HB2016 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
MOPR016	Mitigation of Numerical Noise for Beam Loss Simulations	simulation, emittance, ion, proton	90
	F. Kesting IAP, Frankfurt am Main, Germany G. Franchetti GSI, Darmstadt, Germany
	Numerical noise emerges in self-consistent simulations of charged particles, and its mitigation is investigated since the first numerical studies in plasma physics. In accelerator physics, recent studies find an artificial diffusion of the particle beam due to numerical noise in particle-in-cell tracking, which is of particular importance for high intensity machines with a long storage time, as the SIS100 at FAIR or in context of the LIU upgrade at CERN. In beam loss simulations for these projects artificial effects must be distinguished from physical beam loss. Therefore, it is important to relate artificial diffusion to artificial beam loss, and to choose simulation parameters such that physical beam loss is well resolved. As a practical tool, we therefore suggest a scaling law to find optimal simulation parameters for a given maximum percentage of acceptable artificial beam loss.
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MOPR021	Overview of the ESSnuSB Accumulator Ring	emittance, linac, injection, simulation	105
	M. Olvegård, T.J.C. Ekelöf Uppsala University, Uppsala, Sweden E. Benedetto, M. Cieslak-Kowalska, M. Martini, H.O. Schönauer, E.H.M. Wildner CERN, Geneva, Switzerland
	The European Spallation Source (ESS) is a research center based on the world’s most powerful proton driver, 2.0 GeV, 5 MW on target, currently under construction in Lund. With an increased pulse frequency, the ESS linac could deliver additional beam pulses to a neutrino target, thus giving an excellent opportunity to produce a high-performance ESS neutrino Super-Beam (ESSnuSB). The focusing system surrounding the neutrino target requires short proton pulses. An accumulator ring and acceleration of an H⁻ beam in the linac for charge-exchange injection into the accumulator could provide such short pulses. In this paper we present an overview of the work with optimizing the accumulator design and the challenges of injecting and storing 1.10¹⁵ protons per pulse from the linac. In particular, particle tracking simulations with space charge will be described.
	Poster MOPR021 [2.731 MB]
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MOPR022	Longitudinal Particle Tracking Code for a High Intensity Proton Synchrotron	emittance, acceleration, synchrotron, beam-loading	110
	M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	We have been developing a longitudinal particle tracking code to design and investigate the beam behavior of the J-PARC proton synchrotrons. The code calculate the longitudinal particle motion with a wake voltage and a space charge effect. The most different point from the other codes is that a synchronous particle motion is calculated from the bending magnetic field pattern. This means the synchronous particle is independent from an acceleration frequency pattern. This feature is useful to check the adiabaticity of the synchrotron. The code also calculates the longitudinal emittance and the filling factor at an rf bucket under the multi-harmonics. We will describe the feature of the code.
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MOPR023	Interpretation of Wire-Scanner Asymmetric Profiles in a Low-Energy Ring	emittance, scattering, simulation, booster	115
	M. Cieslak-Kowalska, E. Benedetto CERN, Geneva, Switzerland
	In the CERN PS Booster, wire-scanner profile measurements performed at injection energy are affected by a strong asymmetry. The shape was reproduced with the code pyOrbit, assuming that the effect is due to the beam evolution during the scans, under the influence of space-charge forces and Multiple Coulomb Scattering at the wire itself. Reproducing the transverse profiles during beam evolution allows to use them reliably as input for simulation benchmarking.
	Poster MOPR023 [0.482 MB]
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MOPR024	General Formula to Deduce the Space Charge Tune Spread From a Quadrupolar Pick-Up Measurement	coupling, resonance, pick-up, kicker	120
	E. Métral CERN, Geneva, Switzerland
	In 1966, W. Hardt derived the oscillation frequencies obtained in the presence of space charge forces and gradients errors for elliptical beams. Since then, a simple formula is usually used to relate the shift of the quadrupolar mode (obtained from the quadrupolar pick-up) and the space charge tune spread, depending only on the ratio between the two transverse equilibrium beam sizes. However, this formula is not always valid, in particular for machines running close to the coupling resonance Qx = Qy with almost round beams. A new general formula is presented, giving the space charge tune spread as a function of i) the measured shift of the quadrupolar mode, ii) the ratio between the two transverse equilibrium beam sizes and iii) the distance between the two transverse tunes.
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MOPR025	Space Charge Modules for PyHEADTAIL	GPU, simulation, emittance, vacuum	124
	A. Oeftiger CERN, Geneva, Switzerland S. Hegglin ETH, Zurich, Switzerland
	Funding: CERN, Doctoral Studentship and EPFL, Doctorate PyHEADTAIL is a 6D tracking tool developed at CERN to simulate collective effects. We present recent developments of the direct space charge suite, which is available for both the CPU and GPU. A new 3D particle-in-cell solver with open boundary conditions has been implemented. For the transverse plane, there is a semi-analytical Bassetti-Erskine model as well as 2D self-consistent particle-in-cell solvers with both open and closed boundary conditions. For the longitudinal plane, PyHEADTAIL offers line density derivative models. Simulations with these models are benchmarked with experiments at the injection plateau of CERN's Super Proton Synchrotron.
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MOPR026	Space Charge Mitigation With Longitudinally Hollow Bunches	synchrotron, resonance, emittance, injection	130
	A. Oeftiger, S. Hancock, G. Rumolo CERN, Geneva, Switzerland
	Funding: CERN, Doctoral Studentship and EPFL, Doctorate Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN's PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.
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MOPR028	CERN PS Booster Longitudinal Dynamics Simulations for the Post-LS2 Scenario	emittance, injection, simulation, impedance	140
	D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	The CERN PS Booster is the first synchrotron in the LHC proton injection chain, it currently accelerates particles from 50 MeV to 1.4 GeV kinetic energy. Several upgrades foreseen by the LHC Injectors Upgrade Program will allow the beam to be accelerated from 160 MeV to 2 GeV after Long Shutdown 2 in 2021. The present RF systems will be replaced by a new one, based on Finemet technology. These and other improvements will help to increase the LHC luminosity by a factor of ten. In order to study beam stability in the longitudinal plane simulations have been performed with the CERN BLonD code, using an accurate longitudinal impedance model and a reliable estimation of the longitudinal space charge. Particular attention has been dedicated to the three main features that currently let the beam go stably through the ramp: Double RF operation in bunch-lengthening mode to reduce the transverse space charge tune spread, exploitation of feedback loops to damp dipole oscillations, and controlled longitudinal emittance blow-up. RF phase noise injection has been considered to study if it could complement or substitute the currently used method based on sinusoidal phase modulation.
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MOPR029	On the Impact of Non-Symplecticity of Space Charge Solvers	emittance, simulation, optics, resonance	146
	M. Titze CERN, Geneva, Switzerland
	Funding: German Federal Ministry of Education and Research (BMBF) To guarantee long-term reliability in the predictions of a numerical integrator, it is a well-known requirement that the underlying map has to be symplectic. It is therefore important to examine in detail the impact on emittance growth and noise generation in case this condition is violated. We present a strategy of how to tackle this question and some results obtained for particular PIC and frozen space charge models.
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MOPR030	Simple Models for Beam Loss Near the Half Integer Resonance with Space Charge	resonance, simulation, lattice, coherent-effects	150
	C.M. Warsop, D.J. Adams, B. Jones, B.G. Pine STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The half integer resonance is often used to define the high intensity limit of medium or low energy hadron rings where transverse space charge is significant. However, the mechanism leading to particle loss as beam approaches this resonance, which thus defines the limit, is not clearly understood. In this paper we explore simple models, based on single particle resonance ideas, to see if they describe useful aspects of motion as observed in simulations and experiments of 2D coasting beams on the ISIS synchrotron. Single particle behaviour is compared to 2D self-consistent models to assess when coherent motion begins to affect the single particle motion, and understand the relevance of coherent and incoherent resonance. Whilst the general problem of 2D resonant loss, with non-stationary distributions and non-linear fields is potentially extremely complicated, here we suggest that for a well-designed machine, where higher order pathological loss effects are avoided, a relatively simple model may give valuable insights into beam behaviour and control.
