HB2018 - Classification: Beam Dynamics in Rings

Paper	Title	Page
MOP1WA01	J-PARC RCS: Effects of Emittance Exchange on Injection Painting	20
	H. Hotchi JAEA/J-PARC, Tokai-mura, Japan
	The J-PARC RCS is a high-power rapid cycling synchrotron aiming for a 1-MW output beam power. This talk reports the recent progress of the J-PARC RCS beam commissioning and operation especially focusing on our efforts for beam dynamics issues that we faced during the process of the beam power ramp-up.
	Slides MOP1WA01 [4.081 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP1WA01
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MOP1WA02	IMP Heavy Ion Synchrotron
	J.C. Yang IMP/CAS, Lanzhou, People's Republic of China
	This talks is about IMP heavy ion synchrotron.
	Slides MOP1WA02 [8.382 MB]
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MOP1WA03	High Intensity Issues in Storage Rings
	M. Steck GSI, Darmstadt, Germany
	Storage Rings have peculiar issues for operation with high beam intensity. They can be caused by the application of beam cooling which results in highest beam quality. The heating by intrabeam scattering limits the achievable phase space density, but also space charge can be an issue when the ring is operated with low energy beams with high charge. The limits are even more severe when the beam is bunched for accumulation in longitudinal phase space or due to experiments which require a bunched stored beam.
	Slides MOP1WA03 [10.933 MB]
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MOP2WA01	Beam Physics Limitations for Damping of Instabilities in Circular Accelerators	26
	V.A. Lebedev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359 The paper considers a beam interaction with a feedback system and major limitations on the beam damping rate. In particular, it discusses: limitations on the system gain and damping rate, feedback system noise and its effect on the beam emittance growth, x-y coupling effect on damping, suppression of high order modes and damping of slip-stacked beams.
	Slides MOP2WA01 [0.408 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA01
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MOP2WA02	Chromaticity Effects on Head-Tail Instabilities for Broadband Impedance Using Two Particle Models, Vlasov Analysis, and Simulations
	Y.H. Chin KEK, Ibaraki, Japan
	This talk is about Chromaticity effects on head-tail instabilities for broadband impedance using two particle models, Vlasov analysis, and simulations.
	Slides MOP2WA02 [3.909 MB]
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MOP2WA03	Experiments and Theory on Beam Stabilization with Second-Order Chromaticity	32
	M. Schenk, X. Buffat, L.R. Carver, K.S.B. Li, E. Métral CERN, Geneva, Switzerland A. Maillard ENS, Paris, France
	This study reports on an alternative method to generate transverse Landau damping to suppress coherent instabilities in circular accelerators. The incoherent betatron tune spread can be produced through detuning with longitudinal rather than transverse action. This approach is motivated by the high-brightness, low transverse emittance beams in future colliders where detuning with transverse amplitude will be less effective. Detuning with longitudinal action can be introduced with a radio frequency (rf) quadrupole, or similarly, using second-order chromaticity. The latter was enhanced in the Large Hadron Collider (LHC) at CERN and experimental results on single-bunch stabilization are briefly recapped. The observations are interpreted analytically by extending the Vlasov formalism to include nonlinear chromaticity. Finally, the newly developed theory is benchmarked against circulant matrix and particle tracking models.
	Slides MOP2WA03 [3.374 MB]
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MOP2WA04	Recent Results from the Wideband Feedback System Tests at the SPS and Future Plans	38
	K.S.B. Li, H. Bartosik, M.S. Beck, E.R. Bjørsvik, W. Höfle, G. Kotzian, T.E. Levens, M. Schenk CERN, Geneva, Switzerland J.E. Dusatko, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA M. Schenk EPFL, Lausanne, Switzerland O. Turgut Stanford University, Stanford, California, USA
	A high bandwidth transverse feedback demonstrator system has been devised within the LARP framework in collaboration with SLAC for the LHC Injectors Upgrade (LIU) Project. The initial system targeted the Super Proton Synchrotron (SPS) at CERN to combat TMCI and electron cloud instabilities induced for bunches with bunch lengths at the 100 MHz scale. It features a very fast digital signal processing system running at up to 4~GS/s and high bandwidth kickers with a frequency reach of ultimately beyond 1~GHz. In recent years, the system has gradually been extended and now includes two stripline kickers for a total power of 1~kW delivering correction signals at frequencies of currently more than 700~MHz. This talk will cover recent studies using this demonstrator system to overcome TMCI limitations in the SPS. We will conclude with future plans and also briefly mention potential applications and requirements for larger machines such as the LHC or the HL-LHC.
	Slides MOP2WA04 [19.091 MB]
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MOP2WA05	Simulation and Measurement of the TMCI Threshold in the LHC	43
	D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, L.R. Carver, E. Métral CERN, Geneva, Switzerland
	The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*10¹¹ protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case.
	Slides MOP2WA05 [4.729 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA05
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TUP1WA01	High Intensity Proton Studies at RAL
	C.R. Prior STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	This talk is about High Intensity Proton Studies at RAL.
	Slides TUP1WA01 [27.949 MB]
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TUP1WA02	Fixed Field Accelerators and Space Charge Modeling	158
	A. Adelmann PSI, Villigen PSI, Switzerland C.T. Rogers STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	The efforts of the Fixed Field Accelerators FFA (formerly known as FFAG accelerators) community to address the high intensity challenge are reviewed. Starting from analytic estimates and linear models for space charge computation, the current possibilities of precise 3D models for start to end modeling are discussed.
	Slides TUP1WA02 [9.488 MB]
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TUP1WA03	Beam Instabilities After Injection to the LHC	163
	H. Timko, T. Argyropoulos, I. Karpov, E.N. Shaposhnikova CERN, Geneva, Switzerland
	Long-lasting phase oscillations have been observed at injection into the LHC since its first start-up with beam. These oscillations, however, were not leading to noticeable losses or blow-up in operation, and were therefore not studied in detail. In 2017, dedicated measurements with high-intensity bunches revealed that oscillations can lead to losses even slightly below the baseline intensity for the high-luminosity upgrade of the LHC. For the first time, high-resolution bunch profile acquisitions were triggered directly at injection and the formation of large-amplitude non-rigid dipole oscillations was observed on a turn-by-turn basis. First simulations can reproduce this instability via bunch filamentation that takes place after injection, depending on the mismatch between the bunch and bucket size in momentum at injection.
	Slides TUP1WA03 [2.166 MB]
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TUP2WA01	Optical Stochastic Cooling Experiment at the Fermilab IOTA Ring	168
	J.D. Jarvis, V.A. Lebedev, H. Piekarz, P. Piot, A.L. Romanov, J. Ruan Fermilab, Batavia, Illinois, USA M.B. Andorf, P. Piot Northern Illinois University, DeKalb, Illinois, USA
