[Sheila, Jenne]

While looking at our locklosses today, Sheila noticed that we are using up way more DAC range than is appropriate for the SRM while we are locked using the 3f signals.  Looking at a spectrum, it's all high frequency sensor noise. 

I lowered the frequency of the cutoff from 300 Hz to 200 Hz.  This eats 4 deg of phase at the 40 Hz UGF, so should be plenty fine according to an old OLG measurement Sheila found.   We could / should improve this even more, but (a) it's better than it was before, (b) this is only really a problem while we're on our noisy 3f sensor, and (c) we don't want to get too much more crazy without taking a fresh loop measurement, which we don't want to spend commissioning time on right now.

Attached is a set of spectra showing the old SRM output (blue) and the new (red).  Don't mind the bounce mode in the red spectrum - damping wasn't on yet during this measurement.