Adding two more times to this list:

• 1386538350 transition from December 13th, with configuration shown in screenshot ( 5 second ramp time) (L2 LOCK FM2, 10 and L1 LOCK FM2,4,10) (L3 master out max = 1e6)
• 1386621508 Decmeber 14th L2 LOCK FM1,2,10 L1 LOCK FM2,6 5 second ramp time, 30000 counts max on ESD
• 1387034098 transition from Decmeber 19th, L2 LOCK FM10 then add FM1+2 2 seconds later, L1 LOCK L FM2,6 (L3 master out max = 6e6)
• 1387140058 transition December 20th, L2 and L1 SWSTATS the same as on the 19th (used guardian NEW_DARM), ESD max just below 2e6
• 1387237746 transition December 21st using guardian (same as 19th and 20th)
•  1388444283 Jan 4th failure, SWSTATs the same as on the 14th.
• 1389131192 today attempt to reproduce Dec 13th transition, except that L2 lock boost was on (FM1 L2 LOCKL) 5 second ramp time (screenshot)

The second screenshot here shows the transitions from Dec 13th, 14th, and 19th. These are three slightly different configuration of the UIM filters and variations on which PUM boosts were on when we made the transition.  On the 14th the oscillation was particularly small, this was with our new UIM filter (FM 2 + 6) and with both PUM boosts on L2 LOCK FM1,2,10 already during the transition.  This is the same configuraition that failed mulitple times in the last two weeks.

Today I went back to three of these transitions, December 14th (1386621508 sucsesful no oscillation) and Jan 4 (1388444283) + Jan 5th (1388520329) which were unsucsesfull attempts. It also seems as though the only change to the filter file since the Dec 14th transition is a change copy the Qprime filter into L1 drivealign, which has not been used in any of these attempts (this can't be used because tidal is routed through drivalign). 

In short, it doesn't seem that we made a mistaken change to any of these settings between December and January which caused the transition to stop working.

I added start and end time windows for the successful transitions in LHO:75631.

Did not fix it, flash rate is several per minute. Opened FRS30147

Back to Observing at 1942 UTC. A fairly fast relock.

Reboot helped...only a little.  

ALSx has progressed from a sliver of light on its camera and 0.0 transmission on ndscope (when starting INCREASE FLASHES at 709am Local), to flashes of light and transmited light on ndscope of 0.25 via INCREASE FLASHES at 730am local.

Had a hand-off to TJ at 8am local.

(Slow) Baby Steps....

Summary: OPO IR and Green cavity scans look bad due to misalignment. Mode-matching into OPO cavity looks good. From today, estimating IR_TEM00 ~ 71% (pitch misaligned), GR_TEM00 ~ 56% (yaw misaligned). 

- We noticed that OPO cavity scans looked bad when we translated the squeezer crystal across the cavity (many peaks, see Oct 17, 2023 73524)
- It worse now than we measured in Dec 2022 66527 ( IR <= 82%, GR < 73% )
- But it was great when we replaced the OPO IR fiber collimator in the September 2022 vent, 64949 - with the new CLF collimator, we measured >94% IR_TEM00 mode-matching before closing HAM7.
- Note: OPO IR and GR mode-matching both look pretty good. The difference in TEM00 efficiency is misalignment. For IR, today we measured IR_TEM20_JAN2024 = 6.4%, which is consistent with Sept 2022 in-chamber IR_TEM20_SEPT2022 = 0.304/(5.48+.304) = 5.3% mismatch (from scope image). That 5% mismatch we measured in-chamber was further consistent with optics lab beam profiles of the new collimator, 63400 "This gives us 95% overlap with the target beam". For opo green, I couldn't see the TEM20 mode on the camera to clearly identify which peak it was, suggests the GR_TEM20 mode mismatch is quite small (thanks team cds for getting the sqzt7 green trans camera online 75286).

See below for details of OPO cavity scans using PZT1, while PZT2 = 0V (clf cmb slow output). We did not try the mode-matching dependence with OPO PZT 2, though that is a thing (62856, this image).

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OPO IR,  4.9 mW into seed fiber:  200 second scan, starting around 1388880769

IR_TRANS  (OPO_IR_TRANS_PD has dark offset -20e-6, ignoring this)
- TRANS_TEM00 =  0.055
- TRANS_TEM01 =  0.01   (pitch misaligned)
- TRANS_TEM02 =  0.005
- Camilla calculated the sum of visible peak heights, peaks_sum = 0.0776 (=0.055+0.01+0.005+0.0019+0.0013+0.0004+0.004)
0.055/(0.055+0.01+0.005+0.0019+0.0013+0.0004+0.004) = 71% matched into TEM00
0.01/(0.055+0.01+0.005+0.0019+0.0013+0.0004+0.004) = 12.8% mis-aligned into TEM01 pitch
0.005/(0.055+0.01+0.005+0.0019+0.0013+0.0004+0.004) = 6.4% mis-matched into TEM02 *** same as Sept 2022 in-chamber mismatch (>94% IR_TEM00 coupling)

IR_REFL (refl dark offset = 30e-6, ignoring this)
- REFL_OFF_RES = 1.195
- REFL_ON_RES_TEM00 = 1.152
- REFL_ON_TEM10 = 1.187
- REFL_ON_TEM20 = 1.191

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OPO GREEN,  2.9 mW into pump fiber:  200 second scan, starting around 1388886980. 