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MOPR031	Development of Physics Models of the ISIS Head-Tail Instability	impedance, simulation, synchrotron, acceleration	155
	R.E. Williamson, B. Jones, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron which accelerates 3·10¹³ protons per pulse (ppp) from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high intensity, loss-limited machine, research and development at ISIS is focused on understanding loss mechanisms with a view to improving operational performance and guiding possible upgrade routes. The head-tail instability observed on ISIS is of particular interest as it is currently a main limitation on beam intensity. Good models of impedance are essential for understanding instabilities and to this end, recent beam-based measurements of the effective transverse impedance of the ISIS synchrotron are presented. This paper also presents developments of a new, in-house code to simulate the head-tail instability observed and includes benchmarks against theory and comparisons with experimental results.
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MOPR034	Suppression of Half-Integer Resonance in Fermilab Booster	lattice, booster, resonance, optics	164
	V.A. Lebedev, A. Valishev Fermilab, Batavia, Illinois, USA
	The particle losses at injection in the FNAL Booster are one of the major factors limiting the machine performance. The losses are caused by motion non-linearity due to direct space charge and due to non-linearity introduced by large values of chromaticity sextupoles required to suppress transverse instabilities. The report aims to address the former - the suppression of incoherent space charge effects by reducing deviations from the perfect periodicity of linear optics functions. It should be achieved by high accuracy optics measurements with subsequent optics correction and by removing known sources of optics perturbations. The study shows significant impact of optics correction on the half-integer stop band with subsequent reduction of particle loss. We use realistic Booster lattice model to understand the present limitations, and investigate the possible improvements which would allow high intensity operation with PIP-II parameters.
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MOPR035	Electron Lens for the Fermilab Integrable Optics Test Accelerator	electron, solenoid, optics, gun	170
	G. Stancari, A.V. Burov, K. Carlson, D.J. Crawford, V.A. Lebedev, J.R. Leibfritz, M.W. McGee, S. Nagaitsev, L.E. Nobrega, C.S. Park, E. Prebys, A.L. Romanov, J. Ruan, V.D. Shiltsev, Y.-M. Shin, J.C.T. Thangaraj, A. Valishev Fermilab, Batavia, Illinois, USA D. Noll IAP, Frankfurt am Main, Germany Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy. The Integrable Optics Test Accelerator (IOTA) is a research machine currently being designed and built at Fermilab. The research program includes the study of nonlinear integrable lattices, beam dynamics with self fields, and optical stochastic cooling. One section of the ring will contain an electron lens, a low-energy magnetized electron beam overlapping with the circulating beam. The electron lens can work as a nonlinear element, as an electron cooler, or as a space-charge compensator. We describe the physical principles, experiment design, and hardware implementation plans for the IOTA electron lens.
	Poster MOPR035 [5.399 MB]
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MOPL004	Beam Dynamics Simulations and Code Comparison for a New CW RFQ Design	rfq, linac, simulation, focusing	188
	S.M. Polozov, W.A. Barth, T. Kulevoy, S. Yaramyshev MEPhI, Moscow, Russia W.A. Barth, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth HIM, Mainz, Germany T. Kulevoy ITEP, Moscow, Russia
	Research and development of CW applications is an important step in RFQ design. The RF potential should be limited by 1.3-1.5 of Kilpatrick criterion for the CW mode. A 2 MeV RFQ is under development for the compact CW research proton accelerator, as well as for planned driver linac* in Russia. The maximum beam current is fixed to10 mA; the operating frequency has been set to 162 MHz. The new RFQ linac design will be presented and beam dynamics simulation results will be discussed. Calculations of beam dynamics are provided using the codes BEAMDULAC (developed at MEPhI for linac design) and DYNAMION. A comparison of the software performance is presented. * A.Y. Aksentyev, T.V. Kulevoy, S.M. Polozov. Proc. of IPAC’14, pp. 3286-3288.
	Poster MOPL004 [2.609 MB]
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MOPL006	Beam Dynamics Study of C-Ads Injector-I With Developing P-Topo Code	rfq, simulation, emittance, lattice	195
	Zh.C. Liu, C. Li, Q. Qin, F. Yan, Y.L. Zhao IHEP, Beijing, People's Republic of China
	A parallelized, time-dependent 3D particle simulation code is under developing to study the high-intensity beam dynamics in linear accelerators. The self-consistent space charge effect is taken into account with the Particle-In-Cell (PIC) method. In this paper, the structure of program and the parallel strategy are demonstrated. Then, we show the results of code verification and benchmarking. It is proved that the solvers in P-TOPO code and parallel strategy are reliable and efficient. Finally, the beam dynamics simulation of C-ADS Injector-I at IHEP are launched with P-TOPO and other codes. The possible reasons for the differences between results given by separated codes are also proposed.
	Poster MOPL006 [2.169 MB]
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MOPL021	Fermilab Booster Transition Crossing Simulations and Beam Studies	booster, quadrupole, proton, simulation	242
	C.M. Bhat, C.-Y. Tan Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy The Fermiab Booster accelerates beam from 400 MeV to 8 GeV at 15 Hz. In the PIP (Proton Improvement Plan) era, it is required that Booster deliver 4.2·10¹² protons per pulse to extraction. One of the obstacles for providing quality beam to the users is the longitudinal quadrupole oscillation that the beam suffers from right after transition. Although this oscillation is well taken care of with quadrupole dampers, it is important to understand the source of these oscillation in light of the PIP II requirements that require 6.5·10¹² protons per pulse at extraction. This paper explores the results from computer simulations, machine studies and solutions to prevent the quadrupole oscillation after transition. Author would like to thank S. Chaurize, C. Drennan, W. Pellico, K. Seiya, T. Sullivan and K. Triplett
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TUAM5X01	Space Charge Driven Beam Loss for Cooled Beams and Mitigation Measures in the CERN Low Energy Ion Ring	resonance, injection, ion, sextupole	272
	H. Bartosik, S. Hancock, A. Huschauer, V. Kain CERN, Geneva, Switzerland
	The performance of the CERN Low Energy Ion Ring (LEIR) with electron cooled lead ion beams is presently limited by losses, which occur during RF capture and the first part of acceleration. Extensive experimental studies performed in 2015 indicate that the losses are caused by the interplay of betatron resonances and the direct space charge detuning, which is significantly enhanced during bunching. Mitigation measures have already been identified and successfully tested, such as reducing the peak line charge density after RF capture, i.e. increasing the rms longitudinal emittance, and compensating third order resonances using existing harmonic sextupole correctors. New record intensities at extraction have been achieved. This talk describes the main experimental results from the 2015 measurement campaign including already implemented mitigation measures and the proposed strategy for even further increasing the LEIR intensity reach in the future.
	Slides TUAM5X01 [8.803 MB]
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TUAM6X01	First Analysis of the Space Charge Effects on a Third Order Coupled Resonance	resonance, emittance, synchrotron, simulation	278
	G. Franchetti GSI, Darmstadt, Germany S.S. Gilardoni, A. Huschauer, F. Schmidt, R. Wasef CERN, Geneva, Switzerland
	The effect of space charge on bunches stored for long term in a nonlinear lattice can be severe for beam survival. This may be the case in projects as SIS100 at GSI or LIU at CERN. In 2012, for the first time, the effect of space charge on a normal third order coupled resonance was investigated at the CERN-PS. The experimental results have highlighted an unprecedented asymmetric beam response: in the vertical plane the beam exhibits a thick halo, while the horizontal profile has only core growth. The quest for explaining these results requires a journey through the 4 dimensional dynamics of the coupled resonance investigating the fixed-lines, and requires a detailed code-experiment benchmarking also including beam profile benchmarking. This proceeding gives a short summary of the experimental results of the 2012 PS measurements, and address an interpretation based on the dynamics the fixed-lines.
	Slides TUAM6X01 [7.183 MB]
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TUAM7X01	Intensity Effects in the Formation of Stable Islands in Phase Space During the Multi-Turn Extraction Process at the CERN PS	simulation, vacuum, closed-orbit, extraction	283
