Electron Beam Control and AlignmentElectron Beam Control and Alignment

LCLS FEL UndulatorLCLS FEL UndulatorCommissioning WorkshopCommissioning Workshop

UCLAUCLAJan. 19-20, 2004Jan. 19-20, 2004

P. Emma, P. Emma, SLACSLAC

Undulator collimation and protectionUndulator collimation and protectionVerification of the convergence of BBAVerification of the convergence of BBABeam abort and tune-up dumpsBeam abort and tune-up dumps15-15-ÅÅ startup for nearly guaranteed FEL gain startup for nearly guaranteed FEL gain

/2/2 /2/2

xx11 xx22 xx33

phase-1phase-1 phase-2phase-2 phase-1 phase-1 againagain

halohalo

ee beam beam

3 mm mm

2 mm2 mm

Two-Phase, Two-Plane Collimation, 1½ TimesTwo-Phase, Two-Plane Collimation, 1½ Times

undulator undulator beam beam pipepipe

2.5 mm5 mmedge edge

scatteringscattering

(also collimation in (also collimation in yy and energy – see next slides) and energy – see next slides)

EE11 EE22 xx11yy11

xx22yy22xx33yy33

LCLS Collimation Proposal (2 energy, 3 LCLS Collimation Proposal (2 energy, 3 xx, and 3 , and 3 yy adjustable collimators) adjustable collimators)

muon muon shieldingshielding

undulatorundulator

xx33 & & yy33

optional?optional?

22ndnd-order tracking -order tracking with all collimators with all collimators closed and big haloclosed and big halo

2.5 mm2.5 mm

2-phase, 2-plane, and energy collimation in 22-phase, 2-plane, and energy collimation in 2ndnd-order-order

well shadowed well shadowed in in xx, , yy, and , and EE

Coll.Coll. xxmmmm

yymmmm

CE1CE1 5.05.0 -CE2CE2 5.05.0 -CX1CX1 2.02.0 -CY1CY1 - 2.02.0CX2CX2 2.02.0 -CY2CY2 - 2.02.0CX3CX3 ?? -CY3CY3 - ??

xx,,yy = 4000 = 4000 m,m,

EE//EE = 10% (uniform) = 10% (uniform)

Trajectory through undulator at 14 GeV after 3 passes of BBA procedure.Trajectory through undulator at 14 GeV after 3 passes of BBA procedure.

Trajectory After BBA ConvergenceTrajectory After BBA Convergence

2-2-mm BPM BPM resolutionresolution50-50-mm initial initial BPM & quad BPM & quad offsetsoffsets1-1-mm mover mover backlashbacklash14-7-4.514-7-4.5 GeV GeV 204°204°

2-2-mm BPM BPM resolutionresolution50-50-mm initial initial BPM & quad BPM & quad offsetsoffsets1-1-mm mover mover backlashbacklash14-7-4.514-7-4.5 GeV GeV 204°204°

++ Quadrupole Quadrupole positionspositions

oo BPM readback BPM readback

ee trajectory trajectory

BPM read-backs through undulator at 14 GeV (top) and 4.5 GeV (bottom) after 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 rough steering, but before the BBA procedure. The energy is changed and the launch is re-established. Trajectory changes are expected at the launch is re-established. Trajectory changes are expected at the 500-500-mm level. level.

500 500 mm

Verify BBA Convergence by noting orbit change from 14 to 4.5 GeVVerify BBA Convergence by noting orbit change from 14 to 4.5 GeV

BeforeBefore BBA procedure BBA procedure

14.1 GeV14.1 GeV

4.5 GeV4.5 GeV

drop energy, drop energy, reset launch, reset launch, note changenote change

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

20 20 mm

Verifying BBA ConvergenceVerifying BBA Convergence

AfterAfter BBA procedure BBA procedure

drop energy, drop energy, reset launch, reset launch, note changenote change

14.1 GeV14.1 GeV

4.5 GeV4.5 GeV

abor

t ki

cker

dum

pab

ort

kick

er d

ump

stop

per-

1st

oppe

r-1

stop

per-

2st

oppe

r-2120 Hz120 Hz

10 Hz10 Hz 1 Hz1 Hz

276 m276 m undulatorundulator

Tune-up Dumps in LTUTune-up Dumps in LTU

-measurement-measurementenergy andenergy andenergy-spread energy-spread measurementmeasurement

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.

30-m undulator 30-m undulator extensionextension

GG = 110 T/m = 110 T/mTrack 100 times with:Track 100 times with:

DL2 BPM rms res. = 10 DL2 BPM rms res. = 10 mmDL2 BPM rms misa. = 200 DL2 BPM rms misa. = 200 mmDL2 Quad rms misa. = 200 DL2 Quad rms misa. = 200 mmUndulator Quad rms misa. = 100 Undulator Quad rms misa. = 100 mm

Correct und-launch, then open stopper-2 for one beam shot… Correct und-launch, then open stopper-2 for one beam shot…

Just Just 11 of 10011 of 100 trajectories exceed trajectories exceed 2.5 mm within undulator2.5 mm within undulatorNoneNone exceed exceed 3.5 mm3.5 mm

First beam First beam shot through shot through undulator?undulator?

4 collimators 4 collimators (CX1,CY1,CX2,CY2) (CX1,CY1,CX2,CY2) set tight at set tight at 0.5 mm0.5 mm

LTU Charge ReducerLTU Charge Reducer(spoil beam and collimate hard)(spoil beam and collimate hard)

1-mm aluminum screen1-mm aluminum screen

20 pC20 pC

DL2 BPM rms misa. = 200 DL2 BPM rms misa. = 200 m,m,DL2 Quad rms misa. = 200 DL2 Quad rms misa. = 200 mmCollimators rms misa. = 200 Collimators rms misa. = 200 mmUndulator alignedUndulator aligned

1 nC1 nC

Startup at 15 Startup at 15 ÅÅ with highly degraded with highly degraded ee beam quality 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 0.1-Gauss Earth’s field in xx-direction – perfect system, quads on, no steering-direction – perfect system, quads on, no steering

0.1-Gauss Earth’s field in 0.1-Gauss Earth’s field in xx-direction – perfect system, after BBA-direction – perfect system, after BBA

0.1-Gauss Earth’s field in 0.1-Gauss Earth’s field in xx-direction – standard errors, after BBA-direction – standard errors, after BBA

no Earth’s field – standard errors, after BBAno Earth’s field – standard errors, after BBA

0.2-Gauss Earth’s field in 0.2-Gauss Earth’s field in xx-direction – standard errors, after BBA-direction – standard errors, after BBA