Around 11:30h UTC I went to the LL and blocked the beam at the output of LB to allow works on the EIB for the excess noise found since last Friday (see #69600). BPC loop is open and INJ node in metatron is in down and paused.
WE WRITE AND POST THIS ENTRY A SECOND TIME SINCE IT WAS ERASED FROM THE LOGBOOK AFTER OUR FIRST ATTEMPT.
This morning we performed another round of alignment checks after the intervention in SDB1.
Air flux is off, BS-SR valve open to let the NI single bounce beam reach the SDB1 bench, nitrogen blowing on the cryotrap window.
The suspension control of SDB1 were restored by Paolo yesterday night. SDB1 angular control are closed.
Noticing that the height of SBD2 has drifted away during the night, we remove a few temporary weights to adjut the bench height close to 500 um. Then we close SDB2 angular and position loops.
We then check the position of the beam on B1p camera. it is too high. Thefefore we change the SDB1 angular setpoints to recenter it : in TX setpoint changed from 60 to 15 um, in TY setpoints changed from 20 to 27 um. After this adjustment we checked the position of the B1s beam on the silicon beam dump on SBD2 (using an IR card) and it was found well inside the beam dump.
We open the OMC shutter and check that the B1s beam is well centered in its camera (Fig.1). Initially we read a power of about 40 mW on B1s (Fig.2). Then we checked that the B1s beam is still passing through the iris placed at the input of the EDB bench.
We performed an OMC scan and found the following powers per mode:
- TEM00 mode: containing a power of 1uW (see Figs. 3 and 4)
- 1st HOM: containing a power of 2uW (see Fig. 5 and 6)
- 2nd HOM: containing a power of 1.8uW (see Fig. 7 and 8)
- 3rd HOM: containing a power of 2uW (see Fig. 8 and 9)
- 4th HOM: containing a power of 2uW (see Fig. 10 and 11)
- 5th HOM: containing a power of 2uW (see Fig. 12 and 13 )
This makes a total of 10.8uW. Assuming a calibration factor of 4800 on B1_PD3, we get a total power of 52mW, compared to the B1s power of about 70mW.
We check that the B1p, B1s and B5 galvo loops centering is working well (Fig.14). In order to be able to close the B5_QD1 galvo loop we had to perform a little adjustment (order of 1500 counts) with the picomotors B5_M2. REMEMBER TO UPDATE THE NAMES OF THE PICOMOTORS WHICH ARE NOW VERY CONFUSING (B5_M1 for B5_QD2 now on the B1s beam, versus B5_M2 for B5_QD1).
This concluded our alignment check.
We close the OMC shutter, open the SDB2 local controls. Remove SDB2 temporary weights, remove EDB irises.
We close the SDB2 vacuum chamber and starts the pumping around 10h30 utc.
We ask the VAC team to close the BS-SR valve as we do not need the laser hazard in DET tower any more. The air flux in the tower is switched back on. We close the nitrogen bottle.
Access to the room under the tower is now allowed.
No laser hazard can propagate to the SDB1 tower.
We inform the Laser Safety Officer that laser hazard it not needed any more inside the DET tower.
After the daily meeting we started the intervention in SDB1.
After switching off the laser; we entered the tower and started by blocking SDB1. Then, we inspected the bench. We did not notice any anomaly. Hence, we proceeded with the closing and reopening of the fast shutter after verifying the blades were ok.
We then removed the waveplates and their corresponding clamp and screw (539g). We did not remove the beam dump placed in reflection of the waveplate. To be noted that we did not replug the cable that was used for the waveplate (as there was not easy access to recable it to the B5_M1_TX picomotor).
We then unplugged the OMC shutter translation stage. We dismounted the translation stage and replaced it with the spare one. We repluged it and tested successfully.
We add 540 g of weight under the bench to compensate for the weight of the withdrawn waveplate.
We recenter the motorized weight manually.
We then rebalanced the bench and left the detection tower.
