This morning we start with the IR alignment recovery .

Being SQB1 open, we look at the IR and GR beams overlapp  between SQB1_M21, M22 and M23, where it is possible observe both the incoming beams and the FC_IM retroreflected beam, once we have the last. In particular it is easy to overlapp looking the retroreflected from dichroic SQB1_M23 toward the FI. The overlapp has been done by acting on the cited three mirrors, but expecially on  SQB1_M22 and SQB1_M23. We checked that the retroreflected IR coming from the SQB1_FI to EQB1  was well centered in SQB1_FI2. This has been done moving SQB1_M21  both in the vertical and horizontal direction until the beam coming out from the SQB1_FI3 first polarizer on SQB1_M12 was cut for both the direction, in both versus: we left the beam at the  center of these range.

The  mirrors pico motors positions were:

SQB1_M21_H :-118160

SQB1_M21_V :  -26712

SQB1_M22_H :  -53655

SQB1_M22_V:   0

SQB1_M23_H :  -18400

SQB1_M23_V:   -16500.

POWER CHECK:

BAB:

• EQB1_FI_Pin=1.90+/- 0.02 mW
• EQB1_FI_Pout=1.90+/-0.02 mW
• SQB1_FI2_Pin=1.90 +/-0.02 mW
• SQB1_FI2_Pout=1.90 +/-0.02 mW
• SQB1_FI3_Pout_POL1=1.85 +/-0.03 mW  (Power from FC to EQb1, but the power meter sensor was 'floating')

SC:  18.9 mW;

GR:

• AOM_Pin=22.40 +/- .02 mW
• EQB!_FIin= 14.5 +/- .02 mW
• EQB!_FIout= 13.33 +/- .02 mW

ALUGNMENT ON EQB1_HD CAMs and LO overlapp

After this, we align the  retroreflected IR on the EQB1_HD. The beam has been centered on all the steering mirrors SQB1_M12, M13 and M14 and on EQB1_M6 and overlapped weith the LO. To do this we remove d the two holed absorbing  scrren between

M13 and M14 and just at the end of SQB1 path.  We check the beam height with a movable diaphragm, but on the last absorbing hoed screen in any case results a litle low: even the beam leaving SQB1 to go in EQB1 seemed not cut, we decide to leave the screen out (it is just clumped on the benchnear the original posiiton, as it can see in the attached SQB1 picture)

We  obtain a HD visibility with BAB abd LO ~ 80%. at beginning, and  the end of the shift  ~85% (see attached pictures) This improvement after  tring to better  align the IR on the FC and keeping as other reference the beam on HD cams.

The BAB retroreflected beam appears very similar in dimension to the LO on both the HD_CAMs (see picture BABfromFC_comparison), while is not the case for the SC (see SC_LO_fromFC_)

To overlapp ad the best

ALIGNMENt ON FCEB

Once aligned, we have observed the FC trasmission on  FCEB_IR_PD. To be sure that the observed peaks were the IR and not the green, we  have turned off the GR shutter (see pictures).  IWe observed both the BAB and the  SC resonances, observing more o less the expected ration between the transmitted power, about a factor 10 (BAB ~1.95 mW  and  SC ~18.8 mW are the power measured on EQB1). The BAB resonance appears more 'clean' as expected by the fact that yesterday we was not able to improve the matching between the SC and OPO due to a problem in the alugnment of the fotodiode that measure the beat between SC refelected by the OPO and BAB.

We try to improve the alignment of the BAB on the FC, but the fact that we cannot for the moment apply to the AOM a ramp  with a sutable amplthe that allow to observe more than half FSR.

We work unlocking for few time the FC on  green to observe the resonance with  the mirrors free running. In this way we have  improved a little the alignment.

We will update the data relative to IR trasmission (BAB and SC).

The plan is to give a right offset to the AOM RF ina way to bring the cavity near the IR resonance and scan in that region while the alignment will be improved.

The first part of the shift was dedicated to perform all the modifications needed in order to use as new error signal B4_PD1_6MHz instead of B2_PD3, for SSFS (see https://logbook.virgo-gw.eu/virgo/?r=52705).

