CEPC IR Design
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CEPC IR DesignSha Bai, Yiwei Wang, Dou Wang, Ming Xiao, Jie Gao
TLEP and CEPC IR designs meeting
CEPC low power design1reduce operation costreduce AC power2reduce the Microwave system cost reduce the IP y until reach the low IP y , the parameters table shows several sub-mm yto low beta 350um1) Radiation power reduce AC power (offer the Microwave powerreduceklystron numbers reduce2) Beam power reduceloss of heat energy of beam in SC cavity reduce, AC power due to refrigerator reduce (Now Ring Higgs Factory power without this part31)+2) AC power reduced remarkably
CEPC design parameters*AC power for refrigerator is not included
Design challenge The IP reducechromatic effect increasethe design of Final focus will be more difficult
There is no experience of the IP low FFS design in Ring collider, refer to the low IR design in linear collider. But the emittance in Ring is much bigger than in the linear collider, higher order aberrations large, the correction will be more difficult.
Final Focus Design without chromaticity correction
Final Focus Design without chromaticity correctionFor y*=1mmIR final focus design: Vacuum chamber sizeH=48mm, V=9.4mmQuadrupole parameters
Length (m)strength (T/m)Aperture (mm)Pole strength (T)QD12.25132506.6QF21.5104505.2QD31.57.4500.37QF41.524501.2
Final Focus Design without chromaticity correctionFor y*=1mmIR final focus simple design:y*/y*linear = 3.4Remarkable Chromatic effectFor sub-mm y* final focus chromatic effect is more remarkablecorrection necessary.
L* (m)184.108.40.206.5IP x/y (m)0.2/0.0010.071/0.000480.056/0.000420.041/0.00035Emittance x/y (nm)14.6/0.0739.5/0.0359.1/0.0318.9/0.026Transverse IP (um)(linear)54/0.2725.9/0.1322.6/0.1119.2/0.096Transverse IP (um)(estimated)-/0.59-/0.542-/0.542-/0.540Transverse IP (um)(simulation)55.0/0.93
AberrationContribution to beam size(m^2)R332.51E-14R344.79E-14T3365.15E-13T3462.71E-13
Local-compact FFS designL*=3.5m
Local-compact final focus designy* much similar to the ILC IR design first we tried the local chromaticity correction scheme (ILC type final focus)
CEPCCEPCCEPCCEPCILC 500GeV baselineL* (m)220.127.116.11.53.5IP x/y (m)0.2/0.0010.071/0.000480.056/0.000420.041/0.000350.011/0.00048
Emittance x/y (nm)14.6/0.0739.5/0.0359.1/0.0318.9/0.0260.02/0.00008Energy spread (%)0.130.130.130.130.124/0.070(e-/e+)z (mm)18.104.22.168.20.3Transverse IP (um)54/0.2725.9/0.1322.7/0.1119.2/0.0960.474/0.006Lmax/IP (1034cm-2s-1)3.12.311.971.581.8
CEPC Final focus lattice Designy* =0.35mm15MWdesign:ILC type Final focus Vacuum chamber sizeH=190mm, V=23mmQuadrupole parametersx,max=10000m, y,max=50000m
L* (m)3.51IP x/y (m)0.041/0.00035Dx0.0082Emittance x/y (nm)8.9/0.026Energy spread (%)0.13z (mm)2.2Transverse IP (um)19.2/0.096Lmax/IP (1034cm-2s-1)1.58
Length (m)strength (T/m)Aperture (mm)Pole strength (T)QD02.20.1519011.5QF12.00.071905.48
Chromaticity correctionDue to the emittance much larger than ILChigh order aberration increase. T126, T122, T166, T346 and T324 are no longer the biggest ones to be corrected.Sextupoles strength optimizationreduce the aberrations.y*/y*linear = 15, far away from the aim, need optimization.x* increase.
