J. Kissel, T. MacDonald

We measured a final exploration of ETMY HEPI today to identify the exact mode shape of the 8 [Hz] resonance, given that there were still some ambiguities in yesterdays results. Peppering the piers, boots, housings, crossbeams, and support tubes with hit points, we've nailed it down. The bending point is the crossbeam foot (D020195, see green highlighted part in 2014-08-19_HEPIBoot.pdf attachment) -- the connection point of the suspended stage with the Euler springs. Inward of this foot, everything else is moving in concert -- the crossbeam, the support tubes, and everything else inside the chamber.

We took two sets of measurements, one involving tons of points on one pair of piers and crossbeam (that's where we identified the foot as the problem, see HitPattern.pdf), and the other with all four cross beams involved focused more on the crossbeam foot -- as many data points into which we could squeeze the hammer.

The "single_side.avi" is the first measurment with only one crossbeam system, and the four "*_both.avi" show the measurement with the whole system.

Check out all the visual aides, and be sure to loop your video, since the B&K software doesn't export more than once cycle.