After this modifications, we needed to retune the B2_169MHz, by injecting noise on PRCL from 9.30 UTC (noise ampl 4e-3). New tuned phase is:
- SIB2_B2_169MHz_phi0 = 0.65 (from 1.1);
By looking at the PRCL line at 67.1 Hz we retuned also:
- SIB2_B2_18MHz_phi0 = 4.95 (from 5.3).

At this point we started to prepare the functions in order to perform the hand-off of CARM to the B4_PD1_6MHz signal. 

In order to do this we started selecting PD1 by setting the relay B4_PD_SELECT = 0; then we tuned the SPRB_B4_6MHz phase by looking at the 1111 Hz line. The tuned value is: SPRB_B4_6MHz_Phi0 = 1.2.

We added on LSC a compensated "fake" signal in order to check the right value of the weigth between B7B8 DC and the new error signal.
After we found a good value of this weigth we modified few lines on ITF_lock_library.py script within the carm_null() functions:
    
    cm_send('LSC_Acl','AcFltChFilterSet', 'B4_6MHz_I_COMP','CARM_MC_RF',1.0, 'apply')
  
    cm_send('LSC_Acl', 'AcSumChSet', 'CARM_MC_INPUT', 5.0, carm_cali, 'B4_6MHz_I_COMP' , 0.0,  'B7_B8_DC_SUM_SQRT', 'load')  
    
With carm_cali=-0.07.

After this, we attempted two trials of hand-off respectively at 10.47 UTC and 12.35 UTC.

Both of the attempts ended in an unlock due to a 300 Hz oscillation  (10.47 UTC), due to most probably a high gain oscillation of CARM after which we decreased the carm_cali to 0.07 (from 0.01), and 10 Hz oscillation (12.35 UTC).

The activity will be continued in the afternoon shift.

The modification to the dithering seems to work well. We could keep the filter cavity stably locked during the whole night yesterday. 

The first part of the shift was dedicated to the Change of SSFS input for B4 6MHz (see entry #52705). After this activity was completed at 7:55 UTC the planned ISC activity, carried out by Casanueva and Pinto, started. The work proceeded without major issues.
Other activities carried out during the shift:

• SGD - IR Alignment to FLT, EQB1 and EQB2 (Grimaldi, De Laurentis);

ISC activity still in progress.

SBE
At 13:17 UTC the Vertical Loop of SWEB opened. From 13:26 UTC I acted on the related Motor3 with the Position Loop open and returned LC_Y near its setpoint. Position loop closed again at 13:35 UTC.

DAQ
(30-07-2021 09:25 - 30-07-2021 09:45) From remote
Status: Ended
Description: At around 9:20 UTC we lost the camera images coming from the Injection system. After investigating the related process (INJ_Img) it was noted that the rtpc11 was not responding anymore.
Actions undertaken: I contacted the DAQ Oncall (Letendre) which, we the help of Pacaud, rebooted the machine at 9:45 UTC (see report #52707).

This morning rtpc11 became unreachable. Rtpc11 was rebooted and the processes restored around 9h54 UTC.

This morning we have changed the hard/software in order to stop using B2 PD3 as an input for the SSFS and start using B4 PD1 6MHz instead.

We have made the corresponding changes to SIB2 and SPRB dbox bench. We had to reconfigure both, so it is possible that we will have to retune the phases of B2.

Then we have proceed to made the software changes to SSFS processes and we have restarted them. We have checked that SSFS B4 PD1 and SPRB B4 PD1 signals are coherent, so the changes have been successful. Now the error signal used by default for the SSFS is B4 PD1 6MHz.

ITF State: Cavities locked.
ITF Mode: Commissioning.
Quick Summary: IMC and RFC locked; all Suspensions loops closed; SQB1 in Air with loops open, all other SBE loops closed;
Activities ongoing since this morning: No activity is known so far in the Control Room. 

After opening SQB1 we had some problem in closing dithering aligment loops.

