Intelligent trigger processor for the crystal box

Abstract

A large solid angle modular NaI(Tl) detector with 432 phototubes and 88 trigger scintillators is being used to search simultaneously for three lepton flavor changing decays of muon. A beam of up to 10/sup 6/ muons stopping per second with a 6% duty factor would yield up to 1000 triggers per second from random triple coincidences. A reduction of the trigger rate to 10 Hz is required from a hardwired primary trigger processor described in this paper. Further reduction to < 1 Hz is achieved by a microprocessor based secondary trigger processor. The primary trigger hardware imposes voter coincidence logic, stringent timing requirements, and a non-adjacency requirement in the trigger scintillators defined by hardwired circuits. Sophisticated geometric requirements are imposed by a PROM-based matrix logic, and energy and vector-momentum cuts are imposed by a hardwired processor using LSI flash ADC's and digital arithmetic loci. The secondary trigger employs four satellite microprocessors to do a sparse data scan, multiplex the data acquisition channels and apply additional event filtering.