J. Kissel, J. Warner, H. Radkins, R. Schofield

Summary
The H1ISIHAM2's tuned mass dampers have been re-installed after I've retuned them to the lower frequency (from ~153 Hz to ~139 Hz). 

Attached are several results:
    - The frequency of each TMD, Before vs. After Tuning, as captured by the Laser Vibrometer / HeNe + QPD setup with an SR785
    - The frequency of Corner 2 & 3's TMDs compared against the response of those blades (without TMDs installed)
    - pictures of Corner 2 & 3's TMDs after they've been re-installed (taken by Jim).

Recall, because Corner 1's access is limited at best (see LHO aLOG 38739), we
    - don't have blade response measurements for Corner 1, nor
    - pictures of the TMD reinstalled
but we're confident it's tuned appropriately, placed well, and will do the job nicely given the predictability of the blade fundamental frequency shift with breadth of the TMD response.

Tuning Measurement Setup
Yesterday, I had hoped to tune the TMDs with the same simple Vibrometer + SR785 I'd used to success fully tune the Bounce/Roll Mode dampers and just magnetically afix the TMDs to the clean space on the optical table. However (as suspected by Robert and Hugh), the force between the magnets and the table was weak enough that I was getting inconsistent results -- the frequency would change depending on where I'd reflect the vibrometer off the surface of the TMD and/or where I placed the TMD on the table.
By the time I'd discovered this, I'd already started changing the frequency (loosening bolts holding the diving board/flexure/blade secure) on two blades, so that's why "before" frequencies in the TMDTuning_Results.pdf look so scattered (and not at 153 Hz).

So, today, I pulled out the HeNe + QPD kit I'd used to tune ISI HAM6's TMDs (from LHO aLOG 26488), which most importantly included an iron plate: a better surface to which the TMDs can magnetically adhere. Still suspicious it was a problem with the vibrometer, I set up the HeNe + QPD shadow sensor, and read out the response simultaneously with the SR785. With the better mounting plate, they agree swimmingly. Again, see 2017-09-21_H1ISIHAM2_TMDTuning_Results.pdf for results. As before, for excitation, I'm just flicking the mass end of the TMD with the same Class B, 3/32" Allen Key need to loosen / tighten the securing bolts, timing flicks reasonably well within the two averages of a 4 [sec] FFT length (i.e. Start > Flick > 1st Average Shows Up > Flick > 2nd average).

Note, the in results, I've rescaled the (uncalibrated) QPD ASDs to match (also uncalibrated) Vibrometer ASDs to help guide the eye. The absolute displacement of this measurement is of no consequence.

This makes me a little worried about how much force is obtained when the TMDs are attached to the 304 Maraging Steel blades, but the proof is in the pudding -- post-install proof that the TMDs do their job (e.g. LLO aLOG 25522).