However, we noticed in the control room that the TX position has drifted away a bit and the loop could not be closed any more. To fix this we performed -34000 steps with the BENCH_TX motorized counter-weight. We could then close the angular loops as shown on the attached Figure. We notice large fluctuations in TX and TY (+/-10 urad). This may be due to the presence of the air flux in the tower and maybe the thunderstorm.
We leave the tower slightly open, with nitrogen off, and air flow blowing.
Tomorrow, after the recovery of the suspension control, we will perform an alignment verification.
ITF found in COMMISSIONING Mode and DOWN state, with MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node (equal to SINGLE_BOUNCE_NI state from ITF_LOCK)
7:30 UTC OB Top Stage loops opened (operator), DAQ reconfiguration (Masserot), Closing of BS-SR valve (Pasqualetti), SDB1 rack cables swapping (Gouaty, Romero)
8:00 UTC Opening of SDB1 tower bottom flange, hood with nitrogen flow installation on cryotrap viewport (Vacuum team)
8:12 UTC SDB2 LC troubleshooting and rebalancing (Gouaty, Romero)
9:30 UTC Opening of SR-BS valve (Pasqualetti)
12:00 UTC INJ troubleshooting on EIB (Gosselin, Melo, Ruggi)
12:30 UTC Closing of SR-BS valve (Pasqualetti)
13:00 UTC entering SDB1 tower to change OMC shutter traslation stage (Gouaty, Romero, Menzione)
At 14:00 LT, we went into the LL to perform a more detailed inspection of the EIB bench. We first put the beam in scan mode and blocked it at the LB output.
We then opened the bench controls and slightly moved the plexiglass tube leading to the SIB1 tower, as it appeared to be in slight contact with the bench. However, a comparison of the FFT signals before and after the intervention showed no significant change, suggesting that the contact was not the cause of the excess noise. No other obvious issues that could explain the increased noise were identified during the inspection.
We then unblocked the beam, re-locked the INJ system, and left the LL at approximately 14:40 LT.
Afterwards, we continued analysing the data. Paolo identified some LVDT signals, particularly the vertical 0 and 2 channels, that are significantly noisier than they were previously (see Fig. 1). A similar issue appears to have occurred in the past (see #57229), where the solution was to implement a low-pass filter to attenuate the excess noise.
It would therefore be useful to investigate whether this filter is still correctly implemented and functioning, or whether another issue is currently responsible for the additional LVDT noise.
Today, after the venting of the SDB1 tower was completed, the VAC team opened the SDB1 tower around 08h30 utc and installed the nitrogen setup blowing on the cryotrap window.
Meanwhile we performed some actions on the SDB1 rack:
➢ disconnect the SDB1 waveplate that we are going to remove from Agilis driver AG_UC8, channel 3 axis 2.
➢ Replug the cable on the picomotor driver 8742 SN 10592, channel 4 (B5_M1_TX)
The VPM main configuration has been updated accordingly to remove the button related the driving of the Pre-Faraday waveplate under SDB1_Rot process.
Noticing that the height of SDB2 bench had changed during the night, we went inside the DET lab to remove some mass from the bench and we were able to recover the right height, and to close the angular and position loops. However we lost the DAQ box LeftUp shorhtly after. So we had to reopen the control loops.
Paolo recovered the SDB1 bench position and the SDB1 local control could be closed.
We adjust the gain of the OMC Peltier to 20 (instead of 50) in order to be able to control the OMC in air. OMC temperature stabilization closed at 9h33 utc.
SDB2 control restored at 10h14 utc.
Antonio switch off the air flux inside the tower at 10h20 utc.
We take some alignment references with NI single bounce beam:
* SDB1 LC is set to TX = 60 (instead of previous WP at 120) / TY = 20 (instead of previous WP at 60)
* B1p camera is centered, with Pos X = -0.1, Pos Y = +0.15
We open the OMC shutter at 10h42m50 utc. We have 4 mW on the B1s beam. The beam is centered on B1s camera at position X = 0, Y = 0
To be noted that we observe an electronic offset of 31.2 mW on DET_B1p_DC when B1p_PD2 shutter is closed. We read 34 mW when the shutter is opened, which implies a power on B1p beam equal to about 3 mW which is in reasonable agreement with B1s power.
