IPAC2019 - List of Keywords (collimation)

Paper	Title	Other Keywords	Page
MOPGW035	Coupling Impedance of the Collimator Without RF-Shields at the RCS in J-PARC	impedance, simulation, synchrotron, proton	163
	Y. Shobuda, J. Kamiya, K. Moriya, K. Okabe JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW035
About •	paper received ※ 28 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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MOPRB048	Collimation System Studies for the FCC-hh	proton, collider, simulation, hadron	669
	R. Bruce, A. Abramov, A. Bertarelli, M.I. Besana, F. Carra, F. Cerutti, M. Fiascaris, G. Gobbi, A.M. Krainer, A. Lechner, A. Mereghetti, D. Mirarchi, J. Molson, M. Pasquali, S. Redaelli, D. Schulte, E. Skordis, M. Varasteh Anvar CERN, Geneva, Switzerland A. Abramov JAI, Egham, Surrey, United Kingdom A. Faus-Golfe LAL, Orsay, France M. Serluca IN2P3-LAPP, Annecy-le-Vieux, France
	The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB048
About •	paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB050	Performance of the Collimation System During the 2018 Lead Ion Run at the Large Hadron Collider	simulation, heavy-ion, proton, hadron	677
	N. Fuster-Martínez, R. Bruce, J.M. Jowett, A. Mereghetti, D. Mirarchi, S. Redaelli CERN, Meyrin, Switzerland
	As part of the Large Hadron Collider (LHC) heavy-ion research programme, the last month of the 2018 LHC run was dedicated to Pb ion physics. Several heavy-ion runs have been performed since the start-up of the LHC. These runs are challenging for collimation, despite lower intensities, because of the degraded cleaning observed compared to protons. This is due to the differences of the interaction mechanisms in the collimators. Ions experience fragmentation and electromagnetic dissociation that result in a substantial flux of off-rigidity particles that escape the collimation system. In this paper, the collimation system performance and the experience gained during the 2018 Pb ion run are presented. The measured performance is compared with the expectation from the Sixtrack-FLUKA coupling simulations and the agreement discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB050
About •	paper received ※ 07 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019
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MOPRB051	Collimation System Upgrades for the High Luminosity Large Hadron Collider and Expected Cleaning Performance in Run 3	proton, hadron, collider, dipole	681
	A. Mereghetti, R. Bruce, N. Fuster-Martínez, D. Mirarchi, S. Redaelli CERN, Geneva, Switzerland
	In the framework of the High-Luminosity Large Hadron Collider project (HL-LHC), the LHC collimation system needs important upgrades to cope with the foreseen brighter beams. New collimation hardware will be installed in two phases, the first one during the LHC second Long Shutdown (LS2), in 2019-20, followed by a second phase starting in 2024 (LS3). This paper reviews the collimation upgrade plans for LS2, focused on a first impedance reduction of the system, through the installation of collimators based on new materials, and the improvement of collimation cleaning, achieved by adding new collimators in the cold dispersion suppressor regions. The performance of the new system in terms of cleaning inefficiency for proton and lead ion beams is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB051
About •	paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB055	First Partially Stripped Ions in the LHC (208Pb⁸¹⁺)	experiment, injection, factory, operation	689
	M. Schaumann, R. Alemany-Fernández, H. Bartosik, T. Bohl, R. Bruce, G.H. Hemelsoet, S. Hirlaender, J.M. Jowett, V. Kain, M.W. Krasny, J. Molson, G. Papotti, M. Solfaroli Camillocci, H. Timko, J. Wenninger CERN, Geneva, Switzerland
	The Gamma Factory initiative proposes to use partially stripped ion (PSI) beams as drivers of a new type of high intensity photon source. As part of the ongoing Physics Beyond Collider studies, initial beam tests with PSI beams have been executed at CERN. On 25 July 2018 lead ions with one remaining electron (208Pb⁸¹⁺) were injected and accelerated in the LHC for the first time. After establishing the injection and circulation of a few 208Pb⁸¹⁺ bunches, beam lifetimes of about 50 hours could be established at 6.5 TeV proton equivalent energy. This paper describes the setup of the beam tests and observations made.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB055
About •	paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB058	Collimation of Partially Stripped Ion Beams in the LHC	simulation, operation, collider, hadron	700
	A. Abramov, L.J. Nevay JAI, Egham, Surrey, United Kingdom R. Bruce, N. Fuster-Martínez, A.A. Gorzawski, M.W. Krasny, J. Molson, S. Redaelli, M. Schaumann CERN, Meyrin, Switzerland
