Lattice design for CEPC Geng Huiping 2014 3

Lattice design for CEPC Geng Huiping 2014. 3. 19 Thanks to: Wang Dou, Guo Yuanyuan, Wang Na, Wang Yiwei, Xiao Ming, Peng Yuemei, Bai Sha, Su Feng, Xu Gang, Duan Zhe, Gao Jie, Qing

Outline • Overview of CEPC – Preparation for pre-CDR – Baseline parameters – Layout • Beam dynamics study for CEPC – Lattice – Dynamic aperture • Work to do • Summary

Preliminary Conceptual Design Report

Writing job assigned for Pre-CDR 4 4. 1 CEPC - accelerator physics Main parameters 4. 2 Lattice Geng Huiping, Wang Dou, Guo Yuanyuan, Wang Na, Wang Yiwei, Xiao Ming, Peng Yuemei, Bai Sha, Su Feng, Xu Gang , Duan Zhe, Gao Jie 4. 3 4. 4 4. 5 4. 6 4. 7 4. 8 IR and MDI Beam instability Beam-beam effects Synchrotron radiation Injection and beam dump Background Wang Dou, Geng Huiping, Wang Yiwei, Bai Sha, , Gao Jie Wang Na, Wang Yiwei Zhang Yuan, Guo Yuanyuan, Wang Dou, Xiao Ming, Gao Jie Ma Zhongjian, Geng Huiping Cui Xiaohao, Su Feng, Xu Gang Yue Teng 4. 9 Polarization Duan Zhe Guo Yuanyuan, Geng Huiping, Wang Dou, Xiao Ming, Gao Jie Ø 16 people@IHEP are working on the accelerator physics of CEPC Ø The lead author in each section will be responsible for the writing of that section with the help from the co-authors

Indico for CEPC AP meeting http: //indico. ihep. ac. cn/category. Display. py? categ. Id=237

Outline for each section prepared

Doc. DB system for documents management Ø Doc. DB will be used for documents management Ø Server has been ordered

Overview of CEPC Fundamental parameters: • Circumference: 50 km • Beam energy: 120 Ge. V • Synchrotron radiation power: 50 MW/beam • Luminosity: ~ 1034 cm-2 s-1

Baseline parameters of CEPC Parameter Value Energy (Ge. V) Circumference (km) Number of IPs SR loss/turn (Ge. V) Ne/bunch (1011) Bunch number Beam current (m. A) SR power /beam (MW) Partition number Je Longitudinal damping time(s) Nd (# of turns in damping time) 120 50 2 2. 96 3. 52 50 16. 9 50 2 0. 0067 40. 5 B 0 (T) Dipole length (m) Quadrupole length(m) Quadrupole strength(m-2) Bending radius (km) Momentum compaction (10 -4) 0. 065 20 0. 5 0. 042 6. 2 0. 4 Parameter � IP x/y (m) Emittance x/y (nm) Transverse IP (um) x/IP � y/IP VRF (GV) f. RF (GHz) vs Harmonic number � z (mm) �ng Lifetime[BS](h) Hourglass F Energy spread SR Energy spread BS Energy acceptance (%) L 0/IP (1034 cm-2 s-1) Llimit/IP (1034 cm-2 s-1) Value 0. 2/0. 001 6. 69/0. 033 36. 58/0. 18 0. 1 4. 2 0. 7 0. 13 116747 3 0. 42 1. 6 0. 59 0. 0013 0. 00014 2. 7 2. 62 1. 26

Sketch of CEPC In current design: • Circumference: 51. 6 km • 16*arcs: 48. 4 km • 14*short straight: 14*144 m=2. 0 km • 2*IPs: 2*576 m=1. 2 km Ø 8 RF cavities are uniformly distributed in every other straights. Ø The other 6 straights can be used for injection and dump. May subject to change !

Lattice of arc sections Ø Length of FODO cell: 48 m Ø Phase advance of FODO cells: 60/60 degrees Ø Dispersion suppressor on each side of every arc Ø Length: 96 m

Lattice of straight sections Ø Length straight: 144 m Ø Phase advance of FODO cells: 60/60 degrees Ø FFS is temporarily replaced by FODO cells Ø Length of each IP section: 576 m Ø Used for workpoint adjustment

Tune diagram of CEPC lattice Work point: (178. 73, 179. 12)

Chromatic correction The simplest method: ØOne sextupole next to each quadrupole in the arc section ØOne family of sextupoles are used MAD SAD AT

Dynamic aperture survey SAD AT PTC Ø Quite different results obtained from different codes. Ø But mainly shows the DA is small even for 1% energy spread. Ø Geometric aberrations too big? Will try new chromatic correction scheme.

Work to do Optimize parameters Optimize chromaticity correction scheme Study saw-tooth correction scheme Study pretzel scheme if one ring Iterations with results from other sections, especially beam-beam and FFS results • Many more work to do… • • •

Summary Ø Many work has been done to get ready for Pre-CDR Ø Regular meetings are held to discuss progress and issues in studies Ø Very preliminary beam dynamic study has been done with different codes Ø Bigger dynamic aperture is foreseen by using different chromaticity correction scheme Ø All results have to be double checked Ø Many work still need to be done….

Thank you !