IPAC2021 - Classification: MC1: Circular and Linear Colliders / A01 Hadron Colliders

Paper	Title	Page
MOPAB001	Power Deposition in Superconducting Dispersion Suppressor Magnets Downstream of the Betatron Cleaning Insertion for HL-LHC	37
	A. Waets, C. Bahamonde Castro, E. Belli, R. Bruce, N. Fuster-Martínez, A. Lechner, A. Mereghetti, S. Redaelli, M. Sabaté-Gilarte, E. Skordis CERN, Meyrin, Switzerland
	Funding: Research supported by the HL-LHC project The power deposited in dispersion suppressor magnets downstream of the Large Hadron Collider (LHC) betatron cleaning insertion is governed by off-momentum particles scattered out of the primary collimators. In order to mitigate the risk of magnet quenches during periods of short beam lifetime in future High-Luminosity (HL-LHC) operation, new dispersion suppressor (DS) collimators are considered for installation (one per beam). In this paper, we present FLUKA simulations for both protons and Pb ions at 7 TeV, predicting the power deposition in the DS magnets, including the new higher-field dipoles 11T which are needed to integrate the collimator in the cold region next to the cleaning insertion. The simulated power deposition levels for the adopted HL-LHC collimator configuration and settings are used to assess the quench margin by comparison with the present estimated quench levels.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB001
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 16 August 2021
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MOPAB003	Machine Learning Analysis of Electron Cooler Operation for RHIC	45
	X. Gu, A.V. Fedotov, D. Kayran BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. A regression machine learning algorithm was applied to analyze the operation data of RHIC with electron cooler LEReC during the 2020 physics run. After constructing a black-box surrogate model from the XGBoost algorithm and plotting their partial dependency plots for different operation parameters, we can find the effects of an individual parameter on the RHIC luminosity and optimize it accordingly offline.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB003
About •	paper received ※ 14 May 2021 paper accepted ※ 25 May 2021 issue date ※ 11 August 2021
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MOPAB004	JSPEC - A Simulation Program for IBS and Electron Cooling	49
	H. Zhang, S.V. Benson, M.W. Bruker, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Intrabeam scattering is an important collective effect that can deteriorate the properties of a high-intensity beam, and electron cooling is a method to mitigate the IBS effect. JSPEC (JLab Simulation Package for Electron Cooling) is an open-source program developed at Jefferson Lab, which simulates the evolution of the ion beam under the IBS and/or the electron cooling effect. JSPEC has been benchmarked with BETACOOL and experimental data. In this report, we will introduce the features of JSPEC, including the friction force calculation, the IBS expansion rate and electron cooling rate calculation, and the beam-dynamic simulations for the electron cooling process; explain how to set up the simulations in JSPEC; and demonstrate the benchmarking results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB004
About •	paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 27 August 2021
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MOPAB005	Studies for an LHC Pilot Run with Oxygen Beams	53
	R. Bruce, R. Alemany-Fernández, H. Bartosik, M.A. Jebramcik, J.M. Jowett, M. Schaumann CERN, Geneva, Switzerland
	Motivated by the study of collective effects in small systems with oxygen-oxygen (O-O) collisions, and improvements to the understanding of high-energy cosmic ray interactions from proton-oxygen (p-O) collisions, a short LHC oxygen run during Run 3 has been proposed. This article presents estimates for the obtainable luminosity performance in these two running modes based on simulations of a typical fill. The requested integrated luminosity, projected beam conditions, data-taking and commissioning times are considered and a running scenario is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB005
About •	paper received ※ 17 May 2021 paper accepted ※ 25 May 2021 issue date ※ 19 August 2021
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MOPAB007	Prospect for Interaction Region Local Coupling Correction in the LHC Run 3	61
	F. Soubelet, T.H.B. Persson, R. Tomás García CERN, Geneva, Switzerland O. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) and CERN. Successful operation of large scale particle accelerators depends on the precise correction of unavoidable magnet field or alignment errors present in the machine. In the LHC Run 2, local linear coupling in the Interaction Regions (IR) has been proven to have a severe impact on beam size and hence the luminosity - up to a 50% decrease -, making its handling a target for Run 3 and High Luminosity LHC (HL-LHC). However, current measurement methods are not optimised for local IR coupling. In this contribution, an approach to accurately minimise IR local coupling based on correlated external variables such as the \|C-\| is proposed. The validity of the method is demonstrated through simulations and benchmarked against theoretical values, such as Resonance Driving Terms (RDTs) and Ripken parameters.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB007
About •	paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 19 August 2021
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MOPAB008	Exploiting the Beam-Beam Wire Demonstrators in the Next LHC Run 3	65
	A. Poyet Université Grenoble Alpes, Grenoble, France S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, A. Rossi, G. Sterbini CERN, Geneva, Switzerland K. Skoufaris University of Crete, Heraklion, Crete, Greece
	After the successful experiments performed during the LHC Run 2 with the Beam-Beam Wire demonstrators installed, on Beam 2, in the frame of the HL-LHC project, two of the four wire demonstrators were moved to Beam 1. The objective is to gain operational experience with the wire compensation also on that beam and therefore fully exploit the demonstrators’ potential. This paper proposes a numerical validation of the wire implementation using Run 3 scenarios and explores the optimization of those devices in that respect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB008
About •	paper received ※ 17 May 2021 paper accepted ※ 24 May 2021 issue date ※ 11 August 2021
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MOPAB009	Review of the Fixed Target Operation at RHIC in 2020	69
	C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. As part of the Beam Energy Scan (BES) physics program, RHIC operated in Fixed Target mode at various beam energies in 2020. The fixed target experiment, achieved by scraping the beam halo of the circulating beam on a gold ring inserted in the beam pipe upstream of the experimental detectors, extends the range of the center-of-mass energy for BES. The machine configuration, control of rates, and results of the fixed target experiment operation in 2020 will be presented in this report.
	Poster MOPAB009 [2.913 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB009
About •	paper received ※ 16 May 2021 paper accepted ※ 17 August 2021 issue date ※ 23 August 2021
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MOPAB010	RHIC Beam Energy Scan Operation with Electron Cooling in 2020	72
	C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. RHIC provided Au-Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as a part of the Beam Energy Scan II experiment. The operational experience at these energies will be reported with emphasis on their unique features. These unique features include the addition of a third harmonic RF system to enable a large longitudinal acceptance at 5.75 GeV/nucleon, the application of additional lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling with an RF-accelerated bunched electron beam.
	Poster MOPAB010 [3.523 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB010
About •	paper received ※ 17 May 2021 paper accepted ※ 29 July 2021 issue date ※ 10 August 2021
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MOPAB012	Energy Deposition Study of the CERN HL-LHC Optics v1.5 in the ATLAS and CMS Insertions	76
	M. Sabaté-Gilarte, F. Cerutti CERN, Meyrin, Switzerland
