related logbook: https://logbook.virgo-gw.eu/virgo/?r=69040

We measured magnetic field at WT 900m, where less instrumental noise is expected. 
We used a portable setup with Bartington Mag-03 MC100 + Nanometrics Centaur.
These data; time series, ASDs, and spectrogram are plotted here. We can see the 1, 2, 3, ... Hz comb noise stationally. 

(NOTE: Calibration should be confirmed)

The slave laser remained stable over the weekend, so this morning we continued working on the alignment.
We seeded the Neovan with the SL and everything was as we let it on Friday afternoon.

We first attempted to optimize the alignment using the mirror in front of the Neovan while monitoring both the transmitted power and the beam profile on AMP_cam.

Since the improvement remained limited and the AMP NF was still significantly away from what it was before, we decided to realign the SL beam towards the Neovan using LB_M04 (the second mirror after the SL) hoping for both effect on the shift and the tilt of the beam inside the neovan. This proved to be very beneficial for both the output power and the beam profile. We managed to recover 0.38 V on AMP_DC.

We then adjusted the Neovan pumping diodes to investigate whether the situation could be further improved. We decreased the current of all four pumping diodes by 0.1 A and obtained a better output beam shape together with a lower temperature of the Neovan head, while maintaining good output power (Figure 1).
New pumping diode current values: 4.8 A.

Overall, we now measure 0.37 V on AMP_DC, compared to 0.34 V previously, and the low-frequency noise is reduced (Figure 2).

The beam shape also looks improved (Figures 3 before and figure 4 after).

Having recovered both good output power and a good beam shape, we proceeded to work on the PMC alignment.
We realigned it and now measure 0.52 V at the output, compared to 0.49 V previously (Figure 5).

While normalizing PMC_TRA and PMC_REFL with AMP_DC, the throughput initially appeared lower. However, after further inspection, it seems that about 3.7% is still coupled into the TEM01 mode. This should recover once the system is fully thermalized. The mismatch is instead around 1%.

We also computed the throughput using PMC_REFL in the unlocked and locked states. We now estimate throughput losses of 20%, whereas they used to be around 22%.

It should be noted that, since the IMC transmission signal is currently unavailable, we could neither work on the PSTAB nor easily verify the alignment in the AOM. These checks will need to be performed later. However, only minor adjustments were required for the alignment towards the PMC.

We let everything locked for the coming days for thermalization. Fine alignment of the PMC as well as check of the order 1 in the AOM will be done on wednesday. 

YAG beam is blocked into LaserLab, with IMC unlocked and SIB1 valve closed. There is  no main laser beam in the interferometer.

CO2 lasers are switched off as well as the green ones. 

Confirm that there is no laser hazard to enter the NI tower.

fter discussing it with Walid in the morning, we decided to intervene on the SL fiber alignment to see whether we could recover power at the slave output and improve the cavity alignment toward the Neovan.

We started by switching off the SL and taking additional references of the beam going from the ML toward the neovan (in reflection of the SL), since we had previously observed that the Neovan output power was quite good when it was seeded only by the ML.

We then worked on the alignment inside the SL cavity by acting on the vertical and horizontal axes of both fibers, recovering the alignment with the lenses, trying to maximize the output power. We managed to recover about 0.34 V, starting from 0.32 V. We could not go higher and get back to the 0.38V because both axes of the lens on the western side had reached the end of their coarse adjustment range.

From there, having only 10% missing, we started to check the alignment toward the Neovan, and it was better than what we had yesterday. We had to slightly adjust the tilt by acting M0.4 (second mirror at SL output).
We injected the SL into the Neovan and slowly increased its power using the IPC between the two.

We eventually recovered 0.35 V on AMP_DC, which is better than what we had before. From the AMP diagbox QPD signals, the beam appears to be mainly shifted horizontally compared to its previous position (figure). In addition, the temperature of the Neovan head is slightly higher, around 31°C instead of 30°C.

We did not try to realign the PMC for now, but looking at the peaks on PMC_TRA, it appeared to be misaligned, as expected given the signals on the AMP QPD.

