We starter with the NI.
1) removal of the safety frame at the sides of the payload, they have been located in the underground clean area close to the ITM towers;
2) removal of the HWS mirrors with the related mounts. They have been wrapped and located in the clean area under the detection port, see Fig. 1;
3) we took some pictures and we started noticing that the X stops of the CP were properly set not to touch the plate, Fig 2;
4) we were then about to block the marionette on the cage, in order to start the extraction operation but before touching anything (neither the cage nor the suspended bodies marionette and mirror), we heard a sharp noise. What happened was clear as we saw the vertical stops above the marionette, they were touching, a clear sign of an upwards jump due to fiber breaking. These fibers worked with honor for more than 8 years (Fig. 3)
5) After a crosscheck of the mirror position, quite rotated due to the fact that only two fibers, both on the W side got broken, there was nothing to do than proceeding with the standard maneuvers to extract the payload (Fig 4 and 5).
6) Then the payload, thanks to the valuable efforts of the VAC crew was brought upstairs into the clean room, ans seated on the assembling table.
7) The mounts of the CP and RH were dismounted (Fig. 6)
8) And finally the main mount of the CP, with the CP inside, was separated and set into the clean hood in class 1.
We have re-verified the angular and longitudinal WPs after the work of today.
The new values of the angular WP are close to zero but the horizontal FF. We will investigate the reason for this difference in the following days.
NF H: -0.02
NF V: -0.075
FF H: -0.62
FF V: -0.05
Instead the longitudinal WP remained quite large as measured last week (-1.7V).
Last Thursday a large longitudinal working point offset was observed in the IMC locking loop. In addition, the RF QPD in near field used for IMC alignment did not appear to behave correctly.
Given the significant mode mismatch previously measured (~13%), we redistributed the power by reducing the PMC input by 20% and compensating with IPC1, with the aim of modifying the thermal lens in the EOM and Faraday. Following this change, the mismatch improved to ~9%.
In parallel, a peak at 0.8 Hz was identified in the RF QPD spectra. Maria and Irene performed a Bruco analysis and found coherence with MC TY, suggesting that the feature originates from the AA matrix.
We then optimized the IMC alignment and remeasured the sensing matrix. The 0.8 Hz peak on the horizontal signals was significantly reduced (see comparison plot between Apr 10, this morning before power reduction, and now). However, the longitudinal working point remains large and comparable to last week. Checks of the 22 MHz signal and the RF photodiode after the EOM (EOM_EAB_TRA) do not show any increase in amplitude modulation, leaving this effect unexplained.
To further investigate the mode mismatch, beam profile measurements were performed on EIB after M5 under two thermal conditions: current configuration and with PMC_TRA increased by 20% (as earlier this morning). The goal was to identify possible thermal lensing, including its position and focal length.
Measurements (around 17:17 LT, low PMC power, 29.6 W after EIB M5, IPC1 = -54250 step, ~4.4 mW sampled after M5) :
z from M5 (mm) ellipticity beam width (um)
85 97 1280 um
135 98% 1290
185 100 1380
235 100 1420
285 1470
335 1480 (1530)
After increasing PMC_TRA by 20% (17:24 LT, ~5.3 mW sampled),
85mm 97% 1260
135 98 1305
185 99 1360
235 97 1405
285 96-97 1490
335 98 1520
The measurement sequence ended at 17:37 LT, and the system was returned to low PMC power at 17:44 LT (IPC1 = -51500).
A preliminary analysis of the beam profiles indicates a waist of ~508 µm located at -0.49 mm from M5 in the low-power case, and ~444 µm at the same position in the high-power case (+20%). Using the known waist at the output of the LB (639 µm at 13 cm from EIB), these results can be reproduced by introducing a thermal lens in the third EOM with a focal length of ~1090 mm (low power) and ~900 mm (high power). The variation in focal length is consistent with a linear dependence on absorbed power. Quantitatively, this would correspond to an effective absorption on the order of ~2000 ppm, significantly larger than the expected 50 ppm/cm for a 20 mm crystal.To be followed.
Additional activity :
Realignment and calibration of EIB POUT : 34.5 W on the channel with 0.485 PMC_TRA_DC while 29.6 W have been measured.
