Track recognition in 4 ms 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 high-speed requirements imposed by the eight bunch crossing model of the LEP (Large Electron Positron Collider) could be fulfilled by computing the starting angle and the radius of curvature for each well-defined track in less than 4 μs. 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 systolic processor consisting of 35×32 processing elements has been realized with 21 XILINX chips that handles one sector of the jet chamber. It has been functionally tested with 981 original OPAL test events, and no deviations from the off-line simulation have been found. A trigger efficiency of 93% has been obtained. The prototype is running at a clock rate of 40 MHz