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EXT Beam Measurements & Corrections

EXT Beam Measurements & Corrections. Dispersion, Coupling, Beta Matching. ATF / ATF2 Schematic Layout. Emittance Measurement 5 × WS, 4 × OTR 10 μ W wires (x/y/+10°/-10°). Final Doublet. Coupling Correction. Final Focus. β -match. Dump. Inflector. Laserwire. EXT. INJ. Laserwire.

gary-watkins
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EXT Beam Measurements & Corrections

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  1. EXT Beam Measurements & Corrections Dispersion, Coupling, Beta Matching M. Woodley

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

  3. Parameters • Injector system and Damping Ring can provide single-bunch beam or multi-bunch beam • up to Q=2×1010 • 1-20 bunches per train • 1, 2, or 3 trains • Minimum Damping Ring emittances achieved (c.2004) • εx = 1.5 nm • εy = 4 pm • Y. Honda, et al., PRL92(2004)054802 M. Woodley

  4. EMITTANCE & couplingMeasurement & Correction M. Woodley

  5. XSR SRIF σy ~ 5 μm σy ~ 5 μm LW 00 mode σy = 4.1 μm ATF2 design 01 mode σy = 3.2 μm M. Woodley

  6. QM7R: pole-tip radius = 16 mm … extracted beam offset = 22.5 mm Tokin 3393 (Ф = 32 mm) M. Woodley

  7. 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 × yfor y = 1 mm (εx:εy = 100:1) • K1L = 0.392 m-1 = 0.99 × nominal • K2L = 1 m-2 Measured PRIAM simulation K0L K1L K2L Tokin 3581 (Ф = 42 mm) Tokin 3393 (Ф = 32 mm) M. Woodley

  8. 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) BS3X roll = 4.66 mrad Izv1 = -6.918 (-6.976) amp Izv2 = 1.270 ( 0.965) amp chi2 = 0.3102 M. Woodley

  9. Horizontal EXT Emittance Measurements Vertical EXT Emittance Measurements Anomalous DR → EXT vertical emittance growth fixed (?) M. Woodley

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

  11. Coupling correction: single skew quadrupole scan EmitY (pm) • projected vertical emittance (εy) 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) M. Woodley

  12. Couplingmeasurements in ATF2 EXT (1) [Cecile Rimbault] • Projectedbeam size measurementsat x, 80o, y and 100oat 4 wire-scanner positions varying the strengthof the QK1X skewquadrupole • Coupling reconstruction using: • Verificationof the consistency of 80o and 100omeasurements • Searchfor an algorithmto reconstruct the beammatrixat QK1X position: • The more reliablemethodconsists of: a. Constrain 6 elementswiths33fits b. Constrain 3 elementswiths13fits c. Constrain the last one withs11fits M. Woodley

  13. Couplingmeasurements in ATF2 EXT (2) [Cecile Rimbault] at QK1X Comparisonbetweenmeasurements and beammatrix reconstruction result propagation s33 s13 • - physical results but large error bars (not to mention imaginary εy!) • large number of data sets is required to minimize statistical errors • analysis algorithm must guarantee positive-definite beam matrix M. Woodley

  14. All 4 OTRs installed as of June 1 Target inserters, movers, cameras, controls, software … all OK All 4 OTR targets melted during checkout! • thin aluminized mylar target (1200 Å Al) • Prosilica camera (3.75 μm / pixel) M. Woodley

  15. ATF2 EXT OTR1 • June 2, 2010 • single bunch beam • Q ≈ 4×109 e-/bunch (0.64 nC) • 1.56 Hz • σx ≈ 140 μm ; σy ≈ 10 μm • 2 μm nitrocellulose / 1200 Å Al • ~4 minutes in beam until damage pixels ok … • 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 pixels scribe line … melted pixels M. Woodley

  16. DispersionMeasurement & Correction M. Woodley

  17. Flight Simulator Dispersion Measurement / Correction M. Woodley

  18. Horizontal Dispersion Correction Response Matrix Measurement After Correction Before Correction ηx η'x IQF1X (amp) IQF6X (amp) M. Woodley

  19. Vertical Dispersion Correction (FD-phase) QS1X QS2X “Sum-Knob”: IQS1X = IQS2X Δ Sum-Knob = -0.15 A IP-phase FD-phase Simulated ηy* (right) and η'y* (right), back-propagated from IP M. Woodley

  20. Summary of Vertical Dispersion at IP 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 We used the fast kicker for the beam extraction. 2010/ 3/ 18 2mm at post-IP 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 IP dispersion is not sensitive to Sum-knob From Okugi-san’s presentation (ATF Ops 2010.04.09) M. Woodley

  21. BETA MATCHING M. Woodley

  22. “Irwin Knobs” Final Focus R0 “Irwin Knobs” for β-matching : R = RI × R0 alpha knob beta knob phase knob RI = waist shift magnification phase shift (α*  0) M. Woodley

  23. get initial magnet strengths from control system, compute R0 • for a desired knob type, compute RI(n) for a small step in s, m, or ψ • small steps required due to nonlinear ΔKLQ/ΔKnob • set R=RI(n)*R0 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 M. Woodley

  24. Vertical Waist Scan (±5β*) [BX10BY10 optics] IP Twiss Parameters QM*FF Currents (amps) M. Woodley

  25. Vertical Magnification Scan (0.5-2) [BX10BY10 optics] IP Twiss Parameters QM*FF Currents (amps) M. Woodley

  26. Vertical Phase Scan (0-90°) [BX10BY10 optics] IP Twiss Parameters QM*FF Currents (amps) M. Woodley

  27. QK1X QK2X QK3X QK4X R0 “Irwin Knobs” for coarse coupling correction: R = RI × R0 RI = M. Woodley

  28. 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 ηy with sum-knob • model-based ηx correction with QF1X/QF6X sometimes has trouble, but “manual” correction works • jitter-based (SVD) dispersion measurement / monitoring still a possibility M. Woodley

  29. 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. Woodley

  30. 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 M. Woodley

  31. Ongoing Work (2) • find a better “coarse” IP-phase ηy 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 … M. Woodley

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