We did the following modifications: 

• BPC dithering line amplitude from 0.002 to 0.1 
• BPC loop gain from 0.00025 to 0.00003
• New beam centering setpoint ( FCIM TX = -5, FCIM TY = 8, FCEM TX = -5, FCEM TY = -10)

After this modifications the loops works fine again. The maximum power achieved is 3.5 V, but we have an additional vieport on the beam path.

The aim of the shift was to keep investigating the behaviour of the B2 QPD galvos and to characterize the DRMI loops in carm null. 

B2 QD2 galvo investigations:

Since in the previous shift (52691) we noticed that the B2 beam and  SIB2 B2 QD2 galvo was behaving unexpectedly during the jump to carm offset zero, Was and Gouaty added the possibility of locking the galvo loop using the 2f (12 MHz magnitude) signal.

We therefore checked the difference between locking the galvo loop on the DC and on the 12 MHz loops at various stages of the carm offset reduction procedure (see figure 1, in which the top left plot shows whether the DC or the 2f signal is used). As can be seen in figure 1 there is always a difference between the working point of the DC and of the 2f signal. In particular, at high powers (200 mW and above), using the 2f signal often leads to saturation and consequent opening of the galvo loop, preventing to use the 2f signal reliably. Several tests have been performed at 300 mW to check if the B2 beam position and galvo working point was related to the SR or BS angular working point, but no clear dependence was noticed.  Additionally, the delta between the DC and 2f working points changed from lock to lock.  No noticeable difference was noted on the PR AA signal (that uses the B2 QD2 signal) when the switch is performed or when the galvo loop opened. Additional observations about the DC vs 2f signal for B2 can be found in 52699.

Carm offset reduction investigation:

Multiple carm offset reduction attempts have been performed during the shift, both to performe the B2 investigation, and to attempt LSC loops noise injections at carm offset zero, with the aim of calibrating the final handoff of the CITF loops to the 1f signals. Unfortunately, 10 Hz oscillations (figure 2 and 3) prevented us to stay in carm offset zero for long enough to performe the injection except for the lock at 20.55 UTC in which we performed 120s of noise injections on PRCL. Figure 4 shows that there is good coherence between the current error signal (B2 18 MHz) and both the B2 8 MHz (despite using PD1 since PD2 was accidentally left closed during the injection), and B2 6 MHz signals.

We left the interferometer locked on the IR beam and the DRMI nodes in down. 

The planned ISC activity on ITF tuning, carried out by Valentini and Boldrini, went on for the whole shift without particular problems.
Activity still in progress.

Parallel activities:
SGD - IR Alignment to FLT and EQB2 (Capocasa, Guo, Sequino)

DAQ
- EarlyWarning restarted several times.

SBE
13:30 UTC - Berni closed SQB2 Loops (SBE, LC).
14:10 UC - SBE SQB2 vertical position restored.
SQB1 still in air.

This morning we checked again the behavior of PSD1 that is the one with a weird response.

We aligned back the green beam on PSD1 and PSD2.

There was a ghost beam hitting the edge of the PSD1 and performing the scans it was going inside its sensitive area, see photo attached. This ghost beam is the reflection of the PSD that is hitting on the back surface of the diaphragm in front of it that is not coated and that was hitting back the PSD.

We checked the power of this beam. The beam reflected by GM12 and arriving on the PSD1 is ~300uW. The power of the PSD spurious reflection is ~70uW. So the PSD surface is reflecting > 20% of power. Then, the beam back reflected by the diaphragm has a  power too small to be measured with precision by the power meter (~ few uW). So we doubt that the weird behavior of PSD1 could be actually be due to this ghost beam.

We looked for a spare diaphragm to be put on the other side of the support, as it is done for all the diaphragms on the IR path, but we don't have it on site. So we tilted the PSD and the diaphragm in order to have the surious reflection arriving on the diaphragm and the reflection from the diaphragm going outside the PSD. At the moment this ghost beam is hitting on the Faraday Isolator, so we should take care of dumping it.

We performed some scans by hand using the mirror GM12 in horizontal and in vertical and we still noticed that the signal H_norm was not crossing zero.

The noise level of the four pins is also higher than the other PSDs, as shown in the plots attached, where the green beam was not arriving on the PSDs.

