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Hoffstaetter, G.

Paper Title Page
MOOBAB02 Progress Toward an ERL Extension to CESR 107
  • G. Hoffstaetter, I. V. Bazarov, G. W. Codner, M. Forster, S. Greenwald, Y. Li, M. Liepe, C. E. Mayes, C. K. Sinclair, C. Song, A. Temnykh, M. Tigner, Y. Xie
    CLASSE, Ithaca
  • D. H. Bilderback, D. S. Dale, K. Finkelstein, S. M. Gruner
    CHESS, Ithaca, New York
  • B. M. Dunham
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • D. Sagan
    Cornell University, Department of Physics, Ithaca, New York
  Funding: Supported by Cornell University and NSF grant PHY 0131508

The status of plans for an Energy-Recovery Linac (ERL) X-ray facility at Cornell University is described. Currently, Cornell operates the Cornell High Energy Synchrotron Source (CHESS) at the CESR ring and the ERL is planned to be an extension to the CESR ring with the addition of a 5-GeV superconducting c.w. linac. Topics covered in this paper include the full layout on the Cornell campus, the different operation modes of the accelerator, methods to limit emittance growth, control of beam-ion effects and ways to limit transverse instabilities. As an upgrade of the CESR ring, special attention is given to reuse of many of the existing components. The very small electron-beam emittances would produce an x-ray source that is highly superior than any existing storage-ring light source. The ERL includes 18 X-ray beamlines optimized for specific areas of research that are currently being defined by an international group of scientists. This planned upgrade illustrates how other existing storage rings could be upgraded to work as ERL light sources with vastly improved beam qualities and with limited dark time for x-ray users.

slides icon Slides  
TUPMS019 Ion Effects and Ion Elimination in the Cornell ERL 1218
  • G. Hoffstaetter, Ch. Spethmann, Y. Xie
    CLASSE, Ithaca
  Funding: Supported by Cornell University and NSF grant PHY 0131508

In an energy recovery linac (ERL) where beam-loss has to be minimal, and where beam positions and emittances have to be very stable in time, optic errors and beam instabilities due to ion effects have to be avoided. Here we explain why ion clearing electrodes are the least unattractive way of eliminating ions in an ERL and we present calculations of the remnant ion density and its effect on the beam. We also show a design of the clearing electrodes that should be distributed around the accelerator and illustrate their wake-field properties.

TUPMS022 Beam Breakup Simulations for the Cornell X-ray ERL 1227
  • C. Song, G. Hoffstaetter
    CLASSE, Ithaca
  Funding: Supported by Cornell University and NSF grant PHY 0131508

Multi-pass, multi-bunch beam-breakup (BBU) can limit the current in linac-based recirculating accelerators. We have therefore made the computation of the transverse and longitudinal BBU-threshold current available in Cornell's main optics design and beam simulation library BMAD. The coupling of horizontal and vertical motion as well as time of flight effects are automatically contained. Subsequently we present a detailed simulation study of transverse and longitudinal BBU in the proposed 5GeV Energy Recovery Linac light source at Cornell University, including the use of frequency randomization, polarized cavities and optical manipulations to improve the threshold current.

THPAS043 Controlling Coupler-kick Emittance Growth in the Cornell ERL Main Linac 3591
  • B. W. Buckley, G. Hoffstaetter
    CLASSE, Ithaca
  Funding: Supported by Cornell University and NSF grant PHY 0131508

One of the main concerns in the design of a high energy Energy Recovery Linac x-ray source is the preservation of beam emittance. Discussed is one possible source of emittance dilution due to transverse electromagnetic fields in the accelerating cavities of the linac caused by the power coupler geometry. This has already been found to be a significant effect in Cornell's ERL injector cavities if only one coupler per cavity is chosen. Here we present results of simulations for Cornell's main ERL linac with three possible coupler configurations and compare them with regards to total normalized emittance growth after one complete pass through the linac. We explain why the sign of the phase between the transverse kick and the accelerating force alternates each cavity, which leads to a cancellation of the emittance growth to acceptable values. We also investigate the effect of cavity detuning on the coupler-kick effect.

THPAS045 Method of Perturbative-PIC Simulation for Interactions between a Bunch and Its Synchrotron Radiation 3594
  • J. Shi
    KU, Lawrence, Kansas
  • G. Hoffstaetter
    CLASSE, Ithaca
  Funding: This work is supported by the US Department of Energy under Grant No. DE-FG02-04ER41288.

A self-consistant simulation method is developed for the study of coherent synchrotron radiation effects by using a perturbation expansion of retarded radiation field and the particle-in-cell method. The perturbation expansion of the radiation field is based on the fact that the time dependance of a bunch particle distribution has typically two significantly different time scales, a fast time scale related to the linear dynamics and a slow time scale of the beam-size growth due to nonlinear perturbations. Since the scale of the retardation of the radiation field is usually much shorter than the slow time scale of the particle distribution, the retardation on the slow time scale of the particle distribution is treated perturbatively while the retardation on the fast time scale is removed by transformations associated the linear lattice. With this method, the particle-radiation interaction can be calculated in configuration space without memorizing the history of the particle distribution.