Author: Liu, C.
Paper Title Page
MOPPC023 Polarization Transmission at RHIC, Numerical Simulations 178
 
  • F. Méot, M. Bai, C. Liu, M.G. Minty, V.H. Ranjbar
    BNL, Upton, Long Island, New York, USA
 
  Ray-tracing methods, using the computer code Zgoubi, have proven efficient for beam and spin dynamics simulations in RHIC (see earlier PAC and IPAC publications). More simulations and results are being produced, including spin code benchmarking and cross-checking, effects of strongest resonances and working point on transport of polarization, polarization with Run 9 and Run 11 measured ramp orbit and optics, polarization profiles, etc. The numerical methods involved are recalled, a status of the work is given.  
 
MOPPC025 RHIC Polarized Proton Operation in Run 12 184
 
  • V. Schoefer, L. A. Ahrens, A. Anders, E.C. Aschenauer, G. Atoian, M. Bai, J. Beebe-Wang, M. Blaskiewicz, J.M. Brennan, K.A. Brown, D. Bruno, R. Connolly, T. D'Ottavio, A. Dion, K.A. Drees, W. Fischer, C.J. Gardner, J.W. Glenn, X. Gu, M. Harvey, T. Hayes, L.T. Hoff, H. Huang, R.L. Hulsart, A. Kirleis, J.S. Laster, C. Liu, Y. Luo, Y. Makdisi, G.J. Marr, A. Marusic, F. Méot, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, S. Nemesure, A. Poblaguev, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser, W.B. Schmidke, F. Severino, D. Smirnov, K.S. Smith, D. Steski, S. Tepikian, D. Trbojevic, N. Tsoupas, J.E. Tuozzolo, G. Wang, M. Wilinski, K. Yip, A. Zaltsman, A. Zelenski, K. Zeno, S.Y. Zhang
    BNL, Upton, Long Island, New York, USA
 
  Successful RHIC operation with polarized protons requires meeting demanding and sometimes competing goals for maximizing both luminosity and beam polarization. In Run 12 we sought to fully integrate into operation the many systems that were newly commissioned in Run 11 as well as to enhance collider performance with incremental improvements throughout the acceleration cycle. For luminosity maximization special attention was paid to several possible source of emittance dilution along the injector chain, in particular to optical matching during transfer between accelerators. Possible sources of depolarization in the AGS and RHIC were also investigated including the effects of local coupling and low frequency (10 Hz) oscillations in the vertical equilibrium orbit during the RHIC ramp. The results of a fine storage energy scan made in an effort to improve store polarization lifetime are also reported in this note.  
 
MOPPD070 A SVD-based Orbit Steering Algorithm for RHIC Injection 523
 
  • C. Liu, A. Marusic, M.G. Minty, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The RHIC physics programs involve experiments with polarized proton and several species of ion beams. In the past, when switching between physics programs, first turn and circulating beam in RHIC was established manually by adjustments to the corrector dipoles for minimum beam loss. In this report, we introduce a new steering scheme based on an SVD algorithm which uses a single-pass orbit response matrix for first turn steering. The new scheme was implemented into the controls system and demonstrated successfully in Run-11. Establishing circulating beam using this automated approach has been shown to dramatically reduce the beam setup time.
 
 
MOPPD071 Error Localization in RHIC by Fitting Difference Orbit 526
 
  • C. Liu, M.G. Minty, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Many errors in an accelerator are evidenced as transverse kicks to the beam, which distort the beam trajectory. Therefore, the information of the errors are imprinted in the distorted orbits, which are different from what would be predicted by the optics model. In this paper, we introduce an algorithm for fitting the orbit based on an on-line optics model. We apply the algorithm to localize the location of the elusive source of vertical diurnal variations observed in RHIC, and analyze D0/Dx errors in local coupling measurement.
 
 
WEPPP083 Near Real-time Response Matrix Calibration for 10-Hz GOFB 2903
 
  • C. Liu, R.L. Hulsart, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 10-Hz global orbit feedback, for damping the trajectory perturbation (~10 Hz) due to the vibrations of the triplets, is operational for injection and store in RHIC. The operation of the system has been performed using transfer functions between the beam position monitors and correctors obtained from the online optics model and a correction algorithm based on singular value decomposition (SVD). Calibration of the transfer functions by measuring the beam position oscillations while modulating the dedicated correctors has been carried out. The feedback results with model matrix and measured matrix will be compared.
 
 
WEPPP084 Weighted SVD Algorithm for Close-Orbit Correction and 10 Hz Feedback in RHIC 2906
 
  • C. Liu, R.L. Hulsart, A. Marusic, R.J. Michnoff, M.G. Minty, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Measurements of the beam position along an accelerator are typically treated equally using standard SVD-based orbit correction algorithms so distributing the residual errors, modulo the local beta function, equally at the measurement locations. However, sometimes a more stable orbit at select locations is desirable. In this paper, we introduce an algorithm for weighting the beam position measurements to achieve a more stable local orbit. The results of its application to close-orbit correction and 10-Hz orbit feedback will be shown and analyzed.
 
 
THPPP029 Simultaneous Global Coupling and Vertical Dispersion Correction in RHIC 3794
 
  • C. Liu, Y. Luo, M.G. Minty
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Residual vertical dispersion on the order of ±0.2 m (peak to peak) has been measured at store energies for both polarized proton and heavy ion beams. The hypothesis is that this may have impact on the polarization transmission efficiency during the energy ramp, the beam lifetimes, and, especially for heavy ions, the dynamics aperture. An algorithm to correct global coupling and dispersion simultaneously using skew quads was developed for RHIC. Simulation results together with the measured coupling and dispersion functions before and after correction will be shown for both injection and store together with an assessment of overall collider performance improvement.
 
 
MOPPC059 Various Approaches to Electromagnetic Field Simulations for RF Cavities 268
 
  • C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by BMBF under contract 05H09RD5.
The Superconducting Proton Linac (SPL) cavity is mainly designed and conducted by CERN. It is a part of the planned injector upgrade of the Large Hadron Collider (LHC). The SPL cavity is used to accelerate the ion beam from 160 MeV to 5GeV and served as a driver for neutrino facilities and radioactive beam facilities. In the Superconducting Proton Linac (SPL) cavity, it is very important to calculate the eigenmodes precisely, because many higher-order modes (HOMs) can lead to particle beam instabilities. We used and compared three different ways to calculate the eigenmodes in the SPL cavity: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain, and field simulation with tetrahedral mesh and higher order curvilinear elements. In this paper the principles of the three numerical methods will be introduced and compared. Finally the calculated results will be presented.