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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 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

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  1. 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

  2. 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

  3. APS, a 1 km, 7 GeV Ring at Work

  4. 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.

  5. Major Parameters of DRs and APS

  6. 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)

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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)

  12. 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.

  13. 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

  14. 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/

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