J. Kissel, K. Izumi

Kiwamu is making sure the online calibration filtering (currently in the "OAF" model, will eventually be in the "CAL" model) is reasonably up-to-date. In doing so, we discovered that the two ETMs have different damping loop filters installed and ON. Most filter modules are as expected, according to the original, low noise, Level 2.1 quad design (see LGO aLOG 6760). However, in FM3 of the L and Y banks of both ETMX and ETMY, there are filters called "resg1" and "+12dB" respectively. They are ON only in ETMX.

After a little digging down memory lane, we recalled that in attempts to get ALS DIFF up and running last time (see e.g. LHO aLOG 15025), before we lost the arms, we had copied over LLO's damping filters' differences at the time -- described in detail in LHO aLOG 14959. However, as indicated in LHO aLOG 15037, having the filters constantly ON never got captured in any sort of configuration control, because ALS and LSC control was bouncing between using ETMX and ETMY depending on the functional-state and state-of-confusion for each test mass.

We have now turned both FM3's of L and Y filter banks ON, and changed the DAMP_STATE_?_GOOD state to match the current state with those ON. We have not yet captured a new safe.snap in this configuration, but we'll do so ASAP.

A note -- the ITMs do NOT have these "bonus" LLO filters installed, so FM3 is therefore OFF.