Installation of new MPR Harald Lück ILIAS WP1 meeting, June 14th 2005

Old MPR: T=1.35% New MPR: T≈ 900ppm

Timeline of MPR exchange 02.05: Opened vacuum vessel & exchanged MPR 03.05: Installed attenuator. Prealigned MPR ….spent some time with aligning 09.05 Ifo aligned and flashing 12.05 stable PR Michelson lock 19.05 1hour 2f lock @ 3.5kHz 22.05 tuned down to 1kHz

Power in PR Cavity Input power: 1.7W incident to MPR. Old MPR (1.35%) ≈ 500W ≈ 1.7 * 4/ 1.35% New MPR: up to 2kW (normally ~1.5kW) Expected PR factor >2000 ↔ 3.4kW Have not yet determined where we lose the power (→Stefan)

Power measurements Power transmitted through mirrors MFE: 13mW/10ppm → 1.3kW MFN: 11mW/10ppm → 1.1W 10ppm for MFN guessed to be the same as MFE BS AR ca. 30mW/44ppm → 1.4kW MCN, MCE very high losses due to lens

Cavity pole measurement Curve fit gives: 15.14 Hz +-0.15 Hz Simulations with 126ppm transm. for MCE/N, 50ppm for MFE/N, and 200ppm for BS/AR. BS thermal lens set to 10k for new configurations give a pole f of 15 Hz.

Simulations Fit pole freq: 141Hz ----------------------------------------------------------- pole freq: 18.4 Hz------------------------------------------------------------ pole freq: 15.0 Hz

Transfer function with old MPR (1.35%) Fit gives 147Hz pole frequency

Wire attenuator, 15µm glas fibre, 0.3% attenuation/round trip Not needed with the present losses

Wire attenuator in front of MPRr

Thermal lensing in BS output mode pattern Directly after relocking f=20km A few minutes after relocking f= 8km

Building up the thermal lens dark port power after relocking for PR and DR Michelson

Increasing ROC heater power dual recycled lock, 1kHz detuned Dark port power 75W 80W 85W 90W 98W PR cavity power