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| MOEPPB007 | Studies of eRHIC Coherent Instabilities | proton, simulation, impedance, betatron | 91 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.4cm, which is about a factor of 3 shorter than the current RHIC rms bunch length. Together with a factor of 2 increase in bunch intensity, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for various single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and octupole strength are specified to avoid these instabilities. |
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| MOEPPB012 | High-performance Beam Simulator for the LANSCE Linac | linac, simulation, controls, EPICS | 103 |
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Funding: U.S. Dept. of Energy, NNSA under contract DE-AC52-06NA25396. The LANSCE accelerator complex is a multi-beam facility that provides high-intensity H+ and H− particle beams for a variety of user programs. At the heart of the facility is a room temperature linac that is comprised of a 100-MeV drift tube linac and an 800-MeV coupled cavity linac. During beam operations, linac parameters are adjusted to maintain minimal beam spill, but without detailed knowledge of the beam distribution. A more desirable situation would be one where knowledge of the beam distribution along the linac is available to aid in the optimization of the linac operation and beam performance. We are presently developing a high performance simulator that will provide valuable information about the beam distribution in pseudo real-time during linac operations. The heart of the simulator is based upon the multiparticle beam dynamics code PARMILA, but implemented in C++ using NVIDIA’s CUDA technology for Graphics Processing unit (GPU) hardware. Linac operating set points will be provided by the EPICS control system so that changes are tracked and the simulation results updated automatically. Details regarding the approach, benefits and performance will be presented. |
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| MOPPC018 | Single/Few Bunch Space Charge Effects at 8 GeV in the Fermilab Main Injector | background, factory, simulation, proton | 163 |
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| For Project X, it is planned to inject a beam of 3 1011 particles per bunch into the Main Injector. Therefore, at 8 GeV, there will be increased space charge tune shifts and an increased incoherent tune spread. In preparation for these higher intensity bunches exploratory studies have commenced looking at the transmission of different intensity bunches at different tunes. An experiment is described with results for bunch intensities between 20 and 172 109 particles. To achieve the highest intensity bunches coalescing at 8 GeV is required, resulting in a longer bunch length. Comparisons show that similar transmission curves are obtained when the intensity and bunch length have increased by factors of 3.2 and 3.4 respectively, indicating the incoherent tune shifts are similar, as expected from theory. The results of these experiments will be used in conjugation with simulations to further study high intensity bunches in the Main Injector. | |||
| MOPPC079 | Modelling of the EMMA ns-FFAG Ring Using GPT | emittance, injection, quadrupole, electron | 319 |
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| EMMA (Electron Machine with Many Applications) is a prototype non-scaling Fixed-Field Alternating Gradient (ns-FFAG) accelerator whose construction at Daresbury Laboratory, UK, was completed in the autumn of 2010. The energy recovery linac ALICE will serve as an injector for EMMA, within an energy range of 10 to 20 MeV. The injection line consists of a symmetric 30 degree dogleg to extract the beam from ALICE, a matching section and a tomography section for transverse emittance measurements. This is followed by a transport section to the injection point of the EMMA ring. The ring is composed of 42 cells, each containing one focusing and one defocusing quadrupole. Acceleration over many turns of the EMMA machine has recently been confirmed. In some cases the bunch will traverse upwards of 100 turns, at which point the effects of space-charge may be significant. It is therefore necessary to model the electron beam transport in the ring using a code capable of both calculating the effect of and compensating for space-charge. Therefore the General Particle Tracer (GPT) code has been used. A range of injection beam parameters have been modeled for comparison with experimental results. | |||
| MOPPC080 | Modeling Space Charge in an FFAG with Zgoubi | lattice, emittance, acceleration, synchrotron | 322 |
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| The Zgoubi particle tracker uses a ray tracing algorithm that can accurately track particles with large offset from any reference momentum and trajectory, making it suitable for FFAGs. In high current FFAGs, for example an ADSR driver, space charge has a significant effect on the beam. A transverse space charge model was added to Zgoubi using the interface pyZgoubi. The magnets are sliced and a space charge kick is applied between each slice. Results are presented for an ADSR driver lattice. | |||
| MOPPC084 | G4beamline Code Development | electron, collider, radiation, synchrotron | 334 |
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Funding: Supported in part by DoE STTR grant DE-FG02-06ER86281. G4beamline is a single-particle-tracking simulation program based on Geant4, optimized specifically for beam lines. It is currently used by several hundred physicists and designers around the world, who apply it to a diverse set of interesting problems. As it includes particle decays and interactions, it is applicable to beams for which decays and interactions are important, such as modern muon facilities that involve ionization cooling. Its description language has been designed to be both versatile and user-friendly, and the program includes high-quality visualization and histogramming capabilities. This paper discusses recent code development and new features, and some interesting applications of the program. G4beamline is an open-source program freely available at http://g4beamline.muonsinc.com |
