IPAC2021 - List of Authors (Tomas, R.)

Paper	Title	Page
MOXB02	First Results of the IOTA Ring Research at Fermilab	19
	A. Valishev, D.R. Broemmelsiek, A.V. Burov, K. Carlson, B.L. Cathey, S. Chattopadhyay, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, H. Piekarz, A.L. Romanov, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA A. Arodzero, A.Y. Murokh, M. Ruelas RadiaBeam, Santa Monica, California, USA D.L. Bruhwiler, J.P. Edelen, C.C. Hall RadiaSoft LLC, Boulder, Colorado, USA S. Chattopadhyay, S. Szustkowski Northern Illinois University, DeKalb, Illinois, USA A. Halavanau, Z. Huang, V. Yakimenko SLAC, Menlo Park, California, USA M. Hofer TU Vienna, Wien, Austria M. Hofer, R. Tomás García CERN, Geneva, Switzerland K. Hwang, C.E. Mitchell, R.D. Ryne LBNL, Berkeley, California, USA K.-J. Kim ANL, Lemont, Illinois, USA K.-J. Kim, Y.K. Kim, N. Kuklev, I. Lobach University of Chicago, Chicago, Illinois, USA T.V. Shaftan BNL, Upton, New York, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The IOTA ring at Fermilab is a unique machine exclusively dedicated to accelerator beam physics R&D. The research conducted at IOTA includes topics such as nonlinear integrable optics, suppression of coherent beam instabilities, optical stochastic cooling and quantum science experiments. In this talk we report on the first results of experiments with implementations of nonlinear integrable beam optics. The first of its kind practical realization of a two-dimensional integrable system in a strongly-focusing storage ring was demonstrated allowing among other things for stable beam circulation near or at the integer resonance. Also presented will be the highlights of the world’s first demonstration of optical stochastic beam cooling and other selected results of IOTA’s broad experimental program.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXB02
About •	paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 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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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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MOPAB184	Unsupervised Learning Techniques for Tune Cleaning Measurement	624
	H. Garcia Morales Oxford University, Physics Department, Oxford, Oxon, United Kingdom E. Fol, R. Tomás García CERN, Geneva, Switzerland
	Precise measurements of tune and its stability are crucial for various optics analyses in the LHC, e.g. for the determination of the beta star using K-modulation. LHC BBQ system provides tune measurements online and stores the tune data. We apply unsupervised machine learning techniques on BBQ tune data in order to provide an automatic outlier detection method for better measurements of tune shifts and unexpected tune jitters.
	Poster MOPAB184 [0.354 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB184
About •	paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 11 August 2021
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MOPAB185	HL-LHC Local Linear Optics Correction at the Interaction Regions	628
	H. Garcia Morales Oxford University, Physics Department, Oxford, Oxon, United Kingdom J.F. Cardona UNAL, Bogota D.C, Colombia R. Tomás García CERN, Geneva, Switzerland
	Magnetic imperfections of the HL-LHC inner triplet are expected to generate a significant \beta-beating. For that reason, improved local optics correction techniques at the low-\beta insertions is essential to ensure a high luminosity performance in the HL-LHC. In this study, we compare different strategies for local optics correction at the Interaction Regions with respect to their final performance in terms of residual \beta-beating. Supervised learning techniques are also explored to predict the inner triplet magnetic error contributions.
	Poster MOPAB185 [0.469 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB185
About •	paper received ※ 14 May 2021 paper accepted ※ 10 June 2021 issue date ※ 31 August 2021
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MOPAB186	Comparison of Segment-by-Segment and Action-Phase-Jump Techniques in the Calculation of IR Local Corrections in LHC	632
	H. Garcia Morales Oxford University, Physics Department, Oxford, Oxon, United Kingdom J.F. Cardona UNAL, Bogota D.C, Colombia R. Tomás García CERN, Geneva, Switzerland
	The correction of the local optics at the Interaction Regions of the LHC is crucial to ensure a good performance of the machine. In this paper, we compare two different techniques for local optics correction: Action-Phase Jump and Segment-by-Segment techniques. The comparison is made in view of future machine configurations such as Run 3 LHC optics and HL-LHC optics.
	Poster MOPAB186 [0.349 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB186
About •	paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 30 August 2021
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MOPAB230	The Optics Design for the Final Focus System of CLIC 380 GeV	748
	A. Pastushenko, R. Tomás García CERN, Geneva, Switzerland A. Faus-Golfe Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	The first stage of the Compact Linear Collider (CLIC) is planned to be at the center-of-mass energy of 380 GeV. The final focus system (FFS) was re-optimized for this energy and for L* of 6 m (distance between the Interaction Point (IP) and the last quadrupole, QD0). Furthermore, the FFS optics was optimized for the vertical beta-function of 70 microns to approach the Hourglass effect limit. This paper reports the exploration of shortening the Final Doublet (FD) within the FFS to reduce the chromaticity. In addition, an alternative optics design is investigated with a different dispersion profile along the FFS, which outperforms the previous optics with the same β^*, increasing luminosity by 5 %.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB230
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 11 August 2021
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MOPAB231	Tunability Study of the Ultra-Low β* Optics at ATF2 with New Octupole Setup and Tuning Knobs	752
	A. Pastushenko, R. Tomás García CERN, Geneva, Switzerland A. Faus-Golfe Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France K. Kubo, S. Kuroda, T. Naito, T. Okugi, N. Terunuma, R.J. Yang KEK, Ibaraki, Japan
