Activity concluded at 11:06 UTC.

Zaza, Gherdardini, and Ricci will enterer the Clean Rooms and the base towers for NI Electrical Checks. Dattilo will stay outside Clean Rooms.

Majorana, Pinto will enter in the CEB Clean Rooms and in the NI tower since 08:00 LT.
Puppo and Benedetti will enter only in the CEB Clean Rooms since 8:30 LT.

We left the CEB clean rooms at 18.05 LT.

Last week the motor of one of the 500 KVA diesel generator (GE 1) hosted in the Technical Building and serving the Central Building + Computing room on UPS and Central Building UTAs on IPS was identified as faulty. 

Since it seems that motor repair could be lenghty the immediate solution being pursued at the moment is the renting of an emergency generator to be positioned in the vicinity of the TB that would replace the malfunctioning one and bringing back the standard situation.

This emergency generator has been already shipped onsite (See Fig. 1) and the electrical swap is currently foreseen for tomorrow, Tuesday June 14. The swap itself will not imply IPS interruptions but a test must be done on generator intervention so a ~30 sec ENEL interruption will be simulated.

ITF found DOWN and in UPGRADING Mode.
All times are UTC.
Below the activities comunicated to the Control Room:
07:32 - 10:49 NI payload assembly (Majorana, Pinto).
10:12 - 10:34 RFC Scan (Spinicelli from remote).
12:00 - 12:11 IMC Scan (De Rossi from remote).
12:26 - 12:55 Check of Newtonian Sensor at NEB (Tringali).

We continued to deploy the DAC1955 v3r3 firmware on all the DAC1955 boards use the SQZ system and driven by

• rtpc3 :  the 11 DAC1955 boards have been updated
  • Tolm output data flow is reduced from 37.7MB/s to  12.MB/s

Operations performed between  2026-07-08-11h36m47-UTC and   2026-07-08-15h54m33-UTC

• all the loops were opened during the time of the operations
• we checked that all the DAC1955 Tolm packets are well received by the expected DAC1955  board
• the SQB1 LC loops were successfully closed after the update . The SBE ones were not closed before the upgrade
• The FCEM LC and SBE loops were successfully closed after the update
• The FCIM LC and SBE loops were successfully closed after the update

Below the detailled list of the operations performed

• Use DaqBox v17r11 for SQB2_dbox_bench, SQB2_dbox_rack, FCEM_dbox and FCIM_dbox
• SQB2_LC server : 3 DAC1955 boards
  • SQB2_DAC_PSD                 : DAC1955_SN161 - DBOX_SN108 - SQB2_dbox_bench     : rtpc3
  • SQB2_DAC_LC_LVDT_in    : DAC1955_SN049 - DBOX_SN107 - SQB2_dbox_bench     : rtpc3
  • SQB2_DAC_LC_LVDT_out  : DAC1955_SN150 - DBOX_SN096 - SQB2_dbox_rack        : rtpc3
  • We checked  that the Tolm packects are correctly received by the DAC boards
  • the SQB2_LC loops were successfully closed after the upgrade
• SQB2_SBE and EQB2_QD servers : 2 DAC1955 boards
  •  SQB2_DAC_SBE0             : DAC1955_SN152 -  DBOX_SN095 - SQB2_dbox_rack        : rtpc3
    • SQB2_SBE server    : ch00-ch03 : 4 channels
    • EQB2_QD server      : ch04-ch05 : 2 channels
  • EQB2_DAC_IR_GALVO      : DAC1955_SN122 - DBOX_SN110 - SQB2_dbox_rack        : rtpc3 : all the channels are managed by the EQB2_QD server 
  • We checked  that the Tolm packects are correctly received by the DAC boards
  • It remains to check that the galvo loops are still running correctly
• FCEM_LC and FCEM_SBE servers: 2 DAC1955 boards
  • FCEM_DAC_LC0                 : DAC1955_SN013 - DBOX_SN068 - FCEM_dbox             : rtpc3  : all the channels are managed by the FCEM_LC server 
  • FCEM_DAC_SBE0              : DAC1955_SN127 - DBOX_SN069 - FCEM_dbox             : rtpc3  : shared DAC board
    • FCEM_SBE server : ch00-ch03 : 4 channels
    • FCEM_LC server  : ch04-ch07 : 4 channels
  • We checked  that the Tolm packects are correctly received by the DAC boards
  • The FCEM LC and SBE loops were successfully colsed after the upgrade
• FCIM_LC and FCIM_SBE servers : 2 DAC1955 boards
  • FCIM_DAC_LC0                   : DAC1955_SN143 - DBOX_SN024 - FCIM_dbox              : rtpc3 : all the channels are managed by the FCIM_LC server 
  • FCIM_DAC_SBE0                : DAC1955_SN125 - DBOX_SN073 - FCIM_dbox              : rtpc3  : shared DAC board
    • FCIM_SBE server : ch00-ch03 : 4 channels
    • FCIM_LC server  : ch04-ch07 : 4 channels
  • We checked  that the Tolm packects are correctly received by the DAC boards
  • The FCIM LC and SBE loops were successfully colsed after the upgrade
• Unused DAC1955 boards : 2 boards
  • FCEB_DAC_00                     : DAC1955_SN014 - DBOX_SN045 - FCEM_dbox             : rtpc3 
  • FCIB_DAC_00                      : DAC1955_SN033 - DBOX_SN112 - FCIM_dbox               : rtpc3 

