LCLS Commissioning: Results

1
LCLS CommissioningResults PlansP. Emma, for
the LCLS Commissioning TeamDOE Status Meeting
for the LCLSMay 13, 2008
LCLS
Phys. Rev. publication http//prst-ab.aps.org/pd
f/PRSTAB/v11/i3/e030703
2
LCLS Accelerator Layout
6 MeV ?z ? 0.83 mm ?? ? 0.05
250 MeV ?z ? 0.19 mm ?? ? 1.6
4.30 GeV ?z ? 0.022 mm ?? ? 0.71
13.6 GeV ?z ? 0.022 mm ?? ? 0.01
135 MeV ?z ? 0.83 mm ?? ? 0.10
Linac-X L 0.6 m ?rf -160?
Linac-0 L 6 m
rf gun
L0-a,b
Linac-3 L ?550 m ?rf ? 0
Linac-1 L ?9 m ?rf ? -25
Linac-2 L ?330 m ?rf ? -41
25-1a 30-8c
21-3b 24-6d
...existing linac
21-1 b,c,d
undulator L 130 m
X
BC1 L ?6 m R56? -39 mm
BC2 L ?22 m R56? -25 mm
DL1 L ?12 m R56 ?0
DL2 L 275 m R56 ? 0
SLAC linac tunnel
research yard
3
LCLS Injector Layout
6 MeV
OTR screens (7)
YAG screens (7)
Wire scanners (7)
RF Gun
Dipole magnets (8)
Commissioned in 07
Solenoid
Beam stoppers (2)
S-band RF acc. sections (5)
L0a
Gun Spectrometer
L0b
Emittance Screens/Wires
Emittance Screen/Wires
RF Deflector
L1S
2-km point in 3-km SLAC linac
X-band RF acc. section
BC1
135-MeV Spectrometer
TD11 stopper
135 MeV
250 MeV
4
LCLS BC2 Area Layout (sector 24/25)
OTR screens (3)
Collimator jaws (2
Phase monitor cavity (1)
Dipole magnets (4)
Kicker magnet (1)
Transverse RF deflector (1)
S-band RF acc. sections
4 wire-scanners de-scoped
4 wire-scanners in sec-28 (300 m downstream)
CE21
OTR21
BPMS21
BXKIK
PH03
OTR22 (25-3d)
TCAV3 (25-2d)
OTR_TCAV (25-9)
BC2
4.3 GeV
(not to scale)
5
Commissioning Highlights

• Injector commissioning April through August,
  2007 (DONE)
• Phase-II commissioning Dec. ? Complete 3/31/08
  (BC2 Linac)
• Up to 1 nC of bunch charge now available (0.25 nC
  used)
• Great laser uptime (99) and good performance
  (again)
• Emittances ?1 mm after BC1 at 1 nC, 250 MeV
  (fairly routine)
• Routine e- to 14 GeV (24/7 except Wed., 90
  up-time)
• BC1 dipoles chicane motion fixed!
• No emittance growth in X-band RF cavity when best
  steered
• BC2 compression demonstrated (no dipole field
  quality issues)
• Long transverse RF deflector at 5 GeV fully
  operational
• CSR effects measured in BC1 BC2 agree with
  codes so far
• Many beam RF feedback systems running well
• Coherent OTR observed compromises nearly all
  screen data
• Gun RF probes changed in April 08 (allows 120-Hz
  D. Dowell)
• More physicists involved in commissioning in 2008
  (8 ? 15)

6
Design and Typical Measured Parameters
7
Problems/Issues from July 07 DOE Review

• Gun Faraday cup broken
• Gun toroid shorted during installation
• Some YAG screens not installed properly
• BC1 motion control limited (300 mm ? 260 mm)
• Cathode QE about 5-times lower than design
• Some controls tools late (orbit displays,
  fitting, magnet control alarms)
• MCOR power supply ADC readback noise (fixed)
• Laser phase drift and lock trouble until mid-June