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| MOPPC085 | An Integrated Green Function Poisson Solver for Rectangular Waveguides | simulation, synchrotron, beam-beam-effects | 337 |
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Funding: DOE Office of Science, Office of High Energy Physics and Office of Advanced Scientific Computing Research A new method is presented for solving Poisson's equation inside a rectangular waveguide. The method uses Fast Fourier Transforms (FFTs) to perform mixed convolutions and correlations of the charge density with an integrated Green function. Due to its similarity to the widely used Hockney algorithm for solving Poisson's equation in free space, this capability can be easily implemented in many existing particle-in-cell beam dynamics codes. |
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| MOPPC089 | CUDA Kernel Design for GPU-based Beam Dynamics Simulations | simulation, acceleration, impedance, linac | 343 |
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Funding: Work supported by the US DOE Office of Science, Office of Basic Energy Sciences under grant number DE-SC0004585. Efficient implementation of general-purpose particle tracking on GPUs can result in significant performance benefits to large-scale particle tracking and tracking-based accelerator optimization simulations. We present our work on CUDA kernels for transfer maps of single-particle-dynamics and collective-effects beamline elements, to be incorporated into a GPU-accelerated version of the ANL's accelerator code ELEGANT. In particular, we discuss techniques for efficient utilization of the device shared, cache, and local memory in the design of single-particle and collective-effects kernels. We also discuss the use of data-parallel and hardware-assisted approaches (segmented scan and atomic updates) for resolving memory contention issues at the charge deposition stage of algorithms for modeling collective effects. We present and discuss performance results for the CUDA kernels developed and optimized as part of this project. |
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| MOPPC093 | Optimal Fast Multipole Method Data Structures | target, multipole, electron, simulation | 352 |
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| The Fast Multipole Method (FMM) has been identified as one of the ten most significant numerical algorithms discovered in the 20th century. The FMM guarantees finding fast solutions to many problems in science, such as calculating Coulomb potentials among large number of particles by reducing memory footprint and run time while attaining very high accuracy levels. One important practical issue that we have to solve in implementing a FMM algorithm is organizing large amounts of data, also called data structuring. The non-adaptive FMM is appropriate when the particles are uniformly distributed while the adaptive FMM is most efficient when the distribution is non-uniform. In practice, we typically encounter highly non-uniform 3D particle distributions. This paper summarizes our implementation of a 3D adaptive FMM algorithm data structure setup for non-uniform particle distributions. | |||
| MOPPC094 | Charge Density Estimations with Orthogonal Polynomials | electron | 355 |
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Funding: This work was supported by the Department of Energy under Contract No. DE-FG02-08ER41532 with Northern Illinois University. A beam’s charge density, treated as a smooth and continuous function can be approximated using orthogonal series, allowing a solution of Poisson’s equation to be found. Getting the most accurate solution to the electric potential requires the best approximated charge density. Several beam distributions are approximated using Jacobi polynomials generated by the recursion relation and the moment method. Varying both the particle number and order of the approximation gives a chance to not only compare the performance of the different polynomials, but allows to determine if a particular combination of order and particle number works better for a particular function. Although all three orthogonal polynomials used give similar results, the approximation coefficients should be allowed to converge and taken to high orders for best results. This is clearly seen on the single Gaussian approximation, where after five million particles, the difference between the distributions remains constant and the highest tested order gives best results. |
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| MOPPD028 | Observation of Longitudinal Space Charge Effects in the Injection Beam Line of NIRS-930 Cyclotron | bunching, cyclotron, injection, simulation | 427 |
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| Dependence of bunching efficiencies on the position of a beam buncher was measured for the AVF cyclotron at the National Institute of Radiological Sciences (NIRS) for 30 MeV proton beams with intensities up to 100 microamperes at injection. The measurement was carried out for two positions: 1.53 m and 2.33 m upstream from the inflector. For the buncher position of 2.33 m the bunching efficiency decreased, as the beam intensity increased, to about half of that at low intensities, while for 1.5 m it was constant up to 100 microamperes. The intensity distributions of extracted beam with respect to the buncher phase were also measured for the two buncher positions. The dependence of bunch width on the beam intensity is discussed by comparing the data with one-dimensional simulations on longitudinal space charge effects. | |||
| MOPPD036 | Gabor Lens Focusing for Medical Applications | ion, laser, proton, focusing | 442 |