We open B1 PD1 and PD2 photodiodes at 10h52 utc.
We scan the OMC and observe the following modes:
* 0.1 mW on the TEM00
* 0.17 mW on the first order mode
* 0.3 mW on the second order mode
* 0.5 mW on the order 3
* 0.5 mW on the order 4
* 0.21 mW on the order 5
We close the OMC shutter, open the controls. Next step will be to perform the foreseen installation works inside the tower.
All the SDB2 DBoxes wer reconfigured but without any improvments .
As trial the output of the B5_QD1 and B5_QD2 demodulation sample data were commented and in these conditions , all the data were correctly received by the SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout servers.
To restore all the SDB2 demodulation sample data, for all the demodulation sample output packets the output frequency is now set to 2kHz instead of 5kHz with 16 words of 32bits.
Labels are in place and the laser hazard can be turned on following the authorized procedure.
No other laser hazard can be turned on and propagated to the SDB1 tower.
Access to the room under the tower is now allowed.
No laser hazard can propagate to the SDB1 tower.
We ask to the Laser Safety Officer the authorization to turn on the laser hazard inside the detection tower, by opening the BS-SR valve.
Please confirm that no laser beam hazard (Nd-YAG, CO2, etc.) is present inside the DETECTION tower
Nevertheless, we have some extra noise in the band 1-10 Hz. I checked all raw signals (voice coils, geophones, LVDTs) and they seem all correct. I switched off the MotorSAS process in the vpm, since the driver coils can make electronic noise, but that did not change anything. In the evening when Romain gave the green light, I switched off controls, switched on viscous damping, and switched on the full pid. With the full pid the ground motion is damped well below 1 Hz but there is an extra shoulder between 1-10 Hz. I think it arises in Tx and Tz and is coupled to Ty,x,z via the tilt stabilization but this is just conjecture. Suzanne did not find anything rubbing against the bench, but maybe there is some small detail. I did not see much difference in acoustic noise (such an effect on the bench, bypassing the floor, could maybe cause such a shoulder) and I checked that the actuators and pid have the same transfer functions as last week (plotting the transfer function from actuator current to bench motion) so it is difficult to find the cause of the extra noise now; it seems all sensors and actuators are performing as well as last week,
The only "large" difference is that there is now some 10 times more noise at the secondary microseismic peak (0.3 Hz); this peak is damped well. It should not spoil the pid at 3Hz, but we may hope for improvement on a quieter day.
Included are the files of the d.o.f. and time signals of the actuators with actuation off/only viscous (first attachment), actuation off/pid (second attachment), a comparison to last week (3rd file), and the raw signals/seismic motion for today and last week (4th and 5th file). The excess noise shoulder is obvious, but the damping is good at 0-1 Hz and similar at +10 Hz.
At 14:00 LT, we went into the LL to perform a more detailed inspection of the EIB bench. We first put the beam in scan mode and blocked it at the LB output.
We then opened the bench controls and slightly moved the plexiglass tube leading to the SIB1 tower, as it appeared to be in slight contact with the bench. However, a comparison of the FFT signals before and after the intervention showed no significant change, suggesting that the contact was not the cause of the excess noise. No other obvious issues that could explain the increased noise were identified during the inspection.
We then unblocked the beam, re-locked the INJ system, and left the LL at approximately 14:40 LT.
Afterwards, we continued analysing the data. Paolo identified some LVDT signals, particularly the vertical 0 and 2 channels, that are significantly noisier than they were previously (see Fig. 1). A similar issue appears to have occurred in the past (see #57229), where the solution was to implement a low-pass filter to attenuate the excess noise.
It would therefore be useful to investigate whether this filter is still correctly implemented and functioning, or whether another issue is currently responsible for the additional LVDT noise.
