01 Circular and Linear Colliders
Paper Title Page
MOPMF010 Measurement and Simulation of Betatron Coupling Beam Transfer Function in RHIC 99

• Y. Luo, W. Fischer, A. Marusic, M.G. Minty
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.
Transfer function measurements are important for characterizing betatron tunes, betatron coupling, and beam spectrum in the routine operation of the Relativistic Heavy Ion Collider (RHIC). To counteract the linear betatron coupling, we developed a technique to continuously measure the betatron coupling coefficient with a base band phase lock loop tune meter in 2006. Based on this technique, we demonstrated and built a robust tune/coupling feedback in RHIC. In this article, we revisit the BTF measurement with betatron coupling to benchmark our BTF simulation code. We also compared the values of eigenmode projection ratios from BTF with those calculated with the single particle model.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF010
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MOPMF011 Beam-Beam Issues With Two Interaction Points in eRHIC 102

• Y. Luo, M. Blaskiewicz, A. He, C. Montag, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this article, we study the beam-beam interaction related issues with two interaction points in the current eRHIC ring-ring design. We carried out strong-strong beam-beam simulation in a 2-d bunch intensity scan. We observed coherent beam-beam instability and emittance blowup with 2 collisions per turn at lower bunch intensities than the case with only 1 collision per turn. To deliver collisions to the two experiments simultaneously, we proposed a new bunch filling pattern to avoid 2 collisions per turn for any electron or proton bunch. We proved that the parasitic beam-beam effect with the new bunch filling pattern is negligible.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF011
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MOPMF012 Study of Crabbed Collision in eRHIC With a Combination of Strong-Strong and Weak-Strong Simulations 105

• Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
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.
In the present design of the future electron-ion collider eRHIC at the Brookhaven National Laboratory, a crossing angle of 22~mrad between the electron and proton orbits at the interaction region is adopted. To compensate the geometric luminosity loss, a local compensation scheme with two sets of crab cavities for each beam is considered. In this article, we first carry out strong-strong beam-beam simulation to study possible coherent beam-beam instability. Under the assumption of no coherent beam-beam motion, we then carry out a weak-strong beam-beam simulation to determine the long-term stability of the proton beam with the equilibrium electron beam sizes extracted from the strong-strong beam-beam simulation.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF012
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MOPMF022 Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities 129

• E. Yamakawa, R. Apsimon, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
• P. Baudrenghien, R. Calaga, F.J. Galindo Guarch
CERN, Geneva, Switzerland

The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF022
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MOPMF023 Updates on the Optic Corrections of FCC-hh 133

• D. Boutin, A. Chancé, B. Dalena
CEA/IRFU, Gif-sur-Yvette, France
• B.J. Holzer, D. Schulte
CERN, Geneva, Switzerland

The FCC-hh (Future Hadron-Hadron Circular Collider) is one of the options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group, and the natural evolution of existing LHC. The evaluation of the various magnets mechanical error and field error tolerances in the arc sections of FCC-hh, as well as an estimation of the correctors strengths necessary to perform the error corrections, are important aspects of the collider design. In this study recommended values for the mechanical errors, dipole and quadrupole field errors tolerances are proposed, with the possible consequences on the correctors technological choice and on the beam screen design. Advanced correction schemes of the linear coupling (with skew quadrupoles) and of the beam tunes (with normal quadrupoles) are discussed. Also a combined correction scheme including the interaction regions is tested.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF023
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MOPMF024 Dipole Field Quality and Dynamic Aperture for FCC-hh 137

• B. Dalena
CEA/IRFU, Gif-sur-Yvette, France
• D. Boutin, A. Chancé
CEA/DRF/IRFU, Gif-sur-Yvette, France
• B.J. Holzer, S. Izquierdo Bermudez, D. Schoerling, D. Schulte
CERN, Geneva, Switzerland

Funding: This Research and Innovation Action project submitted to call H2020-INFRADEV-1-2014-1 receives funding from the European Union's H2020 Framework Program under grant agreement No. 654305.
The Nb3Sn dipole design for the hadron machine option of the Future Circular Colliders enters in an intense and long R&D phase. As a result, more realistic dipole field quality evaluations are available for beam dynamics studies. The paper discusses the impact of the main dipole field quality on the first and second order design of the hadron machine and on its dynamic aperture.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF024
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MOPMF025 Overview of Arc Optics of FCC-hh 141

• A. Chancé, B. Dalena
CEA/IRFU, Gif-sur-Yvette, France
• D. Boutin
CEA/DRF/IRFU, Gif-sur-Yvette, France
• B.J. Holzer, D. Schulte
CERN, Geneva, Switzerland

Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol) project has received funding from the European Union's Horizon 2020 research and innovation programme under grant No 654305.
The FCC-hh (Future Hadron-Hadron Circular Collider) is one of the options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group. In this overview the status and the evolution of the design of optics integration of FCC-hh are described, focusing on design of the arcs, alternatives, and tuning procedures.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF025
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MOPMF029 FCC-hh transverse impedance budget 149

• S. Arsenyev, D. Schulte
CERN, Geneva, Switzerland
• O. Boine-Frankenheim

Contributions of different machine elements of the proposed Future Circular Collider (FCC-hh) impedance budget are calculated based on beam stability considerations. For each element (the beamscreen, the collimators, etc), effective impedances are calculated at the injection energy and at the collision energy for considered instabilities. The considered instabilities include the transverse coupled bunch instability (TCBI) and the transverse mode coupling instability (TMCI). Limitations to each total effective impedance are estimated and the critical points in the impedance budget are determined.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF029
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MOPMF030 Broadband Impedance of Pumping Holes and Interconnects in the FCC-hh Beamscreen 153