	Funding: Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Beam cooling enables an increase of peak and average luminosities and significantly expands the discovery potential of colliders; therefore it is an indispensable component of any modern design. Optical Stochastic Cooling (OSC) is a high-bandwidth, beam-cooling technique that will advance the present state-of-the-art, stochastic cooling rate by more than three orders of magnitude. It is an enabling technology for next-generation, discovery-science machines at the energy and intensity frontiers including hadron and electron-ion colliders. This paper presents the status of our experimental effort to demonstrate OSC at the Integrable Optics Test Accelerator (IOTA) ring, a testbed for advanced beam-physics concepts and technologies that is currently being commissioned at Fermilab. Our recent efforts are centered on the development of an integrated design that is prepared for final engineering and fabrication. The paper also presents a comparison of theoretical calculations and numerical simulations of the pickup-undulator radiation and its interaction with electrons in the kicker-undulator.
	Slides TUP2WA01 [20.009 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WA01
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TUP2WA02	Momentum Slip-Stacking Simulations for CERN SPS Ion Beams with Collective Effects	174
	D. Quartullo, T. Argyropoulos, A. Lasheen CERN, Geneva, Switzerland
	The LHC Injectors Upgrade (LIU) Project at CERN aims at doubling the total intensity of the Pb-ion beam for the High-Luminosity LHC (HL-LHC) project. This goal can be achieved by using momentum slip-stacking (MSS) in the SPS, the LHC injector. This RF gymnastics, originally proposed to increase bunch intensity, will be used on the intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 to 50 ns. The MSS feasibility can be tested only in 2021, after the beam controls upgrade of the SPS 200 MHz RF system, so beam dynamics simulations are used to design this complicated beam manipulation. Simulations of the MSS were performed using the CERN BLonD code with a full SPS impedance model. Attention has been paid to the choice of the RF and machine parameters (beam energy, time duration, RF frequency and voltage programmes) to reduce losses and the final bunch length which is crucial for the injection into the LHC 400 MHz buckets. The initial beam parameters used in simulations were obtained from beam measurements in the first part of the SPS cycle taking into account bunch-by-bunch losses on flat bottom and development of bunch instabilities.
	Slides TUP2WA02 [8.272 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WA02
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TUP2WA03	Studies of Capture and Flat-Bottom Losses in the SPS	180
	M. Schwarz, H. Bartosik, E. Chapochnikova, A. Lasheen, J. Repond, H. Timko CERN, Geneva, Switzerland
	One of the strong limitations for reaching higher beam intensities in the SPS, the injector of the LHC at CERN, are particle losses at flat bottom that increase with beam intensity. In this paper, different sources of these losses are investigated for two available SPS optics, using both measurements and simulations. Part of the losses originate from the PS-to-SPS bunch-to-bucket transfer, because the PS bunches are rotated in longitudinal phase space before injection and do not completely fit into the SPS RF bucket. The injection losses due to different injected bunch distributions were analyzed. Furthermore, at high intensities the transient beam loading in the SPS has a strong impact, which is (partially) compensated by the LLRF system. The effect of the present and future upgraded one-turn delay feedback system and phase loop on flat-bottom losses was studied using the longitudinal tracking code BLonD. Finally, the total particle losses are also affected by limitations in the SPS momentum aperture, visible for higher RF capture voltages in optics with lower transition energy and higher dispersion.
	Slides TUP2WA03 [8.038 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WA03
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TUP2WA04	Dynamic Vacuum Simulation for the BRing	186
	P. Li, Z. Dong, M. Li, J.C. Yang IMP/CAS, Lanzhou, People's Republic of China L.H.J. Bozyk GSI, Darmstadt, Germany
	Funding: Youth Innovation Promotion Association of Chinese Academy of Sciences 2016364, National Natural Science Foundation of China (Project No. 11675235). Large dynamic vacuum pressure rises of orders of magnitude which caused by the lost heavy ions can seriously limit the ion intensity and beam lifetime of the heavy ion accelerator, especially for the machine that operate the intermediate charge state heavy ion. The High Intensity heavy ion Accelerator Facility (HIAF) which will be built by the IMP will accumulate the intermediate charge state ion 238U³⁵⁺ to intensity 210¹¹ ppp to different terminals. In order to control the dynamic vacuum effects induced by the lose beams and design the collimation system for the BRing of the HIAF, a newly developed simulation program (ColBeam) and GSI's simulation code StrahlSim are both conducted and the dynamic vacuum simulation result is calculated by the StrahlSim. According to the simulation result, 310¹¹ ppp particles is the up limit beam intensity can be extracted for the current BRing vacuum system design. Higher beam intensity can be reach to 510¹¹ ppp when the NEG coating technology must be implemented for the dipole and quadrupole chamber. HIAF, Collimation, Dynamic vacuum*
	Slides TUP2WA04 [9.947 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WA04
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TUP2WA05	Effect of the Extraction Kickers on the Beam Stability in the CERN SPS	189
	A. Farricker, M.S. Beck, J. Repond, C. Vollinger CERN, Geneva, Switzerland
	Longitudinal beam instability in the CERN SPS is a major limitation in the ability to achieve the bunch intensities required for the goals of the High-Luminosity LHC project (HL-LHC). One of the major drivers in limiting the intensity of the machine is the broadband contribution to the beam-coupling impedance due to the kicker magnets. The extraction kickers (MKE) discussed in this paper are known to give a significant contribution to the overall longitudinal beam-coupling impedance. We present the results of bench measurements of the MKE's impedance to determine the accuracy of electromagnetic simulation models from which the impedance modelused for beam dynamics simulationsis constructed. In addition, we discuss the feasibility and implementation of beam measurements that can indicate the contribution of the MKE magnets to the longitudinal beam-coupling impedance of the SPS.
	Slides TUP2WA05 [2.698 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WA05
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TUP2WA06	Beam Dynamics Study of the Heavy Ion Bunch Rotation With Space Charge Effect in BRing at HIAF
	D.Y. Yin IMP/CAS, Lanzhou, People's Republic of China
	BRing-the key part of the High Intensity heavy-ion Accelerator Facility(HIAF) complex will provide intense heavy ion beams to expand nuclear and related researches into presently unreachable region. As a synchrotron, BRing is designed to accumulate and accelerate heavy ion beams provided by iLinac up to high intensity and energy. Compared to the present research facility CSRm of HIRFL, the primary heavy ion beams intensity will be increased substantially which will open a new path for the HED physics research which requires high quality, well focused, and strongly bunched intense particle beams to satisfy the very high energy deposition to achieve high target power density in laboratory. Based on the beam parameters of 238U³⁵⁺ proposed by the BRing at HIAF, the two critical issues will be studied. One is transmission efficiency during the whole process which can be a necessary prerequisite to ensure the beam intensity, and the other one is bunch rotation longitudinally which is an effective way of producing short pulse duration bunch. Through the analytical calculations and tracking simulations, the possible bunch length and peak beam power after rotation are presented.
	Slides TUP2WA06 [2.341 MB]
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WEA1WA01	Sum Resonances with Space Charge	226
	G. Franchetti GSI, Darmstadt, Germany
