Yesterday I replaced the beamsplitter of the homodyne detector. The new BS is coated by LaserOptik. I tested with a power meter and verified that, with S polarisation, the incidence angle can be tuned around 45° across the 50/50 splitting ratio. Losses are lower than the measurement precision, i.e. well below a few parts per thousand. Fine alignment of the HD is still to be completed after the replacement.

In the recent days we realized that the Green AOM was not configured in double pass. In the morning shift Martina re-configured it in order to have a double pass configuration (see dedicated entry)

Green Alignment:

At the beginning of the shift the cavity was misaligned and the peaks were very low (1.5V). We managed to align the cavity but the peaks were maximum 4.5 V.  Observing the beam shape into the cameras we realized that one of the 2 diaphragram into the green pass was closed. We opened it. The peaks raised at 6 V but the signal for the PDH loop was too low. We realized that the photodiode was misaligned and we realigned it. After that we were able to lock the cavity and we tuned the demodulation phase.  In the new configuration the maximum power transimtted by the filter cavity is 6.7V and no more 7.1V.

IR Recovery:

Observing the two cameras on SQB1 we saw that the SQB1 FI transmitted beam was clipped. Moving SQB1 M21 by about 100 steps in H and in V we recovered it. 

We tried to find the TEM00 of the IR in transmission to the cavity but we did not manage to obtain it. We realized that the work on the AOM changed the IR/Green Coresonance into the cavity thus with a scan we found the BAB TEM00 with the AOM offset around 0.8V.

We improved the alignment of the BAB acting on the EQB1 IR Mirrors (M3 and M5). In tranmission from the cavity we have about 0.16V of BAB

Thwn we switched on the subcarrier beam, we found the TEM00 and we improve a little bit its alignment using SC_M1 and SC_M3. The alignment of the SC is not optimal. It is better to run the SC AA (to do it we need to decrease the SC power. We will do it next week).

SQB1 and FCEM SBE recovery:

In the last days the offload caused the saturation of the FCEM_SBE actuators. With the help of Matteo we discharged the filter cavity offload and we recentered the inverted pendulum.

We recentered also the SQB1 inverted pendulum. Now all the corrections of the Suspended benches are low. Thus we can try to have a long lock during the week end.

IR/SC Frequency study:

After the relock of the cavity we found the BAB TEM00 at 0.8030 V of AOM offset, whereas the SC TEM00 was at 0.9305 V of AOM offset. We moved the SC PLL offset in order to have them corensonant into the filter cavity. The initial offset of SC was 100.10057467 MHz, whereas the offset used to obtain the coresonance was 100.09427962 MHz. Thus the AOM scan frequency slope is 49.37 kHz/V. Before the intervention on the AOM was 25 kHz/V. This confirm that now we are in double pass configuration.

As second step we went into the DET e room and we moved the offset of the AOM frequency generator in order to have back the Green/IR coresonance around 0V. The initial frequency was 80.05370 MHz, now the frequency is 80.01433 MHz. From this we confirm again that the AOM frequency slope is 50 kHz/V. Now the ramp range should be enough to scan a big fraction of a free spectral range. In particular we are able to see TEM00, TEM10 and TEM20 without unlock the cavity as before.

At the end of this analysis we fond that the SC was no more perfectly co-resonant with the BAB. We moved again it PLL offset to 100.09417962 MHz.

With the double pass the Green/IR coresonant is less stable, thus we need to refine oftenly the AOM offset.

Green Lock trigger:

We worked on the lock trigger of the FC on the green beam in order to lock in the green peak corresponding to the IR peak. To do this in the LFC_Acl process we set the thresholds of the SC_PD_DC_CND realy and we added it into the lock filter reset condition. 

We tested it but it is not working well. In particular if the AOM offset is not perfectly tuned the cavity does not lock anymore on the green beam. Moreover if we leave the cavity unlocked for more than 5 minutes the misaligment degradates the IR/Green coresonance and the trigger does not work anymore.

We disabled it by focing the relay to stay alwais at 1.

Green EOM modulation frequency back:

• From 22:17:30 UTC  stretch of data with the GR EOM frequency set to 5.52947075MHz
• From 22:34:30 UTC stretch of data wih the GR EOM frequency set to 5.52942697MHz (wrong demod phase 0.1 rad)
• From 22:47:30 UTC stretch of data wih the GR EOM frequency set to 5.52942697MHz (right demod phase 0.22 rad)

During this test the cavity was locked on green, the IR was resonant and the SC was on. 