	S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom S.S. Gilardoni, M. Giovannozzi, S. Hirlaender, A. Huschauer CERN, Geneva, Switzerland C.R. Prior STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The CERN PS utilises a multi-turn extraction (MTE) scheme to stretch the beam pulse length to optimise the filling process of the SPS. MTE is a novel technique to split a beam in transverse phase space into nonlinear stable islands. The recent experimental results indicate that the positions of the islands depend on the total beam intensity. Particle simulations have been performed to understand the detailed mechanism of the intensity dependence. The analysis carried out so far suggests space charge effects through image charges and image currents on the vacuum chamber and the magnets’ iron cores dominate the observed behaviour. In this talk, the latest analysis with realistic modelling of the beam environment is discussed and it is shown how this further improves the understanding of intensity effects in MTE.
	Slides TUAM7X01 [1.682 MB]
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TUPM4Y01	IFMIF-EVEDA RFQ, Measurement of Beam Input Conditions and Preparation to Beam Commissioning	rfq, emittance, simulation, solenoid	338
	M. Comunian, L. Bellan, E. Fagotti, A. Pisent INFN/LNL, Legnaro (PD), Italy L. Bellan Univ. degli Studi di Padova, Padova, Italy
	The commissioning phase of the IFMIF-EVEDA RFQ requires a complete beam characterization with simulations and measurements of the beam input from the IFMIF-EVEDA ion source and LEBT, in order to reach the RFQ input beam parameters. In this article the simulations of source LEBT RFQ will be reported with the corresponding set of measurements done on the Ion source and LEBT.
	Slides TUPM4Y01 [7.230 MB]
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WEAM1X01	Code Bench-Marking for Long-Term Tracking and Adaptive Algorithms	emittance, simulation, resonance, experiment	357
	F. Schmidt, H. Bartosik, A. Huschauer, A. Oeftiger, M. Titze CERN, Geneva, Switzerland Y.I. Alexahin, J.F. Amundson, V.V. Kapin, E.G. Stern Fermilab, Batavia, Illinois, USA G. Franchetti GSI, Darmstadt, Germany J.A. Holmes ORNL, Oak Ridge, Tennessee, USA
	At CERN we have ramped up a program to investigate space charge effects in the LHC pre-injectors with high brightness beams and long storage times. This in view of the LIU upgrade project for these accelerators. These studies require massive simulation over large number of turns. To this end we have been looking at all available codes and started collaborations on code development with several laboratories: pyORBIT from SNS, SYNERGIA from Fermilab, MICROMAP from GSI and our in-house MAD-X code with an space charge upgrade. We have agreed with our collaborators to bench-mark all these codes in the framework of the GSI bench-marking suite, in particular the main types of frozen space charge and PIC codes are being tested. We also include a study on the subclass of purely frozen and the adaptive frozen modes both part of MAD-X in comparison with the purely frozen MICROMAP code. Last, we will report on CERN's code development effort to understand and eventually overcome the noise issue in PIC codes. J. Coupard et al., ‘‘LHC Injectors Upgrade, Technical Design Report, Vol. I: Protons'', LIU Technical Design Report (TDR), CERN-ACC-2014-0337.
	Slides WEAM1X01 [2.348 MB]
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WEAM3X01	Code Development for Collective Effects	simulation, electron, interface, synchrotron	362
	K.S.B. Li, H. Bartosik, G. Iadarola, A. Oeftiger, A. Passarelli, A. Romano, G. Rumolo, M. Schenk CERN, Geneva, Switzerland S. Hegglin ETH, Zurich, Switzerland A. Oeftiger, M. Schenk EPFL, Lausanne, Switzerland
	The presentation will cover approaches and strategies of modeling and implementing collective effects in modern simulation codes. We will review some of the general approaches to numerically model collective beam dynamics in circular accelerators. We will then look into modern ways of implementing collective effects with a focus on plainness, modularity and flexibility, using the example of the PyHEADTAIL framework, and highlight some of the advantages and drawbacks emerging from this method. To ameliorate one of the main drawbacks, namely a potential loss of performance compared to the classical fully compiled codes, several options for speed improvements will be mentioned and discussed. Finally some examples and application will be shown together with future plans and perspectives.
	Slides WEAM3X01 [65.643 MB]
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WEPM7X01	The Application of the Optimization Algorithm in the Collimation System for CSNS/RCS	collimation, acceleration, simulation, emittance	397
	H.F. Ji, M.Y. Huang, Y. Jiao, N. Wang, S. Wang, S.Y. Xu IHEP, Beijing, People's Republic of China
	The robust conjugate direction search (RCDS) method, which is developed by X. Huang from the SLAC National Accelerator Laboratory, has high tolerance against noise in beam experiments and thus can find an optimal solution effectively and efficiently. In this paper, the RCDS method is used to optimize the beam collimation system for Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS). A two-stage beam collimation system was designed to localize the beam loss in the collimation section in CSNS/RCS. The parameters of secondary collimators are optimized with RCDS algorithm based on detailed tracking with the ORBIT program for a better performance of the collimation system. The study presents a way to quickly find an optimal parameter combination of the secondary collimators for a machine model for preparation for CSNS/RCS commissioning.
	Slides WEPM7X01 [1.137 MB]
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WEAM5Y01	Analyzing and Matching of Mixed High Intensity Highly Charged Ion Beams	ion, solenoid, ion-source, simulation	422
	X.H. Zhang, C. Qian, L.T. Sun, Y. Yang, X. Yin, Y.J. Yuan, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	Funding: Work supported by the National Natural Science Foundation of China (No. 11575265, 11427904) and the “973” Program of China (No. 2014CB845501). Electron cyclotron resonance (ECR) ion sources are widely used in heavy ion accelerators for their advantages in producing high quality intense beams of highly charged ions. However, it exists challenges in the design of the Q/A selection systems for mixed high intensity ion beams to reach sufficient Q/A resolution while controlling the beam emittance growth. Moreover, as the emittance of beam from ECR ion sources is coupled, the matching of phase space to post accelerator, for a wide range of ion beam species with different intensities, should be carefully studied. In this paper, the simulation and experimental results of the Q/A selection system at the LECR4 platform are shown. The formation of hollow cross section heavy ion beam at the end of the Q/A selector is revealed. A reasonable interpretation has been proposed, a modified design of the Q/A selection system has been committed for HIRFL-SSC linac injector. The features of the new design including beam simulations and experiment results are also presented.
	Slides WEAM5Y01 [3.244 MB]
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WEPM1Y01	Emittance Reconstruction Techniques in Presence of Space Charge Applied During the Linac4 Beam Commissioning	linac, emittance, diagnostics, DTL	433
	V.A. Dimov, J.-B. Lallement, A.M. Lombardi CERN, Geneva, Switzerland R. Gaur RRCAT, Indore, India
	The classical emittance reconstruction technique, based on analytic calculations using transfer matrices and beam profile measurements, is reliable only if the emittance is conserved and the space charge forces are negligible in the beamline between the reconstruction and measurement points. The effects of space charge forces prevent this method from giving sound results up to a relativistic beta of about 0.5 and make it inapplicable to the Linac4 commissioning at 50 and 100 MeV. To compensate for this drawback we have developed a dedicated technique, the forward method, which extends the classical method by combining it with an iterative process of multiparticle tracking including space charge forces. The forward method, complemented with a tomographic reconstruction routine, has been applied to transverse and longitudinal emittance reconstruction during the Linac4 beam commissioning. In this paper we describe the reconstruction process and its application during Linac4 beam commissioning.
	Slides WEPM1Y01 [1.923 MB]
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WEPM2Y01	Model Benchmark With Experiment at the SNS Linac	cavity, linac, lattice, laser	439
	A.P. Shishlo, A.V. Aleksandrov, M.A. Plum ORNL, Oak Ridge, Tennessee, USA Y. Liu ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The history of attempts to perform a transverse matching in the SNS superconducting linac (SCL) is discussed. The SCL has 9 laser wire (LW) stations to perform nondestructive measurements of the transverse beam profiles. Any matching starts with the measurement of the initial Twiss parameters which in the SNS case was done by using the first four LW stations at the beginning of the superconducting linac. For years the consistency between all LW stations data could not be achieved. This problem was resolved only after significant improvements in accuracy of the phase scans of the SCL cavities, more precise analysis of all available scan data, better optics planning, and the initial longitudinal Twiss parameters measurements. The presented paper discusses in details these developed procedures.
	Slides WEPM2Y01 [2.815 MB]
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WEPM5Y01	H⁻ Beam Dynamics Study of a LEBT in XiPAF Project with the WARP PIC Code	simulation, ion, rfq, proton	449
