Today we worked on the exploration of the angular DOFs working points with the DRMI configuration (arms locked at -3kHz of CARM offset). As set yesterday, the CHRoCC setpoint was 0.43 V.

Preliminarly, we did a few checks:

• from 6:50 to 6:56 UTC we made a scan of the arm cavities in order to check the mismatch of the arms: the results are similar toSaturday's measurements, but there is a slight improvement on both arms: NArm is at ~2.8% while WArm is at 1.35%;
• around 7:20 UTC, we did a minor tuning of the DRMI demodulation phases (both moved by 0.1 rad);
• around 7:57 UTC, we found out that the occasional bursts of noise that lately have been seen in the DRMI configuration were originated in the CARM loop, which had too much gain; we lowered it by 40%, causing the noise to disappear and all the correction signals of the DRMI to be reduced;
• during this first lock of the DRMI (7:52 UTC for reference) the B4 phase camera imagess were pretty circular and symmetric as expected, while the B1p camera images were quite bad; in this working point, as reference, the main figures of merit were: B4_DC = 2.56, B4_12MHz_mag= 0.135; USB and LSB 56 MHz  power respectively 12 and 8.

Then we moved to the topic of the shift, here are the measurements we performed; occasionally, we relocked from scratch in order to recover the pre-alignment of the arms:

• we started with a wide scan of the PR transversal position, first on the Y direction (starting at 8:06 UTC for the positive direction, 8:19 UTC for the negative one); at the very last step of the negative scan the DRMI unlocked;
• at 8:32 UTC we started the scan on PR_X (positive direction), while at 8:48 UTC the scan was performed in the negative direction; also in this case, at the very end of the latter the DRMI unlocked;
• at 09:01:30 UTC we started the scan of the PR angular working point (on TX; TY started at 9:14 UTC): given that we have a full bandwidth loop for this DOF, we scanned the loop's setpoints, looking at the usual 2D plots; here we focused on the maximization of the B4_12MHz_mag signal, and we used the setpoints we found here onwards;  at this point (9.23 UTC) the superposition of 56MHz LSB and USB powers were respectively 8 and 14;
• at 10:18:30 UTC, after a full pre-alignment we relocked the DRMI locked; the superposition of 56MHz LSB and USB powers were respectively 8 and 13;
• at 10:30 UTC we opened the BS drift control and started the scan on the TX DOF, positive direction, with the local controls;
• we relocked the DRMI from scratch at 12:14 UTC; here the 56MHz LSB and USB powers were respectively 6 and 11;
• we started the scan on BS_TX negative direction at 12:19 UTC;
• at 13:07 UTC we relocked the arms in order to realign, then we relocked the DRMI; the 56MHz LSB and USB powers were respectively 6 and 12;
• we started the scan of BS_TY (positive) at 13:11 UTC, and BS_TY (negative) at 13:42 UTC; in both cases, after reaching a misaglinment of (-) 0.9 urad we witnessed the start of an oscillation on several signals, so we did not move any further;
• at 14:03:25 UTC we unlocked in order to realign the arms;
• finally, we scanned the SR DOFs using the local controls: at 14:23 UTC we started the scan on TX positive, then at 14:49 UTC TX negative; TY positive and negative scans started respectively at 14:59:26 and 15:18 UTC.

Figures:

• 1) mismatch measurement;
• 2) to 5): scan of PR_F7_Y, phase camera images before the scan, after positive scan and negative scan respectively;
• 6) to 8): scan of PR_F0_X, phase camera images after positive scan and negative scan respectively;
• 9) to 11): scan of PR angular DOFs, and 2D plots;
• 12) to 15); scan of BS local controls, TX positive and negative, TY positive and negative respectively;
• 16) and 17): scan of SR local controls, TX and TY respectively.

Data will be analyzed offline, here just a preliminary comment: there doesn't seem to be a strong evidence about a preferred alignment position different from the standard, as basically all the figures of merit seem to degrade (sidebands and DC powers, dark fringe, PC overlap signals); more attention should be devoted to the study of SR, as the results for its DOFs are less clear, and the interaction with the BS drift control (which moved the mirror during the SR scans) should be studied more.