• S. Arsenyev, D. Schulte
CERN, Geneva, Switzerland

In the proposed Future Circular Collider (FCC-hh) pumping holes and interconnects between sections of the beamscreen can be sources of unwanted broadband impedance, potentially leading to the transverse mode coupling instability (TMCI). The pumping holes pose a greater challenge to the impedance calculation due to their small contribution per hole. Unlike for the Large Hadron Collider (LHC), analytical methods cannot be applied due to the complex beamscreen geometry and the greater size of the holes. Instead, two computational methods are used and compared to each other. For the interconnects, the impedance due to a sophisticated system of tapers is also estimated using computational methods.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF030
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MOPMF031 Modelling Wake Impedance of a Rough Surface in Application to the FCC-hh Beamscreen 157

• S. Arsenyev, D. Schulte
CERN, Geneva, Switzerland

The inner surface of the future circular collider (FCC-hh) beamscreen is proposed to be laser-treated in order to mitigate the electron cloud build-up. However, the rough structure of the treated surface can result in unwanted impedance increase, potentially leading to the transverse mode coupling instability (TMCI). Three models have been adopted to estimate the wake impedance of a beamscreen with a rough surface. The models use the resistive wall formalism generalized for the case of an arbitrary surface impedance. The results apply to a beamscreen of a circular cross-section with the homogeneously rough inner surface for the case of ultrarelativistic particles. The free parameters of the models were fit into preliminary measurements of the surface resistivity, giving, as a result, a range of the real and the imaginary parts of the wake impedance.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF031
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MOPMF032 Nonlinear Correction Strategies for the LHC Using Resonance Driving Terms 161

• F.S. Carlier, E.H. Maclean, T. Persson, R. Tomás
CERN, Geneva, Switzerland

The correction of nonlinearities in future colliders is critical to reach operational conditions and pose a significant challenge for commissioning schemes. Several approaches have been succesfully used in the LHC to correct sextupolar and octupolar sources in the LHC insertion regions. Measurements of resonance driving terms at top energy in the LHC have improved and now offer a new observable to calculate and validate nonlinear corrections. This paper reports on measurements of resonance driving terms in the LHC and the relevant strategies used for nonlinear corrections.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF032
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MOPMF033 Probing the Forced Dynamic Aperture in the LHC at Top Energy Using AC Dipoles 165
SUSPF001   use link to see paper's listing under its alternate paper code

• F.S. Carlier, M. Giovannozzi, E.H. Maclean, T. Persson, R. Tomás
CERN, Geneva, Switzerland

Measurements of the dynamic aperture in colliders are a common method to ensure machine performance and offer an insight in the nonlinear content of the machine. Such direct measurements are very challenging for the LHC and High Luminosity LHC. Forced dynamic aperture has been demonstrated for the first time in the LHC at injection energy as a potential new observable to safely probe the nonlinear content of the machine. This paper presents the first measurements of forced dynamic aperture at top energy and discusses the proposed measurement schemes and challenges.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF033
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MOPMF036 FCC-ee Hybrid RF Scheme 173

• Sh. Gorgi Zadeh, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
• R. Calaga, F. Gerigk
CERN, Geneva, Switzerland

Funding: Research supported by the FCC design study
For FCC-ee, the range of beam energies and beam currents is large between each mode of operation, all scaled to an available 50 MW maximum power per beam. The two limiting scenarios for the RF system design are at low energy (45 GeV) with high beam current (1.45 A) and the highest energy (182.5 GeV) with a radiation loss reaching 8.92 GeV per turn. In this paper, RF staging with a hybrid scheme using both 400 MHz and 800 MHz is proposed to mitigate the requirements on the two extremes. Relevant comparisons are made with respect to using only a single frequency for all modes.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF036
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MOPMF038 Cleaning Performance of the Collimation System with Xe Beams at the Large Hadron Collider 176

• N. Fuster-Martínez, R. Bruce, P.D. Hermes, J.M. Jowett, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

The LHC heavy-ion program with Pb ions has delivered substantial physics results since the startup of the LHC. There was a Xe run in 2017 in which collimation losses and cleaning were assessed. These studies give a unique opportunity for very valuable benchmark of simulation models with measurements, which could also be very important to understand limitations for future runs with Pb and other species. In this paper, we present collimation loss maps measured in the first ever operation of the LHC with Xe ions. The measurements are compared with simulations and first conclusions are discussed for possible future operation.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF038
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MOPMF040 Crossing Angle Anti-Leveling at the LHC in 2017 184

• N. Karastathis, K. Fuchsberger, M. Hostettler, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

In 2017, LHC incorporated in operation an anti-leveling procedure of adapting in steps the crossing angle of the colliding beams to increase the integrated luminosity. In this paper, we present the Dynamic Aperture simulations that were employed to identify the operational margins, and therefore define the leveling steps. The results are complemented by observations from nominal operation and projections for the 2018 operation. Additional anti-leveling techniques, investigated in dedicated machine studies are also discussed
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF040
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MOPMF041 Refining the HL-LHC Operational Settings with Inputs From Dynamic Aperture Simulations: A Progress Report 188

• N. Karastathis, R. De Maria, S.D. Fartoukh, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

Recent Dynamic Aperture (DA) simulations aimed at providing guidance for the latest updates of the operational scenario for the High Luminosity upgrade of the LHC. The impact of the increased chromaticity and octupole current has been assessed considering the latest updates of the optics. Additional means to improve the lifetime, such as tune optimization, have been identified and deployed. We also briefly discuss the impact of delivering high luminosity to the LHCb experiment.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF041
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MOPMF042 Crab Cavity Failures Combined with a Loss of the Beam-Beam Kick in the High Luminosity LHC 192

• B. Lindstrom, H. Burkhardt, V.K.B. Olsen, A. Santamaría García, K.N. Sjobak, M. Valette, D. Wollmann
CERN, Geneva, Switzerland

