given that the past injections performed on CARM SLOW loop through the automatic script in /virgoDev/Automation/scripts/LSC/inject_lsc.py were not sufficiently accurate (fig.1),  today we increased of a factor 5 the noise amplitude. If this noise amplitude is not enough, we could increase it even further, there should be margin, see fig.2 and 3.

The DIFFp set point loop that minimizes the DIFFp dither lines in B1p DC might not give the right set point to maximize the DARM optical gain and the BNS range.

Figure 1 shows that the BNS range was decreasing by 5 Mpc yesterday for most of the day between 6:00 UTC and 19:00 UTC (afterwards there is a drop for 3h because of the calibration noise injections).

Figure 2 shows that at the same the optical gain has been decreasing, and started increasing again between 21:00 UTC and 24:00 UTC.

One can do a double demodulation of B1 at the 491.3Hz DARM line frequency and then demodulate the line magnitude at the DIFFp dither line frequency.

Figure 3 shows that at 6:00 UTC that demodulation was relatively close to zero for TX and TY, but at 16:00 UTC DIFFp TX was very far from zero. Which means that changing the DIFFp TX set point should be able to increase the DARM optical gain (and probably the BNS range)

Figure 4 shows that around 24:00 UTC when the BNS range was getting better the measured double demodulation signal was getting closer to zero.

Figure 5 shows than on April 10 when the DIFFp TX was not working and there was a forest of bumps appearing in the sensitivity the signal was even further away from zero.

So a double demodulation of B1 at 491.3Hz + DIFFp dither line frequency might be giving a good signal for the DIFFp set point to increase the DARM optical gain and the BNS range.

/users/mwas/ISC/B1_doubleDemod_DIFFp_20240331/B1_doubledemod.m

The servo has been re-engaged @ LN3 (and now it is in the automation)

It is visbile that the SDB2 structures disappear or reduced with the servo on, figure 1 purple servo off blue servo on.

It has been observed that the servo for the set point of DIFFp tx and ty is not active at low noise 3 (to minimize the B1p DC) and this has always had an impact on the structure on the detection bench caused by diffused ligth.

For this reason I' ve analyzed the last 20 days of LN3 locks and I' ve taken sets of 600 sec in which the correlation between the DIFFp TX and TY inputs and B1p DC are evaluated with a linear fit.

It is visible (for the tx dof) that the higher correlation (higher slope of the fit, which correspond to the set point far from the optimal one) corresponds to a larger amplitude of the peaks (in DARM).

This analysis is to stress the fact that we need to re-engage the servo @ LN3.

Yesterday I started the injection of SQZ into ITF at 20:20 UTC. When you did the test I was working on the switch off of EQB1 hardware and Filter cavity automation thus I think that the ITF data were not affected by my activity

Last night between 19:40 UTC and 19:50 UTC I have put an offset in the SR TX AA loop. The loop did not have the time to arrive to zero that offset but it did change SR TX by 0.3urad, then over a time scale of ~30min the loop has  recovered from that offset.

Figure 1. Shows that it did not have an impact on the CMRF (the motivation for this test), but there is a correlated drop in optical gain of DARM as measured by Hrec, even though ther was no impact on the DCP frequency. It might be a coincidence, or it might mean there is an impact and that trying the offset in the opposite direction would have increased instead of decrease the optical gain.

Note that squeezing tests where going in parallel, so the BNS range is not a useful figure of merit for that test.

Angular injections performed yesterday march 18th and last march 14th have been preliminary analyzed. A noise budget wrt HREC has been produced.

In order:

1. In Fig.1 is reported the projection of the DIFFp, PR and COMMp loops on Hrec, from the first set of measurments taken by hand, in order to set the 'ASC_NOISE' amplitude;
2. In Fig.2 is reported the projection of the DIFFp and COMMp loops on Hrec, from the second set of data taken with the automatic script. N.B. Due to the mispelling of the PR loops channel, the PR injections didn't go through. Addittionally, the stored GPS for the clean data (2024,03,18,10,10,01) was affected by a glitch, which spoiled the projection. Good clean data GPS is taken: 2024,03,18,08,16,30. ----> txt file has to be updated with this GPS.
3. In Fig.3 is reported the noise budget of the remaining loops (i.e. PR TX, PR TY and BS TX) , using the sensing noise injections performed last march 14th, plus the injections at the MAR level of BS TY, performed march 18th. For PR and BS TX loops (QPD sensing) the post channel to compute the transfer function wrt Hrec was 'ASC_DoF_CORR+Sc_DoF_noise', while for BS TY (op lev sensing), the post channel was 'Sc_BS_MAR_TY + Sc_BS_noise'.

