DRAFT  REPORT - shift in progress; the report will be finalized and convalidated at the end of the shift

ITF found in Science mode with Autoscience active.

Upon arrival, I found the ITF locked with Autoscience engaged.

An unlock occurred at 15:31 UTC. The ITF was back in LOW_NOISE_3 at 16:28 UTC.

As planned, I set the COMMISSIONING mode at 16:30 UTC. The measurement of the electric charge on WE was carried out by Ruggi (see #66317).

The ITF was back in SCIENCE mode with Autoscience engaged at 19:40 UTC.

EGO truck passages around CEB (UTC):

- 14:01 - 14:18

Guard tours (UTC):

- 19:05 - 19:55

- 21:27 - ongoing

A line at 19.9 Hz, amplitude 1V, has been injected on each WE MIR coil in configuration OPEN, which means connected to the electronics only on one side. In this way no current flow is generated by the injection, but only a voltage. During the injection, only one pair of WE coils was used to lock. The one not used for the lock and not used for the injection was totally disconnected, when the line was injected on UR and DL. Going to UL and DR, a large effect on the 50 Hz was induced in DISCONNECTED state, out of the range of the feed forward applied on WI, so the one not used was kept in the standard state (CLOSED in LN2).

The gps of the injections are:

gpsDL=1425315918;
gpsUR=1425316718;
gpsDR=1425318518;
gpsUL=1425319518;
gpsCLean=1425321068;

duration: 300s (even much more, in some cases)

The attached plot shows hrec in one case (the others are similar except for the impact on the 50 Hz). The amplitude of the injection was set in order to have a signal at the double frequency (39.8 Hz). That signal was small, but we decided to stop increasing the line because the effect at 19.9 Hz was already very large.

The same injections have been performed on NI. The amplitude of the line was 0.3 V. The three coils not involved in each injection were in standard state (LN);  the effect on the 50 Hz was large in any case.

The gps are:

NIUL=1425322018;
NIDL=1425322718;
NIUR=1425323818;
NIDR=1425324498;

300s are always available, but sometime the data are spoiled by a glitch, visible as a drop of the range. In order to select the better periods, the state of the injections are visible in the channels Sc_NI_MIR_VOUT_UL etc.
 

Profiting of an unlock, the changes in the DET_MAIN node have been loaded in it at 15:32 UTC, and while in DOWN I requested SHUTTER_OPEN, then SHUTTER_CLOSED again, with no apparent issues during the transitions. The lock acquisition was then restarted.

ITF found relocking. In CARM_NULL_1F and in PREPARE_SCIENCE mode (AUTOSCIENCE_ON). 
SCIENCE mode acheived at 06:29 UTC. It kept the lock for the rest of the shift.

Ego truck passages around CEB (UTC):
08:22 - 08:52
10:37 - 10:49

This comment from a few weeks ago went back into draft, posting it again.

To study couplings at ~100Hz it is better to look at the frequency line at 227.1Hz instead of the 1111Hz line to judge changes in the CMRF. The CMRF is frequency dependent, so the line at 227.1Hz line will be more representative of the coupling around 100Hz.

I have looked at why DET_MAIN arrived in the UNKNOWN state this morning

Figure 1 shows the transition from SHUTTER_CHECK_CLOSED to SHUTTER_CHECK_OPEN. This transition should have not happened because the slow shutter was closed properly. But it did happen because in the two seconds before the transition the power on B1p PD2 was very low, it was below the 0.002mW threshold, the Michelson fringes bring it up much above this threshold up to 0.02mW in the few seconds before and after, but during the time when the automation did the check the power is low. So DET_MAIN assumes it cannot check if the slow shutter is closed or not, because there is no laser power reaching SDB1.

There is a solution to mitigate this problem, when the power is low on B1p PD2, we can ask the automation to do the check of power several times before giving up and starting to check if the shutter is open. Currenly the automation tries once and then gives up.

