INJ recovery :

Power calibrations :

Having fixed the power fluctuations at the PMC output that were due to loop oscillation. We worked on the calibration of the photodiodes and power budget :

With 0.615 V on PMC TRA we measured 51 W at PMC output.

With 29.6 W measured after M5 we had 30.4 W on EIB_PD_out not.

With IPC1 at full power we had 41.4 W out of the 51 W at PMC output.
This means 1-(41.4/(51*0.97)) about 16.4 % losses in the EOM FI IPC line.
The losses are quite high but the beam does not seem to be clipped. A potential explanation could be the angle of incidence of the beam arriving on the TFP polarizers at the input and output of the faraday. They are quite sensitive to the aoi. 
We tried to tune the HWP of the FI but it was already set to the maximum. Rotated them is not straight forward, we did not ush this investigation any further.

With 29.4 W measured after M5, we worked on the alignment and managed to get 18 W on IMC TRA. The power seen by the IMC TRA photodiode was consistent with the ones seen by the PSTAB photodiodes.
So it seems that we have an overall throughput of the IMC of the order of 18/29.4 = 0.61% which seems similar to what we had last time we measured the throughput losses (#67826)

By looking at the power on IMC REFL in locked and unlocked states and getting rid of the offset we have : (1.12−0.35)÷(6.38−0.35) = 12.8 % of the power which is reflected when we are locked with 18 W on IMC TRA.

Detailed study to make the comparision with previous power budget studies to come.

To be noted that somehow the DC values seen by the different PD and QPD have changed. This is a phenomena that has already been seen in the past and that could not be explained if not by the polarization somehow slightly rotating wile aligning on the parabolic mirrors and the IPC in front of the PD working closed to the full exctinction (#45306). We will investigate it and we will report the DC values to their normal working point.

Issues to be solved : BPC DSP non responding 
Still to be done when the EIB will be suspended: close the IMC AA, potentially need to redo the matrix. General check of the loops. Updated throughput budget
 

BPL :

We measured the beam properties and they are has expected for both NF and FF about 400 um with accumulated gouy phase difference of 90 degrees (see plots).

We power supplied the QPD and checked their behavior. For now they look quite noisy, especially the FF (see attached figure) but we should close the enclosure of EIB and suspend it before making any conclusion.
We could also see some resonance at 1.7 kHz with harmonics at 50 Hz that could be linked to one of the PZT. 

Still to be done : Connect the PZT to the DAC and check their good functionning. Commissioning of the loop with EIB suspended.

Today we installed the telescope to focalize into the PPLN crystal (waist in the crystal 17um). See first 2 attached photos.

The last lens f=75 mm is positioned at around 110mm from the one before the crystal of f=35mm and is needed to collimate the beam.

We obtained an IR beam with 3.1 mm diameter, collimated over 80cm. For the green beam we will have a diameter of 1.8 mm (see pict 3. On the bottom is the propoagation of the green beam after the waist in the crystal, while on the top is the whole telescope for the IR).

The telescope has been designed to inject the green beam in the fiber coupler Thorlabs PAF2A11A (MFD 1.8mm). So it is not very well adapted to inject the IR in the coupler PAFX11C (MFD 2.09mm), and we will have to add a lens with a focal of 1000mm to have the good size of the beam at the level of the coupler.

After optimization of the alignment and the temperature of the crystal oven (set to 113,27C) we obtained 27,4 mW of green over 1.19 W of IR, which is a conversion efficiency of 1.9% (as expected).

During maintenance shift we replaced the top fan unit of Sa_IB since a DSP board was overheating (> 50 C). In the afternoon, after the daily meeting, we also replaced the DSP board of BPC that drives the piezos (serial #43141 was replaced with DSP #43145) in order to fix the communication issues on the RapidIO bus.   

Today we could start to work on the ALS line on the EIB. A sketch of the pick off is shown in fig.1.



