This morning, as anticipated in the entry 69688, we started with a new HWS-INJ measurement to check the WI CH position after the movements performed yesterday evening using the hot mirror on the WI CO2 bench.

Francesco set the ITF in WI single bounce with PR aligned. 

The HWS-INJ illumination is shown in Fig.1 

07.34 UTC: START HWS ACQUISITION (20260903T0934)

07.38 UTC: WI CH ON (WAVEFRONT 7)

07.48 UTC: WI CH OFF (WAVEFRONT 25)

This measurement confirmed that the CO2 actuators were reasonably well aligned with the RH.

At this point, we went to the Laser Lab with Suzanne and Piernicola to try to improve the centering of the HWS-INJ beam on the WI mirror.

As a first attempt, we performed a pure shift using EIB_HAR_M0 (see Fig. 3). The vertical alignment was easily corrected by a small counterclockwise rotation of the mirror (see Fig. 4).

The horizontal alignment was more challenging. We tried moving the horizontal knob in both directions, but we were not able to obtain the required displacement.

We then tried to recover the alignment using the usual procedure, by superimposing the HWS beam on the green beam. Although we were able to achieve a good overlap, the beam was still clipped on the CCD and no further horizontal adjustment was possible, as the corresponding knob had reached the end of its travel range.

At this point, we rotated the mirror around its axis to move the adjustment away from the end of the travel range. We then realigned the HWS beam with the green beam and also checked the beam reflected back from the WE. The returning beam is shown in Fig. 4.

At this stage, the alignment appeared to be recovered. However, a new HWS acquisition with the WI RH showed that the RH signature was still approximately in the same position as at the beginning (see Fig. 5).

Tomorrow morning we will try to optimize the HWS beam alignment around this position.

To be noted: in order to ease the alignment of the HWS beam on the green, we temporarily removed the automatic check of the presence of the CEB GREEN BEAM in ARM_LOCK automation node (lines commented at #311 and #828). To be reverted once this work will be finished.

14:00 UTC ITF in DOWN state with commissioning group still working in Laser Lab (Corubolo, Melo, Nardecchia, Spinicelli)

20:00 UTC WI RH switched on. Additional control loop on the WI MIR. EIB left on ground, INJ locked.

20:05 UTC INJ Lab air flow set to Portata Ridotta

21:00 UTC ITF left in SINGLE_BOUNCE_WI with commissioning group still working on the lock of the arms.

ITF found in LOCKED_ARMS_IR

At 7:30 UTC  ITF in SINGLE_BOUNCE_WI  with PR aligned.

At around 8:30 UTC the commissioning team went in the Laser Lab; actvity still in progress.

INF

At 12:30 UTC UTA INJ in "Portata Nominale" under request of the commissioning crew.

The /virgoLog disk area was at more than 80% since severals weeks . The investigations made the 2026-08-28 gives the following report 

Filesystem          1K-blocks      Used Available Use% Mounted on
virgodata:/virgoLog 361112576 300837888  41928704  88% /virgoLog

Scan /virgoLog/VirgoOnline directory
191608888       /virgoLog/VirgoOnline
33953916        /virgoLog/VirgoOnline/NNC_NEB
33939604        /virgoLog/VirgoOnline/NNC_CEB_LEV1
21681556        /virgoLog/VirgoOnline/BaDAQ

8734112    /virgoLog/VirgoOnline/FFLMoni55

All the files related to theses 4 servers with a size greater than 1GB were moved from /virgoLog/VirgoOnline to /data/dev/logs/VirgoOnline/ .

The attached  plot shows  the virgoLog rate and usage since the beginning of the year(2026) upto today

ITF found in COMMISSIONING Mode and DOWN State.
All times are UTC.
From the previous shift: TCS activity with INJ HWS is ongoing (Nardecchia, Corubolo), and INJ ventilation set to full speed (Portata Nominale).
13:30 - 14:41 EIB CCD camera removed and HWS installed (Spinicelli, Corubolo, Lagabbe).
14:47 INJ ventilation set back to reduced speed (Portata Ridotta) (operator).
14:58 ITF in SINGLE_BOUNCE_WI (set after LOCKED_ARMS_IR) with PR aligned (operator) and additional loop on the WI MIR switched on (Pinto).
20:46 TCS activity with INJ-HWS ended (Nardecchia, Corubolo, #69688).
IFT left in COMMISSIONING Mode and LOCKED_ARMS_IR State.

