerators, a 45.6'175 GeV lepton collider and a 100-TeV hadron collider. An optimized design of a final-focus system for the hadron collider is presented here. The new design is more compact and enables unequal β^* in both planes, whose choice is justified here. This is followed by energy deposition studies, where the total dose in the magnets as a consequence of the collision debris is evaluated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA037
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TUPVA040	Overview of Design Development of FCC-hh Experimental Interaction Regions	optics, detector, dipole, experiment	2151
	A. Seryi, J.L. Abelleira, E. Cruz Alaniz, L.J. Nevay, L. van Riesen-Haupt JAI, Oxford, United Kingdom R.B. Appleby, H. Rafique UMAN, Manchester, United Kingdom R.B. Appleby Cockcroft Institute, Warrington, Cheshire, United Kingdom J. Barranco García, T. Pieloni EPFL, Lausanne, Switzerland M. Benedikt, M.I. Besana, X. Buffat, H. Burkhardt, F. Cerutti, A. Langner, R. Martin, W. Riegler, D. Schulte, R. Tomás CERN, Geneva, Switzerland M. Boscolo, F. Collamati INFN/LNF, Frascati (Roma), Italy M. Hofer TU Vienna, Wien, Austria L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom L. van Riesen-Haupt University of Oxford, Oxford, United Kingdom
	The experimental interaction region is one of the key areas that define the performance of the Future Circular Collider. In this overview we will describe the status and the evolution of the design of EIR of FCC-hh, focusing on design of the optics, energy deposition in EIR elements, beam-beam effects and machine detector interface issues.
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TUPVA044	Modelling and Measurements of Bunch Profiles at the LHC	emittance, synchrotron, radiation, scattering	2167
	S. Papadopoulou, F. Antoniou, T. Argyropoulos, M. Hostettler, Y. Papaphilippou CERN, Geneva, Switzerland M. Fitterer Fermilab, Batavia, Illinois, USA
	The bunch profiles in the LHC are often observed to be non-Gaussian, both at Flat Bottom (FB) and Flat Top (FT) energies. Especially at FT, an evolution of the tail population in time is observed. In this respect, the Monte-Carlo Software for IBS and Radiation effects (SIRE) is used to track different types of beam distributions. The impact of the distribution shape on the evolution of bunch characteristics is studied. The results are compared with observations from the LHC Run 2 data.
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TUPVA050	RHIC Polarized Proton Operation for 2017	resonance, lattice, polarization, injection	2188
	V.H. Ranjbar, P. Adams, Z. Altinbas, E.C. Aschenauer, G. Atoian, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, M.R. Costanzo, T. D'Ottavio, K.A. Drees, P.S. Dyer, A.V. Fedotov, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, C.E. Harper, M. Harvey, T. Hayes, J. Hock, H. Huang, R.L. Hulsart, J.P. Jamilkowski, T. Kanesue, N.A. Kling, J.S. Laster, C. Liu, Y. Luo, D. Maffei, M. Mapes, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, T.A. Miller, M.G. Minty, C. Montag, J. Morris, G. Narayan, C. Naylor, S. Nemesure, P. Oddo, M. Okamura, S. Perez, A.I. Pikin, A. Poblaguev, S. Polizzo, V. Ptitsyn, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, W.B. Schmidke, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, Z. Sorrell, D. Steski, S. Tepikian, R. Than, P. Thieberger, J.E. Tuozzolo, G. Wang, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, W. Zhang, B. van Kuik BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the US Department of Energy under contract number DE-SC0012704 The 2017 operation of the Relativistic Heavy Ion Collider (RHIC) involved the running of only a single experiment at STAR with PHENIX offline in the process of the upgrade to sPHENIX. For this run there were several notable changes to machine operations. These included, transverse polarization, luminosity leveling, a new approach to machine protection and the development of new store and ramped lattices. The new 255 GeV store lattice was designed to both accommodate the necessary phase advance between the e-lens and IP8 for testing and to maximize dynamic aperture. The new lattices on the ramp were designed to maximize polarization transmission during the three strong intrinsic spin resonances crossings. Finally we are also commissioning new 9 MHz RF cavities during this run.
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TUPVA130	CLIC Tuning Performance Under Realistic Error Conditions	collider, target, linear-collider, alignment	2403
	E. Marín, A. Latina, F. Plassard, D. Schulte, R. Tomás CERN, Geneva, Switzerland
	In this paper we present the latest results regarding the tuning study of the baseline design of the CLIC Final Focus System. In previous studies, 90% of the machines reach 90% of the nominal luminosity, when considering beam position monitor errors and transverse misalignments of magnets for a single beam case. In the present study, roll misalignments and strength errors are also included for both e^- and e⁺ beamlines, making the study a more realistic one. First, second and third order knobs are implemented in the tuning procedure to target the most relevant beam size aberrations. In order to minimise the total number of luminosity measurements a simultaneous scan of various knobs has been developed to cope with the non-fully orthogonality of the knobs. The obtained results for single and double beam studies are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA130
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WEYA1	Crab Cavity Systems for Future Colliders	cavity, collider, electron, proton	2474
	S. Verdú-Andrés, I. Ben-Zvi, Q. Wu BNL, Upton, Long Island, New York, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA R. Calaga CERN, Geneva, Switzerland
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy, by the US LARP program and by the HL-LHC project. KEKB was the first facility to implement the crab crossing technique in 2007, for the interaction of electron and positron beams. The High Luminosity Large Hadron Collider (HL-LHC) project envisages the use of crab cavities for increasing and levelling the luminosity of proton-proton collisions in LHC. Crab cavities have also been proposed and studied for future colliders like CLIC, ILC and eRHIC. This contribution will focus on the near and far future of crab cavities for particle colliders.
	Slides WEYA1 [6.571 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEYA1
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WEOAB2	Correction of Beta-Beating Due to Beam-Beam for the LHC and Its Impact on Dynamic Aperture	sextupole, optics, quadrupole, dynamic-aperture	2512
	L.E. Medina Medrano, J. Barranco García, X. Buffat, Y. Papaphilippou, T. Pieloni, R. Tomás CERN, Geneva, Switzerland J. Barranco García, T. Pieloni EPFL, Lausanne, Switzerland L.E. Medina Medrano UGTO, Leon, Mexico
	Funding: This work is supported by the European Circular Energy-Frontier Collider Study, H2020 programme under grant agreement no. 654305, by the Swiss State Secretariat for Education, Research and Innovation SERI, and by the Beam project (CONACYT, Mexico). Minimization of the beta-beating at the two main interaction points of the LHC arising from the head-on and long-range beam-beam interactions can be performed by adjusting the strength of quadrupole or sextupole correctors. This compensation scheme is applied to the current LHC optics where the results show a significant reduction of the peak and RMS beta-beating; and the impact on the dynamic aperture is computed. A proposal for a similar strategy to be adopted in the High Luminosity LHC is also discussed.
	Slides WEOAB2 [6.292 MB]
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WEPIK004	Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design	detector, background, photon, interaction-region	2914
	G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani CERN, Geneva, Switzerland N. Bacchetta INFN- Sez. di Padova, Padova, Italy M. Boscolo INFN/LNF, Frascati (Roma), Italy M.K. Sullivan SLAC, Menlo Park, California, USA
	A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK004
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WEPIK010	Commissioning Status of SuperKEKB Main Ring Magnet System	operation, power-supply, dipole, interaction-region	2933
	M. Masuzawa, T. Adachi, K. Egawa, T. Kawamoto, S. Nakamura, Y. Ohsawa, T. Oki, R. Sugahara, R. Ueki KEK, Ibaraki, Japan
	SuperKEKB is an electron-positron collider, which aims for the very high peak luminosity of 8x10³⁵ cm^-2s^-1 , 40 times higher than that of KEKB. The SuperKEKB Main Ring (MR) system is very large, consisting of more than 1700 water-cooled normal-conducting magnets and about 900 air-cooled normal-conducting magnets. More than 400 magnets and power supplies were newly fabricated, tested and installed for SuperKEKB Phase I beam operation. The MR magnet system worked well, which contributed greatly to the smooth start-up of the MR. Commissioning status of the MR magnet system during SuperKEKB Phase I operation will be reported. Some problems resulting in beam abort will also be reported.
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WEPIK015	Optimized Monochromatization for Direct Higgs Production in Future Circular e⁺e⁻ Colliders	collider, emittance, radiation, electron	2950
	F. Zimmermann CERN, Geneva, Switzerland M.A. Valdivia García DCI-UG, León, Mexico
	Funding: This work was supported in part by the European Commission under the HORIZON2020 Integrating Activity project ARIES, grant agreement 730871, and by the Mexican CONACyT ‘‘BEAM'' Programme. Direct s-channel Higgs production in e⁺e⁻ collisions is of interest if the centre-of-mass energy spread can be reduced to be comparable to the width of the standard model Higgs boson. A monochromatization scheme could be employed in order to achieve the desired reduction, by introducing a non-zero horizontal dispersion of opposite sign for the two colliding beams at the interaction point. In high-energy high-luminosity circular colliders, beamstrahlung may increase the energy spread and bunch length. The horizontal emittance blow up due to beamstrahlung, a new effect not present in past monochromatization proposals, may degrade the performance, especially the luminosity. We study, for the FCC-ee at 62.5 GeV beam energy, how we can optimize the IP optics parameters (betax, Dx) along with the number of particles per bunch so as to obtain maximum luminosity at a desired target value of the collision energy spread.
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WEPIK016	CEPC-SppC Towards CDR	collider, booster, positron, detector	2954
	J. Gao IHEP, Beijing, People's Republic of China
	Funding: supported by National Key Programme for S&T Research and Development (2016YFA0400400), National Natural Science Foundation of China (11575218, 11605211, 11605210, 11505198), Key Research Program of Frontier Sciences, CAS, (QYZDJ-SSW-SLH004) and CAS Center for Excellence in Particle Physics (CCEPP) In this paper we will give an introduction to Circular Electron Positron Collider (CEPC). The scientific background, physics goal, the collider design requirements and the conceptual design principle of CEPC are described. On CEPC accelerator, the optimization of parameter designs for CEPC with different energies, machine lengthes, single ring and crab-waist collision partial double ring, advanced partial double partial ring and fully partial double ring options, etc. have been discussed systematically, and compared. CEPC accelerator baseline and alternative designs have been proposed based on the luminosity potential in relation with the design goals. The sub-systems of CEPC, such as collider main ring, booster, electron positron injector, etc. ave also been introduced. The detector and MDI design have been briefly mentioned. Finally, the optimization design of Super Proton-Proton Collider (SppC), its energy and luminosity potentials, in the same tunnel of CEPC are also discussed. The CEPC-SppC Progress Report (2015-2016) has been published.
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WEPIK017	100 km CEPC Parameters and Lattice Design	sextupole, collider, dynamic-aperture, optics	2958
	D. Wang, T.J. Bian, X. Cui, J. Gao, H. Geng, Q. Qin, B. Sha, N. Wang, Y. Wang, C.H. Yu, J.Y. Zhai, C. Zhang, Y. Zhang IHEP, Beijing, People's Republic of China F. Su Institute of High Energy Physics (IHEP), People's Republic of China
	The 100km double ring configuration with shared su-perconducting RF system has been defined as baseline by the circular electron positron collider (CEPC) steering committee. Based on this new scheme, we will get higher luminosity for Higgs (+170%) keeping the beam power in preliminary conceptual design report (Pre-CDR) or to reduce the beam power (19 MW) while keeping same luminosity. CEPC will be compatible with W and Z ex-periment. The luminosity for Z is designed at the level of 1035 cm^-2s⁻¹. The requirement for the energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The optics of arc and final focus system (FFS) with crab sextupoles has been designed, and also some primary dynamic aperture (DA) results were introduced.
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WEPIK029	High Luminosity at VEPP-2000 Collider With New Injector	collider, detector, injection, positron	2989
	P.Yu. Shatunov, O.V. Belikov, D.E. Berkaev, K. Gorchakov, A.S. Kasaev, A.N. Kirpotin, I. Koop, A.A. Krasnov, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, D.V. Rabusov, Yu. A. Rogovsky, A.M. Semenov, A.I. Senchenko, Y.M. Shatunov, D.B. Shwartz, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov BINP SB RAS, Novosibirsk, Russia E. Perevedentsev, Yu. A. Rogovsky, A.I. Senchenko, D.B. Shwartz NSU, Novosibirsk, Russia
	VEPP-2000 e⁺e⁻ collider at BINP was commissioned and started data taking with two detectors in 2010 with old injection chain. In the middle energy range, where the luminosity was limited by beam-beam effects, the world record values of beam-beam parameter were achieved, ksi=0.12/IP. At the same time the design luminosity value of L = 10³² cm^-2s⁻¹ at top energy (E = 1 GeV per beam) remained unreachable due to limited e⁺ production rate. The injection chain was significantly upgraded in 2013-2016. The experience of upgraded VEPP-2000 complex operation at top energies with Round Colliding Beams will be presented.
