At the beginning of the shift (13:09UTC), ITF unlocked
At the beginning of the shift (13:09UTC), ITF unlocked
ITF is found in SCIENCE.
At 6:01 UTC I set the ITF in Maintenance Mode, here is the list of the activities communicated to the Control Room:
Periodic Tasks carried out by the Operator:
CH (W) | Inner DAS (W) | Outer DAS (W) | |
W Pickoff | 0.255 | 0 | 0.22 |
N Pickoff | 0.68 | 0.065 | 0.602 |
11:25 UTC Maintenance ended, I re-aligned the CITF and relocked the ITF at the first attempt, back in SCIENCE at 11:35 UTC.
11:58 UTC Vpm restarted
SQZ not working properly, F. Sorrentino contacted H. Valbruch for it.
Sub-system reportsISC
I changed the set-points of NI and WI etalon suggested by M. Mantovani.
12:13 UTC WI new set point 19.825 and NI new set point 20.1
[entry unexpectedly stuck in drafts]
During the night the WI CO2 laser changed the state, but ITF remained locked: Magazzu sent an email and report about the DMS flag in the Virgo logbook (64134).
During this morning maintenance activities were foreseen, so I waited at least for the taking of thermal camera images and chiller refilling before making actions for WI CO2 laser power recovery. After the chiller refilling and filter change, the WI CO2 main laser state was mainly recovered (see Fig. 1).
A further activity was foreseen during maintenance in TCS room (repair WI etalon heating belt, 64114). I waited for the end of this activity to further check CO2 powers (Gianmatteo already checked them 64135) and eventually act on waveplates.
At 09.00 UTC, with ITF in down, I checked all CO2 powers restoring the nominal ones. This activity has been completed at 09.18 UTC.
We have removed the temporary magnetic and seismic probes from the DT turbo, placed there on Feb. 24.
We placed the magnetic probe onto the MC tube (similar location where it had been in the past). The acquired channel is perpendicular to the tube (probe "X"). We used the same name: ENV_CEB_MAG_MC_TUBE.
This morning during the maintenance break, we replaced a fan on the DT turbomolecular pump after noticing some unusual noise, possibly due to a worn bearing. We installed a standard domestic fan, mounted on rubber pads as usual (picture attached)
This morning I slightly tweaked the alignment of the optics showed in entry 56246 inside the AEI sqzueezer board, in order to improve the MZI contrast and the pump beam alignment on the OPA.
I worked on MZI between 7:43 and 7:47 UTC, and on OPA between 7:52 and 8:19 UTC.
The MZI at the beginning was already quite high, and I could only improve it marginally - from 68% to 73%, see first attached plot.
After tweaking the pump beam alignment, the OPA peak trasmission improved by about 5% (see second attached plot) and the main HOM in OPA scan was reduced by a comparable amount (see third attached plot).
ITF found in LOW_NOISE_3_SQZ and in Science Mode. It kept the lock for the whole shift.
Guard Tour (UTC):
21:01 - 21:29
23:02 - 23:29
01:01 - 01:29
03:01 - 03:29
TCS
At around 4:25 UTC the value of TCS_WI_CO2_PWROUT suddenly decreased (see attached plot). Expert informed via mail of the issue.
I found ITF in SCIENCE MODE; It remained locked for the whole shift.
No DMS Events to report
Guard Tour (UTC):
17:08 - 17:35
19:01 - 19:29
The automated noise injections on Friday 26th worked as intended: there were two minutes of noise injection on each longitudinal DoFs (Figs.1-5).
The coherence with Hrec is unsatisfying though (Figs.6-10). A finer tuning of the amplitudes of the noise injections might be necessary.
I found ITF in SCIENCE; It remained locked for the whole shift.
I'm repeating the analysis described in #63996 for the second week of O4b. The selected data segment is: 2024-04-20 22:14:40 to 2024-04-21 18:30:12 (72932.0 sec).
As before, I attach the CSV with the identified frequencies and the PDF with the various regions of the spectrum.
In 2017 the PRC was measured to have a wrong length by 3-4mm: https://logbook.virgo-gw.eu/virgo/?r=36884
I have checked in Optickle that mistuning the sideband frequency by a 2 kHz (which should be equivalent to a 4mm cavity length change), the sideband behavior becomes asymetric with PRCL offset. WIth the sideband power increasing by 1-2% in one direction and decreasing by 1-2% in the other direction, when changing the PRCL offset by ~0.2nm. This is similar to the measurements done last Friday, but it disagrees with the PRCL calibration done a year ago: https://logbook.virgo-gw.eu/virgo/?r=36884. That calibration would say that the PRCL offset was changed by 1.5nm, which would make the sideband power change by a few tens of percent. Maybe that calibration is no longer valid, as some normalizing factors could have been changed when chaning PRCL error signal from 8MHz to 6MHz sideband, or when installing the RAMS on the 6MHz.
