Today we looked at Hanford's RefCav FSS OLG.

Results

The RefCav UGF is ~300 kHz.  The raw data is posted in OLGTF.txt, but the magnitude has to be scaled up by 9.65 dB to account for the inverting op amp between IN1 and IN2, as shown in the LHO TTFSS box schematic (DCC S1107453).

Unlike Livingston, our FSS is still important for our frequency noise suppression.  More to come on the frequency noise budget for the IMC and RefCav.

The TP10 measurement is also posted.  This is a measurement taken from TEST2 to TP10 in the TTFSS schematic, essentially probing the Fast (PZT) path, hitting the common gain and fast gain sliders, two poles, and a notch at 242 kHz.  

We hope to get a proper crossover frequency measurement soon.