Similar tests for studying acoustic modes of the laser bench room were made back in 2024 but with the HVAC on and no much effect was seen: https://logbook.virgo-gw.eu/virgo/?r=65126
The microphone added externally of the laser bench room is named ENV_CEB_LLR_MIC, the microphone insided the is named ENV_LLR_MIC.
In order to see the main laser beam on NE mirror and to re-align it, the pcal NE has been switched off on July 29 at 12:19 utc.
06:45 UTC - NI Large valve open. Laser beam on north arm.
Before attempting the relock of the arms foreseen next days today I tried to asses the actuation balancing of the WI and NI payload at the level of the MAR, due to the new mounted payloads.
The coupling between Z corr and TY corr have been evaluated through some DC steps applied in Z corr, in order to compute the correct driving weigths to minimize such coupling. Both for NI and WI the misbalancing was quite high.
For WI the found value was 0.0046 (from 0.0002), directly applied in the branch that feeds part of the Z corr in TY MAR corr, see Fig.1. Further fine tuning are not appreciable since we are covered by corr signal noise.
Once we have a lock, by measuring some TF between the corrections, it will be easier to estimate the finer weights.
For NI the found value was quite high with respect to the current one, but I didn't implemented it since for NI is not possible to see at a first sights the effect of the driving adjustment due to the way the corr probes are implemented in the DSP card. So I will leave it for tomorrow.
Same decoupling procedure has been applied also to minimize z2roll coupling z-> tz corr, fig.2. (WI weight: from 0.0115 to 0.0104; NI weigth: from 0.00374 to -0.01326)
N.B. MIR coil balancing both for NI and WI need yet to be done.
Motivation: the first scope is to study the sound transmission between the CEB hall and the two labs: in order to quantify the contribution from the CEB HVACs this time we first switch off the INJ and DET labs HVAC and THEN the hall and CleanRooms HVACs. Also, we perform a white noise injection with one of the two sub-woofer positioned in the DET terrace. The second purpose is to study the origin of the low frequency peaks at approximately 12 Hz and 19 Hz which are clearly seen by microphones when the INJ HVAC is off (previous investigations: elog https://logbook.virgo-gw.eu/virgo/?r=69148).
Preparation (this morning):
Action times:
The laser lab temperature increased by 1deg overall as shown in Figure 2. The weather conditions were good, with low wind (also in Fig.2). Analyses will follow.
Similar tests for studying acoustic modes of the laser bench room were made back in 2024 but with the HVAC on and no much effect was seen: https://logbook.virgo-gw.eu/virgo/?r=65126
The microphone added externally of the laser bench room is named ENV_CEB_LLR_MIC, the microphone insided the is named ENV_LLR_MIC.
As rotors were moved, the hInj values change.
All values have been updated in NCalMoni.cfg, /virgoData/NCal/set_NEB_default_lines.sh and /virgoData/NCal/set_WEB_default_lines.sh. after new fromage simulation.
Values will need some more tuning as:
-WEB mirror position needs to be determined
-NEB rotor survey was not complete
On Friday, July 24, we performed an environmental noise characterization of one of the two chillers of the auxiliary CO2 laser cooling system. Since the installation had not yet been completed, the chiller was connected only to the tank, with both components located in the TCS chiller room.
A microphone was installed on the right-hand side of the room, immediately to the right of the entrance. An accelerometer and a triaxial magnetometer were instead installed, in turn, first on the floor next to the chiller and then directly on top of the chiller, Figure 1-6. The sequence and timing of the different measurement configurations are reported in the attached file.
Noise inside the TCS chiller room
*** Seismic ***
Figure 7 compares the vibration spectra measured under the different operating conditions. The highest vibration levels are measured when the accelerometer is mounted directly on top of the chiller (yellow and violet curves). Even when the cooling fan is not operating (violet curve), the vibration level measured on top of the chiller remains significantly higher than that measured on the floor, indicating that other components of the chiller continue to generate vibrations. Only after the chiller is completely switched off does the vibration level measured on top decrease by several orders of magnitude, becoming comparable to the floor measurements.
