IPAC2018 - List of Authors (Redaelli, S.)

Paper	Title	Page
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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MOPMF039	First Xenon-Xenon Collisions in the LHC	180
	M. Schaumann, R. Alemany-Fernández, P. Baudrenghien, T. Bohl, C. Bracco, R. Bruce, N. Fuster-Martínez, M.A. Jebramcik, J.M. Jowett, T. Mertens, D. Mirarchi, S. Redaelli, B. Salvachua, M. Solfaroli, H. Timko, J. Wenninger CERN, Geneva, Switzerland
	In 2017, the CERN accelerator complex once again demonstrated its flexibility by producing beams of a new ion species, xenon, that were successfully injected into LHC. On 12 October, collisions of fully stripped xenon nuclei were recorded for the first time in the LHC at a centre-of-mass energy per colliding nucleon pair of 5.44 TeV. Physics data taking started 9.5 h after the first injection of xenon beams and lasted a total of 6 h. The integrated luminosity delivered to the four LHC experiments was sufficient that new physics results can be expected soon. We provide a general overview of this Xe-Xe pilot run before focussing on beam data at injection energy and at flat-top.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF039
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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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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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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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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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TUPAF029	Observation of Fast Losses in the LHC Operation in 2017	740
	A.A. Gorzawski, N. Fuster-Martínez, S. Redaelli, C. Xu, C. Zamantzas CERN, Geneva, Switzerland R.B. Appleby UMAN, Manchester, United Kingdom H. Garcia Morales Royal Holloway, University of London, Surrey, United Kingdom
	Four diamond detectors that provide beam loss measurements with time resolution in the nanosecond range were added in the vicinity of the primary collimators of the Large Hadron Collider (LHC). This is a powerful diagnostic tool that provides the unique chance to measure bunch-by-bunch losses. The operation of the LHC in 2017 presented several unusual events of fast, high intensity beam losses, many of them captured by the diamond detectors in the betatron cleaning region. In this paper we review some of the relevant loss cases that were analyzed in the wider scope of determining the source of the instability generating these losses. We show few of the possible applications of this detectors in daily operations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF029
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TUPAF045	Studies for Future Fixed-Target Experiments at the LHC in the Framework of the CERN Physics Beyond Colliders Study	798
	S. Redaelli, M. Ferro-Luzzi CERN, Geneva, Switzerland C. Hadjidakis IN2P3-CNRS, Orsay, France
	A study on prospects for Physics Beyond Colliders at CERN was launched in September 2016 to assess the capabilities of the existing accelerators complex. Among several other working groups, this initiative triggered the creation of a working group with the scope of studying a few specific proposals to perform fixed-target physics experiments at the Large Hadron Collider (LHC). This includes for example physics experiments with solid or gaseous internal targets, polarized gas targets, and experiments using bent-crystals for halo splitting from beam core for internal targets. The focus of the working group's activities is on the technical feasibility and on implications to the LHC ring. In this paper, the current status of the studies is presented and future plans are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF045
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TUPAF046	Conceptual Design of a Collimation System for the CERN Super Proton Synchrotron	802
	M. Patecki, A. Mereghetti, D. Mirarchi, S. Redaelli CERN, Geneva, Switzerland
	The Super Proton Synchrotron (SPS) is the last accelerator in the LHC Injectors Chain. Its performance is constantly being improved in frame of the LHC Injectors Upgrade (LIU) Project in order to prepare it for the future HL-LHC (High Luminosity LHC) operation. One of the LIU goals is to nearly double the intensity extracted from the SPS, up to 2.32×10¹¹ p/bunch. In recent years, nearly 10% of losses are observed for nominal intensity and LHC-type beams; they grow to about 20% for the intensity approaching the HL-LHC target. Beam losses imply activation and aging of the SPS hardware; the possibility to add a collimation system is being considered to mitigate this problem. In this paper we present studies of a collimation system design for the SPS. The concept is based on a primary horizontal collimator located in an available position with high enough dispersion, and a secondary collimator to intercept the particles leaking out from the primary collimator. Performance of the proposed collimation system is evaluated by means of numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF046
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WEYGBE4	Low-Impedance Collimators for HL-LHC	1794
	S. A. Antipov, N. Biancacci, R. Bruce, A. Mereghetti, D. Mirarchi, E. Métral, S. Redaelli, B. Salvant CERN, Geneva, Switzerland D. Amorim Université Grenoble Alpes, Grenoble, France
