In the morning several unlocks occurred which seems were due to 2.3 Hz oscillations. Ilaria did a step back in NE RH. The last unlock was due to the guided tour entering the CEB (!!)

The shift activity started in the afternoon, with the nice lock at 12:30 UTC with BNS range 51 to 54.5 Mpc.

We performed three activities.

Near field magnetic injections at SDB1: South, East and North side. This time the small coil has been positioned using reference markers (Maria and Federico set last week) placed in symmetric locations with approx 1 cm accuracy. From the recorded position of the reference marker (Federico) we can extract the position of the center of the injection coil with respect to the tower center.

Figure 1 shows the sweep injections. It seems that the hrec impact was louder when on the North side,

We noticed that several peaks are excited which can be extracted and compared with tappings and SDB1 shakings data.

Disconnection of the NI mirror coils cables from the relay box (25-min glitch investigation): this did not produce any effect, after the 4 coils were disconnected the glitch timely appeared :-(((... as shown in Figures 2 and 3.

Magnetometer ENV_DT_TURBO_MAG (401 Hz noise investigation): a fluxgate probe was positioned, firstly at a few cm distance from the DT turbo cable behind the VAC rack) and secondly it was placed closer to turbo pump (but practically at a similar distance from the cable). Figure 4 shows the measurement close to the cable (401 Hz peak was about 50 nT/sqrtHz). We notice some other noise structures around 400Hz that are coherent with the DT_MAG probe. Indeed the DT_Mag probe seems to copy the turbo pump cable noise also around 100Hz and all multiples (Figure 5).

Figure 6 shows the measurement closer to the pump (401 Hz peak was about 1nT/sqrtHz). More measurements of the 401Hz magnetic noise will be done during next maintenance.

Details of the actions are reported in the attached file.