Crab cavities are an essential component of the High Luminosity LHC (HL-LHC) project. In case of a failure they can create large transverse kicks on the beam within tens of microseconds and, therefore, require a fast extraction of the circulating beam. In this paper, the effects of different crab cavity failures in combination with the missing beam-beam kick following the dump of only one LHC beam are presented and consequences for the interlocking strategy of crab cavities are discussed.
Work supported by the High Luminosity LHC project.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF042
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MOPMF044 New Coordination Tools to Prepare Programmed Stops in the LHC and its Injectors 200

• S. Chemli, M. Bernardini, T.W. Birtwistle, A. Bolognesi, B. Brito Da Palma, S.E. Bustamante, J. Coupard, K. Foraz, E. Kleszcz, N. Kotsolakos, T. Krastev, P. A. Kulig, Y. Muttoni, B. Nicquevert, L. Pater, A. Patrascoiu, S. Petit, C. Rauser, A. Wardzinska
CERN, Geneva, Switzerland

The LHC and its Injectors are submitted to an overall lifecycle of three to four years of physics delivery to Experiments with a two-year long stop, also known as Long Shutdown (LS). The years of physics delivery are ended by a programmed stop for the immediate preventive and corrective maintenance, also known as (Extended)-Year-End Technical Stop - (E)YETS. This regular cycle is to be addressed in parallel with other projects: the upgrade projects to the accelerator complex of the LHC (High-Luminosity project) and to its Injectors (LHC Injectors Upgrade), and the "standard" consolidation tasks. This paper describes the way the programmed stops coordination group prepares the activities to take place during the stop with a set of new tools and processes that ease the communication between the stakeholders of the coordination.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF044
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MOPMF046 Simulation of Hydrodynamic Tunneling Caused by High Energy Proton Beam in Copper through Coupling of FLUKA and Autodyn 204

• Y.C. Nie, A. Bertarelli, F. Carra, C. Fichera, L.K. Mettler, R. Schmidt, D. Wollmann
CERN, Geneva, Switzerland

For machine protection of high-energy colliders, it is important to assess potential damages caused to accelerator components in case large number of bunches are lost at the same place. The numerical assessment requires an iterative execution of an energy-deposition code and a hydrodynamic code, since the hydrodynamic tunneling effect will likely play an important role in the beam-matter interactions. For proton accelerators at CERN and for the Future Circular Collider (FCC), case studies were performed, coupling FLUKA and BIG2. To compare different hydrocodes and not to rely only on BIG2, FLUKA and a commercial tool, Autodyn, have been used to perform these simulations. This paper reports a benchmarking study against a beam test performed at the HiRadMat (High-Radiation to Materials) facility using beams at 440 GeV from the Super Proton Synchrotron. Good agreement has been found between the simulation results and the test as well as previous simulations with FLUKA and BIG2, particularly in terms of penetration depth of the beam in copper. This makes the coupling of FLUKA and Autodyn an alternative solution to simulating the hydrodynamic tunneling. More case studies are planned for FCC and other high-beam-power accelerators.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF046
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MOPMF047 Transverse Coupling Measurements With High Intensity Beams Using Driven Oscillations 208

• T. Persson, G. Baud, X. Buffat, J.M. Coello de Portugal, E. Fol, K. Fuchsberger, M. Gabriel, M. Gąsior, M. Giovannozzi, G.H. Hemelsoet, M. Hostettler, M. Hruska, D. Jacquet, E.H. Maclean, L. Malina, J. Olexa, P.K. Skowroński, M. Solfaroli Camillocci, M.E. Söderén, R. Tomás, D. Valuch, A. Wegscheider, J. Wenninger
CERN, Geneva, Switzerland

Transverse coupling has been linked to instabilities and reduction in dynamic aperture and is hence a crucial parameter to control in the LHC. In this article we describe the development to use driven oscillations to measure the transverse coupling with high intensity beams. The method relies on the use of the transverse damper to drive an oscillation in a similar way as with an AC-dipole. The calculation of the coupling is based on the turn-by-turn data from all available BPMs gated for the excited bunch.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF047
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MOPMF048 Aperture Measurements with AC Dipole at the Large Hadron Collider 212

• N. Fuster-Martínez, R. Bruce, J. Dilly, E.H. Maclean, T. Persson, S. Redaelli, R. Tomás
CERN, Geneva, Switzerland
• L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom

Global aperture measurements are crucial for a safe operation and to push the performance of the LHC, in particular, the knowledge of aperture at top energy allows pushing the optics to reduce the colliding beam sizes. The standard method used in the LHC commissioning requires using several bunches for one measurement and makes bunches un-usable for other activities. This paper presents first global aperture measurements performed at injection with a new method using the AC dipole. This method consists in exciting large coherent oscillations of the beam without spoiling its emittance. A gentle control of the oscillation amplitude enables re-using the beams for several measurements. These measurements are compared with aperture measurements performed using the standard method and possible benefits, for example for optics measurements, at top energy with squeezed optics, are elaborated.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF048
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MOPMF050 LHC Operational Experience of the 6.5 TeV Proton Run with ATS Optics 216

• M. Pojer, M. Albert, R. Alemany-Fernández, T. Argyropoulos, E. Bravin, A. Calia, G.E. Crockford, S.D. Fartoukh, K. Fuchsberger, R. Giachino, M. Giovannozzi, G.H. Hemelsoet, M. Hostettler, W. Höfle, Y. Le Borgne, D. Nisbet, L. Ponce, S. Redaelli, B. Salvachua, M. Solfaroli, R. Suykerbuyk, D.J. Walsh, J. Wenninger, M. Zerlauth
CERN, Geneva, Switzerland

