The purpose of this afternoon's shift was to restore lock acquisition with the usual SDB2 sensors and work on the automation for the slow shutter; these are the results and the changes with respect to the past:

• the new slow shutter is handled by the DET_MAIN Metatron node; this is still operated manually until the procedure and the lock acquisition are validated;
• we restored the usual MICH fringe signal which uses B1p_DC with no issues;
• while in Recombined we did the first tests/adjustments for closing the shutter (state SHUTTER_CLOSED), and everything was working; since this shutter is closed, we do not close anymore the individual shutters for B1s1/B1s2/B1, so that they are ready to close later on if needed avoiding the risk for them to be stuck in-between transitions and not close quickly enough;
• nothing to report along lock acquisition before the realignment of the PRM but that the 7 Hz vertical mode seems to excite more easily than before;
• once the PRM is realigned, the vertical dampers for such mode are engaged as usual and their effectiveness is still good;
• we had issues at first going to dark fringe, but in the end we succeeded and now the transition is very reliable, with just one unlock among many attempts, after the following operations:
  • minor tunings of a couple of longitudinal gains (SSFS & PRCL);
  • re-tuning of the B1p_56MHz demodulation phase;
  • dis-engagement of the vertical dampers while going to dark fringe, as they were causing big oscillations on DARM; they are engaged again at the end of LOCKED_PRITF_DF;
• throughout the shift we managed to get to LOW_NOISE_1 just once (and for a brief time); the main issue seems related to the boost filter for the SSFS, which has some problem we did not understand so far, to be investigated;
• the engagement of the DIFFp loop seemed to work, as it lasted a few seconds, but probably the mixed driving does not when the COMMp is not closed, and I forgot to comment that out;
• both the B1p_PD1 shutter and (later) the slow shutter were opened in dark fringe before LOW_NOISE_1, even with the alignment loops still open; the logic seems to work fine and the thresholds have been tuned;
• the demodulation phase for B1p_QD2_56MHz was (hopefully) tuned, but the single test we managed to do is not conclusive; the B5_QD2_56MHz phase still needs to be tuned.

For these reasons ALL the alignment loops are commented in the Automation, as well as the change of the driving for the DIFFp; on the other hand, the new scheme for the vertical dampers is already in place.