1. EXT Beam Measurements & Corrections Dispersion, Coupling, Beta Matching 10th ATF2 Project Meeting, June 30 2010M. Woodley1/31

2. 10th ATF2 Project Meeting, June 30 2010 120 m S-band RF Gun 1.3 GeV S-band Linac Damping Ring Beam Transport Inflector Coupling Correction β-matchFinal Focus Dump Final Doublet EXT INJ Laserwire XSR Laserwire e- IPBSM 10 μ W wires (x/y) screen Emittance Measurement 5 × WS, 4 × OTR 10 μ W wires (x/y/+10°/-10°) PIP WS 10 μ W wires (x/y/45°) 5 μ C wires (y/+1.3°/-1.3°) ATF / ATF2 Schematic Layout FOBO M. Woodley2/31

3. 10th ATF2 Project Meeting, June 30 2010 Injector system and Damping Ring can provide single-bunch beam or multi-bunch beam up to Q=2×10 10 1-20 bunches per train 1, 2, or 3 trains Minimum Damping Ring emittances achieved (c.2004) ε x = 1.5 nm ε y = 4 pm Y. Honda, et al., PRL92(2004)054802 Parameters M. Woodley parameterdesignMay 2010unit f rep 1.56 Hz Q2-10~510 9 e-/bunch E1.31.282GeV γε x (DR)3.04.810 -6 m γε y (DR)3.03.110 -8 m ε x (EXT)1.21.9nm ε y (EXT)12.012.5pm σzσz 88mm σδσδ 0.08 % βx*βx*4.040.0mm βy*βy*0.11.0mm η' x *0.1394 rad σx*σx*2.28.7μmμm σy*σy*37112nm 3/31

4. 10th ATF2 Project Meeting, June 30 2010 M. Woodley EMITTANCE & COUPLING MEASUREMENT & CORRECTION 4

5. 10th ATF2 Project Meeting, June 30 2010 XSRSRIF LW 00 mode σ y = 4.1 μm 01 mode σ y = 3.2 μm ATF2 design σ y ~ 5 μm M. Woodley5/31

6. 10th ATF2 Project Meeting, June 30 2010 QM7R: pole-tip radius = 16 mm … extracted beam offset = 22.5 mm Tokin 3393 (Ф = 32 mm) M. Woodley6/31

7. 10th ATF2 Project Meeting, June 30 2010 K1L K0L K2L QM7R replaced with larger bore (Ф = 42 mm) quadrupole in January 2009 K1L = 0.3 m -1 = 0.76  nominal  optics mismatch K2L = 46.6 m -2  x-y coupling for vertically off-axis beam: factor ~ 2-3 ×  y for  y = 1 mm (ε x :ε y = 100:1) Tokin 3393 (Ф = 32 mm) PRIAM simulation  K1L = 0.392 m -1 = 0.99 × nominal  K2L = 1 m -2 Tokin 3581 (Ф = 42 mm) Measured M. Woodley7/31

8. 10th ATF2 Project Meeting, June 30 2010 BS3X roll = 4.66 mrad Izv1 = -6.918 (-6.976) amp Izv2 = 1.270 ( 0.965) amp chi2 = 0.3102 Observed that first 2 EXT vertical correctors (ZV1X and ZV2X) needed to be strong to properly launch into EXT (since before EXT rebuild for ATF2 … ) hypothesize that correctors are compensating for a kick error in extraction channel simulate error kick by rolling individual elements; use ZV1X and ZV2X to correct orbit find error that gives best fit to actual ZV1X/ZV2X values → BS3X septum magnet roll BS3X was physically rolled ~ -4 mrad (March 17, 2010) to relieve ZV1X and ZV2X projected vertical emittance in EXT before coupling correction was improved (~20-40 pm before → ~10-20 pm after) M. Woodley8/31

9. 10th ATF2 Project Meeting, June 30 2010 M. Woodley DateN wire Emit (nm)BMAG May 18 201041.905 ± 0.0781.08 ± 0.03 Apr 21 201041.212 ± 0.0651.26 ± 0.03 Mar 17 2010BS3X rolled ~4 mrad (CCW) Feb 25 201041.868 ± 0.3361.15 ± 0.12 Feb 17 20104negative Feb 3 201041.626 ± 0.0951.10 ± 0.06 Jan 28 2010 Dec 8 200932.921 ± 0.1291.05 ± 0.03 DateN wire Emit (pm)BMAG May 18 2010511.7 ± 2.31.43 ± 0.25 Apr 21 2010515.4 ± 2.01.78 ± 0.17 Mar 17 2010BS3X rolled ~4 mrad (CCW) Feb 25 2010538.33 ± 1.11.10 ± 0.02 Feb 17 2010522.6 ± 1.41.15 ± 0.04 Feb 3 2010516.1 ± 0.71.06 ± 0.03 Jan 28 2010531.6 ± 1.21.03 ± 0.01 Dec 17 2009528.4 ± 1.71.01 ± 0.01 Dec 8 2009432.2 ± 1.91.35 ± 0.13 Horizontal EXT Emittance MeasurementsVertical EXT Emittance Measurements Anomalous DR → EXT vertical emittance growth fixed (?) 9/31