Today I reconfigured the 4 DAQ boxes of SDB2 in order to solve timing issues resulting from our intervention on the bench.
The reconfiguration took place between 21h59 and 22h03 utc.
The Timing flag in the DMS is back to green, however, since the reconfiguration the processes SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout seem to be misbehaving. A DAQ expert has been informed;
All the SDB2 DBoxes wer reconfigured but without any improvments .
As trial the output of the B5_QD1 and B5_QD2 demodulation sample data were commented and in these conditions , all the data were correctly received by the SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout servers.
To restore all the SDB2 demodulation sample data, for all the demodulation sample output packets the output frequency is now set to 2kHz instead of 5kHz with 16 words of 32bits.
As agreed during the daily meeting, we post this entry to inform that we have completed our activities on SDB2, and we do not need the NI single bounce beam any more until the SDB1 tower venting is completed (tomorrow morning).
Today we continue the work on SDB2 bench.
We open the OMC shutter at 07h52 utc.
We decide to use B5_QD2 instead of B5_QD1 in order to shorten the optical path up to the galvo and increase the distance between the galvo and the QPD of B1s.
We displace the B5_QD2 quadrant by -150 mm in X. Its galvo was also translated by -125 mm along X. The distance between the galvo and the B5_QD2 oblong hole is now 275 mm.
With this reshuffling we should have preserved the Gouy phase tuning performed yesterday with B5_QD1. In other words the optical path length from the lens to the B5_QD1 should now be the same as the optical path length that we had adjusted yesterday between the lens and othe B5_QD2.
After this change we align the B1s beam on the B5_QD2 quadrant by acting on the picomotors of B5_M1 (-4200 steps in H, -14000 in V) and we managed to close the galvo loops as shown on Fig.1.
We placed a beam dump for the reflection from the quadrant.
We realigned the galvo and QPD B5_QD1 on the B5 beam. We acted on B5_M1 picomotors.
We realigned the beam on B5P_PD1 using the motors of B5_M3. Then we realigned the beam on B5_PD2 by adjusting laterally the photodiode position and acting with B5_M4 (see Fig.2).
Finally we realigned the B5 beam on the camera (see Fig.3) by displacing the camera by 5mm towards east and by vertically adjusting the beam position with the last folding mirror.
To be noted: we had difficulties in seeing a beam on B5_PD1. we suspect that its shutter was stuck in the close position. When it opened we could rapidly realign it.
During this intervention, the elements we have removed and/or added to the bench:
- Added: 6g for cable ties
- Added: 175g for the glass beam dump to block the beam going towards B5_QD1
- Removed: 11g for two screws and their washers
After summing all the added and removed weights on the bench, since yesterday, we conclude that we have added a total of 329.5 g.
To compensate for the extra weight we have removed 332g of counterweights.
We added some temporary weights in order to bring the bench height around +500 um.
We then balanced the bench and were able to close both the angular and position loops (Fig.4).
We performed alignment checks with the bench suspended and controlled in air:
* the beam position on the B1p, B1s, B5 camera did not change at first order, compared to the reference taken last monday before the intervention: Fig. 5,6,7.
* we checked that we obtain the expected power on the B1s and B5 photodiodes and quadrants, compared to what we had before the intervention. The only doubt is on B5-PD2 where we have now more power than we used to.
* we were able to close the galvo loops of B1s and B5 as earlier (Fig. 8).
* we checked the alignment of the B1s beam on the EDB bench. The beam was still passing through the two irises installed last monday and reaching the OMC. We checked that, when opening widely the irises aperture, we have a power of about 2.1 mW reaching the photodiode EDB_B1s in reflection of the OMC, which corresponds roughly to our expectations (Fig.9).
Finally, we added a beam dump in EDB, right after the telescope placed before the OMC. We oriented this beam dump in such a way that its reflection reaches another beam dump.
At the end of the activity on SDB2, we performed the following actions:
* close the doors of SDB2 with only one screw, keeping the temporary weights inside, and keeping the clips holding the door rings.
