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, Qin Qing

Outline Overview of CEPC Beam dynamics study for CEPC Work to do 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 CEPC - accelerator physics 4.1 Main parameters Guo Yuanyuan, Geng Huiping, Wang Dou, Xiao Ming, Gao Jie 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 IR and MDI Wang Dou, Geng Huiping, Wang Yiwei, Bai Sha, , Gao Jie 4.4 Beam instability Wang Na, Wang Yiwei 4.5 Beam-beam effects Zhang Yuan, Guo Yuanyuan, Wang Dou, Xiao Ming, Gao Jie 4.6 Synchrotron radiation Ma Zhongjian, Geng Huiping 4.7 Injection and beam dump Cui Xiaohao, Su Feng, Xu Gang 4.8 Background Yue Teng 4.9 Polarization Duan Zhe 16 people@IHEP are working on the accelerator physics of CEPC 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/categoryDisplay.py?categId=237

Outline for each section prepared

DocDB system for documents management DocDB will be used for documents management Server has been ordered

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

Baseline parameters of CEPC Value Energy (GeV) 120 Circumference (km) 50 Number of IPs 2 SR loss/turn (GeV) 2.96 Ne/bunch (1011) 3.52 Bunch number Beam current (mA) 16.9 SR power /beam (MW) Partition number Je Longitudinal damping time(s) 0.0067 Nd (# of turns in damping time) 40.5 B0 (T) 0.065 Dipole length (m) 20 Quadrupole length(m) 0.5 Quadrupole strength(m-2) 0.042 Bending radius (km) 6.2 Momentum compaction (10-4) 0.4 Parameter Value IP x/y (m) 0.2/0.001 Emittance x/y (nm) 6.69/0.033 Transverse IP (um) 36.58/0.18 x/IP 0.1 y/IP VRF (GV) 4.2 fRF (GHz) 0.7 vs 0.13 Harmonic number 116747 z (mm) 3 ng 0.42 Lifetime[BS](h) 1.6 Hourglass F 0.59 Energy spread SR 0.0013 Energy spread BS 0.00014 Energy acceptance (%) 2.7 L0/IP (1034cm-2s-1) 2.62 Llimit/IP (1034cm-2s-1) 1.26

Sketch of CEPC In current design: May subject to change ! Circumference: 51.6 km 16*arcs: 48.4km 14*short straight: 14*144m=2.0km 2*IPs:2*576m=1.2km 8 RF cavities are uniformly distributed in every other straights. The other 6 straights can be used for injection and dump. May subject to change !

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

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

Tune diagram of CEPC lattice Work point: (178.73, 179.12)

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

Dynamic aperture survey SAD AT PTC Quite different results obtained from different codes. But mainly shows the DA is small even for 1% energy spread. 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 Many work has been done to get ready for Pre-CDR Regular meetings are held to discuss progress and issues in studies Very preliminary beam dynamic study has been done with different codes Bigger dynamic aperture is foreseen by using different chromaticity correction scheme All results have to be double checked Many work still need to be done….

Thank you !