We started by characterizing the beam at the input of the EIB.
Since there are 45W coming from the LB, we could only analyze the beam after M1c, which is a beam splitter 97/3 made from the LMA (the characterization of the mirrorgives  made by the LMA gives transmittivity of 2.7% at 45°  polar S. The AR coating on the second surface has a reflectivity of 260 ppm). We added another BS 97/3 in order to further attenuate the beam for the beam scan.
%beam at the input of EIB
Z=[54 95.5 124 175]*1e-2; %beam at the input of EIB
Wx=[1367 1516 1706 2144]*1e-6*0.5; Wy=[1370 1511 1685 2055]*1e-6*0.5;
The waist position is z0 = 13 cm from the EIB border, and its value w0 = 638 um. (fig.2 )

This is quite consistent with the values taken from the optocad (on which Matthieu based the telescope, shown in fig 3). Since the telescope is designed positioning L1 29cm away from the waist of the beam which is 638 um, we positioned L1 13 cm + 29 cm from the EIB border. We characterized it (shown in fig 4):
%beam after L1
Z=[54 95.5 124 175]*1e-2; %beam after L1
Wx=[1001 855 1147 1622]*1e-6*0.5; Wy=[999 900 1167 1562]*1e-6*0.5; 

We installed after 75cm from L1 the diverging -70mm lens and the 150mm lens, spaced by around 8.6cm (verifying after these two that we have the good waist with the beam scan).
 
 
 
 

1. Injection Line Alignment & Power Loss Investigation

We continued work on the alignment following suspicions of beam clipping in the EOM + FI + IPC section. Initial measurements revealed significant throughput issues:

•  Measured 50.4 W at the PMC output and only 24.2 W after EIB M5.

• After rotating IPC1 for full transmission, power increased to 38.3 W.

• Accounting for measurement uncertainties and the new BPL/ALS pick-off (~3%), we calculated total losses of 21%. This is significantly higher than the historical baseline of 10% (ref: 50224).

Realignment Actions: We performed a systematic high-power realignment. By optimizing the throughput at the output of the third EOM by moving EIB M1c and centering the beam through the FI and IPC using EIB M2/M3, we achieved the following:

• Final Power: 39.4 W measured after M5 with 45.5 W at PMC TRA.

• Final Loss: Calculated at ~14% (normalized via PMC TRA monitor: 39.4/45.5×0.566/0.572).

• Outcome: Beam profile visually improved; alignment proceeded through the telescope to the BPC QPD.

2. INJ Recovery & Loop Status

• BPC Board: Valerio and Marco investigated the BPC board. We are observing an unidentified saturation-like behavior on the PZT where it stops responding. However, by maintaining low PZT values, we successfully locked the BPC.

• IMC Lock: After realigning SIB1 and the MC, the IMC was locked.

• IPC1 Adjustment: Power was reset to previous levels by monitoring the IMC REFL signal in the unlocked state.

• IMC AA : Locked in drift control. Need to work on the matrix with the new reflection

• Current Status: The IMC reflection suggests a larger mode mismatch than previously observed. Transmission power is currently lower at ~15 W.

• Pending: Investigation of mismatch causes (?)band fine-tuning of IMC loops (AA, PDH, offsets, and Transfer Functions).

3. Beam Pointing Line (BPL)

• Set all optics in transmission of M1c.

• Power Measurements: Found 20.5 mW on the FF QPD and 23 mW on the NF QPD. These values align with our theoretical expectations.

• Pending: Verification of beam properties on both QPDs and functional checks of the QPD and PZT.

4. Additional Activities

• PMC Diagbox: Performed fine alignment. Despite using the same mirror transmission as before, the monitor signal is limited to 0.62 V.

• PMC Loop Stability: Reduced the loop gain to eliminate oscillations. This appears to have resolved the power fluctuations observed today

• ALS: (See dedicated entry).

ITF found in UPGRADING Mode and DOWN State.
All times are UTC.
Activity during maintenance:
- TCS Chillers refill.
- Cleaning operations of the experimental areas.
- TCS Power CHecks (Lumaca).
- TCS Image Camera references.

08:00 Start of Free space ALS / LB->EIB pointing activity in Laser Lab (De Rossi, Spinicelli, Cavalieri, Nocera).
13:30 BPC DSP activity (Boschi, Pierdibene).

ITF left in UPGRADING Mode and DOWN State.

We performed a quick functionality test of the GRAS-41NC outdoor microphone which EGO purchased for the external environmental station. The test confirms that the microphone is working. See Figures 1 and 2.

We attempted a similar functionality test of the GURALP 3ESPC (as well purchased for the external station). The idea was to plug it in place of the Guralp 40T placed next to the tiltmeter. We realized then that the cable, although compatible, has a different pin-out. we postpone the test after checking with Rosario.

