IPAC2018 - List of Keywords (octupole)

Paper	Title	Other Keywords	Page
MOPMF041	Refining the HL-LHC Operational Settings with Inputs From Dynamic Aperture Simulations: A Progress Report	luminosity, operation, dynamic-aperture, experiment	188
	N. Karastathis, R. De Maria, S.D. Fartoukh, Y. Papaphilippou, D. Pellegrini CERN, Geneva, Switzerland
	Recent Dynamic Aperture (DA) simulations aimed at providing guidance for the latest updates of the operational scenario for the High Luminosity upgrade of the LHC. The impact of the increased chromaticity and octupole current has been assessed considering the latest updates of the optics. Additional means to improve the lifetime, such as tune optimization, have been identified and deployed. We also briefly discuss the impact of delivering high luminosity to the LHCb experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF041
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MOPMF058	Status of the LHC Schottky Monitors	emittance, injection, sextupole, damping	247
	T. Tydecks, D. Alves, T.E. Levens, M. Wendt, J. Wenninger CERN, Geneva, Switzerland
	The Large Hadron Collider (LHC) features four transverse Schottky monitors detecting Schottky noise from the beam. From the Schottky noise signal, beam properties like tune, chromaticity, and bunch by bunch relative emittances, can be extracted. Being a non-destructive and purely parasitic method of measurement, the Schottky system is of great interest for real-time determination of beam chromaticities especially. Studies, including a dedicated machine development shift as well as parasitic measurements, concerning its capability to accurately measure the beam chromaticities are presented.
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MOPMF069	The High Energy LHC Beam-Beam Effects studies	beam-beam-effects, collider, dynamic-aperture, experiment	285
	T. Pieloni, J. Barranco García, L. Rivkin, C. Tambasco EPFL, Lausanne, Switzerland D. Amorim, S. A. Antipov, X. Buffat, B. Salvant, F. Zimmermann CERN, Geneva, Switzerland
	Funding: This work is supported by the Swiss State Secretariat for Education, Research and Innovation SERI. We present in this paper the studies of beam-beam effects for the High Energy Large Hadron Collider. We will describe and review the different aspects of beam-beam interactions (i.e. orbit effects, Landau damping, compensation schemes and operational set-up). An operational scenario for the collider will also be given as a result of the study.
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TUPAF051	Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS	extraction, multipole, optics, simulation	822
	L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard CERN, Geneva, Switzerland K.A. Brown BNL, Upton, Long Island, New York, USA
	Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.
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TUPAL064	Extended-Domain Tune-Scans for the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects	resonance, lattice, dynamic-aperture, beam-beam-effects	1163
	D. Kaltchev TRIUMF, Vancouver, Canada N. Karastathis, Y. Papaphilippou, D. Pellegrini CERN, Geneva, Switzerland
	We report simulations of the HL-LHC dynamic aperture (DA) at collision energy in the presence of beam-beam effects (weak-strong approximation) aiming to determine its dependence on the working point in tune space. Both linear domains working points are explored, spanning over (0.028 – 0.33) in horizontal tune, and two-dimensional ones which focus on more promising sub-regions near the diagonal. The range of parameters, such as bunch intensity and emittance, are chosen to correspond to the more important HL-LHC scenarios. A comparison with the LHC as built is also made. Direct benefit from these studies is the possible identification of working points alternative to the nominal one (in terms of dynamic aperture). They also help to understand the dependence of DA on particular resonance lines present in the vicinity of the footprint. In this work, the necessary resources were provided by the LHC@home project, based on the BOINC-SixTrack platform for distributed Computing.
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WEYGBE4	Low-Impedance Collimators for HL-LHC	impedance, operation, collimation, luminosity	1794
	S. A. Antipov, N. Biancacci, R. Bruce, A. Mereghetti, D. Mirarchi, E. Métral, S. Redaelli, B. Salvant CERN, Geneva, Switzerland D. Amorim Université Grenoble Alpes, Grenoble, France
	The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will double its beam intensity for the needs of High Energy Physics frontier. This increase requires a reduction of the machine's impedance to ensure the coherent stability of the beams until they are put in collision. A major part of the impedance is the resistive wall contribution of the collimators. To reduce this contribution several coating options have been proposed. We have studied numerically the effect of the novel coatings on the beam stability. The results show that a decrease of up to 30% of the machine impedance and a reduction of up to 120 A in the stabilizing octupole current threshold can be achieved by coating the secondary collimators with Molybdenum. Half of that improvement can be obtained by coating the jaws of a subset of four collimators identified as the highest contributors to machine impedance. The installation of this subset of low-impedance collimators is planned for the Long Shutdown 2 in 2019-2020.
