M. Todd, C. Cahillane

We are looking at the RIN in LSC-REFL_A to try and understand if there are some cavity dynamics that can give an estimate of the power recycling cavity mode-matching to the arms (for some more background, see Daniel's alog 70985)

I've made a plot that shows some interesting changes in the REFL_RIN asd as a function of thermal state. In particular I've looked at the asd at 4 different times as we thermalize after locking and stabilize the ISS.

There's some very interesting dynamics around 5-50 Hz. For the HF dynamics, I've also plotted the shot-noise limit based on that time's DC REFL_A_LF power; which I think is the limit in that frequency regime.

I've put both the dtt plot as well as my own plot that used quick_psd.

Next, I would like to model what RIN we would expect in that frequency band and compare to these measurements, specifically if this is intensity noise coupling changes due to mode mismatch changes during thermalization.