For the results of Fig.s 1 and 2, DIFFp TY looks the one more limiting (to be investigated). Concerning the projections of Fig.3, results of BS both TX and TY are not reliable due to a lack of coherence with Hrec, probably due to the shape of the noise filter (bandpass centered at 5 Hz and 3.5 Hz respectively). Such measurements need to be taken again.

This morning the scope was to re-commission the scripts that inject noise on the LSC / ASC / SSFS loops. The LSC script was already ready, so we just run it to check that it was working properly. All the injections showed coherence with Hrec (SRCL wsa slighlty worse than the others, on Wednesday we would like to try a nosie injection at slightly lower frequencies 5-50Hz). The script can be found and launched at: /virgoDev/Automation/scripts/LSC/inject_lsc.py.  Today's injections GPS can be found at /virgoData/NoiseInjections/LSC/LSC_injection-1394783415. Notice that during these injections the Galvo of B4 QD1 opened. To be checked if it was a coincidence or if this happens consistently.

Next activity was to inject noise in the angular loops closed on QPD error signals (Commp, DIFFp and PR) in order to adjust the amplitudes of the noise injected. Note that BR TX loop is also measurable but we mispelled the DOF name in the function to perform the injection (to be repeated on Wednesday)

Clean data: Same for the LSC noise injections.
ASC noise shape = Butterworth bandpass between 5 and 50 Hz.
GPS time stamps of the injections:
- 8.21.15 UTC + 120 sec, DIFFp TX inj ampl 8e-6.
- 8.32.10 UTC + 120 sec, DIFFp TX inj ampl 1e-4.
- 8.55.00 UTC + 120 sec, PR TX inj ampl 1e-4.
- 9.06.15 UTC + 120 sec, PR TY inj ampl 2e-4.
- 9.22.30 UTC + 120 sec, COMMp TX inj ampl 9e-4.
- 9.33.40 UTC + 120 sec, COMMp TY inj ampl 1e-3.

We also wrote a symmetric code in order to inject noise in these loops, and we tested it. It can be found at: /virgoDev/Automation/scripts/ASC/inject_asc_test.py. The .txt file with the measurements is stored in the folder 'virgoData/NoiseInjection/ASC/ASC_injection-*GPS*.txt'. We would like to finish with the BS TX on Wednesday, and then inject noise through the driving to the remaining angualr DOFs (SR and softs).

As side activity we performed an OLTF measurement of the BS TY loop through the DSP (HF brench, optical lever sensing), in order to have a response of the roll-off of the loop tf.
Noise shape: bandpass 'bpass.flt' centered at 3.5 Hz.
- 9.54.30 + 120 sec, BS TY inj ampl 5e.3
We tested again the control filter for BS TX tested last thursday. This time, it was possible to appreciate the effect of the filter (gain more at 200 mHz). GPS of the test:
- 10.36.00 + 120 sec, clean data with standard filter.
- 10.39.30 + 120 sec, test with new filter (txCorrAA2.flt).
We left the new filter as default. In Fig.s 1 is reported the measurement of the HF brench of the open loop of the BS TY, while in Fig.2 is plotted the spectra with the response of the new control filter for BS TX (red) with respect the current one (blue).

FInally, we tried to inject noise to the SSFS. The first thing we did was to comment the "define SSFS_FLT_NOISE" in order to be able to change the filters online, and then we restarted SSFS_phi, SSFS_noise and SSFS_Ctrl. We relocked and we started to try to make nosie injections. After some trials, we managed to inject noise around the UGF, and we already created a dedicated script that can be found: /virgoDev/Atomation/scripts/LSC/inject_ssfs.py. On Wednesday we would like to add two more dedicated noise injections at lower frequencies.

We will work on the script to produce the noise budget online.

There is an issue about SR_TY versus DIFFp_TY alignment (and, at least partially, SDB1_TY) when we get to CARM_NULL_1F, which depends on the condition we get into such state regarding SR_TY alignment, i.e. whether it starts already aligned or not. This is linked to the recent apparently contradictory changes in the initial DIFFp_TY gain, which has been increased/decreased by 50% several times.

