1. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 1 FEL Commissioning Plans J. Welch, et. al. FEL Commissioning Plans J. Welch, et. al. Accelerator System Breakout Session 10/30/07 LCLS

2. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 2 Linac/BC2 FEE/NEH/X-Ray Tunnel/FEH Installation Timeline of Installation and Commissioning JASONDJFMAMJJASONDJFMAMJJ Linac/BC2 Commissioning 20072008 LTU/Und/Dump Commissioning ASOND 2009 PPS Controls checkout & re-commission Injector Re-commission Inj/BC2 to SL2 FEL/FEE Commissioning …InjectorCommissioning Now PPS 1st Spont. Light 1st NEH Light downtime commissioning LTU/UND/Dump Installation 1st FEL Light installation

3. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 3 FEE/FEL Commissioning Period Starts with Xrays to FEE. Ends with Xrays to NEH. Pre-requisites: BBA working in undulator. Electron beam systems mostly commissioned from Drive Laser to Beam Dump. Simultaneous commissioning of Xray diagnostics and Xray beam. 2 months shared FEL beam with Xray diagnostics 1 month shared with Mirror system

4. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 4 FEL Commissioning - Phase I (~2 months) Using SR only Get “First Light” milestone Establish optical axis Commission X ray diagnostics Characterize SR from individual and multiple segments Measure “photon flux” milestone

5. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 5 X Ray Diagnostics Solid Attenuator Gas Attenuator Slit Start of Experimental Hutches 5 mm diameter collimators Muon Shield Hard X-Ray Offset mirror system Total Energy Thermal Detector WFOV NFOV Gas Detector e-e- Direct Imager Hard x-ray Monochromator (K Spectrometer) Soft X- ray Imager Soft X-Ray Offset mirror system

6. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 6 K Spectrometer/Monochromator 1 eV bandpass at 1st harmonic filters out most of the spontaneous radiation Works only for 8 keV XRays

7. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 7 Soft X-Ray Imager 1% bandpass at first harmonic filters out most of the Spontaneous radiation. works only at 800 eV Multilayer Mirror: Resonant Wavelength: 1.5 nm Relative Bandwidth: 1% Vacuum Chamber X-Ray CCD Camera

8. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 8 “First Light…” …will be seen on a YAG screen of the Direct Imager Shown on right is calculation of Spontaneous Radiation hard X-Rays entering the FEE. Undulator vacuum chamber has realistic “rough” walls for reflection model Light fills the vacuum chamber 8 cm x 6 cm

9. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 9 Establish Optical Axis Want to align gas attenuator and gas detector  3 mm apertures, fixed mask, and mirror systems, to a common optical axis co-linear with the xray beam axis. Need to determine the central ray of Xray beam. Three possible methods: 1.Use the K measurement crystal followed by the direct imager to find the spatial center of the filtered 1st harmonic. 2.Make a small hole with variable slits and scan the slit center while measuring the spectrum with the K measurement “spectrometer”. The central ray is coincident with the maximum spectral shift. 3.Use the Soft Xray imager and a low energy beam to find the spatial center of the filtered 1st harmonic. This has been simulated.

10. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 10 Central Ray Using K Spectrometer ~1 eV BW, 8 keV, pinhole. Fluxview calculation, 1st segment P. StefanOff energy

11. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 11 Finding the Central Ray and SASE At low energy, use the Soft X-Ray Imager FEL Beam 1% BW Filtered SRRAW XRays

12. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 12 Measure SR from Undulator Segments Measure what? Central ray position, as above, and relate it to local BPM readings. Average spectrum using K monochromator Spatial profile, using the Direct Imager. K measurement? Will we have time? Why? Provides a basis for future comparisons. Establishes all segments are producing Xrays as expected and are free from anomolies.

13. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 13 K Measurement: 2-Segment Scheme Measure synchrotron radiation spectrum produced by two undulator segments, and scan K of one segment Other schemes compare spectra from individual segments. (Pinhole technique, angle-integrated edge measurement, reference undulator) K’s are matched when spectrum has the steepest slope on high energy side of 1st harmonic peak. Match segments pairwise until all segments are measured. undulator segments (33 total) segments under test

14. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 14 FEL Commissioning - Phase II (1 month) Generate and detect FEL Radiation at low energy Find SASE signal Measure Gain Curves Optimize gain Steer FEL Radiation thru center of C1 5 mm aperture, then M1-Soft Change energies when time allows

15. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 15 Desirable measurements as function of position along undulator : Intensity (L G, Saturation) Spectral distribution Bunching Desirable measurements after undulator : Pulse length Spatial shape and centroid Divergence Desirable measurements as function of position along undulator : Intensity (L G, Saturation) Spectral distribution Bunching Desirable measurements after undulator : Pulse length Spatial shape and centroid Divergence FEL Measurements Undulator Regime Exponential Gain Regime Saturation 1 % of X-Ray Pulse Electron Bunch Micro-Bunching

16. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 16 Gain Curve Measurement (1) 1.Trajectory bump method FEL Radiation alone is “turned off” by distorting orbit with a single corrector. Spontaneous radiation is more or less constant. If filtered, FEL will dominate over SR. orbit vacuum chamber kick undulator segments (all in) XRays

17. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 17 Gain Curve Measurement (2) Variable length undulator method SR and FEL radiation are both “turned off” by removing segments

18. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 18 Gain Optimization (just words) beta matching studies bunch compression studies laser heater studies trajectory sensitivity studies taper studies...

19. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 19 Offset Mirror Systems Precision steer the FEL beam onto the Mirror system axis and keep it there. FEL beam/mirror steering studies FEL or Mirror axis Pointing system feedback commissioning. Get high energy FEL to work. Stabilize and improve the beam quality. P P P P P P Precision steer FEL beam to center of radiation protection collimator C1 and M1-Soft. Steering feedback?

20. James Welch FACWelch@SLAC.Stanford.edu October 30, 2007 20 Summary Plans for intital FEL commissioning are shaping up. Diagnostics tools are at, or passed, the concept phase Methods for finding SASE and the central rays are identified. Methods for gain curve measurements have been worked out Overall planned duration is very short Considerable additional commissioning time will be needed especially for 0.15 nm radiation.