The PMC length noise no longer shows up in DARM. Even for the 1 kHz and 4 kHz peaks there is a factor of a few safety margin. Increasing the PMC gain slider from 0 dB to 16 dB (actually from 0 dB to 12 dB), we see no significant change in DARM. The 4 kHz peak starts touching the noise floor with a 0.3 coherence.
This means that the increased coherence between DARM and jittery peaks after the increase in the modulation depth and associated PMC changes (alogs 31095 and 31203) is a mystery.
We are running about 8dB higher PMC length gain than before as that's the lowest we can go with the current electronics with higher modulation depth. It would be interesting to see if modifying the electronics will do anything.
(In the attached, IMC_F and IMC-WFS traces are scaled arbitrarily such that it's easier to make an eyball comparison.)
