Presentation on theme: "Electron Beam Control and Alignment LCLS FEL Undulator Commissioning Workshop UCLA Jan. 19-20, 2004 P. Emma, SLAC Undulator collimation and protection."— Presentation transcript:
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 /2 x1x1x1x1 x2x2x2x2 x3x3x3x3 phase-1 phase-2 phase-1 again halo e beam mm 3 mm 2 mm 2 mm Two-Phase, Two-Plane Collimation, 1½ Times undulator beam pipe 5 mm 2.5 mm edge scattering (also collimation in y and energy – see next slides)
E1E1E1E1 E2E2E2E2 x1x1x1x1 y1y1y1y1 x2x2x2x2 y2y2y2y2 x3x3x3x3 y3y3y3y3 LCLS Collimation Proposal (2 energy, 3 x, and 3 y adjustable collimators) muon shielding undulator x 3 & y 3 optional?
2 nd -order tracking with all collimators closed and big halo 2.5 mm 2-phase, 2-plane, and energy collimation in 2 nd -order well shadowed in x, y, and E Coll. x mm y mmCE1 5.0 - CE2 - CX1 2.0 - CY1 - CX2 - CY2 - CX3?- CY3 -? x,y = 4000 m, E /E = 10% (uniform)
Trajectory through undulator at 14 GeV after 3 passes of BBA procedure. Trajectory After BBA Convergence 2- m BPM resolution 50- m initial BPM & quad offsets 1- m mover backlash 14-7-4.5 GeV 204° 2- m BPM resolution 50- m initial BPM & quad offsets 1- m mover backlash 14-7-4.5 GeV 204° + Quadrupole positions positions o BPM readback e trajectory e trajectory
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- m level. 500 m Verify BBA Convergence by noting orbit change from 14 to 4.5 GeV Before BBA procedure 14.1 GeV 4.5 GeV drop energy, reset launch, note change
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- m level. 20 m Verifying BBA Convergence After BBA procedure drop energy, reset launch, note change 14.1 GeV 4.5 GeV
abort kicker dump stopper-1 stopper-2 120 Hz 10 Hz 1 Hz 276 m undulator Tune-up Dumps in LTU -measurement energy and energy-spread measurement Abort 2 nd bad pulse and tune-up at 120 Hz, 10 Hz, or even 1 Hz, with each rate- limit step allowing closer undulator approach. 30-m undulator extension
G = 110 T/m Track 100 times with: DL2 BPM rms res. = 10 m DL2 BPM rms misa. = 200 m DL2 Quad rms misa. = 200 m Undulator Quad rms misa. = 100 m 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 First beam shot through undulator?
4 collimators (CX1,CY1,CX2,CY2) set tight at 0.5 mm LTU Charge Reducer (spoil beam and collimate hard) 1-mm aluminum screen 20 pC DL2 BPM rms misa. = 200 m, DL2 Quad rms misa. = 200 m Collimators rms misa. = 200 m Undulator aligned 1 nC
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.
0.1-Gauss Earth’s field in x-direction – perfect system, quads on, no steering
0.1-Gauss Earth’s field in x-direction – perfect system, after BBA
0.1-Gauss Earth’s field in x-direction – standard errors, after BBA no Earth’s field – standard errors, after BBA
0.2-Gauss Earth’s field in x-direction – standard errors, after BBA