	Funding: Research supported by the HL-LHC project The High Luminosity Large Hadron Collider (HL-LHC) is the approved CERN project aiming at further increasing the integrated luminosity of the LHC by a factor 10. As such, it implies a complete redesign of the experimental high-luminosity insertions of ATLAS and CMS. The progressive evolution of the new layout and optics requires a continuous analysis of the radiation environment, to which magnets and other equipment are exposed to. This is assured by means of Monte Carlo simulations of the collision debris on the evolving machine model. The latter featured several developments, such as the explicit inclusion of the cold protection diodes of the final focusing circuits as well as the crab cavities cryomodule. This work presents the most updated characterization of the radiation field with FLUKA and its impact in the insertion region and the dispersion suppressor of Point 1 and 5, for the HL-LHC optics v1.5 released in 2019. Various optimization and mitigation studies are highlighted, providing key information for maximizing the lifetime of new and present magnets.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB012
About •	paper received ※ 18 May 2021 paper accepted ※ 25 May 2021 issue date ※ 21 August 2021
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MOPAB013	Radiation to Electronics Impact on CERN LHC Operation: Run 2 Overview and HL-LHC Outlook	80
	Y.Q. Aguiar, A. Apollonio, F. Cerutti, S. Danzeca, R. García Alía, G. Lerner, D. Prelipcean, M. Sabaté-Gilarte CERN, Geneva 23, Switzerland
	Funding: Research supported by the HL-LHC project After the mitigation measures implemented during Run 1 (2010-2012) and Long Shutdown 1 (LS1, 2013-2014), the number of equipment failures due to radiation effects on electronics (R2E) leading to LHC beam dumps and/or machine downtime has been sufficiently low as to yield a minor impact on the accelerator performance. During Run 2 (2015-2018) the R2E related failures per unit of integrated luminosity remained below the target value of 0.5 events/fb-1, with the sole exception of the 2015 run during which the machine commissioning took place. However, during 2018, an increase in the failure rate was observed, linked to the increased radiation levels in the dispersion suppressors of the ATLAS and CMS experimental insertions, significantly affecting the Quench Protection System located underneath the superconducting magnets in the tunnel. This work provides an overview of the Run 2 R2E events during LHC proton-proton operation, putting them in the context of the related radiation levels and equipment sensitivity, and providing an outlook for Run 3 and HL-LHC operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB013
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 23 August 2021
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MOPAB014	First High Spin-Flip Efficiency for High Energy Polarized Protons	84
	H. Huang, J. Kewisch, C. Liu, A. Marusic, W. Meng, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, T. Roser BNL, Upton, 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 order to minimize the systematic errors for the Relativistic Heavy Ion Collider (RHIC) spin physics experiments, flipping the spin of each bunch of protons during the stores is needed. Experiments done with single RF magnet at energies less than 2 GeV have demonstrated a spin-flip efficiency over 99%. At high energy colliders with Siberian snakes, a single magnet spin flipper does not work because of the large spin tune spread and the generation of multiple, overlapping resonances. Over past decade, RHIC spin flipper design has evolved and a sophisticated spin flipper, constructed of nine-dipole magnets, was developed to flip the spin in RHIC. A special optics choice was also used to make the spin tune spread very small. In recent experiment, 97% spin-flip efficiency was measured at both 24 and 255 GeV for the first time. The results show that efficient spin flipping can be achieved at high energies.
	Poster MOPAB014 [0.984 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB014
About •	paper received ※ 16 May 2021 paper accepted ※ 08 June 2021 issue date ※ 20 August 2021
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MOPAB017	Influence of Injection Kicker Post-pulses on Storage of Ion Stack in NICA Collider	93
	E. Syresin, A. Tuzikov, N.O. Zagibin JINR, Dubna, Moscow Region, Russia
	The peculiarity of the injection kicker power supply in NICA collider is related to same post pulse of the magnetic field which is appeared after a regular injection pulse. The magnetic field of this post pulse became to an increase of the stack ion angle spread during each injection cycle. When the stack ion angles reaches the acceptance angle the ions are lost in the collider. Influence of the injection kicker post pulse on the storage of the ion stack is considered in this paper in presence of the electron cooling and ion electron recombination losses.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB017
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 13 August 2021
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MOPAB019	Possible Application of Round-to-Flat Hadron Beam Creation Using 3rd Order Coupling Resonances for the Electron-Ion Collider	99
	J. Kallestrup PSI, Villigen PSI, Switzerland X. Gu BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. An Electron-Ion Collider (EIC) is planned to be built in Brookhaven National Laboratory with the contribution from Jefferson National Laboratory. To have a high luminosity, both the EIC ion bunch and the EIC electron bunch are designed to be flat during their collision. The existing injector source provides a round beam of width 2.5 um rad transverse emittances. In this paper we investigate the option of dynamically crossing the 2Qx-Qy coupling resonance in order to create a flat-beam with emittance ratio Ex/Ey of up to 4. Furthermore, we explore the possibility of using a pulsed- or AC skew sextupole magnets to achieve a similar effect. Using one of these methods for flat beam creation will help lower the ion beam cooling time.
	Poster MOPAB019 [0.323 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB019
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 24 August 2021
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MOPAB022	FailSim: A Numerical Toolbox for the Study of Fast Failures and Their Impact on Machine Protection at the CERN Large Hadron Collider	111
	C. Hernalsteens, G. Sterbini, O.K. Tuormaa, C. Wiesner, D. Wollmann CERN, Meyrin, Switzerland
	The High Luminosity LHC (HL-LHC) foresees to reach a nominal, levelled luminosity of 5·10³⁴ cm^-2 s⁻¹ through a higher beam brightness and by using new equipment, such as larger aperture final focusing quadrupole magnets. The HL-LHC upgrade has critical impacts on the machine protection strategy, as the stored beam energy reaches 700 MJ for each of the two beams. Some failure modes of the novel active superconducting magnet protection system of the inner triplet magnets, namely the Coupling-Loss Induced Quench (CLIQ) systems, have been identified as critical. This paper reports on FailSim, a Python-language framework developed to study the machine protection impact of failure cases and their proposed mitigation. It provides seamless integration of the successive phases required by the simulation studies, i.e., verifying the optics, preparing and running a MAD-X instance for multiple particle tracking, processing and analysing the simulation results and summarising them with the relevant plots to provide a solid estimate of the beam losses, their location and time evolution. The paper also presents and discusses the result of its application on the spurious discharge of a CLIQ unit.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB022
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 18 August 2021
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MOPAB023	Experimental Test of a New Method to Verify Retraction Margins Between Dump Absorbers and Tertiary Collimators at the LHC	115
	C. Wiesner, W. Bartmann, C. Bracco, R. Bruce, J. Molson, M. Schaumann, C. Staufenbiel, J.A. Uythoven, M. Valette, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Meyrin, Switzerland
	The protection of the tertiary collimators (TCTs) and the LHC triplet aperture in case of a so-called asynchronous beam dump relies on the correct retraction between the TCTs and the dump region absorbers. A new method to validate this retraction has been proposed, and a proof-of-principle experiment was performed at the LHC. The method uses a long orbit bump to mimic the change of the beam trajectory caused by an asynchronous firing of the extraction kickers. It can, thus, be performed with circulating beam. This paper reports on the performed beam measurements, compares them with expectations and discusses the potential benefits of the new method for machine protection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB023
About •	paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 24 August 2021
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MOPAB024	Efficient Coupling of Hydrodynamic and Energy-Deposition Codes for Hydrodynamic-Tunnelling Studies on High-Energy Particle Accelerators	119
