Figure 1. The effect of the ring heater was clearly visible in the arm power, with a decrease in arm power. There was no associated peak in the B1p power. However, superposed to it there is a trend of increase in the B1p power that started before the PR RH was turned on, and continued afterwards. Also the difference in power has not returned to its starting state.

Figure 2. A likely explanation is that the etalon loop has been changed yesterday, which resulted in a transient during the night spanning 0.07 degrees (1/3 of an etalon fringe?). We have seen the etalon loop affect the arm cavity power, especially increase the difference between B7 and B8. So the steady state difference in arm powers after the PR RH transient is likely due the etalon, although there is also the tail of the PR RH cooling, this will complicate a quantitative analysis of this data.

Figure 3 The B1p and B1s power also increased during the night, on a slow time scale, likely due to the etalon. The order 3 mode has increased by a factor 4, and we have seen last week that the etalon can do that for a half a fringe variation.

This morning I have reenabled the EDB B1t photodiode by hand, it must have turned off during the unlock around 6:00 UTC.

ITF found locked at LN2 in COMMISSIONING mode and DAS power tuning activity in progress.
At 14:50 UTC Gherardini and Tringali switched ON the PR RH power supply.

The TCS activity went on without major issues till 20:00 UTC. ITF still locked at LN3.

Following Michal’s indication, at 19:18 UTC, in order to make the effect induced by the ring heater more evident, we increased the power to 3 W (V = 10.6 V).

The PRM ring heater was then switched off at 21:14 UTC.

In order to evaluate the impact of DAS tuning, performed yesterday, on the mystery noise Vs B1p_DC, I tried to find two gps relatively close in time, corresponding to different TCS working point, having a clear difference in terms of B1p_DC, but the same value of DCP and other parameters relevant for the sensitivity.

My best choice has been:

1453039518 - 14:05 UTC - blue data

1453058818 - 19:26 UTC - red data

At lower B1p corresponds lower noise. The difference in terms of floor is confined in a relatively narrow band (80 - 130 Hz); other differences seem more related to structures going up an down. The variation of floor is compatible to a rescaling of the mystery component by about 10 - 15 %.

Doing this analysis with more data and statistics is a bit difficult because a similar variation of noise occurs when the DCP chenges by a relatively small amount, like 20 Hz, which is the normal amplitude of fluctuation even when the alignment stability is relatively good.

In preparation for the input mode-matching measurement, Michal asked us to switch on the PR ring heater at the end of the DAS tuning activity.

To do this, Fabio, Maria, and Aaron went onto the platform in the CB to switch on the PR-NI ring heater power supply.

After completing the DAS outer rings power tuning, with the ITF in LN2, the PR ring heater was switched on at 1 W (V = 6.1 V) at 16:56 UTC.

Today, we continued the investigation of the DAS working point power started yesterday (68543). Between last night and this morning, the ITF unlocked and relocked twice without issues. Therefore, the lock acquisition seems to work properly with the DAS working point left for the night.

With the ITF in LN2 (and BS control in full bandwidth) we performed three different steps:

STEP 10 | 08.33 UTC:  increase of the NI DAS outer ring by +10%. (pickoff from 0.636 W to 0.691 W)

STEP 11 | 09.42 UTC: decrease of the WI  DAS outer ring by -10%. (pickoff from 0.273 W to 0.247 W) 

STEP 12 |11.05 UTC:  increase of the NI  DAS outer ring by +10%. (pickoff from 0.691 W to 0.753 W) 

For each step, it was quite difficult to assess whether it was beneficial or not (see Fig.1).  The most significant effect was a loss of sideband gain, so after discussing with Michal and Madda, we decided to revert all steps in order to recover the pre-shift condition. All steps were reverted at 13:08 UTC.

STEP 13 | 13.08 UTC:   WI DAS OUT +10% and NI DAS OUT - 20% (restore the starting configuration) 
At 13:27 UTC, the ITF unlocked due to an earthquake . We exploited the unlock to check the DAS powers by closing the flip mirrors one at a time  (completed at 13.48 UTC).
The ITF relocked in LN2 at 14.20 UTC.

