[Halld-pid] light guide simulation

[Beni Zihlmann]

Hi All,
I have simulated a light guide using GEANT4 and looked at how much light 
we lose.
You can find the results at the following link.
http://www.jlab.org/Hall-D/software/wiki/index.php/Light_Guide_Design

Because it is very hard to model a bend in the tapered section where by 
"tapered"
I mean the part that converts a rectangular shape into a round shape I 
left this
part strait. I introduced a bend afterwards in the round section. That 
is much easier
to model. It turns out that most light gets lost in the tapered section 
anyway even
without a bend. Secondly as expected a larger bend causes more light to 
be lost.
In general we can expect a light loss of about 25% to 30% through the 
full light guide
including interfaces also to the PMT.

any thoughts and ideas are welcome,

Beni