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LEReC Retreat Laser System

LEReC Retreat Laser System. b y Patrick Inacker. LEReC Laser Parameters. LEReC Laser Overview. 976nm Pump. 1 W. D C YDF. SC YDF. SC YDF. Mach-Zehnder. 976nm Pump. 704 MHz High-Order-Modelocked Oscillator. EOM. ISO. 60W. 976nm Pump. Non-Critically Phase-Matched LBO Crystal.

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LEReC Retreat Laser System

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  1. LEReC RetreatLaser System by Patrick Inacker

  2. LEReC Laser Parameters

  3. LEReC Laser Overview 976nm Pump 1W DC YDF SC YDF SC YDF Mach-Zehnder 976nm Pump 704 MHz High-Order-Modelocked Oscillator EOM ISO 60W 976nm Pump Non-Critically Phase-MatchedLBO Crystal 160-200W 85µm, 80cm fiber rod PC SHG Power ~22W Polarizer Intensity Control Temporal Shaping PC EOM Power ~16W Power 8-10W

  4. Run18 Highlights • 24/7 capability (Laser is Running continousely. Only turned off for maintenance work) • System protection and monitoring • Increased repeatability and reliability with Plumbing and AC upgrades • Improved Beam Profiles • Improved MPS Extinction ratio with secondary DC Pockels Cell • Intensity Feedback Outstanding Challenges: • High Power Transport and thermal lensing • MPS extinction ratio for 50mA beam operation • Beam Position stabilisation

  5. LEReC Shutdown Schedule

  6. LEReC Shutdown Schedule

  7. LEReC SHG IR Power going into the SHG stage is stable within 2% Peak to Peak Converted, Green Power right after SHG Fluctuates by 10% Peak to Peak Currently waiting on new Critically PM Crystals to arrive. Conversion Efficiency lower than expected for Conversion Technique (~50%, 60-70 expected)

  8. Power Loss before Transport Current Transparancy of the Beam shaping stage is not sufficient Beam Loss due to clipping and absorption Beam Loss ~60%

  9. Transport Transmission Transport had to be tweaked before measurement (Transmission is better than at the end of the run) Trailer – Relay Table Loss = High Order Loss due to distortions in the Trailer Relay Table – Gun Table Loss = Aperture Problems, further High Order Loss, Absorption

  10. Thermal Lensing 10% 0.5W 50% 2.5W 100% 4.8W Thermal lensing still present Beamshape on Gun table no longer distorts, just enlarges Seperated spots on Relay table due to coarse alignment of InterferometerVertical stripes due to clippingin Transport Goal is to make the size increase compensatable with the Zoom Lens

  11. Intensity Stabilisation 90% of Noise is lower than 100Hz. Feedback system with 1 - 2kHz Bandwidth is sufficient for noise supression

  12. Intensity Stabilisation Successfull implementation and commissioning of Laser and e-Beam based Intensity feedback

  13. Critical Questions (From last LEReC Mini-Review (July)) When can we expect stable laser intensity: Both short and long term? When can we expect the thermal lens issues in the temp. shaping crystals to be resolved? Should we expect 10W on the gun table or on the cathode as maximum? What can be done to provide a more uniform laser profile on the gun table 1. Laser intensity fluctuations have been decreased by identifying Humidity fluctuations as main driver Rel. Humidity has been reduced significantly with dedicated dehumidifier. Further modifications to the room AC setup planned. Main part of power fluctuations still originate in SHG stage, not IR. (Still >12% PV Short term) 2,3,4: One Interferometer has been installed and laser beam size adjusted. Transported beamprofile has improved Power level is not sufficient at this point for 50mA operation at 1% QE. 3 Weeks of dedicated time to work on the issue is scheduled during the Shutdown

  14. Conclusion • Appropriate steps have been taken during Run18 which led to improvements • 24/7 capability (Laser is Running continousely now for many weeks at a time) • System protection and monitoring • Increased repeatability and reliability • Improved Beam Profiles • Improved MPS Extinction ratio • Intensity Feedback Outstanding Challenges are being addressed during Shutdown Period • High Power Transport and thermal lensing • MPS extinction ratio for 50mA beam operation • Beam Position stabilisation

  15. Acknowledgements • Laser group: Michiko Minty, Brian Sheehy (retired), Zhi Zhao, Patrick Inacker & Linh Nguyen • Instrumentation, RF and Controls Hardware and Software Engineering • LEReC AIP Project Team under the lead of Alexei Fedotov • CAD Support groups

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