Today I implemented band-pass damping for 0.15 Hz L motion in ITMX.
This filter reduced the RMS in L seen by TM LEN oplev by a factor of 2.
This damping uses a feedback from BF L to BF L.
See the following spectra and time series.

-- Memo:
- filter shape: butter("BandPass",2,0.08,0.30) zpk([0],[],1,"n")butter("LowPass",2,10)gain(-4000)
- This filter is engaged by Guardian (only for ITMX) when entering TWR_DAMPED state.
To engage such a filter only for ITMX, I editted TYPEA master guardian and typeaparams.