This morning I measured the modulation index of the 6MHz and 56MHz after the work on INJ/ALS started on April.

I started scanning the RFC with the INJ in standalone at ~10.21.30UTC , by moving the MC on F0_Z axis for a 500µm displacement in  500µs , as usual.

The resulting modulation depth for the 6MHz and 56MHz are, respectively,  ~0.19 and ~0.18, which correspond to the usual values.

We continued to deploy the DAC1955 v3r3 firmware on all the DAC1955 boards use the SQZ system and driven by

• the rtpc2 : the 9 DAC1955 boards are updated
  • Tolm output data flow is reduced from 37.7MB/s to  8.4MB/s

Operations performed between 2026-07-08-05h59m01-UTC  and  2026-07-08-09h22m32-UTC

• all the loops were opened during the time of the operations
• we checked that all the DAC1955 Tolm packets are well received by the expected DAC1955  board
• the SQB2 LC and SBE loops were successfully closed after the update

Below the detailled list of the operations performed

• Use DaqBox v17r11 for SQB1_dbox_bench, SQB1_dbox_rack and  EQB_QD_dbox_rack
• SQB1_LC  and SBE servers :  4 DAC1955 boards
  • SQB1_DAC_PSD                : DAC1955_SN120 - DBOX_SN103 -  SQB1_dbox_bench      : rtpc2 
  • SQB1_DAC_LC_LVDT_in   : DAC1955_SN135 - DBOX_SN103 -  SQB1_dbox_bench      : rtpc2 
  • SQB1_DAC_LC_LVDT_out : DAC1955_SN144 - DBOX_SN088 -  SQB1_dbox_rack         : rtpc2
  • SQB1_DAC_SBE0              : DAC1955_SN147 - DBOX_SN087 -  SQB1_dbox_rack         : rtpc2
  •  We checked  that the Tolm packects are correctly received by the DAC boards
  • The  SQB1 LC and the SBE  loops were successfully closed after the upgrade
• SQB1_FI server : 1 DAC1955 board
  • SQB1_DAC_01                   : DAC1955_SN151 - DBOX_SN088 -  SQB1_dbox_rack         : rtpc2
  • We checked  that the Tolm packect is correctly received by the DAC board
• EQB1_QD server : 1 DAC1955 board
  • EQB1_DAC_03                   : DAC1955_SN148 - DBOX_SN091 -  SQB1_dbox_rack        : rtpc2
  • We checked  that the Tolm packects are correctly received by the DAC boards
  • It remains to check that the galvo loops are still running correctly
• EQB1_HD_AA server : 2 DAC1955 boards 
  • EQB1_DAC_01                 : DAC1955_SN149 - DBOX_SN089 -  SQB1_dbox_rack          : rtpc2
  • EQB1_DAC_02                 : DAC1955_SN146 - DBOX_SN091 -  SQB1_dbox_rack          : rtpc2
  • We checked  that the Tolm packects are correctly received by the DAC boards
• EDB_QD_AA and EDB_QD_MM servers : 1  DAC1955 board
  • EDB_DAC3                       : DAC1955_SN119 - DBOX_SN075 -  EDB_dbox_rack            : rtpc2
    • EDB_QD_AA server         : EDB_DAC3             : ch00-ch03 : 4 channels
    • EDB_QD_MM server        : EDB_DAC3             : ch04-ch07 : 4 channels
  • We checked  that the Tolm packect is correctly received by the DAC board
  • It remains to check that the galvo loops are still running correctly