	The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will double its beam intensity for the needs of High Energy Physics frontier. This increase requires a reduction of the machine's impedance to ensure the coherent stability of the beams until they are put in collision. A major part of the impedance is the resistive wall contribution of the collimators. To reduce this contribution several coating options have been proposed. We have studied numerically the effect of the novel coatings on the beam stability. The results show that a decrease of up to 30% of the machine impedance and a reduction of up to 120 A in the stabilizing octupole current threshold can be achieved by coating the secondary collimators with Molybdenum. Half of that improvement can be obtained by coating the jaws of a subset of four collimators identified as the highest contributors to machine impedance. The installation of this subset of low-impedance collimators is planned for the Long Shutdown 2 in 2019-2020.
	Slides WEYGBE4 [5.719 MB]
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WEPAF080	Beam Size Measurements Based on Movable Quadrupolar Pick-ups	2028
	A. Sounas, M. Gąsior, T. Lefèvre, A. Mereghetti, J. Olexa, S. Redaelli, G. Valentino CERN, Geneva, Switzerland
	Measurements with quadrupolar pick-ups (PU) have attracted particular interest as non-intercepting diagnostics for determining the transverse beam size. They are based on processing the signals of an electromagnetic PU for the extraction of the second-order moment, which contains information about the beam size. Despite the simplicity of the concept, quadrupololar measurements have always been highly challenging in reality. This comes from the fact that the quadrupolar moment constitutes only a very small part of the total PU signal dominated by the intensity and the position signals. Therefore, the beam size information can easily be lost due to small imperfections in the signal processing chain, such as asymmetries in the electronics and cables. In this paper, we present a new method for quadrupolar measurements using movable PUs. Through position and aperture scans, our technique minimizes the parasitic beam position signal and takes into account imperfections of the PU, cables and electronics, thus enabling an efficient auto-calibration of the measurement system. Preliminary studies, using collimators with embedded electrostatic PUs in the LHC at CERN, have shown very promising results.
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WEPMF071	Dynamic Testing and Characterization of Advanced Materials in a New Experiment at CERN HiRadMat Facility	2534
	A. Bertarelli, C. Accettura, E. Berthomé, L. Bianchi, F. Carra, C. Fichera, M.I. Frankl, G. Gobbi, P. Grosclaude, M. Guinchard, A. Lechner, M. Pasquali, S. Redaelli, E. Rigutto, O. Sacristan De Frutos CERN, Geneva, Switzerland Ph. Bolz, P. Simon GSI, Darmstadt, Germany T.R. Furness University of Huddersfield, Huddersfield, United Kingdom J. Guardia Valenzuela Universidad de Zaragoza, Zaragoza, Spain P. Mollicone, M. Portelli UoM, Msida, Malta
	Funding: This work has received funding from the European Union's Horizon 2020 Research and Innovation programme under Grant Agreement No 730871. An innovative and comprehensive experiment (named "Multimat") was successfully carried out at CERN HiRadMat facility on 18 different materials relevant for Collimators and Beam Intercepting Devices. Material samples, tested under high intensity proton pulses of 440 GeV/c, exceeding the energy density expected in HL-LHC, ranged from very light carbon foams to tungsten heavy alloys, including novel composites as graphite/carbides and metal/diamond without and with thin-film coatings. Experimental data were acquired relying on extensive integrated instrumentation (strain gauges, temperature sensors, radiation-hard camera) and on laser Doppler vibrometer. This allows investigating relatively unexplored and fundamental phenomena as dynamic strength, internal energy dispersion, nonlinearities due to inelasticity and inhomogeneity, strength and delamination of coatings and surfaces. By benchmarking sophisticated numerical simulations against these results, it is possible to establish or update material constitutive models, which are of paramount importance for the design of devices exposed to interaction with particle beams in high energy accelerators such as the HL-LHC or FCC-hh.
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THPAF035	Single-Collimator Tune Shift Measurement of the Three-Stripe Collimator at the LHC	3036
	S. A. Antipov University of Chicago, Chicago, Illinois, USA D. Amorim, N. Biancacci, L.R. Carver, G. Mazzacano, A. Mereghetti, E. Métral, S. Redaelli, B. Salvant, D. Valuch CERN, Geneva, Switzerland
	Several options of low resistivity coating have been proposed for the collimator upgrade of the Large Hadron Collider. In order to study their effect on the beam dynamics a special collimator has been built and installed in the machine. Its jaws are coated with three different materials and can be moved transversely to selectively expose the beam to the chosen coating. We have measured the resistive wall tune shifts of each coating material and compared them with that of a standard Carbon Fibre Composite (CFC) collimator jaw. A resolution of the tune shift of the order of 10^-5 has been achieved in the measurement. The results show a significant reduction of the resistive wall tune shift with novel materials. The largest improvement is obtained with a 5 μm Molybdenum coating of a Molybdenum-Graphite jaw. The observed tune shifts show a good agreement with the impedance model and the bench impedance and resistivity measurements. Obtained results can be used to further improve the precision of the impedance model.
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Paper

