During the first week of the run, a gradual degradation of the sensitivity has been evident; today, almost restored the quiet weather condition of the beginning, the horizon was fluctuating from 4 to 5 Mpc, instead of 6-7.
Looking at the sensitivity curve, all the structures linked to the mentioned optimization were clearly involved in this degradation, therefore we decided to operate at the level of the OB position, trying to see if it was possible to repeat the miracle.
Having no possibility to rotate the bench in ty (this is in loop to keep B1_ACq at zero), and obtaining no effect with tx, we moved the bench along the vertical direction: in fact, a certain drift (~100um) was visible in the data in the last week. Going back in the initial position of the sensitivity was clearly improved.
We decided to do something more: other 100 um in vertical, and about 100 um also in x direction (transversal to the beam). We stopped when the noise was sufficiently low, but we are non sure that we reached an optimal position.