GR_TRANS (trans dark offset = 1 is already subtracted off the following)
- TRANS_TEM00 =  10.66 uW   (85 V PZT1, note PDH 80 MHz sidebands)
- TRANS_TEM01 =   7.4 uW   (90V PZT1, yaw misaligned)
- TRANS_TEM02 =   ??? (maybe 1.02?) uW   (couldn't find TEM20 on camera while scanning)
tem00/peaks_sum =  10.66/(10.66+7.4+1.02) = 56% matched into tem00
tem10/peaks_sum =  7.4/(10.66+7.4+1.02) = 39% misaligned into tem10

GR_REFL (refl dark offset = +0.004, not subtracted yet) (calibrated below into "mW")
- REFL_OFF_RES = 0.35
- REFL_ON_RES_TEM00 = 0.27 around 90V, 0.29 over 100V    different at diff FSR's
- REFL_ON_TEM10 = 0.30 around 90V, 0.31 over 100V    different at diff FSR's
- REFL_ON_TEM20 = ???

Unsure if any of this relates to the recent 5-6 Mpc DARM improvement after the OPO relocked from ~40V to ~95V, LHO:75281, but connecting alogs for reference.

Neither UPS units reported any power issues at the time. Also I was unable to see any problems looking at the fast mains monitor signals in the corner and EX.

Is this additonal nosie at low frequency due to the same non-stationarity we oberved before and we believe is related to the ESD upconversion? Probably not, here's why.

First plot compares the strain spectrum from two times with cold and hot OM2. This confirms Sheila's observation.

The second and third plots are spectrograms of GDS-CALIB_STRAIN during the two periods. Both show non-stationry noise at low frequency. The third plot shows the strain spectrogram normalized to the median of the hot OM2 data: beside the non-stationariity, it looks like the background noise is higher below 30 Hz.

This is confirmed by looking at the BLRMS in the 16-60 Hz region for the two times, as shown in the fourth plot: its higher with cold OM2

Finally, the last plot shows the correlation between the ESD RMS and the strain BLRMS, normalized to the hot OM2 state. There is still a correlation, but it appear again that the cold OM2 state has an additional background noise: when the ESD RMS is att the lower end, the strain BLRMS setlles to higher values

Here is the same comparison, without squeezing.  Using times from  74935 and 74834

This suggests that where cold OM2 seems better than hot OM2 above that is due to the squeezing (and the jitter subtraction Jenne added, which is also on in this plot for cold OM2 but not for hot OM2).  And the additional noise with cold OM2 reaches up to about 45Hz. 

After we optimized ADF demod phase in 74972, the BNS range seems better and consistently 160-165Mpc. The attached plot shows the comparison of OM2 cold/hot with/without SQZ. The OM2 cold with SQZ is measured after optimization of ADF demod phase and other measurements are same as Sheila's previous plots.

This plot supports what Sheila says in the previous alogs.

• The OM2 cold is worse below 40 Hz for both SQZ/no SQZ.  
• Without SQZ, OM2 cold and hot are almost the same above 40 Hz.
• With SQZ, OM2 cold is better between 100-600 Hz, but worse above 1 kHz. This difference could be due to SQZ and we could try to optimize SQZ around 100 Hz with OM2 hot

Echo-ing the above, and summarizing a look at OM2 with sqz in both Sept 2023 and Dec 2023 (running gps times dictionary is attached here).

If we compare the effect of squeezing -- there is higher kHz squeezing efficiency with hot OM2. We can look at either just the darm residuals dB[sqz/unsqz] (top), or do subtraction of non-quantum noise (bottom) which shows that hot OM2 improved the kHz squeezing level by ~0.5 dB at 1.7 kHz (the blue sqz blrms 5). This is consistent with summary pages: SQZ has not reached 4.5 dB since cooling OM2 74861. Possibly suggests better SQZ-OMC mode-matching with hot OM2.

Without squeezing, cold om2 has more optical gain and more low-freq non-quantum noise. Better IFO-OMC mode-matching with cold OM2.

In total, it's almost a wash for kHz sensitivity: heating OM2 loses a few % optical gain, but recovers 0.2-0.5 dB of shot noise squeezing. 

It's worth noting the consistent range increases with SQZ tuning + improvements: even in FDS, there is a non-zero contribution of quantum noise down to almost 50 Hz. For example Naoki's adjustment of sqz angle setpoint on 12/21 74972 improved range, same for Camilla's Jan sqz tuning 75151. Looking at DARM (bottom green/purple traces), these sqz angle tunings reproducibly improved quantum noise between about 60-450 Hz.

Here are some more plots of the times that Vicky plotted above. 

The first attachment is just a DARM comparison with all 4 no sqz times, OM2 cold vs hot in December vs September. 

Comparing OM2 hot September vs December shows that our sensitivity at from 20-40 Hz has gotten worse since September, the MICH coherence seems lower while the jitter and SRCL coherence seem similar.  The same comparison for OM2 cold shows that with OM2 cold our sensitivity has also gotten worse from 15-30 Hz. 

Comparing cold vs hot, in September the MICH coherence did get worse from 60-80 Hz for cold OM2, which might explain the worse sensitivity in that region.  The MICH coherence got better from 20-30 Hz where the sensitivty was better for cold OM2.  The December test had better tuned MICH FF for both hot and cold OM2, so this is the better test of the impact of the curvature change. 

As Gabriele pointed out with his BRUCO, 74886 there is extra coherence with DHARD Y for cold OM2 at the right frequencies to help explain the extra noise.  There isn't much change in the HARD pitch coherence between these December times, but the last attachment here shows a comparison of the HARD Y coherences for hot and cold OM2 in December. 

Peter asked if the difference in coherence with the HARD Yaw ASC was due to a change in the coupling or the control signal. 

Here is a comparison of the control signals with OM2 hot and cold, they look very similar at the frequencies of the coherence.