The CLEO-III trigger: Analog and digital calorimetry

The calorimetry subsystem of the CLEO-III Trigger incorporates both analog and digital electronics to provide pipelined trigger information every 42 ns with a latency of approximately 2.5 μs. This paper describes the pipelined signal-processing and pattern-recognition schemes used to provide calorimeter information to the experiment trigger, with somewhat greater emphasis on the analog components of the system. Analog processing is employed to address the quantization error caused by split energy deposition in adjacent calorimeter cells, and digital field programmable gate arrays are used extensively to filter and categorize the calorimeter energy topology. Timing, geographical, and energy information are all available for use in the calorimeter trigger.