C.Swain, L.Dartez, J.Kissel

Finished characterizing the spare whitening chassis, OMC DCPD S2300004.

• Transfer functions and residuals shown in:
  • 2023-06-29_OMCDCPDWhitening_report.pdf 
• Output Noise Measurements shown in:
  • DCPDA: 2023-07-07_OMC_DCPDA_Whitening_Chassis_S2300004_Output_Referred_Voltage_Noise.pdf 
  • DCPDB: 2023-07-07_OMC_DCPDB_Whitening_Chassis_S2300004_Output_Referred_Voltage_Noise.pdf
• Noise comparison between S2300004 and S2300003, gathered by Jeff Kissel - S2300003 Noise Data - shown in:
  • 2023-07-10_OMC_DCPD_Whitening_Chassis_Noise_Floor_Comparison_Results.pdf

The last two files are text documents containing updated notes on gathering the transfer function measurement data and noise measurement data of the whitening chassis, respectively. 

[Daniel, Keita, Sheila, Jenne]

After checking when we do / don't offload the OM suspensions, we only offload them in the MICH and SRY initial alignment states, after they have completed successfully.  We do not offload them in DRMI ASC. 

Also, from Ibrahim's alog 71183, we haven't succeeded with MICH or SRY initial alignment since *before* we turned on the OM2 heater.  So, probably we're just in a situation where OM2 needs to be moved by hand to compensate for some different alignment due to its being warmer to get the beam more centered on the AS, and then things will be fine.  MICH will lock and align during the initial alignment sequence, and then OM1 and OM2 will be offloaded.  We will probably also need to help OM2 by hand again after we turn off the heater.

If this is not sufficient to ameliorate most of our problems, then we should engage and offload some AS WFS centering before attempting to lock MICH.  There are two ways we could do this, either add AS WFS centering and offloading to the Input Align (or PRX) states, or we could insert the AS_Single_bounce alignment and offloading states after PRX and before PREP_for_MICH.  Since these options are before the BS is aligned (which happens after MICH is locked), we'd be offloading OM1 and OM2 under the assumption that the BS alignment is 'close' (and OM1 and OM2 will get re-offloaded again after the BS is fully aligned, so it doesn't matter at these states if they're not perfect).  Also though, the BS has to be quite close for the Yarm green initial alignment to have succeeded, so the assumption that the BS is 'close' is probably fine. 

For now, I'm not going to make any changes to the guardian, and we'll see how initial alignment goes after hand-aligning OM2. 

Tue Jul 11 10:06:01 2023 INFO: Fill completed in 6min 0secs

Around 9am I turned the corner station dust monitor pump back on. I had powered it down last Friday with concerns of overheating. This pump runs hotter than the End station pumps and is withing operating temps.

J. Kissel

Executive Summary: The current, 2023-03-21, OMC DCPD electronics' compensation filters "NewV2A" and "NewAW" are still very accurately compensating for the frequency dependence of the analog electronics' response, so this is NOT a contributing factor to the complexity of the low frequency sensing function AND the response continues to be stable in time.

As a part of the continued investigation as to why the low-frequency sensing function is so complicated (see page 1 of H1_calibration_report_20230628T015112Z.pdf from LHO:70908 report of the measurement from LHO:70902), I wanted to rule out any possibility that the OMC DCPD electronics' analog response had changed (like we'd seen during the initial 2022 "burn in" period of the electronics -- see the 2022 data within 20230310_H1_DCPDTransimpedanceAmp_OMCA_timeratio.pdf from LHO:68167).

See the first and second attachments. These show a comparison of the remote excitations of the OMC DCPD electronics chain between the second set of "while in nominal low noise" measurements from 2023-04-03 (i.e. from LHO:68377) in BLUE and the ones taken this morning with no light on the DCPDs (the IMC was OFFLINE) in RED. 

This transfer function, driving through the electronics *and* the compensation for those electronics' response continues to behave as "flat below 500 Hz." Thus the compensation is still doing an excellent job at compensating for the low-frequency response of the electronics. In fact, with no light on the DCPDs, the data is cleaner below 100 Hz.

This puts 3 data points "on the board" where the response has not changed within the precision / accuracy that matters:
    - 2023-03-10
    - 2023-04-03
    - 2023-07-11
If we agree that three makes a pattern, then we shouldn't need to worry about this again until the electronics change. Since we're experimentalists, I'll probably measure again in a month or two just to confirm.