During the transient of STEP 10, we observed an initial improvement in the BNS range and on both B1p and B1s, therefore, we performed an additional step:

STEP 14 | 15.05 UTC UTC:   NI DAS OUT +5%.
All steps performed today are schematically represented in Fig.2. 

The DAS outer rings power tuning can be considered completed. 

Hence, the reference powers from now on are as reported in the table.

The work on TCS (DAS tuning) went on in the morning with the ITF locked in LOW_NOISE_2.
13:27 UTC unlock due to an earthquake in Kamchatka (magnitude 6.3)
14:19 UTC relock to LN2

Sub-systems reports

Air Conditioning

• TB heater stopped, backup switched on, spare part shipped today, it will arrive between tomorrow and Saturday (#68546, Pezzimenti, Soldani)
• WE heater malfunction, fixed (Soldani)
• FCIB chillers 1 and 2 malfunction, fixed (Andreazzoli)

Yesterday night (Jan 21), the magnetic line injections were performed via the ENV METRATON node in NEB and WEB.
Regarding the CEB magnetic lines injection, this morning I found that it was still ongoing. In principle, it should have been completed during the night, but there was an interferometer unlock (during NEB injection). I stopped the CEB lines injection this morning since the interferometer had been unlocked to allow the start of the scheduled shift activities.

The output files are /virgoData/NoiseInjections/MagneticInjectionsO4/output:

• MagneticLine_NOISE_MAG_CEB-1453096947.txt
• MagneticLine_NOISE_MAG_NEB-1453060711.txt
• MagneticLine_NOISE_MAG_NEB-1453073344.txt
• MagneticLine_NOISE_MAG_WEB-1453085146.txt

The following report has been submitted to the On-call interface.

On-call events -> Air Conditioning

Title: Caldaia GPL TB in blocco

Author(s): Pezzimenti

Details:

Ricevuto allarme sms da dms per caldaia gpl tb in blocco. In contatto telefonico con Soldani, avviato caldaia caldaia di backup a gasolio.

* Note that any files attached to this report are available in the On-call interface.

Tonight I found the automation stuck in LOCKING_DC_READOUT, because the new command to enable EDB_B1t was not working:

2026-01-21T22:52:40.581Z ITF_LOCK [LOCKING_DC_READOUT.run] USERMSG 0: EZCA CONNECTION ERROR: Any Other Error: Could not get value from channel: SDB_B1t_PD1_VBias

Looking at the error, META_library and the new configuration, one hypothesis is that the function that enables Vbias extracts the name of the bench from the first segment of the process name, but in this very specific case the name of the process and the name of the bench do not share the same segment (SDB and EDB respectvely), so the standard function cannot work and something specific needs to be devised.

I commented the engagement of EDB_B1t and the lock acquisition could proceed. To be debugged tomorrow.

Another long standing bug is that the autorelock selected LOW_NOISE_2 instead of LOW_NOISE_3_ALIGNED as target state. This used to happen with LOW_NOISE_1 and LOW_NOISE_3 as target, but the recent increase of states made the bug scale up the wrong request as well.

The configuration for EDB_B1t has been added to META_library, and the engagement of the PD has been added just before reaching LOCKED_DC_READOUT. To be tested at the next acquisition.

As agreed, we started today’s DAS tuning in LN2 (8:17 UTC).

The actions performed on TCS DAS outer rings are summarised in the table below.

SUMMARY TABLE

The STEP 1 (WI OUTer ring +10%) seemed to cause a slight increase of the SBs and a deterioration of B1p, B1s and CMRF. 

Due to this, we decided to try to act on the other arm, but the STEP 2 (NI OUTer ring +10%) led to SBs getting lower, while B1p and B1s don’t seem to be changed. Furthermore, we noticed that BNS range worse starting from STEP 1.

We agreed to revert STEP 1, to see the effect of only STEP 2, doing STEP 3 (WI DAS OUTer ring -10%). As a result, SBs continued to go down, while other figures of merit  (B1p, B1s, BNS range) came back to this morning's values. 