We tested also the two PSDs spare we have (between 12h30 and 13h39 CEST).

• PSD already installed: the HOR scan was not crossing zero, VER scan looks correct.
• PSD spare #8: the HOR and VER scans were crossing zero.
• PSD spare #2: the HOR and VER scans were crossing zero.

We blocked the green beam with the shutter on EQB1 and we performed the FFT of the signals of the 4 pins for each PSD. The less noisy is PSD #2, which has the same level of noise PSD2 on SQB2 and SQB2_PSD1 and SQB2_PSD2.

We replace PSD1 with the spare #2.

Then we acquired some data with power on and off on the PSDs:

2021-07-29 12h54m44 UTC    bonnand 'GR Shutter:Close' sent to EQB1_ThorAct
2021-07-29 12h55m22 UTC    bonnand SQB1_LC saved - bonnand: PWR off all PSDs (rev. 208601)
2021-07-29 12h55m25 UTC    bonnand 'Acl:Reload config' sent to SQB1_LC
2021-07-29 12h56m53 UTC    bonnand SQB1_LC saved - bonnand: PWR on all PSDs (rev. 208602)
2021-07-29 12h56m57 UTC    bonnand 'Acl:Reload config' sent to SQB1_LC
2021-07-29 12h59m18 UTC    bonnand 'GR Shutter:Open' sent to EQB1_ThorAct.

Moreover, we noticed that also the PSD3 was more noisy than the others, as shown in the attached plot. in addition, if the PSD3 is with power ON or OFF (with no beam on it), it's response is different, see plots.

We checked again the cabling connection at the level of the PSD and of the outside of the electonic box. We replaced it with PSD #8.

We didn't remove the red paper with the numer of PSD (see photo); we will do it before putting SQB1 back in vacuum. To distinguish previous PSD1 and PSD3: PSD3 is the one with some residual paper on it as shown in the picture.

This morning the vacuum team opened SQB1. We want SQB1 to be in air to help with IR alignment in the filter cavity and to replace the PSDs that were not working properly.

We blocked the bench in the closest position to the nominal set points, that were:

LC_X_set       -650

LC_Y_set       -47.5

LC_Z_set       763

LC_TX_set     102.5

LC_TY_set      640

LC_TZ_set      172

The new positions are (as shown in the first picture):

LC_X_set       -663.5

LC_Y_set       -58

LC_Z_set       711

LC_TX_set     169

LC_TY_set      546

LC_TZ_set      223.

We will use these new positions to align the beams and we will update the nominal set points with these values.

Figure 1. When looking at a lock in dark fringe with the B2 QD2 galvo loop open there was to sharp steps in the beam position (mostly visible in B2 QD2 H norm at 58m01 and 58m15),

Figure 2, 3 and 4 show the B2 camera image before the first step, in between the two step and after the second step. The beam is not actually moving, but changing significantly in shape. In between the two steps it looks like an order 1 mode.

The 12MHz QD2 signal that is available is much less affected by this beam shape change. So in principle it could be a better centering error signal.

Figure 5 compares B2 quadrant centering signal with 300mW in transmission of the arms. Purple is centering with the DC signal and blue with the 12MHz signal. The 12MHz has clearly higher sensing noise (this is to be expected). But also show a much prominent motion peak at 7.5Hz /8.5Hz in H and V,  and 1.5Hz in H. I don't know what these are and if it is a bad or good thing that the 12MHz sees that motion.

On Tuesday we noticed that we didn't have power on the PSDs on SQB2 and on PSD2 on SQB1.

Also checking on SQB2 viewport we saw that the beam was really out of the M12 mirror. Using pocomotors we menaged to realign the beam but without reaching the PSDs 1 and 2.

We saw that the problem was linked to the work on the drift control: moving the M5 and M7 mirrors on EQB1, the alignment of the beam on SQB2 has changed. This is shown in the attached plots, where we see that we have power on the PSDs only when the voltage on M5 and M7 was at zero.

