LED calibration system for a quartz fiber calorimeter

We discuss the performance of a light calibration system for multi-PMT arrays. Seven blue high-light-yield LEDs are focused on to a bundle of optical quartz fibers to provide a signal to each PMT in the array. The calibration system was developed for an electro-magnetic quartz-fiber calorimeter with 25 PMT readout and can deliver a light pulse signal equivalent to /spl sim/10/sup 4/ photoelectrons via a single fiber within /spl sim/50 ns time. Mechanical design, pulse shape and duration, light yield, and uniformity are discussed.