In the Figure an example of a full CARM_NULL_1F stretch (1040 s), when we started with SR still misaligned (so, unlocking after a sufficient amount of time spent in LOW_NOISE_3 or above), as it can be seen by the very low DCP. A few observations can be done:

• at the beginning, DIFFp has a quite low gain (if in the ~10 range); sometimes it is low enough that the loop, although in principle stable at such frequency, does not gain enough at 1.2 Hz and it starts to oscillate at such frequency, killing the coherence of the line and making the gain servo unable to correct it; we can see in this case the _I and _Q signals of DIFFp being very mixed, and bad altogether;
• if the gain is increased enough (in the ~18 Hz region), the DIFFp loop manages to behave correctly and the servo will work, but increasing the gain a lot to cope with this bad signal; by the way, starting the CARM_NULL_1F transition with the high gain is detrimental, ofter up to an unlock, if we start with SR already aligned, at least partially (proof this morning at 9:40:16 UTC and 9:50:22 UTC);
• but, as SR_TY is re-aligned by its own loop, the DIFFp signals will get eventually better, and quite abruptly the loop will get to its high gain region quite fast, so that the servo may not be able to decrease the gain fast enough; moreover, as soon as some oscillation will start, also in this case the coherence will drop and the servo will become useless; in the example in the picture, the gain has been halved by hand, making DIFFp to survive; then, the servo reduced it of a factor 2 more;
• in all of this, also SDB1_TY has a role, as it moves on TY quite a lot, not exactly at the very beginning (a couple of urads aside in the very beginning of the transition), but much more once the DIFFp optical gain and signals become decent again; I guess something similar may happen to the SDB1_TY signals.

Conclusion: we need to cope better with the SR_TY (mis)alignment also in CARM_NULL_1F.

I've moved the BS ty set-point servo to LN3 since it does not work with the SR aligned and if you need to work at LN2 it will make the itf to drift away.

The task of the shift was to make the whole lock acqusition with the SR ty close to the final position (~200Hz of DCP) in order to avoid the transient at LN3 which will detune the optimal tuning for the controllers.

We observed that this could not be done if the SR ty initial position is in the wrong side of the "Parabola". If this case happens the servo will bring the SR ty further away. Then for sure we have to start from the aligned position.

The automation has been restored in the normal configuration.

In any case other ideas to have the science mode with the optimal tuning are present and will be implemented next week.

the attached figure shows the successful test of DET_MAIN (cycle of SHUTTER OPEN / SHUTTER CLOSED) with ITF in DOWN.

This morning we continued and completed the recovery of the ITF lock up to Low Noise 3.

Low noise 3 reached a first time at 08h27 utc.

We use these data from 08h27 to 08h29 to check the blending of the B1s photodiode (see Fig.1 and Fig.2). The blending seems OK.

We had some data with stable BNS range around 52-53 Mpc from 09h00 up to ~09h35 utc (Figure 3).

During the previous lock acquisition we realized that we had forgotten to restore the B5 QD2 offsets used for dark fringe. This was done at next unlock, at 10h36 utc.

FbsDet: Remove SMS SDB2_dbox_bench, reload Config at 10h42 utc to recover SMS data produced by this process.

With Michal we changed some logic in DET_MAIN node in order to fix the issue with DET_MAIN node getting stuck in the state "SHUTTER_READY_FOR_CLOSING" when B1s safety is triggered (https://logbook.virgo-gw.eu/virgo/?r=63361):

• The SHUTTER_READY_FOR_CLOSING state has been removed ; instead we now directly go from SHUTTER_OPEN to SHUTTER_CLOSING state.
• We added the state SHUTTER_CHECK_CLOSED between SHUTTER_CLOSING and SHUTTER_CLOSED.
• In the class SHUTTER_CLOSING we have removed the check on B1s photodiode being enabled, and we have removed the check on the power on B1s and B1 during the closing of the shutter.

The DET_MAIN node has been loaded without issue.

ITF unlocked during lock acquisition from step 115 (transition of the DARM hand-off to B1_PD3) at 10h55m48 utc. Figure 4 shows that DET_MAIN wend to DOWN at the time of the unlock and then worked properly, renabling the B1s photodiode when passing through SHUTTER_CHECKED_CLOSED.

Opening and Closing of OMC shutter tested successfully with ITF in DOWN around 10h59 utc.

With ITF in DC readout: we adjusted the B1 demodulation phase for the OMC lock: changed from -0.64 to -0.40 rad at 12h11 utc.

Low Noise 3 reached at 12h18 utc (Figure 5), and interrupted manually at 12h43 utc to allow an activity on the automation.

Figure 6 shows what happened when the lock was interrupted: DET_MAIN passed correctly from the state "SHUTTER_CLOSED" to the state "SHUTTER_CLOSING", before going to DOWN. B1s safety was triggered when DET_MAIN was in SHUTTER_CLOSING, but the photodiode was reactivated  in SHUTTER_CHECKED_CLOSED and DET_MAIN eventually made it to SHUTTER CLOSED.

We analyzed the trend of the sidebands n LN2 and LN3 during the two last days, after the WI etalon step performed on Saturday 63230. It fits well with the etalon period 1/(0.257) deg (attached plots 1 and 2). The red points have been exluded correspond to the work of the QNR group.
We could not perform the same analysis for B1p and the OG because in the passage from LN2 to LN3 they change due to SR alignment.