Figure 1 shows in red the normal situation, in blue with the frequency to amplitude noise coupling divided by ~2 by adding the PRCL offset and in purple by adding the PRCL offset which zeros the coupling. The power fluctuation on B2 at ~1.5Hz improve by a factor 10 when reducing the coupling, on B4 there is also an improvement by a factor ~3, while on B4 12MHz the situation becomes worse, with fluctuations increasing by a factor 2. That would make sense if we improve the resonance condition for the carrier and degrade for the 6MHz sideband.
Figure 2 are the same times but with colors not in the same order. It includes also the B7 and B8 powers, and while on B8 the improvement is monotonic when improving the frequency to amplitude noise conversion, on B7 it is not the case. Is that a consequence of one arm being 3cm shorter than the other?
Lets assume that the PRC length is wrong by ~3mm, there are several options to resolve this:
Glitches might have stopped because the WI etalon loop error signal has finally become negative. The loop is asking for cooling the WI tower, which means turning the heating belt off. This switch off didn't happen immediately, but with an on/off for 10 minutes, so it is most likely due to the loop itself and not from an intentional switch off.
I have run a cross-correlation analysis using deltas for each glitch time, and all the _mean and _rms channels from the trend frame. I confirm what was highlighted by Bas in the previous comment:
1) Since April 26 20:00 UTC, the LSC_WI_HB_moni channel has started behaving oddly, with a sequence of square waves from zero to the set point. This is simultaneous with the appearance of the new glitches. The channel monitoring the electric potential, LSC_WI_HB_cmd_100Hz_FS, doesn't present similar behaviour. Figure 1 shows the glitchgram, with the new glitches showing up at the end of Apr 26, and the time series of the two channels monitoring the WI etalon.
2) The glitches in hrec are synchronous with the steps in the square wave visible in LSC_WI_HB_moni.
3) The correlation analysis with the _rms and the _mean trend channels has produced no other correlated channel with these glitches.
Glitches disappeared around 6:45 UTC. Has some action been taken? Indeed, square waves were seen also in the CEB UPS CURR T monitor, as for the old problem with WI heating belts that Bas pointed out.
These new glitches seem to originate from some noise source activating for ~2 minutes and off for ~4, similar to a square wave.
First of all, I identified the new glitch family selecting the omicron triggers with peak frequency lower than 40 Hz and SNR between 15 and 60. Then, plotting the temporal distances in the occurrences of consecutive glitches (similarly to what has been done for the 25-minute glitches), I noticed that these alternate between ~115 seconds and 250 or 225 seconds in the examined time interval: figure 1.
Figure 2 and 3 show the spectrograms of two consecutive glitches in hrec, and their whiten time series. The latter show opposite behaviours, with a spike up in one glitch, followed by a spike down in the next one.
Similar plots for the magnetometers at the West Input, show a step-like behaviour: figure 4 and 5.
The (non-whitened) time series of this magnetometer channel shows more clearly the square wave behaviour in the correspondence of each pair of glitches: figure 6.
The next task is finding what source is activating with a similar timing.
ITF found in LOW_NOISE_3_SQZ and in Science Mode.
At 18:30 UTC I set the ITF in CALIBRATION Mode to perform the planned measurements:
ITF back in Science mode from 19:16 UTC.
Guard Tour (UTC):
14:05 - 14:55
15:57 - 16:32
19:06 - 19:36
DAQ
The process FCIM_MotSwitch stopped working at around 17:41 UTC. Process restarted via VPM at 17:44 UTC.
The ITF kept science mode all the shift.
Guard tours (UTC):
05:55 --> 06:30
08:00 --> 08:35
09:48 --> 10:33
11:55 --> 12:30
Nice find. Figure 1 and 2 made using omicron-plot show that these glitches in the WI MAG started at the same time as the glitches in h(t) around 20:00 UTC, and that they have not been happening the day before, and have been happening since then. There are magnetic glitches between 150Hz and 200Hz that have stopped a few hours before the glitches at ~30Hz started. The two might be related.
Figure 3 shows that this glitches are not visible on the NI MAG. So it is likely that the issue is close to the WI.
Next steps should be:
UPV + VetoPerf point to the following channels (without the _0 which is added in UPV to label the corresponding veto):
V0 → V1:ENV_WI_MAG_W_0, vetoed clusters: 454 (80.927 %)
V1 → V1:ENV_WI_MAG_N_0, vetoed clusters: 452 (80.570 %)
V2 → V1:ENV_WI_MAG_V_0, vetoed clusters: 452 (80.570 %)
V3 → V1:TCS_WI_CO2_ISSIN_0, vetoed clusters: 172 (30.660 %)
V4 → V1:ENV_CEB_ELECTRIC_0, vetoed clusters: 121 (21.569 %)
See https://scientists.virgo-gw.eu/DataAnalysis/DetCharDev/users/narnaud/UPV/20240428_glitches/V1:Hrec_hoft_16384Hz/perf/vp.html#V0 -> Click here to expand -> Time-frequency trigger distribution: before/after veto.
In attachment the Omicron plots of h(t) and V1:ENV_WI_MAG_W, for comparison.