Installation, Commissioning and Operation of the Master Laser Oscillator at FLASH

Installation, Commissioning and Operation of the Master Laser Oscillator at FLASH Patrick Geßler DESY II Timing & Synchronization Workshop, ICTP, Trieste 09.03.2009 V. Arsov, B. Bayer, M. K. Bock, M. Felber, K. Hacker, F. Loehl, B. Lorbeer, F. Ludwig, K-H. Matthiesen, H. Schlarb, B. Schmidt, A. Winter, J. Zemella (Deutsches Elektronen-Synchrotron) S. Schulz, L. Wissmann (Universität Hamburg)

Agenda Overview of the Synchronization System at FLASH Requirements for the Master Laser Oscillator (MLO) 3 Generations of MLOs RF Lock to Master Oscillator Measurements Pitfalls Conclusion 2

Overview of the Synchronization System Laser MLO Narrow Band. 3 MO-RF Distribution Optical link Optical link Optical link <5fs <5fs Other lasers <5fs End-station Direct EOMs/ Seeding LO-RF Direct/ Interferometer Arrival beam/laser Laser pulse DWC/Kly A & φ cavity Desired point-to-point stability ~ 10 fs

Overview of the Synchronization System Final implementation design 4 Free space opt. distribution MLO1 -Switching unit -Invar base plate -Vibration isolated -16 outputs Distr. With EDFA for each link Fiber link stabilization units (max 14) B. Beyer MLO2 -Special passive thermal stabilization -One output for MLO lock based on Sagnac loop at 1.3GHz

Overview of the Synchronization System Laser building EO, HHG and ORS Photo-cathode Laser L2L ACC 1 BC2 MO MLO MLO BPM DWC L2RF BAM CDR ISR Diag. BAM ACC 23 ACC 456 BC3 L2L THz Laser ORS DWC L2RF BPM CDR BAM Experiment sflash Seed LOLA BAM TEO BAM Backbone: beam based stabilization of arrival time Conjunction with high precision synchronization of lasers Synchronization of all timing critical devices ( ~ 14 incl. FLASHII) Point-to-point synchronization ~ 10 fs rms (e- < 30 fs rms) Permanent operation and long term stability /availability investigation ISR PPlaser L2L Seed Beam arrival monitor Laser to laser synchronization Seed Direct laser seeding DWC High precision down converter L2RF Laser to RF conversion L2L Opt-Cross.. 12 FLASH 2 FLASH II L2L SASE-Undulators HHG BAM Distribution RF gun L2L 5

Requirements for the Master Laser Oscillator Mode-Locked Erbium Doped Fiber Laser Pulse Duration <100fs (FWHM) Repetition Rate 216.66MHz Output Power >120mW Integrated Timing Jitter <10fs [10Hz 40MHz] Amplitude Noise <2 x 10-4 [10Hz 1MHz] Reliability / Redundancy 6

1st Generation MLO (Breadboard Version) Original design: J. Chen et. al., Opt. Lett. 32, 1566-1568 (2007) F. Löhl 7

2nd Generation MLO F. Löhl 8

2nd Generation MLO 9 F. Löhl Temp. Stabilization Controller included Variable Set point Stable Ground Plate Distribution included RF Electronic included Motorized Wave Plates

3nd Generation MLO A. Winter 10

3rd Generation MLO Compact Modular Parts Lower Costs Online Spectrometer A. Winter 11

MLO Included Features Overview 1st Generation 2nd Generation 12 3rd Generation Piezo Motorized Translation Stage Optical Monitor Output Electrical Monitor Output Temperature Stabilization Motorized Wave Plates Modular Parts RF Lock Electronic Online Spectrometer

RF Lock to Master Oscillator M. Felber 13

Measurements Noise and Jitter Integrated timing jitter: < 6 fs [10kHz 40 MHz] F. Löhl relative intensity noise: 0.016 % [10 Hz 1MHz] 14

Measurements Spectrum and Pulse Shape (I) For different Pump Laser Power Level Wave Plates optimized for maximum Output Power Similar Spectra / Shapes are Achievable F. Löhl 15

Measurements Spectrum and Shape (II) For different Wave Plate Settings Constant Pump Laser Power of around 890mW F. Löhl 16

Measurements Autocorrelation Different Wave Plate Settings Constant Pump Laser Power Pulse Width: 60 90 fs [FWHM] (depending on Configuration) F. Löhl Different Output Power 17

Measurements Amplitude Stabilization Without Feedback J. Zemella With Feedback 18

Pitfalls Piezo bends due to weight / torque Alignment Make every Parts removable from the top Have enough degrees of Freedom Make the Ground Plate thick / stable enough A Modular Design could cause alignment problems Put the Shutter not before the RF Lock Monitor Port 19

Conclusion The MLO has a strong influence on the complete system Wave plate and pump power settings influence the optical spectrum A high precision diagnostic is needed to investigate the impacts In contrast to stretched pulse lasers, to achieve modelocking wave plate settings have to be changed Different wave plate settings for minimum phase noise and maximum output power Questionable whether two identical MLOs could be set up such that switching has no impact 20

21 Thanks for your attention