We have re-verified the angular and longitudinal WPs after the work of today.
The new values of the angular WP are close to zero but the horizontal FF. We will investigate the reason for this difference in the following days.
NF H: -0.02
NF V: -0.075
FF H: -0.62
FF V: -0.05
Instead the longitudinal WP remained quite large as measured last week (-1.7V).
This afternoon we put in operation the DAC1955 v3r3 firmware for the NCAL WE . After the upgrade; the WEB NCAL loops, frequency and phase, were successfully closed.
Below the details of the operations:
- use DaqBox v17r9 version for the WEB rtpc DaqBox servers
- update the DAC1955 SN53 (DBox SN121) and DAC1955 SN73 (DBox SN 175) firmware qnd DSP code with the v3r3 release
- The DAC1955 chips are now running at 400KHz instead of 100KHz previously, with an analog anti-image filter cut-off unchanged at 20KHz
- update the SWEB_dbox_rack configuration and the WEB_NCal one
- operations complete at 2026-05-04-14h46m00-UTC
ITF found in down and in Upgrading mode.
Below the list of the activities communicatd in control room:
- NI payload intervention; in progress.
- Instrumented baffles installation; in progress.
Cal
At around 11:30 UTC Alain started to work at WE Pcal.
Susp
At 12:34 UTC we had a problem with the DSP BPC board. I contacted Valerio and he fixed the problem performing the download of the code.
SBE
The DMS was reporting that SPRB_SBE vertical correction was close to saturation; I recovered it using the stepper motors.
The spare part has been installed and then the pumpdown was started. The cryotrap is now under high vacuum, and the cooldown is foreseen from next tuesday.
A few more observations concerning the test of April 23:
- at some point, while the AHU was off, we stopped the water flux by closing the valves located inside the CEB AHU room. Unespectly we measured an increased acoustic noise in the range 50 to 100 Hz (Figure 1)
- between 8:49 and 11:13 UTC, while the AHU was off, we closed all air valves of ducts (all set to 0%). In principle we would expect some change in the position of low frequency spectral peaks, if they were associated to acoustic modes of the air ducts. We did not notice any change (Figure 2).
- acoustic spectrograms show some peaks changing frequency, mostly above a few hundred Hz. They seem correlated to the frequency of the SUPPLY fan (Figures 3 and 4). Yet, we then notice that similar ones are present also when the HVAC was running in MANUAL modes (that is when both fans frequency fixed): Figure 5. Could they be associated to the air flow regulators instead?
- IMC alignment and measurement of the new AA sensing matrix
- IMC longitudinal wp. The offset on the IMC PDH error signal appears to be quite large (-1.6 V, see attached plot). However, with this offset the IMC lock is very unstable, so we left the old one -0.07 V. To be understood why the scan gives such large offset (maybe on monday we will check the alignment in the EOM? on the IMC refl photodiode?)
- IMC Fmoderr. We made it with the automation and it was very close to the optimal wp
- IMC angular wp --> we found an issue on the NF V RF quadrant. We did the usual scans of the galvo working points (scanning the offsets of the galvos) and look at the coupling between error signal and frequency noise (TF between perturb at 1111Hz and the Quadrant signal (the demodulated quadrature I). We observed a strange behaviour for te NF V (non linearity: changes slope around the 0). See plots 2 and 3 which compare current scan (30 Apr 13:17:02 UTC) with an old one (10 Apr 2026 10:03:10 UTC): the magnitude doesn't go to zero and the phase behaviour looks strange. We then went in the LL Atrium and unpowered and powered again the NF QPD electronic box and made another scan at utc2gps(2026,04,30,15,05,08) from -0.5 to 0.5 in 300s (plot 6 and 7), which was still bad. To be investigated next week.
- IMC OLTF we found 96 kHz UGF and 30 deg phase margin. We added 1 dB to get 107 kHz and 23 deg phase margin (plot 8)
In the meanwhile we prepared the Acl code ISYS_BPL for the bench pointing loop. We still have to plug the PZTs to the DAC (we need prior to find a solution to block the beam before the EOMs while testing the PZTs, since the risk would be to burn something)
Here attached some pictures of the EIB after the installation.
