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simulation

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MOCP04 LHC Upgrade Options and CARE-HHH Activities luminosity, electron, dipole, quadrupole 49
 
  • F. Zimmermann
    CERN, Geneva
  The European Accelerator Network on High Energy High Intensity Hadron Beams (CARE HHH) is developing scenarios for luminosity and energy upgrades of the Large Hadron Collider (LHC). The LHC upgrade options under consideration differ in terms of beam parameters, electron-cloud effects, beam-beam compensation, use of crab cavities, and interaction-region layout. Complementary investigations concern injector upgrades, novel magnet technologies, advanced collimation schemes, and ultimate intensity limitations. Flanking these upgrade studies, an accelerator-physics code web repository has been set up, and an extensive simulation-code benchmarking campaign is being prepared.  
 
TUAX03 Beam loss, emittance growth and halo formation due to the pinched electron cloud electron, emittance, synchrotron, resonance 84
 
  • E. Benedetto, F. Zimmermann
    CERN, Geneva
  • G. Franchetti
    GSI, Darmstadt
  • K. Ohmi
    KEK, Ibaraki
  Electron cloud can cause beam losses and emittance growth in proton or positron storage rings. If the electron density exceeds a certain threshold value, a strong head-tail instability manifests itself, characterized by a rapid beam-size blow-up with a rise time comparable to the synchrotron period. However, even for densities below the coherent-instability threshold, the electron-cloud can give rise to a significant emittance growth. We identified the mechanism for this incoherent growth as one caused by the combined effect of the beam particles synchrotron motion and the longitudinal variation of the tune shift, which is proportional to the pinched electron-cloud distribution along the bunch. This can give rise to the periodic crossing of a resonance, in analogy to halo formation in space-charge dominated beams, or eventually, if the tune shift is sufficiently large, to the crossing of bunch regions where the single-particle motion is linearly unstable.  
 
TUAX05 Studies of e-cloud build up for the FNAL main injector and for the LHC electron, dipole, cryogenics, injection 102
 
  • M. A. Furman
    LBNL, Berkeley, California
  We present a summary of recent simulation studies of the electron-cloud (EC) build-up for the FNAL Main Injector and for the LHC. In the first case we pay particular attention to the dependence on bunch intensity (Nb) at injection energy, and we focus on the dipole magnets and field-free regions. The saturated value of the average EC density shows a clear threshold in Nb beyond which the beam will be approximately neutralized on average. For the case of the LHC we limit our discussion to arc dipoles at collision energy, and bunch spacings tb=25 ns or tb=75 ns. The main variables exercised in this study are Nb and the peak value of the secondary emission yield (dmax). For tb=25 ns we conclude that the EC power deposition is comfortably below the available cooling capacity of the cryogenic system if dmax is below ~1.2 at nominal Nb. For tb=75 ns, the EC power deposition is insignificant. As a byproduct of this exercise, we reach a detailed understanding of the significant role played by the backscattered secondary electrons.  
 
TUAY05 Application of the extreme value theory to estimate beam loss in an ion linac, using large scale Monte Carlo simulations linac, beam-losses, quadrupole, beam-transport 107
 
  • R. Duperrier, D. Uriot
    CEA, Gif-sur-Yvette
  The influence of random perturbations of high intensity accelerator elements on the beam losses is considered. This paper presents the error sensitivity study which has been performed for the SPIRAL2 linac in order to define the tolerances for the construction. The proposed driver aims to accelerate a 5 mA deuteron beam up to 20 A. MeV and a 1 mA ion beam for q/A = 1/3 up to 14.5 A. MeV. It consists in an injector (two ECRs sources + LEBTs with the possibility to inject from several sources + Radio Frequency Quadrupole) followed by a superconducting section based on an array of independently phased cavities where the transverse focalization is performed with warm quadrupoles. The correction scheme and the expected losses are described. The Extreme Value Theory is used to estimate the expected beam losses. The described method couples large scale computations to obtain probability distribution functions. The bootstrap technique is used to provide confidence intervals associated to the beam loss predictions. With such a method, it is possible to measure the risk to loose a few watts in this high power linac (up to 200 kW).  
 