Since the SBs decrease seemed to be correlated with STEP 2, we tried to revert the action on N arm with STEP 4 (NI Outer ring -20%). B1p and B1s remain untouched, while SBs and BNS range get better and then worse. 

Before making any other change, we agreed to try an unlock and repeat lock acquisition.

12.03 UTC ITF unlocked.

12.42 UTC ITF locked in LN2.

Since we would like to understand if some other trend was going on in the meanwhile, we made STEP 5 (NI OUTer ring +10%) to restore the thermal actuation condition of this morning. 

After around 1h and half we noticed that all the figures of merit almost reset the values to the one of this morning, except for SBs: after some investigations, Maddalena noticed that it could be related to Etalon loops (see Figure 1: behaviour of SBs level VS WI/NI temperatures from monday, as reference; the SBs level minima are reached, at different moments, between 10 and 14 UTC in the past days).

With STEP 6 (WI OUTer ring -10%) we start to explore the last direction left with the WI DAS. The effect was quite evident on SBs and also on B1p and B1s, all getting better.

Since B1p and B1s get slightly better but SBs lower dramatically, and the BNS range as well, we agreed to perform another step, the STEP 7 (NI OUTer ring -10%), to recover the SBs keeping the lower achieved values of B1p and B1s. 

STEP 8 (NI DAS OUTer ring +10%) and STEP 9 (NI DAS OUTer ring +10%) were performed because the previous direction does not seem to be the right one. After these two steps, BNS range recovered, SBs improved and other figures of merit remained pretty stable.

Michal noticed that the MICH control loop was not working properly and corrected it manually just before letting the ITF go in LN3_ALIGNED (locked in this state at 19.50 UTC), in order to start the ENV low-noise injections.

In Figure 2 the general behaviour of the main signal during all the steps performed and Figure 3 a zoom of the last hours are shown.

The thermal configuration left for the night is reported in the table below.

Today I changed, for LOW_NOISE_3_ALIGNED, the amplitude of the arms dithering lines and the darm LF line (74.4 Hz) at the same level as in LOW_NOISE_2. The OS/DCP calibrations and OS gain have been changed accordingly. To be tested later once we move forward from LOW_NOISE_2.

The PD flag in the DMS had been updated to include a check on the EDB B1t photodiode Vbias. The flag should turn red whenever the Vbias of this photodiode is not engaged after DC readout.

The DetMoni process was restarted at 16h45 utc.

ITF found locked in LN3_ALIGNED, with SIB2 horizontal loop still open.
According with M. Was I unlocked ITF and relocked at LN2 in order to be ready for the planned activity on DAS WI power tuning. Taking advantage of the unlock I closed SIB2 loop via VPM.
COMMISSIONING mode set. After setting BS fullbandwith (Casanueva), TCS activity started at 08:17 UTC with a 10% on WI DAS. Activity in progress...

The reduction of noise from the dither lines improved as expected the accuracy of many in-loop and out-of-loop alignment signals (fig 1, 2 , 3). The impact on SR signals is smaller than the others, likely because the noise of its own AA signal is larger. Looking at DCP (fig 4, 5), no interesting change is visible. Maybe there is a certain reduction of oscillation in the time scale of 200 s, but there are still slower fluctuations as large as before.

Some correlation between DCP and SR TY local signal is stil present along the data of the night, but less evident than in the data shown previously. We have also to notice that the span of SR TY has been +- 0.2 urad, instead of +- 0.4 urad of the previous data.

In order to check if the high gain of SDB1 drift control is a problem at 05:12 UTC I have reduced the gain by a factor 8 in TX and TY, putting it back to the value used in LN2.

Figure 1. The change has slightly reduce the motion of the SDB1 bench with regard to the ground as measured by the local controls, with less short larger deviations of +/-2 urad compared to the mean value, but otherwise it had no visible effect. 

