E. Goetz, J. Kissel
ECR E1800246

Evan and I are beginning to use the recently upgraded time-dependent correction factor calculation system (installed two weeks ago; see LHO aLOG 44507). MEDM screens have been revamped, and or understanding of the DARM loop model is now complete enough that we have inklings of hope for success. We've been filling in demodulators that are new, and/or that had been lost from name changes, and entering in EPICs records that represent the O3 model for the first time. As such, we want to explore the functionality, so we've turned on one of the biggest changes between O2 and O3 -- the separation of correction factors for the upper stages of the QUAD actuator -- kappa_PU is now kappa_P and kappa_U, so we now have an independent measure of the actuation strength changes for the PUM and UIM stage. Yes, we don't *expect* these gains to change much, but we have been bitten by sudden changes in electronics before (e.g. the PUM driver swap right after New Years 2017 in the middle of O2 LHO aLOG 32799).

You will now see two new calibration lines in the DELTAL EXTERNAL asd -- at 15.1 Hz driven from the ETMY UIM, and 16.7 Hz driven from the ETMY PUM. (and technically, you could say there's only *one*new* line -- we've deleted the DARM calibration line, which used to calculate kappa_PU, so you could consider that moved frequency, not a new frequency).

We retain -- only for a few more days -- the ETMX ESD line 35.9 Hz (will be moved 19.1 Hz), the PCAL line at 36.7 Hz (will be moved to 17.9 Hz), and the PCAL line at 331.9 (will be moved to 433.7 Hz). We want to be sure we can reproduce O2-like results with the current line frequencies that were present in O2 (which which looks like it is only a few days away), and then we'll change the rest.

These line frequencies were determined against several criteria (see LHO aLOGs  44892 and 44590).

The point is that (a) these are below most data analysis group's search band (most start their search at 20 Hz), and (b) we'll likely end up subtracting them anyway, so you won't even see them the GDS-STRAIN ASD for O3.