Week end data acquisition:

Before leaving I saved all the AA mirror set points in the various configuration files.

We leave the system in the following way

• Green EOM freuquency restored at the initial value
• AOM scan between -0.04 and 0.08V at 0.1Hz
• BAB and SC distance of about 1 kHz SC PLL offset: 100.09517963 MHz

The AOM ramp was switched on at 23:01 UTC

Data will be analyzed

The shift was dedicated to the planned Computing activity, Virgo environment upgrade, carried out by Carbognani and Poulton. The work started at 13:55 UTC and, under the request of the crew, from 15:45 UTC to 19:40 UTC ARMS_LOCK was set in DOWN to avoid possible issues with the ITF. The infrared and green cavities were locked again at 19:47 UTC after a brief alignment.
Activity concluded at 21:20 UTC; as agreed with the Commissioning crew ARMS_LOCK was left in LOCKED_ARMS_IR_ALS in order to allow the automatic relock of the green cavities during the weekend.

Other activities carried out during the shift:

• SQZ Filter cavity alignment recovery and locking tests (carried out by Vardaro), still in progress;
• NEB and WEB temporary unplug and displacement of some NN sensors (see entry #53268).

DAQ
At 17:51 UTC the rtpc10 became unavailable; this issue seems also to prevent further actions using the VPM. Thanks to the remote intervention of Masserot the rtpc was rebooted at 18:11 UTC and the VPM commands were available again.

In this afternoon shift we attempted to put in operation the IGWN based users environment by activating igwn-py39. While working we realized that a full activation would imply strong impact on CMT based C/C++ compilations in Cascina so we preferred to postpone a full activation to a later stage.

We also encountered strange problems while working directly with the igwn-py39 so we preferred to proceed in using the igwn-py39-testing one on which all our previous tests were made. Further checks will be done in parallel, and after today work, the eventual swap to igwn-py39 will be trivial.

What we have done is a partial migration by basically sobstituting the python3 coming from anaconda with the igwn-py39-testing one and by making avalable all Virgo and Ligo software installed under the igwn-py39-testing bin area via the $PATH mechanism.

The testing sequence has been as follow:

1. Put ITF to DOWN

2. Stop all running phyton3 based applications from VPM:

   • All Python based slow control processes (See list from Fig. 1, 2)
   • All Tango -> DAQ bridges (See list from Fig. 3)

3. Modify the bashr_virgo to set the new PATH configuration and add the following new env variables needed by the conda installed version of PythonVirgoTools:

   • LEAP_FILE=/virgoData/LeapSeconds/leap-seconds.list

   • CHANNEL_PREFIX="V1:"

   • FFLPATH="/virgoData/ffl"

4. Modify the local igwn-py39-testing env by adding the following packages needed by the mentioned applications this way:

   • pip3 install pymodbus

   • pip3 install pyusb

   • conda install -c tango-controls tango

   • conda install -c tango-controls pytango

   • copied over: cp /virgoApp/pyserver/v1r0/scripts/tangodata.py /cvmfs/oasis.opensciencegrid.org/ligo/sw/conda/envs/igwn-py39-testing/lib/python3.9/site-packages/  (this need to be fixed at pyserver package level)

5. Verify that PyCm/ PyFd/ PythonVirgoTools is correctly setup by:

   1. Running the test suite that comes with the packages

   2. Attempt to read data from an ffl

   3. Connect online to a process and extract its data

6. Stop/restart one automation node (NARM_LOCK) and one PyALP server from VPM to check no impact on python2 based applications

7. Restart all previously running phyton3 based applications and verify they run correctly. For some of them attempt some cm commanding from VPM vas attempted (SNEB_MotSwitch on/off)

8. Have the Operator check that the main python based user GUI were running fine

9. Put the ITF in the further achievable locking state wich went all smooth

In this configuration, users in cascina will be able to access all python3 igwn software, and more in general find all command line igwn applications.

Big care should be taken that the default python(2) installation is still the previous anaconda2 one, that is supporting legacy python2 aplications (such as metatron or PyALP) until they are fully ported to python3. So if a user need to access the igwn python, must explicitly use the python3, ipython3, jupyter3 and pip3 commands.

Next week a truck shall enter the WEB and NEB. To avoid damage to the NN sensors, we have unplugged and displaced those in the line of sight of the large door.

Being it a daisy chain, there is the possibility that also some far sensors are affected by this operation.

In the attached photos the NEB situation, before and after (not yet finished); WEB had a similar work.

the mistuining of the Diffp demodulation phases is evident both in ty and tx @ Carm null. see attached plots

As it is visible from the B4 6MHz I signal the 600mW is more or less equivalent (slightly lower) to the old 480mW step.

