As planned, this morning at 5.50 UTC, the ETM RH powers have been changed with the iTF in 'adjusting'.

The old and new values are summarized below:

We did not manage to analyze the results of the free swinging mirrors with the kick measurement made yesterday (probably because they were not excited enough).

For this reason this afternoon we performed again this measurement, but we first opened the dampers, we manually put in down the ITF and then we applied the corrections (more than once, to keep the mirror excited).

The first kick was done at 15:51:36 UTC, and the data were analyzed 3 minutes later taking the peaks during 220s (so it cannot be defined "hot" itf measurement).

We obtained 2% mismatch for the north and 1,6% for the west (see plots)

The goal of the shift was to characterize the ITF working point with the following RH powers:

The actions performed during the shift are listed below:

13.08 UTC: ITF relocked in LN3

14.18 UTC: ITF manually unlocked to perform input beam mode matching measurement with the free swinging technique and green laser scan (performed by Suzanne, Camilla and Matthieu).

                    See detailes in 64204

15.03 UTC: ITF relocked in CARM NULL 1F

16.08 UTC: OMC scan started (performed by Romain and Andrea)

16.30 UTC: OMC scan ended 

16.52 UTC: ITF relocked in LN2

After 1.5 hr in LN2, at 18.20 UTC, Andrea will proceed with the lock acquisition.

The main ITF signals during this afternoon are shown in figure 1.

Figure 1 shows the scan of the OMC performed from 16h08 utc to 16h30 utc, after waiting for 1 hour in CARM_NULL_1F.

Figure 2 shows a zoom of this scan around a Free Spectral Range.

Assuming a calibration factor of about 4800 for B1_PD3, we have: ~75 mW on the first order mode, ~29 mW on the second order mode, ~200 mW on each of the third and fourth order modes, ~70 mW on each of the 5th and 6th order modes, ...

This afternoon we performed some measurements to verify the mismatch towards the arms. The last measurement done is reported in #63374.

First, we performed the free swinging method, giving a kick on the end mirrors (with the dampers opened). The GPS of the kick (we gave the kick simultaneously for the West and North arms) is 14:17:00 UTC.

However, when analysing the data we could not find reasonable values of mismatch. We need to verify if there is any problem with the Matlab code to debug, or there was something wrong with the measurements. In Fig. 1 we can see the time window of the free swinging mirrors. To be noted that the west arm starts swinging after roughly 15 seconds with respect to the North Arm. On Fig.2 we can see the surposed flashs of B7 and B8.

Then, we perform the measurements with the Green Scan. The GPS in this case 14:30:43 UTC (Fig 3). Figs 4 and 5 show the scans of the TEM 00 mode and TEM 02 mode respectively. In this case, for the north arm we found 3.3% and 1.4% for the west arm, as shown in Fig. 6.

VPM process has been reloaded and, after a fix, the 2 new flags are correctly display. I'll watch the new flags regularly in the following days to check that the parameters are correct.

Francesco called me because of the change of state of WI CO2 laser.

To restore the standard condition, I adjusted the WI chiller set point from 19.04 degrees to 19.05 degrees (15.40 UTC).

The BCK chiller set point has been chaged accordingly.

Following the issue on ALS flip mirror in the early morning (Entry 64161), 2 new flags have been implemented for the DMS in order to monitor them. Configuration inside the VPM process have been done and will be reload during Tuesday maintenance to be made effective.

Tuesday 30th of April a slow cold FSR scan has been performed (LOGBOOK n°64135). Here is the report of the analysis concerning the estimation of the finesse of both north and west Fabry-Perot cavities. On each of the 12 FSR scans, an Airy peak has been fitted. From those fits, the FSR and the width at half maximum have been estimated allowing us to derive the finesse. Then we took the average of all the results. Values obtained for each cavities are summarized below :

B7 : average finesse 463.16 standard deviation 2.99
B8 : average finesse 447.59 standard deviation 4.04

Figure 1 shows one example of fit for both north and west scan. For each example, the fit is shown on the full scan and zoomed on the first TEM00 mode. As it can be seen, the data are very noisy. Nevertheless, this can not explain why results are asymmetric between north and west cavities.

We started at 14:00 UTC and to not interfere with the ITF and risk to unlock, we manually injected the SQZ. 

• System initial status: ITF LOW NOISE 3; SQZ_MAIN @SQZ_Locked_NO_FC

• 14:28:26 AA loop engaged

We performed a first CC phase scan (Fig. 1-2): 

• 14:39 CC scan started DCP = 195 Hz

• 15:02:21 CC scan ended (fast shutter closed), ITF in shot

• 15:26:15 fast shutter opened

• 15:36:22 ITF in SQZ phi0 = 0.65 rad

• 15:39:19 SQB1 TX angle set to 300 (initially at 310)

• 16:42:58 SQB1 X position set to -3200 (original position)

• 16:47:58 ITF in SQZ

After the first CC scan we realized the magnitude was similar to the last shift (entry #64094) even though there should be a higher level of injected SQZ. We decided to try to improve the magnitude by acting on SQB1_TX and SQB1_X DOFs. We worked on this from 15:39:19 to 16:42:58 UTC. Finally we left SQB1_X as it was and we changed the set point of SQB1_TX from 310 to 330 urad. The fluctuations on the magnitude are reduced (Fig. 3).