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| The widespread introduction of Hadron therapy for cancer treatment is inhibited by the large costs for the accelerator and treatment facility and the subsequent maintenance costs which reflects into the cost per treatment. In the long term future (laser) plasma wakefield accelerated hadrons could offer compact treatment devices with significantly reduced treatment costs. In the moment the particle distributions produced by such accelerators do not fulfill the medical requirements by far. Never the less steady progress on the field might change the situation in the future. Beside the reliable production of a sufficient number of ions at the required energy the formation of a particle beam suitable for treatment from the burst of ions created in the acceleration process is one of the major challenges. While conventional optical systems will be operating at the technical limits which would be contradictory to the cost argument, space charge lenses of the Gabor type might be a cost effective alternative. In this paper a beam line consisting of such lenses will be presented together with particle transport simulations. | |||
| MOPPD037 | Investigation of Space Charge Compensation at FETS | ion, emittance, ion-source, rfq | 445 |
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| In order to contribute to the development of high power proton accelerators in the MW range, to prepare the way for an ISIS upgrade and to contribute to the UK design effort on neutrino factories, a front end test stand (FETS) is being constructed at the Rutherford Appleton Laboratory (RAL) in the UK. The aim of the FETS is to demonstrate the production of a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV with sufficient beam quality. The ion source and LEBT are operational with the RFQ under manufacture. In the LEBT a high degree of space charge compensation (~90%) and a rise time of space charge compensation around ~ 50 μs could be concluded indirectly from measurements . As a more detailed knowledge is of interest also for other projects like ESS the FETS LEBT was updated to perform a detailed experimental analysis of space charge compensation. In this paper the results of the experimental work will be presented together with discussion of the findings in respect to beam transport. | |||
| MOPPR029 | Upgrade of Ionization Profile Monitor (IPM) in the J-PARC 3-GeV RCS | electron, ion, vacuum, status | 840 |
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| Ionization Profile Monitors (IPM) were installed and operated in the J-PARC 3-GeV RCS for the observation of circulating beam profile. In IPM system, ions produced by the beam passing through beam chamber lead to Multi Channel Plate (MCP) by electric field, and the signals from the MCP are observed as the beam profile. The IPM system has an upgrade plan for the optimization of the electric fields. This will be reported the upgrade status of the IPM. | |||
| MOPPR059 | Modeling Space-charge and its Influence on the Measurement of Phase Space in ALICE by Tomographic Methods | quadrupole, injection, electron, diagnostics | 918 |
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Funding: STFC. ALICE is an experimental electron accelerator designed to operate over a range of energies up to 35 MeV, and with up to 80 pC bunch charge. A dedicated tomography diagnostic section allows measurement of the transverse phase space with different beam parameters. In the low-energy, high-charge regime, space charge effects must be considered: to quantify these effects, the tracking code GPT has been used to simulate beams in the tomography diagnostic section. The results can be compared with simplified models, and with experimental measurements. |
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| TUEPPB004 | A Longitudinal Beam Dynamics Code for Proton Synchrotron | cavity, simulation, synchrotron, bunching | 1119 |
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| The accelerator of China Spallation Neutron Source (CSNS) consists of an 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS). Longitudinal beam dynamics study is one of the most important issues for RCS beam dynamics design. However, the existing codes cannot meet the requirement of longitudinal beam dynamics for CSNS/RCS. A new code has been developed for longitudinal beam dynamics design and simulation. The code can perform the voltage and phase curves design for non-sinusoidal magnetic field of dipole in an RCS cycle, with the fundamental RF mode and dual harmonic mode. The code can also be used for the beam simulation with longitudinal space charge effect, including the effects of higher order mode of RF cavities. By using the code, the longitudinal beam dynamics of CSNS/RCS was designed and optimized, and the simulation study with dual harmonics higher order modes of RF cavity was done, and the simulation results are presented. | |||
| TUEPPB007 | A Self Consistent Multiprocessor Space Charge Algorithm that is Almost Embarrassingly Parallel | simulation, factory, collective-effects, brightness | 1128 |
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Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We present a space charge code that is self consistent, massively parallelizeable, and requires very little communication between the computer nodes; making the calculation almost embarrassingly parallel. This method is implemented in the code COSY Infinity where the differential algebras used in this code are important to the algorithm's proper functioning. The method works by calculating the self consistent charge distribution using the statistical moments of the test particles, and converting them into polynomial series coefficients. These coefficients are combined with differential algebraic integrals to form the potential, and electric fields. The result is a transfer map which contains the effects of space charge. This method allows for massive parallelization since its statistics based solver doesn’t require any binning of the particles, and only requires a vector containing the partial sums of the statistical moments for the different nodes to be passed. All other calculations are done independently. The resulting maps can be used to analyze the system using normal form analysis, as well as advance particles in numbers and at speeds that were previously impossible. |