When the cooling fan is operating, spectral lines are observed at approximately ~22.5 Hz and ~112.5 Hz. The 22.5 Hz component is consistent with the fan rotational frequency, while the 112.5 Hz line corresponds to the blade-passing frequency (Fbpf=Npale*Frot) of a five-blade fan. These two spectral features are consistently observed in both the acoustic and magnetic measurements, Figure 8, 9.
Additional spectral lines are observed at approximately ~47.8 Hz and ~48.9 Hz. The 47.8 Hz line is present both with the cooling fan on and off and disappears only when the chiller is completely switched off, indicating that it is associated with a component operating continuously while the chiller is powered.
Following the inspection carried out by Cecilia, the circulation pump nameplate was found to report a nominal rotational speed of 2850 rpm, corresponding to a rotational frequency of 47.5 Hz, in good agreement with the measured line. This supports the attribution of the 47.8 Hz feature to the circulation pump. The 47.8 Hz spectral line was also observed when the accelerometer was mounted on the supply water pipe connecting the chiller to the tank, Figure 22.
The ~48.9 Hz line is observed only during the fan-on periods (blue and yellow curves in Figure 10 ), suggesting that it is associated with a component operating only during the cooling phase. Both spectral features are also identified in the acoustic and magnetic measurements, Figure 11.
*** Acoustic ***
The acoustic spectra show no significant variation below approximately 40 Hz. During the cooling fan-on condition (blue and yellow curve), a clear increase in acoustic noise is observed mainly above about ~40 Hz, with both a broadband contribution and several narrow spectral features, Figure 12.
***Magnetic ***
The three components of the triaxial magnetometer exhibit a similar overall behaviour, Figure 13,14,15.. When the cooling fan is operating and the magnetometer is placed directly on top of the chiller (yellow curve), a pronounced spectral comb with an approximately 2.5 Hz spacing is observed over a broad frequency range. A similar spectral structure is also visible when the magnetometer is placed on the floor (blue curves), although it is less regular and has significantly lower amplitudes.
In the ~1–3 Hz range, an increase in magnetic noise is observed both during the cooling fan-on and fan-off conditions compared with the completely switched-off chiller. The low-frequency magnetic contribution could be generated by components that remain active while the chiller is powered.
Noise outside the TCS chiller room
The following observations summarize the environmental noise signatures associated with the operation of the auxiliary CO2 laser chiller outside the TCS chiller room.
Today we moved both BS and WI using the old references of the optical levers, and we could find also the WI-reflected beam on the B4 camera. Both reflected beams are now visible (the third one is the second reflection of the NI one).
Actvities communicated in control room:
At the end of the shift Diego started to work at NI/WI mirror alignment.
SBE
SWEB and SNEB opened by the guardian; properly closed at 9:42 UTC.
We tried to recover the alignment of the NI using as a reference the camera image on B4 and the DC power signal. We explored several position both of NI and WI, by moving the local controls (and PR and BS for checks). We maybe were able to find the main beam on B4 cam. Tomorrow we will continue.
Today we moved both BS and WI using the old references of the optical levers, and we could find also the WI-reflected beam on the B4 camera. Both reflected beams are now visible (the third one is the second reflection of the NI one).
The shift was covered first by Lunghini and then by Zaza
Lunghini's report:
ITF in UPGRADING Mode and DOWN State.
All times are UTC.
