Philip Bambade / LAL-Orsay Sha Bai / IHEP-Beijing Interaction point and machine-detector interface 1) highlights of recent developments for ee colliders ATF2 – SuperKEKB – CEPC 2) LAL-IHEP collaboration Philip Bambade / LAL-Orsay Sha Bai / IHEP-Beijing 9th FCPPL workshop IPHC-Strasbourg 30/3-1/4 2016
Collaborating teams LAL-Orsay IHEP SuperKEKB CEPC Philip Bambade – SuperKEKB & ATF2 Cécile Rimbault – SuperKEKB Viacheslav Kubytskyi – SuperKEKB & ATF2 Shan Liu – student/CSC XFEL@DESY Dima El Khechen – student/ED517 Renjun Yang – student/CSC Pang Chengguo – student/CSC (tbc) IHEP Jie Gao – CEPC Sha Bai – CEPC (+ ATF2) Dou Wang – CEPC (+ ATF2/ILC) Yiwei Wang – CEPC (+ CLIC/ILC + SuperKEKB) SuperKEKB CEPC Related collaborations: - KEK (S. Uehara, Y. Funakoshi et al.): luminosity monitoring&feedback for SuperKEKB - KEK (N. Terunuma, T. Tauchi et al.): ATF2 final focus prototype for linear collider - IPHC-Strasbourg (I. Ripp-Baudot et al.): characterize beam backgrounds in Belle-II - BINP (E. Levichev et al.): collaboration on CEPC design
LAL/France and IHEP/China collaborate since 2007 PhD Students : Sha BAI (2007-2010) ATF2 Shan LIU (2012-2015) ATF2 Renjun YANG (2015-2018) ATF2 Pang CHENGGUO tbc (2016-2019) SuperKEKB Publications : 1) In vacuum diamond sensor scanner for beam halo measurements in the beam line at the KEK Accelerator Test Facility, by S. Liu et al.: arXiv:1512.08024,submitted to NIMA (December 2015) 2) Study of alternative ILC final focus optical configurations, by D. Wang et al.: Nucl.Instrum.Meth. A781 (2015) 14-19 3) Analytical Estimate of ATF Beam Halo Distribution, by D. Wang et al.: Chinese Physics C 2014 Vol. 38(12): 127003 4) Experimental Validation of a Novel Compact Focusing Scheme for Future Energy-Frontier Linear Lepton Colliders, by G. White et al. (ATF2 Collaboration): Physical Review Letters 112, 034802 (2014) 5) Propagation of a beam halo in accelerator test facility 2 at KEK , by S. Bai et al.: Chinese Physics C 2013 Vol. 37(5): 057005 6) Mitigating the effects of higher order multipole fields in the magnets of the Accelerator Test Facility 2 at KEK, by S. Bai et al.: Chinese Physics C 2012 Vol. 36(8): 756-760 7) Simulation of beam size multiknobs correction at the Accelerator Test Facility 2 at KEK, by S. Bai et al.: Chinese Physics C 2011 Vol. 35(4): 397-401 8) First beam waist measurements in the final focus beam line at the KEK Accelerator Test Facility, by S. Bai et al.: Physical Review Special Topics - Accelerators and Beams 13, 092804 (2010) 9) Present status and first results of the final focus beam line at the KEK Accelerator Test Facility, by P. Bambade et al. (ATF Collaboration): Physical Review Special Topics - Accelerators and Beams 13, 042801 (2010) Conference reports : 18 Technical reports : 4
ATF2 final focus prototype for linear colliders see talk by Shan LIU
Measuring nanometre beam sizes at ATF2 37 nm vertical size Modulation of Compton scattered photon rate from beam interaction with laser interference fringe pattern Laser wavelength 532 nm
Vertical feedback stabilization of 2nd bunch Preliminary : y 41 nm smallest vertical beam size ever achieved Kano, Okugi, Kraljevic,…
Collimator for beam halo & background control Diamond Sensors x/y Beam size monitor Last bend magnet Transition foil (elastic part) Transition pipe Vacuum chamber 600 mm Fuster, Wallon,…
Beam halo & background control – first results Bremstrahlung background near IP Background rate beam size monitor collimator efficiency study Beam halo near IP Vertical halo symmetric cut Horizontal halo reduction (secondaries) GEANT4 [mm] Horizontal beam halo distribution [mm] Fuster, Yang,…
SuperKEKB asymmetrical very high luminosity B-meson factory
SuperKEKB / Belle-II Machine-Detector Interface Luminosity monitoring & tuning Control beam induced backgrounds 1) Phase 1 : 2016/Feb. Jun. - single beam commissioning, vac. scrubbing - no luminosity (no final focus), no detector 2) Phase 2 : 2017/Nov. 2018/Mar. - colliding beam commissioning, no vertex detector 3) Phase 3 : from 2018/autumn - full luminosity for physics running βy = 300 m d 300 m mitigates beam-beam and hour-glass effects… Lumi 40
