1. LAL-IHEP collaboration on the linear collider final focus & ATF2 prototype Philip Bambade Laboratoire de l’Accélérateur Linéaire Université Paris 11, Orsay, France 6 th FCPPL Workshop, Nanjing, China 27-29 March 2013 On behalf of: LAL: BLANCO Oscar ( PhD ) LIU Shan ( PhD, 3-year FCPPL-CSC grant ) IHEP: BAI Sha ( staff, co-directed LAL-IHEP PhD & Eiffel grant in the past ) GAO Jie ( prof., ILC group leader, LAL staff in the past ) WANG Dou ( staff ) WANG Yi Wei ( PhD, 3-month at LAL in 2012/13 with French Embassy support ) NSFC contract n° 11175192 IN2P3 support ANR & LABEX P2IO grants

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3. ATF & ATF2 R&D for linear colliders

4. Parameters ATF2ILCCLIC Beam Energy [GeV]1.32501500 L* [m]13.5 - 4.53.5  x/y [m.rad] 5E-6 / 3E-81E-5 / 4E-86.6E-7 / 2E-8 IP  x/y [mm] 4 / 0.121 / 0.46.9 / 0.07 IP  ’ [rad] 0.140.00940.00144  E [%] ~ 0.1 ~ 0.3 Chromaticity ~  / L* ~ 1E4 ~ 5E4 Number of bunches1-3 (goal 1)~ 3000312 Number of bunches3-30 (goal 2)~ 3000312 Bunch population1-2E102E103.7E9 IP  y [nm] 375.70.7 scaled ILC FFS start point of CLIC FFS ATF2 = concept of local compact chromaticity correction Beam control  trade-off Linac tech. & sources

5. Main LC beam delivery issues addressed by ATF / ATF2 Beam instrumentation Stabilization 4+1 dim. beam tuning & control for small IP spot Halo control - nm-level position - profile (x, y, tilt) - passive / active mechanical stabilization - beam / vibration measurement based feed-back/forward - emittance minimization via radiation damping - mitigation of 1 st, 2 nd and 3 rd order optical aberrations - convergence time  dynamical errors (sismic & thermal effect) - modeling, generation, propagation, monitoring… - collimation (physical, optics)  validate concept(s), develop, practice, train,…

6. ATF / ATF2 Goals  Very small damping ring vertical emittance - from ̴ 10 pm  4 pm (achieved !)  1-2 pm  Small vertical beam size “goal 1” - achieve  y ̴ 37 nm (cf. 5 / 1 nm in ILC / CLIC) - validate “compact local chromaticity correction”  Stabilization of beam center “goal 2” - down to ̴ 2nm - bunch-to-bunch feedback ( ̴ 300 ns, for ILC)  R&D on nanometer resolution instrumentation  Train young accelerator scientists on “real system” - maintain expertise by practicing operation  open & unique facility

7.   FCPPL FJPPL FKPPL

8. Installation of quadrupoles contributed by IHEP (China) in January 2008

10. First measurements of 70 nm vertical beam sizes in December 2012  confirmed repeatedly in 2013 ! σ y = 72.8 + 5.4 - 4.7 nm Modulation of Compton scattered photon rate resulting interaction with interference fringe pattern Nominal parameters: N = 10 +10 σ y = 37 nm 0.8e9 < N < 1.2e9

11. LAL-IHEP collaboration topics 1)Beam halo generation, propagation, collimation and measurements in ATF/ATF2 2)Development and implementation of mono-crystalline CVD diamond sensors for beam halo and Compton recoil electron measurements after the IP of ATF2 3)Orthogonality of interaction point waist corrections in the presence of σ 13 and σ 24 correlations and tilts of the interference fringe pattern 4)New simplified Final Focus optics design concept for ILC Presentation & discussion sessions in Nanjing - Thursday 4-6 pm - Saturday 9-12 am Thank you, Prof. Ming Qi !

12. Beam halo and BSM background issues post-IP bend magnet vertical gap final doublet beam pipe chromatic correction c-band / ref. BPMs Halo intercepted on GEANT4 (simplified conditions) under study…

13. ATF2 operation & instrumentation R&D DR extraction setup, stability Match optics into FF buffer section for input errors 2 nd order telescope fine tuning of local errors

14. Halo measurement at old ATF extraction line beam core (<3  ) is well approximated by a Gaussian. Beam tail (<3  ) deviate from the center Gaussian-like distribution T. Suehara et al., “Design of a Nanometer Beam Size Monitor for ATF2”, arXiv:0810.5467v1