This afternoon was devoted to the HWS-INJ activities.

As previously done for HWS-DET, we removed the HWS and installed the CCD camera in its place after grounding the EIB. This activity was performed after the Daily Meeting, between 13:30 and 15:00 UTC.

The HWS-INJ SLED beam was switched on and appeared to be well aligned on the CCD camera. Figure 1 shows the beam on the CCD with the ITF set in WI single bounce, the PR aligned, and the SLED voltage set to 2.3 V. Also the additional loop on MIR has been enganged by Manuel.

To make sure that the observed beam was indeed the HWS beam reflected back from the WI, we switched off the green beam and tilted the WI TM to check that the beam moved accordingly on the CCD camera, which was indeed the case.

After that, the SLED was switched off in order to replace the CCD camera with the HWS.

The HWS illumination is shown in Fig. 2, with the ITF set in WI single bounce, the PR aligned, and the SLED voltage set to 1.4 V.

15:04 UTC: HWS acquisition started

15:12 UTC: WI RH ON (wavefront 5)

The RH signature is visible at the edge of the HWS map (see Fig. 3), suggesting that the SLED beam is not well centered on the WI mirror.

16:54 UTC: WI RH OFF (wavefront 55),and the additional control loop was disengaged.

During the same acquisition, we switched on the WI CH to check its position on the HWS map.

17:50 UTC: WI CH ON (wavefront 80)

The CH-induced OPL corresponds to the blue area shown in Fig. 4.

19:31 UTC: WI CH OFF (wavefront 131)

As the last activity of the day, we performed a rough alignment of the CH with the RH. This will allow us to use the CH as a reference tomorrow, when we move the HWS beam using the steering mirrors on the EIB.

STEP 1: Movement of HM by 3 cm (15000 steps) backward in TX

STEP 2: Movement of HM by 2.1 cm (12000 steps) forward in TY

19:59 UTC: WI CH ON (wavefront 144)

We concluded the activity at 20.46 UTC.
Lorenzo will relock the long arms.
Tomorrow, we will start with another HWS acquisition to check the new CO2 actuator position.

Today, we proceeded with the alignment of the CO₂ actuators with the NI RH, based on the measurements performed yesterday.

At the beginning, we encountered some problems with the picomotor control interface. After discussing the issue with Giulio and Franco, we understood that the problem was related to the incompatibility of the old interface with the new operating systems. To bypass the problem, we used CTRL1 to control the picomotors. However, the picomotors can also be controlled directly from the VPM, which is the solution we will use next time.

The ITF was set in NI SB, with the SR aligned and the B5 drift control disengaged.

8:47 UTC: HWS data acquisition started (20260902T1047)
8:50 UTC: NI CH ON (wavefront 6)
8.54 UTC: NI CH OFF (Wavefront 11)

An example of the measured wavefront is shown in Fig. 2.

STEP 1 – TY adjustment
We moved the CO₂ actuators by 1 cm (5556 steps) backward in TY.
9:04 UTC: NI CH ON (wavefront 28)
9:12 UTC: NI CH OFF (wavefront 45)

STEP 2 – TX adjustment
We moved the CO₂ actuators by 1.4 cm (7906 steps) backward in TX.
10:00 UTC: NI CH ON (wavefront 132)
10:07 UTC: NI CH OFF (wavefront 145)

STEP 3 – TX fine adjustment
We moved the CO₂ actuators by an additional 0.5 cm (2800 steps) backward in TX.
10:43 UTC: NI CH ON (wavefront 211)
10:54 UTC: NI CH OFF (wavefront 229)

STEP 4 – TY fine adjustment
We moved the CO₂ actuators by 0.5 cm (1000 steps) forward in TY to fine-tune the horizontal position, since the two directions are slightly coupled when moving in TX.
11:14 UTC: NI CH ON (wavefront 267)
11:25 UTC: NI CH OFF (wavefront 288)

Through these successive adjustments, we progressively superimposed the CH center on the RH center. Figure 3 shows the RH, together with the CH in its initial and final positions.

The measurements were completed at 11:25 UTC.

The CO₂ actuators are now centered on the NI mirror within approximately 0.5 cm.