ALL FIXED
8
Pre-Beam Check List for BC2/Linac
17 pages, 800 checks - all DONE
polarity checks
DONE
installation orientation
controls check
component bar codes
etc.
etc.
9
Laser Spatial and Temporal Shaping
2007
2007
Temporal shape (6.9 ps FWHM)
Spatial shape on cathode using iris
10
Powerful Scanning/Correlation Application
H. Loos
Quickly minimize emittance by scanning any
parameter
11
b-Matching GUI in Matlab
C. Limborg
Soon to be extended for undulator matching
12
Projected Emittance lt1.2 µm at 1 nC (135 MeV)
s 60 µm
gex 1.07 µm
meets injector goals
gey 1.11 µm
13
Injector Emittance Measured Over 3 Days (0.25 nC)
?gex? 0.91, ?gey? 1.01
OTR screen at 135 MeV
gex
injector is stable
gey
?gex? 0.83, ?gey? 0.83
wire-scanner at 250 MeV after BC1
J. Welch
14
Laser Electron-Based Feedback Systems

• Transverse Loops
• Laser spot on cathode (2)
• Gun launch angle
• Injector trajectory
• X-band cavity position
• Linac trajectory (2 old)
• Undulator traj. (future)

• Longitudinal Loops
• DL1 energy
• BC1 energy
• BC1 bunch length
• BC2 energy
• BC2 bunch length
• Final energy (old loop)

now running
Laser
(bunch length feedback still needs work)
BPMs
CSR detectors
Steering Loop
sz1
sz2
V0
d0
gun
d3
d1
d2
L0
?1
?2
V1
V2
V3
D. Fairley J. Wu J. Frisch
L3
L2
X
L1
DL1
BC1
DL2
BC2
15
BC1 Dipole Field Quality Fixed
Poles were milled off and wider poles were bolted
on and then the fields were shimmed.
fixed
J. Welch, S. DeBarger, N. Li, et al.
16
BC1 Dispersion Measurement Correction
Vary energy before BC1 and read BPMs after BC1 ?
h, h?
17
BC2 Dipole Field Quality OK
Beam energy scans confirm BC2 dipole field
quality meets requirements

3s beam
OK
18
Operating Point Summary Display
Shows operators the main machine parameter
targets and their present settings includes
save/restore files
H.-D. Nuhn
19
BPM-Measured CSR Energy Loss in BC1 at 0.25 nC
(compares well with tracking)
Y. Ding, Z. Huang
Chicane Bend
BPM
20
Hor. CSR Emittance Growth after BC1 (250 MeV,
0.25 nC)
Horizontal emittance after BC1 vs. RF phase
Elegant Meas-1 Meas-2
Data also exists at 1 nC and BC2 data (0.25 nC)
also shows decent results
Elegant
operating point
21
RF Phase and Amplitude Stability (e.g., L0a)
New inj. RF systems meet jitter tolerances
0.05 rms (lt0.07)
RF Feedback Running
20-second sample at 10 Hz
0.05º rms (lt0.07º)
R. Akre, D. Kotturi, J. Craft, V. Pacak, et al.
22
Normalized phase space centroid jitter after BC1
(5 of rms beam size)
RMS AyN 4.1
RMS AxN 4.9
Stability is not so far off of our goals (10)
1-s beam size
D. Ratner
DE/E jitter lt 0.1 DQ/Q jitter lt 2
23
BC2 Chicane in the Linac at 4.3 GeV
Bob Fuller
Chicane length 24 m, 4.3 GeV, 2º bends
24
Bunch Compression Measured after BC2 (0.25 nC)
sz gt 25 mm
L2
25
Longitudinal Phase Space at 14 GeV
PR55
LiTrack simulation
Bunch is Over-Compressed L2 phase -41 deg Chirp
knob -450 MeV
Vertical scale only approx.
measurement
PR55
Bunch is Under-Compressed L2 phase -41
deg Chirp knob 450 MeV
LiTrack simulation
Vertical scale only approx.
measurement
older screen has poor resolution
26
Emittance Measurements at End of Linac Using Wire
Scanners
F.-J. Decker R. Iverson
Emittance measured 300 m after BC2 at 10 GeV with
10 mm bunch length
gey 0.9 mm Q 0.25 nC
Results still variable requires careful work
27
Poor Beam Conditions Also Arise
bad X-profile at end of linac
Possibly the L2 phase drifted into a strong CSR
regime bunch length feedback not running
gex 5.5 mm Q 0.25 nC
28
Emittance Near End of Linac Over a Weekend
gex gey
Emittance near end of linac during weekend run at
0.25 nC, with no tuning
29
2008 Commissioning Goals
DONE
http//www-ssrl.slac.stanford.edu/lcls/internals/c
ommissioning/documents/bc2-commissioninggoals.doc
DONE
DONE
DONE
DONE
DONE
30
LCLS Installation and Commissioning Time-Line
First Light in FEE
First Light in FEH
Und. Seg. Install
PPS Cert. LTU/Dump
LTU/Und/Dump Install
CD-4 (7/31/2010)
X-Rays in NEH
FEE/NEH Install
FEH Hutch BO
FEH Install
PEP-II run ends
now
J
F
M
A
M
J
J
A
S
D
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
O
N
A
A
M
2008
2009 2010
Down
PPS
May 2, 2008
31
LTU/Undulator/FEE/FEL Commissioning
H. Tompkins