In May 2017, the CERN Large Hadron Collider (LHC) restarted operations at 6.5 TeV using the Achromatic Telescopic Squeeze (ATS) scheme with a target beta-star of 40 cm in ATLAS and CMS. The number of bunches was progressively increased to a maximum of 2556 with emittances of 2.5 um. In August, several machine parameters had to be re-tuned to mitigate beam loss induced instabilities and maintain a steady increase of the instantaneous luminosity. The use of a novel beam type and filling pattern produced in the injectors, allowed filling the machine with very low emittance beam (1.5 um) achieving an equivalent luminosity with 1868 bunches. In September, the beta-star was further lowered to 30 cm (using, for the first time, the telescopic technique of the ATS) and the bunch intensity pushed to 1.25·1011 protons. In the last 3 months of 2017, the LHC produced more than 500 pb-1 of integrated luminosity per day, delivering to each of the high luminosity experiments 50.6 fb-1, 10% above the 2017 target. A general overview of the operational aspects of the 2017 proton run will be presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF050
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MOPMF051 LHC Operational Scenarios During 2017 Run 220

• B. Salvachua, M. Albert, R. Alemany-Fernández, T. Argyropoulos, E. Bravin, H. Burkhardt, G.E. Crockford, JCD. Dumont, S.D. Fartoukh, K. Fuchsberger, R. Giachino, M. Giovannozzi, G.H. Hemelsoet, W. Höfle, J.M. Jowett, Y. Le Borgne, D. Nisbet, M. Pojer, L. Ponce, S. Redaelli, M. Solfaroli, R. Suykerbuyk, D.J. Walsh, J. Wenninger, M. Zerlauth
CERN, Geneva, Switzerland

During 2017, the Large Hadron Collider LHC delivered luminosity for different physics configuration in addtion to the nominal 6.5 TeV proton-proton run. About 18.5 days were dedicated to commission and to deliver special physics to the experiments. Condifurations with large beta-star of 19 m and 24 m were prepared for luminosity calibration with Van de Meer scans. A proton-proton run at 2.51 TeV took place during the last weeks of November to provide reference data for the heavy ion (Pb-Pb, p-Pb) collisions at the same equivalent nucleon energy . A very short (0.5 days) but effective ion run was scheduled where the LHC saw the first Xe beams collissions and delivered around 3 ub-1 to ATLAS and CMS. The run ended with a low event pile-up run at 6.5TeV. This contribution summarizes the operational aspects and delivered targets for the different configurations.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF051
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MOPMF052 Monitoring and Modeling of the LHC Luminosity Evolution in 2017 224

• N. Karastathis, F. Antoniou, I. Efthymiopoulos, M. Hostettler, G. Iadarola, S. Papadopoulou, Y. Papaphilippou, D. Pellegrini, B. Salvachua
CERN, Geneva, Switzerland

In 2017, the Large Hadron Collider (LHC) restarted operation at 6.5 TeV, after an extended end-of-the-year stop, scheduled to deliver 45/fb to the two general-purpose experiments. Continuous monitoring of the key beam parameters and machine configurations that impact the delivered luminosity was introduced, providing fast feedback to operations for further optimisation. The numerical model based on simulations and use of selected machine parameters to estimate the machine luminosity was further developed. The luminosity evolution and comparisons to the model predictions is presented in this paper. The impact of the dynamic variation of the crossing angle, which was incorporated into nominal LHC operation, is also discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF052
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MOPMF053 Observations, Analysis and Mitigation of Recurrent LHC Beam Dumps Caused by Fast Losses in Arc Half-Cell 16L2 228

• J.M. Jimenez, D. Amorim, S. A. Antipov, G. Arduini, A. Bertarelli, N. Biancacci, B. Bradu, E. Bravin, G. Bregliozzi, K. Brodzinski, R. Bruce, X. Buffat, L.R. Carver, P. Chiggiato, S.D. Claudet, P. Collier, R. Garcia Alia, M. Giovannozzi, L. K. Grob, E.B. Holzer, W. Höfle, G. Iadarola, G. Kotzian, A. Lechner, T.E. Levens, B. Lindstrom, T. Medvedeva, A. Milanese, D. Mirarchi, E. Métral, D. Perini, S. Redaelli, G. Rumolo, B. Salvant, R. Schmidt, M. Valette, D. Valuch, J. Wenninger, D. Wollmann, C. Yin Vallgren, C. Zamantzas, M. Zerlauth
CERN, Geneva, Switzerland
• D. Amorim
Université Grenoble Alpes, Grenoble, France
• A.A. Gorzawski
University of Manchester, Manchester, United Kingdom
• L. Mether
EPFL, Lausanne, Switzerland

Recurrent beam dumps significantly perturbed the operation of the CERN LHC in the summer months of 2017, especially in August. These unexpected beam dumps were triggered by fast beam losses that built up in the cryogenic beam vacuum at the half-cell 16 left of LHC-IP2 and were detected either at that location but mainly in the collimation insertions. This contribution details the experimental observables (beam losses, coherent instabilities, heat load to cryogenic system, vacuum signals), the extent of the understanding of the beam loss and instability mechanisms and the mitigation steps and new settings that allowed recovering the luminosity performance of the LHC for the rest of the Run.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF053
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MOPMF054 Comparison of Different Transverse Emittance Measurement Techniques in the Proton Synchrotron Booster 232

• G.P. Di Giovanni, S.C.P. Albright, V. Forte, M.A. Fraser, G. Guidoboni, B. Mikulec, F. Roncarolo, A. Santamaría García
CERN, Geneva, Switzerland

The measurement of the transverse emittance in an accelerator is a crucial parameter to evaluate the performance of the machine and to understand beam dynamics processes. In recent years, controlling and understanding the emittance became particularly relevant in the Proton Synchrotron Booster (PSB) at CERN as part of the LHC Injectors Upgrade (LIU). The LIU project is a necessary step to achieve the goals of the High-Luminosity LHC project. In this framework, an accurate and reliable emittance measurement of high brightness beams is mandatory to study the brightness reach of the LHC injectors. In the PSB there are two main instruments available for emittance measurements: wire scanners and secondary-emission (SEM) grids. In this paper emittance measurements performed during the 2017 physics run with these two systems are compared, taking into account various systematic error sources.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF054
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MOPMF056 The Second LHC Long Shutdown (LS2) for the Superconducting Magnets 240

