I set up the BS bounce mode damping loop, tested it and confirmed that it works very fine. One should be now able to lower the peak height of the mode by a factor of 10 or so in a minute.

During the calibration activities in this evening, I ran into a problem with the MICH locking where I was not able to lock it. It turned out that the bounce mode was too high so that the length control saturated the DACs on the BS suspension. I guess that the mode was excited due to several times of locking attempts as I was trying unusual locking settings for the calibration. The below is a screen shot of the bounce mode damping filter:

The design process was essentially the same as similar to what Jeff described for LLO's violin mode damping loos (LLO alog 15000) but I did not try to drive it as hard as DAC saturation. I am leaving the filter enabled for now. If someone find this filter doing something bad, please feel free to switch off at its output (because turning off at the input seems to create a huge impulse response). I did not explore the gain so much.