At the end of the day's activities, I made two changes to the lock acquisition, to be tested during the last part of the shift:

• I reinstated the BS_TX angular loop in full bandwidth in LOW_NOISE_2 (instead of LN3); this is a recurring thing, but lately we managed to close the loop manually soon enough in LN2, so it is worth checking if it can be automated (again); for reference/rollback, I uncommented line 5966 and commented lines 6505 -> 6507 of ITF_LOCK.py;
• I increased both gains (standard filter and boost filter) of the SSFS loop in CARM_NULL_1F: the loop UGF was quite low yesterday when I checked, and I tried the boost gain of 800 to improve it (apparently, it has been tested already many times). So I set this value in the ITF_LOCK.ini file, and changed of the same amount the gain of the initial loop; the old values are left, commented, just above the new ones (lines 227 -> 230 of ITF_LOCK.ini).

The issue could be related to the fact that one of the relays of the NE actuator (REL21) was not correctly set to the LowNoise2 mode in the second lock. If the GUI shows the relays in the standard ordering, this should mean that the DR coil was affected, and this confirms the checks done offline on the Hrec reconstruction and the NE TF monitoring in particular.

After the maintenance we set the ITF in LN2 and allowed about 10 minutes for the state to stabilize, before proceeding with the exploration of the stability range of SRCL_SET.

We closed BS_TX in full bandwidth and opened the SRCL_SET servo, then started changing SRCL_SET in steps of 10, one minute per ramp, allowing 20 minutes for each new state to stabilize and gather data. We managed to make a three points scan:

the ITF unlocked a few minutes after the last change of SRCL_SET (Fig.1).

We relocked the interferometer and decided to explore the margin of the scan more granularly. After reaching LN2 we set BS_TX in fbw and disabled the SRCL_SET servo again, then we set SRCL_SET to -20 with a two minutes ramp, allowed about 15 minutes to stabilize. We started changing the SRCL_SET in steps of 2, with one minutes long ramps, but realized after the first step that very little changes with such a small step while the duration of the test becomes considerable. For the next steps, we changed SRCL_SET in by 4, with two minutes long ramps.

The ITF unlocked about 10 minutes after step 4 (Fig.2)

The sensitivity was unexpectdly high for LN2, but the correct reconstruction of Hrec needs to be checked.

ITF found unlocked with WEST cavity misaligned; many red flags for ISYS.

I was able lo realign the WEST cavity but once locked it apperead a strong oscillation in the powers of the arms.

At 7:00 UTC started the planned Maintenance, below the listof the activities communicated in control room:

• check of TCS thermo camera reference (operator);
• check of TCS powers (Diana from remote);
• check on the ISYS, see: 68699;
• TCS chiller refill (Marco and Nicola);
• Remove microphones at NE, reconnect NNC arrays at NEB/WEB, measurements in CEB (Tringali, Fiori, Quemener);
• cleaning of the experimental areas;

At around 11:00 UTC I started to relock; after a manual prealignment of SR and PR the ITF reached LN3 at 12:16 UTC.

At 12:47 UTC it was manually unlocked to relock in LN2 as requested by the commissioning activity; activity still in progress at the end of the shift.

SUSP

At 7:30 UTC while testing the new Alignment interface I opened the SR LC loops; see SR LC tz saturating for wrong setpoint.

DET

The periodic task of OMC lock and scan in single bounce was skipped because of the problem of the SR LC that was fixed around 11:00 UTC.

Today, during normal alingment procedure with the new alignment interface, the local controls of the SR payload opened. When recovering the control loops, TZ was not closing properly as the LC was saturating all the time. This happened since the loop was trying to bring the tz to a wrong setpoint far away from the current mar TZ position. The change of setpoint in SAT_MAR_TZ_SET (and also in tx and ty) occurred during the use of the new UI (around 7.30 UTC, fig.1).

Somehow the correct values of the LC SETs have been overwritten with older values.

Correct numbers have been put and saved in the DSP card.