	C. Wiesner, F. Carra, J. Kruse-Hansen, M. Masci, D. Wollmann CERN, Meyrin, Switzerland Y. Nie KIT, Karlsruhe, Germany
	The machine-protection evaluation of high-energy accelerators comprises the study of beyond-design failures, including the direct beam impact onto machine elements. In case of a direct impact, the nominal beam of the Large Hadron Collider (LHC) would penetrate more than 30 meters into a solid copper target. The penetration depth due to the time structure of the particle beam is, thus, significantly longer than predicted from purely static energy-deposition simulations with 7 TeV protons. This effect, known as hydrodynamic tunnelling, is caused by the beam-induced density depletion of the material at the target axis, which allows subsequent bunches to penetrate deeper into the target. Its proper simulation requires, therefore, to sequentially couple an energy-deposition code and a hydrodynamic code for the different target densities. This paper describes a method to efficiently couple the simulations codes Autodyn and FLUKA based on automatic density assignment and input file generation, and presents the results achieved for a sample case.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB024
About •	paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021
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MOPAB025	First Experiments with Accelerated Ion Beams in the Booster of NICA Accelerator Complex	123
	A.V. Butenko, V. Andreev, A.M. Bazanov, O.I. Brovko, D.E. Donets, A.V. Eliseev, I.V. Gorelyshev, A.V. Konstantinov, S.A. Kostromin, O.S. Kozlov, K.A. Levterov, A. Nesterov, A.V. Philippov, D.O. Ponkin, G.S. Sedykh, I.V. Shirikov, A.O. Sidorin, E. Syresin, A. Tuzikov, V. Volkov JINR/VBLHEP, Dubna, Moscow region, Russia N.N. Agapov, A.V. Alfeev, A.A. Baldin, A.A. Fateev, A.R. Galimov, B.V. Golovenskiy, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, A. Kirichenko, A.G. Kobets, S.A. Korovkin, V. Kosachev, A.D. Kovalenko, G. Kunchenko, I.N. Meshkov, V.A. Mikhailov, V.A. Monchinsky, D. Nikiforov, R.V. Pivin, S. Romanov, A.A. Shurygin, A.I. Sidorov, A.N. Svidetelev, G.V. Trubnikov, B. Vasilishin JINR, Dubna, Moscow Region, Russia G.A. Fatkin Cosylab Siberia, Novosibirsk, Russia
	The NICA accelerator complex in JINR consist of two linear injector chains, a 578 MeV/u superconducting (SC) Booster synchrotron, the existing SC synchrotron Nuclotron, and a new SC collider that has two storage rings. The construction of the facility is based on the Nuclotron technology of SC magnets with an iron yoke and hollow SC cable. Assembly of the Booster synchrotron was finished in autumn of 2020 and first machine Run and experiments with ion beams were successfully done in December 2020. The results of this Run are discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB025
About •	paper received ※ 16 May 2021 paper accepted ※ 07 September 2021 issue date ※ 15 August 2021
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MOPAB026	RHIC Delayed Abort Experiments	126
	M. Valette, D. Bruno, K.A. Drees, K.M. Hartmann, G. Heppner, K. Mernick, C. Mi, J.-L. Mi, R.J. Michnoff, J. Morris, F. Orsatti, E. Rydout, T. Samms, J. Sandberg, V. Schoefer, C. Schultheiss, T.C. Shrey, C. Theisen BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. For RHIC to operate at its top energy (100 GeV/n) while protecting the future sPHENIX detector, spontaneous and asynchronous firing of abort kicker modules (pre-fires) have to be avoided. A new triggering circuit for the abort kickers was implemented with relatively slow mechanical relays in series with the standard fast thyratron tubes. The relays prevents unwanted pre-fires during operation, but comes at the expense of a long latency - about 7 milliseconds - between the removal of beam permit and the actual firing of the abort kickers. Protection considerations of RHIC’s superconducting magnets forbid delaying energy extraction from the main dipoles and quadrupoles for too long after a quench. The beam has thus to circulate in both RHIc rings for a few milliseconds as the current in dipole and quadrupole circuit is being extracted. We present the results of delayed abort experiments conducted in July 2018 with the analysis of fast orbit and tune measurements and discuss the safety implications of this implementation for future RHIC operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB026
About •	paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 23 August 2021
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MOPAB027	Improving the Luminosity Burn-Off Estimate by Considering Single-Diffractive Effects	130
	F.F. Van der Veken, H. Burkhardt, M. Giovannozzi, V.K.B. Olsen CERN, Geneva, Switzerland
	Collisions in a high-luminosity collider result in a continuous burn-off of the circulating beams that is the dominant effect that reduces the instantaneous luminosity over time. In order to obtain a good estimate of the luminosity evolution, it is imperative to have an accurate understanding of the burn-off. Typically, this is calculated based on the inelastic cross-section, as it provides a direct estimate of the number of protons that participate in inelastic collisions, and are hence removed. Likewise, protons that participate in elastic collisions will remain in the machine acceptance, still contributing to luminosity. In between these two regimes lie diffractive collisions, for which the protons have a certain probability to remain in the machine acceptance. Recent developments of the SixTrack code allow it to interface with Pythia, thus allowing for more precise simulations to obtain a better estimate of the diffractive part of the cross-section. In this paper, we will mainly concentrate on slowly-drifting protons that are close to the acceptance limit, resulting from single-diffractive scattering.
	Poster MOPAB027 [1.193 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB027
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 11 August 2021
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MOPAB029	Burn-Off with Asymmetric Interaction Points	138
	R. Tomás García, I. Efthymiopoulos, G. Iadarola CERN, Geneva, Switzerland
	LHC can host above 2700 proton bunches per ring providing collisions in the ATLAS, CMS, LHCb and ALICE interaction points. ATLAS and CMS are placed symmetrically so that they feature the same colliding bunch pairs. However this is not the case for LHCb, hence introducing unwanted bunch-by-bunch variations of the bunch intensity as the physics fill evolves. We present first analytical derivations, numerical simulations and experimental data in different bunch train collision configurations.
	Poster MOPAB029 [1.502 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB029
About •	paper received ※ 13 May 2021 paper accepted ※ 25 May 2021 issue date ※ 27 August 2021
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WEXA01	Successful Crabbing of Proton Beams	2510
	R. Calaga CERN, Meyrin, Switzerland
	Funding: Research supported by the HL-LHC project and by the DOE and UK-STFC. Many future particle colliders require beam crabbing to recover the geometric luminosity loss from the non-zero crossing angle at the interaction point. A first demonstration experiment of crabbing with hadron beams was successfully carried out with high energy protons. This breakthrough result is fundamental to achieve the physics goals of the high luminosity LHC upgrade project (HL-LHC) and the future circular collider (FCC). The expected peak luminosity gain (related to collision rate) is 65% for HL-LHC, and even greater for the FCC. Novel beam physics experiments with proton beams in CERN’s Super Proton Synchrotron (SPS) were performed to demonstrate several critical aspects for the operation of crab cavities in the future HL-LHC including transparency with a pair of cavities, a full characterization of the cavity impedance with high beam currents and controlled emittance growth from crab cavity induced RF noise.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA01
About •	paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 24 August 2021
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WEXA02	Operational Electron Cooling in the Relativistic Heavy Ion Collider	2516
	A.V. Fedotov, K.A. Drees, W. Fischer, X. Gu, D. Kayran, J. Kewisch, C. Liu, K. Mernick, M.G. Minty, V. Schoefer, H. Zhao BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA02
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 31 August 2021
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WEXA05	Solving for Collider Beam Profiles from Luminosity Jitter with Ghost Imaging	2524
	D.F. Ratner, A. Chao SLAC, Menlo Park, California, USA