The first part of the shift was dedicated to investigate the  degradation of the green signals.

After that started the planned activity on ISC that proceeded without major issues.

Other activities:

- NEB-AHU box stiffening

- TCS chiller BCK replacement

- activities in Det Lab on the SQZ side.

Suspensions

WI IP COIL H1 close to saturation; Valerio has been informed by mail.

SBE

- SBE_FCEM loop found opened. I closed it properly. Then the horizontal actuators 0 and 2 are saturanting (problem present since few days ago, experts already informed).

- at 12:40 SWEB vertical loop opened by the guardian; to close it I had to adjust the vertical position sith step motor.

The goal of the shift was to complete the recovery of the ITF and continue with the tuning of TCS.

At the beginning of the shift we waited for ALS team to complete their intervention on the green laser (53262). The effectiveness of this intervention is yet to be determined by analyzing the data, even if the situation seems to be improved.  We will leave the green locked for the whole weekend.

Two other attempts were interrupted by a failure with the CARM hand-off to the IR signal. We tried the solution proposed in (53253) and opened the drift control of the terminal benches and the problem did not present again, but being it so sporadic we cannot tell whether this solution is making a real difference. This procedure will have to be integrated in automation.

Since we encountered the already observed problems at the various steps of the lock acquisition performed with the goto functions, namely the 55 Hz possibly given by low DARM gain or high PRCL gain (may be the DARM dem phase tuning could be tuned), we decided to change the 480mW step to 600mW step (which is more similar in Hz to what we had before the increase of intracavity power thanks to the RH). The last function before carm null is now called goto_600mW_HP(). No other changes have been made to the functions concerning gains or phases.

The Carm null has been reached without the wait of 5mins at this step (this was done in order to do not have the CARM offset drift fast and in un-controlled way due to the high thermal effects since the CARM error signal is generated by B7 and B8 DC) .

From the behavior of the DIFFp signals a clear mistuning of the demodulation phase was present (expecially on the horizontal direction). The first task that will be indeed done in the next ISC shift will be the DiffP phase tuning.

The glitches on SNEB/SWEB_TX/TY are due to the turning on/off the bench drift control that looks at the IR beam. There is probably something wrong with the logic of the filter resetting. The best would be to replace by the new ACL command ACL_FILTER_CH_LATCH_MEM_CND.

One of the potential culprit for the degradation of the green signals that has been observed these last days could be the Stimulated Brillouin Scattering into the 3 km long fiber. The theorical threshold is about 8 mW. When we installed the fibers the power at the input of the fibers was about 7 mW (entry https://logbook.virgo-gw.eu/virgo/?r=49235) However, reading again the log entries, it seems that at the end of the day the power injected was actually higher ( https://logbook.virgo-gw.eu/virgo/?r=49425)
In theory the power picked off from the LB towards the other subsystems is kept constant and we readjsut it whenener we increase the power of the fiber amplifier. After the slight increase (10%) of Tuesday ( https://logbook.virgo-gw.eu/virgo/?r=53212 ), we did not not adjust the power of the pick off. Moreover after a year of functionning and the different power adjustements on the PSL side, this power may have varied.
This morning we went into the DAQ room to measure the power at the input of the 3 km long telecom fiber. We measured about 12 mW for each fiber.
We added a 90/10 coupler at the input of the splitter box in order to reduce this power. From 26 mW at the input of the splitter box, we went down to 16 mW (extra losses not investigated) and we finally got about 7 mW at the input of the 3 km fibers. 
The 2 W amplifier at north end did not restart by its own, we went there to restart it.
Apart from that both sources restarted without any problem. We will monitor their good functionning during the next days, they may suffer from the power/polarization changes of the seed.
We will also monitor if it has an effect on the glitches.
 

The following report has been submitted to the On-call interface.

On-call events -> Interferometer Sensing & Control

Title: ALS glitches

Author(s): gosselin

Details:

I have been called by Michele Valentini because there were some glitches on the green beam of the west arm. I first tried to understand from remote with him what was happenning but without success. On request of Matteo Tacca I came on site to investigate them.
From

* Note that any files attached to this report are available in the On-call interface.

The following report has been submitted to the On-call interface.

On-call events ->

Title:

Author(s):

Details:

* Note that any files attached to this report are available in the On-call interface.

