Congratulations to the team for An excellent and successful programme

1. Congratulations to the team for • An excellent and successful programme • A well-prepared and comprehensive review! • Primary goals have expanded to include a “third” goal • Quantification and control of beamline impedance • We believe goal 1 and impedance issues should be separated (next slide)

2. Goal 1: 37 nm • Achieved 64 nm at low bunch charge • Already clear demonstration of optics and aberration control • Should make this very clear (quantify) • Optics control and tuning algorithms work! • Last “100m” will be challenging • 6437 nm • Kicker and EXT (optics) issues etc. • programmes already in place • understanding diagnostics (IP BSM systematics) • Caveat: understand impact of reduced beta_x* to vertical beam aberrations. Should be a goal to implement. • Going to high currents does not seem to offer any benefit in understanding optics issues • Understanding emittance preservation at higher bunch charge is a new goal • But equally important for LC

3. Goal 2 • Goal II assumes: • 1-"wakefield" problem is solved to enable 1-2e10 e/bunch •  (IPBPM resolution at 7e9/bunch is 3.7nm) • 2-IP Jitter below 30%. So far upper boundary is given by beam size •  during March run: •    10nm < IPjitter < sqrt(65^2-48^2)=44nm • Instrumentation concerns: • 1-IPBPM resolution in largedivergence location? • 2-IPBPM calibration: •  +longprocess •  +Piezoread-outresolution=20nm •  +temperatureeffects in full set-up

4. Goal 2 recommendations • Sharpengoal II being more specific • Includebeam sizestabitlity in goal II • solvethe "wakefield" problem. • Measureground motion (GM sensor ontheway) • Tryto findthejittersource by moving 1 or 2 highresolutionBPMsfrom FD to EXT (maybe not expensive) • Temperaturestabilization by heating IP chamber (seemsalreadyplanned) • UseIPBPM phase info to avoid V-shapefit

5. Collective Effects • Collective effects have been shown to cause significant increase (a factor of ~5 up) of eyin the EXT line. • Simulations in FFS indicate cavity BPMs not enough • include other sources (bellows?) • ~2 pm/1e9 EXT doesn’t explain IP beam size • Continue programme to quantify sources of wakefield kick • impedance calculations for all components • orbit response measurements (vs bunch charge) • attention to asymmetric sources • … • Zero current emittance growth in EXT appears to be 3-4 pm • not dominant • Consider installing bellows shields • should be inexpensive • Further experimental studies on wakefield tuning • movable impedance • orbit bumps and /or betatron oscillation

6. Magnet field quality (E. Marin) A very clear and comprehensive study. The merits of the study and of the replacement of QF1FF by 4Q17 is: • to clear the ATF2 magnet field-quality as one possible cause of the current mismatch between the predicted and measured beam size. • by cancelling the magnet non-linearities, to make it possible to investigate the properties and the limitations of the non-local chromatic correction optics at 35 nm and eventually smaller spot sizes.

7. Diagnostics and instrumentation • Linac-DR feedbacks and corrections are not configured optimally for the FF beamline

8. Damping Ring Performance The ATF2 beam test facility is intended to prove the expected performance of the ILC Beam Delivery System. The ATF linac and damping ring systems that feed beam to ATF2 are to provide a stable beam of nominal intensity with the required emittance and optical parameters. The beam must be stable to varying degrees over a range time – scales from pulse to pulse to multi-hour or multi-day. Several reports devoted to these upstream systems were included in the review in order to provide an assessment of their ability to satisfy this requirement.

9. Review Charge: • Does the ATF routinely provide a stable low-emittance beam to allow ATF2 tuningto proceed in an efficient manner? • Goal 2 may be viewed as a test of the upstream systems to provide stable beam. If the pulse to pulse stability is too poor then the tuning process will not converge and the emittance will also be unstable.

10. Findings - Linac: • The linac trajectory varies by as much as a few mm during a few hour period. The linac energy also varies over a similar time period. • The linac klystron / modulator large, common HVPS is to be replaced during summer 2013 due to its age and reliability performance. HVPS stability is 0.2%. The HVPS does not appear to be a source of instability. • Linac trajectory instability may be caused by gun cavity, accelerating structure and high Q device (SLED) cooling water temperature instability. • There is an intensity cut at the IP section to avoid the the wake field effect, the range of 0.5-2.0x10e9 is used at last month. Usually, the injector can keep the IP intensity in 1 shift or more. This slows the IPBSM scanning.

11. Findings – Ring stability • There is minimal effect on ATF2 tuning when the extraction point is kept stable. • Feedback is sometimes used for the ring. The orbit feedback erroneously caused energy changes while trying to fix the orbit. • The ring emittance measurement is based on an estimate of the beta function at the XSR source point. This is difficult to verify and may be a source of variability. • During short downtime periods the ring magnets are left on. This keeps the ring environment stable. • However, ring alignment checks are done with magnets off. • Continuous operation requires extra resources and effort but appears to worthwhile.

12. Findings - emittance • There are two recent measurements of emittancesvs I. • The measurement using sum / difference adjustment of the dispersion matching quads to correct coupling appears promising. • Possible errors in kicker and BS3X

13. Concerns • Linac instability with plan but unsure about source • Unsure about exact sources of instability in ring • Ring emittance measurement • Jitter normalized to beam size.

14. Injection tuning (T. Naito) • - It looks most likely that the drift of water temperature induces the abnormal orbit in the linac via the change of the rf phase or amplitude of the rf gun through the initial bends. It should be confirmed by analyzing the data or changing the rf gun phase or voltage intentionally. The improvement of the cooling system should make the situation better. Also a simple feedback either on the initial bends or the rf gun voltage may stabilize the orbit without any new hardware. • - I am not sure but does the linac have an energy feedback on the injection beam? If not, please consider to introduce it. • Emittance tuning: (S. Kuroda) • - The bunch current dependence of the emittance looks weak, not sufficient to explain the measurements at EXT. • - The achieved vertical emittance is even better than the requirement, esp in March 2013 (8 pm).

15. Alignment (S. Araki) - What is the tolerance on the horizontal and vertical alignments, assuming the correction methods? Kicker optics (M. Woodley) - What about the beam current dependence of the orbit and orbit responses? Beam optics design (G. White): IP beam size tuning (T. Okugi) - Summarize the beam emittance estimation at the ring, EXT, and IP with beam current dependence. - Some data analyses seem insufficient. All data including measurement errors should be took into account. Also combination of results of different devices should be considered.

16. Collaboration & Future Programmes • Important to unify further the groups involved in Goal 2 • Low beta* an extrapolation of goal 1 (good) • Consider SC FD test back on the table. • Budget situation for 2013 is critical