The Level 0 Pixel Trigger System for the ALICE Silicon Pixel Detector: implementation, testing and commissioning

The ALICE Silicon Pixel Detector transmits 1200 Fast-OR signals every 100 ns on 120 optical readout channels. They indicate the presence of at least one hit in the pixel matrix of each readout chip. The ALICE Level 0 Pixel Trigger System extracts them, processes them and delivers an input signal to the Central Trigger Processor for the first level trigger decision within a latency of 800 ns. This paper describes tests and measurements made on the system during the qualification and commissioning phases. These included Bit Error Rate tests on the Fast-OR data path, the measurement of the overall process latency and the recording of calibration data with cosmic rays. The first results of the operation of the Pixel Trigger System with the SPD detector in the ALICE experiment are also presented.