After the restore of yesterday the Automation worked well up to 6:15 UTC of this morning. Here the cavity unlocked and was not more able to relock again (fig1) . We did the following observation:

• after the unlock the system fall in down and discharged the correction of all the mirrirs (FCIM, FCEM GR_M5 and GR_M7) but some kicks to the mirror occured. After that the transmission was at 4V maximum (fig2)
• the threshold for the lock was set at 6.2 V thus the system did not relock on green anymore
• sometimes after the lock on green we noticed a lot of frequency noise and the BPC2 based on dither lines on FCIM and FCEM did not work well. 

To solve it we are implementing the following solutions:

• increase the SQZ_CC_Ctrl GAIN from 0.12 to 0.5 to reduce frequency noise (temorary bug fixing)
• lower the threshold for engage the lock on green from 6.2 to 5 i.e. the 75% of the maximum transmission
• insert in the green+IR locking a state to re-align the green if the transmission is too low, because in that condition it is difficult to find the IR
• try to discharge the mirrors correction without sending kicks to the actuators. A possible solution is tested (fig 3).

We are impementing these upgrades in the SQZ_FLT.py code and tomorrow we will test them. 

Note that other unlocks were triggered by other issues in the automation. These kind of unlocks was less critical thus we started from the bigger problem

There is a mistake in the text of this entry, the top graph of the first attached figure shows the power towards the IMC cavity, not the transmission of the Mode Cleaner.

We analyzed the throughput losses of the Mode Cleaner before and after the CHRoCC installation in PR and SR towers.

- BEFORE CHRoCC INSTALLATION

The 1st and 2nd attached figures show the trend for the period of May 6th 2022 to July 16th 2022.

In the first figure we can see three graphs: the top graphs shows the power in the output of EIB, that is, the power in the input of the IMC. The middle graph shows the PSL to INJ throughput, i.e.m the ratio between the calculated power at the output of the PMC (we have estimated 7% losses from the output of the PMC to the output of EIB) and the power at the input of the interferometer (which is estimated to be 7.5% less w.r.t the output of the IMC due to SIB1 losses), and bottom graph shows the throughput losses of the Mode Cleaner cavity, i.e., the intracavity losses, which is around 17% for the time window analyzed.

The second figure, on the other hand, shows the mismatch calculated for the same period. The mean value of mismatch is around 8.5%.

- AFTER CHRoCC INSTALLATION

The same plots have been produced for the period of July 23rd 2022 to August 8th 2022, i.e., after the two CHRoCCs installation.

The third plot shows the EIB output power (top graph), PSL to INJ throughput (middle graph) and the IMC throughput losses (bottom graph). Here we can estimate that the throughput losses are around 15.5%, which is 1.5% less w.r.t the value before the CHRoCC installation.

The fourth plot shows the mismatch for this period. As we can see, the mismatch has reached a mean value of around 9.5%, representing an increase of 1% w.r.t the previous value.

This morning the scheduled activity of study of angular d.o.f. on CITF was carried out by Diego and Manuel, the work went on the whole shift without any major problem, this activity is still ongoing...

DET
DET_MAIN switched state to FAST_SHUTTER_DEAD at around 4:28UTC, I restored it back to SHUTTER_CLOSED.

Other
yesterday at 15:08UTC the SQB2 position loop was opened by the guardian, controls properly closed.

This week a few ISC shifts have been allocated to the optimization of alignment in CITF. For the evaluation of alignment quality, a few figures of merit have been identified.

In order to see the 'natural' variation of some figure of merit, two gps have been taken into account:

1343811518  Sat Aug  6 08:58:20 2022

1343980618  Mon Aug  8 07:56:40 2022

As far as I understand, all the settings should be the same for the two locks, but I could have lost something.

