Virgo Logbook

AdV-TCS (Point Absorbers Mitigation)

montanari, nardecchia, spinicelli, tomelleri, tringali - 23:56 Tuesday 22 July 2025 (67353)

Shift on IPATSiA at WE: cabling

This afternoon, the ITF experienced locking troubles, and the shift started later than planned.
During the available time window, we completed the cabling of the following components on the IPATSiA bench:

Flip Mirror — Beam Injection Control
A flip mirror has been cabled to allow injecting or blocking the CO₂ beam on the bench from remote.
It is accessible from the VPM under: R&D → Relay_2 / CH1 (see Fig. 1).

It would be useful to acquire it in Data Display in order to monitor the transitions from 0 to 1 and from 1 to 0 — i.e., open to closed and closed to open.

PT100 — Laser Temperature Monitoring
A PT100 sensor has been installed to monitor the temperature of the CO₂ laser.
It is connected to channel 2 of slow monitoring module 24, and the corresponding data channel is:
ENV_IPATSIA_LAS_TE.
Power Meter — CO₂ Laser Power Pick-off
A power meter has been connected to monitor a pick-off of the laser power injected into the ITF.
The measured value corresponds to 1/5 of the actual injected power.
The corresponding channel name is: IPATSIA_PWRLAS (see fig.2).

After that, we encountered some issues with the thermal camera:
it stopped working properly, and we had to dismount and remount it in order to restore functionality.

During this operation, the ITF unlocked, and no further time was available to continue with the planned activities.

We reclosed the bench and powered off all systems.

Images attached to this report

67353_1753221166_Screenshot 2025-07-22 alle 23.52.33.png

Comments to this report:

nardecchia - 11:04 Wednesday 23 July 2025 (67355)

In the previous entry, I mistakenly wrote:
“The measured value corresponds to 1/5 of the actual injected power.”

This is incorrect. The correct statement is:
“The measured value corresponds to 5 times the actual injected power.”

mwas - 20:53 Wednesday 23 July 2025 (67360)

Yesterday when the interferometer was in LN2 I have realigned EDB OMC locking on 56MHz USB maximizing the transmitted power and then fine tuning by minimizing the beam jitter peaks. Most of the realignment was in TY.

Put a continous scan of the OMC EDB with frequency 0.002Hz, amplitude
0.5 degree, and starting point at 23.27 degree (about 0.1 degree below
the 56MHz USB in steady state)

Starting from 16:26 UTC the scan is with stable parameters (but may
not have a stable average temperature yet, so with drifts from one
sweep to the next)

The scan is fast and non-linear, so mode identification will need to
rely on peak counting. As a reference pattern there is the two close
relatively bright peaks of the 56MHz LSB and the carrier order 1
mode. It Happens around 23.45 degrees for upgoing scans.

Figure 1 shows the time series of the scan

Figure 2 wraps it around in temperature, with one color per scan, counting only the odd scans (as the FSR looks different for upgoing and downgoing scans due to the lag in temperature between the thermistance and the OMC itself). The pair of order 1 mode and 56MHz LSB is visible at ~23.47 and ~23.73. The time in the legend denotes the time of the beginning of the stretch of data shown.

Figure 3 shows the same for the even scans, the order 1 mode / 56MHz LSB pair of peaks is visible at ~23.52.

Many of the modes are stable in amplitude, for example the mode order 3 is shown on figure 4.

I will launch the same continous EDB OMC scan during the next IPATSiA shift, so that we can monitor if some of the HOM change in amplitude significantly. The data here can serve as a reference point for comparison, to check if a mode is normally stable in amplitude or not.

/users/mwas/OMC/EDB_OMC_fast_scan_20250722/EDB_OMC_SCAN.m

Images attached to this comment