To investigate the hypothesis that the structure in the upper part of the HWS map is caused by the green beam, Diego modified the automation configuration to keep it OFF after the unlock. We then performed a new measurement with HWS-DET. For this purpose, I switched OFF the HWS-INJ SLED and switched ON the HWS-DET SLED.

The ITF was locked at CARM NULL 1F at 11:04 UTC. Acquisition started at 14:28 UTC (folder 20251029T1528), and the ITF gently unlocked at 14:36 UTC (WF14).

The structure was also present in the maps (see figure).
The measurement was interrupted, and the lock acquisition was restarted.

ITF found at CARM_NULL_1F in TROUBLESHOOTING mode.
At 09:20 UTC, under request of I. Nardecchia, I unlocked ITF in order to allow the planned activity on WI absorption measurement.
Activity in progress...

This morning we proceeded with the HWS-INJ measurement to assess the absorption of the WI.
The ITF was locked at CARM NULL 1f at 07:41 UTC.
The HWS-DET SLED was switched OFF, and the HWS-INJ SLED was switched ON and set to 1.6 V.
The acquisition started at 09.09 UTC [20251029T1009]. The HWS illumination pattern is shown in figure 1. 
We unlocked the ITF in a gentle way at 09.21 UTC (WF 22).
The YAG effect is visible in the maps (see for example WF 56 in Fig. 2.
We also extracted the curvature from the maps and compared it with the last measurement performed last year [20240801T1703 -  64836]

The measured curvature is consistent with the previous measurements (see the third figure).
The measurement was interrupted at 10:46 UTC (WF 180).

With the purpose to shed some more light on the HWS measurement, we have analyzed the raw images before and after the appearance of the feature in the upper part of the wavefront.

Figure 1 shows the difference between the two raw images. As it can be seen, there is a significant modification of the illumination pattern on the HWS as soon as the ITF has unlocked. The change in the illumination pattern is responsible for the appearance of the feature.

This change in the illumination pattern can be explained with a displacement of the HWS probe beam (due to a misalignment of one of the optics or benches along the path) or with some spurious other beam (1064 nm or 532 nm) reaching the HWS plate. With the available data, it is not possible to discriminate between the two effects, even if a check of the LC signals (figure 2) seems to exclude the displacement of the probe beam.

22:00 UTC ITF found in TROUBLESHOOTING just unlocked from CARM_NULL_1F. I tried to lock with SR ty+2 misalignment but B1p was unstable/too high and ITF unlocked twice.
I left the ITF in CARM_NULL_1F: pic1 shows the drifts in B1p_DC and in the balance of the sidebands during the shift

Guard Tours (UTC)
22:30 - 23:20
00:26 - 01:02
02:31 - 03:07
04:16 - 4:55

Due to the instability of the ITF of the last period, we started a global check of the status of any part of the INJ subsystem that could be related to that problem.

We measured the modulation index of the 6MHz and 56MHz by scanning the RFC with the INJ in standalone. The scan, back and forth, of a duration of 500µs for 500µm of displacement, started at  ~13.31UTC (see fig. 1).

The resulting modulation depth for the 6MHz and 56MHz are, respectively,  ~0.2 and ~0.21 as expected.

As discussed during the daily meeting of Monday, we restored the global thermal settings to the nominal values of last weeks, including the PR Chrocc correction. 

We started setting the nominal DAC voltage  (4.14) on Monday evening (see fig. 1), and waiting the thermalisation, that was expected during the night. However, due to some hysteresis, both heating temperature and circulating current didn't reached the nominal values. In order to restore the correct setpoint, we tuned the DAC voltage (+0.2V then -0.05V) after the maintenance. 

As a result, the sideband slightely increased and the global behavior of the ITF seemed more reliable. Nevertheless, the fringe remains ~50% higher than usual. 

ITF found in CARM_NULL_1F and in Troubleshooting Mode. The shift has been dedicated to the investigation on current instability of the ITF.
From 14:25 UTC to 14:45 UTC with Melo we went in the DET Lab to improve the alignment of the DET Hartmann sensor. Further measurements with the Hartmann sensor indicated a possible issue with the NI Mirror (see report #68051). In agreement with Gouaty, at 19:20 UTC I returned to the DET Lab to place an absorbing glass in front of two SDB2 Viewport in order to investigate a possible issue with scattering light. The glass has been removed at around 21:00 UTC, after a further measurement by the experts.
Relock in progress.

