ITF found in UPGRADING Mode and North Arm locked. I found SIB2_SBE, FCIM_SBE, and MC_MAR_Z_ON loops open.
At 06:59 UTC I closed SIB2_SBE.
At 07:01 UTC I closed FCIM_SBE.
From 8:21 to 9:08 UTC De Laurentis and Gargiulo went in DET Lab for wafers replacement.
At 10:46 UTC MC_MAR_Z_ON loop closed by Ruggi.
From 13:30 UTC Tringali went to WEB to disconnect microphones of newtonian array.

The power supply Hameg29 network interface was configured in USB. We have configured it in DHCP around 14h00 UTC, and it was then available from the remote control process PCal_PowerSupply.

Yesterday we did calibration activities on the NE PCal.

We first performed the installation of WSV at NE at approximately 8h UTC, switched off the laser and started the installation of WSV on the reflection bench.

ADC channel calibration NE:
- Calibration for the temperature channel 5 ADC 0 (10h10 UTC):
with a multifunction calibrator Time series connected to the input of the follower circuit for the PCAL_NE_WSV_temp channel. Here the list of actions performed:
• Changing the channel gain to 200 and offset to 0. in the SNEB_dbox_rack config
• Signal injection from 0 to -6V with 2V steps with the Time Series
• Computing the calibration coefficient (gain and offset) with a linear regression
• updating the coefficient in the config at approximately 10h30  UTC

- Calibration for the power channel ch6 ADC 0 (10h40 UTC):
with a multifunction calibrator Time series connected to the input of the follower circuit for the PCAL_NE_WSV_DC channel. Here the list of the actions performed:

• Changing the channel gain to 2. and offset to 0. in the SNEB_dbox_rack config

• Signal injection from 0 to -6V with 1V steps with the Time Series

• Computing the calibration coefficient (gain and offset) with a linear regression

• updating the coefficient in the config at approximately 12h00 UTC

You will find attached the linear regression associated to both the temperature and power calibration (see figure 1&2).
Here is the tab summaring the old&new values of the gain and offset:

NE Tx_PD1/2 calibration vs WSV measurement 

• Start of background measurement : 11h30 (UTC) for 1h

• Laser turned on at 1.3W : 13h30 UTC

We will have a first glance at the data around 16h00 UTC to see the quality of this latter. We checked the results at about 16h15 UTC and the values were consistent with what was expected (data were stable all along the measurements), we thus interrupted the measurement and run the analysis scripts from which we extracted the following gains/offsets (see figures 3,4,5)

Here is the command used: python3 photodiode_calibration.py 1449930618 5400 1449919818 3600 NE

NE Rx calibration vs Tx_PD1 photodiode

BACKGROUND START 18 UTC (for 1 hour) (see figure 6)

LASER ON 20.50 

MEASUREMENT START AT 22 UTC (for 8 hours) (see figure 7 for the ratio measurements)

Here is the command used:  python3 Rx_sphere_calibration.py 1449957618 28800 1449943218 3600 NE

(using Tx_PD1 as reference is hard-coded)

Finally, the analysis results are as follows:

• Rx sphere new gain : 0.729448, new offset : -0.002623 (using Tx_PD1)
• Rx sphere old gain :  0.730861 , old offset : -0.002632

On the ADC configuration, we updated only the ADC voltage calibration used for the two WSV channels (temperature and power), but we did not update any gains nor offsets for the Tx_PD1,PD2 or Rx photodiodes: all the values are still as they were during O4, since March 2024.

Figure 1. After 17 hours the temperature transient is still ongoing, this means that there is no point in closing the north arm cryotrap valves on Thursday evening, as the north arm will not have the time to arrive at a steady state my Friday morning. The temperature change is more than one degree Kelvin, this should allow for an estimation of the cooling power the cryotrap. For example assuming that the mirrors are perfect black bodies (which they probably are not so it is an approximation) the power needed to change the temperature by 1.5 degrees is 3.4 Watts.

ITF found in upgrading mode.

At around 15:30 UTC Romain started to work on SDB1 (68396); activity concluded at around 16:30 UTC.