* close the OMC shutter
* reopen the SDB2 position loops (in preparation of the SDB1 tower venting).
* Open SDB1 angular controls
* Open OB suspension controls
* Open OMC temperature stabilization loop
ITF found DOWN in COMMISSIONING mode. Still in SINGLE_BOUNCE_NI with PR misalignet (30urad ty).
planned activity:
- B1s QD path installation on SDB2 (Gouaty, Romero)
- 15:00 UTC - start the SDB1 tower venting (Vacuum team)
- intervention on SDB1 postponed to tomorrow morning.
SBE
07:30 UTC - SQB1 vertical position recovered via stepping motors.
The beam parameters obtained from fitting the measured data can be seen in the attached Figure. It must be noted that the sagital and tangential data points have been fitted independently.
This morning we resumed our activities on the SDB2 bench. We reopen the OMC shutter at 07h34 utc. We checked that the bench position (blocked) and the beam position on the B1p, B1s and B5 cameras did not change during the night.
We install one iris on the B1s beam path next to the SDB2-EDB viewport and another iris in front of the OMC to have alignment references.
We start the process of displacing SDB2_B5_M1 to its new position: (x, y) = ( -0.225, -0.331) m (using the optocad reference frame).
We realigned the B1s beam on the first iris by acting on B1s_M2 picomotor:
- B1s_M2_V: 2700
- B1s_M2_H: 13000
We also realign the B1s beam on the iris placed in front of the external OMC by acting on the last folding mirror before the EDB telescope.
We acted on the picomotors of B5_M1 in order to center the beam on B5_QD1.
- B5_M1_H: -3800
- B5_M1_V: -6000
To characterize the beam after the lens, we use the Smartek camera, its sensor is placed at an initial position (z=0) which corresponds to the bench coordinate X=-450+22.5-12 = -439.5mm along the beam axis between the galvo and the quadrant.
We take data points at:
- z=0 at 14h37 utc (integration time is set to 8000 us)
- z=25 at 14h42 utc
- z=50 at 14h46 utc
- z=75 at 14h51 utc
- z=100 at 14h52 utc
- z=125 at 14h55 utc
##### Error in measurement: height of beam on the lens was mistakenly changed
- z=275 at 15h13 utc (we change the integration time to 16000 us)
- z=300 at 15h16 utc
- z=325 at 15h19 utc
- z=350 at 15h22 utc
- z=375 at 15h24 utc
- z=400 at 15h26 utc
##### New measurements with corrected height of beam on the lens
- z=275 at 15h37 utc (we change the integration time to 16000 us)
- z=300 at 15h43 utc
- z=325 at 15h46 utc
- z=350 at 15h49 utc
- z=375 at 15h52 utc
- z=400 at 15h55 utc
- z=425 at 15h58 utc
- z=450 at 16h01 utc
- z=475 at 16h05 utc
The analysis of these data points gives the following parameters for the B1s beam going towards the quadrant:
* Sagital beam : w0s = 322.3 +/-2.3 um, z0s = -116.8 +/-2.3 mm, zRs = 306.7 mm
* Tangential beam : w0t = 256.7 +/-1 um, z0t = -68.9 +/-1.3 mm, zRt = 194.6 mm
This gives the following coordinates for the Gouy phase at 45 deg:
* For the sagital axis (vertical), X = -439.5 + z0S +zRS = -249.6mm
* For the tangential axis (horizontal), X = -439.5 + z0t +zRt = - 313.8 mm
Therefore the QPD sensor should be placed around X = -281.7 mm. This means that the QPD oblong hole should be around X = -258.2. Since this position is too close from the galvo, we displaced the galvo by -75 mm in Y in order to shorten the optical path. And we finally placed the QPD sensor at X=-350-23.5 = -373.5 mm, and Y = 450 mm.
We then aligned the beam on the QPD by acting on the B5_M1 picomotors with -3800 steps in H and +2800 steps in V. We then were able to close the galvo loops as shown on Fig.1. We notice that the corrections in vertical have large fluctuations. This is probably due to the limited distance between the galvo and the quadrant (only ~123 mm).