I have checked the unlock and it seems to me that it was the IMC to unlock first.

I have compared the measurement in LN3 during the shift (with the DAS step) and the one performed in LN3 on saturday, with the usual calibration. UNdortunately the measurement between 300Hz and 1kHz of saturday doesn't seem to have very good coherence and there is a clearly visible step, so I wouldn't trust it too much. ANd there were no injections performed on Monday,

I think it is already interesting since it shows that the coupling at high frequency hasn't changed at all and that at low frequencies it has slightly increased with the DAS step.

ITF found in Science mode with Autoscience active.

The ITF unlocked at 4:18 UTC; at the next relock I had to stop the Autoscience because the DET_MAIN state went in "UNKNOWN" state after the unlock.

At around 4:50 UTC , during a lock acquisition, SDB2 vertical position was opened by the guardian; it was not possibile to recover the vertical position with the stepper motors because the suspension did not move in the right direction.

For this reason at 5:00 UTC I contacted the SBE on-call and I set Troubleshooting mode; the SBE on-call was able in some way to close the loop but the problem requires a deeper investigation. Dedicated entry will follow.

Relock in progress.

Guard tours (time in UTC)

23:25-0:00; 2:10-3:00; 3:53-4:30

Upon arrival, I found the ITF in CARM_NULL_1F with Autoscience engaged. Without any manual intervention, it reached the SCIENCE mode at 14:30 UTC.

Guard tours (UTC):

- 18:44 - 19:30

- 21:18 - 21:55

Figure 1 . Looking at the offset during the relock today the offset is well adjust with the power at zero when there is no power on the B1 PD3.

At the beginning of the shift I found ITF locked in LOW_NOISE_3 and in SCIENCE mode (AUTOSCIENCE_ON). 
At 13:40 UTC ITF unlocked (TBC). Autorelocking in progress. Now CARM_NULL_1F.

Ego truck passages around CEB (UTC):
08:46 - 09:43

yesterday we increased the LF gain only of about a factor 1.3, which allowed to damp a bit the 1.2 Hz  interaction with PR.

from recent lines injections on PR and BS driving we noticed that the optimal ratio between the calibration weigths of the two BS branches (B1p and B4) might be wrong of a factor 3.

we could try to increase up to this value the gain of the LF branch to see if we can improve better the fbw response of the loop and reduce further the interaction.

It is also true that yesterday we were in the middle of a thermal transient, and this could have impacted a lot the optical gain of the 50 MHz signal (which depends on both the 6 and 56MHz optical gains), but anyhow this gain change is worth to be tried.

I found ITF in COMMISSIONING. At 22:22, ITF was in SCIENCE mode and remained in Science mode for the entire shift.

Guard Tours (UTC):

• 21:30-22:09
• 23:31-00:09
• 02:11-02:51
• 03:40-04:20

The reason of this shift is reported in #66243. The procedure followed during the shift is reported in this git issue. 

At the beginning of the shift, after the unlock, Diego called Michal and Romain beacuse DET_MAIN node got stalled  (66300).

At 16.05 UTC, the interferometer locked at LN2. At 17.35 UTC, the standard SSFS noise injection was performed.

After that, at 18.12 UTC, the DAS outer ring powers were adjusted differentially. In particular, the WI outer ring power was increased by 5%, while the NI outer ring power was decreased by 5%.

After one hour we started to see a growing oscillation at low frequency, in particular we checked that it was the usual interaction between PR and BS TX. SO we tried to move the crossing point of the two error signals. WE changed the weight from 0.67 to 0.82 and the oscillation got damped. After 2 hours we repeated the SSFS noise injections and Figure 1 shows the change on the coupling of the SSFS to DARM between before and after the DAS step.

Then we went to LN3 and we stayed there for 1 hour, and repeated the SSFS noise injection. After this injection Ilaria put back the initial DAS values (22.15 - 22.18 UTC).

ITF found in Science mode, Autoscience active.