	This presentation will discuss the extension of the theory of the sum resonances with space charge.
	Slides WEA1WA01 [5.267 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA1WA01
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WEA1WA02	Approaching the High-Intensity Frontier Using the Multi-Turn Extraction at the CERN Proton Synchrotron	231
	A. Huschauer, H. Bartosik, S. Cettour-Cave, M. R. Coly, D.G. Cotte, H. Damerau, G.P. Di Giovanni, S.S. Gilardoni, M. Giovannozzi, V. Kain, E. Koukovini-Platia, B. Mikulec, G. Sterbini, F. Tecker CERN, Geneva, Switzerland
	Complementary to the physics research at the LHC, several fixed target facilities receive beams from the LHC injector complex. In the scope of the fixed target physics program at the Super Proton Synchrotron, high-intensity proton beams from the Proton Synchrotron are extracted using the Multi-Turn Extraction scheme, which is based on particle trapping in stable islands of the horizontal phase space. Considering the number of protons requested by future experimental fixed target facilities, such as the Search for Hidden Particles experiment, the currently operationally delivered beam intensities are insufficient. Therefore, experimental studies have been conducted to optimize the Multi-Turn Extraction technique and to exploit the possible intensity reach. The results of these studies along with the operational performance of high-intensity beams during the 2017 run are presented in this paper. Furthermore, the impact of the hardware changes pursued in the framework of the LHC Injectors Upgrade project on the high-intensity beam properties is briefly mentioned.
	Slides WEA1WA02 [25.566 MB]
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WEA2WA01	High Intensity Effects of Fixed Target Beams in the CERN Injector Complex	237
	E. Koukovini-Platia, H. Bartosik, M. Migliorati, G. Rumolo CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy M. Migliorati Sapienza University of Rome, Rome, Italy
	The current fixed target (FT) experiments at CERN are a complementary approach to the Large Hadron Collider (LHC) and play a crucial role in the investigation of fundamental questions in particle physics. Within the scope of the LHC Injectors Upgrade (LIU), aiming to improve the LHC beam production, the injector complex will be significantly upgraded during the second Long Shutdown (LS2). All non-LHC beams are expected to benefit from these upgrades. In this paper, we focus on the studies of the transverse instability in the Proton Synchrotron (PS), currently limiting the intensity of Time-Of-Flight (ToF) type beams, as well as the prediction of the impact of envisaged hardware modifications. A first discussion on the effect of space charge on the observed instability is also being presented.
	Slides WEA2WA01 [2.483 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA01
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WEA2WA02	Microbunched Electron Cooling (MBEC) for Future Electron-ion Colliders	243
	G. Stupakov SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515. The Microbunched Electron Cooling (MBEC) is a promising cooling technique that can find applications in future hadron and electron-ion colliders. In this paper we give a qualitative derivation of the cooling rate for MBEC and estimate the cooling time for the eRHIC electron-ion collider. We then argue that MBEC with two plasma amplification stages should be sufficient to overcome the emittance growth due to the intra-beam scattering in eRHIC.
	Slides WEA2WA02 [2.701 MB]
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WEA2WA03	High Intensity Studies with Paul Trap
	S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	Funding: Royal Society To date our understanding of fundamental intensity limitations and studies of instabilities and resonances has been based on time-consuming accelerator-based experiments or on simulations, limited by computational power and noise artifacts that can obscure real beam physics effects. As beam intensities increase and new concepts emerge for high intensity machines, accelerator physicists require new methods, tools and modeling techniques to understand the complex dynamics of the intense beams involved. In this talk I will introduce a scaled experimental system known as a Paul ion trap, and discuss how this multi-disciplinary technique is being used to address some of the most challenging questions in the field of intense particle beam dynamics.
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WEA2WA04	Space-Charge Compensation Using Electron Columns at IOTA	247
	B.T. Freemire Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay Northern Illinois Univerity, DeKalb, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea C.S. Park, V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA G. Penn LBNL, Berkeley, California, USA
	Funding: US Department of Energy contracts DE-AC02-07CH11359 and DE-AC02-05CH1123 and the GARD Program. Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam.
	Slides WEA2WA04 [8.501 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA04
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WEP1WA01	Simulations of Electron-Ion Effects and Relevance to LHC Experience in 2017
	L. Mether EPFL, Lausanne, Switzerland G. Iadarola, G. Rumolo CERN, Geneva, Switzerland
	Operation of the LHC in 2017 was severely affected by recurrent beam aborts triggered by beam losses in one of its arc cells. The losses were correlated with quickly developing transverse coherent oscillations, which in most cases caused the beam dumps due to particle losses in the cleaning insertions. The events are thought to have been caused by air that was frozen on the beam screen surface in the concerned location, and which through a complex sequence of events could give rise to a localized high gas density. In this contribution we describe efforts towards modelling the observed coherent effects through the interaction of the beam with the induced pressure bump.
	Slides WEP1WA01 [10.532 MB]
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WEP1WA02	Beam-Beam Studies in Present and Future Hadron Colliders
	Y. Papaphilippou CERN, Geneva, Switzerland
	The impact on beam-beam effects in the non-linear dynamics of colliding hadron beams is reviewed, with emphasis on simulation and measurement examples from the LHC and its High-Luminosity upgrade (HL-LHC). The main limitation encountered is the effect of the beam-beam long range (BBLR) interaction which limits the beam lifetime at collision and is well correlated with the minimum dynamic aperture (DA), as shown by measurements in the LHC. Thereby, multi-parametric DA simulations are used as a guide in order to define the collider settings and beam parameters through the LHC run. The same approach is used for validating the operational HL-LHC scenario and improving the beam performance at collision. Recent studies on the impact of tune modulation to the collider lifetime are briefly described. Finally, the potential of BBLR compensation in the HL-LHC era is evaluated through simulations and LHC machine studies.
	Slides WEP1WA02 [6.355 MB]
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WEP1WA03	IBS Near Transition Crossing in NICA Collider	252
	S.A. Kostromin, A.O. Sidorin JINR, Dubna, Moscow Region, Russia I.V. Gorelyshev JINR/VBLHEP, Dubna, Moscow region, Russia V.A. Lebedev Fermilab, Batavia, Illinois, USA A.O. Sidorin Saint Petersburg State University, Saint Petersburg, Russia
	Intrabeam scattering (IBS) of charged particles in a particle beam results in an exchange of energy between different degrees of freedom. That results in an increase of average energy of particles in the beam frame and an increase of the 3D-emittance. The paper considers calculations of beam emittance growth rates for different options of NICA collider and IBS effects in close vicinity of the transition.
	Slides WEP1WA03 [1.774 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP1WA03