SR LC loops closed.

Yesterday evening, for an unkown reason, the current of the pumping diodes suddently decreased (figure 1). 
This morning we went in EER, we had 27.8 A for diode 1 and 27.6 for diode 2. We brought the current back to 29 A and got the system as it was on saturday (figure 2). 
We waited for everything to thermalized and we went to realign the PMC, shift and tilt (figure 3) 

This morning, at 09h43m33 UTC, I made a small adjustment (~0.1 uW) of the B1_PD3 offset (see attached figure).

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

On-call events -> Interferometer Sensing & Control

Title: SSFS unlocks

Author(s): boldrini

Details:

I was called because of a series of similar unlocks. I identified two of them, both similar in nature, caused by an unlock of the SSFS quickly followed by the rest of the interferometer.

I recommended to leave the ITF in auto-relock and we'll take a look at the issue tomorrow.

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

At the beginning of the shift I found the ITF in COMMISSIONING, relocking
14:46 UTC ITF in CARM_NULL_1F. We waited to check the stability of the ITF that at 15:49 UTC achieved LN3_ALIGNED. Due to the weather's instability, planned activities were postponed.
17:48 UTC unlock
18:24 UTC ITF in LN3_ALIGNED
21:15 UTC on: unlock (maybe SSFS), it unlocked again at ACQUIRE LN1 and then INJ unlocked. DET_MAIN stuck, INIT not working, I set it to DOWN and then to SHUTTER_CLOSED, which worked. INJ unlocked a second time.
22:00 UTC end of the shift: at 21:45 UTC I had to contact the ISC on-call expert (Boldrini) due to these multiple unlocks. ITF left relocking with on-call assessing the problem.

After the recovery of the ITF following the installation of the SR baffle, the interferometer unlocked several times, some of them were clearly indicating the PSL/INJ as source of unlock. 

One of the main concern about is the temperature change of the main laser, as in the past the ML temperature setting has been associated to glitches and instability of the laser.

During the night between 12th and 13th there were two unlocks similar to fig. 1. Here, there is an clear instability in the EOM corrections as well as in all the frequency and power error signals. Not clear who is the culprit. 

Instead, the 14th just before the problem of the slave laser, the behavior was different (fig. 2), and it seems that the PMC/PSTAB loop react before everything else. 

On the 12th evening, another unlock seemed to be related to the INJ system (fig. 3 and 4), however no PSL/INJ seem to see anything, except for the MC mirror Z that starts to drift away. No clear reason has been found yet. 

On Saturday evening, the slave laser switched off while. The system was in standby for the weekend ; this morning we went to EER to investigate the issue.

The safety chain had been triggered due to a faulty temperature controller, namely the controller of diode 1.

We installed a spare controller. As usual, the programming procedure is not straightforward; additional information for possible future interventions is provided at the end of this entry.

We were eventually able to restart the slave laser. We gradually increased the current of the pumping diodes and returned to a relatively normal operating condition. The output power of the Neovan is slightly lower than usual, and the mismatch in the PMC is slightly worse (Normalized reflected power 5% higher). We will perform fine tuning tomorrow.

In addition to the information already provided in entries 66004 and 62780, we add the following details:

• The communication addresses are:

  • diode 1: 27

  • diode 2: 1

  • xtal 1: 2

  • xtal 2: 3

• To access the third menu (PID parameter settings), one must press the right buttons simultaneously, then when “Ulock” appears one should use either 0, 1, or 10 (the value depends on user access rights).

• At present, the controllers appear to be configured with the following Ulock values (tbc)

  • diode 1: 1

  • diode 2: 0

  • xtal 1: 10

  • xtal 2: 10

As observed previously, the safety chain reset did not initially work because the start button on EER1/C3 also needed to be pressed. It is unclear whether this action was possible from the beginning or only after off/on of the 6 V power supply (the unit with the red switch).

