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resonance

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TUAX03 Beam loss, emittance growth and halo formation due to the pinched electron cloud electron, emittance, simulation, synchrotron 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.  
 
WEAX01 Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments beam-losses, emittance, 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, sextupole, emittance 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.  
 
WEAX06 Measurements and Synergia simulations of emittance dilution at the Fermilab Booster. simulation, 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.  
 
WEAY03 Experimental studies of stability issues at HIMAC cooler ion, electron, feedback, injection 197
 
  • K. Noda, T. Fujisawa, T. Honma
    NIRS, Chiba-shi
  • M. Aiba, Y. Hashimoto
    KEK, Ibaraki
  • S. Shibuya
    AEC, Chiba
  • E. Syresin
    JINR, Dubna, Moscow Region
  • T. Uesugi
    KURRI, Osaka
  We have investigated coherent transverse instability when high-density circulating-ion beam was obtained with cool-stacking injection in the HIMAC synchrotron. By using a cooled beam and the Oxygen gas-sheet beam profile monitor, further, we have observed a particle trapping in resonance crossing. We will report these experimental studies at the HIMAC synchrotron.  
 
WEBX05 Scaling laws for space charge resonances emittance, 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 emittance, quadrupole, space-charge, injection 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.  
 
THAW07 Transverse electron-antiproton instability in the Recycler Ring coupling, electron, ion, impedance 334
 
  • A. V. Burov
    Fermilab, Batavia, Illinois
  Lifetime degradation of electron-cooled ions was observed at several electron coolers. In the Recycler, both the lifetime drop and emittance growth of the e-cooled pbars are seen. A possible reason for that can be a coherent interaction between the electron and antiproton beams. A theoretical model of this instability is presented, and a practical recommendation for its suppression is explained and discussed.  
 
THAY03 Challenges for hadron (and leptons) nonscaling FFAGs acceleration, proton, lattice, betatron 303
 
  • A. G. Ruggiero
    BNL, Upton, Long Island, New York
  The concept of Fixed-Field Alternating-Gradient (FFAG) accelerators was introduced about a half century ago. Few prototypes were built soon after and successfully placed in operation. Nevertheless, because of the perceived complexity of the early model magnets and design, the concept was soon abandoned in favor of cyclotrons, synchrotrons and linacs. It was subsequently occasionally revived for possible application as spallation neutron sources; but it was only recently that, because of the need of fast acceleration of muons, that FFAGs were re-considered and studied with more attention. Two prototypes were eventually built and operated at KEK for the acceleration of Protons. The interest indeed soon switched more steadily toward acceleration of protons (and electrons) as application for high-power proton drivers and medical accelerators. The paper describes the design procedure of a proton FFAG accelerator that employs a Non-Scaling lattice and exposes the main inherent issues, namely: the crossing of multiple resonances, space-charge at injection, and the fast acceleration rate that may impose limitations on the RF cavity hardware.  
 
THBW01 Code benchmarking on induce space charge particle trapping space-charge, emittance, 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.  
 
FRAP02 Summary of Working Gropu B space-charge, simulation, beam-losses, linac 363
 
  • S. M. Cousineau
    ORNL, Oak Ridge, Tennessee
  
FRAP08 Summary of General Working Group A+B+D with a Focus on Code Benchmarking electron, simulation, emittance, site 379
 
  • J. Wei
    BNL, Upton, Long Island, New York
  • I. Hofmann
    GSI, Darmstadt
  • E. N. Shaposhnikova, F. Zimmermann
    CERN, Geneva