According to fig 1, the lock of Saturday is a bit better: B4_DC and B4_12MHz_mag are higher, B4_112MHz_mag is almost the same, B1p_DC is lower. The information coming from B4 phase camera confirms the impression: the overlap between carrier and sidebands (fig 2) is higher.

A possible variation in the quality of the alignment is monitored by the demodulation of B7_DC and B8_DC at the angular dither lines on ITMs. The signals are shown in fig 3; they refer to pre-alignments occurred 5000 s before the time of the CITF lock. In both the cases, the signals are not too far from zero, but one is better than the other. That is the one of Monday, corresponding to the worse CITF.

This analysis goes together with a much more evident observation: in the last days the figures of merit taken into account here have been dramatically influenced by a fine tuning of TCS actuators. Any undesired variation of those figures of merit, observed from time to time, could be attributed to some undesired variation of the parameters on which the TCS actuators have an impact. For this reason, we have to be careful in using of the same figures of merit for evaluating the quality of the alignment.

I have to correct the sentence:

''Thus, NI CH and RH are centered within 12*12.28/1024*11~2 mm in X and within  33*12.28/1024~4.5 mm in Y.''

in

''Thus, NI CH and RH are centered within 12*12.28/1024*13~2 mm in X and within  33*12.28/1024*13~5 mm in Y.''

I have mistakenly used the HWS-INJ magnification (11) instead of the HWS-DET one (13).

During the activity of friday morning (OMC mode matching), the bench angular setpoints have evolved from 136 to 29 urad in TX , and from 25 to 32 urad in TY. The change in TY seems rather unsignificant, but the change in TX is quite substantial. We see that at the same time the beam spot is moving on the B1p camera. The main effect is a horizontal motion on the camera by 300 um.

Considering the size of the photodiodes (3 mm aperture), a motion of 300 um should not be an issue, but it may still be worth to check the centering of the beam on the photodiodes and the quadrants on SDB2.

Also probably the alignment of the B1s QPD on EDB will have to be checked.

As noticed in the post, the CHRoCC voltage of 0.43V is a really good starting point. As displayed in the VIM pages, the SB power recycling gain for the 6 MHz was ~65 and ~40 for the 56 MHz. It has to be compared to 40 and 20 without the CHRoCC (see VIR-0369A-22 for example)

All the TolmFrameBuilder servers building a frame at 5Hz are now running with  the DAQ_FIFO_DUMP_FREQ    set to 400Hz.

The operations were performed between 2022-08-08-04h26m-UTC and 2022-08-08-04h33m-UTC

The automation worked well up to 14:48 UTC of 7th August, then the filter cavity unlocked and started to lock/unlock up to 15 UTC see Fig1. A detailed entry to this behaviour will follow/

After that we experienced an INJ unlock and the ITF ML set point moved by about 0.3V (see Fig2). After that the PLLs were no more able to lock thus I had to tune the SQZ laser set point to lock the PLL in this working point (new set points in Fig3). Then I realigned the Green beam and the IR beam to the filter cavity and I re engaged the automation at 21:45 UTC see Fig4.

In preparation for tomorrow's activities, the PR CHRoCC setpoint was moved back to V_DAC = 0.43 V at 19:22:00 UTC.

The check of the last movement has been done today afternoon.

With the ITF in down, the NI CH has been switched ON at high power and the minimum OPL coordinates have been compared with the maximum RH OPL ones (see the attached figure).

The results are summarized in the following table:

Thus, NI CH and RH are centered within 12*12.28/1024*11~2 mm in X and within  33*12.28/1024~4.5 mm in Y.

The ITF has been left locked on IR.

The goal of this activity was to check the alignment of the WI CO2 actuators on the WI CP.

The ITF has been put in down, the HWS-INJ acquisition started and the WI CH has been switched ON at high power at  06.55 UTC (WF 21). The CH beam appeared misaligned wrt the RH in both directions as you can see in the first attached figure (see entry 56673 for the WI TM center identification through RH).