For future Jeff:
(1) You can do this in ~20 minutes on a Tuesday morning.
(2) Take IMC to OFFLINE, or if folks need the beam, make sure the fast shutter is closed.
(3) Open templates from 
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/SensingFunction/OMCA/Data/
        20230711_H1_TIAxWC_OMCA_S2100832_S2300003_DCPDA_RemoteTestChainEXC.xml
        20230711_H1_TIAxWC_OMCA_S2100832_S2300003_DCPDB_RemoteTestChainEXC.xml
and update the references.
(4) One DCPD at a time, turn ON the analog relay to allow the H1:OMC-TEST_DCPD_EXC to head out through the DAC, the whitening chassis, and into the TEST input of the TIA. These relays, H1:OMC-DCPD_A_RELAYSET and H1:OMC-DCPD_B_RELAYSET can be found from the sitemap > OMC control > "sum "norm" "null" sub screen > Relays screen.
(5) Hit go on the measurement.
(6) Restore the relays to OFF.
Done!

TITLE: 07/11 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 14mph Gusts, 11mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.05 μm/s
QUICK SUMMARY: 13:48 hour lock just ended so we can begin maintenance work. SUS in-lock charge measurements successfully ran without killing the lock.

TITLE: 07/11 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Commissioning
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 15mph Gusts, 12mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.05 μm/s 
QUICK SUMMARY:

14:20 UTC Magnetic injections started
14:21 UTC Dropped out of OBSERVING and into Comissioning.
Been pretty quiet.
SEC_ESD_INJECTIONS are still running.
Current IFO Status: NOMINAL_LOW_NOISE Not Observing, and prepairing for 4 hours of down time for Maintenance Day

Current IFO Status: NOMINAL_LOW_NOISE & OBSERVING
Range : 140.9.Mpc
The wind has died down and the Violins look good.

TITLE: 07/11 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 138Mpc
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 23mph Gusts, 18mph 5min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.05 μm/s
QUICK SUMMARY:
Winds have been up and down tonight with some gusts above 30mph.

Current IFO Status: NOMINAL_LOW_NOISE & OBSERVING for 6 Hours

TITLE: 07/11 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 137Mpc
SHIFT SUMMARY:

IFO is in NLN and OBSERVING as of 1:17 UTC. Violins have been coming down nicely since the earthquake and the lock acquisition.

LOG:                                                                                                                                                                                                                                                                                                

There has been excess DARM noise mostly in 20 to 40 Hz region at LHO recently. Gabriele and others have been investigating the potential role of 2.6 Hz peak in this noise, for more info on their work please see alogs 71005, 71092, 71205.  This noise can be seen as excess glitches in 20-40 Hz band as seen in the first plot for July 2. 

This noise kinda got worse June 22 onwards can be seen in the glitchgram of the day as an increase in glitches few hours before the end of the day. Marissa pointed out during a Detchar call that GravitySpy has been classifying a lot of glitches as Fast Scattering. The time-frequency spectrograms  (second file) of these glitches do not look very similar to the fast scatter at LLO but as long as they are high frequency (which these are) and could be some form of scatter, this classification seems apt. 

The third plot below shows all the omicron triggers between Jun 30 and Jul 3 and the fourth plot shows those classified as Fast Scattering by Gravityspy above a confidence of 0.9. Furthermore the fifth plot shows an increase in the number of glitches classified as Fast Scattering after June 22.

From the Q scan (sixth figure), we can see that this is ~5 Hz Fast Scatter, which means the scattering surface is moving at ~ 2.5 Hz. When microseism is low, anthropogenic  motion at f Hz, shows up as fast scatter at 2f Hz. More details on this noise modeling can be found in G2300482.  Sixth figure is actual noise, seventh figure is a model based on 2.5 Hz motion. 

Assuming the peak frequency to be 30 Hz, the scattering surface is moving at 15 µm/s.

Substituting V and f = 2.5 in , V_scatter = A_scatterω_scatter 

We get A_scatter ~ 0.96 µm.  Somewhere there is a scattering surface moving about 2 microns peak to peak, at 2.5 (or 2.6) Hz (it's very difficult to distinguish between 2.5 Hz and 2.6 Hz in the Q scan) causing this noise. Not sure if we have had injections around this frequency in the ACBs.

Today we had SQZ ASC issue again. The first attached figure shows the related signals when SQZ ASC ran away. It seems that the ANG P/Y ran away for some reason and the SQZ-ASC_TRIGGER_INMON got down below the threshold and the SQZ ASC was turned off.