Below the activities communicated to the Control Room:
07:35 - 07:46 TCS: Update NE/WE RH Powers and Turning ON SR RH (Lumaca, Corubolo, #69444);
08:49 VAC: Re opening of NI-BS, NI-PR, and NI Cryotrap Large Valves (Vacuum Team, #69446);
10:36 NEB/WEB safety laser inspections (Galimberti);
10:36 ALS: NEB turning ON amplifier (Lagabbe);
12:55 Re opening of BS-SR, BS-WI Large Valves (Vacuum Team, #69450);
Zaza's report:
13:45 UTC SDB1 camera realignment (Boldrini, Lagabbe)
14:00 UTC WE, NE RH V flags thresholds adjusted (Zaza, Corubolo, Lumaca)
6:00 UTC on: old TCS auxiliary cooling system removed, new system connected to the lasers (Ciardelli, Menzione, Zaza).
15:20 ALS: WEB turning ON amplifier (Lagabbe)
On July 26, at 15:08 UTC, the IMC unclocked, which causes the BPC error signals to go away since they follow the IMC reflected signal.
After investigation, it appears that the PMC transmitted power signal started oscillating around 15 s before the IMC unlock. Which causes both the IMC and PMC to unlock. The PMC relock automatically a few second after the unlock, but the IMC could not because the BPC misaligned the laser beam with the IMC.
We don't know yet what causes these oscillations. The PCM error signal was stable before the unlock, as well as the slave laser cavity. The master laser power signal and frequency correction signals seem stable enough. The PSTAB tried to compensate for these oscillations, but at some point, the AOM started to saturate.
We don't know neither why the BPC did not come back to its previous position after the IMC unlock.
On July 27 at 8h08 utc, the BPC loop filters have been reset and the IMC and RFC have been relocked.
The ipcamz3 camera was re-oriented in order to better view the sdb1 bench.
To access the camera view: http://ipcamz3/
login: root
password: tocaxis
The Vacuum Team it's going to reopen the following Valves as planned:
- BS-NI Large Valve;
- BS-PR Large Valve;
- NI Cryotrap Valve;
The beam will be able to reach NI Tower.
The Vacuum Team it's going to reopen the following Valves as planned:
- BS-SR Large Valve;
- BS-WI Large Valve;
The beam will be able to reach WI and SR Tower.
Retune the offset of the NEB north and West NCal tremerature sensor.
After NCal maintenance operation (see lgbook https://logbook.virgo-gw.eu/virgo/?r=69385), the temperature sensors of NNN and NWN changed their calibration (see https://vim-online.virgo-gw.eu/resources/2026-07-20/resources/20260720_cal_ncal_temp.png).
Between 8:40 and 9:03 UTC this morning, I modified offsets in /virgoData/VirgoOnline/SNEB_dbox_rack.cfg to recover a 22.5° += 0.1° on all sensors when rotors are off.
New values are :
| Sensor name | Offset |
| NNN box | 0.059 |
| NNN rotor | 0.075 |
| NWN box | 0.047 |
| NWN rotor | 0.074 |
July 23rd entry, published on July 27th due to network issues on the 23rd
ITF in UPGRADING, DOWN
Activities communicated to the control room:
CEB laser safety inspection (Galimberti)
TCS aux cooling system final assembly (coarse control side) in preparation for tomorrow's ENV tests (Ciardelli, Gherardini, Menzione, Zaza)
At 7.40 UTC, the SR RH was switched ON and the voltages of the RHs on the terminal mirrors were updated as follows:
ITF DOWN and in UPGRADING Mode.
All times are UTC.
Below the list of activity communicated to the Control Room:
07:37 - 09:17 INJ: Tests on PSTAB feed forward 50/250 Hz lines (Was, #69435);
08:28 - 11:02 ENV: Noise check on TCS chillers (Fiori, Tringali, Dattilo);
11:56 -1351 ALS: Turning on NEB amplifiers (Lagabbe, #69439);
12:11 - 15:05 ENV: Noise check on TCS chillers (Fiori, Tringali);
14:10 - 14:48 Lagabbe and Boldrini in Laser Lab to flip a mirror for ALS (#69439);
We went to NEB in order to switch on the laser amplifier on the ALS rack (kheopsys), but the input laser of the amplifier was missing. This amplifier requires 0 dBm of input power but its internal sensor shows -5.4 dBm.