	Large accelerator facilities must balance the need to achieve user performance requirements while also maximizing delivery time. At the same time, accelerators have advanced data-acquisition systems that acquire synchronous data at high-rate from a large variety of diagnostics. Here we discuss the application of ghost-imaging (GI) to measure beam parameters, switching the emphasis from beam control to data collection: rather than intentionally manipulating the accelerator, we instead passively monitor jitter gathered over thousands to millions of events to reconstruct the target of interest. Passive monitoring during routine operation builds large data sets that can even deliver higher resolution than brief periodic scans, and can provide experiments with event-by-event information. In this presentation we briefly present applications of GI to light-sources, and then discuss a potential new application for colliders: measuring the transverse beam shapes at a collider’s interaction point to determine both the integrated luminosity and the spatial distribution of collision vertices.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA05
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 10 August 2021
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WEXA06	Study of Pb-Pb and Pb-p Collision Debris in the CERN LHC in View of HL-LHC Operation	2528
	M. Sabaté-Gilarte, R. Bruce, F. Cerutti, A. Lechner CERN, Meyrin, Switzerland
	Funding: Research supported by the HL-LHC project For the first time, a full characterization of the Pb-Pb and Pb-p collision debris as well as its impact in terms of energy deposition in the long straight section (LSS) of CERN’s Large Hadron Collider has been carried out. By means of Monte Carlo simulations with FLUKA, both inelastic nuclear interaction and electromagnetic dissociation were taken into account as source term for lead ion operation, while for Pb-p operation only nuclear interaction is of importance. The radiation exposure of detectors exclusively destined for ion beam runs is assessed, allowing drawing implications of their use. This work gave the opportunity for an unprecedented validation of simulation results against measurement of beam loss monitors (BLM) in the experimental LSS during ion operation. Pb-Pb operation refers to the 2018 ion run at 6.37 TeV per charge with a +160 microrad half crossing angle in the vertical plane at the ATLAS interaction point. Instead, Pb-p operation was benchmarked for the 2016 ion run at 6.5 TeV per charge with -140 microrad half crossing angle in the vertical plane at the same location.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA06
About •	paper received ※ 18 May 2021 paper accepted ※ 05 July 2021 issue date ※ 22 August 2021
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WEPAB026	Optics Measurements and Correction Plans for the HL-LHC	2656
	T.H.B. Persson, X. Buffat, F.S. Carlier, R. De Maria, J. Dilly, E. Fol, D. Gamba, H. Garcia Morales, A. García-Tabarés Valdivieso, M. Giovannozzi, M. Hofer, E.J. Høydalsvik, J. Keintzel, M. Le Garrec, E.H. Maclean, L. Malina, P.K. Skowroński, F. Soubelet, R. Tomás García, F.F. Van der Veken, A. Wegscheider, D.W. Wolf, L. van Riesen-Haupt CERN, Geneva, Switzerland J.M. Coello de Portugal PSI, Villigen PSI, Switzerland
	The High Luminosity LHC (HL-LHC) will require stringent optics correction to operate safely and deliver the design luminosity to the experiments. In order to achieve this, several new methods for optics correction have been developed. In this article, we outline some of these methods and we describe the envisioned strategy of how to use them in order to reach the challenging requirements of the HL-LHC physics program.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB026
About •	paper received ※ 17 May 2021 paper accepted ※ 27 July 2021 issue date ※ 30 August 2021
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WEPAB027	Optics Correction Strategy for Run 3 of the LHC	2660
	T.H.B. Persson, R. De Maria, J. Dilly, E. Fol, H. Garcia Morales, M. Hofer, E.J. Høydalsvik, J. Keintzel, M. Le Garrec, E.H. Maclean, L. Malina, F. Soubelet, R. Tomás García, A. Wegscheider, D.W. Wolf, L. van Riesen-Haupt CERN, Geneva, Switzerland J.F. Cardona UNAL, Bogota D.C, Colombia
	The Run 3 of the LHC will continue to provide new challenges for optics corrections. In order to succeed and go beyond what was achieved previously, several new methods to measure and correct the optics have been developed. In this article we describe these methods and outline the plans for the optics commissioning in 2022.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB027
About •	paper received ※ 17 May 2021 paper accepted ※ 12 July 2021 issue date ※ 11 August 2021
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WEPAB028	MAD-X for Future Accelerators	2664
	T.H.B. Persson, H. Burkhardt, L. Deniau, A. Latina, P.K. Skowroński CERN, Geneva, Switzerland
	The feasibility and performance of the future accelerators must, to a large extent, be predicted by simulation codes. This implies that simulation codes need to include effects that previously played a minor role. For example, in large electron machines like the FCC-ee the large energy variation along the ring requires that the magnets strength is adjusted to the beam energy at that location, normally referred to as tapering. In this article, we present new features implemented in the MAD-X code to enable and facilitate simulations of future colliders.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB028
About •	paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 27 August 2021
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WEPAB033	Lattice Design of the CEPC Collider Ring for a High Luminosity Scheme	2679
	Y. Wang, S. Bai, J. Gao, B. Wang, D. Wang, Y. Wei, J. Wu, C.H. Yu, J.Y. Zhai, Y. Zhang, Y.S. Zhu IHEP, Beijing, People’s Republic of China Y. Zhang University of Chinese Academy of Sciences, Beijing, People’s Republic of China
	A high luminosity scheme of the CEPC has been proposed aiming to increase the luminosity mainly at Higgs and Z modes. In this paper, the high luminosity scheme will be introduced briefly, including the beam parameters and RF staging. Then, the lattice design of the CEPC collider ring for the high luminosity scheme will be presented, including the bare lattice design and dynamic aperture optimization at Higgs energy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB033
About •	paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 27 August 2021
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THPAB001	Reaching the Sub Per Mil Level Coupling Corrections in the LHC	3752
	E.J. Høydalsvik, T.H.B. Persson CERN, Geneva, Switzerland
	The High Luminosity LHC (HL-LHC) is requiring sub per mil coupling correction, as defined by the closest tune approach. In this article, the current coupling correction strategy is analyzed in order to understand if it can robustly correct to these very low levels. The impact of realistic errors on the coupling correction is investigated with MAD-X simulations, including the influence of local coupling on the global coupling correction. Through simulations and measurements in the LHC, the effect of BPM noise on the coupling correction is analyzed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB001
About •	paper received ※ 11 May 2021 paper accepted ※ 28 July 2021 issue date ※ 23 August 2021
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THPAB172	Bunch Luminosity Variations in LHC Run 2	4094
	I. Efthymiopoulos, S.D. Fartoukh, G. Iadarola, N. Karastathis, S. Papadopoulou, Y. Papaphilippou CERN, Geneva, Switzerland
	The LHC is designed to collide intense bunches of protons with tightly defined conditions, aimed to maximize the delivered recorded integrated luminosity to the experiments. One of these conditions is the maximum level of bunch-to-bunch fluctuation in the luminosity, in particular when levelling at maximum acceptable event rate at the experiments. Analysis results of the bunch-to-bunch luminosity variations in LHC Run 2 are presented here. In particular, the observed correlations with the LHC filling pattern that can enhance the effects introducing bunch-dependent losses or emittance blow-up from injection to collisions are discussed. In Run 2 conditions, bunch-by-bunch luminosity fluctuations reached 10% at the start of collisions and gradually increased with time, without affecting the experiments as the luminosity was not levelled. Projections for Run 3 and HL-LHC operation are discussed along with envisaged mitigation measures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB172
About •	paper received ※ 18 May 2021 paper accepted ※ 19 July 2021 issue date ※ 23 August 2021
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Paper