Figure 1. Looking at the HOM from this night the level is fairly low when comparing to the etalon fringes from a few days ago. The order 3 mode is still relatively high, and looking at the etalon fringes it is for example comparable to Jan 15 at 11:30 UTC, while a lower power was achieved at 10:30 UTC on Jan 15. So reducing the etalon by the temperature change that occurred in 1h on Jan 15 could help, about 0.05 degree Celcius lower temperature, It was also corresponding to higher BNS range, although the maximum was even further away at ~9:00 UTC on Jan 15. 0.05 degree lower temperature that last night actually correspond to the set point of the loop, as the temperature of the RH was about 0.05 degree higher than the set point for both NI and WI, so it should converge to the slightly better working point by itself.

/users/mwas/OMC/EDB_OMC_fast_scan_20260120/EDB_OMC_slow_scan.m

Onother difference between LN2 and LN3 that can be reverted is the amplitude of the dither line used for arm alignment. If the alignment of SR cavity is a combination of SR and arm rotations, having more or less noise in the arm angular controls could make some difference. I did the change at 6:20 UTC.

In order to do the same test in a faster way, I used for half an hour the local control and I explored some different SR TY position. The data will be analysed better tomorrow, but the first feeling is that this is not a way to increase the DCP. 

The activities of the shift were the following: DAS movement part 2 and explore the setpoint on the alignment of SR TY. 

All the activities concluded at 21:30 UTC; ITF left in LN3_aligned with autorelock enabled.

SBE

SIB2 opened many times due to the strong wind; it was left opened for the night.

We explored in LN3_ALIGNED a setpoint on the alignment of SR TY, both negative and positive direction. In order to have a better trend of the response of the DCP and other figures of merit, at the end of the shift (21.14 UTC) we put slow ramp of 2hrs with a final setpoint of +0.01.

We left the ITF with the ramp ongoing and for the night in LN3_ALIGNED.

We will monitor the data.

Today’s plan was to perform the test proposed by Michal in the entry 68494 to investigate the effect of the DAS horizontal motion on both the B1p and B1s cameras.
ITF locked in LN2 at 13.25 UTC.

STEP 6:  at  13.36 UTC we moved WI DAS by 0.5 cm (2778 steps) in the forward direction. 
In order to reduce signal fluctuations due to the bad weather, at 14:28 UTC Manuel put the BS control into full bandwidth.

STEP 7:  at 14:54 UTC, the WI DAS was moved by an additional 0.5 cm (2778 steps) in the forward direction.
ITF unlocked at 15.19 UTC.

Since the ITF was unable to relock, at 16:40 UTC, with the ITF down, I reverted steps 6 and 7 to recover the pre-shift configuration (STEP 4 described in the entry 68479).
All the steps performed during the January 14 shift (68479) and today are shown in Fig. 1. The main ITF signals during the shift are shown in figure 2.
Figure 3 shows the B1p and B1s images at the steady state of each step, compared with the reference images acquired before starting the movements.
In both the “Nominal Position before installing the SR diaphragm” and step 7, the bright spot appears on the same side of the B1s camera, i.e. the right side (Fig. 4).

The EDB OMC scans have continued throughout the weekend, up to Jan 18 20:20 UTC, when the interferometer unlock turned off the Vbias of the photodiode in transmission (EDB B1t). An action would be to add in the automation renabling the voltage bias of that photodiode after each lock acquisition. For most unlocks this is not needed, as the OMC scans so most of the time it is far from the resonance during the unlock, but on occasion it will be on resonance which will turn off its voltage bias and close the shutter. 

Figure 1 shows the peak height of the different HOM over 50 hours, with two scans that where too far from normal resulting in drops in measured HOM power, on Jan 16 around 12:00 and Jan 18 around 13;00.

Figure 2 shows the integrated HOM power over 50 hours, as before there is a large change in HOM power due to the etalon especially for modes 2, 3, and 4. And the etalon has settled in a set point with high HOM power, also visible on B1s. This has been adjusted since the weekend on Monday by a change of etalon set point. This long trend give us an idea on the stability of the measurement, the fluctuations over the time scale of a few hours are of the order of +/-20% of power, with more variability for the order 9 mode.

/users/mwas/OMC/EDB_OMC_fast_scan_20260116/EDB_OMC_slow_scan.m