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WEPIK030	Experimental Validation of the Achromatic Telescopic Squeezing Scheme at the LHC	optics, collimation, insertion, injection	2992
	S.D. Fartoukh, R. Bruce, F.S. Carlier, J.M. Coello de Portugal, A. Garcia-Tabares, E.H. Maclean, L. Malina, A. Mereghetti, D. Mirarchi, T. Persson, M. Pojer, L. Ponce, S. Redaelli, B. Salvachua, P.K. Skowroński, M. Solfaroli, R. Tomás, D. Valuch, A. Wegscheider, J. Wenninger CERN, Geneva, Switzerland
	The Achromatic Telescopic Squeezing (ATS) [1] scheme offers new techniques to deliver unprecedentedly small beam spot size at the interaction points of the ATLAS and CMS experiments of the LHC, while perfectly controlling the chromatic properties of the corresponding optics (linear and non-linear chromaticities, off-momentum beta-beating, spurious dispersion induced by the crossing bumps). The first series of beam tests with ATS optics were achieved during the LHC Run I (2011/2012) for a first validation of the basics of the scheme at small intensity. In 2016, a new generation of more performing ATS optics was developed and more extensively tested in the machine, still with probe beams for optics measurement and correction at β^=10 cm, but also with a few nominal bunches to establish first collisions at nominal β^ (40 cm) and beyond (33 cm), and to analysis the robustness of these optics in terms of collimation and machine protection. The paper will highlight the most relevant and conclusive results which were obtained during this second series of ATS tests. [1] S. Fartoukh , Phys. Rev. ST Accel. Beams 16, 111002
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WEPIK043	Modeling Local Crabbing Dynamics in the JLEIC Ion Collider Ring	ion, lattice, cavity, emittance	3022
	S.I. Sosa Guitron, J.R. Delayen ODU, Norfolk, Virginia, USA V.S. Morozov JLab, Newport News, Virginia, USA
	The Jefferson Lab Electron-Ion Collider (JLEIC) design considers a 50 mrad crossing angle at the Interaction Point. Without appropriate compensation, this could geometrically reduce the luminosity by an order of magnitude. A local crabbing scheme is implemented to avoid the luminosity loss: crab cavities are placed at both sides of the interaction region to restore a head-on collision scenario. In this contribution, we report on the implementation of a local crabbing scheme in the JLEIC ion ring. The effects of this correction scheme on the stability of proton bunches are analyzed using the particle tracking software elegant.
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WEPIK047	Frequency Choice Studies of eRHIC Crab Cavity	cavity, ion, electron, simulation	3028
	Y. Hao, Y. Luo, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). Since the ion beam is long when cooling is not present, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence a impact to the luminosity lifetime. In this paper, we present the initial result of the weak-strong and strong-strong beam-beam tracking with the crab crossing scheme. The result provides beam dynamics guidance in choosing the proper frequency the crab cavity for the future EIC.
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WEPIK049	Overview of the eRHIC Ring-Ring Design	electron, proton, storage-ring, polarization	3035
	C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, W. Fischer, W. Guo, Y. Hao, A. Hershcovitch, Y. Luo, F. Méot, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, S. Seletskiy, T.V. Shaftan, V.V. Smaluk, S. Tepikian, D. Trbojevic, E. Wang, F.J. Willeke, H. Witte, Q. Wu BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The ring-ring electron-ion collider eRHIC aims at an electron-ion luminosity in the range from 10³² to 10³³cm^-2sec^-1 over a center-of-mass energy range from 20 to 140GeV. To minimize the technical risk the design is based on existing technologies and beam parameters that have already been achieved routinely in hadron-hadron collisions at RHIC, and in electron-positron collisions elsewhere. This design has evolved considerably over the last two years, and a high level of maturity has been achieved. We will present the latest design status and give an overview of studies towards evaluating the feasibility.
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WEPIK050	Parameters for eRHIC	electron, proton, emittance, synchrotron	3038
	R.B. Palmer, C. Montag BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. Requirements for the proposed BNL eRHIC Ring-Ring Electron Ion Collider (EIC) are discussed, together with the dependence of luminosity with the beam divergence and forward proton acceptance. Parameters are given for four cases. The first two use no cooling and could represent a first phase of operation. The next two use strong cooling and increased beam currents. In each case parameters are given that 1) meets the requirement for forward proton acceptance, and 2) has somewhat higher divergences giving somewhat higher luminosity.
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WEPVA071	Preliminary Conceptual Study of Next Generation Tau-Charm Factory at China	factory, collider, positron, electron	3436
	Q. Luo USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by National Natural Science Foundation of China 11375178 and the Fundamental Research Funds for the Central Universities, Grant No WK2310000046 As BEPC II would accomplish its mission in the next decade, research on high energy science demands a successor. The luminosity of this successor should be one or two orders higher than BEPC II, while the electron beam should be longitudinal polarized at the IP. This paper discusses the feasibility and key technologies of the next tau-charm collider: a greenfield new facility or an upgrade of BEPC II.
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WEPVA111	Change of Critical Current Density in Nb-Ti and Nb3Sn Strands After Millisecond Heating	superconducting-magnet, experiment, dipole, collider	3528
	V. Raginel, K. Kulesz, M. Mentink, R. Schmidt, A.P. Verweij, D. Wollmann CERN, Geneva, Switzerland D. Kleiven NTNU, Trondheim, Norway
	The damage mechanisms and limits of superconducting magnet components due to direct beam impact are not well understood. The energy deposition from beam losses can cause significant temperature rise and mechanical stress in the magnet coils, which can lead to a degradation of the insulation strength and critical current of the superconductor. An improved understanding of these mechanisms is not only important for the LHC in view of the planned increase in beam brightness, but also for other high energy accelerators using superconducting magnets. An experimental road map has been defined to study these damage mechanisms. Experiments have been performed with Nb-Ti and Nb3Sn strands and cable stacks at room temperature. This contribution focuses on the experimental study on the effect of millisecond heating on superconducting strands.
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WEPVA112	Characterisation of the Mechanical Behaviour of Superconducting Cables Used in High Field Magnets From Room Temperature Down to 77K	dipole, collider, cryogenics, superconducting-magnet	3532
	O. Sacristan De Frutos, M. Daly, P. Ferracin, C. Fichera, M. Guinchard, T. Mikkola, F. Savary, G. Vallone CERN, Geneva, Switzerland
	A comprehensive knowledge of the mechanical properties of the superconducting cable used in high-field magnets is of paramount importance to study and model the behaviour of the magnet coil from assembly to the operational conditions at cryogenic temperature. The mechanical characterisation of such kind of materials presents practical challenges associated with the heterogeneity of the materials, the geometry, size and quality of the samples that can be produced out of actual cables. These constraints impose the undertaking of such measurements from a nonstandard approach, and hence the development of tailor-made tooling. An extensive characterisation campaign for the determination of the mechanical properties of the superconducting cable at room and cryogenic temperature was launched at CERN in order to determine the most relevant mechanical properties of the superconducting cables used in the MQXF and 11T magnets. This paper describes the design of the tooling developed for this specific application as well as the experimental set-up used for the tests, and discusses the outcomes of the matrix of tests performed.
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WEPVA113	Thermo-Physical and Mechanical Characterisation of Novel Materials under Development for HL-LHC Beam Intercepting Devices	radiation, experiment, laser, framework	3536
	O. Sacristan De Frutos, A. Bertarelli, L. Bianchi, F. Carra, J. Guardia, M. Guinchard, S. Redaelli CERN, Geneva, Switzerland
	Funding: The research leading to these results has received funding from the European Commission under the FP7 Research Infrastructures project EuCARD-2, grant agreement no.312453 The collimation system for high energy particle accelerators as HL-LHC, must be designed to withstand the close interaction with intense and energetic particle beams, safely operating over an extended range of temperatures in extreme conditions (pressure, strain-rate, radiation), which are to become more demanding with the High Luminosity LHC. In order to withstand such conditions, the candidate materials must possess among other properties outstanding thermal shock resistance and high thermal and electrical conductivity, condition only met by advanced or novel materials. Therefore, an extensive R&D program has been launched to develop novel materials capable of replacing or complementing materials used for present collimators. So far, Molybdenum Carbide - Graphite and Copper-Diamond composites have been identified as the most promising materials. Literature data are scarce or non-existing for these materials. For this reason the successive characterisation campaigns constitute a linchpin of the R&D program. This paper reviews the experimental program followed for the thermo-physical and mechanical characterisation of the materials, and discusses the most relevant results.
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WEPVA116	HL-LHC Inner Triplet Powering and Control Strategy	controls, quadrupole, simulation, hadron	3544
	S. Yammine, H. Thiesen CERN, Geneva, Switzerland
	In order to achieve the target 3000 fb-1 integrated field for the HL-LHC (High Luminosity ' Large Hadron Collider) at ATLAS and CMS, new large aperture quadrupoles are required for the final focusing triplet magnets before the interaction points. These low-' magnets, based on the Nb3Sn technology, deliver a peak field of 11.4 T. They consist of two outer quadrupoles, Q1 and Q3 and a central one divided into two identical magnets, Q2a and Q2b. To optimize the powering and the beam dynamics of these triplets, the quadrupoles will be powered in series by a single high-current two quadrants (2-Q) converter [18 kA, ±10 V]. Three 4-Q trim power converters are added over Q1 [±2 kA, ±10 V], Q2a [±0.12 kA, ±10 V] and Q3 [±2 kA, ±10 V] to account for possible transfer function difference between the quadrupoles. This paper presents the powering scheme of the four mentioned coupled circuits. A digital control strategy, using four standard LHC digital controllers, to decouple the four systems and to achieve a high precision control is proposed and discussed.
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THPPA3	Hybrid Multi Bend Achromat: from SuperB to EBS	lattice, emittance, dipole, synchrotron	3670
	P. Raimondi ESRF, Grenoble, France
	The Hybrid Multi Bend Achromat: from SuperB to EBS. The motivations and rationale at the basis of the Hybrid Multi Bend Achromat (HMBA) lattice and its evolution through the years are presented. Its implementation in the ESRF Extremely Brilliant Source (EBS) upgrade is also shown.
	Slides THPPA3 [24.610 MB]
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THPAB042	Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016	simulation, operation, emittance, closed-orbit	3799
	A.A. Gorzawski, K. Fuchsberger, M. Hostettler, T. Pieloni, J. Wenninger CERN, Geneva, Switzerland
	To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed.
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THPAB056	Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC	simulation, emittance, dynamic-aperture, coupling	3840
	M.P. Crouch, R.B. Appleby UMAN, Manchester, United Kingdom J. Barranco García, T. Pieloni, C. Tambasco EPFL, Lausanne, Switzerland X. Buffat, M. Giovannozzi, E.H. Maclean CERN, Geneva, Switzerland B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β^* and therefore the luminosity reach for the collider. These effects can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β^* the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.
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THPVA113	Inverse Problem-Based Magnetic Characterization of Weekly Magnetic Alloys	dipole, background, radiation, collider	4722
	A. Parrella, M.P. Ramos IT, Lisboa, Portugal P. Arpaia, A. Liccardo Naples University Federico II, Science and Technology Pole, Napoli, Italy M.C.L. Buzio CERN, Geneva, Switzerland
	Understanding the magnetic properties of materials used in accelerator components is becoming more and more important. For example, in the upcoming LHC upgrade at CERN, the increasing luminosity will boost the radiation dose received by the accelerator magnet's coil and consequently decrease its lifespan. Hence, a radiation shield with relative permeability less than 1.005 is required. The goal of this research is to design and validate a new method for characterizing weekly magnetic materials, suitable to be used in quality control of series production. The proposed method is based on inverse analysis approach coupled with a finite-element model. A material with unknown permeability is inserted in the air gap of a dipole magnet and the consequent perturbations of the dipole background flux density are measured. The magnetic permeability is then identified through gray-box inverse modelling, based on a finite-element approach. The results have been used to predict the magnetic impact of the radiation shield and develop further research on this subject.
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MOYAA1

