DRAFT - REPORT  IN PROGRESS - will be finalized at the end of the shift

ITF found in LOW_NOISE_3 and in Science Mode. It unlocked at 21:04 UTC, back in Science Mode from 21:52 UTC.

Guard Tour (UTC)
20:55 - 21:32
23:16 - 23:46
1:50 - 2:23

There was no noticeable difference in BNS range when the RFC was off resonance in LN3.

Figure 1. Comparing data with RFC off-resonance (blue) and on resonance (purple), there is no change in spectrum at any ports of the interferometer. The only difference is for the RFC itself, where there is no light in transmission, and the light reflection becomes an imperfect indepent measure of the laser intensity noise. The clearance between the 1501Hz PSTAB and the noise level looks the same for the RFC reflection and for the PSTAB out-of-loop channel (PDd).

Figure 2. Looking at the OMC length spectrum as expected the noise is much higher without the RFC loop (blue), especially at 30mHz. The only exception is a bump at ~3Hz which is present when the RFC loop is closed (purple), I guess this is the frequency at which the RFC control loop of CARM has the phase going through zero, creating gain peaking.

Today, I found ITF in SCIENCE. 

• 05:12 UTC, ITF unlocked. At 06:39 UTC, ITF relocked with autorelock and returned to SCIENCE.
• 11:45 UTC, ITF unlocked again. NE misaligned after the unlock, so I manually realigned to restart the lock.

ITF left in relocking 

Guard Tours (UTC):

• 06:00-6:40
• 08:10-08:50
• 10:30-11:10

ITF found at CARM_NULL_1F, back in Science Mode from 23:24 UTC. It kept the lock for the rest of the shift.

Guard Tour (UTC)
22:14 - 22:55
1:25 - 2:02 
3:03 - 4:37

This afternoon the ITF unlocked once at 16:27UTC, it relocked at the third attempt, science mode started at 17:35UTC; daily calibration and ISC noise injections from 18:30UTC to 19:03UTC; unlocked again at 21:11UTC, relock in progress.

-guard tours (UTC):
16:45 --> 17:15
20:00 --> 20:30

Calibration
- 18:30UTC: CALIBRATED_DF_DAILY;

ISC
- 18:43UTC: ASC injections (inject_asc_test.py);

Today, I found ITF in SCIENCE. 

• 06:34 UTC, ITF unlocked. At 07:21 UTC, ITF relocked with autorelock and returned to SCIENCE.
• 07:57 UTC, ITF unlocked again. At 08:46 UTC, ITF relocked with autorelock and returned to SCIENCE.
• 10:03 UTC, ITF unlocked again. At 10:49 UTC, ITF relocked with autorelock and returned to SCIENCE.
• 12:58 UTC, ITF unlocked again. 

iTF left in relocking acquisition 

Guard Tours (UTC):
06:30 - 07:10
11:15 - 11:55
14:15 - 14:45

ITF found in relocking phase; it went in Science mode at 22:41 UTC.

It unlocked at 1:35 UTC;  it went in Science mode at 2:24 UTC.

It unlocked at 4:24 UTC;  it went in Science mode at 6:09  UTC.

Software

BacNet server restarted at 22:35 UTC because it was providing flat data.

Guard tours (time in UTC)

23:00-23:40; 1:10-1:45; 3:45-4:20

ITF found in LOW_NOISE_3 and in Science Mode. The BNS Range value was initially still lower than usual (around 27 Mpc). Taking advantage of an unlock at 14:17 UTC, Spinicelli and Gosselin went to the Laser Lab to change the gain of the PStab (see entry #66460). Activity concluded at 14:33 UTC, the ITF relocked at the first attempt, and the BNS Range returned to nominal value, back in Science Mode from 15:22 UTC.
The ITF unlocked at 17:35 UTC due to an earthquake (M 6.6, central Mid-Atlantic Ridge, 17:17 UTC), after the unlock the PMC power decreased, preventing the lock of the INJ System. Gosselin interveened in the Laser Lab to further adjust the gain, restoring the system at around 18:00 UTC. ITF back in Science Mode from 18:39 UTC.
It unlocked at 21:29 UTC, triggering the opening of the WI Inertial damping loop. After closing all the WI Loops at 21:44 UTC it was possible to start to relock.