• J.Ph. G. L. Tock, M. Bednarek, L. Bottura, E. Karentzos, S.L.N. Le Naour, F. Meuter, M. Pojer, C.E. Scheuerlein, E. Todesco, D. Tommasini, L. X. Van Den Boogaard, G.P. Willering
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) has been delivering data to the physics experiments since 2009. It first operated at a centre of mass energy of 7 TeV and 8 TeV up to the first long shutdown (LS1) in 2013-14. The 13 kA splices between the main LHC cryomagnets were consolidated during LS1. Then, it was possible to increase safely the centre of mass energy to 13 TeV. During the training campaigns, metallic debris caused short circuits in the dipole diode containers, leading to an unacceptable risk. Major interventions can only take place during multiyear shutdowns. To ensure safe operation at higher energies, hence requiring further magnets training, the electrical insulation of the 1232 dipole diodes bus-bars will be consolidated during the second LHC long shutdown (LS2) in 2019-20. The design of the reinforced electrical insulation of the dipole cold diodes and the associated project organisation are presented, including the validation tests, especially at cryogenics temperature. During LS2, maintenance interventions on the LHC cryomagnets will also be performed, following the plan based on a statistical analysis of the electrical faults. It is inscribed in the overall strategy to produce collisions at 14 TeV, the LHC design energy, and to push it further towards 15 TeV. We give a first guess on the impact on the LHC failure rate.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF056
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MOPMF058 Status of the LHC Schottky Monitors 247

• T. Tydecks, D. Alves, T.E. Levens, M. Wendt, J. Wenninger
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) features four transverse Schottky monitors detecting Schottky noise from the beam. From the Schottky noise signal, beam properties like tune, chromaticity, and bunch by bunch relative emittances, can be extracted. Being a non-destructive and purely parasitic method of measurement, the Schottky system is of great interest for real-time determination of beam chromaticities especially. Studies, including a dedicated machine development shift as well as parasitic measurements, concerning its capability to accurately measure the beam chromaticities are presented.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF058
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MOPMF060 Safe Disposal of the LHC Beam without Beam Dump - Method and Experimental Verification 253

• M. Valette, B. Lindstrom, A. Mereghetti, R. Schmidt, M. Solfaroli, J.A. Uythoven, D. Valuch, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
In the extremely unlikely event of a non-working beam dumping system in the LHC, the 360 MJ of stored beam energy can be dissipated in the collimation system as a last mitigation measure. In such a situation, it is important to reduce the stored beam energy both quickly and at the same time as smoothly as possible in order to limit the risk of trips of critical systems, to avoid quenches of superconducting magnets (which would lead to changes of the beam trajectory and damage to the accelerator) and ultimately damage to the collimators themselves. Detailed steps and parameters have been developed and validated during two dedicated experiments with beam in the LHC. This paper summarizes the key aspects in view of the preparation of such a procedure for operational use, which will allow for the safe disposal of the full LHC beam by the operation crews.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF060
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MOPMF061 Emittance Growth in Coast in the SPS at CERN 257

• F. Antoniou, H. Bartosik, T. Bohl, R. Calaga, L.R. Carver, J. Repond, G. Vandoni
CERN, Geneva, Switzerland
• A. Alekou
UMAN, Manchester, United Kingdom

Funding: Research supported by the HL-LHC project.
The HL-LHC prototype crab-cavities are installed in the CERN SPS, which will allow for a comprehensive beam test with high energy protons for the first time. As the time available for experimental beam dynamics studies with the crab cavities installed in the machine will be limited, a very good preparation is required. One of the main concerns is the induced emittance growth, driven by phase amplitude jitter in the crab cavities. In this respect, several machine development (MD) studies were performed during the past years to quantify and characterize the long term emittance evolution of proton beams in the SPS. In these proceedings, the experimental observations from past years are summarized and the MD studies from 2016 and 2017 are presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF061
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MOPMF064 High-Energy LHC Design 269

• F. Zimmermann, D. Amorim, S. A. Antipov, S. Arsenyev, M. Benedikt, R. Bruce, M.P. Crouch, S.D. Fartoukh, M. Giovannozzi, B. Goddard, M. Hofer, R. Kersevan, V. Mertens, Y. Muttoni, J.A. Osborne, V. Parma, V. Raginel, S. Redaelli, T. Risselada, I. Ruehl, B. Salvant, D. Schoerling, E.N. Shaposhnikova, L.J. Tavian, E. Todesco, R. Tomás, D. Tommasini, F. Valchkova-Georgieva, V. Venturi, D. Wollmann
CERN, Geneva, Switzerland
• J.L. Abelleira, E. Cruz Alaniz, P. Martinez Mirave, A. Seryi, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
• A. Apyan
ANSL, Yerevan, Armenia
• J. Barranco García, L. Mether, T. Pieloni, L. Rivkin, C. Tambasco
EPFL, Lausanne, Switzerland
• F. Burkart
DESY, Hamburg, Germany
• Y. Cai, Y.M. Nosochkov
SLAC, Menlo Park, California, USA
• G. Guillermo Cantón
CINVESTAV, Mérida, Mexico
• K. Ohmi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

In the frame of the FCC study we are designing a 27 TeV hadron collider in the LHC tunnel, called the High Energy LHC (HE-LHC).
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF064
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MOPMF067 Optimized Arc Optics for the HE-LHC 277

• Y.M. Nosochkov, Y. Cai
SLAC, Menlo Park, California, USA
• M.P. Crouch, M. Giovannozzi, M. Hofer, J. Keintzel, T. Risselada, E. Todesco, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
• D. Zhou
KEK, Ibaraki, Japan
• L. van Riesen-Haupt
JAI, Oxford, United Kingdom