10. 10th ATF2 Project Meeting, June 30 2010 SQ WS 90° 180° 90° – x – y 11° 17° 28° 29° 42° 43° 29° 78.2 10.3 151.2 6.9 86.3 12.0 149.3 6.8 84.3 12.1 σ (μm) 7 < σ x / σ y < 22 10° wire orientation is optimal for beam tilt measurement SQ OTR Δψ ILC “orthonormal” coupling correction system M. Woodley10/31

11. 10th ATF2 Project Meeting, June 30 2010 projected vertical emittance (ε y ) reduced to 11.5 pm using QK1X required 57 individual wire scans per QK1X setting –X (MW1X / MW2X / MW3X / MW4X) × 3 –Y (MW0X / MW1X / MW2X / MW3X / MW4X) × 3 –+10° (MW0X / MW1X / MW2X / MW3X / MW4X) × 3 –-10° (MW0X / MW1X / MW2X / MW3X / MW4X) × 3 elapsed time: 7 hours for 5-point scan (!) … need multi-OTR to speed up realistically: 90 minutes for one 5-point QK scan (4 Y wires × 3 scans at each point) EmitY (pm) Coupling correction: single skew quadrupole scan M. Woodley11/31

12. Projected beam size measurements at x, 80 o, y and 100 o at 4 wire-scanner positions varying the strength of the QK1X skew quadrupole Coupling reconstruction using: Verification of the consistency of 80 o and 100 o measurements Search for an algorithm to reconstruct the beam matrix at QK1X position: The more reliable method consists of: Coupling measurements in ATF2 EXT (1) [Cecile Rimbault] a. Constrain 6 elements with  33 fits b. Constrain 3 elements with  13 fits c. Constrain the last one with  11 fits 10th ATF2 Project Meeting, June 30 2010 M. Woodley12/31

13. Coupling measurements in ATF2 EXT (2) [Cecile Rimbault] Comparison between measurements and beam matrix reconstruction result propagation  33  13 at QK1X - physical results but large error bars (not to mention imaginary ε y !) -large number of data sets is required to minimize statistical errors -analysis algorithm must guarantee positive-definite beam matrix 10th ATF2 Project Meeting, June 30 2010 M. Woodley13/31

14. 10th ATF2 Project Meeting, June 30 2010 M. Woodley 4.All 4 OTRs installed as of June 1 5.Target inserters, movers, cameras, controls, software … all OK 6.All 4 OTR targets melted during checkout! thin aluminized mylar target (1200 Å Al) Prosilica camera (3.75 μm / pixel) 14/31

15. 10th ATF2 Project Meeting, June 30 2010 M. Woodley pixels ATF2 EXT OTR1 ok … … melted June 2, 2010 single bunch beam Q ≈ 4×10 9 e-/bunch (0.64 nC) 1.56 Hz σ x ≈ 140 μm ; σ y ≈ 10 μm 2 μm nitrocellulose / 1200 Å Al ~4 minutes in beam until damage damaged targets will be replaced >6 μm kapton / 1200 Å Al >100 μm Al foil 10 μm tungsten X/Y wires will be added to target holders scribe line 15/31

16. 10th ATF2 Project Meeting, June 30 2010 M. Woodley DISPERSION MEASUREMENT & CORRECTION 16

17. 10th ATF2 Project Meeting, June 30 2010 M. Woodley Flight Simulator Dispersion Measurement / Correction 17/31

18. 10th ATF2 Project Meeting, June 30 2010 M. Woodley Before Correction After Correction ηxηx η' x I QF1X (amp)I QF6X (amp) Response Matrix Measurement Horizontal Dispersion Correction 18/31

19. 10th ATF2 Project Meeting, June 30 2010 QS1XQS2X “Sum-Knob”: I QS1X = I QS2X Simulated η y * (right) and η' y * (right), back-propagated from IP Vertical Dispersion Correction (FD-phase) Δ Sum-Knob = -0.15 A IP-phaseFD-phase M. Woodley19/31

20. 10th ATF2 Project Meeting, June 30 2010 M. Woodley 2010/ 2/ 18 10mm at IP The old orbit had a large offset around QF21X, QM16FF. I applied careful orbit tuning around QF21X, QM16FF with FF mover. 2010/ 2/ 25 1mm at IP 2010/ 3/ 18 2mm at post-IP We used the fast kicker for the beam extraction. We switched back to SLAC kicker. 2010/ 4/ 7 3.8mm at post-IP 2010/ 4/ 8 3.6mm at post-IP 3.6mm at IP Dispersion for 4/7 QS1X= -1A QS2X= -1A Dispersion for 4/8 QS1X= -2.8A QS2X= -2.8A Summary of Vertical Dispersion at IP IP dispersion is not sensitive to Sum-knob From Okugi-san’s presentation (ATF Ops 2010.04.09) 20/31

