Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 1 Drive Laser Commissioning results and plans Philippe Hering October 30, 2007 Outline New oscillator Improvements of laser performances New transport beam line Beam stabilization and diagnostics for the transport beam line More remote control

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 2 Great Up Time! 20 weeks of commissioning Three 8 hour downs – Hot swappable parts available now One 3 hour down during a night shift 2 hours per week for locking problems 98% up time !

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 3 New master oscillator from Femtolasers Narrower bandwidth requested to have higher spectral intensity and get a better seeding in the Regen (before FWHM = 30 nm). Crystal is sealed in airtight cavity to avoid contamination (no more weekly cleaning, endurance test made during > 200 hours). Remote starting capability. One pump mirror is remote controlled with picomotors.

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 4 New Femtolock driver for the oscillator Oscillator is first locked to 119 MHz and then to 476 MHz : no more 476 MHz bucket ambiguity. Lock button added to be lock always on the same bucket. RF- locking loop and lock button can be run remotely.

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 5 Reconfiguration of the stretcher Regarding the central wavelength of the Regen seeding beam. Grating and concave/convex mirrors reorientation. Central wavelength of the oscillator Central wavelength of the Regen seeding Bandwidth of the stretcher

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 6 New set-up of the Dazzler DAZZLER Single pass configuration (instead of two before). More accurate spectral shaping with the Dazzler. After further studies from the vendor (Fastlite), quadratic phase correction cannot be added in a big amount and so 4 th and 6 th orders are not possible.  Only spectrum filtering is accurate for our shaping purposes (FWHM < 4 nm).

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 7 Pulse shaping with the Dazzler is made with the spectral filtering parameters : we fix the central wavelength of the Regen seeding beam and shape the spectrum with a 3rd order super-Gaussian. A “hole” in the spectrum can also be done to compensate spectrum distortions in the amplifiers. FWHM = 2 nm

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 8 Change in the REGEN cavity amplifier The Lyot filter (wavelength tuning element) has been removed. One of the end cavity mirror has been changed with an “edge” mirror : low pass filter coating cutting at ~750 nm. Remark : remaining modulations are coming from the fibered input of the spectrometer.

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 9 Improvement of the temporal shape of the pulse Ps pulse duration is obtained by adding quadratic phase with the compressor (distance between gratings shorter than full compression). Super-Gaussian temporal profile is obtained with the Dazzler but only with spectrum shaping (no more with phase orders). You can also dig a “hole” in the spectrum to compensate the spectrum red shift in the multipass amplifiers after the Regen. FWHM = 2 nm

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 10 We measure the temporal beam profile directly in the UV with our scanning cross- correlator.  A flat top spectrum in the IR doesn’t give a flat top temporal profile in the UV because of saturation in the Tripler : asymmetric IR leads to flat top in the UV. FWHM = 2 nm BEFORE Typical temporal shape during last commissioning

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 11 Improvement on the IR input spectrum shape for the Tripler has increased UV yield :  UV yield went up from 15%.  To get the same UV energy in front of the clipping iris, we decided to decrease the IR input ( ~18 mJ instead of ~28 mJ ): main IR amplifier is running with less pumping energy. Save JEDI 2 diodes (half of nominal current value) !!  Safer operation of the Tripler at short pulse duration (<6 ps).

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 12 Beam quality Typical beam image on the clipping iris during last commissioning Changes to be made : Work done on the pulse shaping has improved a little the homogeneity of the beam (to be investigated) ? Replacement of 6 mm thick fused-silica dichroics in UV tripler by 2 mm thick MgF 2 (to lower B-integral) Replacement of all Substrate transmissive fused-silica optics by CaF 2 (to lower fluorescence and absorption). Beam image on the clipping iris before transport after working on the pulse shaping (Preliminary results !)

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 13 Beam stability on the cathode Jitter in x-axis = 35.4  m rms Jiiter in y-axis = 39.2  m rms Beam position on the cathode (on VCC camera) Beam size on the cathode (on VCC camera) Jitter in x-axis = 14.4  m rms Jiiter in y-axis = 18.9  m rms Laser Beam on VCC camera  Instabilities in the electron beam !

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 14 We move the BCS shutter onto the laser table : before it was attached to the side of the table after the mirror folding the beam down through the transport tube. We extended both ends of the vacuum transport tube : upstairs up to the laser table level and downstairs down to the laser box cover. Jitter in x-axis = 11  m rms Jiiter in y-axis = 11  m rms Beam position on the cathode (on VCC camera) Beam size on the cathode (on VCC camera) Jitter in x-axis = 3.6  m rms Jiiter in y-axis = 4.7  m rms  Improvement by a factor of 3 !

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 15 Shot-to-shot energy stability 1.1% charge stability at 1nC Laser energy stability vs. time < 1.5% rms

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 16 Original Transport Layout for 2007 Injector Commissioning F1=200 F2=120 F3=-150 F4=F5=5000 F6=1500

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 17 Changes in the Upstairs Layout No Gaussian Beam Shaper Adjustment of beam size on the cathode is accomplished by changing the magnification of the input telescope and the size of the imaged iris First relay stage (L1 – L3) is removed. Input telescope has 3X higher magnification No vacuum cell is needed Iris is the object plane of the L4 and L5 imaging system Image of the L4-L5 system is virtual L6 relay image the output of the L4 – L5 system to the cathode 4:1. L6 has remote Z-adjustment

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 18 Beam Attenuator Pulse Stacker Iris Wheel Zoom Telescope Insertable Power Meter Insertable Power Meter Active Steering Stabilization New Transport Layout UV Beam Output Vacuum Tube to Gun

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 19 The iris diameter is adjusted by a remotely controlled aperture wheel Laser Beam Wheel houses 12 apertures Beam sizes on cathode mm Smaller diameters can be done Design allows for rapid change for additional apertures Wheel is controlled via Epics

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 20 Option of Focusing the Beam on the Cathode Transport tube Table in the tunnel Photocathode Steering system Active Steering Stabilization F4=F5=5000 F6=1500 L4 L5 L6 Shutter L Cleaning Removable Lens L Cleaning F=3m Z-adjustment of L6 changes the beam size on the cathode

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 21 No Major Changes to Vault Transport M5 L5 M4 L6M3 M2 VC Power Meter Cathode M1 C1 C2 UV plates for Cameras Cathode Cleaning Lens

Philippe Hering October 30, 2007 Drive Laser Commissioning Results and Plans 22 Work in progress before next commissioning Vacuum Transport Cleaning Layout and Alignment of New Optical Transport Install New Controls Hardware Power Meters Cameras and UV plates Iris Wheel Beam quality still needs to be improved Software Installation and Certification of Controls Certification of Laser Operation Training of Operators before LCLS restart