Title

Page

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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MOPMF039

First Xenon-Xenon Collisions in the LHC

180

M. Schaumann, R. Alemany-Fernández, P. Baudrenghien, T. Bohl, C. Bracco, R. Bruce, N. Fuster-Martínez, M.A. Jebramcik, J.M. Jowett, T. Mertens, D. Mirarchi, S. Redaelli, B. Salvachua, M. Solfaroli, H. Timko, J. Wenninger
CERN, Geneva, Switzerland

In 2017, the CERN accelerator complex once again demonstrated its flexibility by producing beams of a new ion species, xenon, that were successfully injected into LHC. On 12 October, collisions of fully stripped xenon nuclei were recorded for the first time in the LHC at a centre-of-mass energy per colliding nucleon pair of 5.44 TeV. Physics data taking started 9.5 h after the first injection of xenon beams and lasted a total of 6 h. The integrated luminosity delivered to the four LHC experiments was sufficient that new physics results can be expected soon. We provide a general overview of this Xe-Xe pilot run before focussing on beam data at injection energy and at flat-top.

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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.

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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.

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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.

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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.

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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).

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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

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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.

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TUPAF029

Observation of Fast Losses in the LHC Operation in 2017

740

A.A. Gorzawski, N. Fuster-Martínez, S. Redaelli, C. Xu, C. Zamantzas
CERN, Geneva, Switzerland
R.B. Appleby
UMAN, Manchester, United Kingdom
H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom

Four diamond detectors that provide beam loss measurements with time resolution in the nanosecond range were added in the vicinity of the primary collimators of the Large Hadron Collider (LHC). This is a powerful diagnostic tool that provides the unique chance to measure bunch-by-bunch losses. The operation of the LHC in 2017 presented several unusual events of fast, high intensity beam losses, many of them captured by the diamond detectors in the betatron cleaning region. In this paper we review some of the relevant loss cases that were analyzed in the wider scope of determining the source of the instability generating these losses. We show few of the possible applications of this detectors in daily operations.

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TUPAF045

Studies for Future Fixed-Target Experiments at the LHC in the Framework of the CERN Physics Beyond Colliders Study

798

S. Redaelli, M. Ferro-Luzzi
CERN, Geneva, Switzerland
C. Hadjidakis
IN2P3-CNRS, Orsay, France

A study on prospects for Physics Beyond Colliders at CERN was launched in September 2016 to assess the capabilities of the existing accelerators complex. Among several other working groups, this initiative triggered the creation of a working group with the scope of studying a few specific proposals to perform fixed-target physics experiments at the Large Hadron Collider (LHC). This includes for example physics experiments with solid or gaseous internal targets, polarized gas targets, and experiments using bent-crystals for halo splitting from beam core for internal targets. The focus of the working group's activities is on the technical feasibility and on implications to the LHC ring. In this paper, the current status of the studies is presented and future plans are discussed.

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TUPAF046

Conceptual Design of a Collimation System for the CERN Super Proton Synchrotron

802

M. Patecki, A. Mereghetti, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

The Super Proton Synchrotron (SPS) is the last accelerator in the LHC Injectors Chain. Its performance is constantly being improved in frame of the LHC Injectors Upgrade (LIU) Project in order to prepare it for the future HL-LHC (High Luminosity LHC) operation. One of the LIU goals is to nearly double the intensity extracted from the SPS, up to 2.32×10¹¹ p/bunch. In recent years, nearly 10% of losses are observed for nominal intensity and LHC-type beams; they grow to about 20% for the intensity approaching the HL-LHC target. Beam losses imply activation and aging of the SPS hardware; the possibility to add a collimation system is being considered to mitigate this problem. In this paper we present studies of a collimation system design for the SPS. The concept is based on a primary horizontal collimator located in an available position with high enough dispersion, and a secondary collimator to intercept the particles leaking out from the primary collimator. Performance of the proposed collimation system is evaluated by means of numerical simulations.

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WEYGBE4

Low-Impedance Collimators for HL-LHC

1794

S. A. Antipov, N. Biancacci, R. Bruce, A. Mereghetti, D. Mirarchi, E. Métral, S. Redaelli, B. Salvant
CERN, Geneva, Switzerland
D. Amorim
Université Grenoble Alpes, Grenoble, France

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will double its beam intensity for the needs of High Energy Physics frontier. This increase requires a reduction of the machine's impedance to ensure the coherent stability of the beams until they are put in collision. A major part of the impedance is the resistive wall contribution of the collimators. To reduce this contribution several coating options have been proposed. We have studied numerically the effect of the novel coatings on the beam stability. The results show that a decrease of up to 30% of the machine impedance and a reduction of up to 120 A in the stabilizing octupole current threshold can be achieved by coating the secondary collimators with Molybdenum. Half of that improvement can be obtained by coating the jaws of a subset of four collimators identified as the highest contributors to machine impedance. The installation of this subset of low-impedance collimators is planned for the Long Shutdown 2 in 2019-2020.