Triggered by some PSTAB misbehavior this morning we noticed that there was an oscillation at around 19 kHz on the PMC error signal .
We went to the laser lab to decrease the gain by 2 dB (now 5dB on the attenuation), the oscillation disappeared (plot).
The oscillation might be present since the works on the SL and IMC loop on the 11/03 but was not a problem till today.

The glitches are gone as well: see https://vim-online.virgo-gw.eu/resources/2025-03-28/resources/20250328_ana_plot_Hrec_hoft_16384Hz_freqtime.png.

During today’s daily meeting, people reported that the ITF lock durations are quite small and Paolo explained that can be due to the troubles of ISC data delivered in late .

Some investigations were made comparing the following channels

• ISC_Tpro_elasped_time giving the time used at each cycle to read the data, perform the calculation and build the packets sent on the Tolm network.
• Daq_ISCToISYS_Tolm_Send_Start  giving the transmission time of this packet . This packect is the first packet sent after the ones related to the suspension (NE,WE,BS.PR.SR.NI.WI)

This plot compare the trend of these channels for the 2024-04-01 and the 2025-03-28

• the ISC_Tpro has increased by 1us while the  Daq_ISCToISYS_Tolm_Send_Start has increased by 2us
• These increases are not understood

Today to ensure the correct running conditions, for the ACL taks running on the ISC_rtpc, the minimal elapsed time of the LSC_Acl task is set to 24 us, but all its operations needs only 16 us to be executed.

As a trick, the LSC_Acl server minimal elapsed time has been reduced by 1us , 23us instead of 24us . This operation has been done at the 2025-03-28-15h14m49-UTC .

This plot shows the effect of this reduction on the same channels as before:

• the ISC_Tpro_elasped_time has recovered its previous values
• but the Daq_ISCToISYS_Tolm_Send_Start  ones have been reduced by 1us only  

This entry is dated 18/03 but it got swallowed back in the Drafts.

The intervention from this morning, done with the North Arm still locked when the crate switched off (Fig. 1), had three consequences:

• excitation of the NE violin modes (Fig. 2, LOW_NOISE_2 today and two weeks ago);
• excitation of the NI vertical mode at 6.9 Hz (Fig. 3, CARM_NULL_1F today and last night), damped by hand in the afternoon as it saturated the B1 dynamics in DC Readout and above;
• an increase of the Tolm errors of the NI DSP (Fig. 4), maybe due to a jump on the NE flag (Fig. 5)?

Yesterday we wanted to take some data, in good weather condition, in LOW_NOISE_3 with the RFC out of resonance (i.e. with the CARM_SLOW loop open); here the sequence of actions:

• 15:39:34 UTC: we tried to open the loop in-lock, but the interferometer unlocked;
• 16:23:25 UTC: we reached again LOW_NOISE_3, without closing the loop in the first place; during the acquisition, another slower CARM loop was disengaged from the DSP, and one IP was moved enough to bring the RFC out of resonance;
• from 16:23:25 UTC to 18:00:00 UTC we were stably in LOW_NOISE_3 with the RFC out of resonance;
• 18:00:00 UTC: we started to bring back by hand the RFC on resonance, rolling back the two changes we made in bullet #2;
• 18:14:29 UTC: we tried to close the loop but we unlocked (usually we close it with the HighPower actuation, which has much more range to cope with it);
• the following relock was in standard conditions.

Science mode was re-engaged at 12:46:30 UTC (GPS 1427201208) with a BNS range of 48.8 Mpc, following the recovery of the injection. The range and sensitivity curve are consistent with the values observed earlier this morning.

This morning the ITF unlocked at 6:32UTC because of the big earthquake in Myanmar:

M 7.7 Mandalay, Burma Earthquake
Time 2025-03-28 07:20:54 (UTC+01:00)
Location 22.013°N 95.922°E
Depth 10.0 km

it's effects prevented to relock for about three hours, ITF relocked at LOW_NOISE_3 at 10:43UTC, at the beginning of the lock the BNS range was around 20-25Mpc, it came back to the usual values by itself, science mode started at 12:46UTC.

