CEPC partial double ring scheme and crab-waist parameters

Transcription

1 HKUST Jocke Club Institute for Advanced Stud CEPC partial double ring scheme and crab-waist parameters Dou Wang, Jie Gao, Feng Su, Ming Xiao, Yuan Zhang, Jiuan Zhai, Yiwei Wang, Bai Sha, Huiping Geng, Tianjian Bian, Xiaohao Cui, Yuanuan Guo IAS Program on High Energ Phsics, Jan 18-1, 16. IAS, Hong Kong.

2 bpass (pp) Advantage: Avoid pretzel orbit Accommodate more bunches at Z/W energ Reduce AC power with crab waist collision bpass (pp)

3 Machine constraints / given parameters Energ E Circumference C N IP Beam power P β * Emittance coupling factor κ ε Bending radius ρ Piwinski angle Φ ξ enhancement b crab waist F l ~1.5 Energ acceptance (DA) Phase advance per cell (FODO)

4 Constraints for parameter choice Limit of Beam-beam tune shift ξ 845 Fl* π γen F : ξ enhancement b crab waist l IP Beam lifetime due to beamstrahlung U Ne α BS life time: 3 min.1η 3 σσ γr x z e V.I. Telnov Beamstrahlung energ spread HOM power per cavit Aδ /δ BS (A 3) P k( σ ) en I 1kw HOM z e b *J. Gao, emittance growth and beam lifetime limitations due to beam-beam effects in e+e- storage rings, Nucl. Instr. and methods A533(4)p

5 Parameter choice step 1 U I b ep U E ( GeV ) ρ( m) 4 3 δ γ C q J ε ρ Beam-beam limit: ξ 845 U π γen IP F l * F l : ξ enhancement b crab waist, ~ 1.5.

6 Parameter choice step ( r) L [ cm s ] ee ( GeV ) NbN ξ () ( cm) 1 34 * T s β e ξ 845 U π γen IP F l ( ) 1 34 L cm s r Fl β [ cm] [ ] [ ] [ ] E GeV I ma P MW b γn IP

7 Parameter choice step 3 BS life time: 3 min ξ: N σσ σσ x σ x α.1η 3 e x z γre N e 1+Φ πγ ξ r β e δ δ BS ( A 3) A πηαξ 5.77δβ 1+Φ γ ra N σσσ.πηαξ 1+Φ e 3 x z 3re β N σσσ 3δ γra e 3 x z.6re σ σ rσx, ε β ε * σ x εx, βx κ ε ε x ε x 3 3 µ 1 4 µ Cqγϕ 1 sin + sin µ µ 8J x sin cos ϕ µ-- phase advance/cell, ϕ-- bending angle/cell. Estimate : α p ϕ 1 1 sin 1 ( )( ) µ

8 Parameter choice step 4 N πγξ 1+Φ e σσ x reβ N b IT b en e σ z 3γ rn e e.1ηασ σ z Φ σ x x tgθ h θ h.1ηασ xφ Arctg 3γ rn e e

9 Parameter choice step 5 Effective bunch length: overlap area of colliding bunches σ x σ zeff sinθ h Hour glass effect: F h β β β exp K πσ σ zeff zeff σ zeff L LF h

10 Parameter choice step 6 U ev sinφ rf s A πe α σ σ Rδ p z z 1+ A frf TeV rf cosφs V rf, φ s Energ acceptance from RF: η RF U 1 q 1 arccos( ) q πα p frf TE q U ev rf

11 Parameter choice step 7 Beam lifetime due to radiative Bhabha scattering τ bhabha Ib eln σ Beam lifetime due to Beamstrahlung IP ee f 5 ( σ ee cm ) τ BS π R c 6πrγe u e α ησ z * HOM power per cavit P k( σ ) en I 1kw HOM z e b HOM loss factor: 1.8 k( σ z ) V / pc σ z.65 *V.I. Telnov, "Issues with current designs for e+e- and gammagamma colliders, PoS Photon13 (13) 7.

