BrianL Hugo JimW Hugh

When I collected HAM4 TFs 3 Sept, a deep zero here seen in the first plot as compared to the second, caught our eyes and it looks to be a problem possibly in the HEPI Isolation loop.

Here is the transverse controller from HAM3 4 & 5 in the attached.  The HAM3 controller is the top graph, appears to be done by hand and at a UGF of 2hz.  The middle graph is HAM4 and are the HAM HEPI Generic Loops developed by Hugo w/a ugf of 5hz and implemented by Hugh.  The bottom graph is HAM5 and again like HAM4, are generic and installed by me.  It is surprising that the HAM4 looks more of an issue than the very sharped peaked HAM5; but, the shoulders of the peak are higher at the ISI zero for HAM4 and the zero at HAM5 is below 6hz rather than above.  That said, the HAM5 HEPI controller is obviously equally problematic given this gain peaking.

Bottom lines--Generic loops while easy to install, should be carefully checked

Is a 5 hz loop best, warrented, needed?

Post HEPI turn-on ISI TFs should be collected and thoroughly checked.

Apologies to my above co authors--they have not been consulted for this entry.