Slides WEYGBE4 [5.719 MB]

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WEPAF080

Beam Size Measurements Based on Movable Quadrupolar Pick-ups

2028

A. Sounas, M. Gąsior, T. Lefèvre, A. Mereghetti, J. Olexa, S. Redaelli, G. Valentino
CERN, Geneva, Switzerland

Measurements with quadrupolar pick-ups (PU) have attracted particular interest as non-intercepting diagnostics for determining the transverse beam size. They are based on processing the signals of an electromagnetic PU for the extraction of the second-order moment, which contains information about the beam size. Despite the simplicity of the concept, quadrupololar measurements have always been highly challenging in reality. This comes from the fact that the quadrupolar moment constitutes only a very small part of the total PU signal dominated by the intensity and the position signals. Therefore, the beam size information can easily be lost due to small imperfections in the signal processing chain, such as asymmetries in the electronics and cables. In this paper, we present a new method for quadrupolar measurements using movable PUs. Through position and aperture scans, our technique minimizes the parasitic beam position signal and takes into account imperfections of the PU, cables and electronics, thus enabling an efficient auto-calibration of the measurement system. Preliminary studies, using collimators with embedded electrostatic PUs in the LHC at CERN, have shown very promising results.

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WEPMF071

Dynamic Testing and Characterization of Advanced Materials in a New Experiment at CERN HiRadMat Facility

2534

A. Bertarelli, C. Accettura, E. Berthomé, L. Bianchi, F. Carra, C. Fichera, M.I. Frankl, G. Gobbi, P. Grosclaude, M. Guinchard, A. Lechner, M. Pasquali, S. Redaelli, E. Rigutto, O. Sacristan De Frutos
CERN, Geneva, Switzerland
Ph. Bolz, P. Simon
GSI, Darmstadt, Germany
T.R. Furness
University of Huddersfield, Huddersfield, United Kingdom
J. Guardia Valenzuela
Universidad de Zaragoza, Zaragoza, Spain
P. Mollicone, M. Portelli
UoM, Msida, Malta

Funding: This work has received funding from the European Union's Horizon 2020 Research and Innovation programme under Grant Agreement No 730871.
An innovative and comprehensive experiment (named "Multimat") was successfully carried out at CERN HiRadMat facility on 18 different materials relevant for Collimators and Beam Intercepting Devices. Material samples, tested under high intensity proton pulses of 440 GeV/c, exceeding the energy density expected in HL-LHC, ranged from very light carbon foams to tungsten heavy alloys, including novel composites as graphite/carbides and metal/diamond without and with thin-film coatings. Experimental data were acquired relying on extensive integrated instrumentation (strain gauges, temperature sensors, radiation-hard camera) and on laser Doppler vibrometer. This allows investigating relatively unexplored and fundamental phenomena as dynamic strength, internal energy dispersion, nonlinearities due to inelasticity and inhomogeneity, strength and delamination of coatings and surfaces. By benchmarking sophisticated numerical simulations against these results, it is possible to establish or update material constitutive models, which are of paramount importance for the design of devices exposed to interaction with particle beams in high energy accelerators such as the HL-LHC or FCC-hh.

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THPAF035

Single-Collimator Tune Shift Measurement of the Three-Stripe Collimator at the LHC

3036

S. A. Antipov
University of Chicago, Chicago, Illinois, USA
D. Amorim, N. Biancacci, L.R. Carver, G. Mazzacano, A. Mereghetti, E. Métral, S. Redaelli, B. Salvant, D. Valuch
CERN, Geneva, Switzerland

Several options of low resistivity coating have been proposed for the collimator upgrade of the Large Hadron Collider. In order to study their effect on the beam dynamics a special collimator has been built and installed in the machine. Its jaws are coated with three different materials and can be moved transversely to selectively expose the beam to the chosen coating. We have measured the resistive wall tune shifts of each coating material and compared them with that of a standard Carbon Fibre Composite (CFC) collimator jaw. A resolution of the tune shift of the order of 10^-5 has been achieved in the measurement. The results show a significant reduction of the resistive wall tune shift with novel materials. The largest improvement is obtained with a 5 μm Molybdenum coating of a Molybdenum-Graphite jaw. The observed tune shifts show a good agreement with the impedance model and the bench impedance and resistivity measurements. Obtained results can be used to further improve the precision of the impedance model.

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