victoriaa.xu@LIGO.ORG - posted 18:58, Wednesday 19 July 2023 - last comment - 16:53, Monday 31 July 2023(71533)
Collecting sqz / no-sqz times at hot, warm, cold, OM2 for quantum noise budgeting
Logging for Brina, who collected a bunch of relevant times to compare sqz vs. no-sqz at different OM2 settings. We aim to do some quantum noise budgeting with these times, to see whether/how much quantum noise is a contributor between 50-150 Hz, and to use the no-sqz data to look at ifo output losses for different OM2 settings. Looking at correlated noise budget from Craig recently, LHO:71333, hopefully we can understand what's going on with quantum noise ~30-200 Hz..
| Date | OM2 temp | gps_start | gps_stop | UTC | alog | ||
| 2023/06/27 | ~56 C | no-sqz | 1371910278 | 1371910578 | 14:11 to 14:16 | 1st hot OM2, LHO:70849 | |
| sqz | 1371910698 | 1371910698 | 14:18 to 14:22 | ||||
| 2023/06/28 | no-sqz | 1372017274 | 1372021147 | 19:54:16 - 20:58:49 | 70930 1-hour no-sqz, hot OM2, xcorr | ||
| sqz | 1372042818 | 1372046418 | 3:00 - 4:00 (6/29) | ||||
| 2023/07/13 | ~22 C | no-sqz | 1373320175 | 1373320818 | 21:49:17- 22:00:00 | cold OM2, LHO:71302 ifo alignment tests | |
| sqz | 1373322138 | 1373322738 | 22:22 - 22:32 | sqz on, AS 36 Q yaw 50,000 | |||
| 2023/07/19 | ~47 C | no-sqz | 1373812338 | 1373812938 | 14:32 - 14:42 | warm OM2 (during pump iss failure, 71497) | |
| sqz | 1373813118 | 1373813118 | 14:45 - 15:00 | (should be more sqz times available) | |||
| 2023/07/19 | ~57 C | no-sqz | 1373839430 | 1373840398 | 22:03:32 - 22:19:40 | 2nd hot OM2, LHO:71518 | |
| sqz | 1373843778 | 1373844498 | 23:16 - 23:28 |
So far I've just started comparing darm spectra (using GDS-CALIB_STRAIN_NOLINES) between the following times, some from the above table:
-- 'cold OM2' uses no-sqz = 1373320175 - 1373320818, fds = 1373322138 - 1373322738
-- 'warm OM2' uses no-sqz = 1373812338 - 1373812938, fds = 1373813118 - 1373814018
-- 'hot OM2 3' uses the recent hot OM2 no-sqz = 1374004600 - 1374005215 (LHO:71591), and fds = 1373984483 - 1373985483 from when range was ~150 this morning. Note FC detuning is -25 Hz for this trace, and many LSC FFs have been retuned here, compared to previous traces.
To start, I looked at compared both the DARM difference with squeezing for different OM2 settings (sqz compared to OM2), and also un-squeezed / squeezed DARMs for different OM2 settings (OM2_compared_to_sqz).
From this second pdf, OM2_compared_to_sqz, a few quick things I notice:
- Hot OM2, >1 kHz (in the shot-noise-limited region at high frequencies), darm looks a bit worse; this is consistent with the decrease in optical gain at hot OM2.
- Hot OM2, ~100 Hz, squeezing seems to give some noticeable improvement around and just above 100 Hz (??). This improvement is not that clear without squeezing. Unclear to me if related to FC detuning or OM2, but I wonder if this ~100Hz noise is in part related to quantum noise..
- Hot OM2, < 100 Hz, low-frequency noise looks much better; the LSC FF tuning seems very effective at improving noise in this configuration.
- At warm OM2, maybe low-frequencies < 100 Hz see some scatter shelves (?), but I might just be seeing things, not totally clear.
Next I'll try to compare this with the quantum noise budget without squeezing, starting by comparing the no-sqz traces to look at IFO shot-noise based output losses, for different OM2s (as Sheila suggested). Ideally this will require independent knowledge of some IFO parameters like the readout angle and the SRCL detuning. Once it makes sense with no-sqz darm, I'll continue to work on making sense of both the full and the semi-classical quantum noise budgets with squeezing injected, and budgeting out the quantum noise contributions to get a sense of whether low-frequency quantum noise (e.g. from sqz misrotations) are plausibly showing up in darm, and what knobs we could turn if so.
Edit: indeed the cold OM2 time had a glitch. Updated plots with the following cold OM2 no-sqz time (different day, early in lock.. but looks more reasonable).
Updated plots: effect of sqz at different OM2s, and sqz vs. no-sqz at different OM2s.
Times used:
cold OM2, no sqz, gps start = 1373371323 (2023-07-14, 12:01:45 UTC)
cold OM2, no sqz, gps stop = 1373372668 (2023-07-14, 12:24:10 UTC)