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WEP2PO002	Scaling Laws for the Time Dependence of Luminosity in Hadron Circular Accelerators based on Simple Models of Dynamic Aperture Evolution	260
	F.F. Van der Veken, M. Giovannozzi CERN, Geneva, Switzerland
	In recent years, models for the time-evolution of the dynamic aperture have been proposed and applied to the analysis of non-linear betatronic motion in circular accelerators. In this paper, these models are used to derive scaling laws for the luminosity evolution and are applied to the analysis of the data collected during the LHC physics runs. An extended set of fills from the LHC proton physics has been analysed and the results presented and discussed in detail. The long-term goal of these studies is to improve the estimate of the performance reach of the HL-LHC.
	Poster WEP2PO002 [5.757 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO002
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WEP2PO003	Beam Loading and Longitudinal Stability Evaluation for the FCC-ee Rings	266
	I. Karpov, P. Baudrenghien CERN, Geneva, Switzerland
	In high-current accelerators, interaction of the beam with fundamental impedance of the accelerating cavities can limit machine performance. It can result in a significant variation of bunch-by-bunch parameters (bunch length, synchronous phase, etc.) and lead to longitudinal coupled-bunch instability. In this work, these limitations are analysed together with possible cures for the high-current option (Z machine) of the future circular electron-positron collider (FCC-ee). The time-domain calculations of steady-state beam loading are presented and compared with frequency-domain analysis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO003
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WEP2PO006	Overview of the CERN PSB-to-PS Transfer Line Optics Matching Studies in View of the LHC Injectors Upgrade Project	272
	V. Forte, S.C.P. Albright, W. Bartmann, G.P. Di Giovanni, M.A. Fraser, C. Heßler, A. Huschauer, A. Oeftiger CERN, Geneva, Switzerland
	At injection into the CERN Proton Synchrotron (PS) a significant horizontal emittance blow-up of the present high brightness beams for the LHC is observed. A partial contribution to this effect is suspected to be an important mismatch between the dispersion function in the transfer line from the PS Booster (PSB) and the ring itself. This mismatch will be unacceptable in view of the beam parameters requested by the LHC Injectors Upgrade (LIU) project with high longitudinal emittance and momentum spread. To deliver the requested beam parameters the PSB-to-PS transfer line will be upgraded and the optics in the line changed to improve the matching from all the four PSB rings. A re-matching campaign from the PSB ring 3 has been carried out to evaluate the impact of the present optics mismatch as a source of emittance growth both in simulations and measurements.
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WEP2PO007	Multi-Particle Simulations of the Future CERN PSB Injection Process with Updated Linac4 Beam Performance	278
	V. Forte, C. Bracco, G.P. Di Giovanni, M.A. Fraser, A.M. Lombardi, B. Mikulec CERN, Geneva, Switzerland
	In the framework of the LHC Injectors Upgrade (LIU) project, the injection process in the CERN Proton Synchrotron Booster (PSB) will be renovated after the connection with the Linac4. A new H⁻ charge exchange injection system using a stripping foil is foreseen to increase the brightness of the stored beams and to provide high flexibility in terms of emittance tailoring at 160 MeV. Realistic multi-particle simulations of the future injection processes for high brightness beams (i.e. for the LHC) and high intensity beams (i.e. for the ISOLDE experiment) are presented in this paper. The simulations are based on the present performance of Linac4 and include scattering induced by the foil, space charge effects and compensation of the lattice perturbation introduced by the bumpers of the injection chicane.
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WEP2PO008	SPS Long Term Stability Studies in the Presence of Crab Cavities and High Order Multipoles	284
	A. Alekou, H. Bartosik, R. Calaga, M. Carlà, Y. Papaphilippou CERN, Geneva, Switzerland R.B. Appleby, R.B. Appleby UMAN, Manchester, United Kingdom R.B. Appleby Cockcroft Institute, Warrington, Cheshire, United Kingdom
	A local Crab Cavity (CC) scheme will recover the head-on collisions at the IP of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The tight space constraints at the CC location result in axially non-symmetric cavity designs that introduce high order multipole CC components. The impact of these high order components on the long term stability of the beam in the SPS machine, where two prototype crab cavities are presently installed in the CERN SPS to perform tests with beam, is presented. Furthermore, the Dynamic Aperture is studied in the presence of the SPS errors. Future plans are discussed.
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WEP2PO011	Studies of Transverse Instabilities in the CERN SPS	291
	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 Computer Science and Electrical Engineering, Rostock, Germany
	In the framework of the LHC Injectors Upgrade (LIU), beams with about twice the intensity compared to the present values will have to be accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). Machine studies with intensity higher than the nominal LHC beam have shown that coherent instabilities in both transverse planes may develop at injection energy, potentially becoming a limitation for the future high intensity operation. In particular, a transverse mode coupling instability is encountered in the vertical plane, the threshold of which can be sufficiently increased by changing the machine optics. In addition, a headtail instability of individual bunches is observed in the horizontal plane in multi-bunch operation, which requires stabilization by high chromaticity. The PyHEADTAIL code has been used to check if the present SPS impedance model reproduces the experimental observations. The instability growth rates have been studied for different machine optics configurations and different chromaticity settings. Other stabilizing mechanisms like tune spread from octupoles or the transverse damper have also been investigated.
	Poster WEP2PO011 [4.940 MB]
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WEP2PO018	Magnetic Field Tracking at CSNS/RCS	306
	S.Y. Xu, S. Fu IHEP, Beijing, People's Republic of China
	Because of the differences of magnetic saturation and eddy current effects between different magnets, magnetic field tracking errors between different magnets is larger than 2.5 % at the Rapid Cycling Synchrotron (RCS) of Chinese Spallation Neutron Source (CSNS), and the induced tune shift is larger than 0.1. So larger tune shift may lead the beam to pass through the resonance lines. To reduce the magnetic field tracking errors, a method of wave form compensation for magnets of the Rapid Cycling Synchrotron was investigated on the magnets of CSNS/RCS. The wave form compensation was applied to CSNS/RCS commissioning. By performing wave form compensation, the maximum magnetic field tracking error was reduced from 2.5 % to 0.08 %, and the maximum tune shift over the ramping process was reduced from 0.1 to 0.004.
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WEP2PO024	Resonance Stop-bands Compensation at Booster Ring of HIAF	315
	J. Li, J.C. Yang IMP/CAS, Lanzhou, People's Republic of China
	Booster Ring (BRing) of the new approved High Intensity heavy-ion Accelerator Facility (HIAF) in China is designed to stack 0.3-1.0·10¹¹ number of 238U³⁵⁺ ions by painting injection and deliver over such intensity beam in extraction. However, depressed tune spread caused by space charge effect crosses the low-order resonance stop-bands after bunching the storage beam. To keep a low beam loss during crossing, stop-band compensation scheme is proposed covering the whole process of RF capture and early acceleration.
	Poster WEP2PO024 [1.218 MB]
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Paper

