This morning LVDT modulation frequency of the horizontal accelerometers has been changed (from 49.5 to 48.3 kHz). The demodulation phases has been adapted, the sensing elements have been re-centered, the TFs re-measured and the controllers re-estimated. Horizontal inertial damping gains has been re-measured as well and changed accordingly.

We investigated the issues concerning DET_MAIN, which were reported in : https://logbook.virgo-gw.eu/virgo/?r=63964

During the night from April 14 to 15, DET_MAIN went to the UNKNOWN state after an ITF unlock. This happened two times, but the two events were actually uncorrelated.

The first time, at 22h57 utc, DET_MAIN went to the UNKNOWN state because of a failure of the injection system. As shown on Fig.1, the injected power (INJ_IMC_TRA_DC) falls to 0, while DET_MAIN was in the state SHUTTER_CHECK_OPEN checking for the shutter to be opened. Since there is no power due to the failure of the injection system, DET_MAIN is not able to recognize that the shutter is open and therefore goes to the UNKNOWN state. In this situation, putting the ITF in NI single bounce, and then requesting the DET_MAIN state "FORCE_CHECK_OPEN" would normally allow to unblock DET_MAIN (then the standard state SHUTTER CLOSED can be retored).

The second time, at 00h14 utc, the shutter has been closed, but the check that the shutter is actually closed (in the state SHUTTER_CHECK_CLOSED) fails (Fig.2 and Fig.3). This is almost certainly due to the fact that around 00h14m17 the power on B1p_PD2_DC is close to zero due to interference fringes. Therefore, as there is not enough power on the dark fringe beam, DET_MAIN is not enabled to confirm that the OMC shutter is open. In this situation, requesting with DET_MAIN the state "FORCE_CHECK_CLOSED" would probably allow to recover the standard state "SHUTTER CLOSED".

Some plots showing the efficiency of the DARM_FREQ clipping in the case of  burst of glitches:

• events of the 2024-04-08 around 17h32m-UTC trend : burst of glitches on NARM and WARN
  • raw at 2024-04-08-17h32m20-UTC  and the zoom where the period with the clipping enabled is highlighted (red rectangle)
  • raw at 2024-04-09-17h37m-UTC
• events of the 2024-04-09 around 14h45-UTC trend:  burst of gliches on WARM only
  • raw  at 2024-04-09-15h48-UTC
• events of the  2024-04-14-23h20m-UTC trend: burst of glitches on NARM and WARM
  • raw at 2024-04-14-23h20-UTC

There is  several single glitches mainly of WARM like the following ones

• 2024-04-15-02h16m22-UTC : trend, raw
• 2024-04-14-22h25m19-UTC: trend, raw
• 2024-04-12-01h55m-UTC: trend, raw_01h57m14-UTC. raw_02h01m23_1s-UTC, raw_02h05m_80s-UTC

This morning, we updated the conditions on the DMS flags for the QPD_B1p/B2/B5/B4 in the configuration file of the DetMoni process.

Main novelties are:

• we are now always checking the level of corrections applied to the galvos. If the corrections exceed 9V in absolute value this will trigger a red flag, if they exceed 5V this will trigger a yellow flag.
• Most of checks on the QPD signals were performed after CARM NULL 1F. We updated the logic to start performing all the checks from LOCKING_ARMS_BEAT_DRMI_1F (when the galvo loops are actually engaged).

Activity concluded at 8h43 utc.

This morning I updated the values of the SNEB_LC angular setpoints (TX,TY) in the SNEB_LC configuration file. The motivation was to reduce the offsets needed for the drift control and restore a green flag on the DMS for SNEB_LC.

The angular setpoints were changed as described below:

SNEB_LC_TX_set: from -656 to -633

SNEB_LC_TY_set: from -254 to -258

External configuration file reloaded at 07h13m18-UTC.

ITF found in Science mode; it unlocked at 23:28 UTC because of the following earthquake: M 5.9 - 143 km SE of Koshima, Japan.

The ITF was relocked at the second attempt; Science mode at 00:39 UTC.

At around 3:00 UTC the DMS started to report a red blinking flag for Sc_WE_MIR_COIL_FLAG (plot2).

At 4:16 UTC the ITF unlocked; the unlock seems correlated to Sc_WE_MIR_COIL_FLAG (plot3); to be checked by experts.

ITF left in relocking; no DMS alerts.

ENV

Sea activity increased during the shift (plot4).

Guard tours (time in UTC)

From 21:00 to 21:30; from 23:00 to 23:30; from 1:00 to 1:30; from 3:12 to 3:44.

On April 9 we performed a set of short (60s) colored acoustic injections in the CEB. The ITF was locked in LOWNOISE 3 since a few minutes.

The purpose was to tune the level of the injection in such a way to avoid triggering the 92 Hz oscillation of the BS F0 accelerometers (mostly Sa_BS_F0_ACC_H3) which caused unlocks in the past (https://logbook.virgo-gw.eu/virgo/?r=63709). The purpose of the present test was not to understand the nature and physical reason of the oscillation onset, which remains to be understood.