15. Analytic calculation of halo distributions in X, Y and energy deviations from beam gas scattering Plan for 2013: 1)Calculation for multiple intra-beam Coulomb scattering 2)Monte-Carlo simulation (coll. Theo Demma) 3)Measurement program in ATF2 diagnostic section Dou WANG (IHEP) ( preliminary )

16. Shan LIU (LAL)

17. GEANT4 I.Khvastunov

18. Plan for 2013: install 1 st prototype @ ATF2 at year end

19. IP BSM fringe tilt increases measured σ y Sha BAI (IHEP) Proposed diagnosis measuring σ y as function of horizontal waist position (  x scan)

20. Orthogonality of α x scan must be good enough BX10BY1 optics vs BX2p5BY1 optics Due the slight breaking of orthogonality over the range of the  x scan, only tilt angles Ɵ > 2 mrad can be diagnosed by this method

21. Horizontal waist scan during continuous “goal 1” tuning in December 2012 Some dependence on  x scan seen  beam or fringe tilt ? Effect consistent with Ɵ ≈ 10 mrad tilt Glen WHITE (SLAC) Plan for 2013: measure more systematically, especially after IPBSM laser path adjustments – Finalise study impact on linear optics IP tuning

22. Chromatic correction concentrated on the vertical plane enlarged β x *=45mm, variable β y * –choose β x *=45mm: as without chromatic correction, σ x * minimized –with chromatic correction mainly in the vertical plane (green line): σ y * minimized when β y *= 0.08mm –σ y *=0.4∙σ y_nom * ( σ x *=3∙σ x_nom * ) –Luminosity recovery seems possible and there’s room for optimization. 22 Yiwei Wang (IHEP) Advantages: -5  2 sextupoles leads to shorter and easier to tune FFS -less beamstrahlung Limitations: -only for small energy spread -shorter bunch length needed to mitigate hour glass effect On-going: -reduce chromaticity redesigning linear optics -stronger bending to reduce sextupole strengths -use smaller emittances & bunch ILC length σyσy βyβy

23. Request for FCPPL support in 2013 Conclusion & prospects ATF2 is making good strong progress in 2012, after recovering form the earthquake The 30 degree mode of “Shintake” monitor is now validated Collaboration with China (IHEP,…) is continuing building on the FCPPL initial support THANK YOU ! ATF2 : first measurements of 70 nm vertical beam sizes ! Building on initial FCPPL support in 2007, a renewed and deepened collaboration between IHEP and LAL is developing to work on several topics relevant to the final focus of future linear colliders Already several new and promising results in 2013.  stay tuned for further progress in 2013 and 2014 !

24. Selected publications and reports P. Bambade (LAL) et al., Present status and first results of the final focus beam line at the KEK Accelerator Test Facility, PRSTAB 13, 042801 (2010) S. Bai (IHEP) et al., First beam waist measurements in the final focus beam line at the KEK Accelerator Test Facility, PRSTAB 13, 092804 (2010) S. Bai (IHEP) et al., Simulation of beam size multiknobs correction at Accelerator Test Facility 2 at KEK, Chinese Phys. C 2011 Vol.35(4):397-401 S. Bai (IHEP) et al., Mitigating the effects of higher order multipole fields in the magnets of ATF2, Chinese Phys. C 2012 Vol.36(8):756-760 Optical configurations with variable beta* at different IP locations in ATF2, by S. Bai, P. Bambade: ATF-08-05, LAL/RT-08-10 Linear Collider Test Facility: Twiss Parameter Analysis at the IP/Post-IP location of the ATF2 beam line, by B. Bolzon et al.: THPD077.PDF, Presented at the 1st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23-28 May 2010 ATF2 ultra-low IP betas proposal, by R. Tomas et al.: LAL-RT-09-11, Presented at the 23rd Particle Accelerator Conference (PAC09), Vancouver, Canada, 4-8 May 2009 Linear Collider Test Facility: Twiss Parameter Analysis at the IP/Post-IP location of the ATF2 beam line, by B. Bolzon et al.: THPD077.PDF, Presented at the 1st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23-28 May 2010 Simulation of Multiknobs Correction at ATF2, by S. Bai et al.: THPD096.PDF, Presented at the 1st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23-28 May 2010 Waist corrections at the interaction point of ATF2 in the presence of IPBSM fringe rotations and input BPM sigma13, sigma24, by S. Bai et al.: TUPPC023.PDF, Presented at the 3rd International Particle Accelerator Conference (IPAC 2012), New Orleans, Louisiana, USA, 20-25 May 2012 Status of the ATF2 lattices, by E. Marin et al.: TUPCO16.PDF, presented at the 2nd International Particle Accelerator Conference (IPAC 2011), San Sebastian, Spain, 4-9 September 2011