J. Kissel 

Changing the clock-rate and PID parameters of the corner station's HEPI Pump Servo (LHo aLOG 16796) has removed most of the noise from the corner station SEI systems, while still maintaining a 10 [mHz] UGF loop suppression on the pump pressure (for design, see 16782). 

Notes on the current impact on chamber performance, compared with what was measured when the problem was initially discovered (LHO aLOG 16239):
- The Beam Splitter remains as the worst chamber, with coupling in X, RZ (as measured by the ISI ST1 T240s) and HP (as measured by the HPI L4Cs) between 5-50 [mHz], 5-50 [mHz] and 50-150 [mHz], respectively. Even still, the amplitude of displacement for these DOFs has been reduced by a factor of a few, with the best reduction being RZ from 20-90 [mHz] where the amplitude dropped by a factor of 5 -- should be great for yaw alignment drift of the BS.
- For all HAM chambers, any coherence, in any DOF -- except for HP -- has disappeared or, at least it's below the HEPI L4C sensor noise floor. 
- For the BSCs, all DOFs but for what's mentioned above, show little coherence even with the T240s, indicating we're also not limited by this noise there either. 
- Of the tanks that still show coherence with HP, their noise amplitude has also reduce by factors of 2 to 3, reducing the coherence by similar factors. HAM2 is the worst offender for HP, with still obvious coherence between 0.1 [Hz] and 1 [Hz].

I think we've got what we can out of the pump servo's stinky computers, tuning the parameters to account for its inherent badness -- and got factors of 2-3 reduction in ISI input noise between 10 [mHz] and 1 [Hz] motion. Any further efforts on improving the remaining coupling should be dedicated to installing a better pressure readout system.

For the attached plots, I've focused on the DOFs that still have some coherence, and new information where I've gathered T240 information. For the entire collection of plots showing all DOFs for all tanks, check out .pdf files tagged with the date 2015-02-20 in the 
/ligo/svncommon/SeiSVN/seismic/HEPI/H1/Common/
folder in the SeiSVN.
The DTT template used to make the thousands of plots can be found here:
/ligo/svncommon/SeiSVN/seismic/HEPI/H1/Common/2015-02-18_H1HPI_PumpControllerNoise.xml

Will post similar results for the ETMs tomorrow -- I expect the same goodness there.