1. Linac/BC1 Commissioning P
Linac/BC1 Commissioning P. Emma LCLS 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. Straight Ahead Spectrometer Bunch Length Diagnostics
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

5. 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

6. 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

7. 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

8. Set S & X RF ampl. & phase, and chirp for BC1 compression
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

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

10. 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

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

12. 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

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

14. 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˚
Linac-1
new rf
gun
21-1b
21-1d X
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 10 mm

15. Longitudinal Beam-Based Feedback
gun L3 L2 X
DL1
BC1
BC2
DL2 L1
sz1 d1 1 V1
sz2 d2 2 V2 d3 V3 d0 V0
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

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

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

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

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

20. 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

21. 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