Attached is comparison of the LSC FF drives before the HAM1 vent (reference traces) and today (live traces). The first time we noticed the roll mode ringing was around June 11, one of the first days we were back into observing after the HAM1 vent (84982).
It doesn't look like there is significantly any difference in the drive between 10-20 Hz for any of the feedforwards. I have already previously checked the filters for high Q features around 13 Hz that might drive the roll mode and there are none. Sheila previously noticed that the roll mode started to ring up after the SRCL and PRCL feedforwards were engaged (87690).
We did a comparison of the FF drives before and after Tuesday, posting here for reference:
The first three are from two days ago with overall MICH FF gain =2, the last three are from earlier today with MICH FF gain =4.
The forst three are from NLN, the second three from low noise length control this morning when we had the MICH FF on.
