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emittance

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MOAP02 Recent Beam Commissioning Results from the Spallation Neutron Source linac, target, extraction, proton 6
 
  • S. Henderson
    ORNL, Oak Ridge, Tennessee
  The Spallation Neutron Source accelerator complex consists of a 2.5 MeV H- front-end injector system, a 186 MeV normal-conducting linear accelerator, a 1 GeV superconducting linear accelerator, an accumulator ring and associated beam transport lines. The beam commissioning campaign of the SNS accelerator complex, initiated in 2002, has been performed in seven discrete runs as each successive portion of the accelerator complex has been installed. The final beam commissioning run, in which beam was transported to the liquid mercury target was recently completed. In the course of beam commissioning, most beam performance parameters and beam intensity goals have been achieved at low duty factor. The beam performance and beam dynamics measurements of the linac and ring will be presented.  
 
MOAP04 Recent progresses on FFAG accelerators proton, acceleration, focusing, target 16
 
  • Y. Mori
    KURRI, Osaka
 
TUAX03 Beam loss, emittance growth and halo formation due to the pinched electron cloud electron, simulation, 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.  
 
TUAX06 Electron cloud and single-bunch instabilities in the Relativistic Heavy Ion Collider electron, beam-losses, vacuum, ion 117
 
  • J. Wei, M. Bai, M. Blaskiewicz, P. Cameron, R. Connolly, A. Della Penna, W. Fischer, H.-C. Hseuh, H. Huang, R. C. Lee, R. J. Michnoff, V. Ptitsyn, T. Roser, T. Satogata, S. Tepikian, S. Y. Zhang
    BNL, Upton, Long Island, New York
  • U. Iriso
    CELLS, Bellaterra (Cerdanyola del Vallès)
  • L. Wang
    SLAC, Menlo Park, California
  Electron cloud is one of the leading mechanisms that limit the performance of high intensity circular accelerators and colliders. Electron cloud in RHIC is in an intermediate regime sharing features of both the long-bunch (PSR) and short-bunch (photon factories) machines. Vacuum-pressure rises, transverse tune shifts, and electron flux are observed at injection, upon transition crossing, and at top energy. Transverse emittance growth, fast instabilities, and beam loss also occur upon transition crossing. Mitigation measures are implemented both to reduce the production of electron cloud and to control the beam stability. This paper summarizes the observation and initial analysis of the electron-cloud effects at RHIC.  
 
TUAY02 End-to-end beam dynamics for CERN Linac4 linac, rfq, quadrupole, booster 79
 
  • A. M. Lombardi, G. Bellodi, J.-B. Lallement, S. Lanzone, E. Zh. Sargsyan
    CERN, Geneva
  • M. A. Baylac
    LPSC, Grenoble
  • R. Duperrier, D. Uriot
    CEA, Gif-sur-Yvette
  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 of H- ions up to 160 MeV for injection into the CERN Proton Synchrotron Booster. The acceleration is done in three stages : up to 3 MeV with a Radio Frequency Quadrupole (the IPHI RFQ) operating at at 352 MHz, then continued to 90 MeV with drift-tube structures at 352 MHz (conventional Alvarez and Cell Coupled Drift Tube Linac) and, finally, with a Side Coupled Linac at 700MHz. The accelerator is completed by a chopper line at 3 MeV and a transport and matching line to the PS booster. After the overall layout was determined based on general consideration of beam dynamics and RF, a global optimisation based on end-to-end simulation has refined some design choices. The results and lessons learned from the end-to-end simulations are reported in this paper.  
 
TUAY04 Beam Dynamics Design of the PEFP 100 MeV Linac linac, proton, quadrupole, rfq 99
 
  • J.-H. Jang, Y.-S. Cho, K. Y. Kim, Y.-H. Kim, H.-J. Kwon
    KAERI, Daejon
  The Proton Engineering Frontier Project (PEFP) is constructing a 100 MeV proton linac in order to provide 20 MeV and 100 MeV proton beams. The linac consists of a 50 keV proton injector including an ion source and a low energy beam transport (LEBT), a 3 MeV radio-frequency quadrupole (RFQ), a 20 MeV drift tube linac (DTL), a medium energy beam transport (MEBT), and the higher energy part (20 MeV ~ 100 MeV) of the 100 MeV DTL. The MEBT is located after the 20 MeV DTL to extract 20 MeV proton beams. The 20 MeV part of the linac was completed and is now under beam test. The higher energy part of the PEFP linac was designed to operate with 8% beam duty. This brief report discusses the design of the PEFP 100MeV linac as well as the MEBT.  
 
