I noticed this morning (through the Detchar pages, very sad that last nights SEI data isn't available) that the HAM5 ISI has not been doing well since about the time HAM6 vent activities started. Sadly this casts some doubt on the feedforward data I posted the other day, so I re-evaluated the performance at HAM4 while I was digging into HAM5. My first image shows the difference between HAM's 4 & 5 in the Y direction, all the other DOFs look similar. Second image shows the rotational dof's of HEPI L4C's on the two chambers, and HAM5 sees al lot more motion than HAM4 (dashed lines are HAM5, solid are HAM4). The translations are messier, (third image) but still seem to indicate more motion at HAM5. Hugh reports finding a few mechanical contacts at the chamber while he was working on HAM6, so I'll wait to panic about HAM5 until after that mess is cleaned up. Jeff is filing a report with FRS on this.
On to doing a better evaluation of RY feedforward on HAM'S : the fourth image shows the healthy HAM4 RY feed forward, dashed lines are off, solid are on. Fifth image shows that turning RY FF on has not spoiled the X performance.
Last two images show HAM4's Y and Z feedforward performance, with the same dashed/solid off/on convention.
Opened FRS ticket #3240.
Keep in mind that the mechanical loads on the HAM6/HAM5 vacuum chambers have drastically changed. Prior to the vent HAM6 was supporting the 42000 pound atmospheric load applied at the East door but now this load is applied at the septum plate. The septum is bolted hard to HAM5 and coupled to HAM6 through a bellows so this load is now applied to HAM5. I don't know what impact this might have on the ISI but the reactions from the floor have certainly moved. Perhaps local tilt has changed?