ITF found DOWN in TROUBLESHOOTING mode.
The ISYS system found DOWN with Slave Laser off and DET_MAIN Metatron node stuck in UNKNOWN state. Experts informed.
Gosselin, DeRossi, Ballardin replaced the TempController in EERoom at 11:30 UTC. Laser again ON.
Upon concluded the recovery of the injection system I set DET_MAIN Metatron node in SHUTTER_CLOSED, ITF_LOCK in EXEC and I started to recover the alignment of both cavities. In particular the NE.

COMMISSIONING mode set.

Relocked at CARM_NULL_1F at 14:56 UTC, after the usual cross-alignment in ACQUIRE_DRMI and after several unsuccesfully locking attempts.

SBE
13:00 UTC - SWEB vertical position restored via stepping motor.

DAQ
14:01 UTC - BaDAQ process crashed / restarted via VPM

DET
14:21 UTC - SDB2_B1p_QD1_GALVO closed via VPM
14:30 UTC - I rearmed Vbias and open shutters for B1pQD1 and B1pQD2.
14:45 UTC - SDB2_B1p_QD1_GALVO, B5_QD1 closed via VPM

We installed one accelerometer and one microphone inside the 1500W building. 

One meggit accelerometer is placed on the concrete floor, veritcally oriented, close to the INGV gravimeter inside the Fiber Lab: picture 1.

• channel name is SQZ_ACC_1500W_SQZ ADC, more info in https://apps-online.virgo-gw.eu/squeezing/?r=857

One GRASS AZ46 microphone  is placed in the Bd. hall: picture 2.

• channel name is W1500_ENV_1500W_MIC, it is read from the DAQ box used for the ROBOT* sensors: https://vpmrd.virgo.infn.it:40000/main.html, W1500_dbox, W1500_ADC0

Figure 1. The test of last week of adding an SRC length detuning was able to improve the BNS range by 6 Mpc from ~38Mpc to ~44Mpc (15% increase). At the same time the B1p power decreased from 265mW to 225mW (15% decrease), and the power in the arms increased by 1% (probably due to less losses to the order 8 and 9 mode).

The DCP as measured by Hrec decreased from 430Hz to 380Hz, and the phase of the 491Hz line in DARM as measured by ASC_DCP_HF_B1_phi changed by ~0.05 radian. The two are roughly consistent with each other and would correspond to a 7nm SRC length detuning using an analytical calculation from André Thüring PhD Thesis.

What is a bit surprising is that the amplitude of the 491Hz line increases by around 1%.

Figure 2. Looking at the analytical DARM response for 7nm and 0nm SRC detuning, the ratio is supposed to increase only in the 100Hz to 400Hz band by 1%. So the DARM response change doesn't seem to be a good explanation as at 491Hz, it is supposed to decrease by 1%.

Maybe the right explanation is that SDB1 turns by 3 urad following the SRC detuning.

During the night after the NE RH was restarted the interferometer was locked in LN2.  https://logbook.virgo-gw.eu/virgo/?r=68655

Figure 1. Shows that during that night the B1p power decreased from 300mW to 180mW, as expected as the time scale for the full RH transient is of the order of 12 hours. The optical gain has also increased slightly by ~1% and the power in the arms, which might be also explained by the mode matching between the two arms improving as the ring heater thermal deformation arrives to its normal working point. However there was no significant change in the BNS range with an increase of less than 1Mpc. This shows that the EM differential RoC matching doesn't play a role in the mystery noise, as has already been observed a few years ago.

Despite that, the 15cm SR diaphragm has clearly shown that HOM are the vector of the 1/f^{2/3} noise, and the conclusion is that the dominant HOM that we see on B1p are not the ones that cause the mystery noise. The reason is most likely that HOM we see on B1p are mostly in the contrast defect quadratures, due to the difference in amplitude between the two beams interfering at the beam splitter. While DC read-out is in the quadrature corresponding to the difference in shape between the two beams at the beam splitter. That DC read-out quadrature can also have HOM, and they don't seem to be related to the contrast defect HOM, by which I mean they are not just a coupling of the contrast defect quadrature HOM due to phase fluctuations, but have an actually different physical origin.

