Reports until 18:58, Wednesday 19 July 2023
H1 SQZ
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    
Comments related to this report
victoriaa.xu@LIGO.ORG - 16:20, Friday 21 July 2023 (71598)ISC

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.

Non-image files attached to this comment
victoriaa.xu@LIGO.ORG - 16:53, Monday 31 July 2023 (71849)

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)

Images attached to this comment