1. Linac Diagnostics Commissioning Experience
LCLS DOE Review
July 11, 2007
Henrik Loos, for the LCLS Commissioning Team
Diagnostics overview
BPMs, Toroids, FCs
Wire Scanners
YAG/OTR Profile Monitors
Transverse Cavity
Bunch Length Monitors

2. LCLS Diagnostics Tasks
Charge
Toroids (Gun, Inj, BC, Und)
Faraday cups (Gun & Inj)
Trajectory & energy
Stripline BPMs (Gun, Inj, Linac)
Profile monitors (Inj), compare position with alignment laser
Transverse emittance & energy spread
Wire scanners
YAG screen (Gun, Inj)
OTR screens (Inj, Linac)
Bunch length
Transverse cavity + OTR (Inj, Linac)
Coherent radiation power (BC)
Slice measurements
Horizontal emittance
T-cavity + quad + OTR
Vertical Emittance
OTR in dispersive beam line + quad
Energy spread
T-cavity + OTR in dispersive beam line

3. Diagnostics Overview OTR screens (7) YAG screens (7) Wire scanners (7)
Dipole magnets (8)
Beam stoppers (2)
S-band RF acc. sections (5)
RF Gun
Gun
Solenoid
Spectrometer RF
Deflector
X-band RF
acc. section
BC1

4. Beam Position and Charge Monitors
21 BPMs functional
BPM polarity and scale checked with correctors and model
5 current monitors and 1 Faraday cup operational
EPICS Displays

5. BPM Position and Charge Online Display

6. BPM Resolution Test Synchronous acquisition of all BPM positions
Fit of one BPM position vs. position calculated from all others
Specification < 10μm
Typical < 5μm

7. Charge Calibration First toroid and FC after gun not functional
Use FC in gun spectrometer to calibrate sum signal from first BPM

8. Wire Scanners 7 wire scanners installed
5 photo-multipliers and 4 ion chambers working
EPICS Displays

9. Wire Scanner User Interface
Raw Synchronized Data
PMT, Toroid, BPM Selection
Processed Profile

10. Wire Scanner Data Correction
No Correction
Charge Correction
Charge & Jitter Correction

11. Wire Scanner Status All wire scanners are working
WS orientation and calibration cross-checked with correctors, BPMs and OTRs
Some wire cards rotated, fixed in software
Charge and jitter correction commissioned
PMT/Ion chambers need work
Some WS give weak signals on PMTs
Ion chambers close to TD11 dump saturate and have large background

12. YAG/OTR Profile Monitors
7 YAG and 7 OTR screens installed
14 optics boxes commissioned
Control for screen insertion, 2 neutral density filters, screen and reticle illumination functional
EPICS Displays

13. Profile Monitor Calibration
Measure known diameter of YAG crystal on CCD image
Verify calibration of reticle image
Use reticle for calibration if screen edge outside FOV

14. OTR Screen Calibration Test
Screen calibration agrees within 2.5% with prediction from corrector scan and model
Best focus close to screen center
Constant beam size within +- 1mm

15. OTR Screen vs. Wire Scanner
Same beam size from WS and OTR
Beam shape shows good agreement
Gaussian Fits

16. Coherent Optical Transition Radiation
Gaussian profile from WS
Fluctuating profile from OTR with compressed beam
OTR screen not usable for emittance measurement of highly compressed beam

17. Transverse Deflecting Cavity
Software for automated time scale calibration and bunch length measurement

18. BL11 – Coherent Edge Radiation
Bunch Length Monitors
BL12 – Ceramic Gap
BL11 – Coherent Edge Radiation
Ceramic Gap
Waveguide
GHz Diode Detectors

19. Edge Radiation Monitor
Bunch Length Monitors
Both bunch length monitors installed
Signal from wave guide diodes and pyroelectric detectors available
All signals show strong correlation with accelerator phase and bunch compression
Absolute calibration with TCAV in S29 to be done
Edge Radiation Monitor
Ceramic Gap Monitor
100 GHz Diode
300 GHz Diode

20. High Level Applications - Emittance
Methods
Multi screen
Quad scan
Devices
OTR
Wire scanner
Features
Scans automatic & manual
Data & config files
1 button -> logbook
Average & raw data
Phase space plot
Slice emittance

21. High Level Applications – Correlation Plot
Purpose
Measure accelerator parameters vs. settings
Use EPICS and results from HLA
Features
Scans 1 or 2 control variables
Reads any process variable plus
OTR/YAG screens
Wire scan
Emittance
Synchronous acquisition
2D data plots
Different fit options

22. Summary Most of the diagnostics is installed and commissioned
Diagnostics is integrated into control system and being used by high level applications
Bunch length monitors need more commissioning
Some diagnostics in gun region (YAG, FC, IM) needs work in next down time
Observation of coherent phenomena on OTR for ultra-short bunches: Future problems for OTR beyond BC2?