	The main goal of the Accelerator Test Facility 2 (ATF2) is to demonstrate the feasibility of future linear colliders’ final focus systems. The Ultra-low β^* optics of ATF2 is designed to have the same chromaticity level as CLIC. To ease the tuning procedure, a pair of octupoles was installed in ATF2 in 2017. This paper reports the optimizations performed to the octupoles’ setup for Ultra-low β^* optics including the new alignment technique, based on the waist shift and the new tunning knobs constructed for this optics. The full tuning procedure including the static errors is simulated for this setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB231
About •	paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021
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MOPAB258	Corrections of Non-Linear Field Errors with Asymmetric Optics in LHC and HL-LHC Insertion Regions	817
	J. Dilly, E.H. Maclean, R. Tomás García CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project, CERN and the german Federal Ministry of Education and Research. Existing correction schemes to locally suppress resonance driving terms in the error-sensitive high-beta regions of the LHC and HL-LHC have operated on the assumption of symmetric beta-functions of the optics in the two rings. As this assumption can fail for a multitude of reasons, such as inherently asymmetric optics and unevenly distributed errors, an extension of this correction scheme has been developed removing the need for symmetry by operating on the two separate optics of the beams at the same time. Presented here is the impact of this novel approach on dynamic aperture as an important measure of particle stability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB258
About •	paper received ※ 10 May 2021 paper accepted ※ 23 July 2021 issue date ※ 16 August 2021
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MOPAB259	Corrections of Feed-Down of Non-Linear Field Errors in LHC and HL-LHC Insertion Regions	821
	J. Dilly, E.H. Maclean, R. Tomás García CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project, CERN and the german Federal Ministry of Education and Research. The optics in the insertion regions of the LHC and its upgrade project the High Luminosity LHC (HL-LHC) are very sensitive to local magnetic errors, due to the extremely high beta-functions present. In collision optics, the non-zero closed orbit in the same region leads to a "feed-down" of high-order errors to lower orders, causing additional effects detrimental to beam lifetime. An extension to the proven method for correcting these errors by locally suppressing resonance driving terms has been undertaken, not only taking this feed-down into account, but also adding the possibility of utilizing it such that the powering of higher-order correctors will compensate for lower order errors. The impact of these corrections on measures of particle stability, namely dynamic aperture and amplitude detuning are presented in this contribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB259
About •	paper received ※ 10 May 2021 paper accepted ※ 23 July 2021 issue date ※ 15 August 2021
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TUPAB004	Comparison of Accelerator Codes for Simulation of Lepton Colliders	1334
	L. van Riesen-Haupt, H. Burkhardt, T.H.B. Persson, R. Tomás García CERN, Geneva, Switzerland
	This paper compares simulation results obtained with SAD, MAD-X and the PTC implementation in MADX for the design studies of the FCC-ee. On-momentum and off-momentum optics are explored for the various programs. Particle tracking with and without synchrotron radiation are used to compare amplitude detuning and emittance. Finally, this paper outlines how well-established SAD features such as tapering have recently been integrated into MADX.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB004
About •	paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 26 August 2021
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TUPAB005	Emittance Estimates for the Future Circular Collider	1338
	L. van Riesen-Haupt, T.K. Charles, R. Tomás García, F. Zimmermann CERN, Meyrin, Switzerland T.K. Charles The University of Liverpool, Liverpool, United Kingdom
	The alignment strategy of the FCC-ee has a large impact on its luminosity. Larger alignment tolerances result in increased coupling and a subsequently higher vertical emittance. At the same time, tighter alignment tolerances around the 100 km ring are a major cost driver. This paper applies analytical emittance estimate methods to the FCC-ee and compares their predictions to data from simulations with different alignment tolerances. These methods can be used to help understand the impact of misalignments of certain magnet groups and to come up with an efficient alignment strategy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB005
About •	paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 26 August 2021
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TUPAB006	The Impact of Beam Position Monitor Tilts on Coupling Measurements	1342
	L. van Riesen-Haupt, R. Tomás García CERN, Geneva, Switzerland
	The measurement and correction of coupling resonance driving terms is a key tool for improving the performance of synchrotrons. These terms are measured by exciting the beam and observing the subsequent motion in the horizontal and vertical planes through beam position monitors. This paper outlines the impact of tilt errors in these monitors to the distortion of the amount of coupling measured between the planes and how the computation of the resonance driving terms is affected by these tilts. It also attempts to use these results for mimicking tilt errors in simulations and discusses how discrepancies in measured resonance driving terms could be used to estimate the tilt errors that cause them.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB006
About •	paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 12 August 2021
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TUPAB009	SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data	1352
