CEPC Partial Double Ring Parameter Update
The CEPC Partial Double Ring Layout features advantages like accommodating more bunches at Z/W energy, reducing AC power with crab waist collision, and unique machine constraints based on given parameters. The provided parameter choices and updates aim to optimize beam-beam effects, emittance growth, beam lifetime limitations, and other crucial factors for efficient operation of the particle accelerator.
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CEPC Partial Double Ring Parameter Update Dou Wang, Jiyuan Zhai, Feng Su, Yuan Zhang, Yiwei Wang, Bai Sha, Huiping Geng, Tianjian Bian,
CEPC Partial Double Ring Layout RF IP1_ee RF 3Km 1/2RF Advantage: Avoid pretzel orbit 1/2RF IP4_pp Accommodate more bunches at Z/W energy Reduce AC power with crab waist collision IP2_pp 1/2RF 1/2RF C=54710.4m RF RF IP3_ee IP1_ee/IP3_ee, 3Km IP2_pp/IP4_pp, 1132.8m 4Straights, 849.6m SU Feng 4Long ARC, 120*FODO, 5852.8m 2015.10.12 4Short ARC, 100*FODO, 4908.8m
Machine constraints / given parameters Energy E0 Circumference C0 NIP Beam power P0 y* R= y/ x Emittance coupling factor Bending radius Piwinski angle luminosity enhancement by crab waist Fl~1.5 Phase advance per cell (FODO)
Parameter choice step 1 4 0 ( ) E GeV = 3 88.5 10 U 0 ( ) m eP U = 0 I b 0 C J = q 0 Beam-beam limit: 2845 2 U E N Fl: y enhancement by crab waist = * 0 F y l 2 0 IP *J. Gao, emittance growth and beam lifetime limitations due to beam-beam effects in e+e- storage rings, Nucl. Instr. and methods A533 2004 p. 270-274.
Parameter choice step 2 ( ( ) ) ( eE GeV N N T s ( ) = + 2 1 34 [ ] 2.17 10 1 0 b e L cm s r 0 y * y ) cm 0 2845 2 U E N = 0 F y l 2 0 IP E GeV I mA P MW N 1 ( ) = 0.7 10 + 0 0 b 2 1 34 1 L cm s r 0 cm y IP
Parameter choice step 3 N 0.1 e BS life time: 30 min 2 3 r + 2 0.2 1 2 e N x z e y = 2 r N 2 x 3 3 r = y: e y z e y y + 2 1 e y x y 2 e 3 r N = ( 3) 0 = A 0 3 BS 2.6 rA A x y z e 2 y = = , r 5.77 y x y 0 y = y x 2 x + 2 1 rA y = = * x , y x x 3 4 1 60 + 2 3 2 4 1 sin sin C -- phase advance/cell, -- bending angle/cell. q 2 2 = x 3 8 sin cos J x 2 2 1 1 = 2 ( ) ( 2 ) Estimate : p 12 2 sin 2
Parameter choice step 4 + 2 2 1 I T eN = N 0 b y r = N b e x y e e y r N 2 3 0.1 = e e z 2 x 0.1 3 x = Arctg h r N 2 = tg z e e h x
Parameter choice step 5 Effective bunch length: overlap area of colliding bunches = x zeff sin h 2 y 2 y y = exp F K Hour glass effect: 0 h 2 zeff 2 zeff 2 2 zeff = L L F 0 h
Parameter choice step 6 = sin U eV 0 rf s Vrf, s 2 E A + 0 p = = R 0 0 z z 1 cos A f T eV 0 rf rf s Energy acceptance from RF: eV U 2 1 q U f T E rf = 1 arccos( ) = 2 0 q q RF 0 0 0 p rf
Parameter choice step 7 Loss factor 1.8 = ( ) / k V pC z z 0.00265 HOM power per cavity = ( ) 2 1 HOM P k eN I kw z e b
Primary parameter design Pre-CDR high lumi. low power Z Number of IPs Energy (GeV) Circumference (km) SR loss/turn (GeV) Half crossing angle (mrad) Piwinski angle Ne/bunch (1011) Bunch number Beam current (mA) SR power /beam (MW) Bending radius (km) Momentum compaction (10-5) IPx/y (m) Emittance x/y (nm) Transverse IP(um) x/IP y/IP VRF(GV) fRF(MHz) Nature z(mm) Total z(mm) HOM power/cavity (kw) Energy spread (%) Energy acceptance (%) Energy acceptance by RF (%) n Life time due to beamstrahlung_cal (minute) F (hour glass) Lmax/IP (1034cm-2s-1) 2 2 2 2 120 54 3.1 0 0 3.79 50 16.6 51.7 6.1 3.4 120 54 2.96 120 54 2.96 45.5 54 0.062 16.5 2.6 0.37 1100 36.2 2.2 6.1 5.4 0.3/0.001 1.18/0.0069 18.8/0.083 0.02 0.042 0.28 650 3.0 3.0 0.73 0.05 14.5 2 3.79 50 16.9 50 6.2 3.0 5.2 2 1.2 158 16.9 50 6.2 2.8 11.5 2 2.81 40 10.1 30 6.2 2.6 4.3 2 1.0 114 10.1 30 6.2 2.5 0.8/0.0012 6.12/0.018 69.97/0.15 0.118 0.083 6.87 650 2.14 2.65 3.6 0.13 2 6 0.23 47 0.306/0.0012 3.34/0.01 32/0.11 0.04 0.11 3.7 650 3.3 4.4 3.3 0.13 2 2.2 0.49 53 0.036/0.0012 3.07/0.0093 10.5/0.1 0.015 0.11 3.9 650 3.0 4.0 0.95 0.13 2 2.6 0.46 32 0.22/0.001 2.67/0.008 24.3/0.09 0.04 0.11 3.6 650 3.2 4.2 1.5 0.13 2 2.2 0.47 41 0.03/0.001 2.56/0.0078 8.8/0.088 0.015 0.11 3.7 650 3.0 4.0 0.47 0.13 2 2.4 0.46 32 2.0 0.08 0.68 2.04 0.73 2.97 0.75 3.07 0.69 2.03 0.7 2.08 0.67 1.01
Arc redesign-lower emittance Length of FODO cell: 47.2m Phase advance of FODO cells: 60/60 degrees Emittance: 7.9nm, p=5.38E-5 Bunch length: 2.3mm Length of FODO cell: 37.5m Phase advance of FODO cells: 60/60 degrees Emittance: 4.3nm , p=2.25E-5 Bunch length: 3.3mm
Arc redesign-ultra low emittance Length of FODO cell: 37.5m Phase advance of FODO cells: 90/60 degrees Emittance: 2.3nm, p=1.07E-5 Bunch length: 3.3mm Dispersion supressor: Angle(BDIS1)=3.583724E-03 Angle(BDIS2)=-8.598108E-04 Angle(B0)=2.723923E-03 BDIS1 BDIS2 B0 B0
summary CEPC AP group and RF group has collaborated to give a more realizable parameter considering cavity HOM power. Based on crab waist scheme, we get a set of Z parameter with 1.0*1034cm-2s-1 luminosity using 1100 bunch. Higgs s parameters have been updated to reduce the cavity HOM power under 1kw. Further improvement is undergoing to make same crossing angle as Z parameter.