Title

Page

J-PARC RCS: Effects of Emittance Exchange on Injection Painting

20

H. Hotchi
JAEA/J-PARC, Tokai-mura, Japan

The J-PARC RCS is a high-power rapid cycling synchrotron aiming for a 1-MW output beam power. This talk reports the recent progress of the J-PARC RCS beam commissioning and operation especially focusing on our efforts for beam dynamics issues that we faced during the process of the beam power ramp-up.

Slides MOP1WA01 [4.081 MB]

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MOP1WA02

IMP Heavy Ion Synchrotron

J.C. Yang
IMP/CAS, Lanzhou, People's Republic of China

This talks is about IMP heavy ion synchrotron.

Slides MOP1WA02 [8.382 MB]

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MOP1WA03

High Intensity Issues in Storage Rings

M. Steck
GSI, Darmstadt, Germany

Storage Rings have peculiar issues for operation with high beam intensity. They can be caused by the application of beam cooling which results in highest beam quality. The heating by intrabeam scattering limits the achievable phase space density, but also space charge can be an issue when the ring is operated with low energy beams with high charge. The limits are even more severe when the beam is bunched for accumulation in longitudinal phase space or due to experiments which require a bunched stored beam.

Slides MOP1WA03 [10.933 MB]

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MOP2WA01

Beam Physics Limitations for Damping of Instabilities in Circular Accelerators

26

V.A. Lebedev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359
The paper considers a beam interaction with a feedback system and major limitations on the beam damping rate. In particular, it discusses: limitations on the system gain and damping rate, feedback system noise and its effect on the beam emittance growth, x-y coupling effect on damping, suppression of high order modes and damping of slip-stacked beams.

Slides MOP2WA01 [0.408 MB]

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MOP2WA02

Chromaticity Effects on Head-Tail Instabilities for Broadband Impedance Using Two Particle Models, Vlasov Analysis, and Simulations

Y.H. Chin
KEK, Ibaraki, Japan

This talk is about Chromaticity effects on head-tail instabilities for broadband impedance using two particle models, Vlasov analysis, and simulations.

Slides MOP2WA02 [3.909 MB]

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MOP2WA03

Experiments and Theory on Beam Stabilization with Second-Order Chromaticity

32

M. Schenk, X. Buffat, L.R. Carver, K.S.B. Li, E. Métral
CERN, Geneva, Switzerland
A. Maillard
ENS, Paris, France

This study reports on an alternative method to generate transverse Landau damping to suppress coherent instabilities in circular accelerators. The incoherent betatron tune spread can be produced through detuning with longitudinal rather than transverse action. This approach is motivated by the high-brightness, low transverse emittance beams in future colliders where detuning with transverse amplitude will be less effective. Detuning with longitudinal action can be introduced with a radio frequency (rf) quadrupole, or similarly, using second-order chromaticity. The latter was enhanced in the Large Hadron Collider (LHC) at CERN and experimental results on single-bunch stabilization are briefly recapped. The observations are interpreted analytically by extending the Vlasov formalism to include nonlinear chromaticity. Finally, the newly developed theory is benchmarked against circulant matrix and particle tracking models.

Slides MOP2WA03 [3.374 MB]

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MOP2WA04

Recent Results from the Wideband Feedback System Tests at the SPS and Future Plans

38

K.S.B. Li, H. Bartosik, M.S. Beck, E.R. Bjørsvik, W. Höfle, G. Kotzian, T.E. Levens, M. Schenk
CERN, Geneva, Switzerland
J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
M. Schenk
EPFL, Lausanne, Switzerland
O. Turgut
Stanford University, Stanford, California, USA

A high bandwidth transverse feedback demonstrator system has been devised within the LARP framework in collaboration with SLAC for the LHC Injectors Upgrade (LIU) Project. The initial system targeted the Super Proton Synchrotron (SPS) at CERN to combat TMCI and electron cloud instabilities induced for bunches with bunch lengths at the 100 MHz scale. It features a very fast digital signal processing system running at up to 4~GS/s and high bandwidth kickers with a frequency reach of ultimately beyond 1~GHz. In recent years, the system has gradually been extended and now includes two stripline kickers for a total power of 1~kW delivering correction signals at frequencies of currently more than 700~MHz. This talk will cover recent studies using this demonstrator system to overcome TMCI limitations in the SPS. We will conclude with future plans and also briefly mention potential applications and requirements for larger machines such as the LHC or the HL-LHC.

Slides MOP2WA04 [19.091 MB]

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MOP2WA05

Simulation and Measurement of the TMCI Threshold in the LHC

43

D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, L.R. Carver, E. Métral
CERN, Geneva, Switzerland

The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*10¹¹ protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case.

Slides MOP2WA05 [4.729 MB]

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TUP1WA01

High Intensity Proton Studies at RAL

C.R. Prior
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

This talk is about High Intensity Proton Studies at RAL.

Slides TUP1WA01 [27.949 MB]

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TUP1WA02

Fixed Field Accelerators and Space Charge Modeling

158

A. Adelmann
PSI, Villigen PSI, Switzerland
C.T. Rogers
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The efforts of the Fixed Field Accelerators FFA (formerly known as FFAG accelerators) community to address the high intensity challenge are reviewed. Starting from analytic estimates and linear models for space charge computation, the current possibilities of precise 3D models for start to end modeling are discussed.

Slides TUP1WA02 [9.488 MB]

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TUP1WA03

Beam Instabilities After Injection to the LHC

163

H. Timko, T. Argyropoulos, I. Karpov, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Long-lasting phase oscillations have been observed at injection into the LHC since its first start-up with beam. These oscillations, however, were not leading to noticeable losses or blow-up in operation, and were therefore not studied in detail. In 2017, dedicated measurements with high-intensity bunches revealed that oscillations can lead to losses even slightly below the baseline intensity for the high-luminosity upgrade of the LHC. For the first time, high-resolution bunch profile acquisitions were triggered directly at injection and the formation of large-amplitude non-rigid dipole oscillations was observed on a turn-by-turn basis. First simulations can reproduce this instability via bunch filamentation that takes place after injection, depending on the mismatch between the bunch and bucket size in momentum at injection.