	In the scope of the Physics Beyond Colliders studies, the Gamma Factory initiative proposes the use of partially stripped ions as a driver of a new type, high intensity photon source in CERN’s Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped 208-Pb-81+ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low. The worst losses were localised in the dispersion suppressor (DS) of the betatron-cleaning insertion. Analytic arguments and simulations show that the large losses are driven by the stripping of the remaining electron from the Pb nucleus by the primary collimators. The rising dispersion in the DS pushes the resulting off-rigidity, fully-stripped ions into the aperture of the superconducting magnets. In this study the measured loss maps are compared against results from simulations. Different mitigation strategies are outlined, including a dispersion suppressor (DS) collimator, crystal collimation or an orbit bump.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB058
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB059	Collimation of Heavy-Ion Beams in the HE-LHC	collider, proton, hadron, simulation	704
	A. Abramov, L.J. Nevay JAI, Egham, Surrey, United Kingdom R. Bruce, M.P. Crouch, N. Fuster-Martínez, A. Mereghetti, J. Molson, S. Redaelli CERN, Meyrin, Switzerland
	A design study for a future collider to be built in the LHC tunnel, the High-Energy Large Hadron Collider (HE-LHC), has been launched as part of the Future Circular Collider (FCC) study at CERN. It would provide proton collisions at a centre-of-mass energy of 27 TeV as well as collisions of heavy ions at the equivalent magnetic rigidity. HE-LHC is being designed under the stringent constraint of using the existing tunnel and therefore the resulting lattice and optics differ in layout and phase advance from the LHC. It is necessary to evaluate the performance of the collimation system for ion beams in HE-LHC in addition to proton beams. In the case of ion beams, the fragmentation and electromagnetic dissociation that relativistic heavy ions can undergo in collimators, as well as the unprecedented energy per nucleon of the HE-LHC, requires dedicated simulations. Results from a study of collimation efficiency for the nominal lead ion (Pb-82-208) beams performed with the SixTrack-FLUKA coupling framework are presented. These include loss maps with comparison against an estimated quench limit as well as detailed considerations of loss spikes in the superconducting aperture for critical sections of the machine such as the dispersion suppressors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB059
About •	paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPRB060	Simulating Novel Collimation Schemes for High-Luminosity LHC With Merlin++	proton, scattering, simulation, electron	708
	S.C. Tygier, R.B. Appleby UMAN, Manchester, United Kingdom R.J. Barlow, S. Rowan IIAA, Huddersfield, United Kingdom
	Due to the large stored beam energy in the HL-LHC new collimation technologies must be used to protect the machine. Active halo control of the proton beam halo with a Hollow Electron Lens can give a kick to protons at the edge of the beam without effecting the core. Various modes of operation are possible for example the electron lens can have a continuous current or it can be pulsed to different amplitudes for each passage of the proton beam. In this article we use Merlin++ simulations to show the performance of these modes for HL-LHC parameters. We also present recent simulations comparing scattering models in Merlin++.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB060
About •	paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB064	Precision Modelling of Energy Deposition in the LHC using BDSIM	simulation, proton, detector, beam-losses	723
	S.D. Walker, A. Abramov, S.T. Boogert, S.M. Gibson, L.J. Nevay, H. Pikhartova JAI, Egham, Surrey, United Kingdom
	A detailed model of the Large Hadron Collider (LHC) has been built using Beam Delivery Simulation (BDSIM) for studying beam loss patterns and is presented and discussed in this paper. BDSIM is a program which builds a Geant4 accelerator model from generic components bridging accelerator tracking routines and particle physics to seamlessly simulate the traversal of particles and any subsequent energy deposition in particle accelerators. The LHC model described here has been further refined with additional features to improve the accuracy of the model, including specific component geometries, tunnel geometry, and more. BDSIM has been extended so that more meaningful comparisons with other simulations and data can be made. Firstly, BDSIM can now record losses in the same way that SixTrack does: when a primary exceeds the limits of the aperture it is recorded as a loss. Secondly, by placing beam loss monitors (BLMs) within the BDSIM model and recording the simulated dose and energy deposition, it can be directly compared with real BLM data. These results are presented here and compared with SixTrack and BLM data from a typical fill in 2018.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB064
About •	paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPTS093	Ultra-High Vacuum Characterization of Molybdenum-Carbide Graphite for HL-LHC Collimators	vacuum, site, proton, collider	1078