Since yesterday 12:00 LT (April 29) the DET AHU is running in MANUAL mode (fixed fan frequencies) at slightly reduced rate of the SUPPLY fan (28.5 Hz instead of usual 31.5). Ambient parameters (TE, HU, PRES) look stable enough (see attached) so we decide to keep it in this configuration untill Monday.
ITF in DOWN, UPGRADING
This morning the INJ team worked on beam realignment and RFC locking. The MC valve was opened by the vacuum group.
After the operations in laser lab, hvac pressure system working point was set back to normal and BACnetServer was restarted.
At 12:00 UTC the vacuum group started venting NI tower
- today upgraded versions of the quadrant photodiodes for the bench pointing loop have been installed. In fact yesterday Piernicola and Flavio found out that the excess of noise on the QPD signals was probably due to the length of the cables.
The two QPDs have then been realigned to have DC and asymmetries close to 0 (plot 1) and plot 2 shows the noise of the QPDs without any laser beam.
- In order to close the BPC we had to move the picomotors on M6 and M8 mirrors on EIB. We found that the driver for the M8 tx ty picomotors doesn't work anymore. We temporarly plugged M8 tx and ty on Far M1 ty an tx respectively. We could then close the loop
- we finally struggled to lock the IMC since we had not realized that the valve between SIB1 and MC had been closed (we thought the beam was misaligned instead).
Tomorrow we will continue with the INJ recovery and precommission of the quadrants on EIB.
*** Erratum ***
Due to an offset between the Kieback & Peter interface and the inverter, the supply and return fan speeds reported were incorrect.
The values in the table below have been updated, and an additional frequency step has been added.
| Time | Mode | Supply fan frequency | Return fan frequency | Note |
| April 27, 12:30 UTC | Automatic | ~32 Hz | ~13.8 Hz | Supply: air speed ~2.6m/s → Air flux~3276 m³/h Return: air speed ~0.2 m/s → Air flux~252 m³/h |
| April 27, 16:10 UTC | Manual | ~22 Hz | ~15.7 Hz | Supply: air speed ~2.5m/s → Air flux~3150 m³/h Return: air speed ~0.3 m/s → Air flux~378 m³/h |
| April 28, 09:40 UTC | Automatic | ~32.8 Hz | ~13.8 Hz | |
| April 28, 15:00 UTC | Manual | ~22 Hz | ~15.7 Hz | |
| April 29, 10:36 UTC | Manual | ~28.5 Hz | ~13.8 Hz | Supply: air speed ~3m/s → Air flux~3780 m³/h Return: air speed ~0.3 m/s → Air flux~378 m³/h |
ITF found DOWN in UPGRADING mode.
he planned activity on Free space ALS / LB->EIB pointing went on for the whole shift.
Software
13:10 UTC: SUSP_Fb restarted after a crash
In order to debug the new QPDs installed for the BPL loop, which show anomalous noise in both DC and asymmetries signals, we removed from EIB bench one of the new QPD (SN: DCQPD26-1) and from EAB bench the QPD used for IBJM (SN: DCQPD 4).
For the time being, EIB bench is blocked and the PMC in scan with the beam blocked on LB.
In the table below are reported the latest actions performed on the supply and return fan operation.
| Time | Mode | Supply fan frequency | Return fan frequency | Note |
| April 27, 12:30 UTC | Automatic | ~32 Hz | ~13.8 Hz | Supply: air speed ~2.6m/s → Air flux~3276 m³/h Return: air speed ~0.2 m/s → Air flux~252 m³/h |
| April 27, 16:10 UTC | Manual | ~28.5 Hz | ~13.8 Hz | Supply: air speed ~2.5m/s → Air flux~3150 m³/h Return: air speed ~0.3 m/s → Air flux~378 m³/h |
| April 28, 09:40 UTC | Automatic | ~32.8 Hz | ~13.8 Hz | |
| April 28, 15:00 UTC | Manual | ~28.5 Hz | ~13.8 Hz |
In Figure 1, a slight temperature drift of approximately 0.1–0.2 °C is observed over time, together with oscillatory behavior in the humidity control loop.