	R. Ruo, L. Du, T.B. Du, X. Guan, C.-X. Tang, X.W. Wang, Q.Z. Xing, H.Y. Zhang, Q.Z. Zhang TUB, Beijing, People's Republic of China Y. He, J. Li NUCTECH, Beijing, People's Republic of China
	The 7 MeV H⁻ linac injector of Xi‘an Proton Application Facility (XiPAF) is composed of an ECR ion source, a Low Energy Beam Transport line (LEBT), a Radio Frequency Quadrupole accelerator (RFQ) and a Drift Tube Linac (DTL). The 1.7 m-long LEBT is used for matching a 40 μs pulse width 6 mA peak current beam to the entrance of the RFQ accelerator. The peak current and pulse-width of the 50 keV H⁻ beam extracted from the ion source is 10 mA and 1 ms respectively. In the LEBT, an adjustable aperture is used for scraping the peak current of the beam to 6 mA, and an electric chopper is used for chopping the beam pulse width to 40 μs. These elements make the space charge compensation problem more complicated. A careful simulation of the space charge compensation problem of the H⁻ beam has been done by considering the beam particles interacting with the residual gas with the help of WARP PIC code. To achieve the requirements of the LEBT in XiPAF, the type and pressure of the residual gas is given according to the simulation results.
	Slides WEPM5Y01 [5.926 MB]
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WEPM6Y01	Study on Space Charge Compensation of Low Energy High Intensity Ion Beam in Peking University	ion, simulation, experiment, ion-source	453
	S.X. Peng, J.E. Chen, Z.Y. Guo, H.T. Ren, J.M. Wen, W.B. Wu, Y. Xu, A.L. Zhang, J.F. Zhang, T. Zhang PKU, Beijing, People's Republic of China J.E. Chen Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China H.T. Ren FRIB, East Lansing, Michigan, USA A.L. Zhang University of Chinese Academy of Sciences, Beijing, People's Republic of China
	To better understand the space charge compensation processes in low energy high intensity beam transportation, numerical study and experimental simulation on H⁺ beam and H⁻ beam were carried out at Peking University (PKU). The numerical simulation is done with a PIC-MCC model [1] whose computing framework was done with the 3D MATLAB PIC code bender [2], and the impacts among particles were done with Monte Carlo collision via null-collision method [3]. Issues, such as beam loss caused by collisions in H⁺, H⁻ beam and ion-electron instability related to decompensation and overcompensation in H⁻ beam, are carefully treated in this model. The experiments were performed on PKU ion source test bench. Compensation gases were injected directly into the beam transportation region to modify the space charge compensation degree. The results obtained during the experiment are agree well with the numerical simulation ones for both H⁺ beam [1] and H⁻ beam [4]. Details will be presented in this paper.
	Slides WEPM6Y01 [5.625 MB]
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THPM1X01	Typology of Space Charge Resonances	resonance, emittance, lattice, focusing	486
	I. Hofmann GSI, Darmstadt, Germany
	The existence of structural space charge resonant effects in otherwise linear periodic focusing systems is well-known, but referred to in a variety of languages and contexts. We show here that for short bunched beams a ‘‘classification'' in two major groups is possible, e.g. parametric resonances or instabilities on the one hand and single particle type space charge resonances on the other hand. The primary feature of distinction is that for the former the driving space charge force initially exists on the noise level (rms or higher order mismatch) only and gets amplified parametrically, hence an entirely coherent response; for the latter the driving space charge multipole is part of the initial density profile and the coherent response is weak. In the extreme limit of KV beams only parametric resonances (instabilities) exist, and in principle in all orders. For waterbag or Gaussian distributions we find half-integer parametric resonances only up to fourth order, but evidence for single particle resonances in all orders up to tenth have been identified.
	Slides THPM1X01 [3.094 MB]
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THPM4X01	Resonances and Envelope Instability in High Intensity Linear Accelerators	resonance, lattice, linac, emittance	491
	D. Jeon, J.-H. Jang, H. Jin IBS, Daejeon, Republic of Korea
	Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the NRF of Korea under Contract 2013M7A1A1075764. Understanding of space charge effects has grown and recent studies have led to the findings of resonances of high intensity linear accelerators. Lately the sixth order resonance of high intensity linear accelerators was reported, along with the in-depth studies on the fourth order resonance and the envelope instability. Experiment studies on space charge resonances were reported. This paper reviews the resonances of high intensity linear accelerators such as the 4σ =360deg, and the 6σ =720deg resonances, along with the envelope instability.
	Slides THPM4X01 [3.279 MB]
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THPM5X01	Using an Electron Cooler for Space Charge Compensation in the GSI Synchrotron SIS18	electron, ion, experiment, focusing	496
	W.D. Stem, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim GSI, Darmstadt, Germany
	Funding: Work is supported by BMBF contract FKZ:05P15RDRBA For the future operation of the SIS18 as a booster synchrotron for the FAIR SIS100, space charge and beam lifetime are expected to be the main intensity limitations. Intensity is limited in part by the space-charge-induced incoherent tune shift in bunched beams. A co-propagating, low energy electron lens can compensate for this tune shift by applying opposing space-charge fields in the ion beam. In this paper, we study the effect of using the existing electron cooler at the SIS18 as a space charge compensation device. We anticipate beta beating may arise due to the singular localized focusing error, and explore the possibility of adding additional lenses to reduce this error. We also study the effect of electron lenses on the coherent (collective) and incoherent (single-particle) stopbands. Furthermore, we estimate the lifetime of partially stripped heavy-ions due to charge exchange process in the lens.
	Slides THPM5X01 [4.731 MB]
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THPM6X01	Space Charge Effects in FFAG	closed-orbit, lattice, betatron, emittance	499
	M. Haj Tahar, F. Méot BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Understanding space charge effects in FFAG is crucial in order to assess their potential for high power applications. This paper shows that, to carry out parametric studies of these effects in FFAG, the average field index of the focusing and defocusing magnets are the natural parametrization. Using several classes of particle distribution functions, we investigate the effects of space charge forces on the non-linear beam dynamics of FFAG and provide stability diagrams for an FFAG-like lattice. The method developed in this study is mainly applicable to systems with slowly varying parameters, i.e slow acceleration.
	Slides THPM6X01 [2.171 MB]
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THPM9X01	Space Charge Effects and Mitigation in the CERN PS Booster, in View of the Upgrade	injection, emittance, booster, simulation	517
	E. Benedetto, M. Cieslak-Kowalska, V. Forte, F. Schmidt CERN, Geneva, Switzerland M. Cieslak-Kowalska EPFL, Lausanne, Switzerland V. Forte Université Blaise Pascal, Clermont-Ferrand, France
	The CERN PS Booster (PSB) is presently running with a space-charge tune spread larger than 0.5 at injection. Since the High Luminosity LHC (HL-LHC) will require beams with twice the intensity and brightness of today, the LHC Injector Upgrade (LIU) Project is putting in place an upgrade program for all the injector chain and, in particular, it relies on the important assumption that the PS Booster can successfully produce these beams after the implementation of the 160 MeV H⁻ injection from Linac4. This contribution describes the studies (measurements and simulations) that have been carried out to confirm that the PSB can indeed perform as needed in terms of beam brightness for the future HL-LHC runs. The importance of the mitigation measures already in place, such as the correction of the half-integer line, and the effects of non-linear resonances on the beam are also discussed.
	Slides THPM9X01 [6.786 MB]
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THPM7Y01	A New RFQ Model and Symplectic Multi-Particle Tracking in the IMPACT Code Suite	rfq, simulation, proton, emittance	562
	J. Qiang LBNL, Berkeley, California, USA L. Li, Z. Wang PKU, Beijing, People's Republic of China
	The IMPACT code suite is a self-consistent parallel three-dimensional beam dynamics simulation toolbox that combines the magnetic optics method and the parallel particle-in-cell method. It has been widely used to study high intensity/high brightness beams in many accelerators. In this paper, we will report on recent improvements to the code such as the capability to model RFQ in time domain and symplectic multi-particle tracking with a gridless spectral solver for space-charge simulation.
	Slides THPM7Y01 [8.794 MB]
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FRAM2P01	Summary WG-A	resonance, electron, simulation, experiment	575
	W. Fischer BNL, Upton, Long Island, New York, USA Y.H. Chin KEK, Ibaraki, Japan G. Franchetti GSI, Darmstadt, Germany
	Friday Summary
	Slides FRAM2P01 [6.325 MB]
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Paper

