1. Drive Laser Introduction ‘ir’ master oscillator power amplifier chain (MOPA) uses standard chirped pulse amplification scheme (CPA) third harmonic generation (THG) produces required uv for photocathode irradiation ‘ir’ master oscillator is a mode-locked source which is locked to external RF Finesse and Reliability are key – stabilities and shaping readily accommodate technical upgrades

2. LCLS Drive Laser Sections Oscillator Temporal Pulse Shaping Preamplifier Final Amplifier UV Conversion and Pulse Shaping UV Transport (to photocathode) Other Beamlines (EO diagnostic, laser heater,…)

3. Drive Laser Architecture: TiS mode-locked oscillator @ 119 MHz (ext reference) & with few nm bandwidth Temporal Pulse Shaper Temporal Stretcher Spatial filtering & pulse compression UV Conversion and wavelength separation UV Profile Shaping and Transport to Photocathode KHz pulse selection Power amplifier with pumps Relay Imaging Injector Photocathode Preamplifier with pump 120 Hz Pulse selection

4. Probe 1 & oscillator diagnostics oscillator + pump ( few nJ) diagnostic compressor 4x30Hz Splitter shaper + stretcher (estimate combined efficiency 10-15 %) KHz pulse selection Probe 2 & diagnostics cross- correlator preamplifier + pump (few mJ) isolator Probe 3 & preamplifier diagnostics isolator to TiS final amplifier (eg. four arms)

5. Final Amplifier - Plan A: uv generation TiS 30 Hz pump (500 gr mJ) Energy stabilization 30 Hz pump (500 gr mJ) Energy stabilization 30 Hz pump (500 gr mJ) Energy stabilization 30 Hz pump (500 gr mJ) Energy stabilization combiner High power compressor From 4x30 Hz splitter uv profile flattener Multipass amplifier heads (eg. four pass) ir to laser heater blue to EO uv to photocathode 80-100 mJ (3 W @ 30 Hz) 80-100 mJ (12 W @ 120 Hz) 80-100 mJ (6 W @ 60 Hz)

6. Beamlines uv profile flattener uv to photocathode ( mJ) unconverted blue to EO diagnostic unconverted ir to laser heater wavelength separation crystal pair

7. Some Drive Laser Challenges -final amplifier designs : plans A and B (minimize ‘ir’ pulse energy requirements) -STABILITIES such as ‘uv’ pulse energy stability (done at ‘ir’ level) -optimize uv conversion efficiency (‘ir’ temporal shaping effects, pulse quality for unconverted light) -‘ir’ control of uv temporal pulse shape -uv profile shaping and efficient uv transport (final launch phase…) -essential prototyping (FY’04 especially) -readily accommodate repairs and technical upgrades during LCLS operation