T. Ahmed et al., A PIPELINED FIRST-LEVEL TRIGGER FOR THE H1 FORWARD-MUON SPECTROMETER, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 364(3), 1995, pp. 456-472
We have built a fast, pipelined first-level trigger processor for the
H1 experiment at HERA. The trigger finds tracks in the forward-muon sp
ectrometer which point back to the interaction vertex. The inputs to t
he trigger come from drift chambers with a 6 cm drift space correspond
ing to a maximum drift time of 1.2 mu s. These chambers consist of two
layers of drift cells whose staggered configuration makes it possible
to extract the time at which a particle traversed the chambers to bet
ter than one HERA bunch-crossing period, 96 ns. The trigger hardware e
xploits this characteristic in a real-time operation, and is able to f
ind pointing tracks and associate them to production in a specific ele
ctron-proton crossing. The trigger processor must be deadtime free. It
operates in a pipelined mode with 48 ns steps and has a latency of ab
out 22 HERA bunch-crossing periods. The compact design is based on two
semi-custom integrated circuits. Both are field-programmable 32 X 32
coincidence matrices, one having serial loading of its inputs and the
other using parallel loading. The system was installed in the H1 exper
iment early in 1993 and has run successfully since then.