21. 10th ATF2 Project Meeting, June 30 2010 M. Woodley BETA MATCHING 21

22. 10th ATF2 Project Meeting, June 30 2010 M. Woodley R I = waist shiftmagnification phase shift (α*  0) alpha knob beta knob phase knob “Irwin Knobs” for β-matching : R = R I × R 0 “Irwin Knobs” R0R0 Final Focus 22/31

23. 10th ATF2 Project Meeting, June 30 2010 M. Woodley get initial magnet strengths from control system, compute R 0 for a desired knob type, compute R I (n) for a small step in s, m, or ψ –small steps required due to nonlinear ΔKL Q /ΔKnob set R=R I (n)*R 0 to make one knob step use MAD matching to fit to desired elements of R using FF matching quadrupoles changes to magnet strengths tend to be symmetric in the knob value … computed strengths for quadrupoles that start at zero tend to go bipolar tried waist shift and magnification knobs during tuning week … seem OK 23/31

24. 10th ATF2 Project Meeting, June 30 2010 M. Woodley QM*FF Currents (amps)IP Twiss Parameters Vertical Waist Scan (±5β*) [BX10BY10 optics] 24/31

25. 10th ATF2 Project Meeting, June 30 2010 M. Woodley Vertical Magnification Scan (0.5-2) [BX10BY10 optics] QM*FF Currents (amps)IP Twiss Parameters 25/31

26. 10th ATF2 Project Meeting, June 30 2010 M. Woodley QM*FF Currents (amps)IP Twiss Parameters Vertical Phase Scan (0-90°) [BX10BY10 optics] 26/31

27. 10th ATF2 Project Meeting, June 30 2010 M. Woodley R0R0 QK1XQK2XQK3XQK4X R I = “Irwin Knobs” for coarse coupling correction: R = R I × R 0 27/31

28. 10th ATF2 Project Meeting, June 30 2010 Summary (1) improvements made to both hardware and diagnostics may have cured the anomalous vertical emittance growth at extraction from the Damping Ring that has been observed for many years – QM7R replacement – BS3X roll – DR emittance diagnostics (XSR, SRIF, LW) the new EXT multi-OTR system should improve our ability to measure and correct emittance – faster emittance measurement and skew quad optimization – possibility of 4D beam-matrix measurement / reconstruction / correction Flight Simulator dispersion measurement / correction software seems to work – excellent improvements in BPM resolution and reliability make it possible – propagation of dispersion fits to wire scanners, IP, PIP, etc. – correction of FD-phase η y with sum-knob – model-based η x correction with QF1X/QF6X sometimes has trouble, but “manual” correction works – jitter-based (SVD) dispersion measurement / monitoring still a possibility M. Woodley28/31

29. 10th ATF2 Project Meeting, June 30 2010 Summary (2) Flight Simulator “Irwin” knobs provide possibility of orthogonal “manual” β- matching – QM*FF only … FF / FD magnets can remain at design strengths – orthogonal waist and β control – orthogonal phase control … intriguing possibilities (vertical dispersion, feedback, … ) – control of IP x-y and x'-y coupling may also be possible M. Woodley29/31

30. 10th ATF2 Project Meeting, June 30 2010 M. Woodley Ongoing Work (1) need to archive future EXT multi-wire and multi-OTR emittance measurements – raw beam sizes, raw dispersion data, wire-to-wire and IEX to MW0X R-matrices – analysis results (with errors) coupling measurement / 4D beam reconstruction – acquire full data set (X/Y/U/+10/-10) plus raw data files for all EXT wires – cross-check raw data normalization and who’s who … is everything OK now? – acquire OTR beam images for all EXT OTRs and extract lengths of semi-major and semi- minor axes and ellipse tilt angles – try 4D reconstruction … Ilya Agapov’s “Cholesky decomposition” method? consistency checks for emittance and Twiss – forward propagate from EXT – backward propagate from IP Flight Simulator computer control of Damping Ring RF frequency ramp 30/31

31. 10th ATF2 Project Meeting, June 30 2010 M. Woodley Ongoing Work (2) find a better “coarse” IP-phase η y knob – closed bump in FF matching quadrupole region? – generate in Damping Ring? – is there a way to use the “Kubo bump” to control IP-phase vertical dispersion? Flight Simulator “Irwin” knob development – GUI – FF optics with all QM*FF ON at reasonable currents – coupling knobs revisit SLAC epoxy kicker multipoles (if we don’t switch to fast stripline extraction permanently) – are observed EXT BMAG values consistent? – why are vertical bumps at KEX1 closed? are the kickers identical? – is there a way to use the “Kubo bump” to control IP-phase vertical dispersion? and on and on … 31/31