Beam background at SuperKEKB At SuperKEKB with x 40 larger luminosity, beam background will also increase drastically Touschek scattering Beam-gas scattering Synchrotron radiation Radiative Bhabha event: emitted g Radiative Bhabha event: spent e+/e- 2-photon process event: e+e-e+e-e+e- etc… Beam-origin Luminosity dependent In this slide, I have listed up variety of possible beam background sources at SuperKEKB. Among these background sources, so-called “Touschek scattering” will be the most difficult one to cope with, which I will explain in more detail in the following slides. e- e+ Nakayama,…
Fast & slow variations at IP require feedback corrections Beam-beam deflection (SLC, KEKB) for fast vertical motion Luminosity feedback by “dithering” (PEP-II) for slower horiz. motion Luminosity tuning with optical knobs (SLC, FFTB, ATF2) to maintain small spot sizes ( time scales of hours ? ) Dy at IP= 5nm 1/10sy* BPM IP Dy at BPM= 1.3mm Vertical vibration 25-100 Hz Sampling (BPMs) 32 kHz 2f0 Horizontal motion few Hz Modulation freq. f0 77 Hz Sampling (lumi. meas.) 1 kHz minimize f0 output component Luminosity f0 x
Radiative Bhabha (“Compton”) process 250 mbarn (E > 1% Ebeam ) major background source from induced particle losses after IP use for luminosity monitoring Luminosity monitoring specs Relative measurements 10-3 in 1 ms over all bunches 10-3 in 1 s for each 2500 bunch 4ns (for nominal luminosity) Non luminosity scaling contamination < 1% (e.g. beam gas bremstrahlung and Touschek losses) Should also work for initial luminosity Macroscopic QED effect… Y. Funakoshi (KEK), background workshop, Feb. 2012
LER & HER measurement stations Recoil electron Outside g from positron from electron @ 30 m Recoil positron @ 11 m 2 diamonds + 1 Cherenkov + 1 Scintillator 2 diamonds + 1 Cherenkov + 1 Scintillator
SuperKEKB single beam commissioning 1st signals from beam gas bremstrahlung coincidence… HER diamond and Cherenkov… Injection noise… Coming soon : - beam particle loss analysis - studies w.r.t. beam conditions Uehara, Kubytskyi, El Khechen, Jehanno,… Signal distribution along 10 s revolution time…
CEPC High luminosity Higgs & Z boson factory Parameters and layout Machine Detector Interface Background Collimators Shielding Solenoid compensation Fast luminosity measurement & feedback What CEPC can learn from SuperKEKB
Advantage: Avoid pretzel orbit Accommodate more bunches at Z/W energy Reduce AC power with crab waist collision bypass (pp) bypass (pp)
Basic parameters for CEPC double ring（wangdou20160219） Pre-CDR H-high lumi. H-low power Z Number of IPs 2 Energy (GeV) 120 45.5 Circumference (km) 54 SR loss/turn (GeV) 3.1 2.96 0.062 Half crossing angle (mrad) 14.5 15 11.5 Piwinski angle 2.5 2.6 8.5 Ne/bunch (1011) 3.79 2.85 2.81 2.67 0.46 Bunch number 50 40 44 1100 Beam current (mA) 16.6 16.9 10.1 10.5 45.4 SR power /beam (MW) 51.7 30 31.2 2.8 Bending radius (km) 6.1 6.2 Momentum compaction (10-5) 3.4 3.0 2.2 3.5 IP x/y (m) 0.8/0.0012 0.306/0.0012 0.25/0.00136 0.22/0.001 0.268 /0.00124 0.08/0.001 Emittance x/y (nm) 6.12/0.018 3.34/0.01 2.45/0.0074 2.67/0.008 2.06 /0.0062 0.62/0.002 Transverse IP (um) 69.97/0.15 32/0.11 24.8/0.1 24.3/0.09 23.5/0.088 7/0.046 x/IP 0.118 0.04 0.03 0.032 0.005 y/IP 0.083 0.11 0.084 VRF (GV) 6.87 3.7 3.62 3.6 3.53 0.12 f RF (MHz) 650 Nature z (mm) 2.14 3.3 3.2 3.9 Total z (mm) 2.65 4.4 4.1 4.2 4.0 HOM power/cavity (kw) 1.5 1.3 0.99 Energy spread (%) 0.13 0.05 Energy acceptance (%) Energy acceptance by RF (%) 6 2.1 1.1 n 0.23 0.49 0.47 0.27 Life time due to beamstrahlung_cal (minute) 47 53 36 41 32 F (hour glass) 0.68 0.73 0.82 0.69 0.81 0.95 Lmax/IP (1034cm-2s-1) 2.04 2.97 2.03 2.01 3.61
MDI layout and issues : single local double ring Beam background Shielding design Collimator design SC magnet design Beam pipe Solenoid compensation Lumical & fast lumi measurement & feedback ……..
CEPC Background Synchrotron radiation background a) from the last bend magnet b) from the quadrupole in the IR Lost particles background a) radiation Bhabha scattering b) beamstrahlung Generator Geant4(Mokka) Analysis(Marlin) Accelerator Simulation
Proposed exchange & collaboration IHEP : Use CEPC simulation tool to evaluate beam losses at SuperKEKB benchmarking of simulation tool validation on real system LAL : Conceptual design of fast luminosity monitoring for CEPC apply experience from SuperKEKB Application to FCPPL for support: 1-2 visits each way for face to face discussions and exchanges