This morning, the operator contacted TCS experts for an increasing of the temperature of the TCS chiller BCK that reached 30°C.
At 07:40 UTC, me and Marco went in TCS Chiller Room to check the status of the chiller BCK and we discovered that the cooling system was stucked.
We replace the BCK chiller (pict1) with the Spare one (pict2), re level the chiller with ultrapure water, restarted it, waited that everithing worked properly and the temperature stibilized at 19°C (pict3), restarted the process and the comunication with tne bridge.
Situation in standard state at 09:00 UTC.

The old chiller will be repaired asap. TCS experts informed.

Same the 23/09 at 7h05 UT,

Triggered by the difficulty of manually setting and blocking the camera focus, I have made the following mechanical upgrades to the imaging facility in the "Perugia Cleanroom":

• Replaced the contraption holding the camera with a custom plate (thanks to Alessio Buggiani for the quick turnouround on the request), which makes the mounting cleaner and a lot more stable.
• Inserted a Thorlabs L200/M lab jack (borrowed by the 1500W lab; thanks Fiodor) under the tip/tilt stage (removing the big washer that was there to prevent the knobs from hitting the breadboard, and is no longer necessary
• Readjusted the position of the two big vertical posts so that the camera is fairly centered on the sample holder (note that the "vertical" of the camera is ajusted manually, as the transverse post that holds it is free to rotate around its axis)
• centered the illuminating ring, and adjusted its height so as it should be quite similar to what it was before wrt the sample holder (I dind't have a precise reference; it can be further adjusted if needed). On the occasion, I also tried to space apart the posts holding the ring as much as possible, so as to make it easier to access the sample holder.

Beside obtaining a general tide-up and increase in stability, the idea now is to keep the camera focus fixed on the closest position, and adjust the lab jack height to move the position of the sample until it is in focus. NOTE: a 1/8" (or 3 mm) allen key (or even beter and hex driver) is needed to adjust the jack height: we should procure one to keep with the facility.

This modifications should allow for a faster and more precise focusing (please note that the jack seems to have a quite obvious backlash, but it is not a big issue once you get used to it).

Picture of the upgraded setup are attached.

We calibrated the photodiodes Tx_PD1 and Tx_PD2 on the WE PCal injection bench. They calibrated with repect of the "Working standard virgo" integrating sphere (WSV).

The method used to calibrate these photodiodes is the same than the one specified on report 53233.

As shown in figure 2, the ratios WSV/Tx_PD1 and WSV/Tx_PD2 are very stable before 22:30 UT. At 22:30 UT, there is a glich on the X and Y angle of the miror, then the power measured by WSV vary with the Z position of the mirror. (see figure 1) We think it is because the beam is clipped by an aperture after this glitch. Therefore, we used the data recoded beroe this glitch to do the calibration. There is no visible correlation between the ratios and humidity.

The calibration factors has been changed the 23/09 at 20h45 UT.

Tx_PD1: 0.774 -> 0.685 W/V           Tx_PD2: 1.511 -> 0.752 W/V

ITF State: Cavities locked on infrared.
ITF Mode: Commissioning
Quick Summary: IMC and RFC locked; all Suspensions loops closed, all SBEs loops closed with the exception of FCEM horizontal loop, TCS chiller BCK not in standard state.
Activities ongoing since this morning: None.

The shift started with the recovery of the FC alignment.

TEST of the AOM frequency  shift
h 14.55 utc we start to  check on the SC shift after the recovery of the FC alignment
We find that the SC was not overlapped on the BAB of about 0.2 V on the AOM DDS ramp.

To overlapp it with the BAB, we shifted the SC resonance with the OPLL of  5 kHz = 0.5 *(0.2V*50 kHz/V_DDS (f_DDS3= 100.10049977) .
This means that the AOM is not working in double pass, since for each GR frequency interval correspond the half one IR.

BAB MM  characterization

Then we send spent some  time to more inmprove the IR alignment in order to measure the MM again.
We did the it for both the beam BAB and IR

we found  that  for the BAB (AOM driver @ 80.0537 MHz )

• TEM00 @ 0V on DDS ramp, height  .17 V
• TEM01 @ 3.47 V                    .03 V  on the other green FSR (unlock and lock the cavity to jump on it)
• TEM02 @ -3.78 V                  0.0019 V  (20:35:01 utc)

From the all the data collected we can deduce that we have a final mismatch

        MM ~1.5 +/.5 % 

The misalignment at the end of the shift was in any case to big (~17%), in agreement on the fact that  the retroreflected
beam is not well centerd on both the SQB1 on SQB1_Cam0 and Cam1 and on  the EQB1 cams (see attached picuteres)

SC MM characterization

We performed even measurement on the SC MM, knowing that is not perfectly matched on th OP, we expected an higgher MM. We will report inthe next day the result

    MM~0.04/0.8 ~ 5 %

The shift was dedicated in recovering the stability of the 480 mW step of the CARM offset reduction and in investigating the unlocks that affect the West arm ALS since a few days.

