After the work on the Injection we have tried to recover the full lock of the interferometer. At the beginning we ahd problems engaging the SSFS, but looking at the Metratron init file we saw that the gain from the DSP loop was at 5 instead of 10, as usual, so we tried putting it back to the old value and it seemed to work. However, we started having problems because the MICH loop opens and the SSFS opens as well because B4 photodiode explodes.

After we had problems with the arm cavities which would unlock regularly due to a strong wind (~ 40km/h). We tried reengaging the marionetta reallocation on the arms, and it seemed to work with the arms, but it does not fix the problem of MICH. Also the drift control of the west arm seemed to send the cavity in the wrong direction and so Valerio discharged the integrator and the situation seemed to be improved.

Figure 1 shows an unlock on the moment that the SSFS is turned on, but the MICH lop unlocks even before the switch SSFS is on. This unlock seems quite systematic, and we have tried to figure out if in Metatron there is some command that might explain this behaviour without success. We hope that the next shifters might be able to find the cause of this misterious unlocks.

We leave the two arms locked, the correct gains for the SSFS and the marionetta reallocation on. During this shift we have seen that decreasing the gain on the SSFS slightly (30-25, 10-7) might help the lock, to be tuned if some problems appear.