	J. Keintzel, R. Tomás García CERN, Geneva, Switzerland H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang KEK, Ibaraki, Japan
	SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021
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TUPAB010	Impact of Bunch Current on Optics Measurements in SuperKEKB	1356
	J. Keintzel, R. Tomás García, F. Zimmermann CERN, Geneva, Switzerland T. Ishibashi, H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, S. Terui, M. Tobiyama, R.J. Yang, D. Zhou KEK, Ibaraki, Japan
	SuperKEKB has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} and aims at reaching a target luminosity of about 6 × 10³⁵ \si{cm^-2s^-1}. To accomplish this goal it is planned to increase beam currents up to §I{3.6}{A} and §I{2.6}{A} for the positron and the electron ring, respectively. Increasing the beam currents and, in particular, the number of leptons per bunch, can impact the optics parameters obtained by turn-by-turn measurements, such as the betatron tune or phase advance. Optics measurements performed at various bunch currents can give first indications of possible intensity dependent effects. In this paper, the effect of varying bunch current on optics measurements at SuperKEKB is explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 30 August 2021
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TUPAB011	Momentum Compaction Factor Measurements in the Large Hadron Collider	1360
	J. Keintzel, L. Malina, R. Tomás García CERN, Geneva, Switzerland
	The Large Hadron Collider (LHC) at CERN and its planned luminosity upgrade, the High Luminosity LHC (HL-LHC) demand well-controlled on- and off-momentum optics. Optics measurements are performed by analysing Turn-by-Turn (TbT) data of excited beams. Different techniques to measure the momentum compaction factor from these data are explored, taking into account the possibility to combine them with RF-voltage scans in future experiments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB011
About •	paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 18 August 2021
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TUPAB013	A CLIC Dual Beam Delivery System for Two Interaction Regions	1364
	V. Cilento, R. Tomás García CERN, Geneva, Switzerland A. Faus-Golfe Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	The Compact Linear Collider (CLIC) could provide e⁺e⁻ collisions in two detectors simultaneously possibly at a repetition frequency twice the design value. In this paper, a novel dual Beam Delivery System (BDS) design is presented including optics designs and the evaluation of luminosity performance with synchrotron radiation (SR) and solenoid effects for both energy stages of CLIC, 380 GeV and 3 TeV. In order to develop the novel optics design, parameters such as the longitudinal and the transverse detector separations were optimized. The luminosity performance of the novel CLIC scheme was evaluated by comparing the different BDS designs for both energy stages of CLIC. The dual CLIC BDS design provides a good luminosity and proves to be a viable candidate for future linear collider projects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB013
About •	paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 31 August 2021
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TUPAB224	Non-Linear Variation of the Beta-Beating Measured From Amplitude	1949
	T. Pugnat, B. Dalena CEA-IRFU, Gif-sur-Yvette, France A. Franchi ESRF, Grenoble, France R. Tomás García CERN, Geneva, Switzerland
	Accelerator physics needs advanced modeling and simulation techniques, for beam stability studies but also for the measurement of beam parameters like the Twiss parameters. A deeper understanding of magnetic field non-linearities effects will greatly help in the improvement of future circular collider design, performance, and diagnostics. This paper studies the variation of the \beta-beating with the action of the particle generated by non-linear Resonance Driving Terms, both from a theoretical and an experimental point of view.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB224
About •	paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 21 August 2021
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TUPAB231	Cooling of an Annular Beam by Using Nonlinear Effects	1968
	F. Capoani, M. Giovannozzi, R. Tomás García CERN, Geneva, Switzerland A. Bazzani, F. Capoani Bologna University, Bologna, Italy
	In recent years, nonlinear effects have been used to modify the transverse beam distribution by crossing nonlinear resonances adiabatically. This allows generating transversally split beams, in which the initial single Gaussian is divided into several ones depending on the order and stability type of the resonance used. Nonlinear effects could be used to try and cool a beam by acting on its transverse beam distribution. In this paper, we present and discuss the special case of a beam with an annular distribution, showing how the resulting emittance could be reduced by means of nonlinear effects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB231
About •	paper received ※ 10 May 2021 paper accepted ※ 16 June 2021 issue date ※ 21 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, Meyrin, 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, Meyrin, 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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WEPAB399	Applications of the Local Observable in Future Optics Measurements in HL-LHC and PETRA III	3642
	A. Wegscheider, R. Tomás García CERN, Geneva, Switzerland
	Phase advances among four nearby beam position monitors in a circular accelerator can be used to calculate a local observable of quadrupolar lattice imperfections. This work explores the applicability of this local observable to two different circular accelerators: PETRA III, a synchrotron light source, and the LHC, a hadron collider as well as its upgrade project HL-LHC. MADX simulations for important optics settings are performed, showing that the local observable can detect strong error sources. This is of particular interest in important regions of the accelerators like the LHC’s interaction regions and PETRA III’s experimental hall.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB399