Approaching the Nominal Performance at the LHC

operation, emittance, experiment, injection

13

J. Wenninger
CERN, Geneva, Switzerland

In 2015 the Large Hadron Collider (LHC) restarted for Run 2 after an almost two year long shutdown to consolidate the machine for operation at nominal beam energy. Following a month of recommissioning and training of the magnet system, the LHC operated for the first time at an energy of 6.5 TeV. The aim of this first year was to master operation at the higher energy and with beams of 25 ns spacing. In 2016 the performance could be pushed based on the experience of 2015, culminating with a luminosity 40% above the design value of 10³⁴ cm^-2s⁻¹. The status of the machine operation, performance and prospects for the rest of Run 2 and Run 3 will be discussed.

Slides MOYAA1 [4.639 MB]

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MOPAB004

Improved Protection of the Warm Magnets of the LHC Betatron Cleaning Insertion

shielding, radiation, operation, collimation

72

C. Bahamonde Castro, F. Cerutti, P. Fessia, A. Lechner, A. Mereghetti, D. Mirarchi, S. Redaelli, E. Skordis
CERN, Geneva, Switzerland
E. Skordis
The University of Liverpool, Liverpool, United Kingdom

After the High Luminosity (HL) upgrade in 2024-2026, the LHC is anticipated to increase its integrated luminosity by a factor of 10 beyond its original design value of 300 fb-1. In preparation for this, several improvements to the equipment will already be implemented during the next Long Shutdown (LS2) starting in 2019. In the betatron cleaning insertion, the debris leaking out of several collimators will deposit energy in the downstream warm magnets, causing long-term radiation damage. A new layout has been proposed in which the most exposed magnet of each assembly is removed, reducing the assembly from 6 to 5 magnet units and gaining 2 spare magnets. New absorbers are therefore required to enhance the shielding of the remaining magnet string. In this paper, we present an evaluation of the dose to the warm magnets for post-LS2 operation, and we quantify the achievable reduction of the long-term radiation damage for different absorber configurations. A solution for an improved magnet protection that fulfills the HL-LHC requirements is proposed.

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MOPAB027

Preparation of CVD Diamond Detector for fast Luminosity Monitoring of SuperKEKB

detector, simulation, monitoring, target

135

C.G. Pang, P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
LAL, Orsay, France

The SuperKEKB e⁺-e⁻ collider aims to reach a very high luminosity of 8×10 ³⁵ cm'2s'1, using highly focused ultra-low emittance bunches colliding every 4ns. To meet the requirement of the dithering feedback system used to stabilize the horizontal orbit at the IP (interaction point), a relative precision of 10 '3 in 1ms is specified for the fast luminosity monitoring, which can be in principle achieved thanks to the large cross section of the radiative Bhabha process. This paper firstly presents the fraction of detected Bhabha scattering positrons with a new beam pipe arrangement coupled with a Tungsten radiator to be installed in the Low Energy Ring; Then the characteristics of signals from a sCVD diamond detector with thickness of 140'm coupled with a broadband current amplifier were studied based on tests with a Sr-90 source; Finally, simulated results for the reconstructed luminosity and the relative precision with different assumed luminosities are also reported.

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MOPAB109

Operational Experience with Luminosity Scans for Beam Size Estimation in 2016 LHC Proton Physics Operation

emittance, operation, proton, simulation

374

M. Hostettler
LHEP, Bern, Switzerland
K. Fuchsberger, G. Papotti
CERN, Geneva, Switzerland

Luminosity scans were regularly performed at the CERN Large Hadron Collider (LHC) as of 2015 as a complementary method for measuring the beam size. The CMS experiment provides bunch-by-bunch luminosities at sufficient rates to allow evaluation of bunch-by-bunch beam sizes, and the scans are performed in the horizontal and vertical plane separately. Closed orbit differences between bunches can also be derived by this analysis. During 2016 LHC operation, these scans were also done in an automated manner on a regular basis, and the analysis was improved to significantly reduce the systematic uncertainty, especially in the crossing plane. This contribution first highlights the recent improvements to the analysis and elaborates on their impact. The measured beam sizes during 2016 proton physics operation are then shown and compared to measurements from synchrotron light telescopes and estimates based on the absolute luminosities of the LHC experiments.

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MOPAB110

Comparison of Transverse Emittance Measurements in the LHC

emittance, experiment, detector, operation

377

M. Hostettler, R. Alemany-Fernández, F. Alessio, M. Ferro-Luzzi, K. Fuchsberger, G. Iadarola, R. Matev, S. Papadopoulou, Y. Papaphilippou, G. Papotti, G. Trad
CERN, Geneva, Switzerland
F. Antoniou
The University of Liverpool, Liverpool, United Kingdom
G.R. Coombs
University of Glasgow, Glasgow, United Kingdom
T.B. Hadavizadeh
Oxford University, Physics Department, Oxford, Oxon, United Kingdom

Transverse emittance measurement in a collider is of crucial importance for understanding beam dynamics observations and evaluating the machine performance. Devices measuring the beam emittance face the challenge of dealing with considerable systematic errors that can compromise the quality of the measurement. Having different instruments or techniques that provide beam size estimations in order to compare the outcome and give an unbiased value of the emittance is very important in a collider. The comparison of the different results is as well very useful to identify possible problems in a given equipment which could remain unnoticed if such device is the only source of emittance reconstruction. In the LHC several of these instruments and techniques are available; wire scanners, synchrotron light monitors, emittance reconstruction from transverse convolved beam sizes extracted from luminosity scans at the LHC collision points and from beam-gas imaging in the vertex detector of the LHCb experiment. Those systems are briefly presented in this paper together with the comparison of the emittances reconstructed by each of them during physics production over the 2016 LHC run.

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MOPAB130

Cross-Calibration of the LHC Transverse Beam-Profile Monitors

emittance, optics, proton, experiment

437

R. Alemany-Fernández, F. Alessio, A. Alexopoulos, C. Barschel, F.S. Carlier, J.M. Coello de Portugal, M. Ferro-Luzzi, A. Garcia-Tabares, M. Hostettler, O. Karacheban, E.H. Maclean, R. Matev, T. Persson, P.K. Skowroński, R. Tomás, G. Trad, S. Vlachos, B. Würkner
CERN, Geneva, Switzerland
G.R. Coombs
EPFL, Lausanne, Switzerland
T.B. Hadavizadeh
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
M. Hofer
TU Vienna, Wien, Austria
L. van Riesen-Haupt
University of Oxford, Oxford, United Kingdom

Calibration of a transverse beam profile monitor is of fundamental importance to guarantee the best possible accuracy and reliability of the instrument over time. In LHC the calibration standard for transverse-profile measurements are the wire scanners. Other profile monitors such as beam synchrotron light telescopes and interferometers are calibrated with respect to them. Additional information about single-bunch sizes can be obtained from beam-gas imaging in the LHCb vertex detector, from the transverse convolved beam sizes extracted from luminosity scans at the collision points, and from the evolution of the luminous-region parameters as reconstructed by ATLAS and CMS inner tracker detectors during such scans. For the first time in LHC, a dedicated cross-calibration of all the above-mentioned systems was carried out with beam in 2016. Additionally, dedicated optics measurements were also performed in order to determine with the highest possible accuracy the amplitude function at the interaction points and at the position of the profile monitors. Results of these measurements are presented in this paper.

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MOPIK076

Optimization of Dynamic Aperture with Constraints on Linear Chromaticity

sextupole, coupling, simulation, lattice

705

H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.