12 Primar parameter for CEPC double ring Pre-CDR H-high lumi. H-low power Z Number of IPs Energ (GeV) Circumference (km) SR loss/turn (GeV) Half crossing angle (mrad) Piwinski angle N e /bunch (1 11 ) Bunch number Beam current (ma) SR power /beam (MW) Bending radius (km) Momentum compaction (1-5 ) β IP x/ (m).8/.1.36/.1.58/.16./.1.115/.1.3/.1 Emittance x/ (nm) 6.1/ /.1.3/.58.67/.8.56/ /.69 Transverse σ IP (um) 69.97/.15 3/ / / / /.83 ξ x /IP ξ /IP V RF (GV) f RF (MHz) Nature σ z (mm) Total σ z (mm) HOM power/cavit (kw) Energ spread (%) Energ acceptance (%) Energ acceptance b RF (%) n γ Life time due to beamstrahlung_cal (minute) F (hour glass) L max /IP (1 34 cm - s -1 )

13 CEPC single ring parameter Pre-CDR H Low-HOM Number of IPs Energ (GeV) Circumference (km) SR loss/turn (GeV) N e /bunch (1 11 ) Bunch number Beam current (ma) SR power /beam (MW) Bending radius (km) Momentum compaction (1-5 ) β IP x/ (m).8/.1.6/.1.4/.1 Emittance x/ (nm) 6.1/ /.18.9/.18 Transverse σ IP (um) 69.97/ / /.15 ξ x /IP ξ /IP V RF (GV) f RF (MHz) Nature σ z (mm) Total σ z (mm) HOM power/cavit (kw) Energ spread (%) Energ acceptance (%) 1.5 Energ acceptance b RF (%) n γ Life time due to beamstrahlung_cal (minute) F (hour glass) L max /IP (1 34 cm - s -1 ) Z

14 CEPC Partial Double Ring Lattice

15 Double ring FFS design with crab sextupoles Betax.8m Beta.3m Khs3.4 m -3 Kvs-16 m -3 IP Crab sextupole L*1.5m L(QD).91m, G(QD)-3T/m L(QF1).74m, G(QF1)16T/m L 4m Critical energ: Ec1 kev Dipole strength: B.1 T As Oide said, the second FFS sextupoles of the CCS-Y section can work as the crab sextupoles, if their strengths and phases to the IP are properl chosen.

16 Crab sextupole strength The crab sextupole should be placed on both sides of the IP in phase with the IP in the horizontal plane and at π/ in the vertical one. ϕ x π, ϕ.5π K * 1 1 β 7.5 x m high lumi * θββ βx 9.7 m low power

17 New FFS design Ec1keV EckeV Khs8. m -3 Kvs8 m -3 L*1.5m L(QD)1.3m, G(QD)-T/m L(QF1).73m, G(QF1)16T/m

18 Combine with partial double ring lattice FFS orbit

19 Arc redesign-lower emittance Length of FODO cell: 47.m Phase advance of FODO cells: 6/6 degrees Emittance: 7.9nm, αp5.38e-5 Bunch length:.3mm Length of FODO cell: 37.5m Phase advance of FODO cells: 6/6 degrees Emittance: 4.3nm, αp.5e-5 Bunch length: 3.3mm

20 Arc redesign-ultra low emittance Length of FODO cell: 37.5m Phase advance of FODO cells: 9/6 degrees Emittance:.3nm, αp1.7e-5 Bunch length: 3.3mm B B Dispersion supressor: Angle(BDIS1) E-3 Angle(BDIS) E-4 Angle(B).7393E-3 BDIS1 BDIS

21 summar A consistent calculation method for CEPC parameter choice with carb waist scheme has been created. Based on partial double ring scheme, we can get higher luminosit (+5%) keeping Pre-CDR beam power or to reduce the beam power (3 MW) keeping same luminosit. Based on partial double ring scheme, we get a set of Z parameter with 1.5*1 34 cm - s -1 luminosit using 11 bunches. CEPC single ring scheme is neither eas to reduce cavit HOM power for Higgs nor to accommodate more bunches for Z. FFS with crab sextupoles and lower emittance arc has been designed. DA optimization is undergoing.

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