After the replacement of the LNFSs to the configuration that was in use last Monday afternoon, we reverted the automation configuration files to the svn snapshot in use at the time , in order to have a usable starting point.

We then proceeded to examine all steps of the lock acquisition from DRMI_1F onwards. We did notice some changes also at that stage, in terms of gains and demodulation phases. As usual, the 3F step was the most impacted.

Then we moved to the CARM/DARM handoffs to the IR, and the following STEP1/2/3 states of the CARM offset reduction, which had to be tuned more heavily.

We consider the recovery relatively reliable up to STEP3, with the following observations:

• MICH is apparently the loop giving more trouble in terms of stability and unlocks; it is also the one that easily gets to higher corrections (also in quiet times), hence the first one to lose control
• PRCL shows downgoing trends at each lock (in terms of UGF) that can be compensated up to a point with the loop gain; the situation is the same in subsequent locks;
• the engagement of DARM back on the IR is statistically not robust, although the loop configuration looks ok; tomorrow we should check better is something is not working of if the weather conditions had some impact (although they were not particularly bad);
• DIFFp has not been checked, and it is now disabled in STEP3 as we wanted not too many things moving at the same time.