	Slides WEYGBE4 [5.719 MB]
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WEPAL047	Online Optimisation of the MAX IV 3 GeV Ring Dynamic Aperture	dynamic-aperture, sextupole, optics, storage-ring	2281
	D.K. Olsson MAX IV Laboratory, Lund University, Lund, Sweden
	In order to improve the resilience of the MAX IV 3 GeV ring's beam to a horizontal dipole kick while at the design tunes (42.20, 16.28) the optimisation algorithm RCDS (Robust Conjugate Direction Search) was deployed. The algorithm was able to increase the horizontal acceptance by finding new settings for the sextupole and octupole magnets, whilst leaving the vertical acceptance virtually unchanged. Additionally, the optimisation increased the momentum acceptance of the lattice, increasing beam lifetime.
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WEPMK009	Status of the ESRF-EBS Magnets	quadrupole, SRF, dipole, sextupole	2648
	C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White ESRF, Grenoble, France
	The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.
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THYGBD4	Landau Damping by Electron Lenses	electron, proton, collider, betatron	2921
	A.V. Burov, Y.I. Alexahin, V.D. Shiltsev, A. Valishev Fermilab, Batavia, Illinois, USA
	Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important to note that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.
	Slides THYGBD4 [4.502 MB]
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THPAF034	Studies of Horizontal Instabilities in the CERN SPS	simulation, optics, damping, impedance	3032
	M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk CERN, Geneva, Switzerland U. van Rienen Rostock University, Faculty of Engineering, Rostock, Germany
	In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.
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THPAF035	Single-Collimator Tune Shift Measurement of the Three-Stripe Collimator at the LHC	impedance, luminosity, feedback, hadron	3036
	S. A. Antipov University of Chicago, Chicago, Illinois, USA D. Amorim, N. Biancacci, L.R. Carver, G. Mazzacano, A. Mereghetti, E. Métral, S. Redaelli, B. Salvant, D. Valuch CERN, Geneva, Switzerland
	Several options of low resistivity coating have been proposed for the collimator upgrade of the Large Hadron Collider. In order to study their effect on the beam dynamics a special collimator has been built and installed in the machine. Its jaws are coated with three different materials and can be moved transversely to selectively expose the beam to the chosen coating. We have measured the resistive wall tune shifts of each coating material and compared them with that of a standard Carbon Fibre Composite (CFC) collimator jaw. A resolution of the tune shift of the order of 10^-5 has been achieved in the measurement. The results show a significant reduction of the resistive wall tune shift with novel materials. The largest improvement is obtained with a 5 μm Molybdenum coating of a Molybdenum-Graphite jaw. The observed tune shifts show a good agreement with the impedance model and the bench impedance and resistivity measurements. Obtained results can be used to further improve the precision of the impedance model.
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THPAF059	Ultra Compact Symplectic Scheme for Fast Multi-Particle Tracking	lattice, flattop, target, sextupole	3107
	K. Skoufaris, Y. Papaphilippou, D. Pellegrini CERN, Geneva, Switzerland
	A versatile symplectic integration scheme has been developed in order to produce simplified versions of non linear lattices, preserving fundamental non-linear properties such as the detuning with amplitude and energy, in addition to the linear transport. The method has been applied to the LHC and benchmarked against tracking simulations with Sixtrack. This reduced lattice is made available as a refined replacement of the simple rotation matrix often used in multi-particle studies requiring a fast beam transport routine.
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THPAF064	Beam Dynamics with Covariant Hamiltonians	space-charge, multipole, wakefield, software	3123
	B.T. Folsom, E. Laface ESS, Lund, Sweden
	We demonstrate covariant beam-physics simulation through multipole magnets using Hamiltonians relying on canonical momentum. Space-charge integration using the Lienard–Wiechert potentials is also discussed. This method is compared with conventional nonlinear Lie-operator tracking and the TraceWin software package.
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THPAF074	Landau Damping Studies for the FCC: Octupole Magnets, Electron Lens and Beam-Beam Effects	damping, flattop, feedback, betatron	3150
	C. Tambasco, J. Barranco García, T. Pieloni, L. Rivkin EPFL, Lausanne, Switzerland S. Arsenyev, X. Buffat, D. Schulte CERN, Geneva, Switzerland
	Funding: This work is supported by the Swiss State Secretariat for Education, Research and Innovation SERI. Stability studies for the FCC-hh operational cycle are explored using Landau octupoles and electron lenses alone and in the presence of long-range as well as head-on beam-beam effects. Pros and cons of the various methods are compared and an optimum operational scenario to guarantee the maximum stability is proposed.
