jeffrey.kissel@LIGO.ORG - posted 09:33, Monday 13 February 2012 - last comment - 16:06, Monday 13 February 2012(2212)
H2 SUS ETMY -- So y'all can see what I see
Since it's clearly frustrating that we can't move forward with the H2 SUS TMSY installation, I wanted to show what's going on with the TOP to TOP transfer functions of H2 SUS ETMY, (Main Chain [M0] data I took this morning) so people understand why I'm holding up the show. I don't have an answer yet, but these are the plots at which I'm staring to try and glean what's going on -- suggestions are welcome!~ I'm still taking data on the reaction chain -- will post when I have that data. The first attachment (allquads_120213*.pdf) is MAGENTA, is current (2012-02-13), "first light" monolithic ETMY data, compared against - BLUE A model of the monolithic main chain (fiber). - ORANGE H2 SUS ITMY's "first light" data (2011-11-19) -- Mated w/ BSC-ISI, First Monolithic Results (Fully Laced), M0 F1 poorly aligned/ratty. M0 R and M0 V not measured because of bad M0 RT. - BLACK H2 SUS ITMY's latest and greatest (2012-01-10), phase 3a approved, in-air, post-cartridge install data. The second attachment shows only the current data, but in more detail (and with regrettably more busy plots), specifically cross coupling and OSEM basis response to the EULER drive.
Non-image files attached to this report
Comments related to this report
Here's the R0 transfer function results (same color coding as above). With this data, Brett and I have managed to convince ourselves the the two chains are coupled in some way. After phone conversation with M. Barton, B. Bland, T. Sadecki, B. Shapiro, and myself, our best guess is that because the reaction chain UIM stage is "pretty severely rolled, and too high by millimeters," that the UIM flags are the coupling point. Another possibility is that the Top Blades' clamp bolts (those that secure the blade to the launching clamp) are interfering -- the top plates of the top mass overlap, or perhaps more accurately: where there's a cut-out in the Main Chain plate that exposes the Main chain's blade spring bolts, the Reaction chain's top plate overlaps that cutout. This hypothesis is supported by comparing the main chain and reaction chain TFs -- you'll see that modes have bifurcated in similar ways, and even some of the high frequency modes (e.g. in V and R) have bifurcated at the same frequency, but in exactly opposite amplitudes in each chain's set of TFs -- implying that were seeing the same physical mode in both chains, which are slightly different in frequency because of the two different chain types, show up in each other's dynamics. Betsy and Travis are down at the end station now investigating, where one of the first things they will do is try to lock up the reaction mass such that it is entirely free of the main chain, and we will then remeasure the main hoping to confirm our hypothesis. Then (of course) the next step is to figure out the why the reaction chain is so screwy....
Non-image files attached to this comment
Found it. The R0 UIM Left Blade Clamp screws were grounding on the bottom of the M0 UIM left top Plate. The roll of this chain just bit us again... We're going to drop the left side of R0, giving up some barrel-barrel centering (adding sideshift to the ERM) of the test mass to ERM. As well, the height of the ERM may go a bit low. Recall, we had worked towards "fixing" sideshift, height, and roll. Looks like "fixing" was the wrong thing to do.
For the record, we removed 2mm of shims at the left Top Stage Blade tip, lowering the left side of the R0 chain. There is 1mm left.
Preliminary Results look encouraging!
Attached is a quick before vs. after comparison between the two degrees of freedom that should be most decoupled -- Vertical and Yaw -- for both chains. Both show signs of significant improvement. take the measurements with a grain of salt -- flags are not yet centered, and there's ~half the averages than is normal ('cause we wanted the info faster).
Betsy and Travis are cleaning up now (re-aligning lower stage flags, etc.), and then I'll begin a full suite of measurements when they're finished (either tonight, or early tomorrow morning).
Non-image files attached to this comment
The source of the interference between the chains is the screw head touching the underside of the plate near background.
Images attached to this comment
After dropping the left side of the reaction chain by 2mm, you can now see a gap above the reaction chain screw heads and below the horizontal plate of the main chain UIM.
Images attached to this comment