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 12 August 2021
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WEPAB400	Forced Coupling Resonance Driving Terms	3646
	A. Wegscheider, R. Tomás García CERN, Geneva, Switzerland
	At the LHC, coupling is routinely measured using forced oscillations of the beam through excitation with an AC-dipole. The driving of the particle motion has an impact on the measurement of resonance driving terms. Recent findings suggest that the current models describing the forced motion are neglecting a local effect of the AC-dipole, creating a jump of the amplitude of the resonance driving terms. This work presents a study of the improvement of coupling measurements for typical LHC optics as well as its upgrade project HL-LHC, by using the new model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB400
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 20 August 2021
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THXA07	Driven 3D Beam Oscillations for Optics Measurements in Synchrotrons	3704
	L. Malina, J.M. Coello de Portugal, H. Timko, R. Tomás García CERN, Geneva, Switzerland
	Optics measurements in storage rings employ turn-by-turn data of transversely excited beams. Traditionally, to measure chromatic properties, the relative momentum is changed step-wise, which is time-consuming and almost impractical during the energy ramp. We present an optics measurement method based on adiabatic simultaneous 3-dimensional beam excitation, which is more time-efficient and well fitted for the energy ramp. This method was successfully demonstrated in the LHC utilising AC-dipoles in combination either with a slow RF-frequency modulation or a driven RF-phase modulation close to the synchrotron frequency. Faster longitudinal oscillations improve the accuracy of optics parameters inferred from the synchro-betatron sidebands. This paper reports on the experimental demonstration of optics measurements based on 3D driven beam excitations and the plans for LHC Run 3.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA07
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 11 August 2021
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THPAB055	Reconstruction of Linear Optics Observables Using Supervised Learning	3875
	E. Fol, H. Garcia, R. Tomás García CERN, Geneva, Switzerland
	In the LHC, most of the optical functions can be obtained from turn-by-turn beam centroid data. However, the measurement of such observables as β^* and the dispersion function require special dedicated techniques and additional operational time. In this work, we propose an alternative approach to estimate these observables using supervised machine learning, in case the dedicated measurements are not available but turn-by-turn data are. The performance of developed estimators is demonstrated on LHC simulations. Comparison to traditional techniques for the computation of beta-function will be also provided.
	Poster THPAB055 [0.713 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB055
About •	paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 15 August 2021
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THPAB068	Denoising of Optics Measurements Using Autoencoder Neural Networks	3915
	E. Fol, R. Tomás García CERN, Geneva, Switzerland
	Noise artefacts can appear in optics measurements data due to instrumentation imperfections or uncertainties in the applied analysis methods. A special type of semi-supervised neural networks, autoencoders, are widely applied to denoising tasks in image and signal processing as well as to generative modeling. Recently, an autoencoder-based approach for denoising and reconstruction of missing data has been developed to improve the quality of phase measurements obtained from harmonic analysis of LHC turn-by-turn data. We present the results achieved on simulations demonstrating the potential of the new method and discuss the effect of the noise in light of optics corrections computed from the cleaned data.
	Poster THPAB068 [0.881 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB068
About •	paper received ※ 19 May 2021 paper accepted ※ 13 July 2021 issue date ※ 02 September 2021
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THPAB168	Optics Measurement by Excitation of Betatron Oscillations in the CERN PSB	4078
	E.H. Maclean, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, J. Dilly, E. Fol, H. Garcia Morales, M. Hofer, J. Keintzel, M. Le Garrec, T.E. Levens, L. Malina, T.H.B. Persson, T. Prebibaj, E. Renner, P.K. Skowroński, F. Soubelet, R. Tomás García, A. Wegscheider, L. van Riesen-Haupt CERN, Meyrin, Switzerland
	Optics measurement from analysis of turn-by-turn BPM data of betatron oscillations excited with a kicker magnet has been employed very successfully in many machines but faces particular challenges in the CERN PSB where BPM to BPM phase advances are sub-optimal for optics reconstruction. Experience using turn-by-turn oscillation data for linear optics measurements during PSB commissioning in2021 is presented, with implications for the prospect of such techniques in the PSB more generally.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB168
About •	paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 27 August 2021
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THPAB169	A Mechanism for Emittance Growth Based on Non-Linear Islands in LHC	4082
	E.H. Maclean, M. Giovannozzi, T.H.B. Persson, R. Tomás García CERN, Geneva, Switzerland
	Landau octupoles are used in the LHC to prevent coherent instabilities of the circulating beam. The reduction of their strength occurring during the energy ramp can transport particles in nonlinear islands to larger amplitude. This has the potential to lead to emittance growth and to beam-losses. Beam-based studies and simulations of emittance growth during Landau octupole ramps performed in the LHC are presented to explore this mechanism in more detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB169
About •	paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 14 August 2021
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Paper

