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News from ATF2 Frank Zimmermann KEK visit, 20-24 February 2012 Thanks to P. Bambade, M. Barnes, A. Faus-Golfe, K. Kubo, S. Kuroda, T. Naito, T. Okugi, K. Oide, Y. Papaphilippou, D. Schulte, T. Tauchi, N. Terunuma, N. Toge, R. Tomas Status, limits and plan for ATF spot-size tuning Follow up of planned CLIC contributions ground motion sensors, Q1 & Q2 quads, extraction kicker Future of ATF beyond 2013/14

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ATF related discussions & activities 20.02. conversation w. Katsunobu Oide about ATF2 future 22.02. tour of e-beam welding and STF (A. Yamamoto) 23.02. 6:30 to ~10 am joining Toshiyuki Okugi for beam-size tuning in ATF control room 23.02. 10-12:00 discussing with T. Tauchi & with J. Urakawa 23.02. 15:00 meeting w Nobu Toge on ATF2 future and proposed CLIC contributions 23.02. 17:00 further discussions with Junji Urakawa 24.02. morning ATF control room, IP-BSM tuning 24.02. 15:00 ATF operation meeting, reports Naito & Okugi & Oroku 24.02. discussion with Toshiaki Tauchi on ATF2 future & CLIC 01.03. 12:00-15:00 back at CERN - lunch w Angeles Faus-Golfe, discussions on fast kicker plan Emails with Mike Barnes, Philip Bambade, Nobuhiro Terunuma, A.F.-G.

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ATF2 parameters IP parameter nominalApril 2010Dec. 2010February 2012 beam energy1.3 GeV xx 2 nm1.7 nm1.8-2.7 nm1.84 nm yy 12 pm

Confusion of signal fluctuation with modulation (if bad S/N) ModulationFluctuation Fluctuation (fake modulation) : sig / sig ~ 0.18 (for S/N ~ 1/10) If fake M > expected M, it becomes confusing Expected M : 0.17 (300 nm) Expected M : 0.42 (200 nm) M. Oroku, 2011 in 2012 laser system is improved compared with 2011; more careful setup & optimization of laser paths, focusing & stability phase scan: change length of one laser path by changing distance of the delay line with piezo

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194.9 +/- 8.29 nm (10 measurements RMS) 17 February 2012

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IP y spot size tuning relaxed optics: x,y *=10 mm x 0.3 mm at present expected vertical beam size ~70 nm ( x =1.84 nm, y =15.6 pm) IP BSM 30 degree mode (no signal at this mode in early 2011) multiknobs for tuning: always scan y, D y, xy coupling scan of xy coupling by upstream skew quadrupole not orthogonal scanning the above three knobs for every step of xy; it would be better to rotate IP BSM, but not possible at the moment fluctuations in DR vertical orbit leads to change in IP beam size optimize, re-scan injected orbit with ZV1X corrector (angle at IP), the dependence is very strong, a change by 0.01 A (3 rad kick; orbit < 500 m) changes spot size by ~30% first scan of the skew sextupole (placed at D0) showed dependence this skew sextupole should compensate for net skew sextupole component in all ATF2 quadrupoles (why is there such component in the first place?) IP BSM size reduction factor - significant, various contributions the real beam size is (~0.8 times?) smaller than measured below about 100 nm one can change to 174 degree mode attempt to scan DR f rF affected timing synchronization with laser T. Okugi, 23.02.2012

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example IP multiknob scans y scan optimum + 0.02 xy scan optimum + 0.02 y scan optimum + 0.005 D Y scan optimum=-0.05 T. Okugi, 23.02.2012

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other example IP scans skew sextupole scan (first ever) optimum + 8A ZV1X (incoming orbit) strong dependence expected? xy scan optimum -10A T. Okugi, 23.02.2012

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laser wire scan showed about 165 nm in 10 successive measurements first time switch to 174 degree mode (which should be used for final tuning!): attempt to find optimal focal range position; max modulation of 12 % reached; if true signal this would be a beam size around 100 nm next steps: towards nominal optics (more favorable background conditions and reduced sensitivity to orbit drifts in the high beta quads) further strategy push only y * or both x * and y *? week 13/2: * y =1.0 mm ; 20/2: * y =0.3 mm; 5/3: * y =0.1 mm - however, backed off to higher * y on 15/03; saw clear modulation with 30 degrees mode for all optics, but background level and signal jitter are increased for decreasing * y movable collimator may reduce background chromaticity and geometric aberration scans not yet applied understand orbit effect stabilize extraction line emittance (correlation, orbit feedback?) longer tuning periods, larger team IP y spot size tuning contd T. Okugi, & M. Oroku et al, 23.02.2012

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10 scans with ~160 nm

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y ~100 nm 174 degree mode

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history of beam size y * [nm] Great Eastern Japan Earthquake & Recovery

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present limitations laser set up & laser stability, intrinsic reduction factor relaxed optics strategy to move forward? nonlinear field components in final quadrupoles expected to be a limit only