The amplitude of the SRTy hes been set to 0 @ LN3

Figure 1 the 6.1Hz SR TY line looks quite high on B1p and B1s in LN3. This is not surprising as in LN3 we misalign SR in TY to adjust the DCP frequency. If it is not used for anything else, then it could be a good idea to turn off the SR TY line in LN3, to avoid unecessary power fluctuations on the dark port. I don't have any evidence that it causes issues, but it would be worth to check that it is indeed the case.

I have plotted the NI and WI RH temperatures vs the BNS. In the last week a scan of the NI temperature had been done (See Figure 1),  but the effect is much smaller than the one occurred the last ER (which was not clear if it was connected to the etalon scans).

In order to speed up the reaching of the best sensitivity in LN3 I've increased the SR ty loop gain of a factor 3 (from -0.001 to -0.003).

I've already tested it online but not a the beginning of the acquisition of the new signal. So at the next lock the behavior has to be checked.

The hystory of the misfunctioning:

- 23th November 4:00UTC start worsening

- 24th November 11:30UTC balancing fixed

- 24th Novemeber 15:07UTC start worsening again

- 27th Novemeber 8:00UTC balancing fixed by coming back to the 23th November values

- 28th November 19:00UTC start worsening again

The SR ty LC is not working properly anymore since yesterday, see Figure 1. This actuator un-balancing has occurred already twice in the last week.

The SR ty excessive movement can be the cause of the DC readout and LN1 locking problem (to be checked)

a deeper analysis will be performed to undestand the cause of the mis-balancing.

I've commented the engagment of SR alignment since the wp does not seems to be optimal and a fine tune of the demodulation phases is required.

Given the bursts of noise on B7 and B8 at 85Hz and on the RFC error signal when the PR is aligned (see attached plot), we checked the tuning of the FI (62470) and, once we knew that it is work properly, the other hypotesis was a ghost beam in SIB2.

We found that one of the galvo on B2 QD2 was close to saturation. After reducing it (62472) the bursts disappeared and we were able to reach carm null 3f.

We added in ASC pre the demodulation of the phase DCP HF B1 phi (in addition of the demodulation of DCP HF B1 Q, which is currently used).

The added/modified lines in the ASC_pre process are: 67, 70, 72 and from 1498 to 1538.

The signals are now available online and they are called ASC_SR_TX/TY_DCP_HF_phi_B1_I/Q, we will look at them once the ITF will be locked

This morning I profit of few minutes before the start of the maintenance since the ITF was in LN3.

I wanted to check if the zero of the SR alignment error signal was optimal. I opened the SR AA and I moved manually the SR set point.

As it is visible in Figure 1 the aligned position using the error signal is not the optimal one.

Purple : aligned position found with the error signal signal

Blue : adding 0.4 urad in ty

the blue position shows an higher DCP and better range.

To be investigated better. We should implement the phi signal to see if it gives a better 0.

The goal of the shift was to perform  measurements to be used for the nonlinear noise detection.

Four stretches of data of about 30 minutes (plus some time for Hrec to converge) in LN2 were measured where each of the CITF lines were consecutively turned off:

15:30 + 30 min clean data in LN2 with all lines on

16:00:30 PRCL Line off 

16:40:00 PRCL + MICH Line off 

17:22:30 PRCL + MICH + SRCL Line off

18:00:00 Unlock 

The next lock I used to put back the new diagonalisation change, but with the final update which seemed to cause problems reverted (see this entry). The diagonalisation seems to work well again. Some fluctuations of the PRCL gain are still initially observed in the first few iterations but afterwards they stabilize and the fluctuations are less excessive (see Fig. 1). We will monitor the situation tomorrow and for now the new algorithm has thus been left enabled. 

We then went to LN2 and turned the lines off to continue the measurements but forgot to turn off the PyDiag process and consequently unlocked due to excessive waits. A safety will be built into the PyDiag process to prevent this from happening in the future.

In the last part of the shift we suffered systematic unlocks in 3f. Most of them show an oscillation in the central DOFs, at relatively high frequencies. We also noticed that the coherence of the UGF lines of MICH and SRCL were low when reaching CARM NULL 3f. We tried decreasing the gains (mich from 0.6 to 0.45 and SRCL from 0.1 to 0.08) but it was not enough to survive for a long time.

Last unlock was even sooner during the lock acquisitin, 400mW, so we asked Diana to check the CO2 powers instead of making a RH step. Since it is already late we will check the demodulation phases of MICH and SRCL during the lock acquisition tomorrow.