Today's quest to increase the bandwidth of the FSS involved the following steps:

• removing both notches in the EOM path
• re-installing the original notch of 220 uH and 150 pF
• changing out the 150 pF cap for a 120 pF cap
• restoring the TTFSS back to its original configuration

The file NONOTCH1.TIF is the open loop transfer function with no notches installed.

Unfortunately the NPRO noise eater was oscillating for this measurement.

The file NONOTCH2.TIF is without the NPRO noise eater oscillating.  One can see

the ~760 kHz resonance that the notch was installed for originally.

The file 150PF.TIF is the open loop transfer function with just the one notch installed.

That notching being the one with 220 uH and 150 pF.  The unity gain frequency is a little

over 300 kHz here.

The file 120PF.TIF is the open loop transfer function with the 150 pF capacitor replaced by

a 120 pF capacitor.  The rationale being moving the notch frequency higher might still attenuate

the 760 kHz resonance enough and allow the gain to pushed a little higher.  This introduced

either another resonance or did not sufficiently suppress the 760 kHz one.

The file RESTORE1.TIF shows the open loop transfer function with the TTFSS restored to its

original state.

For all measurements the reference cavity transmission was ~1.45 V, the fast gain was 18 dB

and the common gain was 22 dB.

Ed, Peter