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| TUPPC007 | Electron Cloud Dynamics in a Gabor Space Charge Lens | electron, plasma, ion, focusing | 1164 |
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| Inside Gabor space charge lenses, external fields confine electrons forming a homogeneously distributed electron cloud. Its linear electric space charge field enables the focusing of high intensity heavy ion beams without aberrations. The focusing performance depends on the properties of the non-neutral plasma. In a small-scale table top experiment, different types of space charge lenses are used to characterize the collective behavior of the confined electron cloud using new non-interceptive diagnostic methods. The plasma parameters, e.g. electron temperature and density, are important to an improved understanding of loss and production mechanisms as well as the electron cloud dynamics. In this context, the evolution of instabilities caused by the enclosing fields has been investigated in detail. Experimental results will be presented and compared to numerical simulations. | |||
| TUPPC065 | High Intensity Beam Analysis for the Superconducting Radio-frequency Linac (SRF-Linac) of the IFMIF-EVEDA Accelerators | emittance, resonance, linac, SRF | 1323 |
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| In this proceeding we analyze space charge effects on the beam dynamics of IFMIF accelerators. The objective is to be able to characterize and understand the crucial issues like halo formation, emittance growth and sudden particle losses in the SRF-Linac. We use the Hofmann stability charts to identify modes of collective space charge density oscillations that are responsible for the transfer and growth of the emittance. With identification of modes we are able to treat the parametric resonance between the modes and the nonlinear motion of an individual ion the amplitude of which is greater than the core radius. The resulting phase space consists of an inner separatrix containing the core and an outer separatrix that becomes the locus near which the halo particles enter and cluster. | |||
| TUPPC094 | Experimental Observations of Large-amplitude Solitary Waves in Electron Beams | electron, laser, longitudinal-dynamics, gun | 1377 |
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Funding: Work funded by the US Dept. of Energy Offices of Fusion Energy Sciences and High Energy Physics and Fusion Energy Sciences, and by the Dept. of Defense Office of Naval Research. The longitudinal dynamics of space charge dominated beams plays an important role in particle accelerators and other applications such as heavy ion fusion and free electron lasers (FELs). All beams are space-charge dominated near the source. Furthermore, the longitudinal profile is not necessarily an ideal mathematical function. By means of experiments on the University of Maryland Electron Ring (UMER), we studied how a perturbation to the line charge density could affect the beam propagation. By varying the initial amplitude of the perturbation, we access nonlinear space charge physics. When starting with large-amplitude perturbations, we have observed, for the first time in charged particle beams, solitary waves for which the nonlinear steepening exactly balances the wave dispersion, leading to persistent waves that preserves their shape over a long distance. This paper presents the results of the soliton experiments, including systematic studies of the dependence of the soliton propagation on beam current, perturbation level and width. The data is compared with theory and simulation. |
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| TUPPC102 | Simulation Study of Beam-beam Effects in Ion Beams with Large Space Charge Tuneshift | simulation, lattice, synchrotron, collider | 1398 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. During low-energy operations with gold-gold collisions at 3.85 GeV beam energy, significant beam lifetime reductions have been observed due to the beam-beam interaction in the presence of large space charge tuneshifts. These beam-beam tuneshift parameters were about an order of magnitude smaller than during regular high energy operations. To get a better understanding of this effect, simulations have been performed. Recent results are presented. |
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| TUPPD046 | Characterization of Li+ Alumino-Silicate Ion Source for Target Heating Experiments | ion, extraction, ion-source, brightness | 1506 |
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Funding: *This work was performed under the auspices of the U.S Department of Energy by LLNL under contract DE AC52 07NA27344, and by LBNL under contract. DE-AC02-05CH11231. The Heavy Ion Fusion Sciences (HIFS) program at Lawrence Berkeley National Laboratory will carry out warm dense matter experiments using Li+ ion beam with energy 1.2–3 MeV to achieve uniform heating up to 0.1–1 eV. Experiments will be done using the Neutralized Drift Compression Experiment-II (NDCX-II) facility. The NDCX-II accelerator has been designed to use a large diameter (10.9 cm) Li+ doped alumino-silicate source to produce short pulses of ≈93 mA beam current. Fabrication of a lithium source is complex, it is necessary to apply a higher temperature (>1200-degC) for thermionic emission, and the beam current density of this source is ~1mA/cm2 in the space-charge limited regime. Li+ emission is lower than the other alkaline ions sources (K+, Cs+). The lifetime of this source is roughly 50 hours, when pulsed. Characterization of an operational lithium alumino-silicate ion source, including beam emittance, is presented. |
