The first attached plot shows the B5_d2_ACp channel comparison before and after the mirror replacement (different periods wrt the bas entry). The peak height has been normalized to have an easier comparison of the width of the peaks. As expected the frequency of the NI drum mode is similar for the old (red) and new (green) mirror (less than 1Hz of difference, compatible with a temperature variation of one or two degrees). Also the width is similar ... but the dark fringe SNR is needed to have a correct evaluation.
The butterfly mode is difficult to detect in the B5_d2 channel because of the low SNR. The second plot show the region where is expected to find that peak for the NI. In the monolithic suspended mirror there is a strange structure (maybe te mirror was strongly excited during that period).
Finally the third plot shows the drum mode frequency region (17 March) and again the frequencies are where we expect them.