At 15:02 UTC ITF in Commissioning mode for the planned activity of test of differential DAS step; activity still in progress at the end of the shift.

Software

BacNet server restarted at 16:27 UTC because it was providing flat data.

Guard tours (time in UTC)

19:00-19:45; 21:30-

I have analyzed the data of the noise injections of Saturday. I attach the couplings of the SSFS to DARM and Hrec in FIgures 1 and 2, and the projections to Hrec and DARM on FIgures 3 and 4. Last noise injection can be found in entry 66199, the coupling level at 100Hz is comparable. but the coherence of some of the injections in the middle range is low.

Is there a filtering done on the figures to include only science time, and exclude the last few seconds of each segment where saturation may occur due to an unlock?

Yes. Glitch triggers are all in science mode segments to avoid the rate analysis getting biased by artificial noise injections. However, I didn't cut on the saturation channel. Looking at its rate, often above 0.1/min, it seems unlikely that these are mostly preceding an unlock. See also this figure from entry #66013. However, I can repeat the rate calculation cutting also on this channel and removing a few tens of seconds before exiting Science mode.

This afternoon the DET_MAIN node got stalled in SHUTTER_CHECK_CLOSED.

We suspect that the cause of the problem was a change in the electronic offset on the B1_PD3 photodiode (correlated with the detectiion lab humidity control test performed during the maintenance).

We adjusted the B1_PD3 offset by +0.0002 mW at 15h22 utc. Then after, performing a successful SHUTTER_CHECK_OPEN (since the shutter was actually opened), we performed a SHUTTER_CHECK_CLOSED to restore the standard conditions of DET_MAIN.

The shift was dedicated to maintenance started at 6:00UTC, here a list of the activity reported to the control room:

- standard vacuum refill from 7:00UTC to 11:00UTC (VAC Team);
- cleaning of central building (Ciardelli with external firm: from 7:00UTC to 10:45UTC);
- ACS: detectiion lab humidity control test (Soldani from 8:150UTC to 11:00UTC);
- DAQ: 1&2MHz demodulations for B2_PD2 (Masserot from 8:20UTC to 9:30UTC #66291);
- INJ: check of IMC working point and position from 8:05UTC to 8:15UTC;
- DET: OMC Lock in single bounce configuration from 7:28UTC to 7:35UTC;
          OMC scan in single bounce configuration from 7:37UTC to 7:59UTC;
- TCS: chiller check and refill (Ciardelli,Zaza 7:30UTC);
          thermal camera reference 8:10UTC;
          CO2 power check (Lumaca 9:55UTC);

maintenance activity completed at around 11:15UTC, ITF relocked at the first attempt and science mode started at 11:56UTC.

Since the start of O4b, every month a chunk of AR frames is produced in /data/prod/hrec/O4/HoftAR1 that contain final h(t) and an updated state vector and updated residual bias and uncertainties on h(t) modulus and phase. Those residual bias and uncertainties, computed every month by Cervane Grimaud, are quite the same from one month to an other. This good stability is illustrated by the attached plot where are shown, for each month of 2024, the residual bias on the modulus and phase of h(t) (<0.5% and <10 mrad at 100 Hz) and the uncertainties on the modulus and phase of h(t) (about 2% and 30 mrad at 100 Hz).

Today there is none phase noise mitigation engaged for the B2_QD{1,2} quadrant signals with the ITF at LN3.

The attached plots compares the coherency with B2_PD2_112MHz_phi or B2_PD2_50MHz_phi

• with the B2_QD{1,2}_6MHz_{H,V}_I , noted that  B2_QD2_6MHz signals are used as error signal for the  PR_T{X,Y}  loops
  • there is a small coherency only for B2_QD1_6MHz_V_I
• with the B2_QD{1,2}_8MHz_{H,V}_I, noted that  B2_QD2_8MHz signals are used as error signal for the  Injection Alignment  loops
  • there is none coherency