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

2. Old MPR: T=1.35%
New MPR: T≈ 900ppm

3. 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
hour 2f 3.5kHz
22.05 tuned down to 1kHz

4. 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)

5. 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

6. Cavity pole measurement
Curve fit gives: Hz 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.

7. Simulations
Fit pole freq: 141Hz pole freq: 18.4 Hz pole freq: 15.0 Hz

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

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

10. Wire attenuator in front of MPRr

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

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

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