Design and performance of a modularized NaI/Tl/ detector /The Crystal Ball prototype/

A prototype NaI(Tl) detector (the Cluster of 54) of spherical geometry subtending a solid angle of 7.5% of 4pi at its center, has recently been assembled and tested. This detector consists of 54 close-packed but optically isolated NaI(Tl) modules and the associated electronic circuitry. The Cluster of 54 is the predecessor of an almost complete spherical detector, the Crystal Ball, which will cover 94% of 4pi. The latter detector is now under construction and is especially designed for the study of gamma-rays produced in electron-positron collisions at colliding beam facilities. This article outlines the mechanical, optical, and electronic assembly of the prototype system.