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ILC Damping Ring Alternative Lattice Design （ Modified FODO ） **

ILC Damping Ring Alternative Lattice Design （ Modified FODO ） **. Yi-Peng Sun *,1,2 , Jie Gao 1 , Zhi-Yu Guo 2 Wei-Shi Wan 3 1 Institute of High Energy Physics, CAS, Beijing 2 State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 3 LBNL, USA

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ILC Damping Ring Alternative Lattice Design （ Modified FODO ） **

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  1. ILC Damping Ring Alternative Lattice Design（Modified FODO）** Yi-Peng Sun*,1,2, Jie Gao1 , Zhi-Yu Guo2 Wei-Shi Wan3 1 Institute of High Energy Physics, CAS, Beijing 2 State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 3 LBNL, USA CCAST ILC Accelerator Workshop, IHEP, Beijing 6 November, 2007

  2. Layout of ILC

  3. Main timeline

  4. Ilc dr alternative lattice design goals • Smaller number quadrupoles and sextupoles used (roughly two thirds), and lower cost. • Freely tunable momentum compaction factor in the range between 2×10-4 and 6×10-4. • Good dynamic aperture. • Simpler layout, with only two wiggler sections and cryogenics shaft.

  5. layout 4 arc sections. 4 straight sections, one for injection, one for extraction, and the other two for RF/wiggler. Two shafts in all and no TL. Beam is counter-rotating.

  6. Considerations for the arc cell • Scan some arc cell parameters. • Arc cell number: from 120 to 240. • Arc cell length: from 20 m to 40 m. • The short drift length: from 1 m to 3 m. To get proper dispersion and beta functions at the sextupole location in a cell, suitable maximum beta function (less than 55 m, constrained by vacuum chamber), and freely tunable alpha with different arc cell phase advance. At last, we select the arc cell length to be 29.4 m, and the arc cell number to be 184.

  7. Comparison with ocs8

  8. Arc cell design Left: 60/60cell, corresponding to 6×10-4alpha Left: 90/90cell, corresponding to 2×10-4alpha

  9. Dispersion suppressor design Add one arc cell after the last standard arc cell and modify the bending angle of these two cells according to the phase advance. The aim is to have undisturbed TWISS parameters in the dispersion suppressor.

  10. Injection/extraction design 2 septums and 21 stripline kickers (lumped kickers) Uses two periodic cells, with the total horizontal phase advance matched to be 180 degree

  11. Chicane Adjustment of one Chicane: 10-6 adjustable 4 Chicane Emittance +9.2％

  12. 6×10-4momentum compaction Dispersion suppressor Total ring 60/60 cell, 6×10-4momentum compaction

  13. 4×10-4momentum compaction Dispersion suppressor Total ring 72/72 cell, 4×10-4momentum compaction

  14. 2×10-4momentum compaction Dispersion suppressor Total ring 90/90 cell, 2×10-4momentum compaction

  15. Total parameters of three critical modes

  16. Chromaticity correction The chromaticity corrected to (0.3,0.31). The tune variation with momentum spread ±1% is ~1×10-4

  17. High order magnets errors * Sys: system error; Ran: random error

  18. Dynamic aperture 6×10-4 alpha case Left: no errors; Right: with high order magnets errors

  19. Dynamic aperture 4×10-4 alpha case Left: no errors; Right: with high order magnets errors

  20. Dynamic aperture 2×10-4 alpha case Left: no errors; Right: with high order magnets errors

  21. Comparison with ocs8 (PAC07) 4×10-4 momentum compaction mode, on momentum particles, with errors; Left: OCS8 (PAC07), Right: FODO-4

  22. FMA optimization results FMA is used to optimize the lattice and the DA. The optimized result for 2×10-4 momentum compaction mode

  23. With harmonic sextupoles 2×10-4 momentum compaction mode, with 3 group harmonic sextupoles Left: no errors; Right: with high order magnets errors

  24. SCAN FOR THE HARMONIC SEXTUPOLES AND TUNES The full scan is still on-going now.

  25. others Touschek lifetime: 4×10-4 momentum compaction mode. Energy acceptance 1.48%, bunch population 2×1010, Touschek lifetime is 160minutes

  26. Several slides from Andy Wolski on Fermi GDE Meetings.

  27. Possible “alternative” FODO lattice extraction injection Yi-Peng Sun (IHEP) Jie Gao (IHEP)

  28. Possible “alternative” FODO lattice • Potential advantages of the FODO alternative include: • improved flexibility, from the ability to vary the momentum compaction factor (can play off bunch length against instability thresholds); • improved performance, from increased dynamic aperture; • reduced cost, from reduced number of magnets. • The OCS8 lattice is more mature, and the engineering design studies are more likely to proceed smoothly if based on this lattice. • A systematic comparison is needed to decide whether the potential benefits of the FODO lattice could be realised in practice. • Comparative studies of the OCS8 and FODO lattice are planned, and a decision on the lattice will be made by the end of 2007.

  29. Acknowledgement • Thanks to A. Xiao and L. Emery et al. in ANL who designed the RF/wiggler sections. • Many thanks to Prof. M. Zisman for his kind suggestions and help. Also thanks Prof. Cai of SLAC for his help.

  30. Thanks for your attention.

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