We added a beam dump in reflection of the QPD.
During this process we had to remove and add some components, namely:
- Removed: Beam dump and screws weighing 169g.
- Added: clamp weighing 20g
- Added: 5 cable ties weighing 6.5g
- Added: cable extension weighing 42g
- Added: clamp and screws weighing 23g
- Added: new lens (f = 125 mm) mounted on column and clamp weighing 267g
- Removed: clamp plus screws weighing 15 g.
- Removed: beam dump in reflection of B5_M1 with clamp and screws weighing 169 g.
- Removed: clamp plus screws weighing 16 g.
- Added: Beam dump and screws weighing 170g (in reflection of the B5_QD1 quadrant).
We stop here for the day. Tomorrow morning we will rebalance the bench and check the alignment with the bench suspended in air.
The beam parameters obtained from fitting the measured data can be seen in the attached Figure. It must be noted that the sagital and tangential data points have been fitted independently.
ITF found in COMMISSIONING Mode and DOWN state, with MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node (equal to SINGLE_BOUNCE_NI state from ITF_LOCK).
The activities of the shift were:
- from 6:00 UTC to 10:00 UTC Maintenance
- from 7:00 UTC B1s QD path installation on SDB2 (Gouaty, Romero); still in progress.
ITF left as it was found: COMMISSIONING Mode and DOWN state, with MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node.
After restoring the Injection loops yesterday, we notice that the system was not completely stable. The issue was initially identified through an alarm on the RMS value of the BsX_TX signal (Fig. 1). Further investigation showed that the excess noise originates from the EIB bench actuators (Fig. 2). All actuators show increased noise starting from the EIB rebalancing performed yesterday morning. Around 17:30h LT, we went into the Laser Lab to do a visual inspection on the bench, but we coudn't identify anything suspect (nothing touching or blocking the bench somehow). We slightly tightened the screw on the plexiglass panel that had been opened to move some weights on the bench yesterday. This appeared to reduce the excess noise somewhat, but the noise is still present this morning (see FFT on Fig. 3 of the broadband noise before and after).
Investigations are ongoing.
Entry of August 17, 2026 remained in draft by mistake.
ITF found in TROUBLESHOOTING Mode and DOWN State.
All times are UTC.
07:20 - 08:14 INJ: EIB restore (Melo, Lagabbe, #69586, #69587).
08:06 - 08:56 VAC: Activity on minilinks near to BS tower (Macchia, Francescon).
08:38 ISC: Etalon loops turned off (operator).
11:35 DET: Start of SDB2 intervention preparation (see attached document):
- ITF_LOCK node in DOWN state, and PAUSE operation;
- INJ_MAIN node in AUTO mode, requesting IMC_RESTORED state;
- ARMS_LOCK node in AUTO mode, requesting DOWN state;
- DRMI_LOCK node in AUTO mode, requesting MISALIGNED_PR_SR state;
- DET_MAIN node SHUTTER_CLOSED state, and PAUSE operation;
- SDB2 LC Angular Loops Open and SBE Position Loops Open;
- SDB1 Drift Control on B5 enabled (SDB1_LC.LC_B5_QD2_enbl = 1);
- SDB2 venting started (#69584);
- DET HVAC set to full speed (Portata Nominale);
13:10 VAC: NI/WI Large Valves closed (#69584).
13:35 DAQ: Virgo Process Monitoring update to version v10p4r2 (Pacaud, #69588).
14:46: Set MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node.
14:28: Added -20 urad PR TY to avoid ghost beams.
14:54 DET: Offsets for SDB1_Quadrants removed (as done performing OMC Lock/Scan during periodic maintenance).
15:00 DET: Begin of SDB2 activity (Gouaty, Romero).
ITF left in COMMISSIONING Mode and DOWN state, with MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node (equal to SINGLE_BOUNCE_NI state from ITF_LOCK).
The activity in DET LAB is still ongoing.
