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Lee, S.-Y.

Paper Title Page
MOOAAB04 Quadruple-bend Achromatic Low Emittance Lattice Studies 86
 
  • M.-H. Wang, H.-P. Chang, H. C. Chao, P. J. Chou, C.-C. Kuo
    NSRRC, Hsinchu
  • S.-Y. Lee, F. Wang
    IUCF, Bloomington, Indiana
 
  A quadruple-bend-achromatic (QBA) cell, defined as a super cell made of two double-bend (DB) cells with different outer and inner dipole bend angles, is found to provide a factor of two in lowering the beam emittance of electron synchrotron light sources. The ratio of bending angles of the inner dipoles to that of the outer dipoles is numerically found to be about 1.51.6 for an optimal low beam emittance in the isomagnetic condition. The QBA lattice provides an advantage over the double-bend achromat or the double-bend non-achromat in performance by providing some zero dispersion straight-sections and a small natural beam emittance. A lattice with 12 QBA cells with a preliminary dynamic aperture study serves as an example. The effects of the different types of insertion devices (ID) on the emittance in dispersive long straight and non-dispersive long straight are also simulated and reported.  
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MOPAS050 Active Damping of the e-p Instability at the LANL PSR 548
 
  • R. C. McCrady, R. J. Macek, S. B. Walbridge, T. Zaugg
    LANL, Los Alamos, New Mexico
  • S. Assadi, C. Deibele, S. Henderson, M. A. Plum
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • M. T.F. Pivi
    SLAC, Menlo Park, California
 
  Funding: This work was supported by the United States Department of Energy under contracts DE-AC52-06NA25396 and W-7405-ENG-36.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance.

 
TUZAAB03 Emittance Measurement and Modeling for the Fermilab Booster 799
 
  • X. Huang
    SLAC, Menlo Park, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • K. Y. Ng
    Fermilab, Batavia, Illinois
 
  Funding: DOE/NSF

We systematically measured the emittance evolution of a fast cycling proton accelerator on a turn-by-turn basis under various beam intensities via an ionization profile monitor (IPM). The vertical emittance growth rate was derived and phenomenologically analyzed. The transverse and longitudinal components in the horizontal beam size were separated by making use of their different evolution behaviors. The quadrupole mode beam size oscillation after transition crossing is also studied and explained. We found a considerable space-charge-induced emittance growth rate component in the vertical plane but not as much for the horizontal plane. We carried out multiparticle simulations to understand the mechanism of space-charge-induced emittance growth. The major sources of emittance growth were found to be the random skew-quadrupole and dipole field errors in the presence of large space-charge tune spread.

PRSTAB 9, 014202 (2006)

 
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TUOCAB01 A New Code for Orbit Response Matrix Analysis 804
 
  • L. Yang, S.-Y. Lee
    IUCF, Bloomington, Indiana
  • X. Huang
    SLAC, Menlo Park, California
  • B. Podobedov
    BNL, Upton, Long Island, New York
 
  Funding: NSF PHY-0552389, DOE DE-FG02-92ER40747

The Orbit Response Matrix (ORM) has been successfully used extensively in accelerator modeling. However, in many cases, the existing codes can not find a correct model. We develop a new code that solve the convergence and coupling problems. We test our code by carrying out systematic study of accelerator models. Effects measurement errors and the completeness of information will be addressed in this study. Possible inclusion of phase information will be discussed.

 
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TUPMS007 NSLS VUV Ring Lifetime Study 1203
 
  • L. Yang, S.-Y. Lee
    IUCF, Bloomington, Indiana
  • S. L. Kramer, B. Podobedov
    BNL, Upton, Long Island, New York
 
  Beam lifetime at VUV ring of National Synchrotron Light Source(NSLS) at BNL is limited by Touschek effect. This effect is affected by momentum acceptance and beam density. The geometry near injection septum, dynamic aperture and the RF acceptance all can limit the over all momentum acceptance. Extensive experiments including coupling, gas scattering, RF acceptance, have been done for understanding the lifetime, and the result is confirmed with theoretical predictions.  
WEXC01 Experimental Tests of a Prototype System for Active Damping of the E-P Instability at the LANL PSR 1991
 
