J. Kissel

I've B&K hammered the response of a bunch of other stand-alone components in HAM2: New MC13 Table Baffle, PSL DownPeriscope, MCREFL Periscopes, and New ISI Table Baffles. The prognosis is not good. Every component aside from the PSL down-periscope has resonant features below, if-not-well-below 150 Hz -- the original requirement from the SEI team to keep ISI 30 Hz UGF control loop design possible. Granted, the MC REFL Periscopes haven't really changed, but this data shows that (a) they are different from each other, and (b) that Periscope 2 is confirmed rattly mess. I can only hope that we can some how stiffen & and damp, instead of just shoving viton everywhere. I fear it's far too late in the schedule...

This being said, I must give props to the SLiC design team for ramming through an incredibly quick design-to-installed turn-around, and I appreciate that not everything could have been thought. We know from LLO that all this new baffling is doing the right thing as far as scattering goes.

See the .pdf for transfer functions.

I'll note that *everything* I hammered in HAM2 (including PRM and PR3 from LHO aLOG 39212) shows these resonant features at ~10.6 and 12.4 Hz. However, the ISI table baffles (a.k.a. beard baffles) seem to show this feature more prominently, and their mounting looks ... less-than-stiff ... so my guess is that since the accelerometer is mounted to the table in these measurements, they're coupling to every measurement. BUT, this is just a guess. I have a tough time believing that there's enough moving mass in those baffles to resonate as low as 10-12 Hz.

Aside from this common feature, I list the remaining prominent low-frequency features here in tabular form for future reference:
    DOF                       IFO Y                                    IFO X
    MC1/3 Table Baffles       [21.5 29.38 44.62]                       [29.62 36.88]
    PSL Down Periscope        [238.4]                                  [269.8]
    ISI HAM2 Table Baffle     [12.38 40 60.75]
    MCREFL Periscope 1        [124.6 124.8 140.8       194.6]          [22.00       42.25 141.2 167.9 195.1 ]
    MCREFL Periscope 2        [31.75 124.6 142.6 167.8 201.4 285.0]    [22.38 31.25 48.12 143.5 167.6 201.6 223.6]

Pictures are attached to guide discussion and aide any repeat measurements in the future.