While waiting for the end of the PR CHRoCC transient, we decided to perform the first measurement on the NI. From the HWS-DET map, we noticed a non-uniform illumination pattern on the sensor with the ITF in CARM NULL 1F, so Suzanne and Andrea went to the EDB to adjust the steering mirror in front of the HWS. Figure 1 shows the illumination image before and after their intervention.

1) Acquisition started at 15:12 UTC, with the folder named 20251028T1612.

At 15:17 UTC, the ITF gently unlocked (WF 10). Immediately after the unlock, the NI was accidentally misaligned, but Diego realigned it promptly.

Starting from WF14 (about 2 minutes after the gentle unlock), a previously unseen structure appeared in the wavefront map.

The picture below shows a comparison between the last measurement on the NI (left – 59448) and today’s measurement (right).

The measurement was interrupted at 16:11 UTC (WF 108).

To investigate whether the structure observed in the map could be an artifact, we checked that the SLED of HWS-INJ was OFF and all mirrors, except for the NI, were misaligned. Everything was Okay.

To confirm the results, we decided to repeat the measurement. The ITF was relocked at CARM NULL 1F at 16:27 UTC. 

Before starting the measurement, I slightly increased the voltage applied to the SLED (from 1.05 V to 1.08 V) to raise the counts to approximately 3500 (see the third figure attached).

2) At 17.29 UTC, the HWS-DET acquisition started (20251028T1829). 

Acquisition stopped at 18:25 UTC (WF 103). The structure was still present (see Fig. 4).
At this point, Piernicola suggested that this structure could be due to a spurious beam from the new OMC installed on EDB.
We therefore contacted Romain to ask about the possibility of blocking the YAG beam near the viewports. 
He gave us the green light, and Andrea, with remote support from Piernicola, went to DET to place an absorbing glass in front of the viewports (see Fig. 5).
3) So, after the ITF had been locked at CARM NULL 1F for one hour, we started the third acquisition at 20:04 UTC (20251028T2104).

The structure was still there. The measurement has been interrupted at 20.40 UTC (WF 67). At this point, Andrea returned to DET to remove the absorbing glass in front of the viewport and we restarted the lock acquisition at 21.00 UTC.
In conclusion, a new structure appears in the HWS-DET wavefronts approximately one minute after the gentle unlock. We repeated the measurements three times, and the results were consistent. Initially, we considered the possibility that it was caused by initial misalignment of the NI mirror. For the second measurement, we repeated the procedure, and for the third, we covered the viewports with absorbing glass to investigate whether the structure could be caused by a spurious beam from the new OMC. But even after blocking the viewports, the structure persisted in the maps.

ITF found in CARM_NULL_1F, Troubleshooting mode.

At 7:00 UTC ITF in Maintenance mode, below the list communicated in control room:

• tasks performed by the operator:
  • scan and lock of the OMC in single bounce, see Investigation of failed OMC lock attempt
  • check of TCS images with thermo cameras; the checks of TCS powers have been skipped in agreement with TCS team
  • TCS chiller refill
• civil work around CB;
• cleanning operations in experimental areas;
• suspensions:
  • centering of MC and NE IP;
  • change of demodulation frequency for SIB1 F0 accelerometers;

At around 11:00 UTC all the maintenance activities were concluded; the ITF was relocked in CARM_NULL_1F after a manual prealignment of PR/SR.

At the end of the shift started the planned activity of WI absorption measurement.

In this entry we report the activity performed by the SAT team during the maintenance 

IP centering

We noticed that the correction signal was a bit too high on the horizontal coils acting on the F0 of NE and MC towers. To prevent possible saturations we centered the IP of NE and MC towers through the IP centering tool. Everything went fine during the operation.

Start of operation: 10:45 local time

End of operation: 11:30 local time

SIB accelerometers modulation frequency

Since the intervention described in entry #68006 did not solve the issue of the glitches appearing on Sa_IB accelerometer signals, we changed the modulation frequencies of all three horizontal accelerometers from 50000 Hz to 50123 Hz in order to avoid any possibile external interferences.

Start of operation: 11:00 local time

End of operation: 11:30 local time

This morning, during the usual OMC check in single bounce, the attempt of locking the OMC failed. As shown on Fig.1 the resonance of the TEM00 was crossed around 7h53m55 utc (and the OMC1_PD_DC_check goes to 1 as expected at this time), but the lock was not triggered. This is due to the fact that LSC_ENABLE was equal to 0 at that time. We can see that LSC_ENABLE was set to 1 around 7h44h54 utc but it stayed ON only for half a second. The reason why LSC_ENABLE did not stay to 1 is because the DET_MAIN node was in DOWN at the time the LSC_ENABLE was set to 1.