At around 15:37 UTC Antonio closed the WEST valves ( 68398 ).

In parallel the CAL team worked at the Pcal power calibration.

All the activities concluded at 19:00 UTC.

SBE

SIB2 opened many times by the guardian; properly closed.

Today around 15:35 UTC the west arm cryotrap valves (both WI and WE) have been closed, so that the cryotrap stop cooling the west arm mirrors. Beforehand the WI etalon loop was open, its correction was already at zero since 11:00UTC. 

Figure 1 shows the effect, the temperature of WI has clearly started increasing. We will see tomorrow what is the timescale of the warming, once the temperature stabilizes.

The goal is to measure the effect of the cryotrap on the IM/EM radius of curvature. Simulations reported in the Advanced Virgo TDR mention it is 2m. That wouldn't be enough to explain the 7m discrepency measured at Virgo compared to LMA measurements, but maybe the cryotrap effect is larger than expected due to cooling of other parts of the vacuum system than just the cryotrap.

The goal of the measurement was to measure the angular transfer functions from the marionetta to the SDB1 bench (a first attempt was made in https://logbook.virgo-gw.eu/virgo/?r=68232 ).

SDB1 bench angular control closed at 15h34m41 utc.

Noise injection on SDB1 TX started at 15h50m23-UTC.

We adjust the amplitude of the noise at 15h53m50 utc and start collecting some data (FIG.1) for 6 min.

Then we change the shape of the noise to cover some slightly higher frequencies: new data taking starting at 16h03m57-UTC (FIG.2), for 6 min.

We inject a noise in TY starting at 16h12m58-UTC (see FIG.3) but we do not see the effect on the bench LVDT.

After adjusting the shape and amplitude of the noise, we obtain the noise spectrum shown in FIG.4. Collecting data from 16h22m16-UTC, for 6 min.

Report of the shift of December 10th.

Motivations:

Task of the shift was to evaluate the level of the DAC noise of the input marionette, in particular if its contribution to the low-frequency noise budget is somehow limiting or not. In order to derive such information, we worked in Low noise configuration, reallocating the locking actuation from the input marionettes, to the END ones.

Once in this configuration, the idea was to implement an active subtraction filter (gamma) to reduce the coupling among CARM and DARM loops, i.e. the driving amount that from the common CARM actuation, goes into the DARM actuation.
With the aim to reduce enough this noise contribution, we wanted to eventually derive an upper limit of the input actuation noise, having the comparison of two istances in which the input MAR relays were respectively closed and open, i.e. the High power configuration and the low-noise configuration, respectively.

To be noted that all the actions performed in this configuration couldn't be appreciated on Hrec, since there's a possible miscalibration of the END actuators models, which affects the good reconstruction of the sensitivity.

Hence, profiting of good injections on DARM, all the projection have been made towards a reconstructed sensitivity starting from a calibrated DARM in [m], and afterwards in strain.

Recap of the shift:

Once in the configuration reallocated to the END marionette, we performed a noise injection on CARM loop in order to measure the coupling to DARM. Given the hypothesis that the coupling, at least in the region 10-50 Hz can be assumed frequency independent, we implemented a filter which is basically a static gain with value equal to the measured coupling. 

The gamma subtraction filter has been obtained trough the relationship:

Gamma = DARM_corr / CARM_SLOW_corr *(1-OL_darm) / DCP / OL_darm.

where DARM_corr / CARM_SLOW_corr is the TF during the CARM measurement, while OL_darm and DCP are obtained from the model used to calibrate the spectra of DARM.
Those terms are necessary in order to get rid of the fact that during the injection the measured coupling is compensated by the DARM corrector, thus the right coupling is obtained by opening its loop.
As shown in fig.1 the initial coupling with DARM was of about 3%, after the implementation of the subtraction filter, the coupling was reduced of about a factor 10 at 20 Hz. This result is confiremed by looking at fig.s 2 and 3 where CARM_slow loop projections towards DARM, before and after the implementation of the subtraction filter, are shown.

At this point, we were in a sufficient clean condition that allowed us to perform the main activity of the shift, which was the derivation of the level of the DAC noise of the IN marionette, to verify that the estimated noise is in accordance to the known models used to produce the LF noise budgets.

