Out of Observing 12:00 to 12:05UTC for DARM Offset Steps as described in 70835, back in Observing now with H1:AWC-OM2_TSAMS_POWER_SET set to 4.6, sdf accepted for 2 hour test.
As OM2 warms up, our Kappa C is dropping, and reported range increasing, see plot. Our SQZ BLRMs are reporting better squeezing around 100Hz, visible in DARM too, see attached. Unsure if this is real or due to the calibration changing...
No SQZ time with hot OM2 was taken 14:11 to 14:16 UTC. Plot attached.
Optical gain seem to have reduced by ~2%, cavity pole higher by ~3Hz.
Looking closer at the sqz vs. no-sqz times from Camilla, at hot vs. cold OM2 settings, here are some things I notice:
- SQZ - IFO ASC alignment changes in 1 DOF as OM2 changes, mostly seen in SQZ-ASC_ANG_P_OUTPUT, which beats to track AS_A_RF45 (pitch). (right side ndscope, bottom shows SQZ ASC outputs)
- SQZ improvement looks similar at hot and cold OM2. B/c squeezing vs. no-sqz doesn't look that different, the low-freq improvement in sqz blrms may just be due to the improved technical noise? (red/pink vs. blues)
- Comparing no-sqz at hot vs. cold om2 (red vs. pink):
- < 50 Hz: not much change w/ om2. Many caveats in screenshot, b/c we don't have a great no-sqz reference since 6/21. That means the red no-sqz trace doesn't include all the good FF changes since 6/21, which really improved the < 50 Hz noise. (red v. pink, < 50 Hz)
- kHz: compared to 6/21, either optical gain has increased overall, or else calibration changed? b/c kHz no-sqz shot noise is all around, compared to 6/21. so even as hot OM2 decreased optical gain a few %, it's hard to evaluate the kHz difference just using no-sqz darm (red v. pink, >kHz)
- ~50-200 Hz, this region seems better with OM2 temp changes, compared to cold OM2. it's possible, but not definitely more squeezing here (red v. pink, ~100Hz)
Coherences for a time with lower range (OM2 cold) and higher range (OM2 hot):
https://ldas-jobs.ligo-wa.caltech.edu/~gabriele.vajente/bruco_GDS_1371896710_lower_range/
https://ldas-jobs.ligo-wa.caltech.edu/~gabriele.vajente/bruco_GDS_1371906344_higher_range/
Coherence with jitter is reduced with the hot OM2. Also there is some brodband improvement.
SRCL coherence is slighlty larger when the range is higher, so there might be even more improvement to be gained with a retuned FF.
Also, CHARD_P has larger coherence, while CHARD_Y is slightly better, so I guess the optimal A2L must have changed
Tagging CAL.
This is when the OM2 TSAMS heater first gets turned ON during O4.
As Camilla indicates, the "ON" button was hit -- i.e. H1:AWC-OM2_TSAMS_POWER_SET was set to 4.6 V at
2023-06-27 12:04:02 UTC (05:04:02 PDT)
-- yes, at 5a in the morning on Tuesday prior to Maintenance day; she was on OWL shifts during O4, prior to when owl shifts became remote/on-call.
WE were
back in observing by 2023-06-27 12:05:30 UTC (05:05:30 PDT).
The thermistors on the TSAMS heater unit took much longer to thermalize, with
- H1:AWC-OM2_TSAMS_THERMISTOR_1_TEMPERATURE taking *days* to reach equilibrium 33.0 [deg C].
- H1:AWC-OM2_TSAMS_THERMISTOR_2_TEMPERATURE taking *hours* to reach equilibrium at 56.60 [deg C].
Indeed the calibration measurements taken on Tuesday 2023-06-28 01:50 UTC (2023-06-27 18:50 PDT -- see LHO:70902 and LHO:70908), the lock and observation stretch *after* the above mentioned turn on segment was taken in the middle of the THERMISTOR_2_TEMPERATURE thermalization.
The TSAMS heater remained ON until 15 days later on 2023-07-12 14:48:47 UTC -- LHO:71285.