Funding: Work supported by the European Commission under Capacities 7th Framework Programme project EuCARD-2, grant agreement 312453, and the HORIZON 2020 project EuroCirCol, grant agreement 654305.
The High Energy LHC (HE-LHC) proton-proton collider is a proposed replacement of the LHC in the existing 27-km tunnel, with the goal of reaching the centre-of-mass beam energy of 27 TeV. The required higher dipole field can be realized by using 16-T dipoles being developed for the FCC-hh design. A major concern is the dynamic aperture at injection energy due to degraded field quality of the new dipole based on Nb3Sn superconductor, the potentially large energy swing between injection and collision, and the slightly reduced magnet aperture. Another issue is the field in quadrupoles and sextupoles at top energy, for which it may be cost-effective, wherever possible, to stay with Nb-Ti technology. In this study, we explore design options differed by arc lattice, for three choices of injection energy, with the goal of attaining acceptable magnet field and maximum injection dynamic aperture with dipole non-linear field errors.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF067
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MOPMF069 The High Energy LHC Beam-Beam Effects studies 285

• T. Pieloni, J. Barranco García, L. Rivkin, C. Tambasco
EPFL, Lausanne, Switzerland
• D. Amorim, S. A. Antipov, X. Buffat, B. Salvant, F. Zimmermann
CERN, Geneva, Switzerland

Funding: This work is supported by the Swiss State Secretariat for Education, Research and Innovation SERI.
We present in this paper the studies of beam-beam effects for the High Energy Large Hadron Collider. We will describe and review the different aspects of beam-beam interactions (i.e. orbit effects, Landau damping, compensation schemes and operational set-up). An operational scenario for the collider will also be given as a result of the study.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF069
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MOPMK001 Optics for RF Acceleration Section for the High Energy Large Hadron Collider 345

• L. van Riesen-Haupt, J.L. Abelleira
University of Oxford, Oxford, United Kingdom
• J.L. Abelleira, E. Cruz Alaniz, P. Martinez Mirave, A. Seryi
JAI, Oxford, United Kingdom
• M. Hofer, F. Zimmermann
CERN, Geneva, Switzerland
• D. Zhou
KEK, Ibaraki, Japan

Funding: Work supported by the Horizon 2020 project EuroCirCol, grant 654305 and by the Science and Technology Facilities Council
As part of the FCC study, the design of the High Energy LHC (HE-LHC) is addressed. A proposed layout for the interaction region for the containing the radio frequency (RF) cavities and various beam instrumentation will be discussed. The higher energy requires more RF cavities, which strongly restricts the space available for optics and instrumentation. Another challenge arises because the beam rigidity increases whilst the LHC geometry has to be conserved. To this end, next generation dipoles have to be used in order to achieve sufficient beam to beam separation. A design that provides enough beam stay clear (BSC) in all the magnets will be presented. The design introduces an additional quadrupole on either side of the RF region to be used for phase advance adjustments that can increase the dynamic aperture.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK001
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MOPMK002 Integrated Full HE-LHC Optics and Its Performance 348

• M. Hofer
TU Vienna, Wien, Austria
• M.P. Crouch, J. Keintzel, T. Risselada, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
• Y.M. Nosochkov
SLAC, Menlo Park, California, USA
• D. Zhou
KEK, Ibaraki, Japan
• L. van Riesen-Haupt
JAI, Oxford, United Kingdom

One possible future hadron collider design investigated in the framework of the Future Circular Collider (FCC) study is the High-Energy LHC (HE-LHC). Using the 16 T dipoles developed for the FCC-hh the center of mass energy of the LHC is set to increase to 27 TeV. To achieve this set energy goal, a new optics design is required, taking into account the constraint from the LHC tunnel geometry. In this paper, two different lattices for the HE-LHC are presented. Initial considerations take into account the physical aperture at the proposed injection energy as well as the energy reach of these lattices. The dynamic aperture at the injection energies is determined using latest evaluations of the field quality of the main dipoles.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK002
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MOPMK003 Energy Deposition Studies and Luminosity Evolution for the Alternative FCC-hh Triplet 352

• J.L. Abelleira, E. Cruz Alaniz, A. Seryi, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
• J.L. Abelleira, E. Cruz Alaniz, L. van Riesen-Haupt
University of Oxford, Oxford, United Kingdom

Funding: Work supported by EuroCircol, EU's Horizon 2020 grant No 654305 & STFC grant to the John Adams Institute
The international Future Circular Collider (FCC) study comprises the development of a new scientific structure in a tunnel of 100 km. This will allow the installation of a proton collider with a centre of mass energy of 100 TeV, called FCC-hh. An alternative design of the final focus triplet for the FCC-hh has been developed in parallel to the alternative one, and adapted to the constraint of a free length (L*) of 40 m. We discuss in this paper the energy deposition issues as well as the luminosity evolution for two different optics choices: round and flat beams.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK003
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MOPMK005 HE-LHC Final Focus: Flat Beam Parameters and Energy Deposition Studies 356

• J.L. Abelleira, E. Cruz Alaniz, A. Seryi, L. van Riesen-Haupt
JAI, Oxford, United Kingdom
• J.L. Abelleira, E. Cruz Alaniz, L. van Riesen-Haupt
University of Oxford, Oxford, United Kingdom

Funding: Work supported by EuroCircol, EU's Horizon 2020 grant No 654305 & STFC grant to the John Adams Institute
The High Energy LHC (HE-LHC) project is studying the feasibility of a new proton-proton collider with a beam energy of 13.5 TeV. The nominal optics features a β* of 0.25 m and crab-cavities. Here we present a flat-beam optics that can be used with a non-zero crossing angle, in the absence of crab cavities. This is followed by energy deposition studies for the superconducting quadrupoles and dipole separators. The total dose in these magnets coming from the collision debris is evaluated.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK005
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MOPMK006 Experimental Interaction Region Optics for the High Energy LHC 360
SUSPF002   use link to see paper's listing under its alternate paper code

