LAL-IHEP collaboration on the linear collider final focus

LAL-IHEP collaboration on the linear collider final focus & ATF 2 prototype Philip Bambade Laboratoire de l’Accélérateur Linéaire Université Paris 11, Orsay, France On behalf of: LAL: BLANCO Oscar (Ph. D) LIU Shan (Ph. D, 3 -year FCPPL-CSC grant) IHEP: BAI Sha (staff, co-directed LAL-IHEP Ph. D & Eiffel grant in the past) GAO Jie (prof. , ILC group leader, LAL staff in the past) WANG Dou (staff) WANG Yi Wei (Ph. D, 3 -month at LAL in 2012/13 with French Embassy support) NSFC contract n° 11175192 6 th FCPPL Workshop, Nanjing, China IN 2 P 3 support ANR & LABEX P 2 IO grants 27 -29 March 2013

ATF & ATF 2 R&D for linear colliders

Parameters Beam Energy [Ge. V] ATF 2 1. 3 ILC CLIC 250 1500 L* [m] 1 3. 5 - 4. 5 3. 5 x/y [m. rad] 5 E-6 / 3 E-8 1 E-5 / 4 E-8 6. 6 E-7 / 2 E-8 IP x/y [mm] 4 / 0. 1 21 / 0. 4 6. 9 / 0. 07 IP ’ [rad] 0. 14 0. 0094 0. 00144 E [%] ~ 0. 1 ~ 0. 3 Chromaticity ~ / L* ~ 1 E 4 ~ 5 E 4 Number of bunches 1 -3 (goal 1) ~ 3000 312 Number of bunches 3 -30 (goal 2) ~ 3000 312 Bunch population 1 -2 E 10 3. 7 E 9 IP y [nm] 37 5. 7 0. 7 ATF 2 = ü scaled ILC FFS ü start point of CLIC FFS concept of local compact chromaticity correction Beam control trade-off Linac tech. & sources

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

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

FCPPL FJPPL FKPPL

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

First measurements of 70 nm vertical beam sizes in December 2012 confirmed repeatedly in 2013 ! 0. 8 e 9 < N < 1. 2 e 9 Nominal parameters: N = 10+10 σy = 37 nm σy = 72. 8 + 5. 4 - 4. 7 nm Modulation of Compton scattered photon rate resulting interaction with interference fringe pattern

LAL-IHEP collaboration topics 1) Beam halo generation, propagation, collimation and measurements in ATF/ATF 2 2) Development and implementation of mono-crystalline CVD diamond sensors for beam halo and Compton recoil electron measurements after the IP of ATF 2 3) Orthogonality of interaction point waist corrections in the presence of σ13 and σ24 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 !

Beam halo and BSM background issues GEANT 4 (simplified conditions) Halo intercepted on post-IP bend magnet vertical gap final doublet beam pipe chromatic correction c-band / ref. BPMs under study…

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

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 ATF 2”, ar. Xiv: 0810. 5467 v 1

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

Shan LIU (LAL)

GEANT 4 I. Khvastunov

Plan for 2013: install 1 st prototype @ ATF 2 at year end

IP BSM fringe tilt increases measured σy Proposed diagnosis measuring σy as function of horizontal waist position ( x scan) Sha BAI (IHEP)

Orthogonality of αx scan must be good enough BX 10 BY 1 optics vs BX 2 p 5 BY 1 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

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

Chromatic correction concentrated on the vertical plane ILC • enlarged βx*=45 mm, variable βy* – choose βx*=45 mm: as without chromatic correction, σx* minimized – with chromatic correction mainly in the vertical plane (green line): σy* minimized when βy*= 0. 08 mm – σy*=0. 4∙σy_nom* ( σx*=3∙σx_nom* ) – Luminosity recovery seems possible and there’s room for optimization. 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 length σy Yiwei Wang (IHEP) 22 βy

Request for FCPPL support in 2013 Conclusion & prospects • ATF 2 : 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 !

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 ATF 2, Chinese Phys. C 2012 Vol. 36(8): 756 -760 Optical configurations with variable beta* at different IP locations in ATF 2 , 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 ATF 2 beam line , by B. Bolzon et al. : THPD 077. PDF, Presented at the 1 st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23 -28 May 2010 ATF 2 ultra-low IP betas proposal , by R. Tomas et al. : LAL-RT-09 -11, Presented at the 23 rd Particle Accelerator Conference (PAC 09), Vancouver, Canada, 4 -8 May 2009 Linear Collider Test Facility: Twiss Parameter Analysis at the IP/Post-IP location of the ATF 2 beam line , by B. Bolzon et al. : THPD 077. PDF, Presented at the 1 st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23 -28 May 2010 Simulation of Multiknobs Correction at ATF 2 , by S. Bai et al. : THPD 096. PDF, Presented at the 1 st International Particle Accelerator Conference (IPAC 2010), Kyoto, Japan, 23 -28 May 2010 Waist corrections at the interaction point of ATF 2 in the presence of IPBSM fringe rotations and input BPM sigma 13, sigma 24, by S. Bai et al. : TUPPC 023. PDF, Presented at the 3 rd International Particle Accelerator Conference (IPAC 2012), New Orleans, Louisiana, USA, 20 -25 May 2012 Status of the ATF 2 lattices , by E. Marin et al. : TUPCO 16. PDF, presented at the 2 nd International Particle Accelerator Conference (IPAC 2011), San Sebastian, Spain, 4 -9 September 2011