This chapter deals with the actual design of the pion beta calorimeter,
a design that ultimately determined the shapes and the number of detector
modules described in the previous chapter. The design proceeded with the
general guideline of uniform coverage of solid angle by the detector modules,
high energy resolution for the elimination of background events, high rate
capability, optimization of light collection efficiency for the modules and
maximum economy for different modular shapes. These features are obtained in
a spherical geometry arrived at by a geodesic breakdown of an icosahedron.