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MOPIK077

Impact of Dynamical Stray Fields on CLIC

shielding, collimation, synchrotron, linear-collider

708

E. Marín, D. Schulte
CERN, Geneva, Switzerland
B. Heilig
MFGI, Budapest, Hungary
J. Pfingstner
University of Oslo, Oslo, Norway

In this paper we estimate the tolerances of stray-fields variations on the Compact Linear Collider (CLIC), discuss possible sources and propose several solutions. The Beam Delivery System (BDS) is the most sensitive system of CLIC to unwanted magnetic field variations, already variations of 1 nT would reduce the luminosity by 10% at wavelengths comparable to the BDS without considering any correction mechanism. Two sources of magnetic field variations are considered, natural and man-made. Precise magnetic field measurements at Earth's surface under a typical geomagnetic storm are presented. Additionally, stray field measurements have been conducted at CERN, to inspect B-field variations due to technical equipment in an accelerator environment. Different solutions are proposed to minimise the impact of stray fields on the CLIC performance.

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MOPIK099

Tuning-Based Design Optimization of CLIC Final Focus System at 3 TeV

sextupole, lattice, collider, linear-collider

760

F. Plassard, A. Latina, E. Marín, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
P. Bambade
LAL, Orsay, France

The tuning aims to mitigate static imperfections of the Final Focus System (FFS) for emittance preservation at the Interaction Point (IP). A simulation campaign on the nominal CLIC FFS at 3 TeV have shown the need of rethink the design in order to ease the tuning of the machine. The goal is to optimize the lattice in order to make the FFS more tolerant to misalignments by reducing the strength of the sextupoles. The tuning efficiency is promoted as figure of merit to find the optimal layout of the FFS. A comparative study of the tuning performances have been performed for two L* options.

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MOPIK100

Beam Delivery System Optimization for CLIC 380 GeV

sextupole, lattice, quadrupole, optics

764

F. Plassard, A. Latina, E. Marín, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
P. Bambade
LAL, Orsay, France

In the framework of the CLIC rebaselining, the Beam Delivery System (BDS) have been re-optimized for its initial stage at 380 GeV. Two BDS designs with L*=4.3 meters and L*=6 meters have been investigated. The optimization of the lattices and the beam parameters at the interaction point (IP) have been performed by taking into account their energy upgrade to 3 TeV and the tuning feasibility of the BDS in presence of static imperfections.

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MOPIK108

Tuning Simulations for the CLIC Traditional Beam Delivery System

simulation, lattice, collider, linear-collider

788

R.M. Bodenstein, P. Burrows
JAI, Oxford, United Kingdom
E. Marín, F. Plassard, R. Tomás
CERN, Geneva, Switzerland

As the design of the CLIC Beam Delivery System (BDS) evolves, tuning simulations must be performed on each of the proposed lattice designs to see which system achieves the highest luminosity in the most realistic manner. This work will focus on the tuning simulations performed on the so-called Traditional lattice design for the center-of-mass energy of 3 TeV. The lattice modifications required to target the most important aberrations and the latest tuning results will be presented.

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MOPVA023

Luminosity Increase in Laser-Compton Scattering by Crab Crossing Method

laser, electron, photon, scattering

902

Y. Koshiba, D. Igarashi, S. Ota, T. Takahashi, M. Washio
RISE, Tokyo, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
J. Urakawa
KEK, Ibaraki, Japan

In collider experiments such as KEKB, crab crossing method is a promising way to increase the luminosity. We are planning to apply crab crossing to laser-Compton scattering, which is a collision of electron beam and laser, to gain a higher luminosity leading to a higher flux X-ray source. It is well known that the collision angle between electron beam and laser affects the luminosity. It is the best when the collision angle is zero, head-on collision, to get a higher luminosity but difficult to construct such system especially when using an optical cavity for laser. Concerning this difficulty, we are planning crab crossing by tilting the electron beam using an rf-deflector. Although crab crossing in laser-Compton scattering has been already proposed*, nowhere has demonstrated yet. We are going to demonstrate and conduct experimental study at our compact accelerator system in Waseda University. In this conference, we will report about our compact accelerator system, laser system for laser-Compton scattering, and expected results of crab crossing laser-Compton scattering.
*Variola Alessandro, et al. Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators. Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.

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MOPVA102

Modeling the Low Level RF Response on the Beam during Crab Cavity Quench

cavity, simulation, SRF, klystron

1098

R. Apsimon, G. Burt, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.B. Appleby
UMAN, Manchester, United Kingdom
P. Baudrenghien, K.N. Sjobak
CERN, Geneva, Switzerland

The High Luminosity Upgrade for the LHC (HL-LHC) relies on crab cavities to compensate for the luminosity reduction due to the crossing angle of the colliding bunches at the interaction points. In this paper we present the simulation studies of cavity quenches and the impact on the beam. The cavity voltage and phase during the quench is determined from a simulation in Matlab and used to determine the impact on the beam from tracking simulations in SixTrack. The results of this study are important for determining the required machine protection and interlock systems for HL-LHC.

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MOPVA106

Experimental Studies of Asymmetric Dual Axis Cavity for Energy Recovery LINAC

cavity, electron, linac, radiation

1105

I.V. Konoplev, A.J. Lancaster, K. Metodiev, A. Seryi
JAI, Oxford, United Kingdom
R. Ainsworth
Fermilab, Batavia, Illinois, USA
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom

Funding: The Leverhulme Trust via International Network Grant (IN-2015-012).
Increasing the beam charge and repetition rate leads to appearance of beam break-up instabilities in conventional ERLs. At this stage the highest current, from the SRF ERL, is around 300mA. A single turn, dual axis, compact Asymmetric Energy Recovery LINAC (AERL) was proposed. The concept assumes the use of electron beams with energies up to 300 MeV and peak currents >1A, enabling the generation of high flux EUV/X-rays and THz radiation using conventional approaches. System allows beam to be transported through each stage i.e. the acceleration, interaction and deceleration only once partially removing the feedback thus increasing the instability start current. This further improved by tuning the individual cells allowing only operating mode to be uniform inside the cavity. We present the studies of 7 cells, aluminium alloy prototype of the cavity and discuss the experimental results. We show that HOMs excited on the different axis have different R/Q factors and show the field structures of operating mode and HOMs. The experimental results observed are in good agreement with theoretical predictions and the full scale copper prototype is demonstrated.

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MOPVA135

Fabrication, Processing and RF Test of RF-Dipole Prototype Crabbing Cavity for LHC High Luminosity Upgrade

cavity, dipole, HOM, cryogenics

1174

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

The superconducting rf-dipole crabbing cavity is one of two crabbing cavity designs proposed for the LHC high luminosity upgrade. The proof-of-principle rf-dipole cavity operating at 400 MHz has demonstrated excellent performance exceeding the design specifications. The prototype cavity for SPS beam test has been designed to include the fundamental power coupler, HOM couplers, and all the ancillary components intended to meet the design requirements. A crabbing cavity system is expected to be installed in the SPS beam line and tested prior to the installation in LHC; this will be the first crabbing cavity operation on a proton beam. The fabrication of two prototype rf-dipole cavities is currently being completed at Jefferson Lab. This paper presents the details on cavity processing and cryogenic test results of the rf-dipole cavities.

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TUPAB016

The CLIC Main Linac Module Updated Design

alignment, linac, klystron, operation

1345

C. Rossi, M. Aicheler, N. Catalán Lasheras, R. Corsini, S. Döbert, A. Grudiev, A. Latina, H. Mainaud Durand, M. Modena, H. Schmickler, D. Schulte, S. Stapnes, I. Syratchev, A.L. Vamvakas, W. Wuensch
CERN, Geneva, Switzerland
M. Aicheler
HIP, University of Helsinki, Finland

In 2016, CLIC implementation working groups have started their reflection on how to finalize the CLIC design work in the different areas of the project, aiming for a technical design and an overall implementation plan for CLIC being available for the next European Strategy Update around 2019. One of the working groups has focused its attention on the Main Linac hardware, which has brought together the different competences of the study with the aim of producing an advanced set of specifications for the design, installation and operation of the CLIC module. As the fundamental unit for the construction of the Main Beam linac, the CLIC module needs to move from the existing prototypes exploring its performance into an advanced and functional unit where the full life cycle of the module is considered. The progress of the working group activity is summarized in this paper, with considerations on the requirements for the design of the next-phase CLIC module.

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TUPAB060

Development of the Laser System for the Proof-of-Principle Experiment of Crab Crossing Laser-Compton Scattering

laser, scattering, electron, experiment

1460

T. Takahashi, D. Igarashi, Y. Koshiba, S. Ota, M. Washio
RISE, Tokyo, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
J. Urakawa
KEK, Ibaraki, Japan

An X-ray source via laser-Compton scattering has the advantage of small source, energy tunability and quasi-monochromaticity and is expected to be applied in a wide range of fields such as the industry and medical care. In laser-Compton scattering, the luminosity, which represents the collision frequency between the electrons and the photons, is very important. Increasing the luminosity is strongly required for increasing the scattered photon flux. One way to increase the luminosity is tilting electron bunches at the collision point, which is called crab crossing. It is the way to create the head-on collision artificially. The purpose of this study is the proof-of-principle of the crab crossing laser-Compton scattering. In this conference, we will report the design optimization and construction of the laser system for the collision and future prospects.
Variola Alessandro, et al. Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators. Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.

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TUPIK037

Proton Cross-Talk and Losses in the Dispersion Suppressor Regions at the FCC-hh

proton, simulation, collimation, quadrupole

1763

H. Rafique, R.B. Appleby
UMAN, Manchester, United Kingdom
J.L. Abelleira
JAI, Oxford, United Kingdom
A.M. Krainer, A. Langner
CERN, Geneva, Switzerland

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305
Protons that collide at the interaction points of the FCC-hh may contribute to the background in the subsequent detector. Due to the high luminosity of the proton beams this may be of concern. Using DPMJET-III to model 50 TeV proton-proton collisions, tracking studies have been performed with PTC and MERLIN in order to gauge the elastic and inelastic proton cross-talk. High arc losses, particularly in the dispersion suppressor regions, have been revealed. These losses originate mainly from particles with a momentum deviation, either from interaction with a primary collimator in the betatron cleaning insertion, or from the proton-proton collisions. This issue can be mitigated by introducing additional collimators in the dispersion suppressor region. The specific design, lattice integration, and the effect of these collimators on cross-talk is assessed.

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TUPIK059

Recent Progress of Dithering System at SuperKEKB

feedback, background, optics, electronics

1827

Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, S. Nakamura, K. Ohmi, T. Oki, S. Uehara
KEK, Ibaraki, Japan
P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault
LAL, Orsay, France
A.S. Fisher
SLAC, Menlo Park, California, USA
U. Wienands
ANL, Argonne, Illinois, USA

Recent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described.

