As part of the today's commissioning work on the MIR/MAR reallocation between IMs and EMs, the logic of the two LowNoise configurations has been changed: a new parameter, bypass_ln1, is defined as boolean in the [ITF_LOCK] section of the ITF_LOCK.ini file.

When this parameter is set to True, during the LOW_NOISE_1 transition we will keep using the Input Mirrors to actuate. And obviously nothing will be done on the relays. Also, we will prepare the End Mirrors to use directly their LowNoise configuration, i.e. LowNoise2.

During the LOW_NOISE_2 transition, we will jump directly from HighPower to LowNoise2. The only caveat here is whether we can survive acting on the IM relays when already in LOW_NOISE_2 (we usually do that in LOW_NOISE_1). The other caveat is that with the very high useism we have now, the standard lock acquisition would probably not work anyway given our current problems.

More information on the changes at the level of the actuators are reported in the aforementioned entry.

At the time of writing a final configuration has been not selected yet, as issues in the lock acquisition showed up at earlier steps with respect to the LowNoise stages, and we are currently troubleshooting the transition to DC readout.

This afternoon shift was dedicated to commissioning: MIR/MAR reallocation, the work was carried out by Diego, Manuel and Paolo; during the afternoon we collected several fails in LOCKING_DC_READOUT state while opening the B1 PD1 and PD2 photodiode shutters, we succeeded to pass this state only two times, in the evening we called Victor (DET on-call) to investigate this issue, investigation on locking troubles in progress...

SBE
at 17:49UTC the SNEB position loop was opened by the guardian, controls properly closed.

DET
(16-04-2024 19:30 - ) From remote
Status: On-going
Description: unlock at DC_READOUT step

Last night a big worsening of the weather condition  arrived (fig 1) and produced the feared increase of correction on NE / WE mirrors, touching some time 10 V (fig 2). There was no need to wait for the strong wind of today, because the microseismic region, between 0.5 and 1 Hz, was enough to create problems (fig. 3).

Today we had in mind to test a filter for the windy condition, so we proceeded like that. In fig 4 we see that a result was achieved for the low frequency (200 mHz and < 100 mHz): a worsening of the sismic signal (first plot) did not produce an equivalent worsening of the correction. Unfortunately, we were again close to the instability at 1.8 Hz.

The next planned test was to move the marionette correction from ITMs to ETMs and see the effect on the 1,8 Hz instability. We started moving the north arm and the 1.8 Hz became quickly unstable, unlocking the ITF (fig 5, fig 6). Probably the right way to do the test would have been to move both the arms at the same time, but we had no opportunity to try.

We developed a new filter, which is supposed to gain less at low frequency, improve a bit between 0.5 and 1 Hz, and behave at 1.8 Hz about like the one which worked well the past days. We are waiting for a successful lock to know if it works.

In order to achieve LN2 in the current weather condition, a change of transition strategy was required, because normally we need to pass through a locking done by only a pair of mirror coils instead of all the four. If the mirror correction often exceeds 5 V like now, very likely it will saturate when 2 coils are used with the double gain. It happened like that the time we tried the normal transition. The new strategy consists in skipping the transition to LN1: setting directly the LN2 state for ETMs actuation and moving form ITMs to ETMs in this condition, we can continue using the four coils. The strategy worked, but it was not totally tested: the final step of disabling the ITMs high power state through the relays was not tested yet. The usual glitch caused by this action could be too large for LN2. The glitch could be eventually reduced because it is due to a DC value present on the high power actuation, which can be better subtracted digitally.

So far we had just one fast gitch on the three PR ACC, not too different from the usual ones, but it was not followed by any trip. Let's wait for the next.

This morning we noticed that the WI main CO2 laser continued to be in an unstable state since last night at around 06.30 UTC, so we decided to act on WI CO2 chiller setpoint, changing it from 19.04 °C to 19.02°C (12.37 UTC, Fig. 1) in order to restore the correct power values. Also the BCK chiller set point has been changed at the same setpoint.

After this change, there have been no significant changes in the powers of the actuators, which have remained stable around their nominal values. The situation will continue to be monitored to determine whether further intervention will be necessary.

Upon reaching the site, I found the ITF relocking, but it kept unlocking during various steps of the locking acqusitition.

At 6:07 UTC I set the ITF in Maintenance Mode, here the list of the activities communicated to the Control Room:

• Cleaning of Central Building, Laser Lab (external firm managed by Gargiulo);
• VAC Refill (Vacuum Team);
• Crane inspections (external firm managed by Bazzi, the approximated timetable is NE: 6:30 UTC, WE: 7:00 UTC, CB: 8:10 UTC, MC: 8:30 UTC);
• SNEB angular setpoints updated (see report #63979);
• At 8:00 UTC, Restart of ASC_pre (Casanueva);
• From 8:30 UTC from 11:10 UTC, PR F0 accelerometer change modulation frequency (see report #63984);
• Operator Periodic Tasks (see section below);

Periodic Tasks carried out by the Operator:

• From 5:57 UTC to 6:10 UTC, Check of IMC Working Point and Position;
• At 6:29 UTC - 5 minutes of OMC Lock in Single Bounce configuration;
• From 6:37 UTC to 6:58 UTC - OMC Scan in Single Bounce configuration;
• At 7:30 UTC - TCS Chiller Refill;
• At 8:00 UTC - TCS Thermal Camera Reference;
• At around 8:30 UTC - TCS Power Checks (see table below for resuts):

To allow the external firm to clean around EIB, the bench was blocked by De Rossi from 8:48 UTC to 9:29 UTC. Due to the ongoing activities (missing laser and PR ID loop open) it was not possible to perform the planned ALS Maintenance.
 After the activity on the PR was concluded we started to relock, but the ITF kept unlocking at various steps of the locking acqusition, possibly due to the worsening of the weather.
Relock in progress.

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.