The "tranfer function" measured in the previous logbook entry is the tranfer function from a noise injected before the driving matrix and after the filter, to the normalized signal of the quadrants. So when we inject a noise on one of the TILT/SHIFT signal, this noise is only visible on the corresponding quadrant signal. In the example given in the  logbook entry, the noise is injected on TILT_X signal, and arrives on the far-field quadrant horizontally. The next image is a scheme of the BPL loop with the injected signal :


Another remark: EIB was not suspeded when preforming all the measurements. So they have to be repeated with the EIB suspended, which may affect the measured sensing matrix, and so the corresponding driving matrix.

The sensing and driving matrices measured in the precedent post 69150 were wrong, due to an error on the threshold on the phase that separates the positive from the negative responses between the piezo and the quadrants. The new matrices were computed:
sensing_matrix =
   -0.6230   -0.0278    0.0033    0.0012
    0.0233   -0.3838   -0.0010   -0.0059
   -0.5035   -0.0063   -0.4332   -0.0151
    0.0154    0.3421    0.0166   -0.2886

driving_matrix =
   -1.5909   -0.1001    1.8540   -0.0972
    0.1081   -2.5520    0.0166   -3.0190
   -0.0128    0.0071   -2.2893   -0.1237
   -0.0080    0.0517    0.1270   -3.3971
 
Using the new driving matrix, we managed to lock the BPL loop in drift control (f < 5 Hz). And then in broadband.
When the BPL is locked in broadband, a 122 Hz signal appeard on the QPD signal spectrums.
 
 
In order to measure the open loop transfer function, the BPL loop was open and a colored noise signal with a 0.001 V amplitude was injected on the channels:

• TILT_X_CORR 13:42:00 UTC
• TILT_Y_CORR 13:45:30 UTC
• SHIFT_X_CORR 13:48:40 UTC
• SHIFT_Y_CORR 13:52:00 UTC

To see the transfer function at low frequency, a 0.03 V signal at frequency < 20 Hz was injected on the same channels at the times:

• TILT_X_CORR 14:27:00 UTC
• TILT_Y_CORR 14:30:00 UTC
• SHIFT_X_CORR 14:32:30 UTC
• SHIFT_Y_CORR 14:36:00 UTC

 The shape of the open loop transfer functions from the CORR signal to the corresponding of the quadrant signals are similar. The following plot is a  transfer function from TILT_X_CORR signal to QF_h_norm during a low frequency injection:

 
The 122 Hz noise was due to a saturation of the control loop, so the loop filter was changed. The QPDs signal spectrums in closed loop, with the old and with the new filter are shown in the following plot:
 
The 122 Hz signal disapeared.

ITF DOWN in UPGRADING mode.
Operations carried out throughout the day:

• FCIM test by HVAC: conditioning turned off for 24 hours
• FCIM_SBE and FCEM_SBE position loops closed (likely opened by yesterday's earthquake in Calabria)
• MC loops were also open and when closing them they showed high corrections. After a quick evaluation (Pinto, see #69153), given the fact that motor UI was not responding, I called Boschi. He noticed an issue with TANGO, problem fixed by Carbognani (server restarted)
• MC IP centered (#69156, Boschi)
• SAT PDU sockets signals have been showing alternating missing data since the computing shutdown on Apr 7th, SUS and DAQ problems have been ruled out (Boschi, Masserot). I notified service. Work in progress
• DET vacuum chamber external inspection (VAC group)
• BPL commissioning (INJ group, Pinto, Ruggi)
• Infrastructure assessment in TCS chiller room to remove the door as part of AUX cooling system upgrade after past weeks' floor renovation (Fabozzi, Marano)
• NI CP mount assembly (Naticchioni, Benedetti)
   

Motor interfaces were not working since the relative TANGO servers were down. I recentererd the IP using the centering script. Now F0 positions should be fine.

When Cecilia tried to close the controls through the operator interface, the setpoints both of TOP stage and BOTTOM stage changed with respect to the used values, see fig.1. This issue has already been observed in 68701.

F0_X_SET: from -2000 to -450

MAR_TX_SET: from -104 to -20.5

MAR_TY_SET: from 163.5 to 144.

Maybe the setpoints have been changed without saving the values in DSP card and have been overwritten to older values.

Correct setpoints have still to be 'recovered'.

On june 2nd at 14.52 UTC the control of MC suspensions opened. Now the top stage controls can't be closed again since the suspension is far away from the setpoints, it should be recovered maybe through the motors, but the motor UI is not working. Experts should address  the issue.

To measure the sensing and driving matrix of BPL, a sinusoidal signal at 2 Hz, with 0.2 V amplitude was injected on channels:

• PZT_EIB_M1BH_CORR
• PZT_EIB_M1BV_CORR
• PZT_LB_M14H_CORR
• PZT_LB_M14V_CORR

Directly on the piezo correction signal. The BPL loop was open while injecting noise.