	F. Carra, C. Accettura, A. Bertarelli, G. Bregliozzi, G. Cattenoz, S. Redaelli, M. Taborelli CERN, Meyrin, Switzerland M. Beghi POLIMI, Milano, Italy J. Guardia Valenzuela Universidad de Zaragoza, Zaragoza, Spain
	Funding: This work has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No. 730871. Research supported by the HL-LHC project In view of the High-Luminosity upgrade of the Large Hadron Collider (LHC) collimation system, a family of novel molybdenum-carbide graphite (MoGr) composites was developed to meet the challenging requirements of HL-LHC beam-halo collimation, in particular the electrical conductivity and thermo-mechanical performances. The Ultra-High Vacuum (UHV) behaviour of this material was extensively characterized to assess its compatibility with the accelerator’s specifications. The results presented in this paper correlate the outgassing behaviour with the microscopic features of MoGr compared to other graphite-based materials. Residual gas analysis (RGA) was exploited to optimize post-production treatments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS093
About •	paper received ※ 12 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUZZPLM1	Operational Results of LHC Collimator Alignment Using Machine Learning	alignment, injection, software, MMI	1208
	G. Azzopardi, A. Muscat, G. Valentino University of Malta, Information and Communication Technology, Msida, Malta S. Redaelli, B. Salvachua CERN, Geneva, Switzerland
	A complex collimation system is installed in the Large Hadron Collider to protect sensitive equipment from unavoidable beam losses. The collimators are positioned close to the beam in the form of a hierarchy, which is guaranteed by precisely aligning each collimator with a precision of a few tens of micrometers. During past years, collimator alignments were performed semi-automatically, such that collimation experts had to be present to oversee and control the alignment. In 2018, machine learning was introduced to develop a new fully-automatic alignment tool, which was used for collimator alignments throughout the year. This paper discusses how machine learning was used to automate the alignment, whilst focusing on the operational results obtained when testing the new software in the LHC. Automatically aligning the collimators decreased the alignment time at injection by a factor of three whilst maintaining the accuracy of the results. G.Valentino et al., "Semi-automatic beam-based LHC collimator alignment", PRSTAB, no.5, 2012.
	Slides TUZZPLM1 [6.060 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUZZPLM1
About •	paper received ※ 10 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUPRB019	Collimator Performance Study at the European XFEL	FEL, alignment, gun, operation	1717
	S. Liu, F. Brinker, W. Decking, L. Fröhlich, N. Golubeva, T. Wamsat, J. Wilgen DESY, Hamburg, Germany
	Beam halo collimation is of great importance for the high repetition rate operation at the European XFEL and for the future CW machines. At the European XFEL several different types of collimators are installed at different locations of the beam line, which include the gun collimators, the bunch compressor collimators, and the main and supplementary collimators in the collimation section. Beam halo measurements have been performed using the wire scanners downstream of the main linac, which show that large part of beam halo is collimated by the gun collimator. Remaining losses in the collimation section are mainly due to misalignment. Alignment using orbit bumps in the collimation section is performed and presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB019
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPTS043	SixTrack Version 5: Status and New Developments	simulation, electron, scattering, HOM	3200
	R. De Maria, J. Andersson, L. Field, M. Giovannozzi, P.D. Hermes, N. Hoimyr, G. Iadarola, S. Kostoglou, E.H. Maclean, E. McIntosh, A. Mereghetti, J. Molson, V.K.B. Olsen, D. Pellegrini, T. Persson, M. Schwinzerl CERN, Geneva, Switzerland B. Dalena, T. Pugnat CEA-IRFU, Gif-sur-Yvette, France K.N. Sjobak University of Oslo, Oslo, Norway I. Zacharov EPFL, Lausanne, Switzerland
	SixTrack Version 5 is a major SixTrack release that introduces new features, with improved integration of the existing ones, and extensive code restructuring. New features include dynamic-memory management, scattering-routine integration, a new initial-condition module, and reviewed post-processing methods. Existing features like on-line aperture checking and Fluka-coupling are now enabled by default. Extensive performance regression tests have been developed and deployed as part of the new-release generation. The new features of the tracking environment developed for the massive numerical simulations will be discussed as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS043
About •	paper received ※ 17 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPTS099	Passive Absorbers for Maximizing the Performance of the Mu2e-II Experiment	target, experiment, solenoid, proton	3345