SBE
SPRB, SDB2, SNEB and SWEB position loops opened by the guardians because of the earthquake, controls properly closed.

Following the recent earthquake in Burma (USGS Link), the BNS range has dropped to 15-25 Mpc. As a result, Science mode operations, which began at 10:46 UTC (GPS 1427194024), were interrupted at 11:31 UTC (1427196723 ) and will remain suspended until the range recovers above 40 Mpc.

As of 12:20 UTC, the range has been fluctuating between 20 and 25 Mpc for the past 30 minutes. Further monitoring is ongoing.

The segment [1427194024,1427196723) will be removed from the offline Science segments.

As the ITF was unlocked this morning, we used this time frame to review high rms values on the phase loops of NCal_WEN and NCal_WWN.

Using the external reloadConfig facility, we adjusted the gain of the corresponding ACL_FILTER_CH channels to improve loop efficiency

• ACL_FILTER_CH WEN_rotor_phase_corr "au" 1 20000 "WEN_rotor_phase_err" 3.0 "NCAL_rotor_phase_filter"  : gain increased from 1 to 3
• ACL_FILTER_CH WWN_rotor_phase_corr "au" 1 20000 "WWN_rotor_phase_err" 2.5 "NCAL_rotor_phase_filter" : gain increased from 1 to 2.5

It's a workaround due to the fact  that we forgot to measure the parameters of the polynomial used to build the command {NCAL} _motor_cmd_Hz_V during the installation phase. This will be done during the ITF shutdown

The attached plot show the trend of the WEN and WWN rotor phase error signal and its improvements

ITF found in Science mode with Autoscience enabled.

It unlocked at 22:41 UTC; it relocked at the first attempt without any actions and Science mode was set 23:27 UTC.

It unlocked again at 0:52 UTC because of the following earthquake M 6.1 - central Mid-Atlantic Ridge;  it relocked at the first attempt without any actions and Science mode was set 1:39 UTC.

It unlocked again 2:58 UTC; the ITF relocked by itself and Science mode was set 3:49 UTC. At 3:55 UTC I stopped Science mode for a few minutes to restore the WI CH flip mirror that was left down during the lock acquisition.

Guard tours (time in UTC)

19:00-19:41; 21:30-22:13; 23:34-00:10; 1:53-2:40; 4:00-4:40

ITF found during the locking acquisition, back in Science Mode from 14:36 UTC.
At 15:30 UTC I set the ITF in Commissioning Mode to allow the planned activity, LN3 with RFC off-resonance, carried out by Casanueva and Ruggi. Activity concluded at 18:49 UTC, ITF back in Science Mode from 19:04 UTC.
ITF left locked.

Guard Tour (UTC)
18:58 - 19:41
21:27 - 

ITF found in LOW_NOISE_3 in SCIENCE mode (AUTOSCIENCE_ON). 

At 04:33 UTC ITF unlocked due to end TM (MIR or MAR) correction saturation. To relock cavities I had to realign NE mirror (2 urad ty+). Autorelocking in progress...

Guard tours (UTC):
21:15 - 21:50
23:30 - 00:15
01:50 - 02:30
04:10 - 04:45

SBE
03:20 UTC - SPRB vertical position recovered via stepping motors.

ITF found in Science mode with autorelock enabled; it kept Science mode for all the shift.

Guard tours (time in UTC)

19:10-19:45; 21:10-21:45

We cleaned up the PAY lab at 1500W to prepare it for the deep cleaning tomorrow.

We removed as much material as possible and moved the bulkiest elements (Fig.1) away from the corners of the room to facilitate cleaning (Figs.3-4)

The smaller components and tools were packed in boxes on the shelves on the left side of the room (Fig.4), with bolts and Screws on the right (Fig.5).

In particular, instructed by Ettore, we disassembled the optical benches that hosted the local control of the LM payload in the vacuum chamber, and cleaned up cables and aluminum parts scattered around the area. We collected the components removed by the benches and the smaller pieces from the corners in the two boxes in the shelf on the opposite side of the room (Fig.6).

The larger pieces, like the optical benches themselves, were stored in the adjacent room that connects to the fiber lab (Figs.7-8-9).

We also found what we suppose to be the new WE mirror on the payoad table (Fig.10)