For the weekend, we decided to flip the mirror between the SL and the Neovan and reduce the current of the Neovan pumping diodes to avoid the head to overheat. We will monitor the thermal behavior of the SL over the weekend.

The next steps are to reinject again the SL into the Neovan, check whether a slight alignment of the beam inside the Neovan could further increase the output power, and realign the PMC in order to eventually try locking it.

ITF found DOWN in UPGRADING mode.
- Slave laser pumping realignment (Melo, Gosselin)
- NO other activities communicated to the control room.

Some results:

• Figure 1 shows and overview of microphones and accelerometers on the LB and EIB benches during the test period. A significant reduction of vibration noise on the LB occurs in correspondence of the switch off of the NEOVAN head chiller at 13:09. There is also a correspondent reduction of acoustic noise on LB. No effect is seen on the nearby EIB.
• Figure 2 is the same but up to 10kHz, showing that both the NEOVAN chiller and the HVAC also contribute noise up to some kHz. At 14:50 about the Neovan chiller has been turned back on (as confirmed by the INJ team).
• Figure 3 zooms on the region around 50Hz which shows a noise associated to the Neovan electronics chiller (on-off sequence 13:39-13:52)
• Figure 4 zooms on a drifting vibro-acoustic noise line starting at approx  500Hz, which never disappeared during the test. Its frequency drift visually correlates, with some delay, with the temperature inside the Lab and the EIB (Figure 5).
• Figure 6 is the same set of spectrograms in the low frequency (below 5Hz): acoustic spectra are "polluted" by some burst noise which might also be associated to people who was working on the platform at that time (nobody was entering the Lab instead) 
• Follows a set of spectra comparing the noise associated to single devices which were swithed off:
  • HVAC noise - Figure 7 (the off time corrsponds to also the CEB HVAC off): we remind that during this test the Towers HVAC in CEB was on and its noise was sensed inside the laser lab.
  • Neovan head chiller (Termotec) - Figure 8: the noise contribution is evident between 100 Hz and  1kHz. It could be the noise noticed in https://logbook.virgo-gw.eu/virgo/?r=68639.
  • Neovan electronics chiller - Figure 9: it contributes with a line at about 47 Hz (also in Figure 3). This noise is sensed louder by NN geophones on the EEroom floor (look at the red colored spectra which are in units of acceleration - m/s2). 
  • Main chiller (OMI) - Figure 10 - no noise evidence from this chiller.

20/05

Yesterday, while relocking the SL, we noticed that the reflection was quite low: 0.22 V instead of the usual 0.38 V.
When the NeoVan was seeded only by the ML, we obtained higher power than when it was seeded with both the ML and SL.
The SL PUMP DC signals, which monitor the pumping diode power at the output of the fiber in the SL head, were also higher.

This indicates a general misalignment of the SL cavity that needed to be cured. 

Since the temperature of the NeoVan was increasing, we decided to slightly reduce the pumping diode current overnight while keeping the SL running, hoping that thermalization during the night would improve the situation.

21/05

No thermalization effect was observed overnight.

In the morning we held a meeting with Walid and Margherita to analyze the situation. We agreed that the beam of the pumping diodes needed to be realigned inside the crystals. Since the power was already quite high, we were expeting a slight misalignment that could be recovered by ajusting the lenses in front of the cavity (at least as a first try).
We then went to the laser lab in the afternoon to perform the adjustment. By tuning the vertical and horizontal position of the lenses, we managed to recover the reflection signal up to 0.32 V.
We did not fully recover the nominal value, which was quite expected since we only had a limited number of degrees of freedom available compared to the full possible misalignment that may have occurred.

We also measured the slave locking bandwidth (14:51:02) and found 1.15 MHz, significantly lower than the 2.1 MHz measured last time we did it. This further confirms the presence of a misalignment of the cavity. 
Also, visually, we observed that the beam was not propagating correctly through the optics toward the NeoVan, so we decided to flip the mirror located between the SL and the amplifier. 

Peltier situation:

When the safety interlock triggered on 08/05, the PID temperature controllers did not stop sending correction signals. This was verified this morning by manually triggering the safety system.

