This entry is posted with a delay because the logbook was temporarily unavailable.

Today, we started the activity on the WI CO2 bench at approximately 12:30 UTC (a reference entry was posted earlier, but it does not appear in the logbook), continuing to following the steps described in issue #186, performing the outer ring checks:

• We removed the mask from its nominal position and installed SPIRICON 2 in its place, using the post holder

• We reduced the power in the DAS OUT branch to limit the power reaching the SPIRICON 2

• We checked the intensity distribution of the outer ring

• We observed mainly a horizontal asymmetry, together with a very small vertical one. We therefore adjusted M10 to obtain a more uniform intensity distribution. Figure 1 shows the outer ring profiles before and after the adjustment. 

After completing the adjustment, and before reinstalling the mask, we acquired an image of both WI DAS rings (Figure 2) with SPIRICON 2. The two rings appeared correctly aligned. 

We then:

• Removed the SPIRICON 2 from mask position and we put back the mask 

• Performed a quick check with SPIRICON 1 at the CINOGY position to verify that the mask correctly covered the hot spot. 

Having completed the power distribution checks, we removed both SPIRICON cameras from the bench and proceeded with the on-bench alignment checks.

At this point, we looked at the actuators through the Thermal Camera data acquisition system, to relatively align all the WI CO2 actuators (DAS rings and CH) one to each other. Figure 3 shows the final DAS OUT-CH alignment. 

After completing the checks, all flip mirrors were restored to their standard positions: the DAS IN, DAS OUT, and CH flip mirrors were closed to block the beams on the bench, while the CINOGY and Thermal Camera flip mirrors were left open to allow the beam to propagate towards the interferometer if required. The WI bench enclosure was then closed.

The activity on the WI bench ended at approximately 15:10 UTC. The WI CO2 bench was secured and the white curtains were closed (69644).

The power-distribution and alignment checks on the WI CO2 bench can therefore be considered complete.


We then moved to the NI CO2 bench to begin the same checks previously performed on the WI bench. The activity started at approximately 15:15 UTC, following the procedure described in issue #186, beginning with the inner ring checks: 

• We installed SPIRICON 1 in the CINOGY position

• We reduced the power in the DAS IN branch to limit the power reaching the SPIRICON 1 and followed the beam along the CINOGY telescope path.

• We checked the intensity distribution of the inner ring.

• We observed mainly a horizontal asymmetry, together with a very small vertical one. We therefore adjusted L3_tras to obtain a more uniform intensity distribution. Figure 4 shows the inner ring profiles before and after the adjustment. 

At approximately 16:30 UTC, we stopped the activity and secured the NI bench. The CO2 laser beams were blocked on the bench using the flip mirrors. SPIRICON 1 was switched off, covered, and left in position, and the bench enclosure was closed.

The activity will continue tomorrow with the outer ring power-distribution checks and the on-bench alignment checks.

Activities on the WI CO2 bench have finished. The enclosure and the white curtains were closed at approximately 15:10 UTC.

Activities continued on the NI CO2 bench until 16.30 UTC.

Following the addition of the RFC Audio channels to rtpc19 ( https://logbook.virgo-gw.eu/virgo/?r=69642 ), I have replaced them as an error signal for the PSTAB 50Hz harmonics feedforward. After some tuning this has worked well at least as measured with the existing diagnostic channels.

Figure 1 shows the performance around the 50Hz line, in purple are reference data with the FF off and in blue with the FF on. The line is removed from RFC PD1 Audio which is in loop, and also RFC PD2 Audio which is out of loop. The two PDs are connected to the same photodiode mezzanine, so one could argue that they just see a common sensing noise and not the power stability itself. The line disappears also from the B2 photodiode, where it is much more faintly visible than in July, because the power on the PD is 10 times smaller, the PR parking position must be slightly different. Most importantly it is reduced also from the RFC Tra photodiode, which is read out of vacuum by separate electronics, confirming a true improvement in the 50Hz, while not being able to quantify the improvement as it is affected by its own 50Hz contamination. On the PSTAB PDs there is no significant difference, as those are contaminated by additional sensing noise at 50Hz, both in loop, and most likely in the readout to the ADC. 

Figure 2 shows the performance for the 250Hz line. Again it is well removed from both RFC PDs, and the improvement on the RFC Tra photodiode is much clearer with a factor 10 decrease, while B2 does not have enough signal to give any information.