Title

Page

First Results of the IOTA Ring Research at Fermilab

19

A. Valishev, D.R. Broemmelsiek, A.V. Burov, K. Carlson, B.L. Cathey, S. Chattopadhyay, N. Eddy, D.R. Edstrom, J.D. Jarvis, V.A. Lebedev, S. Nagaitsev, H. Piekarz, A.L. Romanov, J. Ruan, J.K. Santucci, V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA
A. Arodzero, A.Y. Murokh, M. Ruelas
RadiaBeam, Santa Monica, California, USA
D.L. Bruhwiler, J.P. Edelen, C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA
S. Chattopadhyay, S. Szustkowski
Northern Illinois University, DeKalb, Illinois, USA
A. Halavanau, Z. Huang, V. Yakimenko
SLAC, Menlo Park, California, USA
M. Hofer
TU Vienna, Wien, Austria
M. Hofer, R. Tomás García
CERN, Geneva, Switzerland
K. Hwang, C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA
K.-J. Kim
ANL, Lemont, Illinois, USA
K.-J. Kim, Y.K. Kim, N. Kuklev, I. Lobach
University of Chicago, Chicago, Illinois, USA
T.V. Shaftan
BNL, Upton, New York, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The IOTA ring at Fermilab is a unique machine exclusively dedicated to accelerator beam physics R&D. The research conducted at IOTA includes topics such as nonlinear integrable optics, suppression of coherent beam instabilities, optical stochastic cooling and quantum science experiments. In this talk we report on the first results of experiments with implementations of nonlinear integrable beam optics. The first of its kind practical realization of a two-dimensional integrable system in a strongly-focusing storage ring was demonstrated allowing among other things for stable beam circulation near or at the integer resonance. Also presented will be the highlights of the world’s first demonstration of optical stochastic beam cooling and other selected results of IOTA’s broad experimental program.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXB02

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 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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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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MOPAB184

Unsupervised Learning Techniques for Tune Cleaning Measurement

624

H. Garcia Morales
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
E. Fol, R. Tomás García
CERN, Geneva, Switzerland

Precise measurements of tune and its stability are crucial for various optics analyses in the LHC, e.g. for the determination of the beta star using K-modulation. LHC BBQ system provides tune measurements online and stores the tune data. We apply unsupervised machine learning techniques on BBQ tune data in order to provide an automatic outlier detection method for better measurements of tune shifts and unexpected tune jitters.

Poster MOPAB184 [0.354 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB184

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paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 11 August 2021

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MOPAB185

HL-LHC Local Linear Optics Correction at the Interaction Regions

628

H. Garcia Morales
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
J.F. Cardona
UNAL, Bogota D.C, Colombia
R. Tomás García
CERN, Geneva, Switzerland

Magnetic imperfections of the HL-LHC inner triplet are expected to generate a significant \beta-beating. For that reason, improved local optics correction techniques at the low-\beta insertions is essential to ensure a high luminosity performance in the HL-LHC. In this study, we compare different strategies for local optics correction at the Interaction Regions with respect to their final performance in terms of residual \beta-beating. Supervised learning techniques are also explored to predict the inner triplet magnetic error contributions.

Poster MOPAB185 [0.469 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB185

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paper received ※ 14 May 2021 paper accepted ※ 10 June 2021 issue date ※ 31 August 2021

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MOPAB186

Comparison of Segment-by-Segment and Action-Phase-Jump Techniques in the Calculation of IR Local Corrections in LHC

632

H. Garcia Morales
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
J.F. Cardona
UNAL, Bogota D.C, Colombia
R. Tomás García
CERN, Geneva, Switzerland

The correction of the local optics at the Interaction Regions of the LHC is crucial to ensure a good performance of the machine. In this paper, we compare two different techniques for local optics correction: Action-Phase Jump and Segment-by-Segment techniques. The comparison is made in view of future machine configurations such as Run 3 LHC optics and HL-LHC optics.

Poster MOPAB186 [0.349 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB186

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paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 30 August 2021

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MOPAB230

The Optics Design for the Final Focus System of CLIC 380 GeV

748

A. Pastushenko, R. Tomás García
CERN, Geneva, Switzerland
A. Faus-Golfe
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

The first stage of the Compact Linear Collider (CLIC) is planned to be at the center-of-mass energy of 380 GeV. The final focus system (FFS) was re-optimized for this energy and for L* of 6 m (distance between the Interaction Point (IP) and the last quadrupole, QD0). Furthermore, the FFS optics was optimized for the vertical beta-function of 70 microns to approach the Hourglass effect limit. This paper reports the exploration of shortening the Final Doublet (FD) within the FFS to reduce the chromaticity. In addition, an alternative optics design is investigated with a different dispersion profile along the FFS, which outperforms the previous optics with the same β^*, increasing luminosity by 5 %.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB230