After that, we switched off the HWS-DET SLED to proceed with the HWS-INJ activities.

ITF found in LOCKED_ARMS_IR, COMMISSIONING mode

7:00 UTC ITF in SINGLE_BOUNCE_NI with B5 beam drift open and SR ALIGNED after a cross alignment and reaching LOCKED_ARMS_BEAT_DRMI_1F for a few seconds

7:30 UTC CO2 benches check (Corubolo, Nardecchia)

12:00 UTC ITF in LOCKED_ARMS_IR with B5 beam drift open

13:18 UTC NI etalon loop set to 19.57, 20000s ramp (Mantovani, operator)

13:23 UTC INJ lab ventilation set to Portata Nominale (operator)

13:30 UTC EIB camera placement, ITF in DOWN state, ITF_LOCK and INJ_MAIN paused (Gosselin, Lagabbe, Spinicelli)

13:35 UTC TCS Auxiliary Cooling System Chiller Setpoint changed to 17.8 °C (operator)

The VIM page with sideband gains has been reporting surprisingly low sideband gains, with a gain of at most 34 for the 6MHz sideband when the CITF is locked.

Figure 1 looks at the sideband magnitude measured at different times. In blue at the beginning of O4 in May 2024, in green in March 2026 during the squeezing injection work, in red on August 11 after the mirror and CP replacement, and in purple on August 28. 

After the mirror replacement the 6MHz sideband magnitude looks to be ~15% higher than before the replacement. The 56MHz sideband gain has been more varying after the replacement, probably depending on the quality of the SR alignment, and has been at least the same and up to 30% higher than before the replacement.

Figure 2 shows the  6MHz sideband power measured by the B4 phase camera in CITF, and Figure 3 in single bounce. Using the formula from the OptChar paper G_SB = T_PR * T_BS^2 * R_IM * P_B4_CITF / P_B4_SINGLE_BOUNCE, the sideband gain is around 53 for the LSB, and around 51 for the USB. Which is still far away from the value of a perfect interferometer around 75, but better than it used to be. 

Figure 4. Looking at brief locks from Sep 1, the 6MHz sideband gain may be as high as 60.

The simulation of the PR CHROCC imperfection where showing that the maximum theoreticaly possible gain for the 6MHz gain is 68, given the simulated PR CHROCC imperfections VIR-0567C-22.

Romain checked yesterday's data (69675) and pointed out that the B5 drift control was engaged during the measurement. Unfortunately, this makes the measurement unreliable.

Therefore, today we needed to repeat the measurement performed yesterday.

The ITF was prepared for the measurements in the following configuration: NI in single bounce, B5 drift control disengaged, SR aligned, and the additional loop on the NI MIR switched on.

The HWS-DET illumination is shown in Fig. 1, with the SLED voltage set to 1.45 V.

14.13 UTC: HWS ACQUISITION START (20260901T1613)

14.24 UTC: NI RH ON at around 15 W (V=23 V, WAVEFRONT 7)

16.07 UTC: NI RH OFF  (WAVEFRONT 56)

The RH signature shows up clearly in the HWS map (Fig. 2).

Unfortunately, after switching off the RH at around 16:40 UTC, MATLAB crashed and the HWS data acquisition was interrupted.

At this point, we started a new measurement using the same reference wavefronts as in the previous measurement.

16.50 UTC: HWS data acquisition started again (20260901T1850), using the same reference images of the previous data acquisition run

16.57 UTC: NI CH ON at high power (WAVEFRONT 2)

18.01 UTC: NI CH OFF (WAVEFRONT 34)
The CH signature shows up clearly in the HWS map (Fig. 3).
Using both measurements, we identified the maximum and minimum OPL generated by the RH and CH, respectively, and determined the corresponding coordinates, as reported in the table below.

Thus, on the mirror, the displacement between the CH and RH  (or TM) centers is:
ΔX =  (15 ± 4) mm 

ΔY = (17 ± 4) mm 

So, we need to move the CO₂ actuators by approximately 1.7 cm downwards and 1.5 cm leftwards.
In Fig. 3, some control signals recorded during the measurement are shown. We did not notice anything unusual, but it would be useful if the experts could have a look and confirm that everything is fine.

Tomorrow, we will switch the CH on again and align it with the center of the RH.

NB: Manuel disengaged the NI MIR loop, and Fabio relocked the arms.

