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

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 Longer quadrupole in ARC: Lqf=Lqd=2.5m Longer quadrupole in IR: Lqd0=1.73m*1.25 (TBD)

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

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

Beam stay clear region and quadrupole strength