• L. van Riesen-Haupt, J.L. Abelleira
University of Oxford, Oxford, United Kingdom
• J.L. Abelleira, E. Cruz Alaniz, A. Seryi
JAI, Oxford, United Kingdom
• M.P. Crouch, F. Zimmermann
CERN, Geneva, Switzerland
• D. Zhou
KEK, Ibaraki, Japan

Funding: Work supported by the Horizon 2020 project EuroCirCol, grant 654305 and by the Science and Technology Facilities Council
The High Energy LHC (HE-LHC) is one option for a next generation hadron collider explored in the FCC-hh program. The core concept of the HE-LHC is to install FCC-hh technology magnets in the LHC tunnel. The higher beam rigidity and the increased radiation debris, however, impose severe challenges on the design of the triplet for the low beta insertions. In order to achieve 25 cm β* optics and survive a lifetime integrated luminosity of 10 ab-1 a new longer triplet was designed that provides sufficient shielding and enough beam stay clear. This triplet has been designed using complimentary radiation studies to optimise the shielding that will also be presented. The optics for the rest of the interaction region had to be adjusted in order to host this more rigid beam and longer triplet whilst leaving enough room for crab cavities. Moreover, the effects non-linear errors in this triplet have on the dynamic aperture will be outlined.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK006
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MOPMK007 An Optimised Triplet for the Final Focus of the FCC-HH with a 40m Final Drift 364

• L. van Riesen-Haupt, J.L. Abelleira
University of Oxford, Oxford, United Kingdom
• J.L. Abelleira, E. Cruz Alaniz, A. Seryi
JAI, Oxford, United Kingdom

Funding: Work supported by the Horizon 2020 project EuroCirCol, grant 654305 and by the Science and Technology Facilities Council
The sizes of the beta functions in the final focus triplet of a synchrotron collider have a great impact on the chromaticity and dynamic aperture of the machine. These beta functions are proportional to the square of the length of the final drift so it is desirable to keep it as short as possible whilst leaving enough room for the experiment. In the latest design of the FCC-hh this drift was reduced from 45 m to 40 m. In the following an alternative final focus for this new design will be presented. The effects this change has on the interaction region will examined and discussed.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK007
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MOPMK014 Resistive-Wall Impedance of Insertions for FCC-hh 378

• B. Riemann, S. Khan
DELTA, Dortmund, Germany
• S. Arsenyev, D. Schulte
CERN, Geneva, Switzerland

Funding: This work is supported by the German Ministry of Education & Research (BMBF, funding code 05P15PERB1) and CERN (reference numbers KE3123, EDMS 1606722).
In this work, transverse and longitudinal resistive-wall impedances for beam pipes in the experiment, injection, extraction and RF systems insertion regions of the Future Hadron-Hadron Collider (FCC-hh) are computed based on contributions from different given cross sections of the surrounding (elliptical) chamber parts along the beam path, their temperature-dependent conductivities, and optical functions. An emphasis is placed on the behaviour of transverse impedance in the main experimental regions (A and G), where maximum beta values of 104 to 105 m occur in dependence of the operation mode respectively lattice configuration. Main contributions to the transverse and longitudinal impedance budget are identified, and possibilities of reducing them are discussed.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK014
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MOPML002 Status of the JLEIC Ion Collider Ring Design 394

• G.H. Wei, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA
• Y. Cai, Y.M. Nosochkov
SLAC, Menlo Park, California, USA

Funding: Authored by JSA, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. Work supported also by the US DOE Contract DE-AC02-76SF00515.
We present an update on the lattice design and beam dynamics study of the ion collider ring of JLEIC (Jefferson Lab Electron Ion Collider). The collider ring consists of two 261.7 degree arcs connected by two straight sections crossing each other. One of the straights houses an interaction region (IR) and is shaped to make a 50 mrad crossing angle with the electron beam at the interaction point (IP) to meet physics requirements. The forward acceptance requirements downstream of the IP in the ion direction lead to an asymmetric IR lattice design. The detector solenoid effects and the multipole fields of the IR magnets further complicate this picture. In this paper, compensation of the detector solenoid effects is considered together with orbit correction and multipole effects. We also study local compensation of the magnet multipoles using dedicated multipole correctors. And an optimization of the betatron tunes is also presented.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML002
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MOPML009 New High Luminosity LHC Baseline and Performance at Ultimate Energy 408

• L.E. Medina Medrano
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
• A. Apollonio, G. Arduini, O.S. Brüning, M. Giovannozzi, L.E. Medina Medrano, S. Papadopoulou, Y. Papaphilippou, S. Redaelli, R. Tomás
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project and the Beam project (CONACYT, Mexico).
The LHC machine is envisioned to operate eventually at an ultimate beam energy of 7.5 TeV at the end of LHC Run 4, i.e. after commissioning of the HL-LHC systems, a stage falling into the High Luminosity LHC (HL-LHC) era. In this paper we review the latest baseline parameters and performance, and study the potential reach of the HL-LHC with pushed optics at the ultimate beam energy. Results in terms of integrated luminosity and effective pile-up density of both the nominal (5.0×1034 cm-2 s−1) and ultimate (7.5×1034 cm-2 s−1) levelling operations are discussed

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML009
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MOPML012 Special Collimation System Configuration for the LHC High-Beta Runs 418

• H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom
• R. Bruce, H. Burkhardt, M. Deile, S. Jakobsen, A. Mereghetti, S. Redaelli
CERN, Geneva, Switzerland

Special LHC high-beta optics is required for the forward physics program of TOTEM and ATLAS-ALFA. In this configuration, the beam is de-squeezed (the \beta-function at the collision point is increased) in order to minimize the divergence for measurements at very small scattering angles. In these low beam intensity runs, it is important to place the Roman Pots (RPs) as close as possible to the beam, which demands special collimator settings. During Run I, a significant amount of background was observed in the forward detectors due to particles outscattered from the primary collimator. During Run II, a different collimation configuration was used where a tungsten collimator was used as primary collimator instead of the usual one made of carbon. Using this configuration, a significant reduction of the background at the RPs was observed. In this paper we present a description of the new collimator configuration and the results obtained during the high-beta run carried out in 2016.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML012
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TUXGBD2 Colliding Heavy Ions in the LHC 584