TUBX02 Collective Transverse Instabilities in the GSI Synchrotrons damping, space-charge, octupole, impedance 131
 
  • V. Kornilov, O. Boine-Frankenheim, I. Hofmann
    GSI, Darmstadt
  One of the primary challenges for the design of the FAIR synchrotrons at GSI Darmstadt is the high current operation close to the stability limits, with small tolerable beam losses. Collective instabilities are a potential limiting factor for the performance of the rings. We discuss results of experimental and numerical investigations of transverse collective beam behavior in the SIS 18 synchrotron. Also damping mechanisms in the presence of space charge, including the linear Landau damping and decoherence due to nonlinearities are discussed. These are the essential factors to define impedances budgets for the GSI synchrotrons. As a computational tool accounting the beam nonlinear dynamics with impedances and self-consistent space charge, the particle tracking code PATRIC is used.  
 
TUBY03 Error study of LINAC 4 linac, emittance, quadrupole, proton 137
 
  • M. A. Baylac, J.-M. De Conto, E. Froidefond
    LPSC, Grenoble
  • E. Zh. Sargsyan
    CERN, Geneva
  LINAC 4 is a normal conducting H- linac which aims to intensify the proton flux available for the CERN accelerator complex. This injector is designed to accelerate a 65 mA beam up to 180 MeV. The linac consists of 4 different types of accelerating structures: the 352 MHz IPHI-RFQ, a 352 MHz 3-tank Drift Tube Linac, a 352 MHz Coupled Cavity Drift Tube Linac, and a 704.4 MHz Side Coupled Linac to boost the beam up to the final energy. As LINAC 4 is also designed as a pre-injector for a high power superconducting linac (3.5 GeV, 4 MW) the requirements on acceptable beam emittance growth, halo formation and particle loss are extremely tight. In order to determine the tolerances on the linac components, we examined the sensitivity of the structure to errors on the accelerating field and on the focusing quadrupoles. Simulations were performed between 3 and 180 MeV with the transport code TRACEWIN to evaluate the emittance growth, energy and phase jitter, halo formation of the transported beam and the amount of lost particles. We will present results on individual sensitivities to a single error, as well as the global impact of simultaneous errors on the beam quality. We will mention a f  
 
TUBY05 A HIGH ENERGY GAIN DEUTERON LINAC linac, rfq, emittance, lattice 156
 
  • J. Rodnizki, D. Berkovits, K. Lavie, A. Shor, Y. Yanai
    Soreq NRC, Yavne
  The beam dynamic simulation of the SARAF 40 MeV, 4 mA deuteron beam superconducting linac is extended in this work to 90 MeV for the EURISOL driver. It is designed for a high energy gain gradient with a moderate emittance growth, based on an end-to-end 3D simulation using a detailed 40 k macro particles distribution at the RFQ exit. The linac consists of 84 superconducting HWRs and one superconducting solenoid per two HWRs. The result average energy gain is 2.0 MeV/m. At the linac first cryomodule, where the  mismatch is high, the emittance growth is controlled by considering the bunch acceleration phase at each of the HWR coupled acceleration gaps.  
 
WEAX03 Space charge neutralization and its dynamic effects space-charge, electron, linac, proton 187
 
  • R. Duperrier, N. Pichoff, D. Uriot
    CEA, Gif-sur-Yvette
  • A. BenIsmail
    LLR, Palaiseau
  High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully controlled. This nonlinear force can generate a large and irreversible emittance growth of the beam. To reduce the space charge (SC), neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the beam dynamics study. This contribution aims to modelize the beam behavior in such a regime and to give order of magnitude to the linac designer for the neutralization rise time and the induced emittance growth.  
 
WEAX04 High Intensity Cyclotron Simulations: Towards Quantitative Predictions cyclotron, injection, space-charge, proton 202
 
  • A. Adelmann, S. R.A. Adam, M. Humbel, P. A. Schmelzbach
    PSI, Villigen
  PSI operates the most powerful cyclotron worldwide to the benefit of a multi-user, cross-disciplinary research facility. The accelerator complex consists of a Cockcroft-Walton pre-injector, a 72-MeV separated sector injector cyclotron and a 590-MeV separated sector Ring Cyclotron. A beam current of 1.9 mA is routinely extracted from the Ring Cyclotron overall absolute losses are below 1·10-3. The facility has a considerable potential for further improvements, an ongoing upgrade project aims at a beam current of 3 mA. The purpose of our multi-scale three-dimensional parallel code and methods development is to make the step from qualitative to quantitative predictions. Their simulation requires the accurate three-dimensional modeling of large and complicated accelerator structures including space charge, beam lines, collimation, and in the future secondary effects. We will show methods, both numerically and computational, that we use presently and give an overview on future directions. Measurements from the cyclotrons and beamlines will be compared with simulations carried out in the frame of the high intensity upgrade program.  
 