The signals were injected respectively at GPS times [1464363022, 1464363121, 1464363296, 1464363397] , each injection lasted for 60 s.

The channels QF_h_norm, QF_v_norm, QN_h_norm and QN_v_norm were monitored to see the effect of each piezo on each quadrant.

Piernicola's matlab script "Sensing_matrix_BPL.m" was used to compute the matrices:

sensing_matrix =

   -0.6230   -0.0278    0.0033    0.0012
    0.0233   -0.3838    0.0010   -0.0059
   -0.5035    0.0063    0.4332    0.0151
    0.0154    0.3421    0.0166    0.2886

driving_matrix =

   -1.6099   -0.1078   -1.8808    0.3216
    0.1242   -2.6459    0.0738    3.1261
    0.0118    0.0090    2.3271   -0.1449
    0.0085   -0.0545   -0.1126    3.5359

However, the loop does not close. We tried to adjust the setpoint of the piezo (TILT/SHIFT_X/Y_CORR_SET) so as the norm signal of the QPDs come close to 0, and tried several values of the DRIFT_FILTER gain but we did not succeed.

Paolo got a similar driving matrix, the values of the set point has to be studied more deeply.

One of the performed tests consisted in closing the air valves of the inlet and outlet ducts while the HVAC was off. Acoustic modes of the ducts themself,  associated to air pressure waves resonating inside the ducts, would be affected changing their frequency or reducing. A similar test has been done for DET: https://logbook.virgo-gw.eu/virgo/?r=69058

The plots compare microphones inside the inj lab (and the horizontal accelerometer on LB) at two times with HVAC off: ducts open (blue) and ducts closed (purple). No significant change is observed.

The purple curve shows extra noise due to the fact that on May 19 the Tower HVAC was on (NI open). The blue line in Figures 2 and 3 was taken on April 14 2025 when the ambient noise outside the lab was much quieter (also the CR HVAC responsible a 18.5 Hz line was turned off at that time). 

Figure 3 zooms in the bumps region. Acoustic bumps peaks at 12.07 Hz and 18.20 Hz. The seismic bump present in the laser bench peaks at 18.06 Hz.

In 2021we did tests of mechanically stimulating the LB and measured a mechanical mode of the bench around 17Hz: https://logbook.virgo-gw.eu/virgo/?r=50496. This seems not present now... did it move to 18.06? Could be tested by tapping the bench.

Data sheets of the Quantum gravimeters are now available in the Environmental Monitoring Sys > Sensors and Tools > Documentation: https://scientists.virgo-gw.eu/EnvMon/List/Gravimeter/

ITF DOWN in UPGRADING mode.

Activities communicated to the control room:
- 07:00 UTC - NI CP mount assembly (Travasso)
- 08.40 UTC - STAC site visit (Zaza)
- 12:40 UTC - sniffing for 1Hz magnetic noise in CEB area (Tringali , Fiori)
- TCS Chiller assembly & test at 1500W (Zaza, Ciardelli) in progress.
- NI cleaning (Clean Op team) postponed.

Activities communicated to the control room:

• Confined space safety training

• NI CP mount assembly (Travasso)

• TCS Chiller assembly & test (Zaza)

I confirm that NI tower is still safe wrt laser hazard

This morning from 10:30h to 11h LT we went to the laser lab to realign the beam onto the PMC. We slightly improved the power transmitted by the PMC (Fig. 1) looking at the reflection of the cavity and trying to minimize the 01 mode on the oscilloscope. Afterwards, we flipped down the mirror at the end of the Laser Bench to allow to beam to reach the BPL loop so we can work on it in the next days.

Since May 17 the gravimeter was not reachable from remote. This has been fixed today. Attached are two pictures of the gravimeter (Fig.1) and the laser box (Fig.2).

The issue was with the USB-to-RJ45 adapter, which for some reason was not working properly (the network communication LEDs were off, and the network interface was also disconnected from the console). After unplugging and reconnecting it, the connection was restored, but it went down again a few minutes later. The procedure was repeated, and the connection was re-established. Now, after returning, the machine appears to still be up and running.

Measurement continued through the Cascina holiday, and approximately 48 hours of data was stored.

I evaluated the ASD peak heights for the 1 Hz comb and 50 Hz power line hourly, and plotted their median, max, and min values.

To eliminate calibration uncertainty, the values are expressed in counts.

The median value of the 1 Hz peak was highly stable, whereas other metrics showed temporal variation.

Graphs show data of the accelerometer installed (vertical) on the floor next to the Gravimeter. Fig.1 shows that the noise conditions is more or less stable over 24 hours. Figure 2 compares the spectral noise with one accelerometer sensor (vertical) on the CEB floor (near Guralp). The Fiber lab floor is noisier above 10Hz and below 1Hz.