Thus, the steering mirror on the CO2 bench has been iteratively moved in different steps to recover the centering of the CO2 beam actuators. 

After different steering mirror movements performed during the morning, the final check has been done with a new HWS-INJ acquisition.

The WI CH has been switched ON again at high power at 12.23 UTC (WF 10). Since the curvature is well visible and the coordinates are stable, it was switched off at 12.34 UTC. To be sure, at 13.12 UTC we switched on again the WI RH @15 W (WF 102) (it was switched off at 14.55 UTC) and the final configuration on the WI is shown in figure 2.

In the following table, the today WI RH and CH coordinates on the WI and their difference are reported.

We can conclude that the WI CH is well aligned wrt the WI center.

Upon arrival I found ITF locked on IR. I easily locked the CITF (LOCKED_ARMS_BEAT_DRMI_1F) making a cross.
After the unlock (?) I tried again but the WEST ALS didn't lock anymore (no flashes on WE_Cam). Probably a reset will need at WE.
At 06:40 UTC the planned TCS activity on RH was carried out from remote by Nardecchia, Taranto started and went on without major problems for the whole shift. 
I unlocked and relocked on IR. During the relock I had to realign NI and WI.

 ITF left unlocked.

No particular operations to report

ITF State: ITF Locked on IR.
ITF Mode: COMMISSIONING
Quick Summary: IMC and RFC locked; all Suspensions loops closed, all SBE loops closed.
Activities ongoing since this morning: No activity ongoing

No DMS Events to report

EnvMoni
Meteo station still down, red flags on DMS

After the activity described in 56672, the WI RH has been switched ON in order to check the centering of the WI CO2 actuators, activity planned for tomorrow.
The ITF has been put in down state, the HWS-INJ acquisition started and WI RH has been switched on @15W at 17.50 UTC and switched OFF at 19.44 UTC. The coordinates of the WI mirror center are summarized in the table below (see also attached figure):  

The ITF has been left locked on the IR.
 

Task of the shift was to continue the Chrocc power tuning while locked on CITF.

At the beginning of the shift the ITF was locked by the operator, after the usual first pre-alignment, he managed to lock the CITF and, for a quick test, it was possible to go on with the subsequent steps of the acquisition up to the step after 480 mW of arms power, then it unlocked during the jump to CARM null 3f. No phase or gain tuning was performed, but some fine tuning will be eventually needed.

At 7.45 UTC we started the planned activity: with the last Chrocc power and DAS settings set by Diana we locked the CITF in 1f signals by putting a positive (+) CARM offset of +3000, in order to perform an arms scan in this working point.

After a minor adjustment of some LSC gain and MICH/SRCL demodulation phase, we started the scan:

8.06.35 UTC: 1st Scan CARM set +38.000 Hz with 60 sec ramp: the scan worked, but rigth after reaching the final offset value the CITF unlocked. So for the subsequent scans, we decided to use a lower offset value, i.e. +35000 Hz.

8.14.00 UTC: 2nd scan +35.000 Hz 60 sec ramp.
8.16.57 UTC: CITF unlocked on the way back to +3000 Hz.

8.47.05 UTC: 3rd scan +35.000 Hz 60 sec ramp. This time the CITF unlocked during the ramp to 35.000 Hz offset.

results of the first two scans are reported respectively in Fig.s 1 and 2.

N.B. in the last lock, while we were in the scan condition (positive offsets) we experienced a general improvement of the figures of merit that we monitor during the lock, e.g. B4 DC reached 2.61 mW; the 12 MHz SB 0.138 mW.
Also the phase cameras on B4 showed a more circular and symmetric shape, while the ones on B1p got quite worse (see Fig.s 3 and 4)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

After these scan tests, we relocked the CITF in the usual working conditions (negative CARM Offset -3000 Hz), in order to start the Chrocc power tuning activity.

Phase cameras image at this instance (9.00 UTC is reported in Fig.5)

At 9.04.16 UTC: Diana made the first movement setting the Chrocc Voltage from 0.43 to 0.36 V.