To avoid this, I reduced the gain of ANG P/Y by 20dB. I put -20dB in FM5 of ANG P/Y. The second attached figure shows the same signals with reduced ANG P/Y gain. The ANG P/Y ran away for the first 10 minutes, but the drift is much less and the ANG P/Y came back to reasonable value after that. 

I still don't understand the reason of the drift (related to beam spot control?), but at least SQZ ASC can be engaged without running away now.

IFO is in NLN and OBSERVING for 1:41 hrs (since 1:17 UTC). Nothing else of note.

TITLE: 07/09 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 141Mpc
SHIFT SUMMARY:

IFO is LOCKED and OBSERVING - now for 48 hours and 35 minutes and counting, O4 record!

Other:

Squeezer unlocked without unlocking full IFO, which knocked us out of observing briefly, but quickly and automatically recovered within three minutes, putting us back in observing. This resulted in a data gap in GWISTAT during this time (4:34:38 UTC to 4:37:12 UTC), which was communicated on the RRT O4 mattermost channel and on teamspeak upon clarification.

LOG:

Every lockloss after Tuesday maintenance last week has run up the violins.

Even though before this last lockloss the fundamental mode was very low (but harmonics were still elevated) the IFO has relocked with very high violins. Attached is  the violins screen and DARM at the LOWNOISE ISC_STATES before we get to NLN.

It seems that the OMC single bounce mode matching is better with hot OM2 than it was with the similar measurement 70409

Daniel turned off the sidebands and manually aligned the locked OMC. 

• locked OMC, sidebands off: 1371920979 to 1371921080 (16.15 mA OMC DCPD sum, OMC refl is roughly 1.84mW average, minimum roughly 1.76mW)
• unlocked OMC sidebands off: 1371921192 to 1371921317 (OMC REFL rough average 22.6mW)
• scan time: 1371921531 duration 100 seconds.  screenshot attached.  from cursor 00 mode 16.28mA 20/02 0.73mA) 

The good: we now have access to longer segments of observing-quality data and can get a clearer look at narrow spectral artifacts. It looks like the line and comb situation is fairly stable and consistent with previous observations in smaller data sets. We're generally not seeing new problems arising, but are better understanding the existing problems and their scope.

The bad: Combs are more pervasive than previously known, especially at intermediate and high frequencies. In particular, a large number of spectral bins are contaminated by a set of ~9.47 Hz combs over a wide spectral range, which is problematic for CW searches.

The details:

The 4.98423 Hz comb is still present and clearly visible at low frequencies. The ~9.47 Hz combs (specifically 9.47431, 9.475383, and 9.480526 Hz) are weaker, but the larger data set reveals that they are more pervasive. They contaminate a spectral region spanning from about 200 Hz to 930 Hz (98th harmonic). There are 3 distinct combs involved in this structure; the triple peak can only be seen at high spectral resolution.

There is also a 29.969515 Hz comb which is visible up to its 60th harmonic at about 1800 Hz, and a 99.99864 Hz comb which is visible up to at least 2 kHz.

Coherence information:

We also have averaged coherence data over the same time period. As a reminder, Fscan tracks a limited set of high-priority channels and not the full DetChar list.

• Many of the combs (4.98 Hz, 9.47 Hz, and 29.97 Hz) are coherent across the CS magnetometer channels. They do not appear in the EX or EY magnetometers. This is consistent with previous observations.
• The 99.999 Hz comb is coherent with almost all the channels we’re tracking in Fscans including CS, EX, and EY magnetometers. It is also coherent with H1:CAL-PCALY_RX_PD_OUT_DQ. We do not understand why this comb appears in a PCAL channel.
• Previous studies led to us tracking H1:ASC-OMC_{A,B}_{PIT,YAW}_OUT_DQ with Fscans. Most of the observed combs are coherent with A_PIT, A_YAW, and B_PIT, but not with B_YAW. The 4.98 Hz comb alone is not seen by any of these four channels. It's not clear what is different about the 4.98 Hz comb, and what is different about the B_YAW channel.

Prior related alogs: 68261, 66925

Attached figures: (1) 200-930 Hz plot demonstrating the range of the 9.47 Hz combs, as well as some of the other noted combs. (2) Zoom on the triple peak of these combs. (3) Low frequency spectrum demonstrating the 4.98 Hz comb.