Title

Page

Power Deposition in Superconducting Dispersion Suppressor Magnets Downstream of the Betatron Cleaning Insertion for HL-LHC

37

A. Waets, C. Bahamonde Castro, E. Belli, R. Bruce, N. Fuster-Martínez, A. Lechner, A. Mereghetti, S. Redaelli, M. Sabaté-Gilarte, E. Skordis
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project
The power deposited in dispersion suppressor magnets downstream of the Large Hadron Collider (LHC) betatron cleaning insertion is governed by off-momentum particles scattered out of the primary collimators. In order to mitigate the risk of magnet quenches during periods of short beam lifetime in future High-Luminosity (HL-LHC) operation, new dispersion suppressor (DS) collimators are considered for installation (one per beam). In this paper, we present FLUKA simulations for both protons and Pb ions at 7 TeV, predicting the power deposition in the DS magnets, including the new higher-field dipoles 11T which are needed to integrate the collimator in the cold region next to the cleaning insertion. The simulated power deposition levels for the adopted HL-LHC collimator configuration and settings are used to assess the quench margin by comparison with the present estimated quench levels.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB001

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 16 August 2021

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MOPAB003

Machine Learning Analysis of Electron Cooler Operation for RHIC

45

X. Gu, A.V. Fedotov, D. Kayran
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A regression machine learning algorithm was applied to analyze the operation data of RHIC with electron cooler LEReC during the 2020 physics run. After constructing a black-box surrogate model from the XGBoost algorithm and plotting their partial dependency plots for different operation parameters, we can find the effects of an individual parameter on the RHIC luminosity and optimize it accordingly offline.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB003

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paper received ※ 14 May 2021 paper accepted ※ 25 May 2021 issue date ※ 11 August 2021

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MOPAB004

JSPEC - A Simulation Program for IBS and Electron Cooling

49

H. Zhang, S.V. Benson, M.W. Bruker, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Intrabeam scattering is an important collective effect that can deteriorate the properties of a high-intensity beam, and electron cooling is a method to mitigate the IBS effect. JSPEC (JLab Simulation Package for Electron Cooling) is an open-source program developed at Jefferson Lab, which simulates the evolution of the ion beam under the IBS and/or the electron cooling effect. JSPEC has been benchmarked with BETACOOL and experimental data. In this report, we will introduce the features of JSPEC, including the friction force calculation, the IBS expansion rate and electron cooling rate calculation, and the beam-dynamic simulations for the electron cooling process; explain how to set up the simulations in JSPEC; and demonstrate the benchmarking results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB004

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paper received ※ 19 May 2021 paper accepted ※ 21 May 2021 issue date ※ 27 August 2021

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MOPAB005

Studies for an LHC Pilot Run with Oxygen Beams

53

R. Bruce, R. Alemany-Fernández, H. Bartosik, M.A. Jebramcik, J.M. Jowett, M. Schaumann
CERN, Geneva, Switzerland

Motivated by the study of collective effects in small systems with oxygen-oxygen (O-O) collisions, and improvements to the understanding of high-energy cosmic ray interactions from proton-oxygen (p-O) collisions, a short LHC oxygen run during Run 3 has been proposed. This article presents estimates for the obtainable luminosity performance in these two running modes based on simulations of a typical fill. The requested integrated luminosity, projected beam conditions, data-taking and commissioning times are considered and a running scenario is proposed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB005

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paper received ※ 17 May 2021 paper accepted ※ 25 May 2021 issue date ※ 19 August 2021

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MOPAB007

Prospect for Interaction Region Local Coupling Correction in the LHC Run 3

61

F. Soubelet, T.H.B. Persson, R. Tomás García
CERN, Geneva, Switzerland
O. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) and CERN.
Successful operation of large scale particle accelerators depends on the precise correction of unavoidable magnet field or alignment errors present in the machine. In the LHC Run 2, local linear coupling in the Interaction Regions (IR) has been proven to have a severe impact on beam size and hence the luminosity - up to a 50% decrease -, making its handling a target for Run 3 and High Luminosity LHC (HL-LHC). However, current measurement methods are not optimised for local IR coupling. In this contribution, an approach to accurately minimise IR local coupling based on correlated external variables such as the |C-| is proposed. The validity of the method is demonstrated through simulations and benchmarked against theoretical values, such as Resonance Driving Terms (RDTs) and Ripken parameters.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB007

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paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 19 August 2021

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MOPAB008

Exploiting the Beam-Beam Wire Demonstrators in the Next LHC Run 3

65

A. Poyet
Université Grenoble Alpes, Grenoble, France
S.D. Fartoukh, N. Karastathis, Y. Papaphilippou, A. Rossi, G. Sterbini
CERN, Geneva, Switzerland
K. Skoufaris
University of Crete, Heraklion, Crete, Greece

After the successful experiments performed during the LHC Run 2 with the Beam-Beam Wire demonstrators installed, on Beam 2, in the frame of the HL-LHC project, two of the four wire demonstrators were moved to Beam 1. The objective is to gain operational experience with the wire compensation also on that beam and therefore fully exploit the demonstrators’ potential. This paper proposes a numerical validation of the wire implementation using Run 3 scenarios and explores the optimization of those devices in that respect.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB008

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paper received ※ 17 May 2021 paper accepted ※ 24 May 2021 issue date ※ 11 August 2021

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MOPAB009

Review of the Fixed Target Operation at RHIC in 2020

69

C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
As part of the Beam Energy Scan (BES) physics program, RHIC operated in Fixed Target mode at various beam energies in 2020. The fixed target experiment, achieved by scraping the beam halo of the circulating beam on a gold ring inserted in the beam pipe upstream of the experimental detectors, extends the range of the center-of-mass energy for BES. The machine configuration, control of rates, and results of the fixed target experiment operation in 2020 will be presented in this report.

Poster MOPAB009 [2.913 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB009

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paper received ※ 16 May 2021 paper accepted ※ 17 August 2021 issue date ※ 23 August 2021

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MOPAB010

RHIC Beam Energy Scan Operation with Electron Cooling in 2020

72

C. Liu, P. Adams, E.N. Beebe, S. Binello, I. Blackler, M. Blaskiewicz, K.A. Brown, D. Bruno, B.D. Coe, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, K. Hock, H. Huang, R.L. Hulsart, T. Kanesue, D. Kayran, N.A. Kling, B. Lepore, Y. Luo, D. Maffei, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, J. Morris, C. Naylor, S. Nemesure, M. Okamura, I. Pinayev, S. Polizzo, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, P. Thieberger, M. Valette, A. Zaltsman, I. Zane, K. Zeno, W. Zhang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
RHIC provided Au-Au collisions at beam energies of 5.75 and 4.59 GeV/nucleon for the physics program in 2020 as a part of the Beam Energy Scan II experiment. The operational experience at these energies will be reported with emphasis on their unique features. These unique features include the addition of a third harmonic RF system to enable a large longitudinal acceptance at 5.75 GeV/nucleon, the application of additional lower frequency cavities for alleviating space charge effects, and the world-first operation of cooling with an RF-accelerated bunched electron beam.

