Electron Beam Control and Alignment LCLS FEL Undulator Commissioning Workshop UCLA

1. Electron Beam Control and Alignment LCLS FEL Undulator Commissioning Workshop UCLA Jan. 19-20, 2004 P. Emma, SLAC • Undulator collimation and protection • Verification of the convergence of BBA • Beam abort and tune-up dumps • 15-Å startup for nearly guaranteed FEL gain

2. Two-Phase, Two-Plane Collimation, 1½ Times p/2 ~p/2 3 mm 2.5 mm edge scattering 2 mm halo e- beam undulator beam pipe x1 x2 x3 phase-1 again phase-2 phase-1 (also collimation in y and energy – see next slides)

3. LCLS Collimation Proposal (2 energy, 3 x, and 3 y adjustable collimators) y1 y2 y3 x3 & y3 optional? muon shielding E1 E2 x1 x2 x3 undulator

4. 2-phase, 2-plane, and energy collimation in 2nd-order 2nd-order tracking with all collimators closed and big halo 2.5 mm well shadowed in x, y, and E gex,y = 4000 mm, sE/E = 10% (uniform)

5. + Quadrupole positions e trajectory o BPM readback Trajectory After BBA Convergence • 2-mm BPM resolution • 50-mm initial BPM & quad offsets • 1-mm mover backlash • 14-7-4.5 GeV • Dj204° Trajectory through undulator at 14 GeV after 3 passes of BBA procedure.

6. Verify BBA Convergence by noting orbit change from 14 to 4.5 GeV Before BBA procedure 14.1 GeV drop energy, reset launch, note change 4.5 GeV 500 mm BPM read-backs through undulator at 14 GeV (top) and 4.5 GeV (bottom) after rough steering, but before the BBA procedure. The energy is changed and the launch is re-established. Trajectory changes are expected at the 500-mm level.

7. Verifying BBA Convergence After BBA procedure 14.1 GeV drop energy, reset launch, note change 4.5 GeV 20 mm BPM read-backs through undulator (note scale change) at 14 GeV (top) and 4.5 GeV (bottom) after three rounds of the BBA procedure, where trajectory changes with energy are expected at the 20-mm level.

8. Tune-up Dumps in LTU 120 Hz abort kicker dump 1 Hz 10 Hz stopper-2 stopper-1 276 m undulator e-measurement energy and energy-spread measurement 30-m undulator extension Abort 2nd bad pulse and tune-up at 120 Hz, 10 Hz, or even 1 Hz, with each rate-limit step allowing closer undulator approach.

9. Track 100 times with: • DL2 BPM rms res. = 10 mm • DL2 BPM rms misa. = 200 mm • DL2 Quad rms misa. = 200 mm • Undulator Quad rms misa. = 100 mm • Correct und-launch, then open stopper-2 for one beam shot… • Just 11 of 100 trajectories exceed 2.5 mm within undulator • None exceed 3.5 mm G = 110 T/m First beam shot through undulator?

10. LTU Charge Reducer (spoil beam and collimate hard) 1 nC 4 collimators (CX1,CY1,CX2,CY2) set tight at 0.5 mm 20 pC 1-mm aluminum screen DL2 BPM rms misa. = 200 mm, DL2 Quad rms misa. = 200 mm Collimators rms misa. = 200 mm Undulator aligned

11. Startup at 15 Å with highly degraded e- beam quality FEL gain highly likely in initial commissioning stages – can check out undulator, characterize e- beam, and boot-strap up to shorter wavelengths.

12. 0.1-Gauss Earth’s field in x-direction – perfect system, quads on, no steering

13. 0.1-Gauss Earth’s field in x-direction – perfect system, after BBA

14. 0.1-Gauss Earth’s field in x-direction – standard errors, after BBA no Earth’s field – standard errors, after BBA

15. 0.2-Gauss Earth’s field in x-direction – standard errors, after BBA