We injected colored noise between 20 and 2000Hz with 3 levels: 0.03 V, 0.04 V and 0.05 V, one 25min glitch occurred right at the beginning of the 0.05 V injection (Figure 1).

The intensity on the acoustic noise produced in the hall, measured in the position of the hall microphone, was of the order of a factor 20 above the quiet condition (Figure 2). The 92 Hz oscillation of  the BS F0 ACC H3 accelerometer onsets already with the 0.03 V but  amplifies x5 and x10 when the injected level increases from 0.03V to 0.04V and from 0.03V to 0.05V, respectively (Figure 3).

Figure 4 shows the impact on hrec. The noise in hrec increased at some structures, mostly known to be associated to SDB1. These excitations are well visible with all injected levels (Figure 5, which also shows the 25min glitch).

It seems to notice also an increase of the 74 Hz line (DARM loop gain) and the 227 Hz line (SSFS loop gain). As well, it seems to notice a small increase of the noise in the bucket. It seems that particularly the injection at 0.05 V, brings the ITF to a different working point where other noises (e.g. frequency noise) are more coupled.

However, spectrograms in Figures 6 and 7 indicate that the amplitude of 74 Hz and 227 Hz lines was not so stable during the injection period (we were at the beginning of a lock) and its correlation with single acoustic injections is not straightforward.

Paolo's suggestion is to better study this behaviour with longer injections.

The ITF kept the lock all the shift, science mode stopped from 15:46UTC to 15:50UTC due to squeezing disengage and from 18:30UTC to 18:40UTC for calibration (hrec check).

- guard tours(UTC):
16:56 --> 17:36
19:01 --> 19:28

Calibration
- 18:30UTC: CALIBRATING_DF_DAILY;

At 7h28 utc, we lowered the OMC locking threshold on SDB1_B1x_DC_DARM_norm_prod from 1600 to 1000 in order to make the OMC lock more robust againts ITF misalignments.

I'm investigating this issue, without much success for the moment. From the point of view of data analysis, they are not a major problem, as long as their duration is short, their number/rate remains low enough, and they are just glitches, not increased baseline noise. I add just a couple of plots to motivate the previous statements.

Figure 1: glitchgram showing the omicron triggers of the last 24 hours. The bottom plot shows their rate, which remains under control and below the 1-per-minute level (the one from O3).

Figure 2: "rectanglegram" showing, in addition to the previous plot, the frequency extent of each glitch.

Figure 3: median normalized spectrogram to show that the noise level has remained on average the same, despite the presence of these new glitches.

Figure 4: spectrogram of one of these glitches. They are quite different from the infamous 25-minute ones, and present a repeated excess energy structure.

I will follow up with some correlation study results (hopefully).

Figure 1. As reported by others at the daily meeting, there are new loud glitches in h(t) since the lock of this morning at ~4 UTC

Figure 2. These glitches are visible in the BNS range as drops that last 1-2 minutes, both in Hrec and Hrec raw (so it is not a noise subtraction filter in Hrec having issues). They don't seem to be due to PR F0 glitches nor to B1 photodiode saturations.

It would be good to know from detchar how much of a problem these glitches are for data analysis. And if any correlation with other sensors can be found.

The issue with the extra spike at the beginning of the colored noise injection was related to time settings in the ACL commands in the ENVnoise process. These modifications were made by Alain (on March 26):

Figure 1 shows the result of the test: blue is with the OLD settings, purple is the with the NEW settings (the same colored noise with amplitude 0.025 V has been injected in both cases). The spike is no longer present.

The same test was done by injecting the colored noise from the ENVnoise and also using the ENV_MAIN node which calls the AcousticInjectionCEB process.

The offset on PR_TX is still there.

It's hard to tell exactly whithout trying, but it still seems that the optimal setpoint falls between 0.004 and 0.006 mA, as it did last Friday

Upon arrival, I found the ITF in the ACQUIRE_LOW_NOISE_3 state. The ITF locked correctly at 5:05 UTC and SCIENCE mode was set.

There was an unlock at 7:25 UTC. During the lock acquisition, at 7:40 UTC, I changed the NI Etalon set point to 20.0 degrees (100 seconds ramp time), as requested By Maddalena Mantovani.

At 8:18 UTC Didier Verkindt restarted the SegOnline process (see #63966).

After a failure during the locking acquisition occurred at 8:00 UTC, the ITF reached the LOW_NOISE_3_SQZ at 8:45 UTC. I set the SCIENCE mode one minute later.

I left the ITF locked and in SCIENCE mode.