We continued to deploy the DAC1955 v3r3 firmware on all the DAC1955 boards use the SQZ system and driven by

•  the rtpc23 : 1 DAC1955 board  updated
  • Tolm output data flow is reduced from 4.2MB/s to  0.42MB/s  
• the rtpc1: 2 DAC1955  boards updated 
  • The total  Tolm output data flow reduced from 54.5MB/s  to 11MB/s

Operations performed between 2026-07-08-05h14m16-UTC and 2026-07-08-05h44m40-UTC

• all the loops were opened during the time of the operations
• we checked that all the DAC1955 Tolm packets are well received by the expected DAC1955  board

Below the detailled list of the operations performed :

• Use DaqBox  v17r11 for  SQZ_DBOX_DET_EERoom  server 
• SQZ_PLL_AA server :  1 DAC1955 board
  • SQZ_DAC2             : DAC1955_SN032 - DBOX_SN058 - SQZ_DBOX_DET_EERoom  : rtpc23
  • we checked  that the Tolm packect is correctly received by the DAC board
• SQZ_CTRL server : 2 DAC1955 boards
  • SQZ_DAC0             : DAC1955_SN070 - DBOX_SN092 - SQZ_DBOX                            : rtpc1
  • SQZ_DAC1             : DAC1955_SN112 - DBOX_SN093 - SQZ_DBOX                            : rtpc1
  • we checked  that the Tolm packects are correctly received by the DAC boards

We left CEB clean room at 12:50 LT.

Erratum: The mirror used to align the master laser with the SL cavity is LB_M1, not LB_M2. Horizontally, the screw was turned anti-clockwise, and vertical screw was turned clockwise. The final linearity bandwidth after re-alignment is 1.9 MHz, not 1.0 MHz.

The method used to measure the linearity bandwidth of the slave laser is expalined in post 66249.

We are entering again the CEB clean room. 9.30 LT

We left the CEB clean room at 21.00 LT. Tomorrow morning we will continue.

Before measuring the locking bandwidth, the OLTF of the IMC was measured, and a 14° phase margin was measured.

We measure the locking bandwidth, which is the linearity zone between the SL cavlty length and the error signal. Initially, it was measured at 0.9 MHz

After turning the LB_M2 mirror horizonally, we managed to increase the bandwidth up to 1.3 MHz.  After that, we measured the IMC OLTF again, and found a 19° phase marging.

After that, we tried to realign LB_M2 vertically, we managed to reach a 1.0 MHz bandwidth. The UGF of the IMC OLTF was 92kHz with a 23° phase margin. In order to increase the UGF, we diminished to IMC loop attenuator value from 11dB to 9dB, which increase the main gain of the loop. The new UGF is 120kHz with a 20° phase margin. The two plots shows the OLTF of the IMC with the attenuator at 11dB and at 9 dB.

Other subject: In order to stabilize the TY degree of freedom EIB, we moved the the water tubes of IPC1. It improves the TY value and releases a bit the actuator 0.