We then performed another phase scan (Fig. 4-5)

• 17:05 CC scan started DCP = 195 Hz

• 17:28 CC scan ended (fast shutter closed), ITF in shot

After the second CC scan we realized the SQZ angle is actually around 1.05 rad, so we decided to repeat the SQZ mode acquisition.

• 17:39:53 fast shutter opened, ITF in SQZ phi0 = 1.05 rad

• 17:49:08 CC loop engaged, gain=75000 (glitch between 17:54:50 and 17:56:14)

• 17:58:54 ITF in ASQZ phi0 = 2.75 rad

We were able to get another CC phase scan with DCP setpoint at 225 Hz (Fig. 6-7). Fig. 8 reports also the shot SQZ and ASQZ acquisitions made after the scan.

• 18:11 DCP value set to 225 Hz

• 18:44:11 ITF in shot

• 18:46: CC scan started DCP = 225 Hz

• 19:09 CC scan ended

• 19:15:07 ITF in ASQZ phi0 = 2.7 rad

• 19:22:48 ITF in SQZ phi0 = 0.95 rad

• 19:28 DCP value set back to 195 Hz

Nicola called me because the WI CO2 laser changed its state (see figure 1).
To address the change in the WI outer power, I first rotated the WI outer ring waveplate to recover the nominal  power to be injected into the ITF (11.59 UTC-12.00.26 UTC ) (ITF in ‘adjusting’ mode). Then, I adjusted the WI chiller set point to return the laser to its usual operating point, in particular I decreased it by 0.01 degrees, from 19.02 to 19.01 (12.21.04 UTC). The BCK chiller set point has been changed accordingly. This action did not solve the problem; in fact, the direction turned out to be wrong.
Thus, at 12.41 UTC, I increased the chiller set point from 19.01 to 19.03 degrees.
Finally, the standard situation has been restored (see fig.2). 

As observed by Federico, the metronix magnetometer in MCB is having an issue starting from 2023 October 2 UTC 00:03:03 (Figure 1). The signal looks corrupted (Figure 2).  This does not seem an issue with the ADC and neither with the driving electronics, since other channels sharing the same boards are fine. We will investigate further at next maintenance.

This fauty condition was not signalled by the DMS DeadChannel since the associated rms was smaller than the set threshold. The rms threshold has been updated (0.35 to 1 nT) and this channel temporary shelved.

Errata corridge: the plot of the squeezing level and the BLRMS of the first CC scan (t_start = 16:52 UTC) was erroneously equal to the one of the second CC scan. I attach the correct plot.

I attach the plots for the two CC phase scans performed during the shift of yesterday. I was not able to produce the BNS range plot for the second scan, which is anyway visible in Fig.4.

The second scan started at 18:11 UTC, with the same duration times of shot and CC scan as of the first one.

SHIFT GOAL:

The goal was to perform several CC scan at different SR angle. Nevertheless, due the not optimum condition of the MZ and OPA (waiting for the retuning) we decid to perform a couple of scan without changing the SR angle to check the SQZ alignment-

SHIFT activity:

We started at  16:00 UTC and to not interfere with the ITF and risk to unlock, we manually injected the SQZ. 

• System initial status: ITF LOW NOISE 3; SQZ_MAIN @SQZ_Locked_NO_FC

• 16:10:39 EQB1  fast shutter opened (process: SQZ_ctrl/shutter ‘open’)

After that the CC_loop was engaged and then  the AA (process: SQZ_PLL_AA/ Matrix and Filter ‘AA dither enable’).

• started a CC 4MHz phase scan @ 16:52. 

  • time per point = 6 s

  • - initial phase  = 20 degree

  • - final phase = 230 degree

  • - phase steps = 1 degree

  • - random phase = False

  • - Closed shutter sleep time = 120 s

  • - AA closed on dither = False

  • - cc loop gain   = 75000.0

N.B: No glitch during the scan, it was just before and after (see plot)

In meantime Henning checked the MZ and changed lowered again the offset at 0.035 V due to the humidity  misalignment that spoiled the contrast and induced the set point near the actuator saturation. After the Henning action we redid the scan. 

We stopped at 19.25 after that some data have been collected at the CC phase value corresponding to the SQZ and ASQZ, or better to the minimum and maximum values in the BRMS range @210 MHz and in other ranges.

Further data  and plot in the following comments.

Today after the work at  UTA in DET  (# 64079) the squeezed unlocked due to the change of th ehumidity condition (FIG1). I waited for humidity condition recovery to check and try to relock the MZ. It happened at about 10 UtC. I started to check about at 20:13.

Nevertheless on the signal it was and it is present an oscillation with for me not understood origin (FIG2) un. I tried to check the origin but I was not able to find it and understand. I leave the system with the MZ unlocked and tomorrow morning I will contact Henning to check.

