[Okutomi with helps from colleagues]

• I measured transfer functions in MN and IM DoFs of ITMX in 40-50 Hz.
• The promissing mechanical peak of 46.6 Hz was found in the transfer function of MN pitch with swept-sine excitation with almost maximum amplitude (see the figure below).
  • According to the model prediction, this peak can be a higher-order mode of the TM chain in pitch (#70).
  • This peak could be slightly observed also in the transfer functions of IM pitch and MN roll.
  • The magnitude of the transfer function is small even at the peak frequency.
  • We can see another peak at ~42.3 Hz.
  • Although the TF measurement with photo-sensors shows good coherence function values, it seems they don't represent the mechanical responses.
• I tried to damp the 46.6 Hz peak with the band-pass comb feedback from MNP to MNP.
  • That attempts were not effective so far.
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