We have a 0.4mm vertical drive on the BS HEPI Vertical Actuators.  Long story but with the HEPI loops open, this platform sags low enough that the IPS are no longer in their linear range and behave poorly giving us tilt coupling.  Our pump station system pressure still has some coherence with the BS platform so I wanted to check if this large drive on the BS Vertical was increasing that coherence.

Bottom line, I'm not sure.  I took a reference coherence look and then lowered the vertical on the hepi loops by 0.2mm and took another set of data.  Attached are the results.   The reference traces are the normal offsets and the current plots are with the offsets reduced.  I'm looking at the T240s on the ISI stage1.  Conclusion, ehh, it all just looks noisy, some places better some worse.  There is a band in the X dof that seems broadly better from 10 to 25mHz but I'm not sure if it is meaningful.  I'll look at the HEPI platform channels rather than just the ISI channels too and maybe I need to drop it the full 0.4mm to really see an effect.