J. Kissel

I've process several sets of data to show results of B&K measurements which characterize the new scraper baffles in HAM3 / HAM4, the MC2 scraper baffle (), the PR2 scraper baffle (), and the SR2 scrapper baffle (), all of which are assembled with viton built into the structure, so we expect very little high-Q features.

Attached are results from all three LHO baffles, in addition to comparing the same DOFs measured at LLO (though, LLO used a laser vibrometer, and only measured the response to 2D excitation in one direction).

It's difficult to make any broad sweeping statements about any of these baffles.
I would have naively expected that the PR2 and SR2 baffles from both sites would have similar resonant features in the comparable excitation + response directions, but they're all different. Similarly, the MC2 scraper baffle shows a different response. I could easily imagine the response being different because of the differing hit locations -- from the looks of pictures, Arnaud / Stuart hit the centers of big surfaces on each baffle (think excitation of drumhead modes of those panels), where Siddhesh and I were hitting the top corners of structures (think excitation of flag-pole modes of the entire structure). Also, the response sites were different between observatories: the laser vibrometer can directly measure (at least one) surface of each baffle, where as the accelerometer bolted to the table picks up ISI table resonances (i.e. the high Q features around 10-15 Hz which are the locked / HEPI cross-beam resonances).

If we're really looking to confirm that these are built identically, and have confirm that *all* resonances are damped to a sufficiently low Q, then we're going to need to standardize our measurements.

For now, all we can do is acknowledge what frequencies we see where, and hope the don't show up in the IFO's sensitivity!

For those who need more detailed information, I attach the data (zipped up in an archive that you'll need to decompress), and the script to process the data to make these plots.
 
Details of the measurements can be found in the following aLOGs:
H1 MC2 / PR2 LHO aLOG 39590
H1 SR2 LHO aLOG 39288

L1 MC2 / PR2 LLO aLOG 36908
L1 SR2 LLO aLOG 37020