Our hypothesis is that, during the afternoon of the 08/05, without cooling from the chiller on the hot side and while the system was still attempting to cool the crystal, the Peltier element of Crystal 1 was receiving 2A and experienced an overall temperature increase. This eventually resulted in a general temperature rise of both peltier, both crystals and likely the whole cavity. 

Activities communicated to the control room:

WE vacuum control unit and CEB cryotraps maintenance (Erbanni, Francescon, Macchia, Pasqualetti)
SL electronics checks (De Rossi, Gosselin, Lagabbe, Spinicelli)
Finalization of the changes to the main building's air conditioning system (Infrastructure Group)

 We deployed the DAC1955 v3r3 firmware on the 3 DAC1955 boards used  for the SDB2 bench local controls

• SBE: DAC1955_SN22 located in the DBOX_SN27-slot2 and managed by the SDB_EDB_dbox_rack server 
• LC: 
  • LVDT_in: DAC1955_SN69 located in the DBOX_SN106-slot2 and managed by the SDB2_dbox_bench server
  • LVDT_out:  DAC1955_SN19 located in the DBOX_SN28-slot3 qand managed by the  SDB_EDB_dbox_rack server 
• these DAC1955 boards are now running at 400KHz instead of 100KHz with new facilties for the channel management (see  DaqBox DAC1955 documentation for the details ). The DAC1955 anti-image filter is  a 3rd order with a FCut at 20KHz

The related DBox servers have been updated with the v17r9  the 2026-05-13 and then with v17r10 release the 2026-05-15

These plots show the trend of the relevant signals from the 2026-05-10 to the 2026-05-21 for

•  SBE_SDB2  x,y,z and act1,act2,act3,act4  channels
•  SDB2_LC txyz and txyz_corr channels 

The operations have been done over 1 week, from the 2026-05-12 to the 2026-05-20 

• 2026-05-12-09h57m47-UTC  to 2026-05-12-15h33m36-UTC 

  • DAC1955 v3r3 firmware installation on the related DAC1955 mezzanines
  • Use DBox server  v17r9  release for SDB_EDB_dbox_rack and SDB2_dbox_bench servers
  • the DAC1955 data reception  was set in asynchronous mode and the data policy extension is set to use the zero policy for this version of the DBox server
  • SDB2_SBE and SDB2_LC configuration files update 
    • for SBE and  LC_LVDT_out , the DAC1955 channels are built at 10KHz
    • for the LC_LVDT_in  the DAC1955 channels are built at 50KHz
  • During the operations , we faced with some issues due to the DBOX server compatibility. As consequence all the DBoxes managed by the SDB_EDB_dbox_rack and SDB2_dbox_bench servers were reconfigured.
  • At the end the SDB2_LC loops were successfully closed and the SDB2_SBE ones too with the tracking disabled
• 2026-05-15-04h53m01-UTC to 2026-05-15-05h37m55-UTC
  • Looking at the FFT of LVDT_in and LVDT_out channels; one can see a new line around 36Hz  only on most of the LVDT_out channels  and the presence of the 10KHz line on all the LVDT_out channels
  • This line come from the beating of the FL_H-BR-V line at 9964.3Hz and the 10KHz line due the use of the zero extension policy.
  • Today one way to fix this issue, was to generate the LVDT_out at 50KHz ( LVDTs plots 0Hz-1KHz, 9.6KHz-10KHz ) :
    • SDB2_LC configuration updated to build the LVDT_out DAC channels at 50KHz 
    • LVDT_out DAC1955 reconfiguration to use the new TolmPacket 
  • To avoid the same issue for the SBE DAC channels, they are build at 50KHz too
  • At the end the SDB2_LC loops were successfully closed and the SDB2_SBE ones too with the tracking enabled this time,as it s the default
• 2026-05-20-07h18m46-UTC  to 2026-05-20-08h39m34-UTC
  • Enable the use of the synchronous mode for  the 3 DAC1955 used for the SDB2 SBE and LC control loops
  • the related parts of the DBox servers, SDB_EDB_dbox_rack and SDB2_dbox_bench, have been updated  by adding for the  DBOX_DAC1955_INPUT_PACKET keyword  "sync" and a "delay value" measured using the command /virgoApp/DaqBox/v17r10/Linux-x86_64-CL7-4.14.111-hal-3-rtai-5.2/DaqBoxCtl.exe -s -m   -e 
  • After these operations,  the SDB2_LC loops were successfully closed and the SDB2_SBE ones too with the tracking enable