Title

Other Keywords

Page

MOPR016

Mitigation of Numerical Noise for Beam Loss Simulations

simulation, emittance, ion, proton

90

F. Kesting
IAP, Frankfurt am Main, Germany
G. Franchetti
GSI, Darmstadt, Germany

Numerical noise emerges in self-consistent simulations of charged particles, and its mitigation is investigated since the first numerical studies in plasma physics. In accelerator physics, recent studies find an artificial diffusion of the particle beam due to numerical noise in particle-in-cell tracking, which is of particular importance for high intensity machines with a long storage time, as the SIS100 at FAIR or in context of the LIU upgrade at CERN. In beam loss simulations for these projects artificial effects must be distinguished from physical beam loss. Therefore, it is important to relate artificial diffusion to artificial beam loss, and to choose simulation parameters such that physical beam loss is well resolved. As a practical tool, we therefore suggest a scaling law to find optimal simulation parameters for a given maximum percentage of acceptable artificial beam loss.

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MOPR021

Overview of the ESSnuSB Accumulator Ring

emittance, linac, injection, simulation

105

M. Olvegård, T.J.C. Ekelöf
Uppsala University, Uppsala, Sweden
E. Benedetto, M. Cieslak-Kowalska, M. Martini, H.O. Schönauer, E.H.M. Wildner
CERN, Geneva, Switzerland

The European Spallation Source (ESS) is a research center based on the world’s most powerful proton driver, 2.0 GeV, 5 MW on target, currently under construction in Lund. With an increased pulse frequency, the ESS linac could deliver additional beam pulses to a neutrino target, thus giving an excellent opportunity to produce a high-performance ESS neutrino Super-Beam (ESSnuSB). The focusing system surrounding the neutrino target requires short proton pulses. An accumulator ring and acceleration of an H⁻ beam in the linac for charge-exchange injection into the accumulator could provide such short pulses. In this paper we present an overview of the work with optimizing the accumulator design and the challenges of injecting and storing 1.10¹⁵ protons per pulse from the linac. In particular, particle tracking simulations with space charge will be described.

Poster MOPR021 [2.731 MB]

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MOPR022

Longitudinal Particle Tracking Code for a High Intensity Proton Synchrotron

emittance, acceleration, synchrotron, beam-loading

110

M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

We have been developing a longitudinal particle tracking code to design and investigate the beam behavior of the J-PARC proton synchrotrons. The code calculate the longitudinal particle motion with a wake voltage and a space charge effect. The most different point from the other codes is that a synchronous particle motion is calculated from the bending magnetic field pattern. This means the synchronous particle is independent from an acceleration frequency pattern. This feature is useful to check the adiabaticity of the synchrotron. The code also calculates the longitudinal emittance and the filling factor at an rf bucket under the multi-harmonics. We will describe the feature of the code.

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MOPR023

Interpretation of Wire-Scanner Asymmetric Profiles in a Low-Energy Ring

emittance, scattering, simulation, booster

115

M. Cieslak-Kowalska, E. Benedetto
CERN, Geneva, Switzerland

In the CERN PS Booster, wire-scanner profile measurements performed at injection energy are affected by a strong asymmetry. The shape was reproduced with the code pyOrbit, assuming that the effect is due to the beam evolution during the scans, under the influence of space-charge forces and Multiple Coulomb Scattering at the wire itself. Reproducing the transverse profiles during beam evolution allows to use them reliably as input for simulation benchmarking.

Poster MOPR023 [0.482 MB]

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MOPR024

General Formula to Deduce the Space Charge Tune Spread From a Quadrupolar Pick-Up Measurement

coupling, resonance, pick-up, kicker

120

E. Métral
CERN, Geneva, Switzerland

In 1966, W. Hardt derived the oscillation frequencies obtained in the presence of space charge forces and gradients errors for elliptical beams. Since then, a simple formula is usually used to relate the shift of the quadrupolar mode (obtained from the quadrupolar pick-up) and the space charge tune spread, depending only on the ratio between the two transverse equilibrium beam sizes. However, this formula is not always valid, in particular for machines running close to the coupling resonance Qx = Qy with almost round beams. A new general formula is presented, giving the space charge tune spread as a function of i) the measured shift of the quadrupolar mode, ii) the ratio between the two transverse equilibrium beam sizes and iii) the distance between the two transverse tunes.

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MOPR025

Space Charge Modules for PyHEADTAIL

GPU, simulation, emittance, vacuum

124

A. Oeftiger
CERN, Geneva, Switzerland
S. Hegglin
ETH, Zurich, Switzerland

Funding: CERN, Doctoral Studentship and EPFL, Doctorate
PyHEADTAIL is a 6D tracking tool developed at CERN to simulate collective effects. We present recent developments of the direct space charge suite, which is available for both the CPU and GPU. A new 3D particle-in-cell solver with open boundary conditions has been implemented. For the transverse plane, there is a semi-analytical Bassetti-Erskine model as well as 2D self-consistent particle-in-cell solvers with both open and closed boundary conditions. For the longitudinal plane, PyHEADTAIL offers line density derivative models. Simulations with these models are benchmarked with experiments at the injection plateau of CERN's Super Proton Synchrotron.

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MOPR026

Space Charge Mitigation With Longitudinally Hollow Bunches

synchrotron, resonance, emittance, injection

130

A. Oeftiger, S. Hancock, G. Rumolo
CERN, Geneva, Switzerland

Funding: CERN, Doctoral Studentship and EPFL, Doctorate
Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN's PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

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MOPR028

CERN PS Booster Longitudinal Dynamics Simulations for the Post-LS2 Scenario

emittance, injection, simulation, impedance

140

D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

The CERN PS Booster is the first synchrotron in the LHC proton injection chain, it currently accelerates particles from 50 MeV to 1.4 GeV kinetic energy. Several upgrades foreseen by the LHC Injectors Upgrade Program will allow the beam to be accelerated from 160 MeV to 2 GeV after Long Shutdown 2 in 2021. The present RF systems will be replaced by a new one, based on Finemet technology. These and other improvements will help to increase the LHC luminosity by a factor of ten. In order to study beam stability in the longitudinal plane simulations have been performed with the CERN BLonD code, using an accurate longitudinal impedance model and a reliable estimation of the longitudinal space charge. Particular attention has been dedicated to the three main features that currently let the beam go stably through the ramp: Double RF operation in bunch-lengthening mode to reduce the transverse space charge tune spread, exploitation of feedback loops to damp dipole oscillations, and controlled longitudinal emittance blow-up. RF phase noise injection has been considered to study if it could complement or substitute the currently used method based on sinusoidal phase modulation.

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MOPR029

On the Impact of Non-Symplecticity of Space Charge Solvers

emittance, simulation, optics, resonance

146

M. Titze
CERN, Geneva, Switzerland

Funding: German Federal Ministry of Education and Research (BMBF)
To guarantee long-term reliability in the predictions of a numerical integrator, it is a well-known requirement that the underlying map has to be symplectic. It is therefore important to examine in detail the impact on emittance growth and noise generation in case this condition is violated. We present a strategy of how to tackle this question and some results obtained for particular PIC and frozen space charge models.

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MOPR030

Simple Models for Beam Loss Near the Half Integer Resonance with Space Charge

resonance, simulation, lattice, coherent-effects

150

C.M. Warsop, D.J. Adams, B. Jones, B.G. Pine
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The half integer resonance is often used to define the high intensity limit of medium or low energy hadron rings where transverse space charge is significant. However, the mechanism leading to particle loss as beam approaches this resonance, which thus defines the limit, is not clearly understood. In this paper we explore simple models, based on single particle resonance ideas, to see if they describe useful aspects of motion as observed in simulations and experiments of 2D coasting beams on the ISIS synchrotron. Single particle behaviour is compared to 2D self-consistent models to assess when coherent motion begins to affect the single particle motion, and understand the relevance of coherent and incoherent resonance. Whilst the general problem of 2D resonant loss, with non-stationary distributions and non-linear fields is potentially extremely complicated, here we suggest that for a well-designed machine, where higher order pathological loss effects are avoided, a relatively simple model may give valuable insights into beam behaviour and control.