As mentioned by Romain Gouaty during the daily meeting the SDB1 bench angle has been changing during this measurement, due to the B5 drift control loop which was closed and trying to follow the beam

Figure 1-5 show a few different examples of the B1p and B5 beam shape during the measurement, both of them change shape and size. I expect that this is due to the thermal lens in the NI CP detuning the detection telescope, either by just moving the camera position with regard to the beam waist, and the beam being astigmatic. Or more likely, because the beam stops being collimated at the input of the parabolic telescope, and parabolic telescopes become more abberrated when used for converging or diverging beams.

Especially on figure 5 the beam stops being round. For the B5 beam the cross beam shape is normal, as the B5 pick-off is highly polarized by two mirrors actiing as polarizers before the B5 camera, so most of the beam on the camera is in P-polarization and shows the cross pattern of the injection Faraday depolarization. 

Following a beam which changes shape with the B5 quadrant is not a right choice, and the better solution is to turn of the drift control. Note that today when the drift control was turned off the beam moved by ~20urad, and turning off the floating set points, and adjusting the fixed set points to restore the bench orientation was needed.

To investigate the excess noise in the vertical LVDTs, I performed a brute-force correlation analysis with BruCo, using all ENV and INF channels over the GPS interval identified in #69615.

The results, available at this link, show that the seismometers and accelerometers around the EIB are correlated with the excess noise below 10 Hz. However, these correlations may simply witness the excess motion measured by the LVDTs, rather than provide information about its origin. No other noteworthy correlations were identified.

ITF found in COMMISSIONING Mode and LOCKED_ARMS_IR State.
All times are UTC.

06:00 MAINTENANCE begin.
06:55 - 06:57 DET: OMC 1st, Lock attempt interrupted due to INJ unlock, B1 shutter closed for safety (operator, see attachment #1).
07:04 - 07:09 DET: OMC 2nd Lock attempt interrupted due to OMC temperture jump (operator, see attachment #1).
07:12 - 07:16 DET: OMC 3nd Lock attempt interrupted due to OMC temperture jump (operator, see attachment #1). OMC Lock skipped for the moment, experts informed.
07:27 - 07:48 DET: OMC Scan (operator, see attachment #2).
07:48 - 07:55 DET: OMC B1/B1_PD3 demodulation phase adjusted, OMC Lock performed, B1_PD3 photodiode offset adjusted (Gouaty, #69677). 
08:16 - 08:26 TCS: Thermal Camera Reference (operator).
08:45 - 08:56 TCS: Power Checks (operator).
10:00 MAINTENANCE Ended.
13:52 TCS: CO2 Bench Checks with HWS begin (Nardecchia, Corubolo).

ITF left in COMMISSIONING Mode, SINGLE_BOUNCE_NI State, SDB1_LC B5 drift control disabled and SR aligned.

Sub-system reports:
DET
SDB1_Quadrants offsets kept to the SINGLE_BOUNCE_NI ones to allow TCS work with DET HWS.

TCS
CO2 Power Checks at the pickoff (TCS__CO2_POWER_CH_PICKOFF):

Figure 1. The adjustment today has essentially reversed the adjustment I had done on Sunday evening. When the interferometer was DOWN for a few hours on Sunday afternoon the offset has increased over a few hours. Once I did the offset adjustment, and relocked the arm the offset has decayed back on a time scale of 12 hours. Which made reversing the Sunday adjustment necessary. 

Figure 2. The offset on B1 PD3 is closly following the temperature changes on the bench, which is what one could expect. And the adjustment on Sunday happened to be at the peak of the temperature excursion following the issues with SDB2 on Sunday afternoon. https://logbook.virgo-gw.eu/virgo/?r=69669

This morning, the OMC was not locking due to a mistuning of the OMC error signal demodulation phase, which was found to be wrong by ~90 deg.

The demodulation phase of B1_PD3 was adjusted to 3.4 rad (previous value was 1.85 rad). After reloading the external configuration at 07h45m54 utc, the OMC was able to lock on the TEM00 at first attempt.

Assuming that the demodulation phase for the B1_PD2 photodiode would be affected in the same way, we also adjusted the B1 demodulation phase from -0.6 rad to 0.97 rad. The new demodulation phases have been recorded in the main configuration file of process SDB1_OMC.