Poster MOPAB010 [3.523 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB010

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paper received ※ 17 May 2021 paper accepted ※ 29 July 2021 issue date ※ 10 August 2021

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MOPAB012

Energy Deposition Study of the CERN HL-LHC Optics v1.5 in the ATLAS and CMS Insertions

76

M. Sabaté-Gilarte, F. Cerutti
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project
The High Luminosity Large Hadron Collider (HL-LHC) is the approved CERN project aiming at further increasing the integrated luminosity of the LHC by a factor 10. As such, it implies a complete redesign of the experimental high-luminosity insertions of ATLAS and CMS. The progressive evolution of the new layout and optics requires a continuous analysis of the radiation environment, to which magnets and other equipment are exposed to. This is assured by means of Monte Carlo simulations of the collision debris on the evolving machine model. The latter featured several developments, such as the explicit inclusion of the cold protection diodes of the final focusing circuits as well as the crab cavities cryomodule. This work presents the most updated characterization of the radiation field with FLUKA and its impact in the insertion region and the dispersion suppressor of Point 1 and 5, for the HL-LHC optics v1.5 released in 2019. Various optimization and mitigation studies are highlighted, providing key information for maximizing the lifetime of new and present magnets.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB012

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paper received ※ 18 May 2021 paper accepted ※ 25 May 2021 issue date ※ 21 August 2021

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MOPAB013

Radiation to Electronics Impact on CERN LHC Operation: Run 2 Overview and HL-LHC Outlook

80

Y.Q. Aguiar, A. Apollonio, F. Cerutti, S. Danzeca, R. García Alía, G. Lerner, D. Prelipcean, M. Sabaté-Gilarte
CERN, Geneva 23, Switzerland

Funding: Research supported by the HL-LHC project
After the mitigation measures implemented during Run 1 (2010-2012) and Long Shutdown 1 (LS1, 2013-2014), the number of equipment failures due to radiation effects on electronics (R2E) leading to LHC beam dumps and/or machine downtime has been sufficiently low as to yield a minor impact on the accelerator performance. During Run 2 (2015-2018) the R2E related failures per unit of integrated luminosity remained below the target value of 0.5 events/fb-1, with the sole exception of the 2015 run during which the machine commissioning took place. However, during 2018, an increase in the failure rate was observed, linked to the increased radiation levels in the dispersion suppressors of the ATLAS and CMS experimental insertions, significantly affecting the Quench Protection System located underneath the superconducting magnets in the tunnel. This work provides an overview of the Run 2 R2E events during LHC proton-proton operation, putting them in the context of the related radiation levels and equipment sensitivity, and providing an outlook for Run 3 and HL-LHC operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB013

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 23 August 2021

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MOPAB014

First High Spin-Flip Efficiency for High Energy Polarized Protons

84

H. Huang, J. Kewisch, C. Liu, A. Marusic, W. Meng, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, T. Roser
BNL, Upton, 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 order to minimize the systematic errors for the Relativistic Heavy Ion Collider (RHIC) spin physics experiments, flipping the spin of each bunch of protons during the stores is needed. Experiments done with single RF magnet at energies less than 2 GeV have demonstrated a spin-flip efficiency over 99%. At high energy colliders with Siberian snakes, a single magnet spin flipper does not work because of the large spin tune spread and the generation of multiple, overlapping resonances. Over past decade, RHIC spin flipper design has evolved and a sophisticated spin flipper, constructed of nine-dipole magnets, was developed to flip the spin in RHIC. A special optics choice was also used to make the spin tune spread very small. In recent experiment, 97% spin-flip efficiency was measured at both 24 and 255 GeV for the first time. The results show that efficient spin flipping can be achieved at high energies.

Poster MOPAB014 [0.984 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB014

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paper received ※ 16 May 2021 paper accepted ※ 08 June 2021 issue date ※ 20 August 2021

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MOPAB017

Influence of Injection Kicker Post-pulses on Storage of Ion Stack in NICA Collider

93

E. Syresin, A. Tuzikov, N.O. Zagibin
JINR, Dubna, Moscow Region, Russia

The peculiarity of the injection kicker power supply in NICA collider is related to same post pulse of the magnetic field which is appeared after a regular injection pulse. The magnetic field of this post pulse became to an increase of the stack ion angle spread during each injection cycle. When the stack ion angles reaches the acceptance angle the ions are lost in the collider. Influence of the injection kicker post pulse on the storage of the ion stack is considered in this paper in presence of the electron cooling and ion electron recombination losses.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB017

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paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 13 August 2021

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MOPAB019

Possible Application of Round-to-Flat Hadron Beam Creation Using 3rd Order Coupling Resonances for the Electron-Ion Collider

99

J. Kallestrup
PSI, Villigen PSI, Switzerland
X. Gu
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
An Electron-Ion Collider (EIC) is planned to be built in Brookhaven National Laboratory with the contribution from Jefferson National Laboratory. To have a high luminosity, both the EIC ion bunch and the EIC electron bunch are designed to be flat during their collision. The existing injector source provides a round beam of width 2.5 um rad transverse emittances. In this paper we investigate the option of dynamically crossing the 2Qx-Qy coupling resonance in order to create a flat-beam with emittance ratio Ex/Ey of up to 4. Furthermore, we explore the possibility of using a pulsed- or AC skew sextupole magnets to achieve a similar effect. Using one of these methods for flat beam creation will help lower the ion beam cooling time.

Poster MOPAB019 [0.323 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB019

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 24 August 2021

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MOPAB022

FailSim: A Numerical Toolbox for the Study of Fast Failures and Their Impact on Machine Protection at the CERN Large Hadron Collider

111

C. Hernalsteens, G. Sterbini, O.K. Tuormaa, C. Wiesner, D. Wollmann
CERN, Meyrin, Switzerland

The High Luminosity LHC (HL-LHC) foresees to reach a nominal, levelled luminosity of 5·10³⁴ cm^-2 s⁻¹ through a higher beam brightness and by using new equipment, such as larger aperture final focusing quadrupole magnets. The HL-LHC upgrade has critical impacts on the machine protection strategy, as the stored beam energy reaches 700 MJ for each of the two beams. Some failure modes of the novel active superconducting magnet protection system of the inner triplet magnets, namely the Coupling-Loss Induced Quench (CLIQ) systems, have been identified as critical. This paper reports on FailSim, a Python-language framework developed to study the machine protection impact of failure cases and their proposed mitigation. It provides seamless integration of the successive phases required by the simulation studies, i.e., verifying the optics, preparing and running a MAD-X instance for multiple particle tracking, processing and analysing the simulation results and summarising them with the relevant plots to provide a solid estimate of the beam losses, their location and time evolution. The paper also presents and discusses the result of its application on the spurious discharge of a CLIQ unit.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB022

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 18 August 2021

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MOPAB023

Experimental Test of a New Method to Verify Retraction Margins Between Dump Absorbers and Tertiary Collimators at the LHC

115

C. Wiesner, W. Bartmann, C. Bracco, R. Bruce, J. Molson, M. Schaumann, C. Staufenbiel, J.A. Uythoven, M. Valette, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Meyrin, Switzerland

The protection of the tertiary collimators (TCTs) and the LHC triplet aperture in case of a so-called asynchronous beam dump relies on the correct retraction between the TCTs and the dump region absorbers. A new method to validate this retraction has been proposed, and a proof-of-principle experiment was performed at the LHC. The method uses a long orbit bump to mimic the change of the beam trajectory caused by an asynchronous firing of the extraction kickers. It can, thus, be performed with circulating beam. This paper reports on the performed beam measurements, compares them with expectations and discusses the potential benefits of the new method for machine protection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB023

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paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 24 August 2021

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MOPAB024

Efficient Coupling of Hydrodynamic and Energy-Deposition Codes for Hydrodynamic-Tunnelling Studies on High-Energy Particle Accelerators

119

C. Wiesner, F. Carra, J. Kruse-Hansen, M. Masci, D. Wollmann
CERN, Meyrin, Switzerland
Y. Nie
KIT, Karlsruhe, Germany

The machine-protection evaluation of high-energy accelerators comprises the study of beyond-design failures, including the direct beam impact onto machine elements. In case of a direct impact, the nominal beam of the Large Hadron Collider (LHC) would penetrate more than 30 meters into a solid copper target. The penetration depth due to the time structure of the particle beam is, thus, significantly longer than predicted from purely static energy-deposition simulations with 7 TeV protons. This effect, known as hydrodynamic tunnelling, is caused by the beam-induced density depletion of the material at the target axis, which allows subsequent bunches to penetrate deeper into the target. Its proper simulation requires, therefore, to sequentially couple an energy-deposition code and a hydrodynamic code for the different target densities. This paper describes a method to efficiently couple the simulations codes Autodyn and FLUKA based on automatic density assignment and input file generation, and presents the results achieved for a sample case.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB024