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THPAF079	Landau Damping and Tune-Spread Requirements for Transverse Beam Stability	simulation, damping, impedance, quadrupole	3168
	V. Kornilov, O. Boine-Frankenheim GSI, Darmstadt, Germany
	Passive mitigation methods are effective cures for collective instabilities in ring accelerators. For decades, octupole magnets have been used as an established and well-understood passive mitigation method. Present and the future accelerator facilities, like FAIR or FCC, impose new challenges on the passive mitigation due to higher energies and smaller beam emittances. Lattice resonances usually restrict the tolerable tune-spreads which are essential for the passive mitigation methods. We study the stability of transverse bunch oscillations provided by octupole magnets and radio-frequency quadrupoles. The special focus of our study is on the interplay and role of decoherence, phase-mixing and Landau damping for the different mitigation schemes. Particle tracking simulations are performed and the tune spreads for the different mechanisms are compared with each other and also with analytical dispersion relations.
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THPAK036	Accurate Modeling of Fringe Field Effects on Nonlinear Integrable Optics in IOTA	optics, quadrupole, betatron, lattice	3294
	C.E. Mitchell, R.D. Ryne LBNL, Berkeley, California, USA F.H. O'Shea RadiaBeam, Santa Monica, California, USA
	Funding: This work is supported by the U.S. Department of Energy, Office of High Energy Physics. The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Uncontrolled nonlinear effects resulting from magnetic fringe fields can affect the integrability of particle motion, and long-term numerical tracking requires an accurate representation of these effects. Surface fitting algorithms provide a robust and reliable method for extracting this information from 3-dimensional magnetic field data provided on a grid. These algorithms are applied to investigate the unique nonlinear magnetic insert of the IOTA ring, and consequences of the fringe fields to the long-term dynamics of the beam are discussed.
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THPAK082	Simulation of Perturbative Effects in IOTA	simulation, lattice, optics, emittance	3422
	C.C. Hall, D.L. Bruhwiler, N.M. Cook, J.P. Edelen, S.D. Webb RadiaSoft LLC, Boulder, Colorado, USA
	The Integrable Optics Test Accelerator (IOTA) is being commissioned at Fermi National Laboratory for study of the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The nonlinear element should provide suppression of instabilities through nonlinear decoherence. We examine the case of a bunch injected off-axis and the resulting damping of centroid oscillations from decoherence. A simple model of the damping is described and compared to simulation.
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THPAK090	Symbolic Presentation of Nonlinear Dynamic Systems in Terms of Lego-Objects	quadrupole, database, controls, dipole	3441
	E. Sboeva, E. Krushinevskii Saint Petersburg State University, Saint Petersburg, Russia S.N. Andrianov, A.N. Ivanov St. Petersburg State University, St. Petersburg, Russia
	In this paper we propose a symbolic representation of the solutions of the equations of evolution of dynamical systems in the framework of matrix formalism and Lie algebra for a number of elements of the accelerator (in particular, dipole, quadrupole and octupole) up to the 4th order. The considered solutions are Lego-objects, which are include into the general scheme of the representation beam dynamics. It allows modeling of schemes of various accelerators and thereby to increasing performance of parametrical optimization. Let us note that the symbolic approach to solving such problems is more preferable than the numerical one, which is widely used. This leads to a reduction in the time and resources spent on solving optimization problems, as well as the ability to create universal Lego objects. The paper considers the verification of the obtained formulas from the experimental data. The corresponding Lego objects are the main components of the special software for both symbolic and numerical dynamics analysis. This software is planned to be used for modeling within the framework of the NICA accelerator project. S.N. Andrianov. Dynamic Modeling of Particle Beam Control Systems. Saint Petersburg State University, 2002.
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THPAK099	The Influence of Higher Order Multipoles of IR Magnets on Luminosity for SuperKEKB	sextupole, luminosity, multipole, coupling	3463
	K. Hirosawa, T. Okada Sokendai, Ibaraki, Japan N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan K. Ohmi, N. Ohuchi, D. Zhou KEK, Ibaraki, Japan
	SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them.
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THPAK134	Dynamic Equations: The Matrix Representation of Beam Dynamic Equations Instead of Tensor Description	controls, sextupole, operation, software	3554
	S.N. Andrianov, A.N. Ivanov, N.V. Kulabukhova St. Petersburg State University, St. Petersburg, Russia Chang, S. Chang KAIST, Daejeon, Republic of Korea J. Choi CAPP/IBS, Daejeon, Republic of Korea E. Krushinevskii, E. Sboeva Saint Petersburg State University, Saint Petersburg, Russia