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TUPIK089

Studies on Luminous Region, Pile-up and Performance for HL-LHC Scenarios

operation, simulation, optics, detector

1908

L.E. Medina Medrano, G. Arduini, R. Tomás
CERN, Geneva, Switzerland
L.E. Medina Medrano
UGTO, Leon, Mexico

Funding: Research supported by the HL-LHC project and the Beam project (CONACYT, Mexico).
Studies on luminous region and pile-up density are of great interest for the experiments at the future High Luminosity LHC (HL-LHC) in order to optimize the detector performance. The evolution of these parameters at the two main interaction points of the HL-LHC along optimum physics fills is studied for the baseline and alternative operational scenarios with the latest set of parameters, including a refined description of the longitudinal bunch profile. Results are discussed in terms of a new figure-of-merit, the effective pile-up density.

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TUPIK111

IP Feedback Ground Motion Simulation Studies for the ILC

feedback, ground-motion, simulation, collider

1983

R.M. Bodenstein, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
J. Pfingstner
CERN, Geneva, Switzerland

The International Linear Collider (ILC), as described in its Technical Design Report (TDR), must maintain strict control of its electron and positron beams in order to achieve the desired luminosity at each of its proposed center-of-mass energies. Controlling the beam parameters requires a dynamic system, capable of adjusting to a myriad of perturbations and errors. One of the components used to control the beam is the Interaction Point (IP) feedback system, which is used to dynamically steer the beams back into collision within nanoseconds. This work will show the simulation of the IP Feedback system's compensation for ground motion model K at the ILC.

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TUPVA005

Impact of the Crossing Angle on Luminosity Asymmetries at the LHC in 2016 Proton Physics Operation

experiment, emittance, operation, proton

2035

M. Hostettler
LHEP, Bern, Switzerland
F. Antoniou, I. Efthymiopoulos, K. Fuchsberger, G. Iadarola, N. Karastathis, M. Lamont, Y. Papaphilippou, G. Papotti, J. Wenninger
CERN, Geneva, Switzerland

During 2016 proton physics operation at the CERN Large Hadron Collider (LHC), an asymmetry of up to 10% was observed between the luminosities measured by the ATLAS and CMS experiments. As the same bunch pairs collide in both experiments, a difference in luminosities must be of either geometric or instrumental origin. This paper quantifies the impact of the crossing angle on this asymmetry. As the beams cross in different planes in the two experiments, non-round beams are expected to yield an asymmetry due to the crossing angle. Results from crossing angle measurements at both experiments are also shown and the impact on the luminosities is evaluated.

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TUPVA006

Lessons Learnt from the 2016 LHC Run and Prospects for HL-LHC Availability

proton, target, radiation, operation

2039

A. Apollonio, O. Rey Orozko, R. Schmidt, M. Valette, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

The LHC exhibited unprecedented availability during the 2016 proton run, producing about 40 fb-1 of integrated luminosity, surpassing the sum of production during the 4 previous years. This was achieved while running steadily with a peak luminosity above the design target of 1034 cm- 2s⁻¹. Individual system performance and an increased experience operating the LHC were fundamental for these achievements, following the consolidations and improvements deployed during the Long Shutdown 1 and the Year End Technical Stop in 2015. The implications of this excellent performance in the context of the High Luminosity LHC are discussed in this paper, with the goal of defining the possible integrated luminosity reach of HL-LHC when considering the different operating conditions and the newly developed systems and technologies.

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TUPVA007

Impact of LHC and SPS Injection Kicker Rise Times on Lhc Filling Schemes and Luminosity Reach

injection, kicker, emittance, timing

2043

W. Bartmann, M.J. Barnes, J. Boyd, E. Carlier, A. Chmielinska, B. Goddard, G. Kotzian, C. Schwick, L.S. Stoel, D. Valuch, F.M. Velotti, V. Vlachodimitropoulos, C. Wiesner
CERN, Geneva, Switzerland

The 2016 LHC proton filling schemes generally used a spacing between injections of batches of bunches into SPS and LHC corresponding to the design report specification for the SPS and LHC injection kicker rise times, respectively. A reduction of the batch spacing can be directly used to increase luminosity without detrimental effects on beam stability, and with no increase in the number of events per crossing seen by the experiments. Measurements and simulations were performed in SPS and LHC to understand if a shorter injection kicker rise time and associated tighter batch spacing would lead to increased injection oscillations of the first and last bunches of a bunch train and eventually also a systematic growth of the transverse emittance. The results were used to define the minimum possible batch spacing for an acceptable emittance growth in LHC, with gains of reductions of about 10% possible in both machines. The results are discussed, including the potential improvement of the LHC luminosity for different filling schemes.

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TUPVA009

Multiparametric Response of the LHC Dynamic Aperture in Presence of Beam-Beam Effects

emittance, simulation, optics, octupole

2051

D. Pellegrini, F. Antoniou, S.D. Fartoukh, G. Iadarola, Y. Papaphilippou
CERN, Geneva, Switzerland

We performed extended simulations of LHC dynamic aperture (DA) in the presence of beam-beam effects in the weak-strong approximation, evaluating the contributions of parameters such as: tunes, optics, bunch intensity, crossing angle, emittance, chromaticity and current in the Landau octupoles. Here we present a summary of these studies, giving an overview of the amplitude of the LHC operational space and pointing out the remaining margins for mitigation of instabilities. These studies supported the actions deployed during the 2016 run of the LHC, which aimed at maximising its performances. Examples of such actions are the switch to lower emittance beams, the reduction of crossing angle and tune trims. More recently, DA scans have been used to help the definition of the operational scenarios for the 2017 run. Additional room for improvements, for instance by deploying crossing angle levelling, will be explained.

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TUPVA010

Multiparametric Response of the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects

octupole, simulation, beam-beam-effects, emittance

2055

D. Pellegrini, S.D. Fartoukh, N. Karastathis, Y. Papaphilippou
CERN, Geneva, Switzerland

We performed extended simulations of HL-LHC dynamic aperture in the presence of beam-beam effects in the weak- strong approximation, evaluating the contributions of param- eters such as: bunch intensity, crossing angle, chromaticity, current in the Landau octupoles and multipole errors. From the beam dynamics point of view, the main differ- ence between the LHC (until 2017) and the HL-LHC is the deployment of the achromatic telescopic squeezing (ATS) optics, allowing not only for a smaller '' reach, but also modifying the phase advances between the lattice correctors (sextupoles, octupoles) and the main IPs, and increasing the peak ' functions in the arcs. These correctors become therefore more efficient for the chromatic correction, but also a mitigation of the beam-beam long range interactions using the Landau octupoles is enabled, resulting in a possible reduction of the normalised crossing angle. The limits have been investigated in a tracking simulation campaign aimed at exploring the operational space for the HL-LHC and two possible options for luminosity levelling.

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TUPVA013

Lifetime of Asymmetric Colliding Beams in the LHC

simulation, proton, coupling, ion

2067

J.M. Jowett, R. Alemany-Fernández, M.A. Jebramcik, T. Mertens, M. Schaumann
CERN, Geneva, Switzerland

In the 2013 proton-nucleus (p-Pb) run of the LHC, the lifetime of the lead beam was significantly shorter than could be accounted for by luminosity burn-off. These effects were observed at a lower level in 2016 and studied in more detail. The beams were not only asymmetric but the differences in the bunch filling schemes between protons and Pb nuclei led to a wide variety of beam-beam interaction sequences in the bunch trains. The colliding bunches were also of different sizes. We present an analysis of the data and an interpretation in terms of theoretical models.

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TUPVA014

The 2016 Proton-Nucleus Run of the LHC

proton, experiment, operation, ion

2071

J.M. Jowett, R. Alemany-Fernández, G. Baud, P. Baudrenghien, R. De Maria, R. De Maria, D. Jacquet, M.A. Jebramcik, A. Mereghetti, T. Mertens, M. Schaumann, H. Timko, M. Wendt, J. Wenninger
CERN, Geneva, Switzerland

For five of the LHC experiments the second p-Pb collision run planned in 2016 offered the opportunity to answer a range of important physics questions arising from the surprise discoveries (e.g., flow-like collective phenomena in small systems) made in earlier Pb-Pb, p-Pb and p-p runs. However the diversity of the physics and their respective capabilities led them to request very different operating conditions, in terms of collision energy, luminosity and pile-up. These appeared mutually incompatible within the available one month of operation. Nevertheless, a plan to satisfy most requirements was developed and implemented successfully. It exploited different beam lifetimes at two beam energies of 4 Z TeV and 6.5 Z TeV, a variety of luminosity sharing and bunch filling schemes, and varying beam directions. The outcome of this very complex strategy for repeated re-commissioning and operation of the LHC included the longest ever LHC fill with luminosity levelled for almost 38 h. The peak luminosity achieved exceeded the design value by a factor 7.8 and integrated luminosity substantially exceeded the experiments' requests.

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TUPVA015

Radiation Levels at the LHC: 2012, 2015 and 2016 Proton Physics Operations in View of HL-LHC requirements

radiation, operation, proton, insertion

2075

C. Martinella, M. Brugger, S. Danzeca, R. Garcia Alia, Y. Kadi, O. Stein, C. Xu
CERN, Geneva, Switzerland

The variety of beam losses produced in the Large Hadron Collider (LHC) creates a mixed and complex radiation field. During 2012, 2015 and 2016, Beam Loss Monitors and RadMons were used to monitor the inte-grated dose and the High Energy Hadrons fluence in order to anticipate the electronics degradation and inves-tigate the cause of failures. The annual radiation levels are compared; highlighting the mechanisms in the pro-duction of beam losses and the impact of the different squeeze and crossing angle. In addition, the increase of beam-gas interaction is discussed comparing operations at 25 ns and 50 ns bunch spacing. A strategy is presented to allow for a continuous respective evaluation during the upcoming LHC and future High Luminosity LHC (HL-LHC) operations.

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TUPVA016

Identification and Analysis of Prompt Dose Maxima in the Insertion Regions IR1 and IR5 of the Large Hadron Collider

radiation, operation, dipole, quadrupole

2078

O. Stein, M. Brugger, S. Danzeca, R. Garcia Alia, Y. Kadi, M. Kastriotou, C. Martinella, C. Xu
CERN, Geneva, Switzerland

During the operation of the LHC the continuous particle losses create a radiation field in the LHC tunnel and the adjacent caverns. Exposed electronics and accelerator components show dose dependent accelerated aging effects and stochastic Single Event Effects which can lead to faults and downtime of the LHC. In order to achieve an optimal life duration, the position of the equipment is chosen in dependency of the amplitude of the radiation fields. Therefore, it is crucial to monitor the prompt dose distributions along the whole LHC. By using the LHC beam loss monitor and RadMon systems, the prompt dose during the accelerator operation is continuously monitored. Measurements in the long straight sections and the dispersion suppressors in IR1 (ATLAS) and in IR5 (CMS) have shown that the radiation levels have localised maxima which exceed the base line by 1 to 2 orders of magnitude. The analysis of these radiation peaks will be presented and the underlying loss mechanisms will be discussed. The results will help to identify areas not suitable for radiation sensitive electronics. Implications on the expected radiation levels for High-Luminosity LHC are also discussed.