L* (m)3.5IP x/y (m)0.041/0.00035Emittance x/y (nm)8.9/0.026Transverse IP (um)(linear)19.2/0.096Transverse IP (um)(no correction; estimated)-/1.25Transverse IP (um)(no correction; simulation)45.8/2.03Transverse IP (um)(with correction; simulation)59.8/1.33
Chromaticity correctionReducing the emittance makes final focus correction easierbut beam lifetime and luminosity will be reduced too.Keep the emittanceReduce the L* to makethe chromaticity smaller
Number of IPs11111Energy (GeV)120120120120120Circumference (km)5050505050SR loss/turn (GeV)2.962.962.962.964.61Ne/bunch (1012)0.790.380.330.280.29Bunch number2223211912Beam current (mA)16.98.456.765.073.38SR power /beam (MW)5025201515.6B0 (T)0.0650.0650.0650.0650.1Bending radius (km)22.214.171.124.23.98Momentum compaction (10-4)0.380.380.380.380.19IP x/y (m)0.2/0.0010.071/0.000480.056/0.000420.041/0.000350.07/0.00035Emittance x/y (nm)14.6/0.0739.5/0.0359.1/0.0318.9/0.0264.3/0.022Transverse IP (um)54/0.2725.9/0.1322.7/0.1119.2/0.09617.3/0.087x/IP0.1030.0760.0690.060.129y/IP0.1030.1030.1030.1030.129VRF (GV)66666.6f RF (MHz)704704704704659z (mm)126.96.36.199.22.2Energy spread (%)0.130.130.130.130.16Energy acceptance (%)55555BS (10-4)13.813.813.813.816.3n0.60.60.60.60.7BS (10-4)188.8.131.52.35.9Life time due to beamstrahlung (minute)303030303F (hour glass)0.680.480.450.410.41Lmax/IP (1034cm-2s-1)3.12.311.971.581.33AC power/two beam (MW) *2861431148689Luminosity gain (%)49596938
Local compact FFS designL*=1.5m
IP parameters (25MW, 1.5m)IP parametersBETX := 0.071;ALFX := 0;BETY := 0.00048;ALFY := 0;DX := 0;DPX := -0.00795452718; BLENG := 2.2E-3; !bunch length (m)ESPRD := 1.3E-3; !energy spread (1)EMITX := 9.5E-9;EMITY := 0.035E-9;D0->L = 1.5;
Refit IP to QF1Fit five variables :
QD0 lengthQF1 length Pole-tip strength of QD0Pole-tip strength of QF1Distance between QD0&QF1
Linear latticefit B1, B2 and B5 to obtain Dx=0 and Dpx=0 at exit of B5reverse the system, refit QMs to match and .
Chromaticitynatural chromaticity decreased (compared with L*=3.5m)
Reduce the length of BendWe are tring to reduce the length of the bends as the beam energy of CEPC is lower than the 500GeV ILC.
Local non-compact FFS design
Procedure & MethodThe CEPC design parameters : two cases of y=1mm and y=0.35mm.FFADA programMatching section, CCS, Final Doublet.Non-interlaced sextupoles
Thanks to Hector and Rogelio for helping me setting up the FFADA program !
IP y=1mmat IP:bx=0.2 mby=1 mmL*=3.5 m
Beta Function at IP vs momentumGood region of 0.4% in Dp/p is necessary for the core in beam distribution.
IP lowy=0.35mmat IP:bx=0.041 mby=0.35 mmL*=3.5 m
Beta Function at IP vs momentumOptical bandwidth needs optimization.
Conclusions and ProspectsFor sub-mm y* final focus design, chromatic effect is large, correction necessary.For the local-compact FFS design, due to the large emittance and low y at IP, the high order aberration obvious, we tried to reduce the L* to reduce the chromatic aberrations.Linear lattice design, reduce the bends, shorter length, MAPCLASS optimization for high order aberrations. For the local non-compact FFS design, using the non-interlaced sextupoles to reduce the third order kick, momentum bandwidth needs optimization.Tracking beam size, MAPCLASS optimization for high order aberrations, momentum bandwidth optimization, Oide effect, error analysis
Thank you !