WEAX06 Measurements and Synergia simulations of emittance dilution at the Fermilab Booster. resonance, injection, space-charge, booster 236
 
  • P. Spentzouris
    Fermilab, Batavia, Illinois
  We present a study of the beam evolution in the Fermilab Booster operating both under nominal conditions and in the vicinity of the sum resonance for different beam currents. We simultaneously recorded the horizontal and vertical beam profiles using the Ion Profile Monitor and beam current. Our analysis extracted 2-D emittances and beam shape information from the IPM data. We compare the results with Synergia simulations including 3-D space charge and higher-order optics to analyze and interpret the experimental results.  
 
WEAY04 Analysis of the magnetized friction force electron, ion, plasma, interaction-region 210
 
  • A. V. Fedotov
    BNL, Upton, Long Island, New York
  • D. L. Bruhwiler
    Tech-X, Boulder, Colorado
  • A. O. Sidorin
    JINR, Dubna, Moscow Region
  A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, we present our insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.  
 
WEAZ06 Transfer line damage during high intensity proton beam extraction from the SPS in 2004 extraction, power-supply, vacuum, septum 228
 
  • B. Goddard, V. Kain, V. Mertens, J. A. Uythoven, J. Wenninger
    CERN, Geneva
  During extraction of a high intensity beam from the SPS in 2004 an incident occurred in which the vacuum chamber of a transfer line quadrupole magnet was badly damaged. The beam was a 450 GeV full LHC injection batch of 3.4·1013 p+ in 288 bunches, and was extracted with the wrong trajectory. The incident causes have been identified, with details reconstructed from the logged data and the damage to the vacuum chamber. The remedial measures which were taken are explained, and further recommendations made concerning the interlocking system performance and tests, as well as the operational procedures which must be adopted when commissioning with high intensities. The specific issues of how the incident happened, why the existing protection system was not sufficient and what can/has been done about it are addressed.  
 
WEBX02 Observation of Emittance Growth at the injection in the KEK PS Main Ring injection, emittance, proton, space-charge 250
 
  • S. Igarashi, T. Miura, E. Nakamura, Y. Shimosaki, M. J. Shirakata, K. Takayama, T. Toyama
    KEK, Ibaraki
  We have been studying the emittance growth and beam loss mechanism during the injection period of the 12 GeV main ring of the KEK proton synchrotron to achieve higher intensity. The typical beam loss is about 30 % during the injection period of 500 milliseconds for the high intensity operation. Measurement of the transverse beam profiles using flying wires has revealed a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced for higher beam intensity and could not be explained with the injection mismatch. A resonance created by the space charge field was the cause of the emittance growth. A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully reproduced the beam profiles.  
 
WEBX04 Measurement strategy for the CERN Linac4 Chopper-line linac, rfq, quadrupole, booster 262
 
  • J.-B. Lallement, K. Hanke, H. Hori, A. M. Lombardi, E. Zh. Sargsyan
    CERN, Geneva
  Linac4 is a new accelerator under study at CERN. It is designed to accelerate H- ions to 160 MeV of energy, for injection into the existing Proton Synchrotron Booster. The low energy section, comprising an H- ion source, a 352 MHz Radio Frequency Quadrupole and a 3 MeV chopper line will be assembled at CERN in the next years. Linac 4 is also designed as an injector for the SPL, a high power proton driver delivering 5MW at 3.5 GeV. In this case the beam losses must be limited to 1 W/m and therefore the formation of transverse and longitudinal halo at low energy becomes a critical issue which has to be measured and controlled. The chopper-line is composed of 11 quadrupoles, 3 bunchers and the chopper itself. Its beam dynamics will be characterized with specific detectors and diagnostic lines. In particular the transverse and longitudinal halo will be measured by a Beam Shape and Halo Monitor (BSHM) with a sensitivity of 10.000 particles per bunch and a time resolution of 2ns. In this paper we present the simulation work in preparation for the measurement campaign scheduled in 2008.  
 