We also noticed that the offset of the B1_PD3 photodiode was quite large. The offset was retuned and we reloaded the configuration of SDB2_dbox_bench at 08h05m03-UTC (see attached figure).

This afternoon, we performed several checks before starting the HWS-DET acquisition with the NI RH ON.

As a first step, we checked the HWS-DET acquisition and encountered an issue with the MATLAB version called by the Python code of the acquisition software. Giulio solved the problem by updating the acquisition code to make it compatible with the  MATLAB version 2023.

Now the command to launch the acquisition is:  

./hwsAna2022_R2023a.py -d/r/l DET 

In parallel, Fabio went to the Central Building to switch on the power supply of the NI and PR RHs.

At this point, we prepared the ITF for the measurement. After being locked in CITF with the additional loop on the NI MIR engaged by Paolo, the ITF was set in NI single bounce.

The HWS-DET illumination is shown in fig. 1. The voltage of the SLED has been settled to 1.45 V.

14.41 UTC: HWS ACQUISITION START (20260831T1641)

14.58 UTC: NI RH ON at around 10 W (V=19 V)

16.49 UTC: NI RH OFF  (WAVEFRONT #42)

The RH signal was clearly visible in the HWS map (see Fig. 2).

The HWS beam appears to be displaced with respect to the center of the mirror by approximately 1 cm and 2 cm along the two directions..

To verify the alignment of the NI CO₂ actuators, I switched on the NI CH at 17.12 UTC.

An example of the wavefront map with CH ON is shown in fig. 3. The CO₂ actuators and the RH appear to be well aligned in the horizontal direction, while the CH appears to be slightly lower than the center of the mirror in the vertical direction. However, I would like to repeat the measurement with the CH, since this measurement was performed after several hours in SB.

At the end of the measurement, I closed the NI CH flip mirror (19.38 UTC).

Paolo will disengage the additional loop later this evening.

The North arm will most likely need some time before it can be relocked.
 

Below the list of the activities communicated in control room:

TCS: det hartman sensor re-installation (#69673);
TCS: NI alignment check with hartman det sensor, in progress... 

Air Conditioning
from 9:50UTC to 10:20UTC I set the detection area air conditioning system in "Portata Nominale" to allow the work on det hartman sensonr;

In order to start the check the NI HWS alignment with the NI RH of this afternoon,  we put back the HWS-DET camera in place of the CCD.  

The same plot related to 2 events that occurred on 2026-08-20-04h58m40-UTC and on  2026-08-20-08h51m30-UTC :

• For each of these events, the timing_error signal of the RightUp and RightDown DBoxes were still correctly collected 

As already experimented  2 times during the week from 17-22 August, the  SDB2_DBOX_LeftUp DBox was found unreachable in the Tolm network since 2026-08-30-14h22m05

 Its have been recovered by performing 

• an OFF/ON using  the  SDB2_POWERSUPPLY  server 
• and a full reconfiguration of  the SDB2 bench DBoxes 
• Operations performed betxeeen 2026-08-30-18h32m45-UTC and  2026-08-30-18h57m14-UTC

The problem is not understood. For the time being

• all the SDB2 suspension controls have been left open
• the ITF_LOCK Metatron node put in DOWN

The attached plot shows  the trend of the DBOXes' timing error channels and their  12V power supply channels before the event, during the event, and after the DBoxes reconfiguration

DET_MAIN was stuck in UNKNOWN state because of a large offset on B1 PD3. After adjusting the offset around 19:45 UTC, I could put back DET_MAIN into the SHUTTER_CLOSED state. And then lock the arms using ITF_LOCK. SDB2 is not used for locked arms, so it should be ok to keep the arms locked even if SDB2 is not controlled.

ITF found in DOWN State and COMMISSIONING Mode.
All times are UTC.
05:12 - 09:00 DAQ: EPRB, SIB2, ALS DAC firmware update (Masserot, #69668).
09:26 - 10:38 PSTAB 50Hz harmanics feed-forward preparation, turned on at 10:18, and it will be turned of at the end of the day (Was, #69666).
10:37 CITF relocked only at 1F stage, the handoff to LOCKED_ARMS_BEAT_DRMI_3F caused several unlocks.
ITF left in COMMISSIONING Mode and LOCKED_ARMS_IR State.