Track recognition in 4 μs by a systolic trigger processor using a parallel Hough transform

A parallel Hough transform processor has been developed that identifies circular particle tracks in a 2-D projection of the OPAL jet chamber. The system consists of a Hough transform processor that determines well-defined tracks, and a Euler processor that counts their number by applying the Euler relation to the threshold result of the Hough transform. A prototype of a systolic process has been built that handles one sector of the jet chamber. It consists of 35×32 processing elements that are loaded into 21 programmable gate arrays (XILINX). This processor runs at a clock rate of 40 MHz. It is tested offline with about 1000 original OPAL events. No deviations from the offline simulation are found. A trigger efficiency of 93% is obtained. The prototype, together with the associated drift time measurement unit, has been installed at the OPAL detector at the LEP (Large Electron Positron Collider) and 100 k events have been sampled to evaluate the system under detector conditions