Sheila Jenne

We made some quick intensity noise injections using the second loop, and jitter using the IMC PZT.  A first look at the data suggests that several of our peaks in DAM which show coherence with the ISS sensor are due to jitter coupling, rather than intensity noise. This menas that we can't fix these peaks with more ISS gain, but we might be able to do something by changing alignment offsets.

The attached plot shows the noise in DARM (taken with MICH FF off, which causes extra noise at 100 Hz), a projection of intensity noise in DARM based on the ISS PDs, and a projection of the jitter noise in DARM based on IM4 trans yaw. I"ve used a coherence cut off of 0.5 for the transfer function measurements used here.  

Still to be done:

• pico IM4 trans so that it is centered in pitch and we can get a better pitch jitter measurement
• Cut out frequencies where IM4 is sensor noise limited (this probably won't affect the peaks of the jitter projection.)
• Repeat with MICH and SRCL FF on to see what we can learn about the noise at 100 Hz.