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MOPR031

Development of Physics Models of the ISIS Head-Tail Instability

impedance, simulation, synchrotron, acceleration

155

R.E. Williamson, B. Jones, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron which accelerates 3·10¹³ protons per pulse (ppp) from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high intensity, loss-limited machine, research and development at ISIS is focused on understanding loss mechanisms with a view to improving operational performance and guiding possible upgrade routes. The head-tail instability observed on ISIS is of particular interest as it is currently a main limitation on beam intensity. Good models of impedance are essential for understanding instabilities and to this end, recent beam-based measurements of the effective transverse impedance of the ISIS synchrotron are presented. This paper also presents developments of a new, in-house code to simulate the head-tail instability observed and includes benchmarks against theory and comparisons with experimental results.

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MOPR034

Suppression of Half-Integer Resonance in Fermilab Booster

lattice, booster, resonance, optics

164

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

The particle losses at injection in the FNAL Booster are one of the major factors limiting the machine performance. The losses are caused by motion non-linearity due to direct space charge and due to non-linearity introduced by large values of chromaticity sextupoles required to suppress transverse instabilities. The report aims to address the former - the suppression of incoherent space charge effects by reducing deviations from the perfect periodicity of linear optics functions. It should be achieved by high accuracy optics measurements with subsequent optics correction and by removing known sources of optics perturbations. The study shows significant impact of optics correction on the half-integer stop band with subsequent reduction of particle loss. We use realistic Booster lattice model to understand the present limitations, and investigate the possible improvements which would allow high intensity operation with PIP-II parameters.

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MOPR035

Electron Lens for the Fermilab Integrable Optics Test Accelerator

electron, solenoid, optics, gun

170

G. Stancari, A.V. Burov, K. Carlson, D.J. Crawford, V.A. Lebedev, J.R. Leibfritz, M.W. McGee, S. Nagaitsev, L.E. Nobrega, C.S. Park, E. Prebys, A.L. Romanov, J. Ruan, V.D. Shiltsev, Y.-M. Shin, J.C.T. Thangaraj, A. Valishev
Fermilab, Batavia, Illinois, USA
D. Noll
IAP, Frankfurt am Main, Germany
Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the US Department of Energy.
The Integrable Optics Test Accelerator (IOTA) is a research machine currently being designed and built at Fermilab. The research program includes the study of nonlinear integrable lattices, beam dynamics with self fields, and optical stochastic cooling. One section of the ring will contain an electron lens, a low-energy magnetized electron beam overlapping with the circulating beam. The electron lens can work as a nonlinear element, as an electron cooler, or as a space-charge compensator. We describe the physical principles, experiment design, and hardware implementation plans for the IOTA electron lens.

Poster MOPR035 [5.399 MB]

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MOPL004

Beam Dynamics Simulations and Code Comparison for a New CW RFQ Design

rfq, linac, simulation, focusing

188

S.M. Polozov, W.A. Barth, T. Kulevoy, S. Yaramyshev
MEPhI, Moscow, Russia
W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth
HIM, Mainz, Germany
T. Kulevoy
ITEP, Moscow, Russia

Research and development of CW applications is an important step in RFQ design. The RF potential should be limited by 1.3-1.5 of Kilpatrick criterion for the CW mode. A 2 MeV RFQ is under development for the compact CW research proton accelerator, as well as for planned driver linac* in Russia. The maximum beam current is fixed to10 mA; the operating frequency has been set to 162 MHz. The new RFQ linac design will be presented and beam dynamics simulation results will be discussed. Calculations of beam dynamics are provided using the codes BEAMDULAC (developed at MEPhI for linac design) and DYNAMION. A comparison of the software performance is presented.
* A.Y. Aksentyev, T.V. Kulevoy, S.M. Polozov. Proc. of IPAC’14, pp. 3286-3288.

Poster MOPL004 [2.609 MB]

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MOPL006

Beam Dynamics Study of C-Ads Injector-I With Developing P-Topo Code

rfq, simulation, emittance, lattice

195

Zh.C. Liu, C. Li, Q. Qin, F. Yan, Y.L. Zhao
IHEP, Beijing, People's Republic of China

A parallelized, time-dependent 3D particle simulation code is under developing to study the high-intensity beam dynamics in linear accelerators. The self-consistent space charge effect is taken into account with the Particle-In-Cell (PIC) method. In this paper, the structure of program and the parallel strategy are demonstrated. Then, we show the results of code verification and benchmarking. It is proved that the solvers in P-TOPO code and parallel strategy are reliable and efficient. Finally, the beam dynamics simulation of C-ADS Injector-I at IHEP are launched with P-TOPO and other codes. The possible reasons for the differences between results given by separated codes are also proposed.

Poster MOPL006 [2.169 MB]

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MOPL021

Fermilab Booster Transition Crossing Simulations and Beam Studies

booster, quadrupole, proton, simulation

242

C.M. Bhat, C.-Y. Tan
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy
The Fermiab Booster accelerates beam from 400 MeV to 8 GeV at 15 Hz. In the PIP (Proton Improvement Plan) era, it is required that Booster deliver 4.2·10¹² protons per pulse to extraction. One of the obstacles for providing quality beam to the users is the longitudinal quadrupole oscillation that the beam suffers from right after transition. Although this oscillation is well taken care of with quadrupole dampers, it is important to understand the source of these oscillation in light of the PIP II requirements that require 6.5·10¹² protons per pulse at extraction. This paper explores the results from computer simulations, machine studies and solutions to prevent the quadrupole oscillation after transition.
Author would like to thank S. Chaurize, C. Drennan, W. Pellico, K. Seiya, T. Sullivan and K. Triplett

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TUAM5X01

Space Charge Driven Beam Loss for Cooled Beams and Mitigation Measures in the CERN Low Energy Ion Ring

resonance, injection, ion, sextupole

272

H. Bartosik, S. Hancock, A. Huschauer, V. Kain
CERN, Geneva, Switzerland

The performance of the CERN Low Energy Ion Ring (LEIR) with electron cooled lead ion beams is presently limited by losses, which occur during RF capture and the first part of acceleration. Extensive experimental studies performed in 2015 indicate that the losses are caused by the interplay of betatron resonances and the direct space charge detuning, which is significantly enhanced during bunching. Mitigation measures have already been identified and successfully tested, such as reducing the peak line charge density after RF capture, i.e. increasing the rms longitudinal emittance, and compensating third order resonances using existing harmonic sextupole correctors. New record intensities at extraction have been achieved. This talk describes the main experimental results from the 2015 measurement campaign including already implemented mitigation measures and the proposed strategy for even further increasing the LEIR intensity reach in the future.

Slides TUAM5X01 [8.803 MB]

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TUAM6X01

First Analysis of the Space Charge Effects on a Third Order Coupled Resonance

resonance, emittance, synchrotron, simulation

278

G. Franchetti
GSI, Darmstadt, Germany
S.S. Gilardoni, A. Huschauer, F. Schmidt, R. Wasef
CERN, Geneva, Switzerland

The effect of space charge on bunches stored for long term in a nonlinear lattice can be severe for beam survival. This may be the case in projects as SIS100 at GSI or LIU at CERN. In 2012, for the first time, the effect of space charge on a normal third order coupled resonance was investigated at the CERN-PS. The experimental results have highlighted an unprecedented asymmetric beam response: in the vertical plane the beam exhibits a thick halo, while the horizontal profile has only core growth. The quest for explaining these results requires a journey through the 4 dimensional dynamics of the coupled resonance investigating the fixed-lines, and requires a detailed code-experiment benchmarking also including beam profile benchmarking. This proceeding gives a short summary of the experimental results of the 2012 PS measurements, and address an interpretation based on the dynamics the fixed-lines.