	In this paper we consider mathematical and computer modeling of nonlinear dynamics of particle beams in cyclic accelerators in terms of the matrix representation of the corresponding nonlinear differential equations. The proposed approach is different from the usual presentations of non-linear equations in the form of Taylor series. In the paper, we use the coefficients representation in the form of two-dimensional matrices. The similar approach allows us not only to significantly reduce the time spent on modeling beam dynamics but use symbolic mathematics to calculate the necessary two-dimensional matrices. This method demonstrates the effectiveness when solving problems of dynamics problems and optimization of control systems, and for evaluating the influence of various effects on the dynamics of the beam (including taking into account the spin). Using the tools of symbolic computations not only significantly increases the computational efficiency of the method, but also allows you to create databases of "ready-made" transformations (Lego-objects), which greatly simplify the process of modeling particle dynamics. Examples of solving practical problems are given.
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THPAK141	Initial Tests of Nonlinear Quasi-Integrable Optics at the University of Maryland Electron Ring	electron, optics, experiment, simulation	3581
	H. Baumgartner, B.L. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew, K.J. Ruisard UMD, College Park, Maryland, USA
	Funding: Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program. An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring.
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THPAK143	Tuning Low-Current Beam for Nonlinear Quasi-Integrable Optics Experiments at the University of Maryland Electron Ring	lattice, optics, experiment, quadrupole	3585
	K.J. Ruisard, H. Baumgartner, B.L. Beaudoin, S. Bernal, B. M. Cannon, L. Dovlatyan, I. Haber, T.W. Koeth UMD, College Park, Maryland, USA
	Funding: Travel was supported by the NSF, the APS DPB, and TRIUMF. Funding for the work was provided through DOE-HEP Award DESC0010301, NSF Award PHY1414681 and the NSF GRFP program. Design of accelerator lattices with nonlinear integrable optics is a novel approach to suppress transverse resonances and may be crucial for enabling low-loss high-intensity beam transport. Lattices with large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, have reduced response to resonant driving perturbations []. This paper describes preparations for tests of a quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). The planned tests employ a low-current highemittance beam with low space charge tune shift (∼ 0.005) to probe the dynamics of a lattice with large external tune spread (∼ 0.26). V. Danilov and S. Nagaitsev, Nonlinear accelerator lattices with one and two analytic invariants, PRSTAB, 13, 084002, 2010.
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THPMF002	Studies for Injection with a Pulsed Multipole Kicker at ALBA	injection, kicker, storage-ring, lattice	4030
	G. Benedetti, U. Iriso, M. Pont, D. Ramos Santesmases ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain E. Ahmadi ILSF, Tehran, Iran
	Injection into the ALBA storage ring presently uses a conventional local injection bump with four dipole kickers. However, following the promising results of the first tests with single multipole kicker injection at other light sources, studies to implement this new injection scheme have been started for ALBA. Two possible designs for the kicker have been considered: a pure octupole and a non-linear magnet similar to the BESSY type. A comparison between the expected performances of the two kicker designs has been carried out in terms of injection efficiency and transparency for the users. This paper summarises the beam dynamics results from multi-particle tracking simulations and the proposed kicker magnet design.
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THPMF070	Non-Linear Optics and Low Alpha Operation at the Storage Ring KARA at KIT	wiggler, operation, resonance, injection	4235
	A.I. Papash, E. Blomley, M. Brosi, J. Gethmann, B. Kehrer, A.-S. Müller, M. Schuh, P. Schönfeldt, J.L. Steinmann KIT, Karlsruhe, Germany
	The storage ring Karlsruhe Research Accelerator (KARA) at KIT operate in a wide energy range from 0.5 to 2.5 GeV. Different non-linear effects, in particular, residual octupole components of the magnetic field of the CATACT wiggler at high field level (2.5 T), proximity of the working point to a vertical sextupole resonance Qy=8/3 and weak coupling octupole resonance 2Qx+2Qy=19, high chromaticity, etc. decrease the beam life time. This is because of the reduced dynamic aperture and momentum acceptance for off-momentum particles. A new operation point at high vertical tune Qy=2.81 was tested. For this, injection and ramping tables have been modified. First the values were optimized by simulations, then during beam tests, to minimize betatron tune shaking during beam-energy ramps. It stabilized high-current beams by the fast-feedback system the whole process: injection at 0.5 GeV, ramping, and operation at 1.3 GeV cycles. It essentially improved life time and beam current. In addition, new low-alpha tables have been created and tested, resulting in the reduction of the momentum compaction factor to 10^-4. Short bunch operation at 0.5GeV injection energy was also tested successfully.
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Paper

