[Halld-cal] Light guide shapes
elton at jlab.org
Fri Apr 29 15:18:34 EDT 2011
Dear Bcal Readout,
Good ideas never die, even at this late stage. We are re-evaluating the
precise shapes of the light guides for the Bcal. Jim Fochtman, who has
been laying out the geometry for the readout has resurrected the notion
of phi-symmetric light guides. Similar schemes have been proposed
previous. See for example GlueX-doc-1536, Figs 7 and 8. Up to know the
nominal design has been that given in Fig 8, where there are 20
different light guide types and many of them have rectangular bases,
instead of trapezoids. The original concept for the phi-symmetric guides
had 40 different shapes and we were searching for ways of minimizing the
number and complexity of the shapes.
The new twist proposed by Jim is to have four columns, each identical,
just rotated with respect to the neighbor. In other words, for this
geometry, there are only 10 different light guide types. See attached
figure. This creates a gaps relative to the bcal physical build at the
center of the inner layer and at the outside corners of the outer layer.
We will likely want to stretch the height to over-cover part of the
aluminum plates in some areas in order to completely cover the entire
I wanted to put this out now so people could think about it before our
Bcal readout meeting next Tue. Comments and feedback are welcome.
p.s. Note that prototyping for the readout will continue with the
present nominal light guide design, even if we might decide to move to
the new geometry for the entire detector.
Jefferson Lab MS 12H5
12000 Jefferson Ave
Newport News, VA 23606
(757) 269-6331 fax
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