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 11 August 2021

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MOPAB231

Tunability Study of the Ultra-Low β* Optics at ATF2 with New Octupole Setup and Tuning Knobs

752

A. Pastushenko, R. Tomás García
CERN, Geneva, Switzerland
A. Faus-Golfe
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
K. Kubo, S. Kuroda, T. Naito, T. Okugi, N. Terunuma, R.J. Yang
KEK, Ibaraki, Japan

The main goal of the Accelerator Test Facility 2 (ATF2) is to demonstrate the feasibility of future linear colliders’ final focus systems. The Ultra-low β^* optics of ATF2 is designed to have the same chromaticity level as CLIC. To ease the tuning procedure, a pair of octupoles was installed in ATF2 in 2017. This paper reports the optimizations performed to the octupoles’ setup for Ultra-low β^* optics including the new alignment technique, based on the waist shift and the new tunning knobs constructed for this optics. The full tuning procedure including the static errors is simulated for this setup.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB231

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paper received ※ 19 May 2021 paper accepted ※ 28 July 2021 issue date ※ 12 August 2021

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MOPAB258

Corrections of Non-Linear Field Errors with Asymmetric Optics in LHC and HL-LHC Insertion Regions

817

J. Dilly, E.H. Maclean, R. Tomás García
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project, CERN and the german Federal Ministry of Education and Research.
Existing correction schemes to locally suppress resonance driving terms in the error-sensitive high-beta regions of the LHC and HL-LHC have operated on the assumption of symmetric beta-functions of the optics in the two rings. As this assumption can fail for a multitude of reasons, such as inherently asymmetric optics and unevenly distributed errors, an extension of this correction scheme has been developed removing the need for symmetry by operating on the two separate optics of the beams at the same time. Presented here is the impact of this novel approach on dynamic aperture as an important measure of particle stability.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB258

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paper received ※ 10 May 2021 paper accepted ※ 23 July 2021 issue date ※ 16 August 2021

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MOPAB259

Corrections of Feed-Down of Non-Linear Field Errors in LHC and HL-LHC Insertion Regions

821

J. Dilly, E.H. Maclean, R. Tomás García
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project, CERN and the german Federal Ministry of Education and Research.
The optics in the insertion regions of the LHC and its upgrade project the High Luminosity LHC (HL-LHC) are very sensitive to local magnetic errors, due to the extremely high beta-functions present. In collision optics, the non-zero closed orbit in the same region leads to a "feed-down" of high-order errors to lower orders, causing additional effects detrimental to beam lifetime. An extension to the proven method for correcting these errors by locally suppressing resonance driving terms has been undertaken, not only taking this feed-down into account, but also adding the possibility of utilizing it such that the powering of higher-order correctors will compensate for lower order errors. The impact of these corrections on measures of particle stability, namely dynamic aperture and amplitude detuning are presented in this contribution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB259

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paper received ※ 10 May 2021 paper accepted ※ 23 July 2021 issue date ※ 15 August 2021

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TUPAB004

Comparison of Accelerator Codes for Simulation of Lepton Colliders

1334

L. van Riesen-Haupt, H. Burkhardt, T.H.B. Persson, R. Tomás García
CERN, Geneva, Switzerland

This paper compares simulation results obtained with SAD, MAD-X and the PTC implementation in MADX for the design studies of the FCC-ee. On-momentum and off-momentum optics are explored for the various programs. Particle tracking with and without synchrotron radiation are used to compare amplitude detuning and emittance. Finally, this paper outlines how well-established SAD features such as tapering have recently been integrated into MADX.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB004

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paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 26 August 2021

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TUPAB005

Emittance Estimates for the Future Circular Collider

1338

L. van Riesen-Haupt, T.K. Charles, R. Tomás García, F. Zimmermann
CERN, Meyrin, Switzerland
T.K. Charles
The University of Liverpool, Liverpool, United Kingdom

The alignment strategy of the FCC-ee has a large impact on its luminosity. Larger alignment tolerances result in increased coupling and a subsequently higher vertical emittance. At the same time, tighter alignment tolerances around the 100 km ring are a major cost driver. This paper applies analytical emittance estimate methods to the FCC-ee and compares their predictions to data from simulations with different alignment tolerances. These methods can be used to help understand the impact of misalignments of certain magnet groups and to come up with an efficient alignment strategy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB005

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paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 26 August 2021

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TUPAB006

The Impact of Beam Position Monitor Tilts on Coupling Measurements

1342

L. van Riesen-Haupt, R. Tomás García
CERN, Geneva, Switzerland

The measurement and correction of coupling resonance driving terms is a key tool for improving the performance of synchrotrons. These terms are measured by exciting the beam and observing the subsequent motion in the horizontal and vertical planes through beam position monitors. This paper outlines the impact of tilt errors in these monitors to the distortion of the amount of coupling measured between the planes and how the computation of the resonance driving terms is affected by these tilts. It also attempts to use these results for mimicking tilt errors in simulations and discusses how discrepancies in measured resonance driving terms could be used to estimate the tilt errors that cause them.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB006

