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Linac/BC1 Commissioning P. Emma LCLS Injector Commissioning Workshop (ICW) Oct. 10, 2006

This workshop focuses on the commissioning process of the LCLS Injector, specifically the Linac through BC1. It covers the timeline of the commissioning dates, equipment installations, beam measurements, and future plans for the accelerator. Various diagnostics tools are used to measure beam properties such as emittance, energy spread, bunch length, and micro-bunching instability. The workshop also discusses the longitudinal beam-based feedback system and the simulation of slice emittance measurement.

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Linac/BC1 Commissioning P. Emma LCLS Injector Commissioning Workshop (ICW) Oct. 10, 2006

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  1. Linac/BC1 CommissioningP. EmmaLCLS Injector Commissioning Workshop (ICW)Oct. 10, 2006 LCLS

  2. LCLS Injector Commissioning Dates (’06 - ’07) July 24: Sector-20 ready for laser installation Aug. 29:Laser installation complete Dec. 18: Virtual cathode fully characterized (ready to install gun) Dec. 19: RF gun installation starts (10 days) + pre-beam checkout + laser rate switched to 30 Hz (5 days) Dec. 20-Jan. 1:Holidays Jan. 2: VVS’s switched on (RF power available) Jan. 12:First laser UV-light on cathode! Jan. 12-Feb. 4: Electrons in GTL and gun-spect. (RF processing L0a,b, L1, LX) Feb. 5: Beam into L0a, L0b and down to 135-MeV spect. Feb. 20: Beam into main linac (to TD11 dump) ~June: Take beam down full linac (to SL2 stopper)

  3. Injector Through BC1 RF Gun & Solenoid L0a&L0b S-Band Linacs Transverse RF Cavity BC1 (BPM, OTR, collimator) OTR & Wire Scanners Gun Spectrometer L1 S-Band Linac Wire Scanners + OTR Main SLAC Linac 135 MeV 250 MeV TD-11 stopper X-Band RF Straight Ahead Spectrometer Bunch Length Diagnostics 40 m

  4. Dog-Leg-1 up to First L1 RF Section(135 MeV) Bend 2 Matching quads e- Bend 1 OTR Wire-scanner Existing linac Minimize energy spread

  5. L1-Linac (135 to 250 MeV) Cut-off RF sections with new BPMs & quads inserted e- 21-1 klystron, new SS sub-booster Set RF phase (-25º) & voltage for BC1 compression

  6. Accelerator Sections Straightened Coordinate Measurement Machine (CMM) after before (De/e 30%) Four RF sections measured on CMM and straightened (L0a, L0b, L1a, L1b) Jose Chan

  7. BC1 Chicane e- tweaker quad 2 0-30 cm translation stage Bunch length monitors tweaker quad 1 OTR X-band RF collimator BPM Set S & X RF ampl. & phase,and chirp for BC1 compression

  8. Moveable BC1 Chicane BPM critical for energy feedback (20 mm resolution) offset: 0 to 30 cm (23 cm nominal) collimator BPM tweaker quadrupole screen 3-cm contraction (allows passage of 30-GeV beam)

  9. BC1 Dipole Fields are Marginal tracking through fields measured with stretched wire De/e0 1 to 6 % Pole nose pieces in fabrication + tweaker quadrupoles available

  10. Dispersion Correction in SPPS Chicane One linear comb. of 2 tweaker quads

  11. Diagnostic Section After BC1 3 wire-scanners e- Bunch length monitors Insertable stopper (TD11) OTR Future EO? Measure emittance, beta match, bunch length, CSR effects

  12. Tune-up simulations have been run... steering with quad and BPM offsets

  13. rf gun new Linac-1 21-1b 21-1d X Setup of Linac-1, X-band RF Phases 20-mm res. BC1 BPM 20-mm res. BC1 BPM LX RF phase L1 RF phase Linac-1 RF phase scan (X-band off, BC1 at 295 MeV) Linac-X RF phase scan (BC1 at 250 MeV) set phase to -25˚0.5˚ set phase to -160˚0.5˚ • Set L1 and LX RF phase and amplitude • Turn on BC1 energy feedback (if ready) • Use RF-deflector to meas. bunch length (sz1) • Adjust S-band RF phase (0.5˚) to set sz1 195 10mm

  14. sz1 sz2 V0 d0 gun d3 d1 d2 L0 1 2 V1 V2 V3 L2 L3 X L1 DL2 DL1 BC1 BC2 Longitudinal Beam-Based Feedback • Longitudinal feedback (J. Wu): • Maintains DL1 energy, BC1 energy, post-BC1 bunch length • Measures DL1-BPM, BC1-BPM, BC1 bunch-length monitor • Controls L0 and L1 RF amplitude, and L1 RF phase • Use MATLAB in 2007 as temporary slow (~1 Hz) solution

  15. Slice-Emittance Measurement Simulation sy bunch length RF-deflector at 1 MV slice OTR 10 times 135 MeV quad scanned

  16. y-slice-Emittance Measurement in BC1 “Q21201” scanned ±20% 0.3 mm 16 mm

  17. BC1 CSR Effects at 1 nC Full Compression (q= 5.70°) Nominal Bend (q= 4.97°) e/e0 = 1.04 e/e0 = 6.78 sz = 200 mm sz = 12 mm

  18. R56 = 39 mm CSR-Track: De/e0 8% BC1 CSR Effects

  19. Study Micro-bunching Instability at BC1(~Summer 2007) • Scan BC1 bend angle, , to adjust compression factor • Use RF deflectors before and after BC1 to detect bunch density (energy) modulations and compare with micro-bunching gain from theory & simulations 0= 50 m 0= 150 m 0= 300 m  (degrees) Z. Huang

  20. Concluding Remarks • Drive-Laser and gun probably most intensive commissioning areas • Linac through BC1 is mostly magnets, RF, and diagnostics (but most is new) • Need to take beam down full linac (1 km) in order to use RF deflector (LOLA) in sector-29 (test BC1 compression) • Next commissioning phase will start in ~Jan. ’08 with BC2, LTU, undulator, and dump

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