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| TUPPP012 | Optimization of the Beam Optical Parameters of the Linac-based Terahertz Source FLUTE | laser, gun, linac, simulation | 1629 |
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Funding: Karlsruher Institut für Technologie. FLUTE is a compact accelerator (consisting of a 7 MeV laser gun, a 50 MeV linac, and bunch compressors) under construction at KIT in Karlsruhe for producing coherent THz radiation. The programs ASTRA and CSRtrack were used to optimize the beam parameters. The aim was to minimize the bunch length used in various THz experiments, with bunch charges between 100 pC and 3 nC. It was calculated that the bunch length after compression depends both on the bunch current and the transverse beam size. The transverse beam size depends on the laser spot size at the cathode of the 7 MeV laser gun. Further simulations showed that a larger beam size reduces the efficiency of the compressor. This problem is cured by focusing elements with a focusing strength depending on the space charge after the gun and integrated into the various compressors layouts under study (four magnets, two magnets and quadrupoles, etc.). The results of these calculations are presented in this paper. |
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| TUPPP053 | Investigations on the Optimum Accelerator Parameters for the Ultra-Short Bunch Operation of the Free-Electron Laser in Hamburg (FLASH) | laser, emittance, electron, simulation | 1718 |
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Funding: The project is supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301. In order to produce the shortest possible radiation pulses using Free Electron Lasers like FLASH, various possibilities have been proposed during the last decade. Probably the most robust method is the generation of electron bunches that in the most extreme case are as short as a single longitudinal optical mode of the SASE (Self-Amplified Spontaneous Emission) radiation. For FLASH this means that the bunch length has to be a few fs only. As a consequence, very low bunch charges (in the order of 20 pC) have to be used. To achieve these extremely short bunch lengths, a new photo-injector laser has been installed, which allows for the generation of shorter electron bunches right at the cathode. Simulations of the electron bunches and their six-dimensional phase-space distribution have been performed to investigate the optimum accelerator parameters during injection and to determine how to realize them. First results are discussed in this contribution. |
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| TUPPP090 | Studies of Controlled Laser-induced Microbunching Instability at Source Development Laboratory | laser, electron, linac, radiation | 1798 |
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| We present the studies of controlled microbunching intentionally induced on the beam by the photocathode laser with modulated longitudinal profile. Varying the depth and frequency of longitudinal modulation of the laser pulse allowed us to observe the development of microbunching instability at BNL Source Development Laboratory (SDL) in the controlled environment. That allowed us to benchmark the model of the microbunching gain for the first time. In addition to that, we demonstrated for the first time a constructive work of a so-called longitudinal space charge amplifier, which in case under consideration can be utilized for enhancement of linac-based sources of THz radiation. | |||
| WEPPD052 | Compression and Synchronization of MeV Scale Subpicosecond Electron Beams in a THz IFEL Interaction | undulator, electron, laser, simulation | 2636 |
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Recent development of MW peak power THz sources from efficient optical rectification of broadband IR pulses by pulse front tilting has made available laser locked single cycle THz pulses suitable for compression and laser-synchronization of photoinjector generated subpicosecond electron beams. Three dimensional simulations have shown that a waveguided 8 pulse THz train can be used to interact with a sub picoseconds electron beam in an undulator to achieve compression and laser synchronization. We present a THz pulse train source currently under development at UCLA PBPL as well as detailed 3 dimensional simulations including the effect of the interaction on transverse beam quality.
DOE-BES No. DE-FG02-92ER40693 and DOE-BES No. DE-FG02-07ER46272 |
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| WEPPR001 | Experimental Observation of Space Charge Effects in Transverse Bunch Oscillations in the SIS18 Synchrotron | synchrotron, simulation, ion, damping | 2931 |
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| Coherent signals from transverse bunch oscillations in the heavy-ion synchrotron SIS18 are used for direct measurements of the space charge effect. The bunch oscillations are excited by a transverse kick and the resulting decoherence is observed. The transverse coherent motion in the SIS18 experiments is strongly affected by space charge. The bunches are long, thus the nonlinear motion in the rf bucket plays an important role and must be taken into account. The signals from the measurements are analyzed and explained using analytical and numerical models. | |||
| WEPPR002 | Intensity Thresholds for Transverse Coherent Instabilities During Proton and Heavy-Ion Operation in SIS100 | impedance, proton, synchrotron, simulation | 2934 |