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paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 12 August 2021

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TUPAB009

SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data

1352

J. Keintzel, R. Tomás García
CERN, Geneva, Switzerland
H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang
KEK, Ibaraki, Japan

SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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TUPAB010

Impact of Bunch Current on Optics Measurements in SuperKEKB

1356

J. Keintzel, R. Tomás García, F. Zimmermann
CERN, Geneva, Switzerland
T. Ishibashi, H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, S. Terui, M. Tobiyama, R.J. Yang, D. Zhou
KEK, Ibaraki, Japan

SuperKEKB has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} and aims at reaching a target luminosity of about 6 × 10³⁵ \si{cm^-2s^-1}. To accomplish this goal it is planned to increase beam currents up to §I{3.6}{A} and §I{2.6}{A} for the positron and the electron ring, respectively. Increasing the beam currents and, in particular, the number of leptons per bunch, can impact the optics parameters obtained by turn-by-turn measurements, such as the betatron tune or phase advance. Optics measurements performed at various bunch currents can give first indications of possible intensity dependent effects. In this paper, the effect of varying bunch current on optics measurements at SuperKEKB is explored.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 30 August 2021

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TUPAB011

Momentum Compaction Factor Measurements in the Large Hadron Collider

1360

J. Keintzel, L. Malina, R. Tomás García
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) at CERN and its planned luminosity upgrade, the High Luminosity LHC (HL-LHC) demand well-controlled on- and off-momentum optics. Optics measurements are performed by analysing Turn-by-Turn (TbT) data of excited beams. Different techniques to measure the momentum compaction factor from these data are explored, taking into account the possibility to combine them with RF-voltage scans in future experiments.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB011

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 18 August 2021

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TUPAB013

A CLIC Dual Beam Delivery System for Two Interaction Regions

1364

V. Cilento, R. Tomás García
CERN, Geneva, Switzerland
A. Faus-Golfe
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

The Compact Linear Collider (CLIC) could provide e⁺e⁻ collisions in two detectors simultaneously possibly at a repetition frequency twice the design value. In this paper, a novel dual Beam Delivery System (BDS) design is presented including optics designs and the evaluation of luminosity performance with synchrotron radiation (SR) and solenoid effects for both energy stages of CLIC, 380 GeV and 3 TeV. In order to develop the novel optics design, parameters such as the longitudinal and the transverse detector separations were optimized. The luminosity performance of the novel CLIC scheme was evaluated by comparing the different BDS designs for both energy stages of CLIC. The dual CLIC BDS design provides a good luminosity and proves to be a viable candidate for future linear collider projects.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB013

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paper received ※ 17 May 2021 paper accepted ※ 09 June 2021 issue date ※ 31 August 2021

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TUPAB224

Non-Linear Variation of the Beta-Beating Measured From Amplitude

1949

T. Pugnat, B. Dalena
CEA-IRFU, Gif-sur-Yvette, France
A. Franchi
ESRF, Grenoble, France
R. Tomás García
CERN, Geneva, Switzerland

Accelerator physics needs advanced modeling and simulation techniques, for beam stability studies but also for the measurement of beam parameters like the Twiss parameters. A deeper understanding of magnetic field non-linearities effects will greatly help in the improvement of future circular collider design, performance, and diagnostics. This paper studies the variation of the \beta-beating with the action of the particle generated by non-linear Resonance Driving Terms, both from a theoretical and an experimental point of view.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB224

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paper received ※ 18 May 2021 paper accepted ※ 06 July 2021 issue date ※ 21 August 2021

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TUPAB231

Cooling of an Annular Beam by Using Nonlinear Effects

1968

F. Capoani, M. Giovannozzi, R. Tomás García
CERN, Geneva, Switzerland
A. Bazzani, F. Capoani
Bologna University, Bologna, Italy

In recent years, nonlinear effects have been used to modify the transverse beam distribution by crossing nonlinear resonances adiabatically. This allows generating transversally split beams, in which the initial single Gaussian is divided into several ones depending on the order and stability type of the resonance used. Nonlinear effects could be used to try and cool a beam by acting on its transverse beam distribution. In this paper, we present and discuss the special case of a beam with an annular distribution, showing how the resulting emittance could be reduced by means of nonlinear effects.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB231

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paper received ※ 10 May 2021 paper accepted ※ 16 June 2021 issue date ※ 21 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, Meyrin, 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, Meyrin, 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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WEPAB399

Applications of the Local Observable in Future Optics Measurements in HL-LHC and PETRA III

3642

A. Wegscheider, R. Tomás García
CERN, Geneva, Switzerland

Phase advances among four nearby beam position monitors in a circular accelerator can be used to calculate a local observable of quadrupolar lattice imperfections. This work explores the applicability of this local observable to two different circular accelerators: PETRA III, a synchrotron light source, and the LHC, a hadron collider as well as its upgrade project HL-LHC. MADX simulations for important optics settings are performed, showing that the local observable can detect strong error sources. This is of particular interest in important regions of the accelerators like the LHC’s interaction regions and PETRA III’s experimental hall.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB399