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TUPVA020

The LHC Injectors Upgrade (LIU) Project at CERN: Ion Injector Chain

ion, injection, extraction, kicker

2089

H. Bartosik, S.C.P. Albright, M.E. Angoletta, G. Bellodi, N. Biancacci, T. Bohl, J. Coupard, H. Damerau, A. Funken, B. Goddard, S. Hancock, K. Hanke, A. Huschauer, J.M. Jowett, V. Kain, D. Küchler, D. Manglunki, M. Meddahi, G. Rumolo, R. Scrivens, E.N. Shaposhnikova, V. Toivanen, F.J.C. Wenander
CERN, Geneva, Switzerland

The LHC injector chain for Pb-ion beams at CERN consists of Linac3, the accumulator ring LEIR, the PS and the SPS. In the context of the LHC injectors upgrade (LIU) project an intense program of machine development studies has been performed in the last two years to maximise the intensity of Pb-ion beams at LHC injection. In this paper we present an analysis of the operational performance achieved so far, with the goal of 1) identifying the remaining performance bottlenecks along the chain and possible areas for improvement, and 2) to optimize the Pb-ion beam production scheme for the High Luminosity (HL-) LHC era. A consistent set of beam parameters for the HL-LHC era has been established taking into account the already achieved improvements as well as foreseen upgrades still to be implemented, such as slip stacking in the SPS.

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TUPVA021

Impact of Collision Debris in the HL-LHC ATLAS and CMS Insertions

proton, optics, insertion, radiation

2093

A. Tsinganis, F. Cerutti
CERN, Geneva, Switzerland

The High Luminosity upgrade of the LHC (HL-LHC) foresees the baseline operation of the accelerator at a 5 times higher peak luminosity (5.0x1034cm^-2s⁻¹). The impact of collision debris on the magnets and other equipment in the triplet region and matching section of the ATLAS and CMS insertions has been evaluated by means of detailed FLUKA models implementing the latest optics and layout version. Qualitative and quantitative differences between the vertical and horizontal beam crossing schemes are highlighted. With measures in place to mitigate the effects of the interruption of the beam screen in the triplet interconnections and the Q4 aperture reduction, peak dose values in the superconducting coils remain below 30MGy in the triplet-D1 and below 12MGy in the matching section magnets for an integrated luminosity of 3000fb-1. Peak power density values are lower than 3mW/cm³ and 1mW/cm³ in the triplet and matching section respectively. Total heat loads in magnets, collimators, masks and absorbers were also estimated, along with dose and particle fluence maps relevant for Radiation to Electronics (R2E) aspects. The effect of a displacement of the interaction point is also addressed.

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TUPVA022

Requirements for Crab Cavity System Availability in HL-LHC

cavity, optics, operation, proton

2097

M. Valette, A. Apollonio, J.A. Uythoven, D. Wollmann
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
Crab Cavities will be installed in the High Luminosity LHC in order to increase the effective peak luminosity through a partial compensation of the geometric factor. This will allow extending the levelling time resulting in an increased production of integrated luminosity. Based on the availability of the LHC during 2016 operation, the expected yearly-integrated luminosity of the future HL-LHC was estimated using a Monte Carlo model. Crab cavity faults were added to the observed failure distribu-tions and their impact on integrated luminosity produc-tion as a function of fault time and fault frequency was studied. This allows identifying a breakeven point in luminosity production and defining minimum system availability requirements for the crab cavities to reach the design goal of 250 fb-1 of integrated luminosity per year.

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TUPVA025

Observations of Beam Losses at the LHC During Reduction of Crossing Angle

experiment, beam-losses, proton, beam-beam-effects

2105

B. Salvachua, X. Buffat, A.A. Gorzawski, T. Pieloni, S. Redaelli, C. Tambasco, J. Wenninger
CERN, Geneva, Switzerland
J. Barranco García, A.A. Gorzawski
EPFL, Lausanne, Switzerland
M.P. Crouch
UMAN, Manchester, United Kingdom

Several machine development studies have been performed in 2016 at the LHC in order to evaluate the effects of reducing the crossing angles in favor of defining the maximum achievable luminosity in the ATLAS and CMS experiments. At the end of the LHC proton-proton run at 6.5TeV the reduction of the crossing angle from 185urad to 140urad was operationally implemented. The observation of beam losses and lifetimes during this process are analysed and discussed.

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TUPVA026

Beam-Beam Studies for FCC-hh

optics, simulation, dynamic-aperture, resonance

2109

J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland
X. Buffat, S.V. Furuseth, C. Tambasco
CERN, Geneva, Switzerland
S.V. Furuseth
NTNU, Trondheim, Norway

Funding: This works was performed in the framework of the European Circular 'Energy Fr'ontier Collider Study, H2020 Framework Programme under grant agreement no. 654305. We acknowledge support from the Swiss State Secretariat for Education, Research and Innovation SERI.
The Future Circular Collider hadron-hadron (FCC-hh) design study is currently exploring different IR design possibilities including round and flat optics or different crossing schemes. The present study intends to evaluate each scenario from the beam-beam effects point of view. In particular the single particle long term stability to maximize beam lifetimes and luminosity reach is used to quantify the differences. The impact of strong head on interactions on the beam quality and lifetime is addressed by means of GPU accelerated simulations code featuring a weak-strong 6-dimensional beam-beam interaction.

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TUPVA032

Beam-Gas Background Observations at LHC

background, experiment, detector, simulation

2129

S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
R. Alemany-Fernández, F. Alessio, G. Bregliozzi, H. Burkhardt, G. Corti, A. Di Mauro, M. Guthoff, A. Manousos, K.N. Sjobak, C. Yin Vallgren
CERN, Geneva, Switzerland
A. Alici
Bologna University, Bologna, Italy
S. D'Auria
University of Glasgow, Glasgow, United Kingdom
S.M. Gibson
JAI, Egham, Surrey, United Kingdom
D. Lazic
BUphy, Boston, Massachusetts, USA

Observations of beam-induced background at LHC during 2015 and 2016 are presented in this paper. The four LHC experiments use the non-colliding bunches present in the physics-filling pattern of the accelerator to trigger on beam-gas interactions. During luminosity production the LHC experiments record the beam-gas interactions using dedicated background monitors. These data are sent to the LHC control system and are used to monitor the background levels at the experiments during accelerator operation. This is a very important measurement, since poor beam-induced background conditions can seriously affect the performance of the detectors. A summary of the evolution of the background levels during 2015 and 2016 is given in these proceedings.

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TUPVA034

SPS Studies in Preparation for the Crab Cavity Experiment

emittance, experiment, cavity, simulation

2133

A. Alekou, A. Alekou, F. Antoniou, F. Antoniou, G. Arduini, G. Arduini, H. Bartosik, H. Bartosik, R. Calaga, R. Calaga, Y. Papaphilippou, Y. Papaphilippou, Y. Papaphilippou
CERN, Geneva, Switzerland
A. Alekou, R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

A local Crab Cavity (CC) scheme will recover head-on collisions at the Interaction Points (IPs) of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The first time that CC will ever be tested with proton beams will be in 2018 in the SPS machine. The available dedicated Machine Development (MD) time after the installation of the cavities will be limited and therefore good preparation is essential in order to ensure that the MDs are as efficient as possible. This paper presents the simulations and experimental studies performed in preparation for the future MDs and discusses the next steps.

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TUPVA037

FCC-hh Final-Focus for Flat-Beams: Parameters and Energy Deposition Studies

optics, collider, quadrupole, hadron

2139

J.L. Abelleira, E. Cruz Alaniz, A. Seryi, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
M.I. Besana
CERN, Geneva, Switzerland

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol), EU's Horizon 2020 grant No 654305.
The international Future Circular Collider (FCC) study comprises the study of a new scientific structure in a tunnel of 100 km. This will allow the installation of two accelerators, a 45.6'175 GeV lepton collider and a 100-TeV hadron collider. An optimized design of a final-focus system for the hadron collider is presented here. The new design is more compact and enables unequal β^* in both planes, whose choice is justified here. This is followed by energy deposition studies, where the total dose in the magnets as a consequence of the collision debris is evaluated.

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TUPVA040

Overview of Design Development of FCC-hh Experimental Interaction Regions

optics, detector, dipole, experiment

2151

A. Seryi, J.L. Abelleira, E. Cruz Alaniz, L.J. Nevay, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
R.B. Appleby, H. Rafique
UMAN, Manchester, United Kingdom
R.B. Appleby
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J. Barranco García, T. Pieloni
EPFL, Lausanne, Switzerland
M. Benedikt, M.I. Besana, X. Buffat, H. Burkhardt, F. Cerutti, A. Langner, R. Martin, W. Riegler, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
M. Boscolo, F. Collamati
INFN/LNF, Frascati (Roma), Italy
M. Hofer
TU Vienna, Wien, Austria
L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom
L. van Riesen-Haupt
University of Oxford, Oxford, United Kingdom

The experimental interaction region is one of the key areas that define the performance of the Future Circular Collider. In this overview we will describe the status and the evolution of the design of EIR of FCC-hh, focusing on design of the optics, energy deposition in EIR elements, beam-beam effects and machine detector interface issues.

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TUPVA044

Modelling and Measurements of Bunch Profiles at the LHC

emittance, synchrotron, radiation, scattering

2167

S. Papadopoulou, F. Antoniou, T. Argyropoulos, M. Hostettler, Y. Papaphilippou
CERN, Geneva, Switzerland
M. Fitterer
Fermilab, Batavia, Illinois, USA

The bunch profiles in the LHC are often observed to be non-Gaussian, both at Flat Bottom (FB) and Flat Top (FT) energies. Especially at FT, an evolution of the tail population in time is observed. In this respect, the Monte-Carlo Software for IBS and Radiation effects (SIRE) is used to track different types of beam distributions. The impact of the distribution shape on the evolution of bunch characteristics is studied. The results are compared with observations from the LHC Run 2 data.