Title

Other Keywords

Page

MOPMF041

Refining the HL-LHC Operational Settings with Inputs From Dynamic Aperture Simulations: A Progress Report

luminosity, operation, dynamic-aperture, experiment

188

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

Recent Dynamic Aperture (DA) simulations aimed at providing guidance for the latest updates of the operational scenario for the High Luminosity upgrade of the LHC. The impact of the increased chromaticity and octupole current has been assessed considering the latest updates of the optics. Additional means to improve the lifetime, such as tune optimization, have been identified and deployed. We also briefly discuss the impact of delivering high luminosity to the LHCb experiment.

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MOPMF058

Status of the LHC Schottky Monitors

emittance, injection, sextupole, damping

247

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

The Large Hadron Collider (LHC) features four transverse Schottky monitors detecting Schottky noise from the beam. From the Schottky noise signal, beam properties like tune, chromaticity, and bunch by bunch relative emittances, can be extracted. Being a non-destructive and purely parasitic method of measurement, the Schottky system is of great interest for real-time determination of beam chromaticities especially. Studies, including a dedicated machine development shift as well as parasitic measurements, concerning its capability to accurately measure the beam chromaticities are presented.

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MOPMF069

The High Energy LHC Beam-Beam Effects studies

beam-beam-effects, collider, dynamic-aperture, experiment

285

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

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

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TUPAF051

Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS

extraction, multipole, optics, simulation

822

L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard
CERN, Geneva, Switzerland
K.A. Brown
BNL, Upton, Long Island, New York, USA

Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.

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TUPAL064

Extended-Domain Tune-Scans for the HL-LHC Dynamic Aperture in Presence of Beam-Beam Effects

resonance, lattice, dynamic-aperture, beam-beam-effects

1163

D. Kaltchev
TRIUMF, Vancouver, Canada
N. Karastathis, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

We report simulations of the HL-LHC dynamic aperture (DA) at collision energy in the presence of beam-beam effects (weak-strong approximation) aiming to determine its dependence on the working point in tune space. Both linear domains working points are explored, spanning over (0.028 – 0.33) in horizontal tune, and two-dimensional ones which focus on more promising sub-regions near the diagonal. The range of parameters, such as bunch intensity and emittance, are chosen to correspond to the more important HL-LHC scenarios. A comparison with the LHC as built is also made. Direct benefit from these studies is the possible identification of working points alternative to the nominal one (in terms of dynamic aperture). They also help to understand the dependence of DA on particular resonance lines present in the vicinity of the footprint. In this work, the necessary resources were provided by the LHC@home project, based on the BOINC-SixTrack platform for distributed Computing.

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WEYGBE4

Low-Impedance Collimators for HL-LHC

impedance, operation, collimation, luminosity

1794

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

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

Slides WEYGBE4 [5.719 MB]

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WEPAL047

Online Optimisation of the MAX IV 3 GeV Ring Dynamic Aperture

dynamic-aperture, sextupole, optics, storage-ring

2281

D.K. Olsson
MAX IV Laboratory, Lund University, Lund, Sweden

In order to improve the resilience of the MAX IV 3 GeV ring's beam to a horizontal dipole kick while at the design tunes (42.20, 16.28) the optimisation algorithm RCDS (Robust Conjugate Direction Search) was deployed. The algorithm was able to increase the horizontal acceptance by finding new settings for the sextupole and octupole magnets, whilst leaving the vertical acceptance virtually unchanged. Additionally, the optimisation increased the momentum acceptance of the lattice, increasing beam lifetime.