	J. Manczak IFIC, Valencia, Spain J. Manczak Warsaw University, Warsaw, Poland D.V. Neuffer, D. Stratakis Fermilab, Batavia, Illinois, USA
	The Fermilab’s Mu2e experiment is designed to search for Charged Lepton Flavour Violation in direct, neutrinoless conversion of muon into electron in the presence of a nucleus’ electromagnetic field. Quantity, which is going to be observed is the ratio between the rate of the above BSM (Beyond Standard Model) reaction and the rate of the standard muon capture on the nucleus. The measurement precision is expected to reach up to 10^-17. Mu2e-II is the codename for the second phase of the experiment planned to run with the lower energy, higher intensity primary proton beam provided by PIP-II accelerator, currently under construction. The ionization cooling with a wedge absorber is introduced to Mu2e-II setup for potential increase in the number of low momentum muons reaching the target. The study is made into the position and size of the wedge inside the beamline using G4Beamline simulation framework. Results show an increase up to 12% for muons with momentum P below 30 MeV/c and 7% for muons with P<40 MeV/c when the beam is measured right after the wedge. Further studies are necessary to investigate how this gain can be delivered to the stopping target.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS099
About •	paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPMP027	Concept of Radiographic Complex Based on Ironless Pulsed Betatrons for Small-Angle Tomography	betatron, radiation, experiment, ion-source	3503
	O.A. Shamro, A.A. Chinin, V.A. Fomichev, Yu.P. Kuropatkin, V.I. Nizhegorodtsev, K.V. Savchenko, V.D. Selemir RFNC-VNIIEF, Sarov, Nizhniy Novgorod region, Russia
	The active research complexes intended for the radiography of dynamic objects with a high optical density are reviewed. The concept of a multi-beam radiographic complex for a small-angle tomography based on ironless pulsed betatrons is proposed. It is possible to use up to 18 compact facilities in a complex; they are located in three horizontal planes. The test object is placed in the explosion-proof chamber. Each facility consists of two typical units: an accelerator unit, and a unit of the electromagnet pulsed powering system. The output parameters of the facility are the maximum translucent capacity of 200 mm of the lead at 1 m from the betatron target, the resolution of less than 1 mm, the gamma-pulse full width at half maximum of 100 ns in a single frame mode, the gamma-pulse full width at half maximum of 150 ns in a three-frame mode. The complex will be able to obtain up to 54 frames in one hydrodynamic experiment at the operation of each facility in a three-frame mode. The complex is compact. Its diameter with a service area will be 20 m. Pat. 2515053 С1 RU МPK G03B 42/02. Yu.P. Kuropatkin, others. «Method of Radiograph. Image Form. of Fast Processes in Inhomogeneity and Radiograph. Complex for its Implementation», 2014.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP027
About •	paper received ※ 25 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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THPRB084	Run 2 Prompt Dose Distribution and Evolution at the Large Hadron Collider and Implications for Future Accelerator Operation	operation, radiation, proton, luminosity	4013
	O. Stein, K. Bilko, M. Brugger, R. Garcia Alia, F.J. Harden, Y. Kadi, A. Lechner, G. Lerner CERN, Geneva, Switzerland
	During the operation of the Large Hadron Collider (LHC) small fractions of beam particles are lost, creating prompt radiation fields in the accelerator tunnels. Exposed electronics and accelerator components show lifetime degradation and stochastic Single Event Effects (SEEs) which can lead to faults and downtime of the LHC. Close to the experiments the radiation levels scale nicely with the integrated luminosity since the luminosity debris is the major contributor for creating the radiation fields in this area of the LHC. In the collimation regions it was expected that the radiation fields scale with the integrated beam intensities since the beams are continuously cleaned from particles which exceed the accelerator’s acceptance. The analysis of radiation data shows that the dose measurements in the collimation regions normalised with the integrated beam intensities for 2016 and 2017 are comparable. Against expectations, the intensity normalised radiation datasets of 2018 in these regions differ significantly from the previous years. Especially in the betatron collimation region the radiation levels are up to a factor 3 higher. The radiation levels in the collimation regions correlate with the levelling of beta-star and the crossing angle in the high luminosity experiments ATLAS and CMS. These increased normalised doses have direct implications on the expected dose levels during future LHC operation, including the High-Luminosity LHC (HL-LHC) upgrade.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB084
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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Paper