Slides TUP1WA03 [2.166 MB]

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TUP2WA01

Optical Stochastic Cooling Experiment at the Fermilab IOTA Ring

168

J.D. Jarvis, V.A. Lebedev, H. Piekarz, P. Piot, A.L. Romanov, J. Ruan
Fermilab, Batavia, Illinois, USA
M.B. Andorf, P. Piot
Northern Illinois University, DeKalb, Illinois, USA

Funding: Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Beam cooling enables an increase of peak and average luminosities and significantly expands the discovery potential of colliders; therefore it is an indispensable component of any modern design. Optical Stochastic Cooling (OSC) is a high-bandwidth, beam-cooling technique that will advance the present state-of-the-art, stochastic cooling rate by more than three orders of magnitude. It is an enabling technology for next-generation, discovery-science machines at the energy and intensity frontiers including hadron and electron-ion colliders. This paper presents the status of our experimental effort to demonstrate OSC at the Integrable Optics Test Accelerator (IOTA) ring, a testbed for advanced beam-physics concepts and technologies that is currently being commissioned at Fermilab. Our recent efforts are centered on the development of an integrated design that is prepared for final engineering and fabrication. The paper also presents a comparison of theoretical calculations and numerical simulations of the pickup-undulator radiation and its interaction with electrons in the kicker-undulator.

Slides TUP2WA01 [20.009 MB]

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TUP2WA02

Momentum Slip-Stacking Simulations for CERN SPS Ion Beams with Collective Effects

174

D. Quartullo, T. Argyropoulos, A. Lasheen
CERN, Geneva, Switzerland

The LHC Injectors Upgrade (LIU) Project at CERN aims at doubling the total intensity of the Pb-ion beam for the High-Luminosity LHC (HL-LHC) project. This goal can be achieved by using momentum slip-stacking (MSS) in the SPS, the LHC injector. This RF gymnastics, originally proposed to increase bunch intensity, will be used on the intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 to 50 ns. The MSS feasibility can be tested only in 2021, after the beam controls upgrade of the SPS 200 MHz RF system, so beam dynamics simulations are used to design this complicated beam manipulation. Simulations of the MSS were performed using the CERN BLonD code with a full SPS impedance model. Attention has been paid to the choice of the RF and machine parameters (beam energy, time duration, RF frequency and voltage programmes) to reduce losses and the final bunch length which is crucial for the injection into the LHC 400 MHz buckets. The initial beam parameters used in simulations were obtained from beam measurements in the first part of the SPS cycle taking into account bunch-by-bunch losses on flat bottom and development of bunch instabilities.

Slides TUP2WA02 [8.272 MB]

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TUP2WA03

Studies of Capture and Flat-Bottom Losses in the SPS

180

M. Schwarz, H. Bartosik, E. Chapochnikova, A. Lasheen, J. Repond, H. Timko
CERN, Geneva, Switzerland

One of the strong limitations for reaching higher beam intensities in the SPS, the injector of the LHC at CERN, are particle losses at flat bottom that increase with beam intensity. In this paper, different sources of these losses are investigated for two available SPS optics, using both measurements and simulations. Part of the losses originate from the PS-to-SPS bunch-to-bucket transfer, because the PS bunches are rotated in longitudinal phase space before injection and do not completely fit into the SPS RF bucket. The injection losses due to different injected bunch distributions were analyzed. Furthermore, at high intensities the transient beam loading in the SPS has a strong impact, which is (partially) compensated by the LLRF system. The effect of the present and future upgraded one-turn delay feedback system and phase loop on flat-bottom losses was studied using the longitudinal tracking code BLonD. Finally, the total particle losses are also affected by limitations in the SPS momentum aperture, visible for higher RF capture voltages in optics with lower transition energy and higher dispersion.

Slides TUP2WA03 [8.038 MB]

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TUP2WA04

Dynamic Vacuum Simulation for the BRing

186

P. Li, Z. Dong, M. Li, J.C. Yang
IMP/CAS, Lanzhou, People's Republic of China
L.H.J. Bozyk
GSI, Darmstadt, Germany

Funding: Youth Innovation Promotion Association of Chinese Academy of Sciences 2016364, National Natural Science Foundation of China (Project No. 11675235).
Large dynamic vacuum pressure rises of orders of magnitude which caused by the lost heavy ions can seriously limit the ion intensity and beam lifetime of the heavy ion accelerator, especially for the machine that operate the intermediate charge state heavy ion. The High Intensity heavy ion Accelerator Facility (HIAF) which will be built by the IMP will accumulate the intermediate charge state ion 238U³⁵⁺ to intensity 2*10¹¹ ppp to different terminals. In order to control the dynamic vacuum effects induced by the lose beams and design the collimation system for the BRing of the HIAF, a newly developed simulation program (ColBeam) and GSI's simulation code StrahlSim are both conducted and the dynamic vacuum simulation result is calculated by the StrahlSim. According to the simulation result, 3*10¹¹ ppp particles is the up limit beam intensity can be extracted for the current BRing vacuum system design. Higher beam intensity can be reach to 5*10¹¹ ppp when the NEG coating technology must be implemented for the dipole and quadrupole chamber.
HIAF, Collimation, Dynamic vacuum

Slides TUP2WA04 [9.947 MB]

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TUP2WA05

Effect of the Extraction Kickers on the Beam Stability in the CERN SPS

189

A. Farricker, M.S. Beck, J. Repond, C. Vollinger
CERN, Geneva, Switzerland

Longitudinal beam instability in the CERN SPS is a major limitation in the ability to achieve the bunch intensities required for the goals of the High-Luminosity LHC project (HL-LHC). One of the major drivers in limiting the intensity of the machine is the broadband contribution to the beam-coupling impedance due to the kicker magnets. The extraction kickers (MKE) discussed in this paper are known to give a significant contribution to the overall longitudinal beam-coupling impedance. We present the results of bench measurements of the MKE's impedance to determine the accuracy of electromagnetic simulation models from which the impedance modelused for beam dynamics simulationsis constructed. In addition, we discuss the feasibility and implementation of beam measurements that can indicate the contribution of the MKE magnets to the longitudinal beam-coupling impedance of the SPS.

Slides TUP2WA05 [2.698 MB]

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TUP2WA06

Beam Dynamics Study of the Heavy Ion Bunch Rotation With Space Charge Effect in BRing at HIAF

D.Y. Yin
IMP/CAS, Lanzhou, People's Republic of China

BRing-the key part of the High Intensity heavy-ion Accelerator Facility(HIAF) complex will provide intense heavy ion beams to expand nuclear and related researches into presently unreachable region. As a synchrotron, BRing is designed to accumulate and accelerate heavy ion beams provided by iLinac up to high intensity and energy. Compared to the present research facility CSRm of HIRFL, the primary heavy ion beams intensity will be increased substantially which will open a new path for the HED physics research which requires high quality, well focused, and strongly bunched intense particle beams to satisfy the very high energy deposition to achieve high target power density in laboratory. Based on the beam parameters of 238U³⁵⁺ proposed by the BRing at HIAF, the two critical issues will be studied. One is transmission efficiency during the whole process which can be a necessary prerequisite to ensure the beam intensity, and the other one is bunch rotation longitudinally which is an effective way of producing short pulse duration bunch. Through the analytical calculations and tracking simulations, the possible bunch length and peak beam power after rotation are presented.

