Attached is a spectra of ITMY and ETMY optical lever with ISI blends in two different configurations :
BLUE : Tbetter on both stages and for every DOF (except for Ry which stayed on Tcrappy)
PINK : Tcrappy on both stages
The sensor correction on stage 1 was running during the measurement for both ISIs.
There is no major difference in the YAW spectra (bottom two plots) since Ry stays in Tcrappy, but the difference can be clearly seen in Pitch (top two plots). Tcrappy improves the microseism (~.1Hz) but gives less attenuation at the sus resonance frequencies (~.5Hz).
The reason we started looking at this is that we were bothered by the large (order of 1 urad peak) fluctuations at around 0.14Hz. The microseism is a bit higher today that it was when Rich was here designing Tbetter, it has been around 5e-5 decaum/s most of the day, (the upper dashed line on the 0.1-0.3 Hz PEM FOM) We are also running Tcrappy +sensor correction on the xarm, with OpLev damping as well.