J. Kissel

The CAL-CS front-end model is where the infrastructure for the calibration (i.e. inverting the DARM actuation function such that a waveform calibrated into strain can be injected into the DARM loop in the correct DARM [ct] units), so I'm looking at what I need in order to fill the one filter bank that we'll use for this inversion. I've used the DARM open loop gain TF model (described in LHO aLOG 17951) to demonstrate (a) what the actuation function model looks like and (b) how simple it *could* be to invert it.

In summary, we can get a ~5%, 3 [deg] frequency-dependent fidelity of the full model between 10 - 2000 [Hz] if we simply use a
1.03e-13 [m/ct] * (1 [Hz] / freq)^2
model for the magnitude, and a
-1 * 176 [us] delay
model for the phase. Huh! 

Recall that 1.03e-13 [m/ct] has a +/- 26% uncertainty because we're as of yet unable to discern the difference between optical gain fluctuations and ESD strength changes from fluctuations in charge (again, see LHO aLOG 17951 for discussion).

I'll discuss with the LLO injection team to see what they'd implemented for ER6, where they've rolled off the *inverse* of this filter, and discuss the path forward, so we can get something installed by the mini-run.