Since a while we realized that the NEB vertical magnetometer (ENV_NEB_MAG_V) has a strange noise behaviour below a few Hz. It appears as excess noise with respect to the other and lack of coherence. We noticed this by looking at the no-trains data (elog 68641). Figure 3 compares spectrograms for the 3 NEB magnetometers, the extra noise is seen only in the "V" channel... this is quite strange being the three magnetometer co-located.

We first connected and diconnected the cable of the "V" magnetometer: the low-freaquency noise changed: from excess noise to reduced response with respect to the other 2 sensors: Figure 4

We placed the 3 magnetometers all vertical and close by to the "V" one: while the "W" and "N" have good coherence down to 0.1Hz, the coherence with the "V" magnetometer drops below 1 Hz: Figure 5

Keeping the magnetometers in this position, we exchange the cable of the "V" and the "W", the signal with the reduced low frequency response moves to the "W". This proves that the problem is not with the cable but with the sensor.

Our conclusion is that the NEB "V" magnetometer has some issue, which needs to be addressed.

Today we kept on working on the alignment. 
First at low power and then we swap the LB M13 mirror that was reflecting only 1% of the power of the PMC transmission and put the nominal one that relfect it all. 
Unfortunately we had to work again on the alignment but at high power. We managed to get a rough alignment with the PMC in scan at medium power (10W).
The beam was still low on the BPC QPD, we had to realign it by hand using M6 and M8. We eventually reach the values of TX TY X and Y that we had before starting the intervention.  
There are still things to understand, especially the DC values of the PD and QPD that seems to be different, the IMC REFL seems to be different as well. 

Side activity : we started to realign the beam inside the PMC diagbox. 

ITF found in Upgrading mode and in down mode.

The shift was dedicated to the planned activity of "Free space ALS / LB -> EIB pointing"; activity still in progress.

Software

At 8:03 UTC BACnetServer restarted because it was not providing data.

Suspsensions / SBE

All the suspensions / SBE loops were opened by the guuardian following the earthquake: 2026-04-20 07:53:00 (UTC) M 7.4 - 100 km ENE of Miyako, Japan.   I have successfully reclosed all loops; for PR, SDB1, and MC, Paolo's assistance was necessary.

After the work done by Bulten and co on the EIB rebalancing with started to work on the realignement of the beam from PMC output towards the BPC quadrant with the EIB blocked in its nominal position.
To do so we locked the PMC with the reflection as a trigger. The LB_M13 is still a beam sampler that reflect only about 1% of the PMC TRA. The power was also reduce at the PMC input by about 50%. As a result we were working with a beam of about 350 mW to do the alignment.
We started by aligning the beam into the apertures which are at the output of the LB, using LB M13 and LB M14. While arriving on the EIB, we noticed that the beam was relatively low, few mm below the usual working point (100 mm). This is not completly explained, we checked the apertures at the output of the LB that were effectively at 100 mm. This discrepency can either be due to a height difference between the two benches or it means that we are not well aligned in the lens (f = 1000) at the output of the laser bench. The heght of this last an not be set.
We decided to keep the pinholes as the horizontal reference for the beam at the output of the LB but to use M13 and M14 to get a beam propagating in the 100 mm plan on EIB. We did so and adjusted the height of the apertures at the output of LB.
From here we started the alignement of the beam on EB by setting the miror EIB M1a M1b and M1c. We used M1a and M1b to ensure that the beam was propagating in the 100 mm plan and in the right direction for the transmission of M1c that will be used both for ALS and for the BPL loop. Once it was done we moved M1c by hand both in horizontal shift and horizontal tilt to pass through the EOM and eventually reached the photodiodes downstream ( BPC QN DC and QF DC for example). We managed to get the expected DC on both quadrants about: 0.006 V  for 0.35 W of PMC TRA while we usualy have about 1V for 60 W of PMC TRA. 
From here we started to work on the alignment of the optics downstream of M1c.
We noticed that we were very high on PT_M1, also the Y of the BPC was quite out of range.
This is explained by the fact that the algnment on EIB as alwas been done with a beam that was slightly lower.
We decided to go on with a general realignment on EIB. At first we got the beam back in the 100 mm plan in transmission of M1c, using M1a and M1b, and check that we were indeed correctly passing through the EOM.
Then we used EIB M3 to get the beam centered at the exit of IPC1/ M4. Then we used the mirrors one after the other till M8 to center the beam on each other.
We eventually got some signals on both NF and FF QPD (note for the future : IBJM is convenient to visually check the FF). 
We will go on with the final fine alignment on monday.

