J. Kissel

I re-measured the broadband (CAL-DELTAL_EXTERNAL_DQ / CAL-PCALY_RX_PD_DQ) transfer function, and found it slightly different from the 2022-07-22 measurements (4% low below 20 Hz, 2% higher from 65 to 200 Hz). 

As such, and suspecting the root cause being the DAC upgrade of the penultimate stage, I nudged around the same scalar factors of the actuator I fudged the calibration with last time and thus I changed the calibration again. I found I needed to 
    - Change the PUM scale-factor from 1.01 to 1.05, and
    - Change the TST scale-factor from 1.045 to 1.07
to restore the systematic error to the levels of the previous fudge. Given how many times I've said fudge already, and that I need to change both the PUM and TST stage, you know that while these scale factors have made the systematic error transfer function similarly flat it doesn't make sense physically. But, we'll solve that mystery later. For now, the calibration is now as good as it was prior to the PUM DAC change.

In order to "solve that mystery later," I've gathered the 8 transfer function sweeps of all components of the response function. I'll post details about those measurements in the comments.

Attached are screenshots of the current new values of the scale factors.

Also attached is the DTT measure of the transfer function (which still has an old version of the corrective transfer function). 
    - Red trace is now, after sweeps and after fudge tuning.
    - (REF2) Blue trace is today, but before today's fudging, showing the ~4% frequency dependent error (~2% change) that has accrued since we last fudge-tuned the calibration on 2022-07-22
    - (REF4) Gray trace is just after fudge tuning, today, but before all the sweeping began a few hours ago. 
    - (REF4) Black trace is the 2022-07-22 measurement after the first fudging.
I took "post tuning" broad band injections twice several hours apart as a crude check to see if the IFO's *actual* time-dependent correction factors (most likely the sensing function optical gain or cavity pole) have changed. Because they report the same answer several hours apart leads me to believe that the TDCFs were stable across this period. It's a crude measurement (you'd see this more clearly if the PCAL had the range to drive out to higer frequency, but it does not.)