WEBX05 Scaling laws for space charge resonances emittance, resonance, space-charge, focusing 268
 
  • I. Hofmann, G. Franchetti
    GSI, Darmstadt
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  Space charge can be the driving term of nonlinear resonances, like the resonant emittance exchange 2Qx-2Qy=0 ("Montague resonance", in linacs and high-intensity rings), or the fourth-order structure resonance 4Qx=n (high-intensity rings, FFAG's). In this study we present scaling laws to describe the dependence of the expected emittance growth effect on the initial emittances, the tune shift and/or the crossing rate through the resonance.  
 
WEBY03 Experimental studies of IBS in RHIC and comparison with theory emittance, ion, lattice, coupling 259
 
  • A. V. Fedotov, W. Fischer, S. Tepikian, J. Wei
    BNL, Upton, Long Island, New York
  A high-energy electron cooling system is presently being developed to overcome emittance growth due to Intra-beam Scattering (IBS) for heavy ion operation in RHIC. A critical item for choosing appropriate parameters of the cooler is an accurate description of the IBS. The analytic models were verified vs dedicated IBS measurements. Analysis of the 2004 data with the Au ions showed very good agreement for the longitudinal growth rates but significant disagreement with exact IBS models for the transverse growth rates. Experimental measurements were improved for the 2005 run with the Cu ions. Here, we present comparison of the 2005 data with theoretical models.  
 
THAW01 New simulation capabilities of electron clouds in ion beams with large tune depression electron, ion, quadrupole, bunching 279
 
  • J.-L. Vay, M. A. Furman, P. A. Seidl
    LBNL, Berkeley, California
  • R. H. Cohen, A. Friedman, D. P. Grote, M. Kireeff Covo, A. W. Molvik
    LLNL, Livermore, California
  • P. Stoltz, S. A. Veitzer
    Tech-X, Boulder, Colorado
  • J. Verboncoeur
    UCB, Berkeley, California
  We have developed a new, comprehensive set of simulation tools aimed at modeling the interaction of intense ion beams and electron clouds (e-clouds). The set contains the 3-D accelerator PIC code WARP and the 2-D “slice” e-cloud code POSINST [M. Furman, this workshop], as well as a merger of the two, augmented by new modules for impact ionization and neutral gas generation. The new capability runs on workstations or parallel supercomputers and contains advanced features such as mesh refinement, disparate adaptive time stepping, and a new “drift-Lorentz” particle mover for tracking charged particles in magnetic fields using large time steps. It is being applied to the modeling of ion beams (1 MeV, 180 mA, K+) for heavy ion inertial fusion and warm dense matter studies, as they interact with electron clouds in the High-Current Experiment (HCX) [experimental results discussed by A. Molvik, this workshop]. We will describe the capabilities and simulation results with detailed comparisons against the HCX experiment, as well as their application (in a different regime) to the modeling of e-clouds in the Large Hadron Collider (LHC).  
 
THAW02 New experimental measurements of electron clouds in ion beams with large tune depression* electron, quadrupole, ion, diagnostics 288
 
  • A. W. Molvik, R. H. Cohen, A. Friedman, M. Kireeff Covo
    LLNL, Livermore, California
  • F. M. Bieniosek, P. A. Seidl, J.-L. Vay
    LBNL, Berkeley, California
  We study electron clouds in high perveance beams (K = 8E-4) with a large tune depression of 0.2 (defined as the ratio of a single particle oscillation response to the applied focusing fields, with and without space charge). These 1 MeV, 180 mA, K+ beams have a beam potential of +2 kV when electron clouds are minimized. Simulation results are discussed in a companion paper [J-L. Vay, this Conference]. We have developed the first diagnostics that quantitatively measure the accumulation of electrons in a beam [M. Kireeff Covo, et al., to be submitted to Phys. Rev. Lett.]. This, together with measurements of electron sources, will enable the electron particle balance to be measured, and electron-trapping efficiencies determined. We measure and simulate ~10 MHz electron oscillations in the last quadrupole magnet when we flood the beam with electrons from an end wall. Experiments where the heavy-ion beam is transported with solenoid magnetic fields, rather than with quadrupole magnetic or electrostatic fields, are being initiated. We will discuss the initial results using electrode sets (in the middle and at the ends of magnets) to either expel or to trap electrons within the magnets.  
 
