Fast pipelined trigger for the H1 experiment based on multiwire proportional chamber signals

Based on a total of 1920 pads from two cylindrical and one planar double layer multiwire proportional chamber, the vertex position of ep collisions along the beam axis of the HERA storage ring is reconstructed. This allows discrimination between ep events, originating from the nominal interaction region, and background, introduced mainly by proton beam pipe and proton rest gas interactions. The trigger works in a pipelined manner, delivering a delayed decision every 96 ns, corresponding to the accelerator bunch crossing frequency. It employs custom designed gate arrays as well as XILINX logic cell arrays and a 16 Mbyte static RAM lookup table. Computer controlled debugging procedures take advantage of the reprogrammability of XILINX chips.