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LIGO II Pre-stabilized Laser System Design Requirements and Conceptual Design

LIGO II Pre-stabilized Laser System Design Requirements and Conceptual Design. David Ottaway, Todd Rutherford, Rick Savage, Peter Veitch, and Benno Willke LIGO Science Collaboration Meeting Hanford, WA August 15-17, 2000. LIGO II PSL Design Requirements. Output power delivered to IO system

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LIGO II Pre-stabilized Laser System Design Requirements and Conceptual Design

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  1. LIGO II Pre-stabilized Laser SystemDesign Requirements and Conceptual Design David Ottaway, Todd Rutherford, Rick Savage, Peter Veitch, and Benno WillkeLIGO Science Collaboration MeetingHanford, WAAugust 15-17, 2000

  2. LIGO II PSLDesign Requirements • Output power delivered to IO system • 150 watts in a circular TEM00 mode (8.5 W for LIGO I) • In-band relative intensity noise • 3 x 10-9 1/rtHz (1 x 10-8 for LIGO I) • Relative intensity noise at GW modulation frequency • ASD < 1.005 times shot noise for 5 W of light (600 mW for LIGO I) • Frequency fluctuations at PSL output • 100 mHz/rtHz at 100 Hz (same as for LIGO I) • 10 mHz/rtHz at 1 kHz and above (same as for LIGO I) • Wideband and Tidal Actuators (same as for LIGO I) LSC Meeting - Hanford 8/00

  3. Status of LIGO I PSL Performance • Output power delivered to IO system • 6-8 wattts • no serious effort made to optimize operating parameters – MO and PA current and temperature • Alignment and modematching into power amplifier required • Mountig of EOM between MO and PA complicates alignment • LHO system operated continuously for > 18 months • In-band relative intensity noise • Staiblization AFTER modecleaner not yet attempted • Photodetector and preamplifier not yet designed or fabricated • Currrent shunt actuator designed and implemented LSC Meeting - Hanford 8/00

  4. LIGO I PSL Status (cont.) • Relative power fluctuations at GW modulation freq. • Pre-modecleaner • Operating continuously for > 18 months at LHO • Sensitive to atmospheric pressure fluctuations • Sensitive to acoustics • Sealing or housing inside a sealed chamber planned • Finesse ~ 2-3 times too low • Frequency fluctuations • Approaching requirements • Optical layout optimization • Acoustic shielding • Pick off reference cavity beam AFTER PMC – P. King testing on hold LSC Meeting - Hanford 8/00

  5. Frequency Servo Performance N. Mavalvala P. Fritschel LSC Meeting - Hanford 8/00

  6. LIGO II PSL Conceptual Design • Strategy • Develop ONE concept even though numerous options exist and requirements are still in a state of flux • Propose design for LIGO II laser even though LIGO is pursuing procurement from commercial vendor. • Build on experience with LIGO I PSL • Utilize hardware and software from LIGO I PSL (already paid for) • Goals • Demonstrate that requirements are reasonable and realizable • Provide Peter King and Rich Abbott information required for cost estimate • Provide Gary Sanders conceptual design description for NSF proposal. LSC Meeting - Hanford 8/00

  7. LIGO II PSL Concept Overview • Laser source (Todd Rutherford) • LIGO I 10-W laser modified to produce 20 watts as front end. • Two-stages of zig-zag slab amplifiers • Laser pre-modecleaner (LPMC) between front end and amplifiers • Itensity stabilization (David Ottaway) • LPMC and PMC • Circulating powers about 10 times LIGO I • Pwr. Stab. PD inside the vacuum envelope • Frequency stabilization • Beam for reference cavity sampled AFTER PMC • All hardware and software same as for LIGO I LSC Meeting - Hanford 8/00

  8. Wideband actuator • Same as for LIGO I PSL • VCO range reduced to enable noise reduction • Tidal acutator • Same as for LIGO I PSL • Diagnostic modes • Removed from PSL scope • Some power modulation may be achievable via power stabilization loop LSC Meeting - Hanford 8/00

  9. LIGO II PSL Concept (cont.) • New Features • Laser Room similar to Livingston enclosure • Electronics racks moved outside room • > 20 dB acoustic attenuation • Controlled thermal environment • Controlled access • Active vibration isolation system for IO/PSL optical table • Output power reduction with complementary increase in power to reference cavity and PMC RFPDs • Laser power supplies located outside Laser Room near other eclectronics racks • Chillers for lasers located remotely in Mechanical Rooms LSC Meeting - Hanford 8/00

  10. LIGO II PSL Upgrade Options • Laser source (Peter Veitch) • Injection-locked oscillator for front end • Stable-unstable resonators • Frequency stabilization LSC Meeting - Hanford 8/00

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