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| The SIS100 synchrotron is the central accelerator of the projected FAIR complex. It should deliver high intensity proton and heavy-ion beams to the different FAIR experiments. Coherent transverse instabilities are a potential intensity-limiting factor in SIS100. In this contribution we give a summary of the different transverse coherent effects in intense bunched beams that can be expected in the SIS100. Some of the main concerns are unstable head-tail modes, the transverse mode coupling instability, and the beam break-up instability. Space charge is an important effect that leads to Landau damping of the head-tail eigenmodes and modifies the transverse mode coupling. The growth times and thresholds for instabilities will be calculated on the basis of the present SIS100 impedance model whose main components are the resistive wall, the kickers, and the broad-band contribution. The corresponding experience from the CERN injector complex will be used for comparisons. | |||
| WEPPR003 | Longitudinal Dynamics of Intense Heavy-Ion Bunches in SIS-100 | impedance, ion, heavy-ion, beam-loading | 2937 |
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| In the SIS-100 highest heavy-ion intensities have to be accelerated to deliver beam to the FAIR experiments. In the projected SIS-100 synchrotron the heavy ion bunches will be strongly affected by the longitudinal space charge force. Due to the limited RF bucket area all mechanisms which might cause longitudinal phase space dilution must be understood and controlled. Space charge effects, like the reduction in the RF voltage and the loss of Landau damping, have already been part of elaborate studies. It has been shown that cavity beam loading can deform the flattened bunch shape in the dual rf bucket. Among the different counter measures an inductive insert has been proposed in order to partially compensate the longitudinal space charge impedance. Optimized settings for the difference between the two rf phases in a dual rf bucket might be an option to reduce the effect of beam loading. In this contribution we will analyse the matched bunch distribution for SIS-100 parameters in single and dual rf buckets. Analytical and numerical studies of the interplay of longitudinal space charge, cavity beam loading and an inductive insert will be presented. | |||
| WEPPR011 | Numerical Simulation Study of the Montague Resonance at the CERN Proton Synchrotron | emittance, simulation, resonance, synchrotron | 2958 |
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Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP) under Contract No. DE-AC02-05CH11231. The Montague resonance provides a coupling between the vertical and the horizontal dynamics of beams and can cause particle losses due to unequal aperture sizes of the accelerator. In this paper, we present a new numerical simulation study of a previous Montague resonance crossing experiment at the CERN PS including detailed three-dimensional space-charge effects and machine nonlinearity. The simulation reproduces the experimental data and suggests that the longitudinal synchrotron motion played an important role in enhancing transverse resonance coupling. |
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| WEPPR012 | Simulating High-Intensity Proton Beams in Nonlinear Lattices with PyORBIT | lattice, resonance, simulation, proton | 2961 |
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High-intensity proton linacs and storage rings are essential for a) state-of-the-art neutron source user facilities, b) extending the high-energy physics intensity frontier, c) as a driver to generate pions for a future neutrino factory or muon collider, and d) for transmutation of radioactive waste and associated energy production. For example, Project X at Fermilab will deliver MW proton beams at energies ranging from 3 to 120 GeV. Nonlinear magnetic lattices with large tune spreads and with integrable*, nearly integrable** and chaotic* dynamics have been proposed to maximize dynamic aperture and minimize particle loss. We present PyORBIT*** simulations of proton dynamics in such lattices, including the effects of transverse space charge.
* V. Danilov and S. Nagaitsev, PR ST-AB 13 084002 (2010) ** K. Sonnad and J. Cary, Phys. Rev. E 69 056501 (2004) *** A. Shishlo, J. Holmes and T. Gorlov, From Proceedings of IPAC '09 351-354 |
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| WEPPR014 | Recovering Measured Dynamics from a DC Circulating Space-Charge-Dominated Storage Ring | electron, background, diagnostics, storage-ring | 2967 |
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Funding: This work is supported by the US Dept. of Energy Offices of High Energy Physics and Fusion Energy Sciences, and by the US Dept. of Defense Office of Naval Research and Joint Technology Office. Space-charge is increasingly significant at high beam intensities such as in FEL injectors and heavy ion inertial fusion drivers, where it dominates the beam dynamics. The University of Maryland Electron Ring (UMER) is a high intensity circular machine that is dedicated to the study of long path length space-charge-dominated beam physics on a small scale. Over multiple turns, longitudinal space charge effects cause the tail and head of an electron bunch to expand and interpenetrate, eventually resulting in a “DC beam”. This leads to complications when trying to measure the beam with UMER’s AC coupled diagnostics. Three techniques are developed to recover the information within the beam. Two “knockout” techniques implement invasive pulsed electric kicks to the beam in combination with either a fluorescent imaging screen or a current monitor. A third technique based on integration of the wall-current signal provides a non-invasive method to study the DC beam dynamics. Experimental results from all three methods are compared. The DC beam profile can then be studied over long trajectories and the existence of any loss mechanisms can be determined. |