9.19.00 UTC: we noticed a general worsening trend, as the aforementioned figures of merit were decreasing and the fringe was getting brigther: B4_DC from 2.61 to 2.54 mW; B4_12 to 0.135 from 0.138 mW (see again fig.3). In the meantime, B1p Phase cameras started to get worse a lot (especially the two e UPP and LWR 6 MHz sidebands, see Fig. 6).

9.57.26 UTC: CITF unlock.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

10.53.20 UTC: lock CITF -> 12 MHz 0.09 mW; B4_DC 1.95; B4 phase cameras had a very good circular shape, while B1p cameras kept getting worse (see Fig. 7). During this lock at first the BS was fine aligned by hand to improve the figures of merit, but we immediately noticed that the BS AA didn't engage as the QPDs shutters were closed, so we opened them by hand. The situation sligthly improved.

then at around 12.05 the CITF seemed to almost stabilize with constant figures of merit value, so we started to perform an other set of scans.

However, this last set of scan didn't succed, as everytime we unlocked as we were passing by the 56MHz LWR HOM2 mode, i.e. to the corresponding value of around 21500 Hz of CARM offset. We tried different ramp values, or adjusting MICH gain (as its correction sometimes saturated), but we never went past that value.

For reference the GPS of the scan attempts are the following:

12.05.45 CARM set 35.000 in 60 sec.
12.06.22 unlock CITF

12.12.16 UTC: scan 35000 Hz offset, 300 sec ramp;
12.15.10 unlock CITF at 21500 Hz offset;

12.18.00 UTC: scan 35000 Hz offset, 300 sec ramp;
12.20.57 unlock CITF at 21500 Hz offset;

12.27.59 UTC: scan 35000 Hz offset, 300 sec ramp;
12.30.54 unlock CITF at 21500 Hz offset; MICH correction saturated;

12.36.49 UTC: scan 35000 Hz offset, 300 sec ramp;  (this time with a lower MICH gain)
12.39.45 unlock CITF at 21500 Hz offset; This time MICH correction didn't saturate, but we unlocked anyway.

13.01.12 UTC: scan 35 kHz in 120 sec ramp.

13.02.27 UTC: unlock CITF at 21500 Hz offset;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

After these failed attempts, we relocked the CITF with the usual negative offset (-3000 Hz), in order to explore a new Chrocc power value.

At 13.39 UTC Diana started a Hartman measurement to take a reference.

At 13.47.53 UTC Chrocc Voltage has been set to a higher value: 0.4 V.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

In the following table are reported the different Chrocc settings performed in the past shifts, in terms of Power (W), Voltage (V) and Dioptres, together with the two equations to obtain the conversion from Voltage to Power and to Power to Dioptres.

Chrocc Power:

Dioptres:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

At the end of the shift we performed a scan while locked on beating signals, to evaluate the mismatch percentage. GPS of the scan are:

For the TEM 00 mode: 15.49.10 UTC

For the TEM 02 mode: 15.53.27 UTC.

Results are reported in Fig. 8., where a 3 % of mismatch has been found on North Arm.

We left the ITF locked on the IR, with the Chrocc left to the last voltage setting (i.e. 0.4 V).

Upon arrival I found ITF locked on IR. I locked CITF realigning PR and SR (cross) then, I easily locked ITF up to CARM_NULL_3F at the first attempt.
At 07:00 UTC, the planned ISC activity on – CHRoCC power tuning until CITF lock (Bersanetti, Pinto, Lumaca) started and went on without major problems performing scans with ITF locked at LOCKEDARMS_BEAT_DRMI_1F.
Activity is still in progress.

No particular operations to report.
No DMS Events to report

ITF State: ITF Locked on IR.
ITF Mode: LOCKING
Quick Summary: IMC and RFC locked; all Suspensions loops closed, all SBE loops closed.
Activities ongoing since this morning: No activity ongoing

No DMS Events to report

EnvMoni
METEO station down since yesterday at 1:30 UTC (plot attached), "Esternal, FlatChannel, Wind activity" red flags on DMS.