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WEPMK009

Status of the ESRF-EBS Magnets

quadrupole, SRF, dipole, sextupole

2648

C. Benabderrahmane, J.C. Biasci, J-F. B. Bouteille, J. Chavanne, L. Eybert, L. Goirand, G. Le Bec, L. Lefebvre, S.M. Liuzzo, D. Martin, C. Penel, P. Raimondi, J.-L. Revol, F. Villar, S.M. White
ESRF, Grenoble, France

The ESRF-EBS (Extremely Brilliant Source) is an upgrade project planned at the European Synchrotron Radiation Facility (ESRF) in the period 2015-2022. A new storage ring will be built, aiming to decrease the horizontal emittance and to improve the brilliance and coherence of the X-ray beams. The lattice of the new storage ring relies on magnets with demanding specifications: dipoles with longitudinal gradient (field ranging from 0.17 T up to 0.67 T), strong quadrupoles (up to 90 T/m), combined function dipole-quadrupoles with high gradient (0.57 T and 37 T/m), strong sextupoles and octupoles. The design of these magnets is based on innovative solutions; in particular, the longitudinal gradient dipoles are permanent magnets and the combined dipole-quadrupoles are single-sided devices. The longitudinal gradient dipoles have been assembled and measured in house. The design of the magnets, production status and magnetic measurement results will be presented.

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THYGBD4

Landau Damping by Electron Lenses

electron, proton, collider, betatron

2921

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

Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important to note that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.

Slides THYGBD4 [4.502 MB]

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THPAF034

Studies of Horizontal Instabilities in the CERN SPS

simulation, optics, damping, impedance

3032

M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk
CERN, Geneva, Switzerland
U. van Rienen
Rostock University, Faculty of Engineering, Rostock, Germany

In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.

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THPAF035

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

impedance, luminosity, feedback, hadron

3036

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

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

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THPAF059

Ultra Compact Symplectic Scheme for Fast Multi-Particle Tracking

lattice, flattop, target, sextupole

3107

K. Skoufaris, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

A versatile symplectic integration scheme has been developed in order to produce simplified versions of non linear lattices, preserving fundamental non-linear properties such as the detuning with amplitude and energy, in addition to the linear transport. The method has been applied to the LHC and benchmarked against tracking simulations with Sixtrack. This reduced lattice is made available as a refined replacement of the simple rotation matrix often used in multi-particle studies requiring a fast beam transport routine.

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THPAF064

Beam Dynamics with Covariant Hamiltonians

space-charge, multipole, wakefield, software

3123

B.T. Folsom, E. Laface
ESS, Lund, Sweden

We demonstrate covariant beam-physics simulation through multipole magnets using Hamiltonians relying on canonical momentum. Space-charge integration using the Lienard–Wiechert potentials is also discussed. This method is compared with conventional nonlinear Lie-operator tracking and the TraceWin software package.

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THPAF074

Landau Damping Studies for the FCC: Octupole Magnets, Electron Lens and Beam-Beam Effects

damping, flattop, feedback, betatron

3150

C. Tambasco, J. Barranco García, T. Pieloni, L. Rivkin
EPFL, Lausanne, Switzerland
S. Arsenyev, X. Buffat, D. Schulte
CERN, Geneva, Switzerland

Funding: This work is supported by the Swiss State Secretariat for Education, Research and Innovation SERI.
Stability studies for the FCC-hh operational cycle are explored using Landau octupoles and electron lenses alone and in the presence of long-range as well as head-on beam-beam effects. Pros and cons of the various methods are compared and an optimum operational scenario to guarantee the maximum stability is proposed.

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THPAF079

Landau Damping and Tune-Spread Requirements for Transverse Beam Stability

simulation, damping, impedance, quadrupole

3168

V. Kornilov, O. Boine-Frankenheim
GSI, Darmstadt, Germany

Passive mitigation methods are effective cures for collective instabilities in ring accelerators. For decades, octupole magnets have been used as an established and well-understood passive mitigation method. Present and the future accelerator facilities, like FAIR or FCC, impose new challenges on the passive mitigation due to higher energies and smaller beam emittances. Lattice resonances usually restrict the tolerable tune-spreads which are essential for the passive mitigation methods. We study the stability of transverse bunch oscillations provided by octupole magnets and radio-frequency quadrupoles. The special focus of our study is on the interplay and role of decoherence, phase-mixing and Landau damping for the different mitigation schemes. Particle tracking simulations are performed and the tune spreads for the different mechanisms are compared with each other and also with analytical dispersion relations.