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paper received ※ 19 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021

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MOPAB025

First Experiments with Accelerated Ion Beams in the Booster of NICA Accelerator Complex

123

A.V. Butenko, V. Andreev, A.M. Bazanov, O.I. Brovko, D.E. Donets, A.V. Eliseev, I.V. Gorelyshev, A.V. Konstantinov, S.A. Kostromin, O.S. Kozlov, K.A. Levterov, A. Nesterov, A.V. Philippov, D.O. Ponkin, G.S. Sedykh, I.V. Shirikov, A.O. Sidorin, E. Syresin, A. Tuzikov, V. Volkov
JINR/VBLHEP, Dubna, Moscow region, Russia
N.N. Agapov, A.V. Alfeev, A.A. Baldin, A.A. Fateev, A.R. Galimov, B.V. Golovenskiy, E.V. Gorbachev, A. Govorov, E.V. Ivanov, V. Karpinsky, V.D. Kekelidze, H.G. Khodzhibagiyan, A. Kirichenko, A.G. Kobets, S.A. Korovkin, V. Kosachev, A.D. Kovalenko, G. Kunchenko, I.N. Meshkov, V.A. Mikhailov, V.A. Monchinsky, D. Nikiforov, R.V. Pivin, S. Romanov, A.A. Shurygin, A.I. Sidorov, A.N. Svidetelev, G.V. Trubnikov, B. Vasilishin
JINR, Dubna, Moscow Region, Russia
G.A. Fatkin
Cosylab Siberia, Novosibirsk, Russia

The NICA accelerator complex in JINR consist of two linear injector chains, a 578 MeV/u superconducting (SC) Booster synchrotron, the existing SC synchrotron Nuclotron, and a new SC collider that has two storage rings. The construction of the facility is based on the Nuclotron technology of SC magnets with an iron yoke and hollow SC cable. Assembly of the Booster synchrotron was finished in autumn of 2020 and first machine Run and experiments with ion beams were successfully done in December 2020. The results of this Run are discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB025

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paper received ※ 16 May 2021 paper accepted ※ 07 September 2021 issue date ※ 15 August 2021

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MOPAB026

RHIC Delayed Abort Experiments

126

M. Valette, D. Bruno, K.A. Drees, K.M. Hartmann, G. Heppner, K. Mernick, C. Mi, J.-L. Mi, R.J. Michnoff, J. Morris, F. Orsatti, E. Rydout, T. Samms, J. Sandberg, V. Schoefer, C. Schultheiss, T.C. Shrey, C. Theisen
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
For RHIC to operate at its top energy (100 GeV/n) while protecting the future sPHENIX detector, spontaneous and asynchronous firing of abort kicker modules (pre-fires) have to be avoided. A new triggering circuit for the abort kickers was implemented with relatively slow mechanical relays in series with the standard fast thyratron tubes. The relays prevents unwanted pre-fires during operation, but comes at the expense of a long latency - about 7 milliseconds - between the removal of beam permit and the actual firing of the abort kickers. Protection considerations of RHIC’s superconducting magnets forbid delaying energy extraction from the main dipoles and quadrupoles for too long after a quench. The beam has thus to circulate in both RHIc rings for a few milliseconds as the current in dipole and quadrupole circuit is being extracted. We present the results of delayed abort experiments conducted in July 2018 with the analysis of fast orbit and tune measurements and discuss the safety implications of this implementation for future RHIC operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB026

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paper received ※ 19 May 2021 paper accepted ※ 26 May 2021 issue date ※ 23 August 2021

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MOPAB027

Improving the Luminosity Burn-Off Estimate by Considering Single-Diffractive Effects

130

F.F. Van der Veken, H. Burkhardt, M. Giovannozzi, V.K.B. Olsen
CERN, Geneva, Switzerland

Collisions in a high-luminosity collider result in a continuous burn-off of the circulating beams that is the dominant effect that reduces the instantaneous luminosity over time. In order to obtain a good estimate of the luminosity evolution, it is imperative to have an accurate understanding of the burn-off. Typically, this is calculated based on the inelastic cross-section, as it provides a direct estimate of the number of protons that participate in inelastic collisions, and are hence removed. Likewise, protons that participate in elastic collisions will remain in the machine acceptance, still contributing to luminosity. In between these two regimes lie diffractive collisions, for which the protons have a certain probability to remain in the machine acceptance. Recent developments of the SixTrack code allow it to interface with Pythia, thus allowing for more precise simulations to obtain a better estimate of the diffractive part of the cross-section. In this paper, we will mainly concentrate on slowly-drifting protons that are close to the acceptance limit, resulting from single-diffractive scattering.

Poster MOPAB027 [1.193 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB027

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 11 August 2021

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MOPAB029

Burn-Off with Asymmetric Interaction Points

138

R. Tomás García, I. Efthymiopoulos, G. Iadarola
CERN, Geneva, Switzerland

LHC can host above 2700 proton bunches per ring providing collisions in the ATLAS, CMS, LHCb and ALICE interaction points. ATLAS and CMS are placed symmetrically so that they feature the same colliding bunch pairs. However this is not the case for LHCb, hence introducing unwanted bunch-by-bunch variations of the bunch intensity as the physics fill evolves. We present first analytical derivations, numerical simulations and experimental data in different bunch train collision configurations.

Poster MOPAB029 [1.502 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB029

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paper received ※ 13 May 2021 paper accepted ※ 25 May 2021 issue date ※ 27 August 2021

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WEXA01

Successful Crabbing of Proton Beams

2510

R. Calaga
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project and by the DOE and UK-STFC.
Many future particle colliders require beam crabbing to recover the geometric luminosity loss from the non-zero crossing angle at the interaction point. A first demonstration experiment of crabbing with hadron beams was successfully carried out with high energy protons. This breakthrough result is fundamental to achieve the physics goals of the high luminosity LHC upgrade project (HL-LHC) and the future circular collider (FCC). The expected peak luminosity gain (related to collision rate) is 65% for HL-LHC, and even greater for the FCC. Novel beam physics experiments with proton beams in CERN’s Super Proton Synchrotron (SPS) were performed to demonstrate several critical aspects for the operation of crab cavities in the future HL-LHC including transparency with a pair of cavities, a full characterization of the cavity impedance with high beam currents and controlled emittance growth from crab cavity induced RF noise.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA01

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 24 August 2021

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WEXA02

Operational Electron Cooling in the Relativistic Heavy Ion Collider

2516

A.V. Fedotov, K.A. Drees, W. Fischer, X. Gu, D. Kayran, J. Kewisch, C. Liu, K. Mernick, M.G. Minty, V. Schoefer, H. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
Since the invention of the electron cooling technique its application to cool hadron beams in colliders was considered for numerous accelerator physics projects worldwide. However, achieving the required high-brightness electron beams of required quality and cooling of ion beams in collisions was deemed to be challenging. An electron cooling of ion beams employing a high-energy approach with RF-accelerated electron bunches was recently successfully implemented at BNL. It was used to cool ion beams in both collider rings with ion beams in collision. Electron cooling in RHIC became fully operational during the 2020 physics run and led to substantial improvements in luminosity. This presentation will discuss implementation, optimization and challenges of electron cooling for colliding ion beams in RHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA02