Title

Other Keywords

Page

MOPGW035

Coupling Impedance of the Collimator Without RF-Shields at the RCS in J-PARC

impedance, simulation, synchrotron, proton

163

Y. Shobuda, J. Kamiya, K. Moriya, K. Okabe
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW035

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paper received ※ 28 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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MOPRB048

Collimation System Studies for the FCC-hh

proton, collider, simulation, hadron

669

R. Bruce, A. Abramov, A. Bertarelli, M.I. Besana, F. Carra, F. Cerutti, M. Fiascaris, G. Gobbi, A.M. Krainer, A. Lechner, A. Mereghetti, D. Mirarchi, J. Molson, M. Pasquali, S. Redaelli, D. Schulte, E. Skordis, M. Varasteh Anvar
CERN, Geneva, Switzerland
A. Abramov
JAI, Egham, Surrey, United Kingdom
A. Faus-Golfe
LAL, Orsay, France
M. Serluca
IN2P3-LAPP, Annecy-le-Vieux, France

The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB048

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paper received ※ 18 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB050

Performance of the Collimation System During the 2018 Lead Ion Run at the Large Hadron Collider

simulation, heavy-ion, proton, hadron

677

N. Fuster-Martínez, R. Bruce, J.M. Jowett, A. Mereghetti, D. Mirarchi, S. Redaelli
CERN, Meyrin, Switzerland

As part of the Large Hadron Collider (LHC) heavy-ion research programme, the last month of the 2018 LHC run was dedicated to Pb ion physics. Several heavy-ion runs have been performed since the start-up of the LHC. These runs are challenging for collimation, despite lower intensities, because of the degraded cleaning observed compared to protons. This is due to the differences of the interaction mechanisms in the collimators. Ions experience fragmentation and electromagnetic dissociation that result in a substantial flux of off-rigidity particles that escape the collimation system. In this paper, the collimation system performance and the experience gained during the 2018 Pb ion run are presented. The measured performance is compared with the expectation from the Sixtrack-FLUKA coupling simulations and the agreement discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB050

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paper received ※ 07 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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MOPRB051

Collimation System Upgrades for the High Luminosity Large Hadron Collider and Expected Cleaning Performance in Run 3

proton, hadron, collider, dipole

681

A. Mereghetti, R. Bruce, N. Fuster-Martínez, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

In the framework of the High-Luminosity Large Hadron Collider project (HL-LHC), the LHC collimation system needs important upgrades to cope with the foreseen brighter beams. New collimation hardware will be installed in two phases, the first one during the LHC second Long Shutdown (LS2), in 2019-20, followed by a second phase starting in 2024 (LS3). This paper reviews the collimation upgrade plans for LS2, focused on a first impedance reduction of the system, through the installation of collimators based on new materials, and the improvement of collimation cleaning, achieved by adding new collimators in the cold dispersion suppressor regions. The performance of the new system in terms of cleaning inefficiency for proton and lead ion beams is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB051

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paper received ※ 06 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB055

First Partially Stripped Ions in the LHC (208Pb⁸¹⁺)

experiment, injection, factory, operation

689

M. Schaumann, R. Alemany-Fernández, H. Bartosik, T. Bohl, R. Bruce, G.H. Hemelsoet, S. Hirlaender, J.M. Jowett, V. Kain, M.W. Krasny, J. Molson, G. Papotti, M. Solfaroli Camillocci, H. Timko, J. Wenninger
CERN, Geneva, Switzerland

The Gamma Factory initiative proposes to use partially stripped ion (PSI) beams as drivers of a new type of high intensity photon source. As part of the ongoing Physics Beyond Collider studies, initial beam tests with PSI beams have been executed at CERN. On 25 July 2018 lead ions with one remaining electron (208Pb⁸¹⁺) were injected and accelerated in the LHC for the first time. After establishing the injection and circulation of a few 208Pb⁸¹⁺ bunches, beam lifetimes of about 50 hours could be established at 6.5 TeV proton equivalent energy. This paper describes the setup of the beam tests and observations made.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB055

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paper received ※ 29 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB058

Collimation of Partially Stripped Ion Beams in the LHC

simulation, operation, collider, hadron

700

A. Abramov, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
R. Bruce, N. Fuster-Martínez, A.A. Gorzawski, M.W. Krasny, J. Molson, S. Redaelli, M. Schaumann
CERN, Meyrin, Switzerland