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WEA1WA01

Sum Resonances with Space Charge

226

G. Franchetti
GSI, Darmstadt, Germany

This presentation will discuss the extension of the theory of the sum resonances with space charge.

Slides WEA1WA01 [5.267 MB]

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WEA1WA02

Approaching the High-Intensity Frontier Using the Multi-Turn Extraction at the CERN Proton Synchrotron

231

A. Huschauer, H. Bartosik, S. Cettour-Cave, M. R. Coly, D.G. Cotte, H. Damerau, G.P. Di Giovanni, S.S. Gilardoni, M. Giovannozzi, V. Kain, E. Koukovini-Platia, B. Mikulec, G. Sterbini, F. Tecker
CERN, Geneva, Switzerland

Complementary to the physics research at the LHC, several fixed target facilities receive beams from the LHC injector complex. In the scope of the fixed target physics program at the Super Proton Synchrotron, high-intensity proton beams from the Proton Synchrotron are extracted using the Multi-Turn Extraction scheme, which is based on particle trapping in stable islands of the horizontal phase space. Considering the number of protons requested by future experimental fixed target facilities, such as the Search for Hidden Particles experiment, the currently operationally delivered beam intensities are insufficient. Therefore, experimental studies have been conducted to optimize the Multi-Turn Extraction technique and to exploit the possible intensity reach. The results of these studies along with the operational performance of high-intensity beams during the 2017 run are presented in this paper. Furthermore, the impact of the hardware changes pursued in the framework of the LHC Injectors Upgrade project on the high-intensity beam properties is briefly mentioned.

Slides WEA1WA02 [25.566 MB]

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WEA2WA01

High Intensity Effects of Fixed Target Beams in the CERN Injector Complex

237

E. Koukovini-Platia, H. Bartosik, M. Migliorati, G. Rumolo
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy
M. Migliorati
Sapienza University of Rome, Rome, Italy

The current fixed target (FT) experiments at CERN are a complementary approach to the Large Hadron Collider (LHC) and play a crucial role in the investigation of fundamental questions in particle physics. Within the scope of the LHC Injectors Upgrade (LIU), aiming to improve the LHC beam production, the injector complex will be significantly upgraded during the second Long Shutdown (LS2). All non-LHC beams are expected to benefit from these upgrades. In this paper, we focus on the studies of the transverse instability in the Proton Synchrotron (PS), currently limiting the intensity of Time-Of-Flight (ToF) type beams, as well as the prediction of the impact of envisaged hardware modifications. A first discussion on the effect of space charge on the observed instability is also being presented.

Slides WEA2WA01 [2.483 MB]

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WEA2WA02

Microbunched Electron Cooling (MBEC) for Future Electron-ion Colliders

243

G. Stupakov
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515.
The Microbunched Electron Cooling (MBEC) is a promising cooling technique that can find applications in future hadron and electron-ion colliders. In this paper we give a qualitative derivation of the cooling rate for MBEC and estimate the cooling time for the eRHIC electron-ion collider. We then argue that MBEC with two plasma amplification stages should be sufficient to overcome the emittance growth due to the intra-beam scattering in eRHIC.

Slides WEA2WA02 [2.701 MB]

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WEA2WA03

High Intensity Studies with Paul Trap

S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Funding: Royal Society
To date our understanding of fundamental intensity limitations and studies of instabilities and resonances has been based on time-consuming accelerator-based experiments or on simulations, limited by computational power and noise artifacts that can obscure real beam physics effects. As beam intensities increase and new concepts emerge for high intensity machines, accelerator physicists require new methods, tools and modeling techniques to understand the complex dynamics of the intense beams involved. In this talk I will introduce a scaled experimental system known as a Paul ion trap, and discuss how this multi-disciplinary technique is being used to address some of the most challenging questions in the field of intense particle beam dynamics.

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WEA2WA04

Space-Charge Compensation Using Electron Columns at IOTA

247

B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
C.S. Park, V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA
G. Penn
LBNL, Berkeley, California, USA

Funding: US Department of Energy contracts DE-AC02-07CH11359 and DE-AC02-05CH1123 and the GARD Program.
Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam.

Slides WEA2WA04 [8.501 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA04

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WEP1WA01

Simulations of Electron-Ion Effects and Relevance to LHC Experience in 2017

L. Mether
EPFL, Lausanne, Switzerland
G. Iadarola, G. Rumolo
CERN, Geneva, Switzerland

Operation of the LHC in 2017 was severely affected by recurrent beam aborts triggered by beam losses in one of its arc cells. The losses were correlated with quickly developing transverse coherent oscillations, which in most cases caused the beam dumps due to particle losses in the cleaning insertions. The events are thought to have been caused by air that was frozen on the beam screen surface in the concerned location, and which through a complex sequence of events could give rise to a localized high gas density. In this contribution we describe efforts towards modelling the observed coherent effects through the interaction of the beam with the induced pressure bump.

Slides WEP1WA01 [10.532 MB]

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WEP1WA02

Beam-Beam Studies in Present and Future Hadron Colliders

Y. Papaphilippou
CERN, Geneva, Switzerland

The impact on beam-beam effects in the non-linear dynamics of colliding hadron beams is reviewed, with emphasis on simulation and measurement examples from the LHC and its High-Luminosity upgrade (HL-LHC). The main limitation encountered is the effect of the beam-beam long range (BBLR) interaction which limits the beam lifetime at collision and is well correlated with the minimum dynamic aperture (DA), as shown by measurements in the LHC. Thereby, multi-parametric DA simulations are used as a guide in order to define the collider settings and beam parameters through the LHC run. The same approach is used for validating the operational HL-LHC scenario and improving the beam performance at collision. Recent studies on the impact of tune modulation to the collider lifetime are briefly described. Finally, the potential of BBLR compensation in the HL-LHC era is evaluated through simulations and LHC machine studies.

Slides WEP1WA02 [6.355 MB]

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WEP1WA03

IBS Near Transition Crossing in NICA Collider

252

S.A. Kostromin, A.O. Sidorin
JINR, Dubna, Moscow Region, Russia
I.V. Gorelyshev
JINR/VBLHEP, Dubna, Moscow region, Russia
V.A. Lebedev
Fermilab, Batavia, Illinois, USA
A.O. Sidorin
Saint Petersburg State University, Saint Petersburg, Russia

Intrabeam scattering (IBS) of charged particles in a particle beam results in an exchange of energy between different degrees of freedom. That results in an increase of average energy of particles in the beam frame and an increase of the 3D-emittance. The paper considers calculations of beam emittance growth rates for different options of NICA collider and IBS effects in close vicinity of the transition.