Next time I recommand the following order in the procedure :

* After setting the NI single bounce mode,  put the metraton note ITF_LOCK in PAUSE

*  From the metratron node DET_MAIN, request the state SHUTTER_OPEN.

* Only after the OMC shutter is open, set the LSC.ENABLE = 1 from the python interface.

14:00 UTC ITF found in LOCKED_ARMS_IR, TROUBLESHOOTING investigation ongoing
19:00 UTC helicopter passage
19:56 UTC unlock - Earthquake in Turkey: as pic 1 shows, while the seismic sensors in CEB, MCB, NEB and WEB clearly mark the time it hits the site and consequently unlocks SBEs (here plotted SPRB), SEISMON flag does not react to the seismon, staying green.
20:35 UTC ITF in CARM_NULL_1F
22:00 UTC ITF left in CARM NULL

Actions performed during the investigation:
TCS: CHROCC standard working point restored - ramp in progress, ITF kept in CARM_NULL_1F
INJ: HWS Reactivation

Could not carry out the planned tasks due to the state of the ITF:
ENV noise injections
calibration with ITF locked
ISC injections (inject_lsc.py)

Guard Tours (UTC)
19:00 - 19:46

Today, in preparation for the absorption measurements, I asked Suzanne to switch on the SLED and HWS of HWS-INJ. The 5 V and 13 V channels powering the SLED and HWS, respectively, were already on, but the SLED voltage was set to zero.

When voltage was applied, the SLED of HWS-INJ did not turn on. As experienced in the past, this SLED sometimes freezes and can be restarted simply by touching it. Suzanne therefore grounded the EIB and touched it, after which the SLED started functioning normally.

Attached are images of HWS-INJ and HWS-DET. In both cases, the beams return correctly on the sensors, and the intensity appears sufficiently uniform to carry out the measurements.

I left the system with the SLED of HWS-DET turned OFF and the SLED of HWS-INJ turned ON at 1.6 V.  

ITF found in CARM_NULL_1F. ITF back in Science Mode from 6:23 UTC.
It unlocked at 7:13 UTC, the rest of the shift has been spent investigating the cause of the general instabilities and issues of the ITF.
At 13:00 UTC, after an unlock possibly caused by a gust of wind or an earthquake that later affected the suspensions (12:38 UTC, M 6.5 - 162 km E of Beauséjour, Guadeloupe), the INJ crew performed a mismatch measurement with the ITF unlocked. Activity concluded at 14:01 UTC, investigation in progress.

We checked the shape of the B2 beam before and after the 20/10 to look for any signs of potential issues on SIB1, both in CITF and in CARM 0. 
We did not spot any big difference in the shape. 
The figures are attached to this entry. 

This night the ITF unlocked at 22:40UTC and it was not possible to relock anymore at LOW_NOISE_3 because of too much power on the dark fringe, even misaligning the SR the ITF sistematically unlocked while setting the DARM offset and starting to lock the OMC; at some point I gave it up and left the ITF locked at CARM_NULL_1F.

ISYS
At around 3:00UTC the EIBAgillisRot server crashed and the actusb1 device become unreachable over the net, I switched off/on the device and restarted the server at 3:27UTC.

14:00 UTC ITF found in SCIENCE
17:13 UTC unlock with seismon and seaActivity flags red (maybe the earthquake in Indonesia). While relocking, to be able to open the shutter, I misaligned SR +2Ty the same way my colleagues did in the past few days, to lower B1p_DC from 0.045 to 0.02 mA.
18:03 UTC ITF in SCIENCE range 47 Mpc -  all IP flags yellow, seismon flag still red
20:16 UTC unlock, DET_MAIN restarted. While relocking this time B1p_DC in CARM_NULL_1F was 0.022 mA so I didn't move the SR, but it spiked to 0.04 mA during the OMC lock causing the ITF to unlock at LOCKING_OMC_DARM_B1_PD3. I restarted DET_MAIN again. PR and SR alignment checked. Sea activity still high, difficulties in achieving LOCKED_ARMS_BEAT. Unlock at LOCKING_CARM_MC_IR. Once in CARM_NULL_1F I misaligned the SR
22:00 UTC ITF left in SCIENCE