Figure 2. Shows the results for the scans of the EDB OMC that were happening that night, as expected the dominant power was in the order 2 mode, and has decreased by a factor 3 during the night.

Figure 1. The temperature of the NI etalon control started dropping today. Looking at the monitoring of the heating belt output it became intermitent.

This issue has appeared several times in the past and was solved by replacing the Kert power supply: https://logbook.virgo-gw.eu/virgo/?r=67582

We should consider starting to make the replacement of these power supplies on fixed schedule based on past expererience (for example changing them every year or two) instead of waiting for the power supply to fail and then have a thermal transient in the etalon loop lasting a for several days.

ITF found in COMMISSIONING Mode and LOW_NOISE_3_ALIGNED State.
All times are UTC.
14:30 - 16:00 Test of reduction in SDB1 angular set point drift control loop gain (Was, #68684);
18:20:37 Unlock;
18:44:58 Unlock at the end of CARM_NULL_1F;
18:58:10 Unlock at LOCKING_CARM_NULL_1F;
19:31:41 Unlock from ACQUIRE_LOW_NOISE_3_ALIGNED;
20:09:50 ITF reached LOW_NOISE_3_ALIGNED;
20:23:03 Unlock, DET_MAIN Node went in UNKNOWN State, I restored it Requesting INIT state and then SHUTTER_CLOSED;
21:01:38 ITF reached LOW_NOISE_3_ALIGNED;
ITF left in LOW_NOISE_3_ALIGNED State and COMMISSIONING Mode with AUTORELOCK_FAILSAFE engaged.

Today between 14:30 UTC and 16:00 UTC I have reduced the gain of the SDB1 angular set point drift control loop by a factor 4.The motivation is that the angular motion of SDB1, especially in TY, looks correlated with the BNS range and with the optical gain fluctuation measured by Hrec.

Figure 1 shows the result compared with beferoe and after. The fluctuations on SDB1 LC TX/TY decrease when the drift control has lower gain, but there is no change in the BNS fluctuation, DARM gain fluctuations, or anything else.

An interesting comparison can be done with old data taken with an intermediate SR TY misalignment. Fig 1 shows the comparison when the DCP is about 270 Hz: the mystery noise is clearly lower. Fig 2 shows that the working point is quite similar, according to the DCP and the optical gain; now the dark fringe is much darker.

As we know, in the past the mystery noise was lower with a higher misalignement (fig3); now, going further with the misalignament the curve does not change in the region where the mystery noise is supposed to be limiting (fig 4). To be noticed that there is still an improvement of the dark fringe when the DCP is pushed down (fig 5).

A rough estimation of the noise components (fig 6) says that a pessimistic estimation of the thermal noise (0.7e-23  @ 100 Hz) is almost sufficient to explain the curve.

ITF found unlocked with both cavities misaligned; to realign them I had to move the PR. The ITF relocked at the first attempt in LN3_Aligned.

At 9:30 UTC Paolo made some test to acquire data with SR misaligned in different steps.

At 13:28 UTC, following Maddalena's instrunctions, I changed the Etalon setpoint:

•  NI:NI Set point [NI_RH_SET=18.66,rampTime=3600]' sent to LSC_Etalon_Acl
• WI:WI Set point [WI_RH_SET=18.82,rampTime=3600]' sent to LSC_Etalon_Acl

ITF left locked in LN3_Aligned.

Same plots again, where yellow dots now include this morning's scan of the SRM angle. It seems that the strain noise at 110÷133 Hz is flat below 300 Hz DCP frequency. And the effect above 300 Hz DCP is mostly due to optical gain, i.e. the net broadband noise in power units does not change significantly when misaligning SR. 

Starting form 9:30 UTC, for two hours some data have been acquired with SR TY misaligned in many steps, up to the usual 2 urad which sets the DCP below 200 Hz. The aligned state with SR TY in loop has been recovered at 11:35 UTC.