The strategy is to align the PSDs opening the tower once we will be sure about the filter cavity alignment. M5 and M7 don't move a lot to keep the cavity aligned, so once their position is fixed, we will proceed with PSDs alignment again.

The planned activity was compromised due to the earthquakes occurred around 8.15 LT. (see 52694).

From 12.30 UTC we were able to lock of the ITF and try the whole sequence of the lock acquisition several times. We reached the step of CARM zero once at 13.32 UTC, but the ITF unlocked on the way.

We leave the ITF to the afternoon shift which will continue the planned activity.

At the start of the shift I checked the alignment of the green (no manual alignment was needed) and then I locked the ITF in LOCKED_ARMS_IR_ALS.

Then a series of earthquakes in the Alaska region unlocked the ITF, the strongest one (magnitude 8.2, see attached picture) opened many SBE loops,  the NE IP, the NE F7; to avoid further problems I manually opened all the SBE loops and also the NE_LC.

The effect of the earthquake was present until 11:30 UTC (see attached plot 2) and prevented any kind of ISC activities.

The SBE loops have been closed around 10:30 UTC; the SBE SNEB loop was closed thanks to help of Matteo because the horizontal loop was oscillating (SBE expert have been informed).

I fully recovered the NE suspension at 11:40 UTC; I realigned the cavities on the IR and I locked the the arms; I checked again the alignment of the green laser and finally at 12:03 UTC I locked the ITF in  LOCKED_ARMS_IR_ALS.

From that point started the planned ISC activity.

Other parallel activities were on SQB1 which was vented and openend this morning.

Air Conditioning
High temperature in DER; experts verified that it is due to the presence of person in the lab.

After the implemetation of the dithring alignement and the offload of the locking correction to the FCEM invertend pedulum last tuesday, the filter cavity stayed locked the whole night.

It was manually unlocked in the moring due to the commissioning activity.

The lenght correction to the IP reached about -550 um and then it had an inversion arount 4am CET. It is likely to be a thermal drift but it seems there is no correspondence with the temperature sensors.

ITF State: Cavities locked on IR.
ITF Mode: Commissioning.
Quick Summary: IMC and RFC locked; all Suspensions loops closed; all SBEs loops closed with the exception of SQB1 . 
Susp: Sa_NE_F7_LVDT_V_50Hz out of range (plot attached)
Activities ongoing since this morning: venting of SQB1.

The goal of the shift was to study and improve the robustness of the ITF lock ad carm offset null, by studying the effects diff+ drift control, PR AA loop, UGF servos and eventually the TCS systems.

During our shift we realigned the green laser in the West arm. The North was also slightly misaligned, not enough to prevent the lock after increasing the reflection DC lock threshold to avoid having it unlocking every few minutes.

We proceeded towards carm null slowly, finely adjusting gains and phases along the way. In particular, we tuned the phase for B2_169MHz in every step of the way (in particular at 300mW and higher powers) in order to strike the best balance between reducing the coupling between PRCL/SRCL and MICH, by minimizing the magnitude of their corresponding UGF monitor lines on the latter error signal.

The first two times we reached carm null, we unlocked for a 70 Hz oscillation on DARM (Fig.1-2, row 2, plots 5-6) that we solved by reducing its gain by a 30% factor, and this problem did not manifest again for the rest of the shift.

We mainly investigated the behaviour of the quadrants used for diff+, B1p_QD2, at carm null. As also noted in the previous shift (52679) we noticed that at carm null the quadrants galvo loops start behaving erratically: the B1p QD2 galvos (Fig.3-4, row 4, plots 6-7) sometime open and the shutter closes as soon as there is any power spike in B1p. At the same time, the B2 QD2 quadrant used for PR AA galvo corrections perform a large jump (Fig.3-4, row 5, plots 1-2). Simultaneous jumps can be observed on the camera position of B2 (Fig.3-4, row 5, plots 4-5). Fig.7 shows these in detail, in particular that the jumps on the galvos loops happen exactly when one goes to carm null.

We decided to keep the diff+ closed up to 300mW, where we open it and let it be. Since the PR AA loop error signals degrade at carm null (see fig 4), possibly due the jumps observed on the B2 beam, we decided to keep it in drift control (Fig.5, row 4, plots 2-3) at carm null.