The morning was dedicated to weekly maintenance started at 6:00UTC, here a list of the activity reported to the control room:
- standard vacuum refill from 6:00UTC to 10:00UTC (VAC Team);
- cleaning of central and west end buildings (Menzione with external firm: from 6:00UTC to 10:00UTC);
- ALS: free space beating installation (#69042);
- SBE: EIB balancing (#69045);
- SQZ: removal of the fiber noise box (#69047);
- TCS: chiller check and refill (Menzione 7:15UTC);
thermal camera reference 8:00UTC;
the work on injection system is still in progress...
Today I removed the “Fiber Noise box 2” in the Atrium used for the phase noise suppression loop. The goal would be to bring it to Padova to upgrade it. In particular, the idea is to actively -stabilize the plate that houses the fibers and, if needed, shorten the fibers using the fiber splicing.
Activity on detLab:
First I connected the output of the fiber going to the squeezer directly to the SQZ main PLL. This way, the retroreflector is excluded; otherwise, it would have reflected about 50% of the power back toward the injection (see Fig1).
In this configuration the power reaching the PLL from the injection is doubled . This is evident from the DC value of the PLL photodiodes (see Fig2)
Activity on EE-Room
I turned off the RF amplifier that powered the AOM in the fiber noise box 2 . The amplifier was then removed and will be taken to Padova along with the box.
Activity in the Atrium
After disconnecting the cables and the optical fibers from the Fiber noise Box 2 , I removed the box. The optical fiber that powered the box is now directly connected to the fiber that carries the signal to detection. This connection was made by inserting a 10 dB Thorlabs fiber attenuator to keep the power reaching the squeezer approximately the same (figure 1). After this operation, the DC value of the photodiodes slightly increased to above 0.30 V (figure 3).
The disconnected cables in the atrium are labelled as
“Fiber Box” RF amplifiers power supply
“Fiber Box LO Sin” RF output of the first amplifier in the box
“FiberBox LO Des” RF output of the second amplifier in the box
“Fiber Box LO AOM” RF power to the AOM in the box
Before the intervention of Henk Jan, we tried to rebalance the bench moving some weights on the bench and adding some more (around 3kgs). We had also to take off some weights of under the bench (5kg) in the upper right side of EIB (corner near SIB2 in SIB1 direction). At the end it was not possible to rebalance only with the weights and we asked for the expert intervention.
This morning around 8:50 UTC a resistance box provided by the electronic team was connected to the piezo driver controller of the BPL mirrors (INJ_BPL_QD1/2_H/V) in EEroom. Attached the FFT of the signals before and after installation.
Before the intervention of Henk Jan, we tried to rebalance the bench moving some weights on the bench and adding some more (around 3kgs). We had also to take off some weights of under the bench (5kg) in the upper right side of EIB (corner near SIB2 in SIB1 direction). At the end it was not possible to rebalance only with the weights and we asked for the expert intervention.
One week ago (Monday April 20th) at 6:50 UTC (8:50 LT) a magnetic comb with 1Hz spacing turned on, and it has been on since then. The origin is still unknown. The noise is mostly affecting up to few tens of Hz, and has the characteristics of a clock driven noise, yet it is somehow intense and widespread. Here is what we observed so far:
- the noise was first noticed in the external magnetometer (thanks Renato)
- the source is most likely DC-powered since the noise is not consistent with 50 Hz sidebands
- comb lines are very narrow, with at least ms stability, and this points to some clock driven device.
- the noise is louder (a factor 10 to 100 louder than EXT) in CEB magnetometers and in magnetometers close to towers. NI, WI, BS are the loudest.
- the noise is present also in the NE and WE magnetometers (curious!) where it started at the same time as for CEB
- no evidence of noise is seen in any VOLT, CURR sensor (UPS or IPS), as well as nothing in the grounding monitor
- the ELECTRIC monitor seems to show a factor two increase in the amplitude of lines at 1,2,3,4 Hz.
- Large coils are all off: VPM processes tell that all coils relay are set to 0, and in addition CURR and VOLT coils monitors do not see any noise
- the logbook does not report any concurrent operation
- VAC team and Davide are not aware of any new hardware or operation at that time
- the VPM log does not report any action at that time
