Because I suspected electronics noise in HAM4, Richard and Dave power cycled the HAM45 computer and rack. When I tried to recover the ISI, it still tripped, so I took some open loop measurements. In pretty much all dofs there is a new (at least compared to the original measurements from 2014 that we used to design the controllers) feature at ~52 hz. First attached plot is the open loop measurement for the X dof I took today, the lump at the vertical cursor is the new feature. Second attached plot is the design plot from 2014 This feature is eating up all the phase margin at this frequency, hence the table is unstable. Looking back to my measurement from the November closeout of this chamber, the feature is visible in those tf's as well, but it's kind of small, and there are other features in the neighborhood that are due to HEPI that go away when HEPI is fully unlocked. So far the table is stable with the lower UGF "medium" isolation filters, but we lose some performance between 1-10hz. In order to run for now, we have to pause the SEI_HAM4 guardian and use the ISI and HEPI guardians separately to manage the seismic components in this chamber. I think I have all the data to redesign the loops to accommodate the new feature.

There's also the matter of 10 degrees phase margin...