In order to obtain a direct measure of the DAC noise level, we proceeded by opening the relais of the input marionette. After this action, a slight improvement of the reconstructed calibrated sensitivity has been observed (see fig.4). This improvement could be 'reproduced' if we made the hypothesis that the sensitivity curve with the high-power configuration is equal to the quadratic sum of the known DAC model and the sensitivity curve with the low-noise configuration. If we made this approximation, we obtain one similar response (fig.5). This reconstruction doesn't give a precise value of the DAC level of the marionette, but at least tells us that the known model can be assumed as an upper limit, confirming that we are not underestimating the DAC contribution to the LF noise budget.

list of useful GPS:

gps1=1449415808;dur1=300;%CLEAN; CARM subtracted; DAC ON
gps2=1449417098;dur2=300;%CLEAN; CARM subtracted; DAC OFF
gps3=1449406448;dur3=200;%CLEAN; CARM coupled
gps4=1449402128;dur4=400;%NOISE; CARM coupled
gps5=1449415008;dur5=400;%NOISE; CARM subtracted
gps6=1449418948;dur6=160;%injection on DARM

Figure 1. Following the decrease in RH power the arm power increased by about 2%, peaking around 14:00 UTC. Shortly after the interferometer unlocked and then relocked with the power in the arms decreasing. This indicates that a better mode matching by ~2% is possible, and it corresponds to flatter end mirrors.

Figure 2. Shows in purple the position of the order 2 mode in the arm FSR before the RH change, and in blue at 14:00 UTC close to the peak in the arm circulating power. The mode is at 10.9kHz-11.1kHz when the power in the arms is maximum,  this looks similar to the previous test in June of common RH change when the power in the arms was maximum for 11.15kHz,  https://logbook.virgo-gw.eu/virgo/?r=67078

Figure 3 shows the position of the order 4 mode, it moves from 21.6kHz to 22.3kHz. Note that the position of the 56MHz sideband (assuming 56436993Hz frequency) is at 22.36kHz (assuming an arm FSR of 49'969Hz based on the O4 OptChar paper), so the change in EM RoC makes the order 4 mode and one of the 56MHz sidebands overlap.

Figure 4 shows the position of the orde 5 mode. It is not clearly visible before the RH change, and it is clearly at 27.6kHz at the peak of arm power. For the other 56MHz sideband (upper or lower) the peak in the arm FSR is at 27.60kHz, exactly the same frequency.

In conclusion the change in EM RoC increases the power circulating in the arms, but it also corresponds to making the 56MHz USB and LSB co-resonant with the order 4 and order 5 modes. So just changing the EM RoC doesn't seem like a good solution to improve mode matching, and the input beam needs to be change to modify the beam radius at the level of the input mirror, which requires acting on two actuators of the input beam. However, it is much simpler, and it doesn't seem like it creates any real problems to have the sidebands overlapping with the carrrier HOM.

SBE

SIB2 vertical position recovered with step motors at around 13:00UTC.

Around 14h UTC, we brought the NE PCal Rx sphere to WE and connected it at the place of the WE Rx sphere (changing only the sphere with its preamplifier, not changing any cables). It confirmed that the extra-noise seen on the NE Rx sphere comes from the sphere electronics itself.

The figure shows, with the laser switched off:

• in purple the noise levels of the standard WE PCal sensors : no extra-noise.
• in blue the noise levels with the NE Rx sphere at the place of WE Rx sphere: there is clearly higher noise, which has the same shape and level as the noise level usually seen on the NE PCal with laser off (see figure of 68337).

--> We will bring back the NE Rx sphere to LAPP for further investigations.

For reference, the figure 2 shows the WE Pcal sensor noise levels: 

• in purple with laser off,
• in blue with laser at 1.3 W (Tx_PD1 in loop), with injected lines around 9, 35 and 995 Hz.

This morning, I performed noise injections on the PMC PZT with the BPC loop open to better calibrate the PZT induced jitter noise observed in our previous noise injection measurements.