Note: the DAC1955 synchronous mode has been deployed  to NCAL NE and WE   DAC1955 boards too :

• WEB NCAL: operations performed between  2026-05-20-09h15m36-UTC and 2026-05-20-09h31m13-UTC, the phase loops were successfully closed after these modifications
• NEB NCAL: operatios performed between 2026-05-20-18h38m05-UTC and 2026-05-20-18h45m18-UTC

Aim:

• Dismount old NNN, NNF, NSN and NSF setups
• Install new NNN and NSN setup
• Recable some channels
• Check position measurements with Survey group
• Check (and if needed correct) the position sensor conventions

Status on arrival (see  old_drawing and pictures NorthBench, EastBench, SouthBench, WestBench):

• NNN:box-2024-10, NNF:2024-13, NSN:box-2024-12, NSF:box2021-07, NEN; 2021-08, NWN: 2021-04
• Noise (sound) levels On North and South setup: Valentin listen to the rotors and determines the FAR rotor (NSF:box2021-07 and NNF:2024-13) are more noisy than near rotors (NNN:box-2024-10 and NSN:box-2024-12) so we keep the Near for next installation. We use the Far rotors as counterweights.
• Survey group (A. Paoli and R. Romboli re-measured the positions of the NEN and NWN rotor (see logbook https://logbook.virgo-gw.eu/virgo/?r=69119). The new results give 3.0444 and 3.0446 meters, about three mm bigger than may 2025 survey.

Old suspended North, East and South setups have been removed (old_drawing , North picture, South picture)

New setups are installed with convention from New_drawing. Cabling have been reshuffled accordingly as well as the DAQ box configuration. Positions sensors are active for all platforms but the motors are not yet ready

Position sensors gain sign have been adjusted to have the direction for all NEB setups with following convention (same as in West end building):

• Lateral, along the x-axis, corresponding to the laser beam (increasing when moving away from the central building)
• Vertical, along the z-axis (positive upward)
• Axial (not lateral as previously stated), along the y-axis, with y = z ^ x

NNN tuning;

• With jigs on NNN plate, adjust the biasis in " virgoData/VirgoOnline/SNEB_dbox_rack.cfg". The mean values (mm) of the position sensors are then (@ 13:53:49 utc with 35 averaging): NNF lateral: 0.0012; NNF Vertical: 0.0004; NNM Axial : 0.0009; NNM Vertical : -0.0013; NNN Lateral : 0.00024; NNN Vertical : -0.00099
• Removing the jigs from NNN, we adjust the plate position untill all sensor measure below 0.06 mm deviation from 0 (see NorthSetupZeroing)

New_drawing and pictures after our work (1, 2, 3, 4, 5, 6, 7)

Yesterday we carried out the survey for measuring the position of the NCal benches @NE. We measured the point on top of the calibrators (Fig.2, Fig.4) for the two benches (east and west side of the tower).

Tab1 reports the result of the survey in VRS coordinates, while the scheme of the survey is shown in the Fig6_SurveyDiagram_Staz01 and Fig7_SurveyDiagram_Staz02.

Fig.1 to 4 report some pictures of the survey carried out, while Fig.5 shows an auxiliary bench placed for the next NCal check survey.

Similar to what was done for the WE building, for the enlargement of the VRS network @NE it was worth confirming the survey done (eLog 69117) with another independent one, carried out with classical tecnique by theodolite and post-processing by compensation software, as we did in the past for all the reference points installed in the Virgo Experimental Buildings (see also VIR-0523AF-13). During last May12-13 we carried out the survey by teodolithe Leica TDA5000 and then the analisys of the raw data by compensationt software StarNet.