After investigation, it appears that the power that is sent to both ALS_NEB and ALS_WEB was cut off at the same time on May 6 2026, which indicates that the problem comes from EIB. The flip mirror has been switched to block the laser beam that goes toward ALS green laser generator.
Now the ALS_WEB amplifier works properly, but the power at the output of the ALS_NEB amplifier is still missing. It is required to go to NEB again to switch on the amplifier
Following the previous temperature sensor tuning (https://logbook.virgo-gw.eu/virgo/?r=69362), I complete the procedure for WEN aand WWN box sensors to have all WEB temperature sensors within 0.1°C.
For this, I applied offsets of 0.025 V for WEN box and 0.002 V for WNN box. For memory, the temperature change for a 0.1 V offset are respectively 3.34° and 3.20° for WEN box and WNN box.To align the sensor values on the motor values,
Implemented the 50Hz and 250Hz line feed forward into the PSTAB, it works but the target signal needs to be replaced by one which is not contaminated by the 50Hz harmonics.
7:38:40 UTC restarted ISYSnoise without changes in the configuration file,
other than putting PSTAB1 line amplitude to be the same as in the
External file. This unlocked the injection which then relocked after 1 minute.
After fixing some forgotten copy pastes, and adjusting the feedback
sampling frequency could restart the ISYSnoise process. Also added
buttons to turn the FF on and FF into the VPM interface.
08:23 UTC (3min) 50Hz feed-forward on with automatic tracking converged.
It is effective at removing 50Hz from PSTAB channels, both PDa and PDd
simultaneously, but 50Hz harmonic remains on RFC and B2 spectrum,
where they are reduced only by a factor 1.5-2. It is somewhat not
suprising as the 50Hz is polluting the PSTAB photodiodes sensor, so
minimizing the 50Hz in the PSTAB sensor does not improve the light
power stability. Need to use a sensor that is not contaminated by 50Hz
harmanics, the RFC reflection photodiodes can be good candidates as
they are in vacuum and with a differential read-out of the photodiode signal.
09:03 UTC (6min) 50Hz and 250Hz FF on with aumatic tracking
09:10 UTC (6min) 50Hz and 250Hz FF off
Figure 1 shows the result of the feed-forward on the 50Hz lines, it is
reduced by ~2 orders of magnitude on both PSTAB photodiodes (PDa is
the one which is in loop), but for signals without 50Hz contamination
(RFC, B2, the improvement is less than a factor 2). Blue shows data
with the FF enabled and purple with the FF disabled
Figure 2 shows the result for the 250Hz line, where the environmental
channel has less clearance between the 250Hz line and the measurement
noise, so the FF is effective at removing the line but adds a wide
bump around the line.
Figure 3 shows some of the FF channels when the loop is open.
Leaving the FF off as it doesn't have a protection to not misbehave
when the injection is unlocked. Next step is to add the RFC Audio
channel to RTPC19 so it can be used as a target channel for the
feed-forward.
On Wednesday Angelo and I went to the WI tower to install a prototype for a camera holder that also covers the exposed viewport.
This first version of the holder is made by a metal bracket that is tightened around the flange (NOT the viewport itself, to avoid mechanical stress on the glass) and then a metal cylinder that envelopes the camera and obstructs the viewport.
The figures show the assembly stages. Fig.2,3 in particular show the camera cables exiting the envelope through a thin slit on its bottom side.
The holder is currently installed, so the risk of accidental exposure to 1064 nm light inside the tent around the WI tower is greatly reduced.
We are considering successive iterations made of PVC to further diminish the risck of applying mechanical stress on the viewport and to possibly introduce some ability to adjust the camera. Another feature we would like to introduce is to remove the need for tools to open/close the assembly and move the camera, as currently a #8 wrench is required for these operations.