TUBX05 Cures for beam instabilities in the CERN SPS and their limitations synchrotron, beam-loading, feedback, injection 153
 
  • E. N. Shaposhnikova
    CERN, Geneva
  The LHC beam in the SPS is unstable with a threshold almost an order of magnitude below the nominal intensity. The cures used to stabilise this beam against coupled bunch instabilities apart from beam feedback, feed-forward and longitudinal damping, include a fourth harmonic RF system and controlled emittance blow-up. The limitations of the two last methods were studied experimentally and are analysed here from the point of view of beam quality requirements at extraction and future intensity increases up to ultimate value.  
 
TUBX06 Betatron Tune Shift due to Nonlinear Resistive-Wall Wake Field damping, impedance, betatron, dipole 159
 
  • F. Zimmermann
    CERN, Geneva
  I present formulae for the coherent and incoherent tune shifts of a single bunch traveling between two parallel resistive plates. It is shown that for the parameters of an LHC prototype collimator in the SPS, both the nonlinear wake-field components, calculated by Piwinski, and the correct time dependence, e.g., as derived by Burov and Lebedev, must be taken into account.  
 
TUBY03 Error study of LINAC 4 linac, simulation, 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, simulation, rfq, 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.  
 
WEAX01 Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments beam-losses, resonance, synchrotron, space-charge 167
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  With the development of high intensity accelerator, the role of space charge effect in a nonlinear lattice gained special attention, as in the FAIR project at GSI, where long term storage of high intensity beams is required. The simultaneous presence of space charge and a nonlinear lattice creates an unprecedented challenge for ring designers as well as a new area of studies in beam physics. We present our understanding of the effect of space charge and chromaticity on the nonlinear beam dynamics of a bunched beam.  
 
WEAX02 Space charge simulation of J-PARC main ring injection, space-charge, resonance, sextupole 177
 
  • A. Y. Molodozhentsev, M. Tomizawa
    KEK, Ibaraki
  The space charge effect in combination with the intrinsic field nonlinearity like the sextupole nonlinearity, used for the chromaticity correction, could lead to significant particle losses in a high beam intensity proton machine. For J-PARC Main Ring (MR) the total particle losses at the ring’s collimator should be less than 1% from the expected maximum beam power of 45kW at the injection energy of 3GeV. To keep the particle losses during the injection process within the required limit it is necessary to optimize the beam parameters from the injector (J-PARC RCS), the collimator aperture of the beam-line from RCS to MR and the collimator aperture of MR. Influence of the structure and non-structure high-order resonances for different working points is discussed. The budget of the beam losses for different MR commissioning scenario is presented.  
 
WEAY02 Electron cooling of 8 GeV antiprotons at Fermilab’s Recycler: Results and operational implications electron, antiproton, extraction, beam-losses 182
 
  • L. R. Prost, D. R. Broemmelsiek, A. V. Burov, K. Carlson, C. Gattuso, M. Hu, T. K. Kroc, J. R. Leibfritz, S. Nagaitsev, S. M. Pruss, G. W. Saewert, C. W. Schmidt, A. V. Shemyakin, M. Sutherland, V. Tupikov, A. Warner
    Fermilab, Batavia, Illinois
  Electron cooling of 8 GeV antiprotons at Fermilab’s Recycler storage ring is now routinely used in the collider operation. It requires a 0.1-0.5 A, 4.3 MeV DC electron beam that reduces the longitudinal phase-space of the circulating antiproton beam. This paper first describes the characteristics of the electron beam that was achieved to successfully cool antiprotons as well as its necessary stability. Then, results from various cooling force measurements along with comparison to a simple non-magnetized model will be presented. Finally, operational aspects of the implementation of electron cooling at the Recycler will be discussed, such as regulation of the cooling rate and the influence of the electron beam on the antiprotons lifetime.  
 