Tab1 reports the final result of the compensation obtained showing the VRS coordinates, the standard deviations and the parameters of the relevant error ellipses port the new reference points considered.The resuls obtained are perfectly coherent with those deriving from the laser tracker survey, so that the coordinates of the new points are validated.

Fig.7 reports the whole scheme of the survey carried out, with the graphical indication of the error ellipses, while Fig.1 to 6 shown some pictures of the survey carried out.

Following the installation of the new reference points @NE building (placed as small shelves on the concrete walls of the building and plates on the tower floor), last Apr23 we performed the first survey with the laser tracker Leica AT403.

Similar to what was done for the WE building, we carried out 3 different measures for each of the 4 station in total, at different positions in the building. Each measure has been processed with the Best Fit technique.

Tab1 summarizes the result of the survey in VRS coordinates.

Fig.1 to 6 shown the pictures of the survey carried out and some of the new reference points.

Activities communicated in control room:

• CH laser cooling system installan by Cecilia;
• work on SDB2 LC by Alain;
• Ncal works (Mours);
• INJ: injection chiller checks by INJ team.

While performing these tests, we noticed that the SL crystal temperatures were unusually high.
By checking the trends, we observed that the temperatures started to rise and eventually reached approximately 70°C after the pumping diodes were switched off on 07/05.
This suggests that the temperature controllers are not responding properly in the present configuration.

Under normal operation, both the pumping diodes and the crystals have their temperatures stabilized by the Peltier modules (W signals on the fig attached) in order to maintain the temperatures at their setpoints (SET signals on the fig attached).The hot side of the Peltier modules is itself cooled by the chiller.

Usually, when the pumping diodes and the chiller are switched off, the correction signals go to 100 and everything remains at low temperature.
We had never paid particular attention to this behavior before, but it is already somewhat anomalous, since the controllers should regulate around the setpoints rather than continuously applying maximum corrections.

When we switched off the chiller and the pumping diodes on 08/05, the behavior was different for the crystals: instead of going to 100 as observed for the pumping diodes, the Peltier correction signals for the crystals dropped to 0, and the crystal temperatures started to increase (figure 1)
This behavior is currently not understood. 0 corrections should be the lowest temperature...

The crystals eventually reached approximately 70°C.
When restarting the SL, we will need to assess whether this may have caused any damage and whether the alignment has been affected.

After noticing the issue and we saw that the crystal temperatures were increasing again (figure 2) : without changing anything on the chiller nor the peltier corrections, at 11:30 UTC the temperature of the crystals started to increase again from 40 degrees towards 70 degrees.
So we went to the chiller room to restart the chiller. The Peltier modules only resumed normal behavior once the temperature became close to the setpoint (figure 3).

We found Sa_WI crate off since its power supply was broken (probably due to aging). We replaced it with a spare. Top stage control is now working properly again. 

A selective switch-on test of the Laser system chillers was performed to identify their individual noise contribution to the laser benches.

The test involved the NEOVAN head chiller (Termotec), the main chiller (OMI), and the NEOVAN electronics chiller.

During the test, the AHU used for venting the NI tower remained ON, while the CEB hall and Laser lab AHUs were temporarily switched off and the supply/return air distribution valves together with the outdoor air valves were closed.

The detailed test sequence is reported in the attached file.

The test was completed with all chillers left OFF.

This morning we went in the Eeroom to check the INJ chillers.

- the MAIN CHILLER Omi (which is used for the SL diodes in EEroom, SL crystal in LL and Beam dumps IPC (EIB) + IMC REFL (EIB but not connected) + PMC REFL (LB) + B2 (SIB2) + IPC2 (SIB1 flux blocked)) when switched off was giving the error A05. We changed the filter and switched it on and it was working fine. We switched it off again.

- the NEOVAN HEAD CHILLER Termotek (used for the Neovan head). We switched it on with the circuit closed on itself and this time the pump started (we observed this behaviour also in the past, maybe due to the air which enters while changing the filter)