Slides TUAM6X01 [7.183 MB]

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TUAM7X01

Intensity Effects in the Formation of Stable Islands in Phase Space During the Multi-Turn Extraction Process at the CERN PS

simulation, vacuum, closed-orbit, extraction

283

S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
S.S. Gilardoni, M. Giovannozzi, S. Hirlaender, A. Huschauer
CERN, Geneva, Switzerland
C.R. Prior
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The CERN PS utilises a multi-turn extraction (MTE) scheme to stretch the beam pulse length to optimise the filling process of the SPS. MTE is a novel technique to split a beam in transverse phase space into nonlinear stable islands. The recent experimental results indicate that the positions of the islands depend on the total beam intensity. Particle simulations have been performed to understand the detailed mechanism of the intensity dependence. The analysis carried out so far suggests space charge effects through image charges and image currents on the vacuum chamber and the magnets’ iron cores dominate the observed behaviour. In this talk, the latest analysis with realistic modelling of the beam environment is discussed and it is shown how this further improves the understanding of intensity effects in MTE.

Slides TUAM7X01 [1.682 MB]

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TUPM4Y01

IFMIF-EVEDA RFQ, Measurement of Beam Input Conditions and Preparation to Beam Commissioning

rfq, emittance, simulation, solenoid

338

M. Comunian, L. Bellan, E. Fagotti, A. Pisent
INFN/LNL, Legnaro (PD), Italy
L. Bellan
Univ. degli Studi di Padova, Padova, Italy

The commissioning phase of the IFMIF-EVEDA RFQ requires a complete beam characterization with simulations and measurements of the beam input from the IFMIF-EVEDA ion source and LEBT, in order to reach the RFQ input beam parameters. In this article the simulations of source LEBT RFQ will be reported with the corresponding set of measurements done on the Ion source and LEBT.

Slides TUPM4Y01 [7.230 MB]

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WEAM1X01

Code Bench-Marking for Long-Term Tracking and Adaptive Algorithms

emittance, simulation, resonance, experiment

357

F. Schmidt, H. Bartosik, A. Huschauer, A. Oeftiger, M. Titze
CERN, Geneva, Switzerland
Y.I. Alexahin, J.F. Amundson, V.V. Kapin, E.G. Stern
Fermilab, Batavia, Illinois, USA
G. Franchetti
GSI, Darmstadt, Germany
J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA

At CERN we have ramped up a program to investigate space charge effects in the LHC pre-injectors with high brightness beams and long storage times. This in view of the LIU upgrade project for these accelerators. These studies require massive simulation over large number of turns. To this end we have been looking at all available codes and started collaborations on code development with several laboratories: pyORBIT from SNS, SYNERGIA from Fermilab, MICROMAP from GSI and our in-house MAD-X code with an space charge upgrade. We have agreed with our collaborators to bench-mark all these codes in the framework of the GSI bench-marking suite, in particular the main types of frozen space charge and PIC codes are being tested. We also include a study on the subclass of purely frozen and the adaptive frozen modes both part of MAD-X in comparison with the purely frozen MICROMAP code. Last, we will report on CERN's code development effort to understand and eventually overcome the noise issue in PIC codes.
J. Coupard et al., ‘‘LHC Injectors Upgrade,
Technical Design Report, Vol. I: Protons'', LIU Technical Design
Report (TDR), CERN-ACC-2014-0337.

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WEAM3X01

Code Development for Collective Effects

simulation, electron, interface, synchrotron

362

K.S.B. Li, H. Bartosik, G. Iadarola, A. Oeftiger, A. Passarelli, A. Romano, G. Rumolo, M. Schenk
CERN, Geneva, Switzerland
S. Hegglin
ETH, Zurich, Switzerland
A. Oeftiger, M. Schenk
EPFL, Lausanne, Switzerland

The presentation will cover approaches and strategies of modeling and implementing collective effects in modern simulation codes. We will review some of the general approaches to numerically model collective beam dynamics in circular accelerators. We will then look into modern ways of implementing collective effects with a focus on plainness, modularity and flexibility, using the example of the PyHEADTAIL framework, and highlight some of the advantages and drawbacks emerging from this method. To ameliorate one of the main drawbacks, namely a potential loss of performance compared to the classical fully compiled codes, several options for speed improvements will be mentioned and discussed. Finally some examples and application will be shown together with future plans and perspectives.

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WEPM7X01

The Application of the Optimization Algorithm in the Collimation System for CSNS/RCS

collimation, acceleration, simulation, emittance

397

H.F. Ji, M.Y. Huang, Y. Jiao, N. Wang, S. Wang, S.Y. Xu
IHEP, Beijing, People's Republic of China

The robust conjugate direction search (RCDS) method, which is developed by X. Huang from the SLAC National Accelerator Laboratory, has high tolerance against noise in beam experiments and thus can find an optimal solution effectively and efficiently. In this paper, the RCDS method is used to optimize the beam collimation system for Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS). A two-stage beam collimation system was designed to localize the beam loss in the collimation section in CSNS/RCS. The parameters of secondary collimators are optimized with RCDS algorithm based on detailed tracking with the ORBIT program for a better performance of the collimation system. The study presents a way to quickly find an optimal parameter combination of the secondary collimators for a machine model for preparation for CSNS/RCS commissioning.

Slides WEPM7X01 [1.137 MB]

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WEAM5Y01

Analyzing and Matching of Mixed High Intensity Highly Charged Ion Beams

ion, solenoid, ion-source, simulation

422

X.H. Zhang, C. Qian, L.T. Sun, Y. Yang, X. Yin, Y.J. Yuan, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

Funding: Work supported by the National Natural Science Foundation of China (No. 11575265, 11427904) and the “973” Program of China (No. 2014CB845501).
Electron cyclotron resonance (ECR) ion sources are widely used in heavy ion accelerators for their advantages in producing high quality intense beams of highly charged ions. However, it exists challenges in the design of the Q/A selection systems for mixed high intensity ion beams to reach sufficient Q/A resolution while controlling the beam emittance growth. Moreover, as the emittance of beam from ECR ion sources is coupled, the matching of phase space to post accelerator, for a wide range of ion beam species with different intensities, should be carefully studied. In this paper, the simulation and experimental results of the Q/A selection system at the LECR4 platform are shown. The formation of hollow cross section heavy ion beam at the end of the Q/A selector is revealed. A reasonable interpretation has been proposed, a modified design of the Q/A selection system has been committed for HIRFL-SSC linac injector. The features of the new design including beam simulations and experiment results are also presented.

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WEPM1Y01

Emittance Reconstruction Techniques in Presence of Space Charge Applied During the Linac4 Beam Commissioning

linac, emittance, diagnostics, DTL

433

V.A. Dimov, J.-B. Lallement, A.M. Lombardi
CERN, Geneva, Switzerland
R. Gaur
RRCAT, Indore, India

The classical emittance reconstruction technique, based on analytic calculations using transfer matrices and beam profile measurements, is reliable only if the emittance is conserved and the space charge forces are negligible in the beamline between the reconstruction and measurement points. The effects of space charge forces prevent this method from giving sound results up to a relativistic beta of about 0.5 and make it inapplicable to the Linac4 commissioning at 50 and 100 MeV. To compensate for this drawback we have developed a dedicated technique, the forward method, which extends the classical method by combining it with an iterative process of multiparticle tracking including space charge forces. The forward method, complemented with a tomographic reconstruction routine, has been applied to transverse and longitudinal emittance reconstruction during the Linac4 beam commissioning. In this paper we describe the reconstruction process and its application during Linac4 beam commissioning.

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WEPM2Y01

Model Benchmark With Experiment at the SNS Linac

cavity, linac, lattice, laser

439

A.P. Shishlo, A.V. Aleksandrov, M.A. Plum
ORNL, Oak Ridge, Tennessee, USA
Y. Liu
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The history of attempts to perform a transverse matching in the SNS superconducting linac (SCL) is discussed. The SCL has 9 laser wire (LW) stations to perform nondestructive measurements of the transverse beam profiles. Any matching starts with the measurement of the initial Twiss parameters which in the SNS case was done by using the first four LW stations at the beginning of the superconducting linac. For years the consistency between all LW stations data could not be achieved. This problem was resolved only after significant improvements in accuracy of the phase scans of the SCL cavities, more precise analysis of all available scan data, better optics planning, and the initial longitudinal Twiss parameters measurements. The presented paper discusses in details these developed procedures.

