J. Garcia, J. Kissel, B. Shapiro
After unlocking both the QUAD and the ISI, here are the latest results from H2 SUS ETMY. In summary, the chains look good and match other equivalent chains reasonably well, save the details below. My only concern is
- There seems to be cross-coupling, most notably in the M0 Transverse direction (but present in other degrees of freedom *and in both chains*), between T/R at 1.25 Hz, and T/R/P 1.6 Hz.
Other things that are not worthy:
- The upper two Vertical mode frequencies are consistently higher than ITMY by ~2% (for main chain, same SUS but with metal erm for reaction chain). BUT, this would mean an equivalent increase in lower blade stiffness of sqrt(2%) = 0.04% -- by which I'm not alarmed, merely interested, since almost all other instances of SUS project wide have had *remarkably* consistent vertical modes.
- Again focusing on the vertical TF -- Brett identified that we had accidentally left the UIM horizontal center of mass parameter, h1, at 0.005 m instead of the nominal production value of 0.000 m for the main chain, monolithic, 'fiber', parameter set. This offset, when present, (among other things, most notably) creates a cross-coupling of Pitch to the Vertical TF @ 2.76Hz. I've corrected this in the production model parameter set. Further, as you'll see in the attached, ITMY has some of this offset, where ETMY does not (good!).
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For persepective, one should probably start with allquads_120315_H2SUSETMY_ALL_TFs.pdf
Here, I compare 2 chains, 4 measurements of monolithic main-chains, and 3 measurements of equivalent reaction chains.
Main Chain
H2 SUS ITMY 2011-12-02 -- Pre-cartridge install, Floating ISI, After IAS Adjustments, Stiffening Elements + Vibration Absorbers in Place, L1&L2 Aligned
H2 SUS ITMY 2012-02-16 -- Post-cartridge install, Pre-ISI-Shakedown-Fiber-Failure, Floating ISI
H2 SUS ETMY 2012-02-14 -- Pre-cartridge install, after major intra-chain rubbing was relieved
H2 SUS ETMY 2012-03-14 -- Pre-cartridge install, after further UIM flag rubbing relieved, stiffening elements installed, etc (only thing missing is VA, which shouldn't effect anything).
A quick scan through these TFs show that, for the most part, the most recent ETMY measurement matches the best ITMY measurement. In fact, comparing CYAN with MAGENTA, shows that the most recent round of UIM flag adjustment has greatly cleaned up all DOFs measurements.
The only flaws visible are those mentioned above:
- Cross-coupling, most notably in the M0 Transverse direction between T/R at 1.25 Hz, and T/R/P 1.6 Hz.
- Slightly higher Vertical stiffness.
Reaction Chain
QUAD04 2011-11-22 -- Phase 1 approved measurement of H2 SUS ETMY, with metal ERM (on a solid stack)
QUAD03 2012-01-24 -- Phase 1 approved measurment, with metal ERM (on solid stack)
H2 SUS ETMY 2012-02-14 -- Pre-cartridge install, after major intra-chain rubbing was relieved
H2 SUS ETMY 2012-03-15 -- Pre-cartridge install, after further UIM flag rubbing relieved, stiffening elements installed, etc (only thing missing is VA, which shouldn't effect anything).
Here, in the most recent ETMY measurement, the reaction chain looks OK at first glance, but upon closer investigation shows the same 1.25Hz and 1.6Hz modes as the main chain, and the mid-frequency band just looks kinda noisier (though not as bad as 2012-02-14).
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The ALL_ZOOMED_TFs.pdf plot just shows a tighter X-axis for a better look at the details, and the first two attachments show a lot more information (cross-coupling, plus OSEM basis) on the CYAN measurements.
Though it's difficult to blame a particular thing (*sigh* isn't that always the case?), my gut tells me there's still something rubbing between the chains. I know we've been having trouble with UIM flags... Also it's difficult to imagine a scenario where Transverse couples to Pitch...
We'll keep thinking.