9:19:05 UTC line at 270 Hz anplitude 1 => lines and harmonics
9:23:50 UTC line at 123 Hz amplitude 1 => lines and harmonics
9:24:51 UTC line at 123 Hz amplitude 1e-3 => can not be seen in the BPC signals 
9:23:50 UTC line at 123 Hz amplitude 1e-2 => figures attached 

This morning, we fixed the issue with NE_Tx_PD1. Two cables was loose inside two banana connectors plugged on the power supply (channel 2, +12V,  and on the gnd cable between ch1 and ch2). After fixing them, the signal from the photodiode looked again ok.

In the Automation we made the following modifications:

•  INJ_MAIN.py line #187 to set IMC_line to 0 when INJ state is DOWN
•  INJ_MAIN.py line #455-456 to set IMC_line to the defined amplitude when INJ state is IMC_RESTORED
•  INJ_MAIN.ini line #9 to set the amplitude of the line (we fixed it to 0.03)

Then we measured the IMC OLTF with the network analyzer and we changed the gain of the loop. The monitor is in good agreement to what we measured (see attached plot).

The  IMC UGF monitoring, based on a line demodulation on the INJ_IMC_REFL_I_{PRE,POST} channels, has been setup

• the INJ_IMC_REFL_I_{PRE,POST} readout is done on the EER_DBOX2_ADC3 Adc2378 mezzanine . These channels are acquired at 20KHz and ar 1MHz
  • the channels acquired at 1MHz  were previously sent to the SUSP_rtpc using the  EER_DBOX2_ADC3_1 Tolm packet at 50KHz.  The EER_DBOX2_ADC3_1 Tolm packet has been removed from the SUSP_Fb 's expect_producer list 
  • these channels are now sent to the SSFS_rtpc using the  EER_DBOX2_ADC3_1 Tolm packet . The EER_DBOX2_ADC3_1 Tolm packet has been added to the SSFS_Fb's expect_producer list 
• at the SSFS_rtpc level 
  • the EER_DBOX2_ADC3_1 Tolm packet has been added to the TOLM_PROCESSOR_INPUT_PACKETS list 
  • The SSFS_Ctrl server configuration has been updated
    • to generate the IMC_line at 97400Hz :  ACL_SINELINE_CH                IMC_line            "V"    SSFS_DSP_FREQ    IMC_LINE_FREQ    0  (SSFS_Ctrl.cfg-line 211)
    • the IMC line is sent using the noise_driving channel:
      •  ACL_SUM_CH noise_driving   "V" 1 0 "noise_dsp" 0 "SSFS_line_LF" 0 "IMC_line" 1 "DigitalNoise_corr"  (SSFS_Ctrl.cfg-line 225)
      • Im the VPM interface, a button related to the noise driving part called "IMC UGF line" allows to set the amplitude of the IMC line
    • to add the  IMC UGF computation part  (SSFS_Ctrl.cfg-line 280 - 298) :
      • the UGF monitoring in the one used for the LSC UGFs monitoring.
      • The 2 filters called IMC_UGF_DEMOD_flt and IMC_UGF_AVG_flt used by the UGF computation are available in  SSFS_filter.cfg 
      • The output channels, sampled at 1Hz, are  INJ_IMC_LINE_COH,   INJ_IMC_LINE_OLTF INJ_IMC_LINE_TAN_PHI  INJ_IMC_UGF  (see the IMC_UGF trend plot , IMC_line FFT plot )
• operations performed  between 2025-12-16-07h15m31-UTC and 2025-12-16-08h34m04-UTC

The last plot show the trend of the different rtpc21 (SSFS_rtpc) monitoring channels after IMC UGF monitoring installation .

At the end,  the IMC_line has been left with an amplitude of 5e-2. But in the configuration file, by defaut, the amplitude is set to 0 . 

It remains to automate the injection of IMC_line either from the INJ_MAIN or ITF_MAIN nodes.