ALS glitches:
Most of the shift was affected by random unlocks of the West arm ALS. The unlocks were (except for a few notable exceptions noted in the paragraphs below) related to glitches (similar to the ones affecting the North arm ALS in the past weeks) appearing at different rates. During some parts of the shift (mostly at the beginning and after 19.30 UTC) they  appeared every few minutes or even every several tens of minutes (allowing a couple of CARM offset reduction attempts), while during the period between 16.00 and 19.30 UTC the rate of glitches increased up to a glitch every few seconds, resulting in continuous lock and unlocks of the green beam (see figure 1). The reason of these unlocks is still under investigation by the ALS team.

Other ALS unlocks during the lock acquisition:
During the unlock investigations, the reason a relatively common kind of unlock was discovered. This unlock happens in two possible steps of the lock acquisition: either when engaging the boost filter after the handoff of the arm control from the IR beam to the ALS beams, or later while increasing the power just after the handoff of CARM2MC to the IR beam. During these steps, the power of the transmitted arm IR beam (B7 and B8) goes from below to above 1 mW, and this triggers the enabling of the SNEB and SWEB IR tracking loops, causing a transient in the SNEB/SWEB_LC_TX and SNEB/SWEB_LC_TY that sometimes affects the ALS lock stability, as can be seen in figure 2  and 3 . To avoid unlocks, the tracking loops should be disabled during the lock-acquisition steps that rely on the ALS beams.

Oscillations at 480 mW:
During the few successfull attempts of reaching CARM offset reduction, two different differential oscillations affected the interferometer at the 480 mW of transmitted power step, leading to unlocks. One was the same ~55 Hz oscillation encountered during the morning shift  (53247), related to an increase of UGF that affects the DARM loop after a few tens of seconds of lock in this state (see figure 4). Attempts of manually  or automatically (using the UGF servo) tuning the DARM GAIN in order to keep the UGF under control (around 35 Hz) had mixed results, since lowering too much DARM (below 0.02, from the current 0.025) leads to the appearance of low frequency ~1.8 Hz differential oscillations that equally distrupt the lock.

The interferometer has been left with the arms locked on the IR beam and the other nodes in DOWN.

In order to understand the coresonance of the BAB and SC inside the filter cavity, we did some lock/unlock tests.

First we shifted the SC frequency to have it coresonance with BAB, the we perfomed three time relatively long term lock/unlock. GPS time of the unlocks are listed below. 

start unlock ------- locked on the right FSR 

1316459958 ----- 1316460408

1316460438 ----- 1316461278

1316462058 ----- 1316463138(slowed the scan)

We didn't observe any AOM frequency shift between BAB and SC for the first two unlocks. We checked the transmission IR PD signal sampled at 10kHz. 

But after the 3rd unlock, the resonance of BAB and SC shifted about 0.007V in AOM voltage. (pic 1) There was once PLL unlock during the 3rd unlock.

We also did feel fast lock/unlock, we didn't observe any shift between the BAB and SC. The gps time of the fast lock/unlock listed below

1316466630 ----- 1316366824.  (AOM ramp freq 0.5Hz)

1316466936 ----- 1316467180   (AOM ramp freq 0.1Hz)

This shift was dedicated to go on with ISC activity; in the afternoon we had a lot of problem with the green lock of the west arm preventing to lock the ITF, at some point Matthieu (ALS on-call) came on-site to check the status of the system; the situation get better in the evening without doing anything and Michele started trying to lock the ITF;
starting from 20:30UTC we started to have problem of missing channels from SWEB most probably because of some work on the WE photon calibrator, the missing channels get the ARM_LOCK metatron node stuck preventing to go on with the lock.
The ISC activity stopped at 21:00UTC, we left the cavities locked on the infrared.


other activities:

-SQZ: work on the filter cavity locking;

DAQ
SWEB_Fb crashed and restarted at 20:48UTC.

We checked the data of this night during the misalignment of the cavity. The problem was that the drift control of the FCIM was no more enabled. 

When we tested the drift control for the first time we forgot to save some weight in the configuration file. The process was restarted the 22 september at 10:33 UTC and from this date the drift control at FCIM was open (fig 1). Before this event was ok see fig 2.  We restored it.