The microprogrammable processor ESOP in the AFS trigger system

A programmable processor is used online in the trigger system of the Axial Field Spectrometer for selecting events with a charged particle of high transverse momentum. After having formed a pretrigger by using signals from proportional chambers, a selected part of the data from the cylindrical drift chamber is transferred into the memory of the processor. The track sagitta of the triggering particle is calculated. Only if it is smaller than a predefined value of the event is accepted and recorded on magnetic tape. The implementation of the processor in the electronics of the experiment and the software procedures are discussed together with the performance of the system. (5 refs).