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THPAK036

Accurate Modeling of Fringe Field Effects on Nonlinear Integrable Optics in IOTA

optics, quadrupole, betatron, lattice

3294

C.E. Mitchell, R.D. Ryne
LBNL, Berkeley, California, USA
F.H. O'Shea
RadiaBeam, Santa Monica, California, USA

Funding: This work is supported by the U.S. Department of Energy, Office of High Energy Physics.
The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Uncontrolled nonlinear effects resulting from magnetic fringe fields can affect the integrability of particle motion, and long-term numerical tracking requires an accurate representation of these effects. Surface fitting algorithms provide a robust and reliable method for extracting this information from 3-dimensional magnetic field data provided on a grid. These algorithms are applied to investigate the unique nonlinear magnetic insert of the IOTA ring, and consequences of the fringe fields to the long-term dynamics of the beam are discussed.

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THPAK082

Simulation of Perturbative Effects in IOTA

simulation, lattice, optics, emittance

3422

C.C. Hall, D.L. Bruhwiler, N.M. Cook, J.P. Edelen, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA

The Integrable Optics Test Accelerator (IOTA) is being commissioned at Fermi National Laboratory for study of the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The nonlinear element should provide suppression of instabilities through nonlinear decoherence. We examine the case of a bunch injected off-axis and the resulting damping of centroid oscillations from decoherence. A simple model of the damping is described and compared to simulation.

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THPAK090

Symbolic Presentation of Nonlinear Dynamic Systems in Terms of Lego-Objects

quadrupole, database, controls, dipole

3441

E. Sboeva, E. Krushinevskii
Saint Petersburg State University, Saint Petersburg, Russia
S.N. Andrianov, A.N. Ivanov
St. Petersburg State University, St. Petersburg, Russia

In this paper we propose a symbolic representation of the solutions of the equations of evolution of dynamical systems in the framework of matrix formalism and Lie algebra for a number of elements of the accelerator (in particular, dipole, quadrupole and octupole) up to the 4th order. The considered solutions are Lego-objects*, which are include into the general scheme of the representation beam dynamics. It allows modeling of schemes of various accelerators and thereby to increasing performance of parametrical optimization. Let us note that the symbolic approach to solving such problems is more preferable than the numerical one, which is widely used. This leads to a reduction in the time and resources spent on solving optimization problems, as well as the ability to create universal Lego objects. The paper considers the verification of the obtained formulas from the experimental data. The corresponding Lego objects are the main components of the special software for both symbolic and numerical dynamics analysis. This software is planned to be used for modeling within the framework of the NICA accelerator project.
*S.N. Andrianov. Dynamic Modeling of Particle Beam Control Systems.
Saint Petersburg State University, 2002.

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THPAK099

The Influence of Higher Order Multipoles of IR Magnets on Luminosity for SuperKEKB

sextupole, luminosity, multipole, coupling

3463

K. Hirosawa, T. Okada
Sokendai, Ibaraki, Japan
N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
K. Ohmi, N. Ohuchi, D. Zhou
KEK, Ibaraki, Japan

SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them.

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THPAK134

Dynamic Equations: The Matrix Representation of Beam Dynamic Equations Instead of Tensor Description

controls, sextupole, operation, software

3554

S.N. Andrianov, A.N. Ivanov, N.V. Kulabukhova
St. Petersburg State University, St. Petersburg, Russia
Chang, S. Chang
KAIST, Daejeon, Republic of Korea
J. Choi
CAPP/IBS, Daejeon, Republic of Korea
E. Krushinevskii, E. Sboeva
Saint Petersburg State University, Saint Petersburg, Russia

In this paper we consider mathematical and computer modeling of nonlinear dynamics of particle beams in cyclic accelerators in terms of the matrix representation of the corresponding nonlinear differential equations. The proposed approach is different from the usual presentations of non-linear equations in the form of Taylor series. In the paper, we use the coefficients representation in the form of two-dimensional matrices. The similar approach allows us not only to significantly reduce the time spent on modeling beam dynamics but use symbolic mathematics to calculate the necessary two-dimensional matrices. This method demonstrates the effectiveness when solving problems of dynamics problems and optimization of control systems, and for evaluating the influence of various effects on the dynamics of the beam (including taking into account the spin). Using the tools of symbolic computations not only significantly increases the computational efficiency of the method, but also allows you to create databases of "ready-made" transformations (Lego-objects), which greatly simplify the process of modeling particle dynamics. Examples of solving practical problems are given.