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TUPVA050

RHIC Polarized Proton Operation for 2017

resonance, lattice, polarization, injection

2188

V.H. Ranjbar, P. Adams, Z. Altinbas, E.C. Aschenauer, G. Atoian, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, M.R. Costanzo, T. D'Ottavio, K.A. Drees, P.S. Dyer, A.V. Fedotov, W. Fischer, C.J. Gardner, D.M. Gassner, X. Gu, C.E. Harper, M. Harvey, T. Hayes, J. Hock, H. Huang, R.L. Hulsart, J.P. Jamilkowski, T. Kanesue, N.A. Kling, J.S. Laster, C. Liu, Y. Luo, D. Maffei, M. Mapes, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, T.A. Miller, M.G. Minty, C. Montag, J. Morris, G. Narayan, C. Naylor, S. Nemesure, P. Oddo, M. Okamura, S. Perez, A.I. Pikin, A. Poblaguev, S. Polizzo, V. Ptitsyn, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, W.B. Schmidke, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, Z. Sorrell, D. Steski, S. Tepikian, R. Than, P. Thieberger, J.E. Tuozzolo, G. Wang, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, W. Zhang, B. van Kuik
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the US Department of Energy under contract number DE-SC0012704
The 2017 operation of the Relativistic Heavy Ion Collider (RHIC) involved the running of only a single experiment at STAR with PHENIX offline in the process of the upgrade to sPHENIX. For this run there were several notable changes to machine operations. These included, transverse polarization, luminosity leveling, a new approach to machine protection and the development of new store and ramped lattices. The new 255 GeV store lattice was designed to both accommodate the necessary phase advance between the e-lens and IP8 for testing and to maximize dynamic aperture. The new lattices on the ramp were designed to maximize polarization transmission during the three strong intrinsic spin resonances crossings. Finally we are also commissioning new 9 MHz RF cavities during this run.

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TUPVA130

CLIC Tuning Performance Under Realistic Error Conditions

collider, target, linear-collider, alignment

2403

E. Marín, A. Latina, F. Plassard, D. Schulte, R. Tomás
CERN, Geneva, Switzerland

In this paper we present the latest results regarding the tuning study of the baseline design of the CLIC Final Focus System. In previous studies, 90% of the machines reach 90% of the nominal luminosity, when considering beam position monitor errors and transverse misalignments of magnets for a single beam case. In the present study, roll misalignments and strength errors are also included for both e^- and e⁺ beamlines, making the study a more realistic one. First, second and third order knobs are implemented in the tuning procedure to target the most relevant beam size aberrations. In order to minimise the total number of luminosity measurements a simultaneous scan of various knobs has been developed to cope with the non-fully orthogonality of the knobs. The obtained results for single and double beam studies are presented.

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WEYA1

Crab Cavity Systems for Future Colliders

cavity, collider, electron, proton

2474

S. Verdú-Andrés, I. Ben-Zvi, Q. Wu
BNL, Upton, Long Island, New York, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
R. Calaga
CERN, Geneva, Switzerland

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy, by the US LARP program and by the HL-LHC project.
KEKB was the first facility to implement the crab crossing technique in 2007, for the interaction of electron and positron beams. The High Luminosity Large Hadron Collider (HL-LHC) project envisages the use of crab cavities for increasing and levelling the luminosity of proton-proton collisions in LHC. Crab cavities have also been proposed and studied for future colliders like CLIC, ILC and eRHIC. This contribution will focus on the near and far future of crab cavities for particle colliders.

Slides WEYA1 [6.571 MB]

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WEOAB2

Correction of Beta-Beating Due to Beam-Beam for the LHC and Its Impact on Dynamic Aperture

sextupole, optics, quadrupole, dynamic-aperture

2512

L.E. Medina Medrano, J. Barranco García, X. Buffat, Y. Papaphilippou, T. Pieloni, R. Tomás
CERN, Geneva, Switzerland
J. Barranco García, T. Pieloni
EPFL, Lausanne, Switzerland
L.E. Medina Medrano
UGTO, Leon, Mexico

Funding: This work is supported by the European Circular Energy-Frontier Collider Study, H2020 programme under grant agreement no. 654305, by the Swiss State Secretariat for Education, Research and Innovation SERI, and by the Beam project (CONACYT, Mexico).
Minimization of the beta-beating at the two main interaction points of the LHC arising from the head-on and long-range beam-beam interactions can be performed by adjusting the strength of quadrupole or sextupole correctors. This compensation scheme is applied to the current LHC optics where the results show a significant reduction of the peak and RMS beta-beating; and the impact on the dynamic aperture is computed. A proposal for a similar strategy to be adopted in the High Luminosity LHC is also discussed.

Slides WEOAB2 [6.292 MB]

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WEPIK004

Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design

detector, background, photon, interaction-region

2914

G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani
CERN, Geneva, Switzerland
N. Bacchetta
INFN- Sez. di Padova, Padova, Italy
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
M.K. Sullivan
SLAC, Menlo Park, California, USA

A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.

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WEPIK010

Commissioning Status of SuperKEKB Main Ring Magnet System

operation, power-supply, dipole, interaction-region

2933

M. Masuzawa, T. Adachi, K. Egawa, T. Kawamoto, S. Nakamura, Y. Ohsawa, T. Oki, R. Sugahara, R. Ueki
KEK, Ibaraki, Japan

SuperKEKB is an electron-positron collider, which aims for the very high peak luminosity of 8x10³⁵ cm^-2s^-1 , 40 times higher than that of KEKB. The SuperKEKB Main Ring (MR) system is very large, consisting of more than 1700 water-cooled normal-conducting magnets and about 900 air-cooled normal-conducting magnets. More than 400 magnets and power supplies were newly fabricated, tested and installed for SuperKEKB Phase I beam operation. The MR magnet system worked well, which contributed greatly to the smooth start-up of the MR. Commissioning status of the MR magnet system during SuperKEKB Phase I operation will be reported. Some problems resulting in beam abort will also be reported.

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WEPIK015

Optimized Monochromatization for Direct Higgs Production in Future Circular e⁺e⁻ Colliders

collider, emittance, radiation, electron

2950

F. Zimmermann
CERN, Geneva, Switzerland
M.A. Valdivia García
DCI-UG, León, Mexico

Funding: This work was supported in part by the European Commission under the HORIZON2020 Integrating Activity project ARIES, grant agreement 730871, and by the Mexican CONACyT ‘‘BEAM'' Programme.
Direct s-channel Higgs production in e⁺e⁻ collisions is of interest if the centre-of-mass energy spread can be reduced to be comparable to the width of the standard model Higgs boson. A monochromatization scheme could be employed in order to achieve the desired reduction, by introducing a non-zero horizontal dispersion of opposite sign for the two colliding beams at the interaction point. In high-energy high-luminosity circular colliders, beamstrahlung may increase the energy spread and bunch length. The horizontal emittance blow up due to beamstrahlung, a new effect not present in past monochromatization proposals, may degrade the performance, especially the luminosity. We study, for the FCC-ee at 62.5 GeV beam energy, how we can optimize the IP optics parameters (betax*, Dx*) along with the number of particles per bunch so as to obtain maximum luminosity at a desired target value of the collision energy spread.

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WEPIK016

CEPC-SppC Towards CDR

collider, booster, positron, detector

2954

J. Gao
IHEP, Beijing, People's Republic of China

Funding: supported by National Key Programme for S&T Research and Development (2016YFA0400400), National Natural Science Foundation of China (11575218, 11605211, 11605210, 11505198), Key Research Program of Frontier Sciences, CAS, (QYZDJ-SSW-SLH004) and CAS Center for Excellence in Particle Physics (CCEPP)
In this paper we will give an introduction to Circular Electron Positron Collider (CEPC). The scientific background, physics goal, the collider design requirements and the conceptual design principle of CEPC are described. On CEPC accelerator, the optimization of parameter designs for CEPC with different energies, machine lengthes, single ring and crab-waist collision partial double ring, advanced partial double partial ring and fully partial double ring options, etc. have been discussed systematically, and compared. CEPC accelerator baseline and alternative designs have been proposed based on the luminosity potential in relation with the design goals. The sub-systems of CEPC, such as collider main ring, booster, electron positron injector, etc. ave also been introduced. The detector and MDI design have been briefly mentioned. Finally, the optimization design of Super Proton-Proton Collider (SppC), its energy and luminosity potentials, in the same tunnel of CEPC are also discussed. The CEPC-SppC Progress Report (2015-2016) has been published.

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WEPIK017

100 km CEPC Parameters and Lattice Design

sextupole, collider, dynamic-aperture, optics

2958

D. Wang, T.J. Bian, X. Cui, J. Gao, H. Geng, Q. Qin, B. Sha, N. Wang, Y. Wang, C.H. Yu, J.Y. Zhai, C. Zhang, Y. Zhang
IHEP, Beijing, People's Republic of China
F. Su
Institute of High Energy Physics (IHEP), People's Republic of China

The 100km double ring configuration with shared su-perconducting RF system has been defined as baseline by the circular electron positron collider (CEPC) steering committee. Based on this new scheme, we will get higher luminosity for Higgs (+170%) keeping the beam power in preliminary conceptual design report (Pre-CDR) or to reduce the beam power (19 MW) while keeping same luminosity. CEPC will be compatible with W and Z ex-periment. The luminosity for Z is designed at the level of 1035 cm^-2s⁻¹. The requirement for the energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The optics of arc and final focus system (FFS) with crab sextupoles has been designed, and also some primary dynamic aperture (DA) results were introduced.

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WEPIK029

High Luminosity at VEPP-2000 Collider With New Injector

collider, detector, injection, positron

2989

P.Yu. Shatunov, O.V. Belikov, D.E. Berkaev, K. Gorchakov, A.S. Kasaev, A.N. Kirpotin, I. Koop, A.A. Krasnov, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, D.V. Rabusov, Yu. A. Rogovsky, A.M. Semenov, A.I. Senchenko, Y.M. Shatunov, D.B. Shwartz, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov
BINP SB RAS, Novosibirsk, Russia
E. Perevedentsev, Yu. A. Rogovsky, A.I. Senchenko, D.B. Shwartz
NSU, Novosibirsk, Russia

VEPP-2000 e⁺e⁻ collider at BINP was commissioned and started data taking with two detectors in 2010 with old injection chain. In the middle energy range, where the luminosity was limited by beam-beam effects, the world record values of beam-beam parameter were achieved, ksi=0.12/IP. At the same time the design luminosity value of L = 10³² cm^-2s⁻¹ at top energy (E = 1 GeV per beam) remained unreachable due to limited e⁺ production rate. The injection chain was significantly upgraded in 2013-2016. The experience of upgraded VEPP-2000 complex operation at top energies with Round Colliding Beams will be presented.

