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Overview of 6 km Damping Ring Study Kwang-Je Kim for ANL-FNAL-UIUC Collaboration ILC-Americas Work Shop SLAC, Stanford, CA October 14-16, 2004 6-km Damping Ring Study The 17-km Tesla dog-bone design assumed 20 ns rise- & fall-time kickers.

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overview of 6 km damping ring study

Overview of 6 km Damping Ring Study

Kwang-Je Kim

for ANL-FNAL-UIUC Collaboration

ILC-Americas Work Shop

SLAC, Stanford, CA

October 14-16, 2004

6 km damping ring study
6-km Damping Ring Study
  • The 17-km Tesla dog-bone design assumed 20 ns rise- & fall-time kickers.
  • If kickers with shorter rise & longer fall time are available, damping rings can be “small” using a injection scheme by Joe Rogers.
  • Fast kickers were discussed by Frisch and Gollin.
  • This is an overview of work on a 6-km small damping ring by ANL-FNAL-UIUC collaboration and J. Rogers & A. Wolski.
  • Content:
    • Current status: linear lattice, instability estimates, & alignment sensitivities
    • Plan for a next level study using tools developed for higher brightness light sources
damping ring lattice development
Damping Ring Lattice Development

Initial work started at Fermilab (Amin Xiao’s talk)

  • A 6-km, 5 GeV ring with TME lattice using the procedure discussed in P. Emma and T. Raubenheimer, PRSTAB,4, 021001 (2001)
    • 77 m of wigglers compared to 400 m in TESLA.
    • Higher current in smaller ring than TESLA.
    • Performance similar to the TESLA design.
instability estimates bill ng
Instability Estimates (Bill Ng)
  • Incoherent space charge tune shift=0.026 << 0.31 for TESLA
    • Smaller circumference, larger beam size (larger disp.)
  • Instabilities
    • Longitudinal: Single- & multi-bunch thresholds;safe
    • Transverse: Single bunch threshold; safe multi-bunch threshold; safe with damper
    • Electron cloud: Growth time about 1s with solenoids
    • Fast ion: Growth less than 20% with feedback (@ 10-10)
quadrupole and sextupole alignment sensitivities a wolski
Quadrupole and Sextupole Alignment Sensitivities (A. Wolski)
  • 6-km DR less sensitive than Tesla dogbone
  • Both 6-km DR and Tesla dogbone more sensitive than ATF
the small dr looks doable next step
The “Small” DR Looks Doable. Next Step?
  • Further optimization of parameters
      • Energy (3.7GeV), lattice,
  • Next-level study with tools and technology developed for high-brightness light sources:
    • Impedance modelling and minimization
    • Beam monitoring and feedback
    • Wiggler development
    • Photon absorbers
tools for nonlinear beam dynamics louis emery s talk
Tools for Nonlinear Beam Dynamics(Louis Emery’s Talk)
  • Toolkit approach combined with comprehensive tracking code elegant developed by M. Borland
  • Parallel simplex optimizer being developed by H. Shang
  • An example of future investigation
    • Trade-off in non-linearities between weaker focusing arc cell design and longer wiggler to maximize dynamic aperture
rf bpm diagnostics feedback
RF BPM Diagnostics & Feedback
  • Orbit motion is characterized by a PSD spectrum in range 0 to frev/2
  • RMS orbit jitter at extraction is equal the integral of PSD spectrum
  • Orbit feedback reduces beam motion only in a certain band, say, 0-60 Hz (APS) -> Orbit jitter is reduced somewhat depending on the PSD details
  • For damping ring, higher-bandwidth feedback may be needed to reduce jitter sufficiently
vacuum chamber issues
Vacuum Chamber Issues
  • Minimizing Impedances:
    • Make use “impedance database” obtained by modeling and measuring local impedance (e.g., by orbit response matrix)
  • Suppress electron cloud effects:
    • Employ solenoids, slots, low-secondary-yield-coefficient coatings, and/or corrugation
    • Based on experimental and modelling experiences at APS (K. Harkay, R. Rosenberg, L. Loiacono)
wiggler development
Wiggler Development
  • Radiation damage of PM undulator( M. Petra)
  • Superconducting wiggler (S.H. Kim); Useful for damping wiggler?
  • The LCLS undulator under construction at APS is similar to that used for positron production scheme.
photon absorbers
Photon Absorbers
  • APS dipole fan and undulator photon beam absorbers sustain high intensities ( S. Sharma)
    • Upto 600 mA for dipole fan, 300mA for undulator
  • Damping ring absorbers can be scaled from APS designs
summary
Summary
  • With the development of fast kickers “small” damping rings are a serious option for ILC.
  • Preliminary study of a 6 km, 5 Gev DR look promising.
  • Further optimization and next level study are planned using tools for light source improvement.

More information:

    • Studies Pertaining to a Small Damping Ring for the International Linear Collider,FERMILAB-TM-2272-AD-TD
    • ILC Damping Rings web site: http://awolski.lbl.gov/ILCDR/