The goal of the activity was to check the relative position of the NI RH center (i.e. the NI mirror center) and the NI CH center, continuing the activity started in 56633.

In preparation for the shift, at 14:22 UTC the NI DASes were blocked on the bench by flip mirrors and the ITF was realigned on green, after the work performed during the morning shift.

At 16.25 UTC Fabio set the ITF in N arm locked, W arm misaligned.

After checking the HWS DET illumination, at 16.26 UTC an HWS DET acquisition started and at 16.36 UTC the NI RH was switched ON @ 15 W. 

After almost 1 hour the NI RH induced curvature center starts to stabilize: results are shown in table 1 and fig.1. The NI RH was switched OFF at 18.14 UTC.

The NI RH center position changed by around 23 mm along the horizontal direction: it could be justified by the intervention of the morning shift (56654), during which the position of the meniscus lens (through which also the HWS DET SLED beam passed) was changed. It could be worth considering a realignment of HWS DET SLED beam on top of NI TM.

At 20.06 UTC a new HWS DET acquisition was started and at 20.15 UTC the NI CH was switched ON at high power. The induced curvature became immediately evident and soon after the center stabilized: the comparison results between NI CH and RH centers are shown in table 2 and fig.2. At 20.27 UTC the NI CH was switched OFF.

Still a slight mis-centering along horizontal direction was present. I performed an horizontal movement to recover this mis-alignement: it should be checked in a next shift.

At the end of the shift, the NI DASes actuators were switched ON again ( 21.22 UTC), at the powers left from last shift (56650) to compensate for the NI CP cold lens, and the ITF was left locked on IR.

This afternoon shift was dedicated to NI CO2 actuator centering check, the work work was carried out with the north cavity locked and the west misaligned, it went on for the whole shift without any major problem; activity concluded at the end of the shift, we left the cavities locked on the infrared.

Other
at 15:19UTC the SQB1 position control was opened by the guardian; control closed after re adjust of F1 vertical position with stepping motors.

Vacuum
west end LN2 tank extraordinary refill from 15:30UTC to 16:45UTC

We successfully ported PyPllServer to the default cmt-conda environment.

After that, we prepared an automation branch (dev-mb_220805_for_long_run) adjusted to the long test run. With respect to the currently most updated dev-mb branch it contains changes:
- PySQZ_IR is enabled all the time
- LFC_UGF decorator is disabled (verify if this decorator or LOCK_FLAG creates a problem in case of lock at low GR transmission).

In the process we realized that a measurement of the IR AA sensing matrix might be necessary. We made an attempt but due to the presence of strong wind we were not successful. On the other hand we dedicated time to write down the sensing matrix measurement algorithm which you can find beneath.

The automation was started at (useful data since) 1343766188 05 Aug 2022 20:22:50 UTC

IR AA sensing matrix measurement procedure

Prerequisites:

1. Cavity is AOM_LOCKED_IR, (IR_AA is off).
2. Demodulation Phase of the error signals must be correct.
3. Error signal noise below: ?
4. IR Galvos must be ON and OK

Actuators

• EQB2_IR_QD1_RF_11MHz_X
• EQB2_IR_QD1_RF_11MHz_Y
• EQB2_IR_QD2_RF_11MHz_X
• EQB2_IR_QD2_RF_11MHz_Y

Error signals

• EQB1_IR_M3_MT1_X
• EQB1_IR_M3_MT1_Y
• EQB1_IR_M5_MT1_X
• EQB1_IR_M5_MT1_Y

Steps:

1. Put the offset on one actuator (command is in VPM)
2. Wait one second
3. Read average values of all error signals
4. Invert the offset on the actuator
5. Wait one second
6. Read average values of all error signals (detrend?)
7. Calculate the differences between the two readouts and divide by the difference in offsets.
8. Put results to the matrix column.
9. Repeat steps from 1-8 for other three actuators.
10. Invert the measured matrix