1. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 1 Design for the DR RF cavities and impedance issues Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory February 19, 2007 KEK, Japan

2. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 2 Outline ILC Damping Ring RF RequirementsILC Damping Ring RF Requirements RF Cavity ChoicesRF Cavity Choices ─Superconducting cavity ─Existing successful SC RF cavities that could be used Cornell 500-MHz single cell cavityCornell 500-MHz single cell cavity KEK 500-MHz single cell cavityKEK 500-MHz single cell cavity What has been done so farWhat has been done so far ─Scaled Cornell 500-MHz cavity design to 650-MHz Short range wakefield simulations (SLAC)Short range wakefield simulations (SLAC) Future plansFuture plans SummarySummary

3. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 3 ILC Damping Ring RF Requirements ILC DRs Main Parameters* * M. Venturini, et al, PAC-2007 Proceedings

4. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 4 RF Cavity Choices Existing (successful) SC RF cavity designs Cornell 500-MHz cavity: WG coupler and HOM dampedCornell 500-MHz cavity: WG coupler and HOM damped ─Installed and demonstrated successfullyin CESR-B, 2 nd generation light source (greater than 500-mA) ─Installed and demonstrated successfully in CESR-B, 2 nd generation light source (greater than 500-mA) ─ Very heavy HOM damping ─ Used by other light sources Diamond LS (500-mA), CL (300-mA), SSRC (500-mA) and SSRF (300-mA) HOM Damping

5. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 5 RF Cavity Choices (cont’d) Coax coupler and HOM Damping

6. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 6 RF Cavity Choices (cont’d) KEK 500-MHz (scaled from 509-MHz) SC Cavity DesignKEK 500-MHz (scaled from 509-MHz) SC Cavity Design ─Successfully used at KEK-B and BEPC-II at IHEP, China

7. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 7 KEK-B SC Cavity Achievements at KEK-B (RF frequency = 509-MHz)

8. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 8 Niobium on Copper Cavity One cryomodule: One cryomodule: - Two single-cell Nb-on - Two single-cell Nb-on copper cavities copper cavities - Frequency: 352 MHz - Frequency: 352 MHz - Beam Energy: 2.5 GeV - Beam Energy: 2.5 GeV - Beam current: 500 mA - Beam current: 500 mA 352-MHz Nb-on-Copper RF System Soleil Light Source: Possible candidate, but no plan yet to explore further at the moment

9. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 9 Turn-Key System from Industry Available as a turn-key RF system (based on Cornell design) for light sources (ACCEL)Available as a turn-key RF system (based on Cornell design) for light sources (ACCEL) ─Cryomodule + LLRF controls

10. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 10 What Have We Done So Far SLAC has scaled Cornell 500- MHz design to 650-MHzSLAC has scaled Cornell 500- MHz design to 650-MHz ─Short range wakefield simulations using ABCI (Z. Li) ─No long range (narrow band) wakefield simulations yet I found: ILC-INF-003 NotesI found: ILC-INF-003 Notes

11. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 11 What Have We Done So Far (cont’d) From the ILC-INF-003 Notes

12. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 12 Future Plans Regardless of recent budget newsRegardless of recent budget news For the scaled 650-MHz SC cavity design from Cornell 500-MHz cavity:For the scaled 650-MHz SC cavity design from Cornell 500-MHz cavity: ─Continue the scaled 650-MHz RF cavity design in collaboration with SLAC ─Re-visit the scaled 650-MHz design, check if there is a need for geometry modifications: Beam pipeBeam pipe RF power couplerRF power coupler HOM dampingHOM damping ─Complete long range wakefield simulations  Impedance spectra with HOM damping ─Confirm the impedance meets ILS DR requirements (needs to impedance threshold for the DRs) ─Define RF system requirements: RF power + cryogenics + …

13. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 13 Future Plans In parallel with the work for the scaled Cornell cavityIn parallel with the work for the scaled Cornell cavity ─Lunch collaboration with BEPC-II team at IHEP, Beijing to scale the KEK cavity to 650-MHz IHEP plans to build a spare 500-MHz SC cavity (based on KEK cavity) for BEPC-II from funding from Chinese Academy of ScienceIHEP plans to build a spare 500-MHz SC cavity (based on KEK cavity) for BEPC-II from funding from Chinese Academy of Science Available resources: man power + SRF research facility at IHEPAvailable resources: man power + SRF research facility at IHEP Already received very positive response from IHEP (Drs. J. Wang, J. Gao, W. Pan and G. Wang)Already received very positive response from IHEP (Drs. J. Wang, J. Gao, W. Pan and G. Wang) ─In addition to repeat the proposed work in the previous slide, IHEP could be a potential institute of the cavity prototype for ILC DRs Exploring engineering challenges for the cavity and cryomoduleExploring engineering challenges for the cavity and cryomodule Significant savings (potentially)Significant savings (potentially)

14. ILC DR RF Cavity – D. Li DR Workshop, KEK, Japan 14 Summary Possible SC RF cavity choices for ILC DRsPossible SC RF cavity choices for ILC DRs Plans for futurePlans for future ─Collaboration with SLAC and other institutes ─Collaboration with IHEP, China We look forward to working with ILC DR collaborators and making more contributions, but (honestly) nothing has been done yet at this moment, the recent ILC budget news does not look like for us to make a rapid progress in near futureWe look forward to working with ILC DR collaborators and making more contributions, but (honestly) nothing has been done yet at this moment, the recent ILC budget news does not look like for us to make a rapid progress in near future