  • C. Deibele, S. Assadi, V. V. Danilov, S. Henderson, M. A. Plum, A. K. Polisetti
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • J. D. Gilpatrick, R. C. McCrady, J. F. Power, T. Zaugg
    LANL, Los Alamos, New Mexico
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • M. T.F. Pivi
    SLAC, Menlo Park, California
  • M. J. Schulte, Z. P. Xie
    UW-Madison, Madison, Wisconsin
 
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This talk describes the system configuration, results of several experimental tests and studies of system optimization along with studies of the factors limiting its performance.

 
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THPAN016 Improving the SIS18 Performance by use of the Orbit Response Method 3256
 
  • A. S. Parfenova, G. Franchetti, I. Hofmann, C. Omet
    GSI, Darmstadt
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
 
  The SIS18 will be used as a booster for the new FAIR facility SIS100. A well-controlled linear optics of the SIS18 is necessary for further optimisation studies of nonlinear dynamics, resonance induced beam loss, dynamic aperture and nonlinear error measurements. The analysis of the orbit response matrix (ORM) is a powerful tool to calibrate the linear lattice models. We present results of several measurements on the SIS18 using the ORM and discuss the achieved improvement of the SIS18 performance.  
THPAS011 Investigation of Residual Vertical Intrinsic Resonances with Dual Partial Siberian Snakes in the AGS 3534
 
  • F. Lin, S.-Y. Lee
    IUCF, Bloomington, Indiana
  • L. Ahrens, M. Bai, K. A. Brown, E. D. Courant, J. W. Glenn, H. Huang, A. U. Luccio, W. W. MacKay, T. Roser, N. Tsoupas
    BNL, Upton, Long Island, New York
 
  Funding: The work was performed under the US Department of Energy Contract No. DE-AC02-98CH1-886, No. DE-FG02-92ER40747, NSF PHY-0552389, and with support of RIKEN(Japan) and Renaissance Technologies Corp.(USA)

Two partial helical dipole snakes were found to be able to overcome all imperfection and intrinsic spin resonances provided that the vertical betatron tunes were maintained in the spin tune gap near the integer 9. Recent vertical betatron tune scan showed that the two weak resonances at the beginning of the acceleration cycle may be the cause of polarization loss. This result has been confirmed by the vertical polarization profile measurement, and spin tracking simulations. Possible cure of the remaining beam polarization is discussed.

 
THPAS013 Electron Cloud Simulations to Cold PSR Proton Bunches 3540
 
  • Y. Sato, S.-Y. Lee
    IUCF, Bloomington, Indiana
  • J. A. Holmes
    ORNL, Oak Ridge, Tennessee
  • R. J. Macek
    LANL, Los Alamos, New Mexico
 
  Funding: SNS through UT-Battelle, LLC, DE-AC05-00OR22725 for the U. S. DOE. Indiana University Bloomington, PHY-0552389 for NSF and DE-FG02-92ER40747 for DOE. LANL, W-7405-ENG-36.

We present ORBIT code simulations to examine the sensitivity of electron cloud properties to different proton beam profiles and to reproduce experimental results from the proton storage ring at Los Alamos National Laboratory. We study the recovery of electron clouds after sweeping, and also the characteristics of two types of electrons signals (prompt and swept) as functions of beam charge. The prompt signal means the peak height of electron sweeper signal before high voltage pulse applied on its electrode and after beam accumulation, and the swept signal means the spike height of electron sweeper signal during the high voltage pulse. To concentrate on the electron cloud dynamics, we use a cold proton bunch to generate primary electrons and electromagnetic field for electron dynamics. However, the protons receive no feedback from the electron cloud. Our simulations indicate that the proton loss rate in the field-free straight section might be an exponential function of proton beam charge and may also be lower than the averaged proton loss rate in a whole ring.