Leaving the FF off. The next step should be to automate switching of the FF loop when the RFC unlocks, as it may misbehave without the RFC locked, and then perform some longer duration tests of the FF and FF tracking loop stability.

-----------------------------------------------------

around 12:38 - restarting ISYSnoise process to add RFC as possible
inputs to PSTAB 50Hz harmonics cancellation
12:40 UTC (4min) reference time

spent a long time adjusting the starting parameters and the FF
tracking parameters. Especially for the 250Hz where a delay of 90
degrees was needed to make the I quadrature act on the gain, and the Q
quadrature on the phase.

14:09 UTC (4min) FF on with tracking enabled and in steady state

14:15:20 UTC disabling FF and FF tracking
 

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)

Activities communicated in control room:

• RFC_PD{1,2}_Audio sent from SIB2_rtpc(rtpc18) to INJ_rtpc(rtpc19);
• from 6:00 UTC to 10:30 UTC standard planned maintenance; 
• from 12:30 UT
• work on WI CO2 benches, still in progress

ITF left as it was found.

The SIB2_Photodiodes server configuration has been updated to send the  RFC_PD{1,2}_Audio channels to the INJ_rtpc

The ISYSnoise server configuration has been update to read the SIB2_RFC_PD{1,2}_Audio channels

Operations performed between 2026-08-25-07h18m43-UTC and 2026-08-25-07h23m38-UTC

After the completion of the SDB1 tower evacuation, the VAC team opened the BS-SR and DET cryotrap valves to send the NI single bounce beam towards SDB1. Meanwhile Paolo restored the reference position of the SDB1 bench in vacuum and closed the position loops. Henk-Jan restored the nominal height of SDB2 and could then close the position loops.

We adjust the SDB1 angular setpoints in order to center the beam on the B1p camera (Fig.1): This was achieved by setting TX = 70 and TY = 80 urad

Noticing that the TX correction is around -4V, we acted on the BENCH_TX motorized counter-weight with -16000 steps in order to reduce this correction around -0.4V. Adding this to the steps performed last week, the motorized counter-weight is now off-centered in TX by -50000 steps.

We adjust the OMC Peltier gain (from 20 to 50) in order to be able to control the OMC temperature in vacuum. OMC temperature stabilization loop closed at 13h46 utc.

We close B5 beam drift control at 13h50 utc. The position of the B5 and B1p beam on their cameras with the B5 drift control closed are shown on Fig.2 and Fig.3

Open OMC shutter at 13h56 utc. We check that in these conditions, the B1s beam is almost perfectly centered on the camera (Fig.4). The powers obtained on the photodiodes are shown in Fig.5. In particular we have 78 mW on B1p and 93 mW on B1s.

We start an OMC lock acquisition at 14h18 utc starting from 22.45 deg. We observe a mode of order 5. Therefore we stop the scan and adjust manually the OMC temperature to 22.54 deg. Start another scan for OMC lock acquisition at 14h23m50. The OMC is properly locked around 14h30 utc (Fig.6) with about 12.8 uW on B1_PD3.

We improved the alignment of the OMC in TX and achieve about 14.8 uW on B1_PD3 (Fig. 7).

Start OMC scan at 14h57 utc

Order 1: 1.1 uW > 7% of misalignment defect

Order 2: 0.2 uW > 1.4% of mode mismatch

We update the picomotors names as follows:

* Old "B5_M2_H" / "B5_M2_V" becomes now : "B5_M1_H" / "B5_M1_V"

* Old "B5_M1_H" / "B5_M1_V", becomes now: "B1s_M3_H" / "B1s_M3_V"

We then try to close the SDB2 galvo loops. All loops were closed at first attempt except the galvo of B5_QD2 (the new B1s QPD). In order to recenter the beam on the quadrant we acted on the mirror B1s_M3 with the following steps:

B1s_M3_H -1200 steps

B1s_M3_V +1200 steps

Then the B5_QD2 galvo loops was closed successfully.

We also acted on B1p_M1 and B1p_M2 to reduce a bit the vertical corrections (B1p M2 V +400, B1p_M1_V +300)

Fig. 8 shows all galvo loops closed with small level of corrections.

We open all galvo loops at 15h34 utc.