In the scope of the Physics Beyond Colliders studies, the Gamma Factory initiative proposes the use of partially stripped ions as a driver of a new type, high intensity photon source in CERN’s Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped 208-Pb-81+ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low. The worst losses were localised in the dispersion suppressor (DS) of the betatron-cleaning insertion. Analytic arguments and simulations show that the large losses are driven by the stripping of the remaining electron from the Pb nucleus by the primary collimators. The rising dispersion in the DS pushes the resulting off-rigidity, fully-stripped ions into the aperture of the superconducting magnets. In this study the measured loss maps are compared against results from simulations. Different mitigation strategies are outlined, including a dispersion suppressor (DS) collimator, crystal collimation or an orbit bump.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB058

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paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB059

Collimation of Heavy-Ion Beams in the HE-LHC

collider, proton, hadron, simulation

704

A. Abramov, L.J. Nevay
JAI, Egham, Surrey, United Kingdom
R. Bruce, M.P. Crouch, N. Fuster-Martínez, A. Mereghetti, J. Molson, S. Redaelli
CERN, Meyrin, Switzerland

A design study for a future collider to be built in the LHC tunnel, the High-Energy Large Hadron Collider (HE-LHC), has been launched as part of the Future Circular Collider (FCC) study at CERN. It would provide proton collisions at a centre-of-mass energy of 27 TeV as well as collisions of heavy ions at the equivalent magnetic rigidity. HE-LHC is being designed under the stringent constraint of using the existing tunnel and therefore the resulting lattice and optics differ in layout and phase advance from the LHC. It is necessary to evaluate the performance of the collimation system for ion beams in HE-LHC in addition to proton beams. In the case of ion beams, the fragmentation and electromagnetic dissociation that relativistic heavy ions can undergo in collimators, as well as the unprecedented energy per nucleon of the HE-LHC, requires dedicated simulations. Results from a study of collimation efficiency for the nominal lead ion (Pb-82-208) beams performed with the SixTrack-FLUKA coupling framework are presented. These include loss maps with comparison against an estimated quench limit as well as detailed considerations of loss spikes in the superconducting aperture for critical sections of the machine such as the dispersion suppressors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB059

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paper received ※ 18 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPRB060

Simulating Novel Collimation Schemes for High-Luminosity LHC With Merlin++

proton, scattering, simulation, electron

708

S.C. Tygier, R.B. Appleby
UMAN, Manchester, United Kingdom
R.J. Barlow, S. Rowan
IIAA, Huddersfield, United Kingdom

Due to the large stored beam energy in the HL-LHC new collimation technologies must be used to protect the machine. Active halo control of the proton beam halo with a Hollow Electron Lens can give a kick to protons at the edge of the beam without effecting the core. Various modes of operation are possible for example the electron lens can have a continuous current or it can be pulsed to different amplitudes for each passage of the proton beam. In this article we use Merlin++ simulations to show the performance of these modes for HL-LHC parameters. We also present recent simulations comparing scattering models in Merlin++.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB060

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paper received ※ 08 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB064

Precision Modelling of Energy Deposition in the LHC using BDSIM

simulation, proton, detector, beam-losses

723

S.D. Walker, A. Abramov, S.T. Boogert, S.M. Gibson, L.J. Nevay, H. Pikhartova
JAI, Egham, Surrey, United Kingdom

A detailed model of the Large Hadron Collider (LHC) has been built using Beam Delivery Simulation (BDSIM) for studying beam loss patterns and is presented and discussed in this paper. BDSIM is a program which builds a Geant4 accelerator model from generic components bridging accelerator tracking routines and particle physics to seamlessly simulate the traversal of particles and any subsequent energy deposition in particle accelerators. The LHC model described here has been further refined with additional features to improve the accuracy of the model, including specific component geometries, tunnel geometry, and more. BDSIM has been extended so that more meaningful comparisons with other simulations and data can be made. Firstly, BDSIM can now record losses in the same way that SixTrack does: when a primary exceeds the limits of the aperture it is recorded as a loss. Secondly, by placing beam loss monitors (BLMs) within the BDSIM model and recording the simulated dose and energy deposition, it can be directly compared with real BLM data. These results are presented here and compared with SixTrack and BLM data from a typical fill in 2018.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB064

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paper received ※ 15 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPTS093