Furthermore, we noticed that DARM UGF drops significantly after reaching carm null, therefore we enabled the UGF servos for PRCL, MICH and DARM with target UGFs 45, 15, 40 respectively.

These interventions all togheter allowed for a lock in carm null marginally more stable than usual, lasting 5 minutes (last lock in Fig.8). For this last attempt, we also tuned the phase of B2_169MHz in carm null (Figs.9-10). As one can see in the picture, minimizing PRCL line on I significantly increases SRCL contribution. We chose to prioritize minimizing PRCL coupling with MICH.

We leave the arms locked on the IR.

The shift was dedicated as a continuation of the planned ISC activity, carried out by Boldrini and Valentini. The shift proceeded without major issues. 
Other activities carried out during the shift:

• SGD - Green Locking/Alignment optimization (Guo, Capocasa).

ISC activity concluded at 21:10 UTC, infrared cavities left locked.

SBE
At 18:47 UTC the vertical loop of SWEB opened. At 18:48 UTC I opened and closed the related Position Loop to restore the standard condition.

At 22:13 CEST I open LC and SBE control of SQB1.

At 19:06 CEST I reduced the SC power to 1.40mW by rotating th HW before the SC box Output

At the beginning of the shift we experienced some troubles with the North ALS, which was continuously unlocking with no apparent reason (no visible glitches, the alignment and both the signals in transmission and reflection were good). Increasing the gain from 1.2 to 1.5 the issue seemed to be solved.

After this we have tuned the FmodErr signal changing the frequency of the sidebands (no need of MC F0 z position motion). Consider that in order to measure the correct FmodErr the 8MHz has to be brougth back to 15dB using the following command:

cm_send('Lnfs100','SET8AMPL',15) 

remember to bring it back to 0.

At ~8.40 UTC we were able to start the planned ativity.

For the whole shift, the lock acquisition was characterized by the presence of a ~10 Hz oscillation appearing on the way up to 200 mW of arms power, which rapidly killed the lock.  At 200 Hz a huge SRCL line was visible on B2_169MHz_I (MICH-SRCL coupling), so adjusting the demodulation phase at this working point helped to keep the lock more stable. The phase value was good at the initial DRMI lock acquistition stage, but from 200 mW up to higher powers was not good anymore and it has been tuned, see Figure 1.

During the shift we were able to reach CARM offset ZERO only twice, respectively:

• 8.50 UTC: DAS switched ON at 8.50.48 UTC. Unlock occurred after 2 minutes at 8.52.36 UTC;
• 13.34 UTC: DAS switched ON at 13.35 UTC. Unlock occurred after 2 minutes at 13.37 UTC.

this last lock was killed by a ~0.4 Hz oscillation, probably of angular nature (see Figure 2)

The activity will be continued in the afternoon shift.

The planned ISC activity carried out by Mantovani, Pinto and Casanueva from remote, went on without major problems for the whole shift.
Activity still in progress with aternoon ISC crew.

Parallel activities:
INF - Bridge cranes inspections at CB, MC, NE, WE (Omis firm, Baldocchi) from 06:00 to 08:00 UTC.
INF - ACS - CEB AHU outlet fan new frequency
SGD - Green Locking/Alignment optimization (Guo Capocasa).

DAQ
11:41 UTC - EarlyWarning started after a crash.

DMS
- 08:02 UTC - INF..CEB_PRES_OUT threshold changed under request of Soldani.
- 12:31 UTC - Sa_NE_F7_LVDT_V threshold changed under request of Boschi.

SBE
- 10:13 UTC - Rearm vbias of photodiode SNEB_B7_PD2 of mezzanine SNEB_MezzPD_B7
- 10:13 UTC - Rearm vbias of photodiode SNEB_B8_PD2 of mezzanine SWEB_MezzPD_B8.
- 13:00 UTC - Vertical position of SQB2 recovered (plot attached).

TCS
13:20 UTC - TCS_WI_CO2_POWER_CH_PICKOFF threshold changed under request of Nardecchia.