ITF found in UPGRADING Mode.
Ongoing activities on the ITF:
- FCEM payload measurements, concluded at 13:12 UTC (Guo, Vacatello);
- Arm FSR scan without RH, concluded at 16:10 UTC (Jacquet, see #68385);
At 16:10 ITF put in LOCKED_ARMS_IR using ARMS_LOCK node.
ITF Left in UPGRADING Mode with arms locked on the IR.

Motivation for the shift

During this shift, several arm scans are made in order to characterize the optical properties of the North and West cavity. The scan will be used in order to:

-> Measure the astigmatism amplitude. From previous measurement (66835), the astigmatism amplitude appeared to be smaller in the North arm when the ring heater is turned off. No measurement has been made for the West arm since the RH were turned off during the change of the WE mirror. The data from this shift will be used to redo the measurement in both arms.

-> Discrepancy between the characterization made at LMA and from scan (VIR-0562A-25). According to previous measurement, there is a discrepancy between the expected g-factor and what is measured from the scan. The estimation will be done again and for both arms.

-> Most of the scans are made with a misalignment of the end mirrors in order to measure the orientation of astigmatism.

Shift report

Date of the shift : 15th December 2025

The table below shows the tasks performed and their time in UTC. The scans are run with the command CARM_SET_scan_FSR(numiteration = 10, f_FSR=110000,timescan = 60.), where one iteration corresponds to one descending ramp + one ascending ramp. One iteration produces two scans, each one is 60 seconds long.

ITF found in upgrading; see entries 68378 , 68374 , 68379

At the beginning of the shift the Arms FSR scan activity could not be performed bacause the arms valves were closed.

At 8:27 UTC Antonio opened the arms valves; no flashes present in the arms. I was able to find the flashes by looking at the NI,WI,BS mirror positions and finally the cavities were locked at 9:20 UTC.

At around 9:00 UTC Ettore entered in the SR tower, see Weight checks meant to stray light baffle substitution.

At around 10:30 UTC Jacquet started to perform the Arms FSR scan without RH; activity still in progress.

Software

At 8:08 UTC BacnetServer restarted because it was providing flat signals.

SBE

At 8:16 UTC I closed the SNEB position loop; SNEB loop closed again at 9:30 UTC and vertical position recovered with stepper motors.

Venting of SR tower is in progress

• 12h30LT BS/SR and DT/SR valves closed and SR tower isolated;
• 13h15LT venting started;
• arms valved off

Note: G21 / SR link to be replaced during the shutdown

ITF found relocking in COMMISSIONING mode.
At ~17:30 UTC D. Lumaca switched OFF NE, WE and SR RH.

At 17:58 UTC, under request of Gouaty, I performed the following actions:
- SDB2_LC: Open Angular Loop
- SDB2_SBE: Open Position Loop
- SDB1_LC : Open Angular Loop 

At 18:09 UTC, according with the planning of SR intervention, I opened SR loops: LC, F7, ID.

ITF left in LOCKED_ARMS_IR arms. Manually locked via ARMS_LOCK; although ITF state appears DOWN on ITF Event Monitor and DMS.
DET_MAIN, DRMI_LOCK, ITF_LOCK in PAUSE, in UPGRADING mode.

In view of the opening of the SR tower, I setup the automation in the following way:

• DET_MAIN in SHUTTER_CLOSED, then paused;
• SUS_SR in MISALIGNED, then paused;
• DRMI_LOCK in MISALIGNED_PR_SR, then paused;
• ITF_LOCK in DOWN, then paused;
• SUS_PR in MISALIGNED, then manual;
• OMC_LOCK in TEMP_CONTROLLED, then manual;
• INJ_MAIN in IMC_RESTORED, then manual;
• ARMS_LOCK in LOCKED_ARMS_IR, then manual;
• all other nodes unchanged.

As a consequence, the DMS and in general the webpages will not reflect the status of the interferometer anymore, as it is desumed from the state of ITF_LOCK.

For the following weeks, the nodes INJ_MAIN and ARMS_LOCK should be (almost) the only ones to be operated manually; they will not talk with one another, so people should take care of both:

• INJ_MAIN: unless the FmodErr tuning is really needed, IMC_RESTORED is the target state

• ARMS_LOCK: nothing above LOCKED_BEATING_BOOST_ON should be requested