Let's assume the additional flat noise in the ~100 Hz region that might be limiting now (w.r.t. to O4a) is due to OMC length noise. Either the OMC lenght noise is larger than before, and coupling through the residual OMC length RMS noise, or the OMC lock has an offset.

Let's assume that the OMC was locked at the top of the resonance (no offset, to be confirmed with the new demodulation phase).

According to 76137, the two PZT responses are PZT1 = 11.3 nm/V, and PZT2 = 12.7 nm/V.

Following Sheila's note in 30510, the normalized OMC transmission (RIN) is given by [after correcting for a mistake in the coefficient multipling F]

RIN = 1 / (1 + (2 F (x0 + dx)/ lambda)^2 )

where F = 400 is the OMC finesse (76386), x0 is a static lock offset (or equivalent RMS fluctuation) and dx is OMC lenght noise (form example due to dither).

The amplitude of the dither line is 0.23 V peak, corresponding to a dither amplitude (peak) of A = 2.6e-9 m, using the PZT1 calibration above.

The locking error signal is obtained using a length modulation dx = A sin(wt) that gives a RIN = (2F/lambda)^2 A sin(wt) x0, where x0 is the offsetf from resonance of the OMC length. Once demodulated, this gives

OMC-LSC_I = (2F/lambda)^2 A/2 x0 = 7.3e8 error_signal_demodulated_RIN / m (note that 30510 seems to be wrong and missing some factors, thank you Elenna for checking)

This allows me to calibrate the OMC-LSC input signal. The RMS with the OMC locked is 4.7e-5 RIN, corresponding to 6.4e-14 m RMS of residual OMC fluctuation around the lock point.

The flat noise in DARM is about 7e-21 m/rHz. Using the optical gain from the calibration measurement (3.4e6 LSC-DARM_IN cts/m) and the ratio LSC-DARM_IN / OMC_DCPD_NORM = 1.6e-5, I find an optical gain of 2.1e11 RIN/m for OMC-DCPD_NORM

Therefore the noise in DARM corresponds to a OMC-DCPD RIN of 1.5e-9 RIN/rHz

Noise coupling due to the residual OMC length RMS goes like (2F/lambda)^2 x_RMS dx_noise, where x_RMS is now the residual RMS motion computed above. Using this conversion, I found that the excess noise in DARM would correspond to a OMC length noise of 4e-14 m/rHz at 100 Hz. This still seems higher than the expected noise that should be in the 3e-16 m/rHz range (see for example section 8 of T1000276)

Tests to do:

1. check if the new demodulation phase improves anything in DARM
2. scan the OMC lock offset around 0, looking at DARM noise and at the optical gain (for example amplitude of the 410.3 Hz calibration line)
3. change the locking gain to reduce / increase RMS and check DARM

In addition to the BSC10 accelerometer, the amount of floor motion also increases over the past 6 weeks, though not in a sudden fashion.

This does not correspond to the time of the most recent fan swap, judging by fan accelerometers.

Naoki, Daniel, Nutsinee

Today we increased RF6  from -22dBm to -13 dBm and 8 dBm. We saw excess noise at 8 dBm above 300Hz but no excess noise at -13dBm. REF 12 is the squeezing at -22dB before we started the test. Using the time from alog76553. REF9 and REF10 both show squeezing at -13dBm RF6 at different squeeze angle where one has a better sensitivity at low frequency bucket. REF13 shows squeezing at 8dBm RF6. The excess noise above 300Hz cannot be improved with squeeze angle. Investigation is required.

We turned off ADF sqz angle servo during the test. We readjusted the ADF squeeze angle demod phase and accepted the new value in the SDF.

We are parking RF6 at -12dBm. Since Daniel didn't like the unlucky number 13.

SDFs from green initial alignment setpoints

Jenne was pecking away at SDFs (separate alogs), Jennie/Evan did OMC (I took screenshot below), Louis helped with PCal.....Squeezer work is currently active, so will wait for that team to ACCEPT Squeezer!