Air Conditioning

BACnetServer crashed and restarted at 6:18UTC.

SBE

recovery of SPRB vertical position with F1 step motors from 15:20UTC to 17:25UTC.

For the enlargement of the VRS network @WE it was worth confirming the survey done (eLog 69010) with another independent one, carried out with classical tecnique by theodolite and post-processing by compensation software, as we did in the past for all the reference points installed in the Virgo Experimental Buildings (see also VIR-0523AF-13). During last Mar31-Apr1 we carried out the survey by teodolithe Leica TDA5000 and then the analisys of the raw data by compensationt software StarNet.

Tab1 reports the final result of the compensation obtained showing the VRS coordinates, the standard deviations and the parameters of the relevant error ellipses port the new reference points considered.The resuls obtained are perfectly coherent with those deriving from the laser tracker survey, so that the coordinates of the new points are validated.

Fig.8 reports the whole scheme of the survey carried out, with the graphical indication of the error ellipses, while Fig.1 to 7 shown some pictures of the survey carried out.

Following the installation of the new reference points @WE building (placed on the concrete walls of the building and on the tower floor), last Feb24 it has been carried out the survey with the laser tracker Leica AT403 in order to estabilish the new coordinates of the reference points.

We performed 3 different measures for each of the 5 station in total, at different positions in the building. Each measure has been processed with the Best Fit technique.

Tab1 summarizes the result of the survey in VRS coordinates, while Fig.7 reports the scheme of the survey for one of the stations (S05).

Fig.1 to 6 shown the pictures of the survey carried out and some of the new reference points.

Yesterday, due to the pumping transient, V coils were going towards saturation, we opened the V loops.

Today position of vertical filters have been recovered through the use of the motors.

SR is now back in standard control configuration (TOP H+V pos and inertial, F7 and LC controls).

By adding about 10 kg of counterweights we managed to get an acceptable poisiton of the EIB and managed to close the loop. Some actuators are quite at the limit. 
We will work on the balancing tomorrow with Henk Jan to put some of the counterweights on the bottom part and get a healthier situation for the bench.

THURSDAY 

WI PAM 
This morning, we replaced our LED with one kindly provided by the EGO optics group, as the one we brought from Rome was too weak and might not have been visible inside the tower. To be on the safe side, we also verified that the red LED light passes through the ZnSe viewport using a spare window (see Fig. 1). After that, we switched on the heater to align the beam with the new LED.

We then proceeded with the installation on the tower base. During the installation, it was noticed that the LED mount prevented the actuator from reaching the nominal distance to the viewport. The actuator was therefore removed and the LED mount was modified (the final configuration is shown in Fig. 2). At this stage, the LED was realigned to the thermal radiation by applying V=6.8 V I=4. 2 A reaching a temperature of about 670 °C (see Fig. 3-Fig. 4).

The installation on the tower base was then repeated and successfully completed (see Fig. 5). Once the actuator was correctly positioned, it was secured to the alignment plate using clamps.

The cabling, including the remote powering of the actuator and the operation of the picomotors, was tested after completing the installation.

The WI PAM actuator was left OFF, with the power supplies ON, the maximum current set to 8 A, and the output voltage disabled (see Fig. 6).

NI PAM

At this stage, we moved to the NI HR side. The NI PAM was removed in order to install the alignment layers on the tower base. To perform this operation, the tripod supporting both the camera and the thermal camera was moved. The alignment plate on which the tripod is now placed has a thickness of 18 mm; therefore, both cameras need to be realigned and refocused (see Fig. 7).
The NI PAM was left near the NI CO₂ laser bench, inside the white tent marking the laser hazard area.

Today we installed all the optics on the EIB, without aligning them, in order to let Henk Jan rebalance the bench.

Pictures 1 and 2 show the optics added. The list with the corresponding weight are in the attached pdf.

The total added weight is around 12.2 kg.

We removed from the EIB some other optics no more needed (a mirror and a density). A beam dump of 960 g was replaced with a 255 g standard mount, so the total removed weight is around 750

Yesterday afternoon we started the installation of the LB-EIB pointing, as shown in the block diagram on Fig. 1. After removing all the old components and the old IBMS system, yesterday evening we finished to install the new mirrors after the PMC on the laser bench (Figs. 2 and 3) and to take some references for the beam. Today we installed also all the optical components on the EIB. 

