1. Lattice design for CEPC
Geng Huiping
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

2. 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

3. Preliminary Conceptual Design Report

4. Writing job assigned for Pre-CDR4
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 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

5. Indico for CEPC AP meeting

6. Outline for each section prepared

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

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

9. 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
Energy acceptance (%)
2.7
L0/IP (1034cm-2s-1)
2.62
Llimit/IP (1034cm-2s-1)
1.26

10. 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 !

11. 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

12. 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

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

14. 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

15. 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.

16. 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…

17. 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….

18. Thank you !