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| WEPPR016 | Potential for Luminosity Improvement for Low-energy RHIC Operation | luminosity, electron, ion, emittance | 2973 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. At the Brookhaven National Laboratory, a physics program, motivated by the search of the QCD phase transition critical point, requires operation of the Relativistic Heavy Ion Collider (RHIC) with heavy ions at very low beam energies corresponding to 2.5-20 GeV/n. Several physics runs were already successfully performed at these low energies. However, the luminosity is very low at lowest energies of interest (< 10 GeV/n) limited by the intra-beam scattering and space-charge, as well as by machine nonlinearities. At these low energies, electron cooling is very effective in counteracting luminosity degradation due to the IBS, while it is less effective against other limitations. Overall potential luminosity improvement for low-energy RHIC operation from cooling is summarized for various energies, taking into account all these limitations as well as beam lifetime measured during the low-energy RHIC runs. We also explore a possibility of further luminosity improvement under the space-charge limitation. |
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| WEPPR031 | Injector Beam Dynamics for a High-repetition Rate 4th-generation Light Source | emittance, electron, gun, linac | 3000 |
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Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231. We report on the beam dynamics studies and optimization methods for a high-repetition (1 MHz) photoinjector based on a VHF normal conducting electron source. The simultaneous goals of beam compression and preservation of 6-dimensional beam brightness have to be achieved in the injector, in order to accommodate a linac driven FEL light source. For this, a parallel, multiobjective optimization algorithm is used. We discuss the relative merits of different injector design points, as well as the constraints imposed on the beam dynamics by technical considerations such as the high repetition rate. |
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| WEPPR039 | Nonlinear Lattice for Space-Charge Dominated Beam Transport with Suppressed Emittance Growth | quadrupole, focusing, emittance, lattice | 3021 |
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We present a feasible design for the implementation of a beam emittance growth suppressing lattice for space-charge dominated beams. Our analysis is based on original derivations developed in *. We present a FODO focusing channel with quadrupole and duodecapole components which on average create the field required to match the high-brightness beam with the structure. Matched beam exhibits smaller emittance growth than that in regular quadrupole focusing channel. Numerical results demonstrate the lattice’s performance in preventing halo formation of a nonuniform space charge dominated beam.
* Y. Batygin, Phys. Rev. E, 57, 5, p. 6020 (1998). |
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| WEPPR041 | Design of a Compact Linear Accelerator for the Ultrafast Electron Diffraction Facility | electron, gun, linac, emittance | 3027 |
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| Ultrafast Electron Diffraction (UED) is a powerful tool to find 3-dimensional structures and dynamical transitions of chemical or biological samples with a femtosecond-range temporal resolution and an angstrom-range spatial resolution. Due to the columbic field of electrons, UED can provide a higher cross section and a higher time resolution than those of the ultrafast photon diffraction with X-ray Free Electron Lasers (XFELs). In this paper, we describe the design concepts and ASTRA simulation results of a compact linac for an UED facility. | |||
| WEPPR054 | Calculation of Coherent Wiggler Radiation using Eigenfunction Expansion Method | wiggler, impedance, radiation, damping | 3048 |
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An analytic method originated by Y. H. Chin* was extended to calculate the electromagnetic fields and the longitudinal impedance due to coherent wiggler radiation (CWR) in a rectangular chamber. The method used dyadic Green functions based on eigenfunction expansion method in electromagnetic theory and was rigorous for the case of straight chamber. We re-derived the theory and did find the full expressions for the longitudinal impedance of a wiggler with finite length. With shielding of chamber, the CWR impedance indicated resonant properties which were not seen in the theory for CWR in free space.
* Y.H. Chin, LBL-29981, 1990. |
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| WEPPR059 | The Simulation of Ion Cloud Build-up in Electron Storage Ring | ion, electron, simulation, storage-ring | 3060 |
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| In electron storage rings, positive ions are created by the ionization of the residual gas. Three main collision types including elastic collision, excitation collision and ionization collision are considered in this paper. In order to calculate the probability of the gas ionization using DSMC method, the total cross section, total inelastic cross section, elastic cross section, excitation cross section and ionization cross section are deduced separately. Once ions are created，PIC is adopted to trace the ion，s motion under the combined action due to externally applied field and self-field. The purpose of all study is to present how ion cloud gets to equilibrium little by little. | |||
| WEPPR085 | Observation of Instabilities of Coherent Transverse Ocillations in the Fermilab Booster | coupling, booster, damping, injection | 3129 |
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Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. The Fermilab Booster - built more than 40 years ago - operates well above the design proton beam intensity of 4.e12 ppp. Still, the Fermilab neutrino experiments call for even higher intensity of 5.5·1012 ppp. A multitude of intensity related effects must be overcome in order to meet this goal including suppression of coherent dipole instabilities of transverse oscillations which manifest themselves as a sudden drop in the beam current. In this report we present the results of observation of these instabilities at different tune, coupling and chromaticity settings and discuss possible cures. |