Here a list of the new components on EIB and the weight of each of them:

1. M1a - 516 g
2. M1b - 772 g
3. M1c - 516 g
4. L1 - 173 g
5. L2 - 173 g
6. PT_M1 - 430 g
7. PT_M2 - 430g
8. QPD NF - 1360 g
9. QPD FF - 1360g
10. clamps and screws - 625 g

The total weight is 6354 g. We did a rough alignment but the fine alignment is going to be performed once EIB is rebalanced to have the right position of the main beam. Attached some pictures before (Figs. 4 to 6), and after the installation on EIB (Figs. 7 to 10). 

ITF found in UPGRADING mode and in DOWN state
The planned activities went on without major issues:

- Free space ALS / LB->EIB pointing (De Rossi, Spinicelli, Lagabbe, Melo, Gosselin)
- NI cryotrap repair (Vacuum Group)
- WI PAM installation (Nardecchia, Aiello)
- DMS maintenance (Berni)

The TCS_PAM_WI_PowerSupply server was launched yesterday at 13:45 UTC. Data has been archived to the DAQ since 14:10 UTC. For unknown reasons, after 15:00 UTC, there is a data gap of about 10 minutes (see figure1). After that, everything seems to be working properly (see figure2).

This afternoon we could start the work on ALS.

• We switched off all the ALS is in the Laser Lab atrium (taking notes for the cabliing): 

1064 pd alim L.2.4 DCF 21   (lemo adc 3 orange)
534 pd alim L3.1 DCF 21     (lemo adc 6 blue)
West beating RF PD alim  L3.2 DCF 21  (sma cable 2 atr-piscina 15m  lemo adc 5 green)     fiber EIB atrium B 14m
North beating RF PD alim L3.3 DCF 21   (sma cable 1 atr-piscina 15m  lemo adc 4 yellow)  fiber EIB atrium A 14m

Box ALS Ctrl PD alim 1 L2.2 DCF21                (lemo adc 1 brown)
Box ALS Ctrl flip mirror alim 1 L2.3 DCF21

• Installation of some of the optics on the EIB.
  • We removed extra weight from the EIB (3 flip mirrors from IBMS, for a total weight of 1.55 kg).
  •  Since we do not have the main beam pickoff available yet, we installed a fibered laser at 1064 nm for alignment and we started to install some optics.
  • The goal is to move the setup from the SHG box (pict 1 and 2) on the EIB (we cannot simply move the whole 40cmx50cm bench because its own weight is more than 20kg. Moreover the height of the beam in the box is 7.5 cm while on the EIB is 10 cm)

To be continued...

Roberto and Federico completed the cabling of the WI PAM source, both at the actuator level and in the TCS room, to provide power and enable temperature monitoring (see Fig. 1).
The temperature of the heater is available under the channel INF_TCS_WI_IntHeater_TE.
 
In the afternoon, Elian completed the ethernet cabling for the WI PAM power supply in the TCS room, while Giulio set up the process on the VPM to control the switching on and off of the WI PAM actuator by setting the desired voltage (see Fig. 2).

Giulio also integrated the data to monitor the applied voltage, the current drawn by the actuator, and the applied power, which are now available on DD under the following names:

• TCS_PAM_PowerUnitWI_Heater_p32_curr
• TCS_PAM_PowerUnitWI_Heater_p32_volt
• TCS_PAM_PowerUnitWI_Heater_p32_power

! The data are available online but we are not able to see them in the DD (see Fig. 3).

After completion of the cabling activities, the following actions were performed:

• Alignment of the LED with the thermal radiation emitted by the heater

• Installation of the alignment mask (“smile”) in the optical path and verification of its focus at the nominal position of the WI HR surface. Figure 4 shows the “smile” for lens L2 in two configurations: the left image corresponds to a non-optimized lens position, while the right image shows the smile in the optimized lens configuration.

The actuator was operated at V = 6 V and I = 4.1 A and the temperature of the heater reaches 600 °C (see Fig. 5).
Tomorrow we will proceed with the final positioning of the WI PAM actuator on the tower base.

ITF found in Upgrading mode and in Down state.

- SR loops still opened after the susp intervention.
- SDB1 and SDB2 loops still opened

The planned activities went on without major issues::

- Free space ALS / LB->EIB pointing
- NI cryotrap repair
- WI PAM installation