Pecking away at some SDFs in preparation for OBSERVING tonight:

Easy Ones To ACCEPT: 

• SUSETMY & SUSITMX:  Both of these only had (1) Time Ramp diff  (image#1)

More Involved to ACCEPT:

• SUSETMX:  handful of diffs (image#2), but they were from the recent lock and are confirmed in the ISC_LOCK.py.
• OMC:  Jennie & Evan worked on accepting these (see images 3&4....the latter is accepting the DARM1 filter bank before I could take an SDF screenshot).
• OAF: (image#5)  Jenne said I could ACCEPT these (she couldn't find notes on them in the alog, but she said they should be accepted).
• CALEY:  (image#6)All of these were for PCal--->REVERTED a recent T-Ramp & ACCEPTED the rest of the diffs (which were from Feb).  Louis was looking over my shoulder.

These changes were accpted, but need to be set again after aligning the FC IR transmission.

Noaki added a gain increase to the CAM1 PIT loop for faster convergence.  It should be in the guardian, so I've accepted it in SDF.

DHARD yaw new FM8, alog 76314.

Accepting AS_A offset engagement in Observe.snap.  Values from alog 76500

MICH and SRCL FF SDFs accepted.

alog for MICH: 76460

I think this is the alog for SRCL: 76279

I've accepted dark offsets for the LSC and ASC PDs in SDF for the Observe.snap files. 

TITLE: 03/20 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Commissioning
OUTGOING OPERATOR: Corey
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 13mph Gusts, 10mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.19 μm/s
QUICK SUMMARY:

Engineering Run #16 (ER16) started this morning and Oli handed over an H1 in NLN with Camilla doing a Squeezer measurement and there is a possibility we may try to "squeeze" in a few other measurements (i.e. no squeezing quiet time) before the 6pm target for Observing.

TITLE: 03/20 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
INCOMING OPERATOR: Corey
SHIFT SUMMARY: Commissioning all day with a few locklosses. Relocking took an average of 42ish minutes.
LOG:

15:00 Detector got to NOMINAL_LOW_NOISE
19:25 Lockloss

20:38 NOMINAL_LOW_NOISE
20:42 Lockloss in NOMINAL_LOW_NOISE from commissioners

21:31 NOMINAL_LOW_NOISE                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

Naoki, Nutsinee, Camilla

We turned the SQZ_ANG_ADJUST servo back to it's O3a nominal ADJUST_SQZ_ANG_ADF.  Changed sqzparams.use_sqz_angle_adjust to True and reloaded SQZ_MANAGER and SQZ_ANG_ADJUST.

Set H1:SQZ-ADF_OMC_TRANS_PHASE as 133deg, new scan (as in 76434) running now to check what angle is best for total squeezing.

Naoki, Camilla, Evan, Sheila, Julian, Nutsinee

Many things happened with the squeezer this afternoon. A quick summary is we are back to 5 dB at kHz and we should be able to do this repeatedly. No PSAMs adjustment required at this time.

- When the IFO relocked this afternoon we adjusted ZM5 alignment to optimize ADF trans signal. By doing so we improved both the RF3 and the 42. However this made squeezing worse.

- We adjusted the SQZ angle. We couldn't make it better so we went the other way. This made squeezing worse and ADS TRANS went up with it. Note that this is the IQSUM channel. We didn't think that was a sensible behavior but we've seen it before.

- Sheila and Julian then optimized the crystal tempeature. The NLG for today was 17.3.

- Naoki measured the SQZ IFO sensing matrix. We found a big cross coupling between ZM5 P to AS42 B Y. Other than then everything else was sensible. A new improved sensing matrix has been implemented. 

- We lost hours tracking down why the filter cavity failed to lock on green. A reminder to check SDF next time we run into mysterious problems.

- After everything went back to normal we recovered 5 dB of squeezing. DARM plot said so. BLRMS seemed slightly off. We tried turning the ASC loop off and optimizing the ZM alignment by hand to see if we could do any better than the loop. We couldn't. SQZ IFO ASC loop now works as it should.

- We also optimized the filter cavity offset. Mostly to double checked that we were sitting at a good place. An offset of -28 (where we started) gave the best squeezing at low frequency.

We haven't got to increase CLF power today. 

After a new CLF VCO installed we should revert the CLF sign to make sure everything was the same as before. In theory this shouldn't do anything.