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 31 August 2021

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WEXA05

Solving for Collider Beam Profiles from Luminosity Jitter with Ghost Imaging

2524

D.F. Ratner, A. Chao
SLAC, Menlo Park, California, USA

Large accelerator facilities must balance the need to achieve user performance requirements while also maximizing delivery time. At the same time, accelerators have advanced data-acquisition systems that acquire synchronous data at high-rate from a large variety of diagnostics. Here we discuss the application of ghost-imaging (GI) to measure beam parameters, switching the emphasis from beam control to data collection: rather than intentionally manipulating the accelerator, we instead passively monitor jitter gathered over thousands to millions of events to reconstruct the target of interest. Passive monitoring during routine operation builds large data sets that can even deliver higher resolution than brief periodic scans, and can provide experiments with event-by-event information. In this presentation we briefly present applications of GI to light-sources, and then discuss a potential new application for colliders: measuring the transverse beam shapes at a collider’s interaction point to determine both the integrated luminosity and the spatial distribution of collision vertices.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA05

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 10 August 2021

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WEXA06

Study of Pb-Pb and Pb-p Collision Debris in the CERN LHC in View of HL-LHC Operation

2528

M. Sabaté-Gilarte, R. Bruce, F. Cerutti, A. Lechner
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project
For the first time, a full characterization of the Pb-Pb and Pb-p collision debris as well as its impact in terms of energy deposition in the long straight section (LSS) of CERN’s Large Hadron Collider has been carried out. By means of Monte Carlo simulations with FLUKA, both inelastic nuclear interaction and electromagnetic dissociation were taken into account as source term for lead ion operation, while for Pb-p operation only nuclear interaction is of importance. The radiation exposure of detectors exclusively destined for ion beam runs is assessed, allowing drawing implications of their use. This work gave the opportunity for an unprecedented validation of simulation results against measurement of beam loss monitors (BLM) in the experimental LSS during ion operation. Pb-Pb operation refers to the 2018 ion run at 6.37 TeV per charge with a +160 microrad half crossing angle in the vertical plane at the ATLAS interaction point. Instead, Pb-p operation was benchmarked for the 2016 ion run at 6.5 TeV per charge with -140 microrad half crossing angle in the vertical plane at the same location.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA06

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paper received ※ 18 May 2021 paper accepted ※ 05 July 2021 issue date ※ 22 August 2021

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WEPAB026

Optics Measurements and Correction Plans for the HL-LHC

2656

T.H.B. Persson, X. Buffat, F.S. Carlier, R. De Maria, J. Dilly, E. Fol, D. Gamba, H. Garcia Morales, A. García-Tabarés Valdivieso, M. Giovannozzi, M. Hofer, E.J. Høydalsvik, J. Keintzel, M. Le Garrec, E.H. Maclean, L. Malina, P.K. Skowroński, F. Soubelet, R. Tomás García, F.F. Van der Veken, A. Wegscheider, D.W. Wolf, L. van Riesen-Haupt
CERN, Geneva, Switzerland
J.M. Coello de Portugal
PSI, Villigen PSI, Switzerland

The High Luminosity LHC (HL-LHC) will require stringent optics correction to operate safely and deliver the design luminosity to the experiments. In order to achieve this, several new methods for optics correction have been developed. In this article, we outline some of these methods and we describe the envisioned strategy of how to use them in order to reach the challenging requirements of the HL-LHC physics program.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB026

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paper received ※ 17 May 2021 paper accepted ※ 27 July 2021 issue date ※ 30 August 2021

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WEPAB027

Optics Correction Strategy for Run 3 of the LHC

2660

T.H.B. Persson, R. De Maria, J. Dilly, E. Fol, H. Garcia Morales, M. Hofer, E.J. Høydalsvik, J. Keintzel, M. Le Garrec, E.H. Maclean, L. Malina, F. Soubelet, R. Tomás García, A. Wegscheider, D.W. Wolf, L. van Riesen-Haupt
CERN, Geneva, Switzerland
J.F. Cardona
UNAL, Bogota D.C, Colombia

The Run 3 of the LHC will continue to provide new challenges for optics corrections. In order to succeed and go beyond what was achieved previously, several new methods to measure and correct the optics have been developed. In this article we describe these methods and outline the plans for the optics commissioning in 2022.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB027

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paper received ※ 17 May 2021 paper accepted ※ 12 July 2021 issue date ※ 11 August 2021

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WEPAB028

MAD-X for Future Accelerators

2664

T.H.B. Persson, H. Burkhardt, L. Deniau, A. Latina, P.K. Skowroński
CERN, Geneva, Switzerland

The feasibility and performance of the future accelerators must, to a large extent, be predicted by simulation codes. This implies that simulation codes need to include effects that previously played a minor role. For example, in large electron machines like the FCC-ee the large energy variation along the ring requires that the magnets strength is adjusted to the beam energy at that location, normally referred to as tapering. In this article, we present new features implemented in the MAD-X code to enable and facilitate simulations of future colliders.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB028

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paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 27 August 2021

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WEPAB033

Lattice Design of the CEPC Collider Ring for a High Luminosity Scheme

2679

Y. Wang, S. Bai, J. Gao, B. Wang, D. Wang, Y. Wei, J. Wu, C.H. Yu, J.Y. Zhai, Y. Zhang, Y.S. Zhu
IHEP, Beijing, People’s Republic of China
Y. Zhang
University of Chinese Academy of Sciences, Beijing, People’s Republic of China

A high luminosity scheme of the CEPC has been proposed aiming to increase the luminosity mainly at Higgs and Z modes. In this paper, the high luminosity scheme will be introduced briefly, including the beam parameters and RF staging. Then, the lattice design of the CEPC collider ring for the high luminosity scheme will be presented, including the bare lattice design and dynamic aperture optimization at Higgs energy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB033

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paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 27 August 2021

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THPAB001

Reaching the Sub Per Mil Level Coupling Corrections in the LHC

3752

E.J. Høydalsvik, T.H.B. Persson
CERN, Geneva, Switzerland

The High Luminosity LHC (HL-LHC) is requiring sub per mil coupling correction, as defined by the closest tune approach. In this article, the current coupling correction strategy is analyzed in order to understand if it can robustly correct to these very low levels. The impact of realistic errors on the coupling correction is investigated with MAD-X simulations, including the influence of local coupling on the global coupling correction. Through simulations and measurements in the LHC, the effect of BPM noise on the coupling correction is analyzed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB001

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paper received ※ 11 May 2021 paper accepted ※ 28 July 2021 issue date ※ 23 August 2021

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THPAB172

Bunch Luminosity Variations in LHC Run 2

4094

I. Efthymiopoulos, S.D. Fartoukh, G. Iadarola, N. Karastathis, S. Papadopoulou, Y. Papaphilippou
CERN, Geneva, Switzerland

The LHC is designed to collide intense bunches of protons with tightly defined conditions, aimed to maximize the delivered recorded integrated luminosity to the experiments. One of these conditions is the maximum level of bunch-to-bunch fluctuation in the luminosity, in particular when levelling at maximum acceptable event rate at the experiments. Analysis results of the bunch-to-bunch luminosity variations in LHC Run 2 are presented here. In particular, the observed correlations with the LHC filling pattern that can enhance the effects introducing bunch-dependent losses or emittance blow-up from injection to collisions are discussed. In Run 2 conditions, bunch-by-bunch luminosity fluctuations reached 10% at the start of collisions and gradually increased with time, without affecting the experiments as the luminosity was not levelled. Projections for Run 3 and HL-LHC operation are discussed along with envisaged mitigation measures.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB172

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paper received ※ 18 May 2021 paper accepted ※ 19 July 2021 issue date ※ 23 August 2021

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