Guard Tours (UTC)
14:03 - 14:30
16:53 - 17:25
18:57 - 19:31

ITF found in BAD_WEATHER Mode and DOWN State. Initially, It wasn't possible to relock due to DET_MAIN stuck: the node was unable to check if the shutter was closed, as it reported that there wasn't enough powers on B1p PD2. I've manually checked the various vBias / shutters and previous state of the ITF in DOWN State, but I couldn't identify a clear cause of the issue.
Thanks to the intervetion of Was the problem was identified and solved (a drift in power of B1 PD3) and from 7:04 UTC it was possible to relock. ITF relocked at 8:44 UTC (using the SR Misalignent trick at CARM_NULL_1F) and in Science Mode from 8:49 UTC.
The ITF unlocked at 9:37 UTC, due to the strong wind it was not possible to reach LOW_NOISE_3 until 11:37 UTC.
ITF left locked.

Guard Tour (UTC)
7:35 - 8:02
11:34 - 12:12
13:03 - 

ITF found locked at LN3 in SCIENCE mode.

At 00:58 UTC ITF unlocked due to tha bad weather conditions. High wind activity. BAD_WEATHER mode set.
ITF unlocked twice at LOCKING_CARM_MC_IR. Relocked at 03:45 UTC after the usual cross-alignment in ACQUIRE_DRMI and SR misalignment trick at CARM_NULL_1F.
SCIENCE mode set.

ITF very unstable. It unlocked several times. I waited for a while in CARM_NULL_1F.  Attempting LN3.

Today, we investigated the present ITF working point with the idea to perform some DAS tuning to decrease the power on the dark fringe. 
At 10:43 UTC, we increased the NI inner ring as in the past days, from 0.58 → 0.62, but the effect was negative and we then experienced multiple unlocks. Therefore, I completely reversed the step at 12:21 UTC.
After waiting for some thermal transients, the ITF locked again in CARM NULL 1F at 13:33 UTC.

After about half an hour, Fabio misaligned the SR by 2 μrad in positive TY in order to reduce the dark fringe, which was initially at 0.034 mW.
Once finished, we stopped the lock acquisition in LN2 to  see the position of the order 2 mode on B1 following Michal’s indications. Once in LN2, we waited for the SR alignment (around 14:48 UTC). However, the ITF unlocked shortly after at 14:51 UTC. Using the last ~3 minutes of data with SR aligned we checked that the 02 mode was still around 10.6 kHz (see the first figure attached).
Then, it relocked at CARM NULL 1f  at 15.11 UTC and, again by misaligning the SR by 2 urad, we were able to reach LN3 (at 15.49 UTC).
At this point, we decided to leave the ITF in this configuration without changing anything. 
Fabio settled Science at 18.16 UTC. 
Some trends of the main ITF signals recorded during the day are shown in Fig. 2.
In conclusion, no DAS changes have been applied since last evening. 

ITF found in Troubleshooting Mode and CARM_NULL_1F State.
All times are UTC.
As instructed by the experts the ITF Lock Request will remain CARM_NULL_1F.
06:20:20 ITF Unlocked from CARM_NULL_1F due to strong wind. 
08:00:19 ITF Unlocked from CARM_NULL_1F with unusual increase of power on B7 ~595 mW on SNEB_B7_DC (See Figure 1, Unlock_251025_08-00-19__B7_Increase.png);
09:54:15 ITF Unlocked from CARM_NULL_1F with a similar behaviour, power on B7 ~613 mW SNEB_B7_DC (See Figure 2, Unlock_251025_09-54-15__B7_Increase.png);

From 9:07 to 9:31 test effect of changing MICH offsets on B1p perfomed by Was (#68035).
From 10:40 TCS Tuning operations, experts working on repeted unlocks around CARM_NULL.

Guard tours:
5:30 - 6:10
11:10 - 11:50

The MICH offset can also have an impact on the dark fringe power when the sideband are balanced. 

Figure 1. Shows a test I did this morning between 9:00 UTC and 9:30 UTC, and to my surprise the dark fringe become dark for a MICH offset of 50. The power on B1p decreased by ~20%. I haven't tried to go further than that. The direction that improves the dark fringe is the same as it was on Monday. Duing the MICH offset also the power in the arms was higher by 2%, but the power of the sidebands on B4 decreased.

So it would appear we have an offset in the control of MICH, despite the fact that the sidebands are balanced.