Scan SDB2 bench in TY (Fig.9): We can see that for the nominal setpoint of the bench TY = 880 urad the B1p photodiodes are well centered and during the scan the beam is always inside B1s. For B5, TY=880 corresponds to a maximum, but it is very close to the edge of the power plateau. This behaviour is probably due to the fact that the photodiode is seeing a second beam in addition to the main beam (as on B5 camera) when the main beam is close to being clipped. We decided to adjust the centering of the B5_PD2 photodiode (acting on B5_M3 and B5_M4 picomotors) in order to better center the main beam for TY=880 urad. While repeating the TY scan of the bench, we obtain Fig.10. We intentionally kept the B5p photodiodel on a maximum for TY=880, but it is not clear if that is the best tuning. We leave it as it is for now.

Fig.11 shows a small scan in TX which does not have any impact on the photodiodes power.

We conclude here the alignement checks.

Close OMC shutter at 16h55 utc.

At the end of the shift we restore the SDB1 floating setpoints. Then we open the B5 beam drift control and restore the B5 QD offsets used in dark fringe.

We started the activity at approximately 13:50 UTC (69638), following the steps described in issue #186 for the inner ring checks:

• Installed SPIRICON 1 at the CINOGY position, using the available bench marker.

• Verified that the power in the DAS IN branch was already set to its minimum, as required to follow the beam along the CINOGY telescope path.

• Checked the intensity distribution of the inner ring.

• A vertical asymmetry and a smaller horizontal asymmetry were observed. We therefore adjusted L3_tras to recover a more uniform intensity distribution. Figure 1 shows the inner-ring profiles before and after the adjustment.

The activity ended at approximately 16:15 UTC. The WI CO2 bench was secured, and the white curtains were closed (69639).

The checks will continue tomorrow, after the maintenance work has been completed, with the outer ring measurements.

Activities on the WI CO2 bench have finished for today. The enclosure and the white curtains were closed at approximately 16:15 UTC.

Activities will resume tomorrow after the maintenance work has been completed.

6:00 UTC DET lab air flow set back to REDUCED ("Portata Ridotta") (operator)

8:30 UTC INJ alignment (Gosselin, Lagabbe)

9:00 UTC Unblocking of SQZ beams towards SQB1 (Sorrentino)

12:00 UTC BS-SR valve opening (Vacuum Team)

13:00 UTC SDB1 position loops closed, SDB2 and SPRB vertical position adjusted (Bulten, Ruggi, operator)

13:30 UTC TCS WI bench assessment (Lumaca, Corubolo)

Around 13.50 UTC, we are starting the check activities on the WI CO2 bench.

This morning around 9:20 UTC I removed the beam dumps from EQB1.

This afternoon, we went back to the detection tower to check the position of the motorized counter weight (on which we performed -34000 steps yesterday evening). We observed that the translation stage is about 0.5 mm from its zero position, which we considered reasonable.

Fig.1 shows the values of the angular corrections applied on the marionetta.

We then gave green light to the VAC team for the closing and evacuation of the SDB1 tower. We opened the angular control and the OMC temperature stabilization loop.

While checking with the operator the status of the position loops we realized that we had forgotten to close them in the morning. On Fig.2 we check the evolution of the SDB1 bench position between yesterday morning when we took the alignment reference (around 10h00-11h00 utc) and the position of today. We can see that they are very similar despite the fact that the loops were not closed today.

Since we could not replug the B5_M1_TX picomotor on SDB1, we have unpluged the cable from the picomotor driver 8742 SN 10592, channel 4. The cable is left free, we have attached a sticker on it with the label "B5_M1_TX".

The beam dump that was placed on the reference beam path of the B1p PC on August 13th has now been removed. The beam dump is stored inside the rack of the DET lab.

ITF found in SINGLE_BOUNCE_NI (with PR misaligned about 30 urad in ty), in COMMISSIONING mode.

planned activty:
- SDB1 intervention (Gouaty, Romero). Activity concluded at 14:30 UTC.
- 11:30 UTC Melo in Laser Lab to block the beam in order to allow Bulten to work on the eccess of noise on EIB.

SBE
11:30 UTC - SIB2_SBE loop opened for unknown reason. Properly closed via VPM. Unfortunately the loop opened again after 10 min. I contacted Bulten who fixed it at 12:15 UTC.

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.