Today, we performed the mode matching measurement towards the ITF in two cases: with the free swinging technique and with the green scan:

- Measurement of the mismatch with the free swinging technique with nominal power:

West - GPS: 16:40:25 - 1.9% (Fig. 1)

North - GPS: 16:39:30 - 2.8% (Fig. 2)

- With the green scan, we have similar results (NA - 3%, WA - 1.5%, Fig. 3).

We also meant to measure the mismatch reducing the power with IPC2 in order to simulate the same thermal lens as we have in CARM NULL (so, reducing from 100% to 12% the power on IPC2). However, after perform the power reduction, we ended up with 6W entering the ITF and with this value was not possible to relock the ITF, requiring a very long work to retune several ISC loops. So, we decided not to continue in this direction. 

Since the West Arm presented a acceptable value of mismatch, we decided not to move the lens (L1) to reduce the mismatch as these values can be compensated with the differential DAS.

Afterwards, we also tried to tune the Farday Isolator on SIB1. For that, we reduced again the power going towards the ITF with IPC2, taking as reference B2 (from 12.5mW to 2.5 mW). Then, we followed the same procedure descbribed in #61943, moving the waveplate of the FI on SIB1 (minirack of CB) and giving some kicks on PR_F0_Z in order to minimize the signal INJ_FMOD_56MHz_mag. We moved the waveplate on both directions but we concluded that the best isolation was achieved with the initial value. Therefore, we brought the waveplate back to the original position (Fig. 4).