Ultra-High Vacuum Characterization of Molybdenum-Carbide Graphite for HL-LHC Collimators

vacuum, site, proton, collider

1078

F. Carra, C. Accettura, A. Bertarelli, G. Bregliozzi, G. Cattenoz, S. Redaelli, M. Taborelli
CERN, Meyrin, Switzerland
M. Beghi
POLIMI, Milano, Italy
J. Guardia Valenzuela
Universidad de Zaragoza, Zaragoza, Spain

Funding: This work has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No. 730871. Research supported by the HL-LHC project
In view of the High-Luminosity upgrade of the Large Hadron Collider (LHC) collimation system, a family of novel molybdenum-carbide graphite (MoGr) composites was developed to meet the challenging requirements of HL-LHC beam-halo collimation, in particular the electrical conductivity and thermo-mechanical performances. The Ultra-High Vacuum (UHV) behaviour of this material was extensively characterized to assess its compatibility with the accelerator’s specifications. The results presented in this paper correlate the outgassing behaviour with the microscopic features of MoGr compared to other graphite-based materials. Residual gas analysis (RGA) was exploited to optimize post-production treatments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS093

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paper received ※ 12 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUZZPLM1

Operational Results of LHC Collimator Alignment Using Machine Learning

alignment, injection, software, MMI

1208

G. Azzopardi, A. Muscat, G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta
S. Redaelli, B. Salvachua
CERN, Geneva, Switzerland

A complex collimation system is installed in the Large Hadron Collider to protect sensitive equipment from unavoidable beam losses. The collimators are positioned close to the beam in the form of a hierarchy, which is guaranteed by precisely aligning each collimator with a precision of a few tens of micrometers. During past years, collimator alignments were performed semi-automatically*, such that collimation experts had to be present to oversee and control the alignment. In 2018, machine learning was introduced to develop a new fully-automatic alignment tool, which was used for collimator alignments throughout the year. This paper discusses how machine learning was used to automate the alignment, whilst focusing on the operational results obtained when testing the new software in the LHC. Automatically aligning the collimators decreased the alignment time at injection by a factor of three whilst maintaining the accuracy of the results.
*G.Valentino et al., "Semi-automatic beam-based LHC collimator alignment", PRSTAB, no.5, 2012.

Slides TUZZPLM1 [6.060 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUZZPLM1

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paper received ※ 10 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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TUPRB019

Collimator Performance Study at the European XFEL

FEL, alignment, gun, operation

1717

S. Liu, F. Brinker, W. Decking, L. Fröhlich, N. Golubeva, T. Wamsat, J. Wilgen
DESY, Hamburg, Germany

Beam halo collimation is of great importance for the high repetition rate operation at the European XFEL and for the future CW machines. At the European XFEL several different types of collimators are installed at different locations of the beam line, which include the gun collimators, the bunch compressor collimators, and the main and supplementary collimators in the collimation section. Beam halo measurements have been performed using the wire scanners downstream of the main linac, which show that large part of beam halo is collimated by the gun collimator. Remaining losses in the collimation section are mainly due to misalignment. Alignment using orbit bumps in the collimation section is performed and presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB019

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS043

SixTrack Version 5: Status and New Developments

simulation, electron, scattering, HOM

3200

R. De Maria, J. Andersson, L. Field, M. Giovannozzi, P.D. Hermes, N. Hoimyr, G. Iadarola, S. Kostoglou, E.H. Maclean, E. McIntosh, A. Mereghetti, J. Molson, V.K.B. Olsen, D. Pellegrini, T. Persson, M. Schwinzerl
CERN, Geneva, Switzerland
B. Dalena, T. Pugnat
CEA-IRFU, Gif-sur-Yvette, France
K.N. Sjobak
University of Oslo, Oslo, Norway
I. Zacharov
EPFL, Lausanne, Switzerland

SixTrack Version 5 is a major SixTrack release that introduces new features, with improved integration of the existing ones, and extensive code restructuring. New features include dynamic-memory management, scattering-routine integration, a new initial-condition module, and reviewed post-processing methods. Existing features like on-line aperture checking and Fluka-coupling are now enabled by default. Extensive performance regression tests have been developed and deployed as part of the new-release generation. The new features of the tracking environment developed for the massive numerical simulations will be discussed as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS043

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paper received ※ 17 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEPTS099

