On Tueday, the End Y HEPI Servo Computer Power Supply was ground bounded, and the Accumulators on the Fluid system were charged, alog 16907.  On Thursday, I removed the ground strap for ~6 hours to understand if the coherence reduction seen was from the Ground bonding or the Accumulator Charging.

Conclusion: the bulk of the improvement comes from the Accumulator charging.

While there is a minor amount of increased coherence seen in Z and HP it isn't near the amount seen before the Tuesday work especially HP--See the reference traces on 16907.  Of course, most of the ultimate noise reduction comes from Jeff's tuning of the controller pushing the ugf down to 10mhz but charging the accumulators and well grounding the servo computer are important too.

The attached plots have the reference traces as post Tuesday work and the current traces are beginning at 1730utc 26 Feb.