(Corey, Eric, Hugo, Jim)

Investigations continue for the big mechanical resonance peak around 120Hz.  Hugo has given us a rough location of where to look (Somewhere around the H3 GS-13).  On Monday, we pulled out H3 (replaced with mass), but there was no change.  Also on Mon we pulled some walls in hopes of finding anything obvious.  One issue noticed were a pair of 90degree Wall Brackets which were loose (at V3); see attached "photo(3)".  These were torqued down, but the 120Hz peak was still there---Hugo did notice broadband noise reduction in the high frequencies by torquing these brackets down.

On Tuesday, Jim started banging on things to see if he could hear any rattling/ringing.  He noticed a ping when hitting the big Leg Element weight on the Optics Table.  We decided to put some Viton pads underneath it.  Hugo went with a checkerboard pattern ([48] 0.5"x0.5" 0.0625" thick pads); see attached photos....grrrr, the last photo should be flipped, looks fine on my computer before I uploaded.  Waiting to hear how the measurements turned out on these guys.