camilla.compton@LIGO.ORG - posted 12:20, Monday 29 July 2024 - last comment - 14:23, Wednesday 31 July 2024(79344)
OFI KTP Wedge Reinstalled and alignment checked
Sheila, Keita, Betsy, Camilla
New KTP crystal reinstalled, alignment checked, 99.96% transmission and 0.17% rejected. We don't plan to adjust the KPT further and will next remove the FS.
Sheila and I measured the distance between KPT holder with the new crystal (79326) and irises in the optics lab (890mm to left far iris and 880mm to right far iris) and then moved it to HAM5.
We checked the OFI suspension was supported using ther dog camps and finger lockers as in 79315 and then placed the KPT assembly with the teflon barrier in place.
There's not much wiggle room but we pushed the KTP assembly as far toward +Y as we could and then tightened it down.
Then let the OFI suspension hang freely.
We checked SRM osems were good.
Keita and Sheila could see the retroflected beam on the iris after the aux laser. The beam was also hitting the OM1 iris, maybe 0.5mm off in yaw.
In the last power measurements in 79313 we were loosing 25% through OFI and another 15% from lost through incorrect polarization through the TFP.
Today's measurements:
- Before OFI after SRM, 1) mean 5.212mW, stdev 40uW over 10sec 2) lights out mean 5.134mW st 35uW 3) lights out mean 5.098mW stdev 39uW, mean
- Input to HAM6 1) mean 5.173mW stdev 32uW, 2) mean 5.199mW stdev 40uW 3) mean 5.066mW stdev 23.4uW
- SQZ beam power to ZM6: 1) mean 10.09uW stdev 78nW, Blocked/Background 1.175uW stdev 0.3nW, difference 8.915uW 2) mean 9.92uW stdev 64nW, Blocked 1.16uW stdev 0.5nW, difference 8.76uW 3) mean 9.944uW stdev 76nW, Blocked/Background 1.185uW stdev 16nW difference 8.759uW
- Max power out of laser collimator at iris with 220mAmp setting, 38mW+13mW dumped ~50mW
From the mean of these measurements Sheila and Louis calculated the rejected ratio (power sent to ZM6) is 0.17 ± 0.002%. The transmission through to HAM6 is 99.96 ± 1.45%. The sum of these is 100.13%, which is within the margin off error.
Attached is a .txt version of the .py file Sheila did this calculation in.
We realized that we overestimated the errors here so the transmission through to HAM6 is 99.96 ± 0.84%. Rejected ratio (power sent to ZM6) is 0.17 ± 0.001%. Updated code attached and more recent measurements (with swapped FS) in 79383