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WEPIK030

Experimental Validation of the Achromatic Telescopic Squeezing Scheme at the LHC

optics, collimation, insertion, injection

2992

S.D. Fartoukh, R. Bruce, F.S. Carlier, J.M. Coello de Portugal, A. Garcia-Tabares, E.H. Maclean, L. Malina, A. Mereghetti, D. Mirarchi, T. Persson, M. Pojer, L. Ponce, S. Redaelli, B. Salvachua, P.K. Skowroński, M. Solfaroli, R. Tomás, D. Valuch, A. Wegscheider, J. Wenninger
CERN, Geneva, Switzerland

The Achromatic Telescopic Squeezing (ATS) [1] scheme offers new techniques to deliver unprecedentedly small beam spot size at the interaction points of the ATLAS and CMS experiments of the LHC, while perfectly controlling the chromatic properties of the corresponding optics (linear and non-linear chromaticities, off-momentum beta-beating, spurious dispersion induced by the crossing bumps). The first series of beam tests with ATS optics were achieved during the LHC Run I (2011/2012) for a first validation of the basics of the scheme at small intensity. In 2016, a new generation of more performing ATS optics was developed and more extensively tested in the machine, still with probe beams for optics measurement and correction at β^*=10 cm, but also with a few nominal bunches to establish first collisions at nominal β^* (40 cm) and beyond (33 cm), and to analysis the robustness of these optics in terms of collimation and machine protection. The paper will highlight the most relevant and conclusive results which were obtained during this second series of ATS tests.
[1] S. Fartoukh , Phys. Rev. ST Accel. Beams 16, 111002

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WEPIK043

Modeling Local Crabbing Dynamics in the JLEIC Ion Collider Ring

ion, lattice, cavity, emittance

3022

S.I. Sosa Guitron, J.R. Delayen
ODU, Norfolk, Virginia, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

The Jefferson Lab Electron-Ion Collider (JLEIC) design considers a 50 mrad crossing angle at the Interaction Point. Without appropriate compensation, this could geometrically reduce the luminosity by an order of magnitude. A local crabbing scheme is implemented to avoid the luminosity loss: crab cavities are placed at both sides of the interaction region to restore a head-on collision scenario. In this contribution, we report on the implementation of a local crabbing scheme in the JLEIC ion ring. The effects of this correction scheme on the stability of proton bunches are analyzed using the particle tracking software elegant.

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WEPIK047

Frequency Choice Studies of eRHIC Crab Cavity

cavity, ion, electron, simulation

3028

Y. Hao, Y. Luo, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). Since the ion beam is long when cooling is not present, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence a impact to the luminosity lifetime. In this paper, we present the initial result of the weak-strong and strong-strong beam-beam tracking with the crab crossing scheme. The result provides beam dynamics guidance in choosing the proper frequency the crab cavity for the future EIC.

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WEPIK049

Overview of the eRHIC Ring-Ring Design

electron, proton, storage-ring, polarization

3035

C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, J.M. Brennan, A.V. Fedotov, W. Fischer, W. Guo, Y. Hao, A. Hershcovitch, Y. Luo, F. Méot, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, S. Seletskiy, T.V. Shaftan, V.V. Smaluk, S. Tepikian, D. Trbojevic, E. Wang, F.J. Willeke, H. Witte, Q. Wu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The ring-ring electron-ion collider eRHIC aims at an electron-ion luminosity in the range from 10³² to 10³³cm^-2sec^-1 over a center-of-mass energy range from 20 to 140GeV. To minimize the technical risk the design is based on existing technologies and beam parameters that have already been achieved routinely in hadron-hadron collisions at RHIC, and in electron-positron collisions elsewhere. This design has evolved considerably over the last two years, and a high level of maturity has been achieved. We will present the latest design status and give an overview of studies towards evaluating the feasibility.

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WEPIK050

Parameters for eRHIC

electron, proton, emittance, synchrotron

3038

R.B. Palmer, C. Montag
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Requirements for the proposed BNL eRHIC Ring-Ring Electron Ion Collider (EIC) are discussed, together with the dependence of luminosity with the beam divergence and forward proton acceptance. Parameters are given for four cases. The first two use no cooling and could represent a first phase of operation. The next two use strong cooling and increased beam currents. In each case parameters are given that 1) meets the requirement for forward proton acceptance, and 2) has somewhat higher divergences giving somewhat higher luminosity.

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WEPVA071

Preliminary Conceptual Study of Next Generation Tau-Charm Factory at China

factory, collider, positron, electron

3436

Q. Luo
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China 11375178 and the Fundamental Research Funds for the Central Universities, Grant No WK2310000046
As BEPC II would accomplish its mission in the next decade, research on high energy science demands a successor. The luminosity of this successor should be one or two orders higher than BEPC II, while the electron beam should be longitudinal polarized at the IP. This paper discusses the feasibility and key technologies of the next tau-charm collider: a greenfield new facility or an upgrade of BEPC II.

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WEPVA111

Change of Critical Current Density in Nb-Ti and Nb3Sn Strands After Millisecond Heating

superconducting-magnet, experiment, dipole, collider

3528

V. Raginel, K. Kulesz, M. Mentink, R. Schmidt, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland
D. Kleiven
NTNU, Trondheim, Norway

The damage mechanisms and limits of superconducting magnet components due to direct beam impact are not well understood. The energy deposition from beam losses can cause significant temperature rise and mechanical stress in the magnet coils, which can lead to a degradation of the insulation strength and critical current of the superconductor. An improved understanding of these mechanisms is not only important for the LHC in view of the planned increase in beam brightness, but also for other high energy accelerators using superconducting magnets. An experimental road map has been defined to study these damage mechanisms. Experiments have been performed with Nb-Ti and Nb3Sn strands and cable stacks at room temperature. This contribution focuses on the experimental study on the effect of millisecond heating on superconducting strands.

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WEPVA112

Characterisation of the Mechanical Behaviour of Superconducting Cables Used in High Field Magnets From Room Temperature Down to 77K

dipole, collider, cryogenics, superconducting-magnet

3532

O. Sacristan De Frutos, M. Daly, P. Ferracin, C. Fichera, M. Guinchard, T. Mikkola, F. Savary, G. Vallone
CERN, Geneva, Switzerland

A comprehensive knowledge of the mechanical properties of the superconducting cable used in high-field magnets is of paramount importance to study and model the behaviour of the magnet coil from assembly to the operational conditions at cryogenic temperature. The mechanical characterisation of such kind of materials presents practical challenges associated with the heterogeneity of the materials, the geometry, size and quality of the samples that can be produced out of actual cables. These constraints impose the undertaking of such measurements from a nonstandard approach, and hence the development of tailor-made tooling. An extensive characterisation campaign for the determination of the mechanical properties of the superconducting cable at room and cryogenic temperature was launched at CERN in order to determine the most relevant mechanical properties of the superconducting cables used in the MQXF and 11T magnets. This paper describes the design of the tooling developed for this specific application as well as the experimental set-up used for the tests, and discusses the outcomes of the matrix of tests performed.

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WEPVA113

Thermo-Physical and Mechanical Characterisation of Novel Materials under Development for HL-LHC Beam Intercepting Devices

radiation, experiment, laser, framework

3536

O. Sacristan De Frutos, A. Bertarelli, L. Bianchi, F. Carra, J. Guardia, M. Guinchard, S. Redaelli
CERN, Geneva, Switzerland

Funding: The research leading to these results has received funding from the European Commission under the FP7 Research Infrastructures project EuCARD-2, grant agreement no.312453
The collimation system for high energy particle accelerators as HL-LHC, must be designed to withstand the close interaction with intense and energetic particle beams, safely operating over an extended range of temperatures in extreme conditions (pressure, strain-rate, radiation), which are to become more demanding with the High Luminosity LHC. In order to withstand such conditions, the candidate materials must possess among other properties outstanding thermal shock resistance and high thermal and electrical conductivity, condition only met by advanced or novel materials. Therefore, an extensive R&D program has been launched to develop novel materials capable of replacing or complementing materials used for present collimators. So far, Molybdenum Carbide - Graphite and Copper-Diamond composites have been identified as the most promising materials. Literature data are scarce or non-existing for these materials. For this reason the successive characterisation campaigns constitute a linchpin of the R&D program. This paper reviews the experimental program followed for the thermo-physical and mechanical characterisation of the materials, and discusses the most relevant results.

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WEPVA116

HL-LHC Inner Triplet Powering and Control Strategy

controls, quadrupole, simulation, hadron

3544

S. Yammine, H. Thiesen
CERN, Geneva, Switzerland

In order to achieve the target 3000 fb-1 integrated field for the HL-LHC (High Luminosity ' Large Hadron Collider) at ATLAS and CMS, new large aperture quadrupoles are required for the final focusing triplet magnets before the interaction points. These low-' magnets, based on the Nb3Sn technology, deliver a peak field of 11.4 T. They consist of two outer quadrupoles, Q1 and Q3 and a central one divided into two identical magnets, Q2a and Q2b. To optimize the powering and the beam dynamics of these triplets, the quadrupoles will be powered in series by a single high-current two quadrants (2-Q) converter [18 kA, ±10 V]. Three 4-Q trim power converters are added over Q1 [±2 kA, ±10 V], Q2a [±0.12 kA, ±10 V] and Q3 [±2 kA, ±10 V] to account for possible transfer function difference between the quadrupoles. This paper presents the powering scheme of the four mentioned coupled circuits. A digital control strategy, using four standard LHC digital controllers, to decouple the four systems and to achieve a high precision control is proposed and discussed.

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THPPA3

Hybrid Multi Bend Achromat: from SuperB to EBS

lattice, emittance, dipole, synchrotron

3670

P. Raimondi
ESRF, Grenoble, France

The Hybrid Multi Bend Achromat: from SuperB to EBS. The motivations and rationale at the basis of the Hybrid Multi Bend Achromat (HMBA) lattice and its evolution through the years are presented. Its implementation in the ESRF Extremely Brilliant Source (EBS) upgrade is also shown.

Slides THPPA3 [24.610 MB]

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THPAB042

Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016

simulation, operation, emittance, closed-orbit

3799

A.A. Gorzawski, K. Fuchsberger, M. Hostettler, T. Pieloni, J. Wenninger
CERN, Geneva, Switzerland

To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed.

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THPAB056

Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC

simulation, emittance, dynamic-aperture, coupling

3840

M.P. Crouch, R.B. Appleby
UMAN, Manchester, United Kingdom
J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland
X. Buffat, M. Giovannozzi, E.H. Maclean
CERN, Geneva, Switzerland
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β^* and therefore the luminosity reach for the collider. These effects can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β^* the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.

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THPVA113

Inverse Problem-Based Magnetic Characterization of Weekly Magnetic Alloys

dipole, background, radiation, collider

4722

A. Parrella, M.P. Ramos
IT, Lisboa, Portugal
P. Arpaia, A. Liccardo
Naples University Federico II, Science and Technology Pole, Napoli, Italy
M.C.L. Buzio
CERN, Geneva, Switzerland

Understanding the magnetic properties of materials used in accelerator components is becoming more and more important. For example, in the upcoming LHC upgrade at CERN, the increasing luminosity will boost the radiation dose received by the accelerator magnet's coil and consequently decrease its lifespan. Hence, a radiation shield with relative permeability less than 1.005 is required. The goal of this research is to design and validate a new method for characterizing weekly magnetic materials, suitable to be used in quality control of series production. The proposed method is based on inverse analysis approach coupled with a finite-element model. A material with unknown permeability is inserted in the air gap of a dipole magnet and the consequent perturbations of the dipole background flux density are measured. The magnetic permeability is then identified through gray-box inverse modelling, based on a finite-element approach. The results have been used to predict the magnetic impact of the radiation shield and develop further research on this subject.

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