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| WEPPR097 | Comparing New Models of Transverse Instability with Simulations | coupling, simulation, synchrotron, wakefield | 3165 |
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Recently, Balbekov* has produced an ordinary integro-differential equation that approximates the Vlasov equation for beams with wakefields and large space charge tune shift. The present work compares this model with simulations. In particular, the claim that certain types of transverse wakes cannot lead to mode coupling instabilities, which contradicts earlier work**, is explored
* V. Balbekov, PRSTAB, 14, 094401 (2011). ** M. Blaskiewicz, PRSTAB 1, 044201 (1998). |
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| THEPPB003 | A 1 GeV CW FFAG High Intensity Proton Driver | emittance, simulation, cyclotron, focusing | 3234 |
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| The drive for high beam power, high duty cycle, and reliable beams at reasonable cost has focused world attention on fixed-field accelerators, notably Fixed-Field Alternating Gradient accelerators (FFAGs). High-intensity GeV proton drivers are of particular interest, as these encounter duty cycle and space-charge limits in the synchrotron and machine size concerns in the weaker-focusing cyclotron. Recently, the concept of isochronous orbits has been explored and developed for non-scaling FFAGs using powerful new methodologies in FFAG accelerator design. These new breeds of FFAGs have been identified by international collaborations for serious study thanks to their potential applications including Accelerator Driven Subcritical Reactors (ADS) and Accelerator Transmutation of Waste. The extreme reliability requirements for ADS mandate CW operation capability and the FFAG’s strong focusing, particularly in the vertical, will serve to mitigate the effect of space charge (as compared with the weak-focusing cyclotron). This paper reports on these new advances in FFAG accelerator technology and presents a stable, 0.25-1GeV isochronous FFAG for an accelerator driven subcritical reactor. | |||
| THPPP005 | Space Charge Effect in the Presence of x-y Coupling in J-PARC MR | coupling, lattice, emittance, simulation | 3731 |
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| It is crucial issue to suppress beam loss due to space charge force in J-PARC MR. We focus x-y coupling as a source of the beam loss. x-y coupling is measured by turn-by-turn beam position monitors in J-PARC MR. A space charge simulation under the measured x-y coupling evaluates the beam loss. Tolerance of x-y coupling and how to improve the beam loss are discussed. | |||
| THPPP014 | Design Parameters of a High-Power Proton Synchrotron for Neutrino Beams at Cern | proton, linac, synchrotron, injection | 3755 |
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| Design studies have been initiated at CERN for exploring the prospects of future high-power proton beams for producing neutrinos within the LAGUNA-LBNO project. These studies include a possible increase of the SPS beam power from 500kW to 700kW for a new conventional neutrino beam line based on the CNGS technology, and at a second stage a 2~MW High-Power Proton Synchrotron (HP-PS) using the Low Power Superconducting Proton Linac (LP-SPL) as injector. A low energy 5GeV-4MW neutrino super-beam alternative based on a high-power version of SPL is also considered. This paper concentrates on the HP-PS by exploring the parameter space and constraints regarding beam characteristics, machine hardware and layout, for reaching the 2~MW average beam power. | |||
| THPPP022 | Coalescing at 8 GeV in the Fermilab Main Injector | simulation, LLRF, emittance, synchrotron | 3779 |
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| For Project X, it is planned to inject a beam of 3 1011 particles per bunch into the Main Injector. To prepare for this by studying the effects of higher intensity bunches in the Main Injector it is necessary to perform coalescing at 8 GeV. The results of a series of experiments and simulations of 8 GeV coalescing are presented. To increase the coalescing efficiency adiabatic reduction of the 53 MHz RF is required, resulting in ~70% coalescing efficiency of 5 initial bunches. Data using wall current monitors has been taken to compare previous work and new simulations for 53 MHz RF reduction, bunch rotations and coalescing, good agreement between experiment and simulation was found. Possible schemes to increase the coalescing efficiency and generate even higher intensity bunches are discussed. These require improving the timing resolution of the low level RF and/or tuning the adiabatic voltage reduction of the 53 MHz. | |||
| THPPP046 | ESS End-to-End Simulations: a Comparison Between IMPACT and MADX | linac, simulation, cavity, DTL | 3841 |
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| The European Spallation Source will be a 5 MW superconducting proton linac for the production of spallation neutrons. It is composed of an ion source, a radio frequency quadrupole, a drift tube linac and a superconducting linac as well as the low, medium and high, energy beam transport sections. At present these components of the linac are in the design phase: the optimization of the accelerator parameters requires an intensive campaign of simulations to test the model of the machine under possible operational conditions. In this paper the results of simulations performed with the IMPACT and MADX-PTC codes are presented and a comparison is made between them and independent simulations using TraceWin. The dynamics of the beam envelope and single and multi-particle tracking are reported. | |||