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Commissioning Status of the LCLS Accelerator and Undulator Systems

Commissioning Status of the LCLS Accelerator and Undulator Systems. Henrik Loos for the LCLS Commissioning Team. Overview. LCLS Introduction Accelerator Commissioning Emittance Laser Heater Bunch Compression Feedback Stability Undulator Commissioning Diagnostics Beam Based Alignment

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Commissioning Status of the LCLS Accelerator and Undulator Systems

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  1. Commissioning Status of the LCLS Accelerator and Undulator Systems Henrik Loos for the LCLS Commissioning Team

  2. Overview • LCLS Introduction • Accelerator Commissioning • Emittance • Laser Heater • Bunch Compression • Feedback • Stability • Undulator Commissioning • Diagnostics • Beam Based Alignment • Spontaneous Radiation • Outlook

  3. Injector (35º) at 2-km point Existing 1/3 Linac (1 km) (with modifications) New e- Transfer Line (340 m) X-ray Transport Line (200 m) Undulator (130 m) Near Experiment Hall Far Experiment Hall Linac Coherent Light Source at SLAC X-FEL based on last 1-km of existing linac 1.5-15 Å

  4. LCLS Accelerator Layout beam parked here Dec 2008… Commission Jan-Aug 2008 Commission Mar-Aug 2007 250 MeV z  0.19 mm   1.6 % 4.30 GeV z  0.022 mm   0.71 % 13.6 GeV z  0.022 mm   0.01 % 6 MeV z  0.83 mm   0.05 % 135 MeV z  0.83 mm   0.10 % Linac-X L =0.6 m rf= -160 Linac-0 L =6 m rf gun L0-a,b Linac-3 L 550 m rf  0° Linac-1 L 9 m rf  -25° Linac-2 L 330 m rf  -41° 25-1a 30-8c 21-3b 24-6d ...existing linac 21-1 b,c,d undulator L =130 m X BC1 L 6 m R56 -39 mm BC2 L 22 m R56 -25 mm undulator DL1 L 12 m R56 0 DL2 L =275 m R56  0 SLAC linac tunnel research yard X-rays in spring 2009

  5. LCLS Beam Diagnostics gun 4 wire scanners + 4 collimators L1X TCAV0 old screen 3 wires 2 OTR 4 wire scanners L0 3 OTR vert. dump L1S heater m wall 3 wires 3 OTR sz1 sz2 L2-linac L3-linac DL1 135 MeV BC1 250 MeV BC2 4.3 GeV TCAV3 5.0 GeV BSY 14 GeV DL2 14 GeV undulator 14 GeV stopper • 2 Transverse RF cavities (135 MeV & 5 GeV) • ~195 BPMs and toroids • 7 YAG screens (at E135 MeV) • 12 OTR screens at E 135 MeV • 15 wire scanners (each with x & y wires) • CSR/CER pyroelectric bunch length monitors at BC1 & BC2 • 4 beam phase monitors (2856 – 51 MHz) • Gun spectrometer line + injector spectrometer line • YAG screens • OTR screens • Wire scanners

  6. Injector Emittance Commissioning Measured emittance meets requirement for FEL Emittance measured at OTR screen with upstream quad scan for 95% charge Q = 250 pC E = 135 MeV Iterative Optimization with gun solenoid & quads, steering correctors, and matching to design Twiss γεx = 0.83 μm For 1 nC γεx = 1.07 μm γεy = 1.11 μm γεy = 0.86 μm

  7. New LTU Wire-Scanners Working Well Emittance to upstream of undulator (mostly) preserved Emittance horizontal 1.1um

  8. Laser-Heater Working Well YAGS2 RF deflector ON energy time Laser OFF σE/E< 12 keV YAGS2 Laser: 40 µJ σE/E 45 keV YAGS2 Laser: 230 µJ σE/E 120 keV Dec. 10, 2008

  9. Laser-Heater Working Well YAGS2 YAGS2 Laser energy 230 µJ σE/E 120 keV Laser OFF Double-horn is consistent with laser beam presently ~50% larger in transverse size than electron beam

  10. Bunch Compression in BC2 RF ‘streak’ 2.44 m V(t) sy e- S-band sz D 90° V0≤ 20 MV bc bp Bunch Length vs. Compression Measurement Calibration Q = 0.25 nC σz ≈ 2 μm

  11. CSR Emittance Growth in BC2 Beam emittance can grow due to coherent synchrotron radiation effects during bunch compression Compare measurements with simulation code Confirms 100% projected emittance growth at nominal compression Slice emittance not effected at operating point Emittance growth mechanisms well understood Y. Ding, Z. Huang

  12. Laser & Electron-Based Feedback Systems Steering Loop BPMs Laser CER detectors sz1 sz2 V0 gun d0 d3 d1 d2 L0 1 2 V1 V2 V3 L2 L3 X L1 D. Fairley,J. Wu DL2 DL1 BC1 BC2 • Transverse Loops Stabilize: • Laser spot on cathode • Gun launch angle • Injector trajectory • X-band cavity position • Linac & LTU trajectory (5) • Undulator trajectory • Longitudinal Loops Stabilize: • DL1 energy • BC1 energy • BC1 bunch length • BC2 energy • BC2 bunch length • Final energy

