Took spectra of the IMC length control signal with different control configurations for HAM2-ISI and HAM3-ISI. In comparision to measurements with damping only, most improvement in the 0.5Hz-3Hz  range were seen with Level 2 isolation and 100mHz Sensor Blend on translational DOF, and 250mHz Sensor Blend on rotational DOF. 

Both HAM-HEPIS were locked, and control configurations (ISO level, and blend) are systematically the same for both ISIs. One should note however that level 2 controllers used here are specific to each chamber. I will try having the exact same filters on both ISIs to limit the differential motion injected later.

I haven't managed to calibrate these curves yet. I am working on it and it should come soon.

These measurements were performent yesterday, with the IMC locked using Matt's new MC2 M2-M3 cross-over. This recent modification of IMC controls allow keeping the IMC locked, even with the level of differencial motion injected at low frequency by the Lv2 ISO /w 100mHz X,Y,Z blend & 250mHz RX,RY,RZ blend configuration. The seismic isolation is then optimal, in comparision to what we obtained so far, in the 0.5Hz-3Hz  range.