Overview of 6 km damping ring study
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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 l.jpg

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 l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
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 l.jpg
    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 l.jpg
    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 l.jpg
    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 l.jpg
    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 l.jpg
    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 l.jpg

    • 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/