After Corey and I removed the center of MCA1 (Swiss Cheese), we installed the damping corks on the eye baffle, MCA2 (see figures).

While adding corks, I noticed that the panels on MCA2 did not fit perfectly and bulged out from the frame because the distance between fastening points was longer for the panels than the frames (see figures). This resulted in long stretches of loose sheet metal that vibrated at low frequencies (order of 10 Hz) with large amplitudes and Qs. Hugh had some Class A 1/16” x 2” x 2” Viton pieces associated with ISI table damping that I wedged in between the panels and the frame, giving some damping (see figures). Of course, the best solution would be to increase the size of the holes in the panel so that the fastening would be more forgiving and to use damping washers.

I found a few bulging panels on MCA1 and damped those as well (see figures).

The bulging surface changes the angle and can increase the reflectivity of the panels from the point of view of beam spots (see figures). I checked that the damping pieces wedged between the panel and the frame did not increase the bulges to the degree that it was evident as increased glints in photos from the point of view of beam spots (see figures).

This damping scheme should, of course, be reviewed and, if accepted, we should plan on doing this on all 8 similar baffles at both sites. The only other issue I can think of is melting of the small exposed region from wildly errant beams. However, I think that only rapidly moving wide-angle beams from HAM2 could reach the Viton, and I think we have other Viton on the tables that is more likely to be a problem.

Finally, the central panel of MCA2 was loose where a bolt had apparently broken off during installation, and we added a small chunk of Viton to damp the vibration (see figures).

Robert, Corey, Hugh, Jim