• See break-out presentations
• LTU Undulator Commissioning Plans (H.-D. Nuhn)
• FEL/FEE Overview Commissioning Plans (H.
  Tompkins)
• FEE Diagnostics Commissioning (R. Bionta)

32
Problems/Issues

• End-of-linac x-emittance difficult to minimize
  and maintain, especially at 1 nC (needs more work
  m-bunching?)
• Some wire-scanner vibration issues (fixed in
  April 08)
• Most OTR screens are unusable due to COTR (laser
  heater should solve this in FY2009)
• Most linac BPMs need upgrade 16 of 83 done with
  great resolution improvement (on AIP list)
• BC2 bunch length monitor noisy or real jitter
  (need beam synchronous acquisition for RF BPMs
  or m-bunching?)
• Bunch length feedback loops need more wring-out
  (need more time less noisy monitor)

33
Summary

• Drive laser very reliable performs well (great
  team)
• Injector in very good shape runs well after
  setup
• Many measurements made getting to know machine
• Emittances at end of linac difficult to tune and
  maintain, but nice results are possible with
  effort (gey is maybe there?)
• We look forward to next phase (LTU, undulator,
  FEL, ) preparations have begun (plans,
  software, checkout, )
• Thanks to dedicated Commissioning Team
  Controls, RF, Engineering, Operations, ASD,
  maintenance, etc

34
DONE
35
m-Bunching in BC2 May Blow up X-Emittance
OTR screen in BC2
OTR21
gex,y measured with wire-scanners 500-m downbeam
of BC2
gex
gey
36
COTR After BC2
OTR screen just after BC2
OTR22
OTR22
with BC2 screen OUT (m-bunching present COTR!)
with BC2 screen inserted (smoothes m-bunching)
37
FY2009 Commissioning Activities

• Pre-Beam Checkout (Nov-Dec 08) check-list in
  prep.
• Re-establish injector linac beam quality
  (Nov-Dec 08) have experience
• First LTU Commissioning with beam (Jan-Mar 09)
  lots of time
• Undulator/Dump Comm. without undulators
  (Jan-Mar 09)
• Calibrate commission RF BPMs, Loss Monitors,
  BFWs, ADS
• BBA algorithm testing (without segments)
• Install undulator segments (Mar 09, two wks)
  optimize linac again
• First Undulator Segments Commissioning (Mar-Apr
  09)
• Care with first transport to minimize radiation
  on segments
• Full alignment process (BBA, BFWs)
• Commission FEE Diagnostics (Apr-Jun 09)
• Direct Imager, Calorimeter, Slit, Solid
  Attenuator, Gas Attenuator, Gas Detector
• Beam-Based K Measurement Components
• Optimization characterization of SASE (Jun-Jul
  09)
• Optimize linac beam quality (adjust compression,
  emittance tuning, BBA)
• Measure gain length