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WEPM5Y01

H⁻ Beam Dynamics Study of a LEBT in XiPAF Project with the WARP PIC Code

simulation, ion, rfq, proton

449

R. Ruo, L. Du, T.B. Du, X. Guan, C.-X. Tang, X.W. Wang, Q.Z. Xing, H.Y. Zhang, Q.Z. Zhang
TUB, Beijing, People's Republic of China
Y. He, J. Li
NUCTECH, Beijing, People's Republic of China

The 7 MeV H⁻ linac injector of Xi‘an Proton Application Facility (XiPAF) is composed of an ECR ion source, a Low Energy Beam Transport line (LEBT), a Radio Frequency Quadrupole accelerator (RFQ) and a Drift Tube Linac (DTL). The 1.7 m-long LEBT is used for matching a 40 μs pulse width 6 mA peak current beam to the entrance of the RFQ accelerator. The peak current and pulse-width of the 50 keV H⁻ beam extracted from the ion source is 10 mA and 1 ms respectively. In the LEBT, an adjustable aperture is used for scraping the peak current of the beam to 6 mA, and an electric chopper is used for chopping the beam pulse width to 40 μs. These elements make the space charge compensation problem more complicated. A careful simulation of the space charge compensation problem of the H⁻ beam has been done by considering the beam particles interacting with the residual gas with the help of WARP PIC code. To achieve the requirements of the LEBT in XiPAF, the type and pressure of the residual gas is given according to the simulation results.

Slides WEPM5Y01 [5.926 MB]

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WEPM6Y01

Study on Space Charge Compensation of Low Energy High Intensity Ion Beam in Peking University

ion, simulation, experiment, ion-source

453

S.X. Peng, J.E. Chen, Z.Y. Guo, H.T. Ren, J.M. Wen, W.B. Wu, Y. Xu, A.L. Zhang, J.F. Zhang, T. Zhang
PKU, Beijing, People's Republic of China
J.E. Chen
Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China
H.T. Ren
FRIB, East Lansing, Michigan, USA
A.L. Zhang
University of Chinese Academy of Sciences, Beijing, People's Republic of China

To better understand the space charge compensation processes in low energy high intensity beam transportation, numerical study and experimental simulation on H⁺ beam and H⁻ beam were carried out at Peking University (PKU). The numerical simulation is done with a PIC-MCC model [1] whose computing framework was done with the 3D MATLAB PIC code bender [2], and the impacts among particles were done with Monte Carlo collision via null-collision method [3]. Issues, such as beam loss caused by collisions in H⁺, H⁻ beam and ion-electron instability related to decompensation and overcompensation in H⁻ beam, are carefully treated in this model. The experiments were performed on PKU ion source test bench. Compensation gases were injected directly into the beam transportation region to modify the space charge compensation degree. The results obtained during the experiment are agree well with the numerical simulation ones for both H⁺ beam [1] and H⁻ beam [4]. Details will be presented in this paper.

Slides WEPM6Y01 [5.625 MB]

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THPM1X01

Typology of Space Charge Resonances

resonance, emittance, lattice, focusing

486

I. Hofmann
GSI, Darmstadt, Germany

The existence of structural space charge resonant effects in otherwise linear periodic focusing systems is well-known, but referred to in a variety of languages and contexts. We show here that for short bunched beams a ‘‘classification'' in two major groups is possible, e.g. parametric resonances or instabilities on the one hand and single particle type space charge resonances on the other hand. The primary feature of distinction is that for the former the driving space charge force initially exists on the noise level (rms or higher order mismatch) only and gets amplified parametrically, hence an entirely coherent response; for the latter the driving space charge multipole is part of the initial density profile and the coherent response is weak. In the extreme limit of KV beams only parametric resonances (instabilities) exist, and in principle in all orders. For waterbag or Gaussian distributions we find half-integer parametric resonances only up to fourth order, but evidence for single particle resonances in all orders up to tenth have been identified.

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THPM4X01

Resonances and Envelope Instability in High Intensity Linear Accelerators

resonance, lattice, linac, emittance

491

D. Jeon, J.-H. Jang, H. Jin
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the NRF of Korea under Contract 2013M7A1A1075764.
Understanding of space charge effects has grown and recent studies have led to the findings of resonances of high intensity linear accelerators. Lately the sixth order resonance of high intensity linear accelerators was reported, along with the in-depth studies on the fourth order resonance and the envelope instability. Experiment studies on space charge resonances were reported. This paper reviews the resonances of high intensity linear accelerators such as the 4σ =360deg, and the 6σ =720deg resonances, along with the envelope instability.

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THPM5X01

Using an Electron Cooler for Space Charge Compensation in the GSI Synchrotron SIS18

electron, ion, experiment, focusing

496

W.D. Stem, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

Funding: Work is supported by BMBF contract FKZ:05P15RDRBA
For the future operation of the SIS18 as a booster synchrotron for the FAIR SIS100, space charge and beam lifetime are expected to be the main intensity limitations. Intensity is limited in part by the space-charge-induced incoherent tune shift in bunched beams. A co-propagating, low energy electron lens can compensate for this tune shift by applying opposing space-charge fields in the ion beam. In this paper, we study the effect of using the existing electron cooler at the SIS18 as a space charge compensation device. We anticipate beta beating may arise due to the singular localized focusing error, and explore the possibility of adding additional lenses to reduce this error. We also study the effect of electron lenses on the coherent (collective) and incoherent (single-particle) stopbands. Furthermore, we estimate the lifetime of partially stripped heavy-ions due to charge exchange process in the lens.

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THPM6X01

Space Charge Effects in FFAG

closed-orbit, lattice, betatron, emittance

499

M. Haj Tahar, F. Méot
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Understanding space charge effects in FFAG is crucial in order to assess their potential for high power applications. This paper shows that, to carry out parametric studies of these effects in FFAG, the average field index of the focusing and defocusing magnets are the natural parametrization. Using several classes of particle distribution functions, we investigate the effects of space charge forces on the non-linear beam dynamics of FFAG and provide stability diagrams for an FFAG-like lattice. The method developed in this study is mainly applicable to systems with slowly varying parameters, i.e slow acceleration.

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THPM9X01

Space Charge Effects and Mitigation in the CERN PS Booster, in View of the Upgrade

injection, emittance, booster, simulation

517

E. Benedetto, M. Cieslak-Kowalska, V. Forte, F. Schmidt
CERN, Geneva, Switzerland
M. Cieslak-Kowalska
EPFL, Lausanne, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France

The CERN PS Booster (PSB) is presently running with a space-charge tune spread larger than 0.5 at injection. Since the High Luminosity LHC (HL-LHC) will require beams with twice the intensity and brightness of today, the LHC Injector Upgrade (LIU) Project is putting in place an upgrade program for all the injector chain and, in particular, it relies on the important assumption that the PS Booster can successfully produce these beams after the implementation of the 160 MeV H⁻ injection from Linac4. This contribution describes the studies (measurements and simulations) that have been carried out to confirm that the PSB can indeed perform as needed in terms of beam brightness for the future HL-LHC runs. The importance of the mitigation measures already in place, such as the correction of the half-integer line, and the effects of non-linear resonances on the beam are also discussed.

Slides THPM9X01 [6.786 MB]

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THPM7Y01

A New RFQ Model and Symplectic Multi-Particle Tracking in the IMPACT Code Suite

rfq, simulation, proton, emittance

562

J. Qiang
LBNL, Berkeley, California, USA
L. Li, Z. Wang
PKU, Beijing, People's Republic of China

The IMPACT code suite is a self-consistent parallel three-dimensional beam dynamics simulation toolbox that combines the magnetic optics method and the parallel particle-in-cell method. It has been widely used to study high intensity/high brightness beams in many accelerators. In this paper, we will report on recent improvements to the code such as the capability to model RFQ in time domain and symplectic multi-particle tracking with a gridless spectral solver for space-charge simulation.

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FRAM2P01

Summary WG-A

resonance, electron, simulation, experiment

575

W. Fischer
BNL, Upton, Long Island, New York, USA
Y.H. Chin
KEK, Ibaraki, Japan
G. Franchetti
GSI, Darmstadt, Germany

Friday Summary

Slides FRAM2P01 [6.325 MB]

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