Slides WEP1WA03 [1.774 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP1WA03

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WEP2PO002

Scaling Laws for the Time Dependence of Luminosity in Hadron Circular Accelerators based on Simple Models of Dynamic Aperture Evolution

260

F.F. Van der Veken, M. Giovannozzi
CERN, Geneva, Switzerland

In recent years, models for the time-evolution of the dynamic aperture have been proposed and applied to the analysis of non-linear betatronic motion in circular accelerators. In this paper, these models are used to derive scaling laws for the luminosity evolution and are applied to the analysis of the data collected during the LHC physics runs. An extended set of fills from the LHC proton physics has been analysed and the results presented and discussed in detail. The long-term goal of these studies is to improve the estimate of the performance reach of the HL-LHC.

Poster WEP2PO002 [5.757 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO002

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WEP2PO003

Beam Loading and Longitudinal Stability Evaluation for the FCC-ee Rings

266

I. Karpov, P. Baudrenghien
CERN, Geneva, Switzerland

In high-current accelerators, interaction of the beam with fundamental impedance of the accelerating cavities can limit machine performance. It can result in a significant variation of bunch-by-bunch parameters (bunch length, synchronous phase, etc.) and lead to longitudinal coupled-bunch instability. In this work, these limitations are analysed together with possible cures for the high-current option (Z machine) of the future circular electron-positron collider (FCC-ee). The time-domain calculations of steady-state beam loading are presented and compared with frequency-domain analysis.

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO003

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WEP2PO006

Overview of the CERN PSB-to-PS Transfer Line Optics Matching Studies in View of the LHC Injectors Upgrade Project

272

V. Forte, S.C.P. Albright, W. Bartmann, G.P. Di Giovanni, M.A. Fraser, C. Heßler, A. Huschauer, A. Oeftiger
CERN, Geneva, Switzerland

At injection into the CERN Proton Synchrotron (PS) a significant horizontal emittance blow-up of the present high brightness beams for the LHC is observed. A partial contribution to this effect is suspected to be an important mismatch between the dispersion function in the transfer line from the PS Booster (PSB) and the ring itself. This mismatch will be unacceptable in view of the beam parameters requested by the LHC Injectors Upgrade (LIU) project with high longitudinal emittance and momentum spread. To deliver the requested beam parameters the PSB-to-PS transfer line will be upgraded and the optics in the line changed to improve the matching from all the four PSB rings. A re-matching campaign from the PSB ring 3 has been carried out to evaluate the impact of the present optics mismatch as a source of emittance growth both in simulations and measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO006

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WEP2PO007

Multi-Particle Simulations of the Future CERN PSB Injection Process with Updated Linac4 Beam Performance

278

V. Forte, C. Bracco, G.P. Di Giovanni, M.A. Fraser, A.M. Lombardi, B. Mikulec
CERN, Geneva, Switzerland

In the framework of the LHC Injectors Upgrade (LIU) project, the injection process in the CERN Proton Synchrotron Booster (PSB) will be renovated after the connection with the Linac4. A new H⁻ charge exchange injection system using a stripping foil is foreseen to increase the brightness of the stored beams and to provide high flexibility in terms of emittance tailoring at 160 MeV. Realistic multi-particle simulations of the future injection processes for high brightness beams (i.e. for the LHC) and high intensity beams (i.e. for the ISOLDE experiment) are presented in this paper. The simulations are based on the present performance of Linac4 and include scattering induced by the foil, space charge effects and compensation of the lattice perturbation introduced by the bumpers of the injection chicane.

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO007

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WEP2PO008

SPS Long Term Stability Studies in the Presence of Crab Cavities and High Order Multipoles

284

A. Alekou, H. Bartosik, R. Calaga, M. Carlà, Y. Papaphilippou
CERN, Geneva, Switzerland
R.B. Appleby, R.B. Appleby
UMAN, Manchester, United Kingdom
R.B. Appleby
Cockcroft Institute, Warrington, Cheshire, United Kingdom

A local Crab Cavity (CC) scheme will recover the head-on collisions at the IP of the High Luminosity LHC (HL-LHC), which aims to increase the LHC luminosity by a factor of 3-10. The tight space constraints at the CC location result in axially non-symmetric cavity designs that introduce high order multipole CC components. The impact of these high order components on the long term stability of the beam in the SPS machine, where two prototype crab cavities are presently installed in the CERN SPS to perform tests with beam, is presented. Furthermore, the Dynamic Aperture is studied in the presence of the SPS errors. Future plans are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO008

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WEP2PO011

Studies of Transverse Instabilities in the CERN SPS

291

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 Computer Science and Electrical Engineering, Rostock, Germany

In the framework of the LHC Injectors Upgrade (LIU), beams with about twice the intensity compared to the present values will have to be accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). Machine studies with intensity higher than the nominal LHC beam have shown that coherent instabilities in both transverse planes may develop at injection energy, potentially becoming a limitation for the future high intensity operation. In particular, a transverse mode coupling instability is encountered in the vertical plane, the threshold of which can be sufficiently increased by changing the machine optics. In addition, a headtail instability of individual bunches is observed in the horizontal plane in multi-bunch operation, which requires stabilization by high chromaticity. The PyHEADTAIL code has been used to check if the present SPS impedance model reproduces the experimental observations. The instability growth rates have been studied for different machine optics configurations and different chromaticity settings. Other stabilizing mechanisms like tune spread from octupoles or the transverse damper have also been investigated.

Poster WEP2PO011 [4.940 MB]

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WEP2PO018

Magnetic Field Tracking at CSNS/RCS

306

S.Y. Xu, S. Fu
IHEP, Beijing, People's Republic of China

Because of the differences of magnetic saturation and eddy current effects between different magnets, magnetic field tracking errors between different magnets is larger than 2.5 % at the Rapid Cycling Synchrotron (RCS) of Chinese Spallation Neutron Source (CSNS), and the induced tune shift is larger than 0.1. So larger tune shift may lead the beam to pass through the resonance lines. To reduce the magnetic field tracking errors, a method of wave form compensation for magnets of the Rapid Cycling Synchrotron was investigated on the magnets of CSNS/RCS. The wave form compensation was applied to CSNS/RCS commissioning. By performing wave form compensation, the maximum magnetic field tracking error was reduced from 2.5 % to 0.08 %, and the maximum tune shift over the ramping process was reduced from 0.1 to 0.004.

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO018

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WEP2PO024

Resonance Stop-bands Compensation at Booster Ring of HIAF

315

J. Li, J.C. Yang
IMP/CAS, Lanzhou, People's Republic of China

Booster Ring (BRing) of the new approved High Intensity heavy-ion Accelerator Facility (HIAF) in China is designed to stack 0.3-1.0·10¹¹ number of 238U³⁵⁺ ions by painting injection and deliver over such intensity beam in extraction. However, depressed tune spread caused by space charge effect crosses the low-order resonance stop-bands after bunching the storage beam. To keep a low beam loss during crossing, stop-band compensation scheme is proposed covering the whole process of RF capture and early acceleration.

Poster WEP2PO024 [1.218 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO024

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