Last night, around 21h30 UTC, an earthquake strongly misaligned NE mirror (several mrad) and the PCal beam reflected by NE mirror was not visible anymore by the detection sphere (PCAL_NE_Rx_PD1_DC).
Plot1 shows the NE alignment signals during the earthquake.
Plot2 shows the start of the earthquake perturbation, where can be seen the strong misalignment on NE, the corrupted NE alignment correction signals and the decrease of power seen by PCal NE Rx. We can see also that on WE, the misalignment was much less and the PCal WE was not perturbed.

Today at 8h18 UTC, I have restarted SegOnline process after changing its configuration so that it takes as input channel the adcData V1:DQ_META_NOMINAL_LOCK instead of the serData DQ_META..NOMINAL_LOCK.
To do this, I had to restart also FbmQc (and change its configuration) so that it propagates this new adcData channel down to SegOnline.
So, from 2024-04-15-08:18:00, the DQ flag V1:ITF_NOMINAL_LOCK is properly produced and sent to DQSEGDB.

Concerning the failed OMC lock attempt around 4:00, the issue was due to the fact that the TEM00 power was too small to reach the threshold triggering the OMC lock (see Fig.1). This observation and the fact that the dark fringe was larger than during the previous successful lock (Fig.2) suggests a problem of alignment in the interferometer.

Looking at a longer trend (Fig.3), I noticed that after the earthquake the SR_MAR_TX position is following a trend with a bigger slope. Could this be indicative of an issue ? To be confirmed by ISC experts.

Today, I found ITF in SCIENCE. 21:25 UTC ITF unlocked due to an earthquake (20:56 UTC 6.4 Papua New Guinea), NE and NI suspension opened by the guardian. I had to manually close the suspension and realign the NI and NE mirror to relock. 22:58 UTC Det main got stuck after an unlock 00:08 UTC ITF stuck for 30 minutes in LOCKING_OMC_DARM_B1_PD3, then it unlocked, and DET_main got stuck again. 01:10 UTC ITF back in SCIENCE. 01:59 UTC ITF unlocked again. I got a couple more unlocked during the locking acquisition, and again at 03:40 UTC ITF stuck for 30 minutes in LOCKING_OMC_DARM_B1_PD3. ITF left in LOW_NOISE_3.

No DMS event.

ITF locked for all the shift.

From 18:30 UTC to 18:40 UTC ITF in Calibration mode to perform the daily calibration.

No DMS alerts.

Software

FCEM_MotSwitch reatrted at 17:43 UTC after a crash.

Guard tours (time in UTC)

From 13:00 to 13:30; from 15:00 to 15:30; from 17:40 to 18:10; from 19:40 to 20:10.

This is a summary of the PR trips occurred recently.

SInce the beginning of O4, almost 3 days, we had 15 trips. At least ten of them would have unlocked, but the feed-forward prevented it. Only one unlocked the ITF: it was the smallest one, almost invisible in PR_F0_TY, but anticipated by the usual fast glitch on the accelerometers as all the others. Its impact would have been null, but the anti-trip applied by feed-forward produced 6 V of locking correction, enough to unlock.

Considering that the correction resulting from the largest trip was 5 V, it has been decided to reduce e little bit the amplitude of the back action. After this modification, the largest trip arrived at 5.5 V of correction and the ITF survived.

It is clear that we are at the limit and there is the possibility of an unlock both with the large and the small trips. So far we have been lucky and we can hope that things will continue like that, but it would be better to have something a bit more robust. The variable back action, based on a measurement of the foreseen amplitude of the trip, seem a feasible strategy, but needs to be validated on the machine.

As reporter by Francesco, Sa_MC_F0_COIL_H1 was going towards the saturation. The reduction of the correction by the motors has been done this morning, putting in Adjustment for a few minutes.

Today, I found ITF in SCIENCE. 03:12 UTC ITF unlocked, I performed a CITF alignement and relocked the ITF. 06:20 UTC ITF back in SCIENCE.

No DMS event.

ITF found in Science mode.

From 18:30 UTC to 18:40 UTC ITF in Calibration to perform the planned DAILY_CALIBRATION.

At 19:35 UTC the ITF unlocked;  in the attached plot you can see a spike in the Sc_PR signals. At the same time the process ISC_Fb reported the following message:

2024-04-13-19h35m31-UTC>ERROR..-[TfbSource::StoreData] producer Sc_PR: overflow at GPS 1397072149.999912000 (received 2230 / expected 2000) (14490 times)

The ITF relocked at the first attempt; Science mode 20:27 UTC.

SBE

With the ITF unlocked I recovered the SPRB vertical position with step motors.

SUSP 

At the beginning of the shift, I contacted Paolo and Valerio regarding the issue with Sa_MC_F0_COIL_H1; to recover the correction, it would have been necessary to exit Science mode and perhaps unlock the ITF. We decided to continue monitoring the signal; around 16:00 UTC, the correction peaked and reversed the trend, so it was decided to postpone the intervention until tomorrow.

Guard tours (time in UTC)

13:00 - 13:30

17:00 - 17:30

20:00 - 20:30

21:40 - 22:10