WEAZ01 Overview of beam loss mechanisms in injection and extraction injection, extraction, beam-losses, linac 172
 
  • M. Tomizawa
    KEK, Ibaraki
 
WEAZ03 DESIGN AND TESTS OF A LOW-LOSS MULTI-TURN EJECTION FOR THE CERN PS extraction, septum, kicker, beam-losses 192
 
  • M. Giovannozzi
    CERN, Geneva
  Following the positive results of the three-year measurement campaign at the CERN Proton Synchrotron, the study of a possible implementation of the proposed multi-turn extraction based on beam splitting with stable islands in the transverse phase space was undertaken. A substantial reduction of beam losses, with respect to the present extraction scheme, should be achieved with the proposed technique when delivering the high-intensity proton beams required for the planned CERN Neutrino to Gran Sasso Project. Major modifications to the ring layout are foreseen, such as a new design of the extraction bumps including also the installation of three additional kickers to create a closed-bump over the five turns used to extract the split beam. The ring aperture was reviewed and improvements are proposed to reduce possible beam losses between beam splitting and extraction. The goal consists of implementing the proposed changes by beginning of 2008 and to commission the novel extraction during the 2008 PS physics run.  
 
WEBX02 Observation of Emittance Growth at the injection in the KEK PS Main Ring injection, proton, simulation, 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.  
 
WEBX05 Scaling laws for space charge resonances resonance, space-charge, focusing, simulation 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.  
 
WEBX06 Analysis of emittance growth in the Fermilab Booster quadrupole, space-charge, injection, resonance 271
 
  • K. Y. Ng
    Fermilab, Batavia, Illinois
  • X. Huang
    SLAC, Menlo Park, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  Multi-particle similations are performed to study emittance growth in the Fermilab Booster. Analysis shows that the sourcce of the vertical emittance growth comes mostly from random errors in skew quadrupoles as well as the transverse space-charge force. Random errors in the dipole fields and the Montague resonance do contribute but to a much lesser extent. The effect of random errors in the quadrupoles is small because the betatron envelope tunes are resonably far away from the half-integer stopband.  
 
WEBY03 Experimental studies of IBS in RHIC and comparison with theory ion, simulation, 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.  
 
WEBY04 Refined Models of Intrabeam Scattering scattering, proton, damping, coupling 265
 
  • F. Zimmermann, F. Ruggiero
    CERN, Geneva
  We discuss two extensions of intrabeam-scattering theory. First, starting from the Bjorken-Mtingwa recipe, general formulae are derived for the three electro-magnetic intrabeam scattering growth rates, including non-ultrarelativistic terms and vertical dispersion, but maintaining a Gaussian beam approximation. A few applications demonstrate the importance of the vertical dispersion. Second, aside from electromagnetic interactions, hadrons may also undergo nuclear scattering off each other. We estimate the magnitude of this process, and argue that the loss rate due to “nuclear intrabeam scattering” could become significant in high-energy proton or ion storage rings, such as the LHC.  
 
WEBZ02 BEAM TRACKING FOR J-PARC 3 GEV RCS INJECTION injection, septum, electron, quadrupole 253
 
  • M. J. Shirakata, H. Fujimori
    KEK, Ibaraki
  • Y. Irie, T. Takayanagi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  In the J-PARC 3 GeV RCS injection system, the orbit-bump magnets of large-bore are located close with each other, and the incoming beam passes through the non-linear field region of the ring quadrupole magnet. Beam behavior under these conditions is analysed by means of the Runge-Kutta method in the three dimensional magnetic field distribution. The charge exchange foil is inserted between the bump magnets. Orbit of the stripped electrons from the foil is also investigated.  
 
THBW01 Code benchmarking on induce space charge particle trapping space-charge, resonance, synchrotron, sextupole 344
 
  • G. Franchetti, I. Hofmann
    GSI, Darmstadt
  • S. Machida
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  Trapping of particles in a high intensity bunch has been studied by using the MICROMAP. The numerical studies were used to interpret the CERN-PS experiments and explore the underlying beam loss/emittance growth mechanisms. We present in this contributed talk the first attempt of code benchmarking in modeling the long term storage of a high intensity bunch. The code benchmarking is initiated between MICROMAP and SIMPSONS.  
 
THBW02 Electron-Cloud Benchmarking & CARE-HHH Codes simulation, electron, 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, simulation, 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, simulation, impedance, 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.  
 
FRAP08 Summary of General Working Group A+B+D with a Focus on Code Benchmarking electron, simulation, resonance, site 379
 
  • J. Wei
    BNL, Upton, Long Island, New York
  • I. Hofmann
    GSI, Darmstadt
  • E. N. Shaposhnikova, F. Zimmermann
    CERN, Geneva