During the last lock segment, we had the Tidal Error messages (X& Y COMM CTRL within 10% of limit). Additionally, noticed on the Striptool on nuc1 that IMC-F_OUT16 was diverging & drifting off-screen (see attached). Ultimately there was a lockloss (could it be related?).
Talked to Hugh while we were locked, and he pointed me to the End Station HEPIs & also to the ISC signals they get. He mentioned they have a limit of 700,000counts. ETMy was moving below -36,000 (this was OK). EX was flatlined at 14,660 (this was ODD). But since both of these were well away from 700,000, we ruled out this being a tidal issue and figured it was something upstream (ISC? PSL?). We'll see how the next lock looks.
The attachment shows how the integrated ALS offsets remain as error point offsets for the IMC-F → UIM offloading.
We should bleed these ALS offsets away once we have transitioned off ALS, and preferrably before increasing the laser power (as this will load CARM by a few microns).
I thought that with EX tidal flatlined, the IMC frequency changes to try and keep H1 locked, but then runs out of range causing lock loss?
Wouldn't that mean the EX flatlined is the issue, IMC_F is just responding?
It seems that during this lock acquisition, there were large offsets remaining on the ALS → UIM offloading filter modules, and correspondingly large offsets on the IMC-F → UIM offloading filter modules (which are used during full lock).
The IMC-F → UIM offloading hit the limit around 15:50:00 Z, causing the tidal offloading to halt. As Cheryl said, this means IMC-F starts accumulating a dc offset to keep the laser on resonance.
