M. Todd, S. Dwyer, J. Driggers
Summary
| Measurement | Value [uD / W] | Notes |
| Ring Heater Coupling to Substrate Lens | -21.0 +/- 0.3 | relative to modeled coupling, 79 +/- 1 % efficiency compared to predicted 75-80% efficiency from arm cavity measurements. Modeled couplings assuming 100% efficiency report around -26.5 uD/W. |
| SR3 Heater Coupling to Substrate Lens |
ITMX HWS: 4.7 +/- 0.2 ITMY HWS: 4.6 +/- 0.1 |
The ITMX HWS seems to be noisier than ITMY, but give very similar mean estimates. The estimate from Gouy phase measurements is around 5.0 uD/W. |
We turned on inverse ring heater filters to speed up the heating for those (using nominal values for the settings). Because of the weekend mayhem with the earthquakes we did not get a SUPER long HWS transient measuring the full response, but we could get a pretty good estimate of the ring heater effect on the substrate thermal lens without any other heating in the measurement. This is good to compare to modeled values that we have.
I also turned on SR3 heater on Sunday to get estimates of the coupling of SR3 heating to the defocus of SR3. To do this, Jenne helped me untrip a lot of the SU watchdogs for the relevant optics to the HWS. About 3 hours after the SR3 was turned on the watchdogs must have tripped again and misaligned the optics. But fortunately we got the cooldown data for this as well and it's all pretty consistent. These measurement suggest a 4.7 uD/W coupling for SR3 heating, which is very similar to modeled coupling from Gouy phase measurements at different SR3 heater powers.
Overall, while these measurements provide more pieces to the puzzle, they make previous analyses a bit more confusing, requiring some more thought (as usual).
