DRAFT
ITF found in LOW_NOISE_3 and SCIENCE Mode, AUTOSCIENCE On.
UTC 9:09 COMMISSIONING Mode set for CEB viewport tapping (Tringali, Fiori);
UTC 10:45 Unlock. Relock to LN3 achieved at 11:26 UTC.
UTC 11:31 Unlock. Relock failed at first attempt (LOCKING_CARM_NULL_1F). Relock failed at second attempt (LOCKING_OMC_DARM_B1_PD3). Relock failed at third attempt (LOCKING_CARM_NULL_3F). At fourth attempt the sidebands were unbalanced and B1p was 0.035, once the CARM_NULL timer was over i lowered MICH_SET to 30 and added +1.8 urad to SR TY, the OMC was not still able to lock, I contacted DET oncall with no answer and then I contacted Was, activity ongoing. Another attempt was performed adding +2 urad ST TY ensuring B1p was in the correct range, ITF Unlocked at ACQUIRE_LOW_NOISE_2. ITF Unlocked one more time at ACQUIRE_LOW_NOISE_2.
ITF left in CARM_NULL_1F.
The OMC was not locking due to a change in sign of its error signal. This must be due to the reconfiguration of the EDB DAQ box:
2025-11-28-11h31m04-UTC info masserot Reconfigure EDB_DBOX_DetLab2 in SDB_EDB_dbox_rack
After changing the sign of both photodiode error signal (as usual for this type of problem), the OMC could lock. But we had afterwards two unlocks in ACQUIRE LN2.
Figure 1 shows one example, it was odd as the OMC PZT correction is suddenly diverging from zero. Looking at the log of the automation it corresponds to the time when the OMC goes to low noise mode, which means use B1 PD2 instead of B1 PD3 as the error signal. And comparing both error signals they go in opposite direction.
So this time only the sign of B1 PD3 error signal change, while the one of B1 PD2 did not. This is new, both were changing together in the past ~5 times I have seen this problem.
After changing the sign of just the B1 PD2 error signal the lock acquisition could continue to LN3. Note that the B1 PD2 phase is still quite bad, as the I and Q signals are equal, so it is off by ~45 degrees. But I haven't touched it as I am not sure in which direction in needs to be changed.