Passive Absorbers for Maximizing the Performance of the Mu2e-II Experiment

target, experiment, solenoid, proton

3345

J. Manczak
IFIC, Valencia, Spain
J. Manczak
Warsaw University, Warsaw, Poland
D.V. Neuffer, D. Stratakis
Fermilab, Batavia, Illinois, USA

The Fermilab’s Mu2e experiment is designed to search for Charged Lepton Flavour Violation in direct, neutrinoless conversion of muon into electron in the presence of a nucleus’ electromagnetic field. Quantity, which is going to be observed is the ratio between the rate of the above BSM (Beyond Standard Model) reaction and the rate of the standard muon capture on the nucleus. The measurement precision is expected to reach up to 10^-17. Mu2e-II is the codename for the second phase of the experiment planned to run with the lower energy, higher intensity primary proton beam provided by PIP-II accelerator, currently under construction. The ionization cooling with a wedge absorber is introduced to Mu2e-II setup for potential increase in the number of low momentum muons reaching the target. The study is made into the position and size of the wedge inside the beamline using G4Beamline simulation framework. Results show an increase up to 12% for muons with momentum P below 30 MeV/c and 7% for muons with P<40 MeV/c when the beam is measured right after the wedge. Further studies are necessary to investigate how this gain can be delivered to the stopping target.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS099

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paper received ※ 13 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPMP027

Concept of Radiographic Complex Based on Ironless Pulsed Betatrons for Small-Angle Tomography

betatron, radiation, experiment, ion-source

3503

O.A. Shamro, A.A. Chinin, V.A. Fomichev, Yu.P. Kuropatkin, V.I. Nizhegorodtsev, K.V. Savchenko, V.D. Selemir
RFNC-VNIIEF, Sarov, Nizhniy Novgorod region, Russia

The active research complexes intended for the radiography of dynamic objects with a high optical density are reviewed. The concept of a multi-beam radiographic complex for a small-angle tomography based on ironless pulsed betatrons is proposed*. It is possible to use up to 18 compact facilities in a complex; they are located in three horizontal planes. The test object is placed in the explosion-proof chamber. Each facility consists of two typical units: an accelerator unit, and a unit of the electromagnet pulsed powering system. The output parameters of the facility are the maximum translucent capacity of 200 mm of the lead at 1 m from the betatron target, the resolution of less than 1 mm, the gamma-pulse full width at half maximum of 100 ns in a single frame mode, the gamma-pulse full width at half maximum of 150 ns in a three-frame mode. The complex will be able to obtain up to 54 frames in one hydrodynamic experiment at the operation of each facility in a three-frame mode. The complex is compact. Its diameter with a service area will be 20 m.
* Pat. 2515053 С1 RU МPK G03B 42/02. Yu.P. Kuropatkin, others. «Method of Radiograph. Image Form. of Fast Processes in Inhomogeneity and Radiograph. Complex for its Implementation», 2014.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP027

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paper received ※ 25 April 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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THPRB084

Run 2 Prompt Dose Distribution and Evolution at the Large Hadron Collider and Implications for Future Accelerator Operation

operation, radiation, proton, luminosity

4013

O. Stein, K. Bilko, M. Brugger, R. Garcia Alia, F.J. Harden, Y. Kadi, A. Lechner, G. Lerner
CERN, Geneva, Switzerland

During the operation of the Large Hadron Collider (LHC) small fractions of beam particles are lost, creating prompt radiation fields in the accelerator tunnels. Exposed electronics and accelerator components show lifetime degradation and stochastic Single Event Effects (SEEs) which can lead to faults and downtime of the LHC. Close to the experiments the radiation levels scale nicely with the integrated luminosity since the luminosity debris is the major contributor for creating the radiation fields in this area of the LHC. In the collimation regions it was expected that the radiation fields scale with the integrated beam intensities since the beams are continuously cleaned from particles which exceed the accelerator’s acceptance. The analysis of radiation data shows that the dose measurements in the collimation regions normalised with the integrated beam intensities for 2016 and 2017 are comparable. Against expectations, the intensity normalised radiation datasets of 2018 in these regions differ significantly from the previous years. Especially in the betatron collimation region the radiation levels are up to a factor 3 higher. The radiation levels in the collimation regions correlate with the levelling of beta-star and the crossing angle in the high luminosity experiments ATLAS and CMS. These increased normalised doses have direct implications on the expected dose levels during future LHC operation, including the High-Luminosity LHC (HL-LHC) upgrade.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB084

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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