SudarshanK, DarkhanT
We were using 137 degree of correction factor on kappa_tst on our time varying parameters calculation. (alog 21594). Darkhan found a negative sign that was placed at a wrong position in the DARM model which gave us back 180 degrees of phase. Additionally, Shivaraj found that we were not accounting for DAQ downsampling filter used in ESD Calibration line. These two factors gave us back almost all the phase we were missing. There was also an analog antialiasing filter missing in the actuation TF that was applied in the new model. After these corrections, Darkhan created the new upated epics variable. These epics variable are committed at:
CalSVN/Runs/O1/Scripts/CAL_EPICS
Using these new epics variable, kaapas were recalculated for LHO. For, LLO these epics variable doesnot exist yet. The new plot is attached below. The imaginary parts of all the kappa's are now close to their nominal values of 0 and real part are few percent (2-3%) from their nominal values of 1, which is within the uncertainity of the model. Cavity pole is still off from its nominal value of 341 Hz but has stayed constant over time.
The script to calculate these time varying factors is committed to SVN:
LHO: CalSVN/aligocalibration/trunk/Runs/ER8/H1/Scripts/CAL_PARAM/
LLO: CalSVN/aligocalibration/trunk/Runs/ER8/L1/Scripts/CAL_PARAM/
Recall that Stefan made changes to the OMC Power Scaling on Sunday 13 September 2015 (in the late evening PDT, which means Sept 14th UTC). One can see the difference in character (i.e. the subsequent consistency) of kappa_C after this change on Sudarshan's attached plot. Once can also see that, for a given lock stretch, that the change in optical gain is now more that ~2-3%. That means that ~5 [Mpc] trends we see on our 75 [Mpc] the in-spiral range, which we've seen evolve over long, 6+ hour long lock stretches, cannot be entirely attributed to optical gain fluctuations as we've been flippantly sure of, and claiming. However, now that we've started calculating these values in the GDS pipeline (LHO aLOGs 21795 and 21812), it will be straight-forward to make comparative plots between the calculated time dependent parameters and every other IFO metric we have. And we will! You can too! Stay tuned!
Just to drive the point home, I took 15 hours' worth of range and optical gain data from our ongoing 41+ hour lock. The optical gain fluctuates by a few percent, but the range fluctuates by more like 10 %.
