J. Kissel, T. Sadecki

Attached are the results of the H1 SUS ITMX fiber characterization perform last week while the QUAD was (in-air) still fully suspended. After initially gathering data on the +X / +Y, Front Right (as viewed looking at the HR surface, a.k.a. the Angus Convention) without using a speaker array (see LHO aLOG 38743), we resumed the next day using the array, but with it not attached to the structure in any way, just resting on the chamber floor near the Left or Right side as needed. 

To complete Borja's table from LHO aLOG 38309,

Angus      Global      Prev.            Avg.           This 
Conv.      Coord.      In-Air          In-Vac         Result

FL         -X/+Y      502.2+/-0.25     502.68     499.656+/-0.015

FR         +X/+Y      500.8+/-0.25     501.15     500.797+/-0.015

BL         -X/-Y      501.2+/-0.25     501.35     500.922+/-0.015

BR         +X/-Y      499.9+/-0.25     500.13     502.219+/-0.015

Naturally, the confusing directions in which these change from in-air in in-vac makes me wonder whether the naming convention didn't get mix up somewhere along the way...

However, with these measurements, we've taken up to the 6th harmonic in air. There are a select few of these results which are highly questionable, if not down-right untrustworthy. They're marked with an asterisk. However, all results are determined by just finding the maxmimum frequency bin in the spectra. Having starred at all the data by eye, this works, but because the Q of the mode is so large in air, I inflate the uncertainty to include two bin-widths, assuming that the mode is perfectly bin-centered (which isn't true). In other words -- take this data with grains of salt and a few flecks of black pepper.

Here're those results in tabular form:
         FL(-X/+Y)    FR(+X/+Y)    BL(-X/-Y)    BR(+X/-Y)
Fund.    499.656      500.797      500.922      502.219
2nd      991.859      993.5781     996          995.2969
3rd      1455.5       1461.906     1461.891     1471.969*
4th      1923.953     1924.766     1923.594     1931.125
5th      2384.375     2396.813     2382.125     2460.813*
6th      2837.75      2845.063     2846.625     2830.813

Excitingly, at least in broad strokes, 3 of the 4 fibers show very similar in-harmonicity (and that which doesn't has the black pepper data points).

I'm not sure how, but it would be very interesting to compare these higher harmonic results against the in-vacuum higher harmonics. Do we have individual fiber identification for non-fundamental harmonics? It's not reported in the LHO Violin Mode Table, for instance.