THAY02 Progress in slip stacking and barrier-RF injection, booster, target, antiproton 293
 
  • K. Seiya, T. Berenc, B. Chase, W. Chou, J. E. Dey, P. W. Joireman, I. Kourbanis, J. Reid, D. Wildman
    Fermilab, Sequim, Washington
  Slip stacking for pbar production has been operational since December 2004 and increased the beam intensity on pbar target more than 60%. We plan to use slip stacking for NuMI neutrino experiment for effectively increasing intensity to NuMI target by about a factor two in a 2.2 sec MI cycle. In parallel with slip stacking, we plan to study fast momentum stacking using barrier buckets. One barrier rf system has been installed and tested, and second system is being installed during the current shutdown.  
 
THAZ04 Commissioning and Operational Scenarios of the LHC Beam Loss Monitor System beam-losses, collimation, superconducting-magnet, ion 314
 
  • E. B. Holzer
    CERN, Geneva
  One of the most critical elements for the protection of CERN’s Large Hadron Collider (LHC) is its beam loss monitoring (BLM) system. It aims to prevent the super conducting magnets from quenching and to protect the machine components from damages, as a result of critical beam losses. The contribution will discuss the commissioning procedures of the BLM system and the envisaged operational scenarios. About 4000 monitors will be installed around the ring. The specification for the BLM system includes a factor of 2 absolute precisions on the prediction of the quench levels, a wide range of integration times (100 us to 100 s) and a fast (one turn) trigger generation. When the loss rate exceeds a pre-defined threshold value, a beam abort is requested. Magnet quench and damage levels vary as a function of beam energy and loss duration. Consequently, the beam abort threshold values vary accordingly. By measuring the loss pattern, the BLM system helps to identify the loss mechanism. Furthermore, it will be an important tool for commissioning, machine setup and studies. Special monitors will be used for the setup and control of the collimators.  
 
THBW02 Electron-Cloud Benchmarking & CARE-HHH Codes electron, emittance, vacuum, single-bunch 350
 
  • F. Zimmermann
    CERN, Geneva
  The state-of-the-art in code benchmarking for various types of electron-cloud simulations is reviewed. In particular, we recall possible meanings of benchmarking, summarize past and more recent code comparisons, present examples of code verifications against machine experiments, describe some remaining uncertainties, and formulate a few goals for the future. The code-benchmarking effort is supported by the CARE-HHH initiative on accelerator physics simulation codes, whose other objectives include a common web repository and the practical extension of simulation codes.  
 
THBZ05 The SNS linac commissioning – comparison of measurement and model* optics, emittance, linac, lattice 353
 
  • D.-O. Jeon
    ORNL, Oak Ridge, Tennessee
  The Spallation Neutron Source linac commissioning was an excellent opportunity to benchmark the model with the measurement data for a high intensity linac. A new halo formation mechanism due to large beam eccentricity predicted by simulation was confirmed through a series of emittance measurement. Also the phase scan technique and the acceptance scan technique were benchmarked. Commissioning both demonstrated the validity of the model and revealed the shortfall of the model.  
 
FRAP01 SUMMARY OF WORKING GROUP A AND A+B+D JOINT SESSION electron, impedance, emittance, feedback 358
 
  • F. Zimmermann
    CERN, Geneva
  • A. V. Burov
    Fermilab, Batavia, Illinois
  We summarize the presentations and discussions of the HB2006 Working Group A, devoted to beam instabilities, and of the joint session of Working Groups A, B (on space charge), and D (beam cooling and experiments). First we review the progress on conventional instabilities and impedances, and then the advances on electron cloud.  
 
FRAP02 Summary of Working Gropu B space-charge, resonance, beam-losses, linac 363
 
  • S. M. Cousineau
    ORNL, Oak Ridge, Tennessee
  
FRAP05 Summary of Working Group D electron, ion, scattering, beam-cooling 372
 
  • A. V. Fedotov, J. Wei
    BNL, Upton, Long Island, New York
  • I. N. Meshkov
    JINR, Dubna, Moscow Region
  
FRAP08 Summary of General Working Group A+B+D with a Focus on Code Benchmarking electron, resonance, emittance, site 379
 
  • J. Wei
    BNL, Upton, Long Island, New York
  • I. Hofmann
    GSI, Darmstadt
  • E. N. Shaposhnikova, F. Zimmermann
    CERN, Geneva