ITF DOWN in UPGRADING mode.

planned activities communicated to the control room:

• Realignment of Master Laser wrt Slave Laser, OLTF measurements (Gosselin, Lagabbe)
• WI tower baffle installation (Ballester, Erbanni, Francescon, Gherardini)
• EIB step-motor adjustment. EIB - SAS motor control not responding, issue temporarily fixed but if will be addressed again by Bertolini during the next maintenance (Bertolini, Carbognani, Gosselin)
   

Figure 1. The B4 phase camera has an apparent offset in the sideband power measurement when no light and no reference beam is present on the phase camera. The offset is around 25e-6 in the not normalized channels. This offset has been present for at least the past three years, and has been relatively stable over that period.

Figure 2. That offset is comparable to the sideband power in single bounce, especially when the input power is low, as in this example with 11W of input power. The signal of the phase camera for the 6MHz increases only by a factor 2, in the single bounce configuration, compared to the dip in the middle which is at 25e-6 corresponding to no beam arriving on the phase camera. 

If that is a real offset, then in single bounce the power of the sidebands is overestimated by a factor, and the sideband gain is under estimated by a factor 2. It would also affect the measurement of the sideband modulation depth that use single bounce beam data and the ratio between the sideband and the carrier power as measured by the phase camera.

Analyzing data from the reference period at 11W used in the O4 detector paper (VIR-0710G-24), on Dec 10, 2023. The 6MHz modulation depth without compenstating for the offset is 0.21, while by subtracting the offset it becomes 0.15. However, the modulation depth measured simultanously with the B1p camera is 0.19, much closer to the value without subtracting the offset, and the B1p camera is not affected by the offset issue because the power is much higher, so the offset is always negligible compared to the sideband power in single bounce.

Similarly the 56MHz sideband has modulation depth of 0.21 on B4 without correcting for the offset, and 0.14-0.16 after correcting for the offset, while on the B1p phase camer it is 0.19-0.20.

/users/mwas/PC/PC_modulation_depth/SB_mod_depth.m

Figure 3-5 The OMC was scanned a few days later on Dec 19. The carrier TEM00 power is 0.0272 and the 56MHz sideband power is 0.29e-3, which correspond to a modulation depth of sqrt(4*0.29e-3/0.0272) = 0.206, which agrees with the B4 phase camera measuremetn without offset correction. 

It appears that the offset visible in the phase camera does not affect significantly the sideband power measurement despite the offset being equal to half of the sideband power measured value on a single bounce beam.

Looking at the phase camer code and raw data, this offset is likely the average value of numerical noise. 

Figure 6 shows the raw phase camera data at a time when no beam is present, and it is clearly a digital noise with an integer number of counts between 0 and 3. Looking at the computation of the sideband power in /virgoApp/PyALP/v3r0/src/main.py, it is the average value of the square of that channel over one second. 

Figure 7 for comparison shows the same raw data when the interferometer is full locked. This is only available in raw full data so we do not have recent data, but there were some times which have been archived. I did not search the archive extensively, but I do not expect we have archived single bounce raw full data. The power of the sideband in single bounce should be a factor 5e-2*0.5^2/20 smaller, where 5e-2 is the PR transmission, 0.5 the BS reflectivity and 20 the sideband gain, which means the amplitude as measured by the phase camera should be a factor 40 smaller in single bounce than with a full interferometer, corresponding to up to 15 counts. Given that the average is looking at the square of the PC raw channel, mostly the times when the value is large count in the average, and these will be less affected by a digital noise of a few counts around 15, especially if that noise becomes symmetrical once the signal is no longer at the zero rail of the digital output. 

This might be an explanation why the offset is not affecting so much the measurement of the sideband power, but that depends on how that digital noise behaves when there is a small but not zero signal. It will be easier to confirm once we get back a single bounce beam to have access to PC raw data in single bounce.

Luca, Angelo and Fabio are entering the WI tower to install the 'tower baffle'