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THPAK141

Initial Tests of Nonlinear Quasi-Integrable Optics at the University of Maryland Electron Ring

electron, optics, experiment, simulation

3581

H. Baumgartner, B.L. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew, K.J. Ruisard
UMD, College Park, Maryland, USA

Funding: Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program.
An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring.

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THPAK143

Tuning Low-Current Beam for Nonlinear Quasi-Integrable Optics Experiments at the University of Maryland Electron Ring

lattice, optics, experiment, quadrupole

3585

K.J. Ruisard, H. Baumgartner, B.L. Beaudoin, S. Bernal, B. M. Cannon, L. Dovlatyan, I. Haber, T.W. Koeth
UMD, College Park, Maryland, USA

Funding: Travel was supported by the NSF, the APS DPB, and TRIUMF. Funding for the work was provided through DOE-HEP Award DESC0010301, NSF Award PHY1414681 and the NSF GRFP program.
Design of accelerator lattices with nonlinear integrable optics is a novel approach to suppress transverse resonances and may be crucial for enabling low-loss high-intensity beam transport. Lattices with large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, have reduced response to resonant driving perturbations [*]. This paper describes preparations for tests of a quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). The planned tests employ a low-current highemittance beam with low space charge tune shift (∼ 0.005) to probe the dynamics of a lattice with large external tune spread (∼ 0.26).
* V. Danilov and S. Nagaitsev, Nonlinear accelerator lattices
with one and two analytic invariants, PRSTAB, 13, 084002, 2010.

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THPMF002

Studies for Injection with a Pulsed Multipole Kicker at ALBA

injection, kicker, storage-ring, lattice

4030

G. Benedetti, U. Iriso, M. Pont, D. Ramos Santesmases
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
E. Ahmadi
ILSF, Tehran, Iran

Injection into the ALBA storage ring presently uses a conventional local injection bump with four dipole kickers. However, following the promising results of the first tests with single multipole kicker injection at other light sources, studies to implement this new injection scheme have been started for ALBA. Two possible designs for the kicker have been considered: a pure octupole and a non-linear magnet similar to the BESSY type. A comparison between the expected performances of the two kicker designs has been carried out in terms of injection efficiency and transparency for the users. This paper summarises the beam dynamics results from multi-particle tracking simulations and the proposed kicker magnet design.

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THPMF070

Non-Linear Optics and Low Alpha Operation at the Storage Ring KARA at KIT

wiggler, operation, resonance, injection

4235

A.I. Papash, E. Blomley, M. Brosi, J. Gethmann, B. Kehrer, A.-S. Müller, M. Schuh, P. Schönfeldt, J.L. Steinmann
KIT, Karlsruhe, Germany

The storage ring Karlsruhe Research Accelerator (KARA) at KIT operate in a wide energy range from 0.5 to 2.5 GeV. Different non-linear effects, in particular, residual octupole components of the magnetic field of the CATACT wiggler at high field level (2.5 T), proximity of the working point to a vertical sextupole resonance Qy=8/3 and weak coupling octupole resonance 2Qx+2Qy=19, high chromaticity, etc. decrease the beam life time. This is because of the reduced dynamic aperture and momentum acceptance for off-momentum particles. A new operation point at high vertical tune Qy=2.81 was tested. For this, injection and ramping tables have been modified. First the values were optimized by simulations, then during beam tests, to minimize betatron tune shaking during beam-energy ramps. It stabilized high-current beams by the fast-feedback system the whole process: injection at 0.5 GeV, ramping, and operation at 1.3 GeV cycles. It essentially improved life time and beam current. In addition, new low-alpha tables have been created and tested, resulting in the reduction of the momentum compaction factor to 10^-4. Short bunch operation at 0.5GeV injection energy was also tested successfully.

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