[DIRC] meeting Wednesday

[hyde at jlab.org]

Dear Carston,
The cross section of your lens designs, 15 mm x 35 mm matches
the DIRC bar cross section.
However, the expansion volume is of course larger than the bar,
and includes a 'step down' of ~10mm.

I have been discussing with Heghine the possibility of
using a lens with a square cross section:  35 x 35 mm.
I am hopeful that this would allow us to better transmit and image
the large angle photons (particularly from tracks near 90deg).

We realized today a problem, however.
With your most recent design, it is impossible to expand the
profile to square:  the thickness parameter of the second lens, currently
1 mm (thickness at edge) becomes negative (the radius of curvature
of the second interface is too small).

I wonder as you explore different lens parameters, if it would be able
to explore designs compatible with a square lens.

Sincerely,
Charles