• J.M. Jowett
CERN, Geneva, Switzerland

The Large Hadron Collider at CERN not only collides protons but also heavier nuclei. So far Pb+Pb, Xe-Xe and p+Pb collisions, at multiple energies, have been provided for what was initially conceived as a distinct physics program on the collective behavior of QCD matter at extreme energy density and temperature. However unexpected phenomena observed in p+Pb and p+p collisions at equivalent energies have blurred the distinction. Intense, low-emittance, ion beams are provided by a dedicated source and injector chain setup. When Pb beams collide, new luminosity limits arise from photon-photon and photonuclear interactions but effective mitigations have allowed luminosities over 3 times design. Asymmetric p+Pb collisions introduce new features and beam-dynamical phenomena into operation of the LHC but have also achieved luminosity far beyond expectations. With experimental requirements for multiple changes in energy and data-taking configurations during very short heavy-ion runs, high operational efficiency and reliability are vital. This invited talk discusses performance, future prospects, and technical challenges for the LHC heavy ion program, including injector performance.
Slides TUXGBD2 [5.322 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBD2
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THYGBD2 Results of UFO Dynamics Studies with Beam in the LHC 2914

• B. Lindstrom, A. Apollonio, P. Bélanger, M. Dziadosz, A.A. Gorzawski, L. K. Grob, E.B. Holzer, A. Lechner, R. Schmidt, M. Valette, D. Valuch, D. Wollmann
CERN, Geneva, Switzerland

Micrometer sized particles entering the LHC beam (the so-called Unidentified Falling Objects or UFOs) are a known cause of localized beam losses since the beginning of high intensity beam operation, however the origin of these particles is not fully known. Their effect limits LHC availability by causing premature dumps due to excessive beam losses and occasionally even magnet quenches. This could become an important limitation for future accelerators such as the High Luminosity upgrade of the LHC (HL-LHC) and the Future Circular Collider (FCC). The dynamics of these UFOs was investigated in two dedicated experiments. In the first experiment, it was shown that the transverse movements of these particles can be studied by observing bunch-by-bunch losses from bunches with different horizontal and vertical emittances. In the second experiment, UFO-like events around the 16L2 interconnect in the LHC, which has seen intense UFO activity in 2017, were studied with the above method. This paper summarizes the results of both experiments.
Slides THYGBD2 [1.361 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD2
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THYGBD3 Beam-beam Studies for Super Proton-Proton Collider 2918

• L.J. Wang, J.Y. Tang
IHEP, Beijing, People's Republic of China
• K. Ohmi
KEK, Ibaraki, Japan

In China, a two-stage circular collider project, CEPC-SPPC has been proposed. The first stage, CEPC (Circular Electron Positron Collier, a so-called Higgs factory) is focused on the Higgs physics, and the second stage, SPPC (Super Proton-Proton Collider) will be an energy frontier collider and a discovery machine. Luminosity is a key factor for any particle-physics colliders. With the increasing bunch population, beam-beam interaction is increasingly become the limit factor of luminosity improvement. The finite crossing angle scheme is considered firstly. Meanwhile, long-range interaction is another significant source of luminosity degrade. In this report, firstly, we don't consider long-range interactions and study luminosity degrade with crossing angle and without crossing angle for horizontal crossing and horizontal-vertical crossing. Secondly we discuss luminosity decay with long-range interactions for horizontal crossing and horizontal-vertical crossing. Thirdly, we talk about emittance growth and luminosity degradation using resonance analysis for different scenarios. Finally the resulting beam-beam limit will be concluded for SPPC.
Slides THYGBD3 [1.379 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD3
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THYGBD4 Landau Damping by Electron Lenses 2921

• A.V. Burov, Y.I. Alexahin, V.D. Shiltsev, A. Valishev
Fermilab, Batavia, Illinois, USA

Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important to note that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.
Slides THYGBD4 [4.506 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBD4
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THZGB1
Louis Costrell Awards Session: Introduction

• T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Introduction to session by Tor Raubenheimer
Slides THZGB1 [1.203 MB]
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THZGB2
IEEE/NPSS PAST Award Talk: Hermann Grunder

• H.A. Grunder
ANL, Argonne, Illinois, USA

IEEE/NPSS PAST Award Talk: Hermann Grunder
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THZGB3
IEEE/NPSS PAST Award Talk: Sandra Biedron

• S. Biedron
UNM, Albuquerque, New Mexico, USA

IEEE/NPSS PAST Award Talk: Sandra Biedron
Slides THZGB3 [13.844 MB]
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THZGB4
IEEE/NPSS PAST Thesis Award Talk: Martina Martinello

• M. Martinello
Fermilab, Batavia, Illinois, USA

IEEE/NPSS PAST Thesis Award Talk: Martina Martinello
Slides THZGB4 [22.930 MB]
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THZGB5
APS/DPB Thesis Award Talk 2017: Spencer Gessner

• S.J. Gessner
CERN, Geneva, Switzerland

APS/DPB Thesis Award Talk 2017: Spencer Gessner
Slides THZGB5 [11.333 MB]
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THZGB6
APS/DPB Thesis Award Talk 2018: Sergey Antipov

• S. A. Antipov
CERN, Geneva, Switzerland

APS/DPB Thesis Award Talk 2018: Sergey Antipov
Slides THZGB6 [1.711 MB]
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THZGB7
Wilson Award: Alex Chao

• A. Chao
SLAC, Menlo Park, California, USA

Wilson Award: Alex Chao
Slides THZGB7 [1.890 MB]
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FRYGB4
IPAC'19 Chair Closing Slides

• M.J. Boland