Note that the ITF unlock happend when I put in pause the SQZ MAIN automation to work on SQZ system. Maybe it is my fault (FIG3)

Today the lock acquisition was very troublesome due an excess of noise on the West Green beam. We tried to check the coupling of the fibers on the DAQ room, but it didn't solve the problem. Then we went to the end building and tried to improve the fiber coupling by moving the fibers in the rack. We found a position where the noise was reduced. Still there is some green power missing, so tomorrow some more systematic alignment work will be done, in order to better align the green in the SHG box. After this action the lock acquisition worked properly.

Around 19:00 LT, I discovered that the WI flip mirror used to acquire the thermal camera images was closed. This means that the CH and DAS were blocked on the bench since last night.

Gianmatteo re-opened it at 19.05 UTC.

After the earthquake in Japan, we relocked at the first trial and after we arrived LN3_SQZ we started to tune the noise injections for the PSTAB loop (both at LF and HF). After the amplitude of the noise was tuned, we added the corresponding functions into the "injection_SSFS.py" script.

We then proceeded to repeat by hand the two last injections of the SSFS loop, that last shift made the ITF unlock. We decreased slightly their amplitude, while checking that the coherence with Hrec was still high. Now the script launches: CLEAN SSFS_UGF PSTAB_LF PSTAB_HF and then the 4 other SSFS injections at lower frequencies (down to 100 Hz). The operator launched the script and it worked without any problem. Figure 1 shows the injection corresponding to SSFS_UGF, and I think the current UGF is safe enough (I wouldn't push much higher, to ensure robustness, unless the noise injections suggest that it is limiting).

At this point we passed to the DIFFp topic. We started by opening the DIFFp_TX servo loop (which zeros the offset!), and then we started to put back the offset. However this didn't zeroed the new signals and so we continued to increase the offset. During this scan we tried to tune the phase, slightly, even if it was already quite good. Then we repeated the same operation with the TY loop. Figure 2 shows the two scans that we did. For the TY the phases were not clear so we left the deafult ones.

The phases we put are:DIFFp_TX_DCP_HF_mag_B1_phi0 = 0.5;       DIFFp_TX_DCP_mag_B1_phi0 =0.5

This morning we noticed that the WI main CO2 laser continued to be in an unstable state since last night at around 06.30 UTC, so we decided to act on WI CO2 chiller setpoint, changing it from 19.04 °C to 19.02°C (12.37 UTC, Fig. 1) in order to restore the correct power values. Also the BCK chiller set point has been changed at the same setpoint.

After this change, there have been no significant changes in the powers of the actuators, which have remained stable around their nominal values. The situation will continue to be monitored to determine whether further intervention will be necessary.

Following the activity of yesterday night (63940), we noticed that the WI main CO2 laser continued to be in an unstable state, so we decided to act on WI CO2 chiller setpoint, changing it from 19.02 °C to 19.04°C (08.27 UTC, Fig. 1). Also the BCK chiller set point has been changed at the same setpoint.

Soon after, we noticed a prominent change in the WI CO2 signals and we needed to recover the WI CO2 DAS outer ring power injected in the ITF, by rotating back the relative wave plate to recover the condition with respect to yesterday’s action (08.45 UTC, Fig. 2).

We’ll continue to monitor the situation to evaluate if a further chiller setpoint small change will be needed.

Today, at 15.06 UTC, the WI chiller set point has been decreased from 19.00 C to 18.98 C. The BCK chiller set point has been changed accordingly. 
The effect was significat: the total power emitted by the laser increased  but it altered the polarization. In agreement with Fiodor, to avoid some instability problems related to the power change, the step has been reverted. Thus, at 15.28 UTC, the WI chiller set point (and that of the BCK one) has been increased back to 19.00 C. Then,  Francesco alerted me of the TCS DMS flags which were red. So, with ITF in down, I checked all CO2 powers restoring the nominal ones.  This activity has been completed at 16.47 UTC. Now, the laser WP came back to the pre-step condition (see attached figure).

On the March 12th, a shaker has been installed on the Laser Bench to perform sismic noise injection. After those studies done on the 14th, the electronics that controls the shaker (deployed on the ground) has been left ON (with 0V of input voltage) to have the possibility to further perform other remote injections. 
However, entering in the laser lab few days later, we noticed a slightly higher acoustic noise than usual. We decided then to switch OFF that electronics, and indeed the noise reduced.

Looking at the environmental sensors present in laser lab, we found this noise visible as both high frequency broad noise (>200Hz)  and with some lines a low frequency (~45Hz and harmonics).
Moreover, we see it on acoustic (see fig. 1-3, 5) and sismic (fig. 4) sensors. While the noise is visible on both benches, the effect (seismic and acoustic) on EIB is really faint (see fig 4-5).

Nevertheless, we didn't find any noticeble effect on Hrec.  

We checked some signals of interest after the realignment of the RFC and could not see any clear improvment neither in LN3 (figure1) nor in INJ stand alone (figure 2).

RFC alignment in LN3

We moved the setpoints of the piezo from around 17h45 UTC to 18h10. We improved the alignment as shown in fig.1

(We also updated the thresholds in the DMS).

SBE EIB noise injections in LN3 (sine @ 0.5Hz)

Analysis of the noise injections will follow.