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 12 August 2021

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WEPAB400

Forced Coupling Resonance Driving Terms

3646

A. Wegscheider, R. Tomás García
CERN, Geneva, Switzerland

At the LHC, coupling is routinely measured using forced oscillations of the beam through excitation with an AC-dipole. The driving of the particle motion has an impact on the measurement of resonance driving terms. Recent findings suggest that the current models describing the forced motion are neglecting a local effect of the AC-dipole, creating a jump of the amplitude of the resonance driving terms. This work presents a study of the improvement of coupling measurements for typical LHC optics as well as its upgrade project HL-LHC, by using the new model.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB400

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 20 August 2021

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THXA07

Driven 3D Beam Oscillations for Optics Measurements in Synchrotrons

3704

L. Malina, J.M. Coello de Portugal, H. Timko, R. Tomás García
CERN, Geneva, Switzerland

Optics measurements in storage rings employ turn-by-turn data of transversely excited beams. Traditionally, to measure chromatic properties, the relative momentum is changed step-wise, which is time-consuming and almost impractical during the energy ramp. We present an optics measurement method based on adiabatic simultaneous 3-dimensional beam excitation, which is more time-efficient and well fitted for the energy ramp. This method was successfully demonstrated in the LHC utilising AC-dipoles in combination either with a slow RF-frequency modulation or a driven RF-phase modulation close to the synchrotron frequency. Faster longitudinal oscillations improve the accuracy of optics parameters inferred from the synchro-betatron sidebands. This paper reports on the experimental demonstration of optics measurements based on 3D driven beam excitations and the plans for LHC Run 3.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA07

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 11 August 2021

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THPAB055

Reconstruction of Linear Optics Observables Using Supervised Learning

3875

E. Fol, H. Garcia, R. Tomás García
CERN, Geneva, Switzerland

In the LHC, most of the optical functions can be obtained from turn-by-turn beam centroid data. However, the measurement of such observables as β^* and the dispersion function require special dedicated techniques and additional operational time. In this work, we propose an alternative approach to estimate these observables using supervised machine learning, in case the dedicated measurements are not available but turn-by-turn data are. The performance of developed estimators is demonstrated on LHC simulations. Comparison to traditional techniques for the computation of beta-function will be also provided.

Poster THPAB055 [0.713 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB055

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paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 15 August 2021

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THPAB068

Denoising of Optics Measurements Using Autoencoder Neural Networks

3915

E. Fol, R. Tomás García
CERN, Geneva, Switzerland

Noise artefacts can appear in optics measurements data due to instrumentation imperfections or uncertainties in the applied analysis methods. A special type of semi-supervised neural networks, autoencoders, are widely applied to denoising tasks in image and signal processing as well as to generative modeling. Recently, an autoencoder-based approach for denoising and reconstruction of missing data has been developed to improve the quality of phase measurements obtained from harmonic analysis of LHC turn-by-turn data. We present the results achieved on simulations demonstrating the potential of the new method and discuss the effect of the noise in light of optics corrections computed from the cleaned data.

Poster THPAB068 [0.881 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB068

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paper received ※ 19 May 2021 paper accepted ※ 13 July 2021 issue date ※ 02 September 2021

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THPAB168

Optics Measurement by Excitation of Betatron Oscillations in the CERN PSB

4078

E.H. Maclean, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, J. Dilly, E. Fol, H. Garcia Morales, M. Hofer, J. Keintzel, M. Le Garrec, T.E. Levens, L. Malina, T.H.B. Persson, T. Prebibaj, E. Renner, P.K. Skowroński, F. Soubelet, R. Tomás García, A. Wegscheider, L. van Riesen-Haupt
CERN, Meyrin, Switzerland

Optics measurement from analysis of turn-by-turn BPM data of betatron oscillations excited with a kicker magnet has been employed very successfully in many machines but faces particular challenges in the CERN PSB where BPM to BPM phase advances are sub-optimal for optics reconstruction. Experience using turn-by-turn oscillation data for linear optics measurements during PSB commissioning in2021 is presented, with implications for the prospect of such techniques in the PSB more generally.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB168

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 27 August 2021

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THPAB169

A Mechanism for Emittance Growth Based on Non-Linear Islands in LHC

4082

E.H. Maclean, M. Giovannozzi, T.H.B. Persson, R. Tomás García
CERN, Geneva, Switzerland

Landau octupoles are used in the LHC to prevent coherent instabilities of the circulating beam. The reduction of their strength occurring during the energy ramp can transport particles in nonlinear islands to larger amplitude. This has the potential to lead to emittance growth and to beam-losses. Beam-based studies and simulations of emittance growth during Landau octupole ramps performed in the LHC are presented to explore this mechanism in more detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB169

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paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 14 August 2021

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