  13. LCLS Beam Stability Injector Beam position Laser: 3% Injector: 4% at 250 MeV Linac: 10-15% at 9 GeV Undulator: ~20% Goal is 10% Bunch length BC1: 5% at 250 A BC2: 8% at 3000 A Charge & Energy ΔQ/Q ≈ 1.5% ΔE/E ≈ 0.03% at 13.6 GeV 1-s beam size Linac D. Ratner Feedback system keep machine stable for short-term …

  14. Electron Beam Reaches Brightness for 1.5 Å … and for long-term! FEL Power Prediction 3D Gain Length Gain length and saturation power calculated from measured electron beam parameters

  15. LCLS Undulator Configuration BFW In/Out Undulator Quad Corr RF BPM Beam Scan Girder Girder Movers • 33 Undulator segments on individual girders (21 installed) • Undulator, Quad, BPM, BFW move with girder • Beam Finder Wire (BFW) retractable • Girder alignment with BFW at upstream and BBA at downstream end

  16. First Beam to Main Dump BPMs mistimed 1st shot (stops in just into undulator) 2nd shot (all the way to dump)

  17. 66 Beam Finder Wires (BFW) Tested and Aligned …also emittance measured using 4 BFW’s Centering Works Well

  18. Undulator Re-Pointing is Tested Enables motion of the entire undulator to steer electron beam and X-rays to a new axis

  19. Undulator Cavity BPMs Calibrated with Beam using girder motion vs. BPM reading 6% rms scale variation in X (will be improved) fixed 6% rms scale variation in Y (will be improved)

  20. Beam Based Alignment Schematic BPM and quadrupole offsets are unknown Vary energy, measure orbit to determine straight line Δb0 Δb1 Δb2 Δb3 Δb0 Δq1 Δq2 Δq3 E2 x,x’ E1 Δy0 Δy1 Δy2 Δy3 Δy4 BPM Offsets Δbi Quad Offsets Δqi E1<E2

  21. Undulator Beam-Based Alignment Converged 100 µm 40 µm Final Round of Beam-Based Alignment Earth’s field pattern RMS = 64 µm Verify alignment with quad strength variations RMS = 26 µm

  22. Undulator Beam-Based Alignment Converged 20 mm 5 mm Dispersion-Free (from 4.3 to 13.6 GeV)

  23. Undulator Magnet Installed at U-25 (of 33) Photo is just an example, and not U-25

  24. High resolution RF-BPMs RF-BPMs Resolve 10 nrad Kicks (~300 nm resolution) 20 BPMs in a 6-parameter fit (X0, X0', Y0, Y0', Xkick, Ykick) has a 0.5 µm Xrms fit residual and a 0.3 µm Yrms fit residual (NAVG=25).

  25. Beam-Based Measured Field Integrals MMF Measurements (U25) Beam-based measurement agrees with MMF data Beam-Based Measurements (U25) IX1 IX1 IY1 IY1

  26. Measured Undulator Girder Backlash (<1 mm) 0.7 mm backlash 3-parameter fit to 20 cavity BPMs along the undulator (y0, y0, and Dy) Dy = 30 nrad kick due to quad ±4 mm (y0, y0) Feb. 7, 2009

  27. Wakefield Energy-Loss in the LCLS Undulator Wake field energy loss agrees well with theory Important to adjust taper of undulator correctly

  28. 84 meters of Undulator Installed

  29. Observation of Undulator Radiation Spontaneous X-Rays (U25 undulator only) Radiation from dump bends Used to measure X-ray energy at K-edge of YAG crystal absorption

  30. X-Ray Diagnostics in the Front End Enclosure Slit Fixed Mask Solid Attenuators Reticule K-Monochromator Collimators Thermal Sensor Pop-in cameras C0 collimator (in e- beam dump Gas Attenuator Gas Detector Beam Direction Direct Imager (Scintillator) Pop-in cameras Gas Detector FEL Offset Mirror Systems

  31. Summary • Accelerator commissioned mostly to design goals • Laser heater commissioned and working well (does not salvage OTR screen quantitative use – many MPS problems) • Beam-based alignment converged to required level (should improve after undulators installed due to µ-shielding of Earth’s field) • New LTU wire scanners working routinely • Cavity BPMs commissioned and working fantastically • One undulator field integrals confirmed with beam • 21 undulators installed • Full motion control on all girders (+ 21 undulators) working well • All beam finder wires (BFW) checked out and aligned with beam • BFW’s also used successfully to measure emittance • Full 6x6 feedback running (some over-sensitivity to machine setup still) • Soon hopefully to observe first FEL light

  32. To Do • Tune up and run extended time (2 wks) at 4.3 GeV in preparation for AMO run • Streamline energy change for users and for rapid beam-based alignment • Install, set up, and verify new MPS system (controls) • Commission remaining undulators • Measure FEL gain • Commission FEE • Optimize FEL

  33. LCLS Installation and Commissioning Time-Line InstallUndulators First Light in FEH PPS Cert. LTU/Dump LTU/Und Install X-Rays in NEH First Light in FEE CD-4 (7/31/2010) FEE/NEH Install FEH Hutch BO PEP-II run ends now J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J D M D A 2008 2009 2010 Down Down? PPS LTU/Und Comm. NEH Ops & Commissioning Linac/BC2 Commissioning Re-establish e- to SL2 FEL/FEE Commissioning Nov. 3, 2008

  34. Undulator Trajectory Jitter

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