camilla.compton@LIGO.ORG - posted 17:06, Wednesday 04 June 2025 - last comment - 13:42, Thursday 05 June 2025(84794)
SQZ FIS SRC Detuning Dataset
Vicky, Sheila, Kevin, Camilla
Followed plan outlined in 84762 apart from after each SRCL offset change we moved sqz angle roughly close to max sqz to allow SCAN_SQZANG_KHZ enough range to optimize sqz.
After each 3 minutes of data, Kevin and Vicky took a ADF scan.
Increased NLG (needed to adjust SHG waveplate) by taking OPO trans setpoint from 95uW up to 120uW. Measured NLG = 49 (numbers below) following 76542.
Sheila's fitting found that the SRCL offset (H1:LSC-SRCL1_OFFSET) needed to get a zero degree SRC detuning is -455 counts. Have not accepted in sdf, Sheila added to ISC_LOCK.
Finally we went to FDS and adjusted FC detuning from -34 to -24.
Data attached and saved at /ligo/home/camilla.compton/Documents/sqz/templates/dtt/20250607_SRCdetuning.xml
| Type | Time (UTC) | SRCL | Angle | DTT Ref |
| No SQZ | 21:37:00 - 21:43:00 | N/A | N/A | ref 0 |
| FIS | 22:17:30 - 22:30:30 | -191 | (CLF-) 242 | ref1 |
| FIS | 22:35:00 - 22:38:00 | -90 | (CLF+) 120 | ref2 |
| FIS | 22:49:30 - 22:52:30 | 0 | (CLF+) 172 | ref3 |
| FIS | 23:17:00 - 23:20:00 | -390 | (CLF-) 161 | ref4 |
| FIS | 23:45:00 - 23:48:00 | -455 | (CLF-) 143 | ref5 |
| FDS | ~ 00:00:30 | -455 | (CLF-) 143 | ref6 |
Note that I left the OPO servo gain at -8, but we have previously left it there (83569) or used -12dB for 120uW OPO trans (83370)
| opo_grTrans_ setpoint_uW | Amplified Max | Amplified Min | UnAmp | Dark | NLG (usual) | OPO Gain |
| 120 | 0.018035 | 0.000119507 | 0.000316548 | -2e-5 | 48.9 | -8 |
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Here are the plots of this dataset, showing that our SRCL detuning (in gwinc) would be 50 mrad with no digital offset in the SRCL loop. Kevin tells us that this is a double passed SRCL detuning, so it's really 25 mrad, 1.4 degrees of SRCL detuning.
Edited to add the last point (and have the correct plots).
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