1. Update of Lattice Design for CEPC Main Ring
Yiwei Wang, Yuan Zhang, Chenghui Yu, Jie Gao
CEPC AP meeting, 15 SEP 2017

2. New lattice and DA:
bx*=0.36m
Longer sextupole in ARC: Lsd=1.2m, Lsf=0.6m
Finite length of sextupole in IR: Lhs=Lvs=0.3m, Lsdd=0.1m
Finite length of crab sextupole: Lcrab=1.0m
Reduce radiation effect due to quadrupole
Longer quadrupole in ARC: Lqf=Lqd=2.0*1.25m
Longer quadrupole in IR: Lqd0=1.73m*1.25, *2.0
Lower radiation due to quadrupoles (undergoing)

3. CEPC new parameter - Higgs
D. Wang
x*=1.18m (lattice)
Number of IPs 2
Energy (GeV)
120
Circumference (km)
100
SR loss/turn (GeV)
1.61
Half crossing angle (mrad)
16.5
Piwinski angle
2.28
Ne/bunch (1011)
0.968
Bunch number
420
Beam current (mA)
19.5
SR power /beam (MW)
31.4
Bending radius (km)
11.4
Momentum compaction (10-5)
1.15
IP x/y (m)
0.36/0.002
Emittance x/y (nm)
1.18/0.0036
Transverse IP (um)
20.6/0.085
x/y/IP
0.025/0.085
RF Phase (degree)
128
VRF (GV)
2.03
f RF (MHz) (harmonic)
650
Nature z (mm)
2.75
Total z (mm)
2.85
HOM power/cavity (kw)
0.42
Energy spread (%)
0.096
Energy acceptance (%)
1.1
Energy acceptance by RF (%)
1.98 n
0.19
Life time due to beamstrahlung_cal (minute) 63
F (hour glass)
0.93
Lmax/IP (1034cm-2s-1)
2.0

4. DA with damping vs damping+fluctuation
LQF=LQD=2.0 m
LQF=LQD=2.5 m x y

5. DA with damping vs damping+fluctuation
Longer QD0 to reduce DA reduction due to fluctuation
LQD0=1.73m -> 1.73m  1.25, 1.73m  2.0
Keep other region as former lattice as possible to exclude other affections
Some bugs will be fixed after further optimization of QD0 length
LQD0=1.73m  1.25

6. DA with damping vs damping+fluctuation
LQF=LQD=2.0 m
LQD0=1.73 m
LQF=LQD=2.0 m
LQD0=1.73 m  1.25 x y

7. DA with damping vs damping+fluctuation
LQF=LQD=2.0 m
LQD0=1.73 m
LQF=LQD=2.0 m
LQD0=1.73 m  2.0 x y

8. Next step
Check radiation effect due to all quadrupoles along the whole ring
seems possible to further increase DA by reduce synchrotron radiation due to the quadrupoles