[Rich] The aerogel from ASPEN

[pappalardo at fe.infn.it]

Dear All,

In my last talk at the fridays RICH meetings, I showed some measurements
done in Ferrara on the aerogel tiles recently received by the US company
ASPEN.
The conclusion of my studies was that the optical properties
(transmittance, and scattering length) of the n=1.05 tiles were extremely
poor and well below the standards we need. The only tile with reasonable
performances was that with n=1.01 (not usable for our RICH).

Today I had a look at the ASPEN presentation (link below)

http://science.energy.gov/~/media/np/pdf/sbir%20sttr/SBIR%20STTR%202012%20Meeting/Day2/Begag_Aspen-Aerogels-Presentation.pdf

and found that our measurements are qualitatively consistent with what
they show.

The good transmittance shown in slide 8 refers to n=1.013. On the other
hand, on slide 9, they explicitly clame that the transmittance at 400nm is
"relatively low" for higher refractive indices. Also the picture shown
(top right of slide 9) is consistent with appearance (opaque) of the tiles
with n=1.05 received from them.

Best regards,
Luciano