High energy physics data acquisition and trigger systems

The trigger and data acquisition tasks faced by the next generation of High Energy Physics experiments are very challenging. One example is the Zeus Detector Trigger and Data Acquisition system. The Zeus detector is being built for operation at the HERA storage ring that will provide collisions between 820 GeV protons and 30 GeV electrons next year. The first level trigger is pipelined with a decision provided 5 μ sec after each beam crossing, occurring every 96 nsec. The first level trigger rate needs to be held to 1 kHz against a rate of proton-beam gas interactions of approximately 500 kHz. A second example is a proposed trigger and data acquisition system for the Solenoidal Detector Collaboration experiment at the SSC laboratory. The SSC will provide collisions between beams of 20 TeV protons at the end of this decade. The first level trigger will be pipelined with a decision provided 1.5 μ sec after each beam crossing, occurring every 16 nsec. The first level trigger rate needs to be reduced to between 10 and 100 KHz from an initial rate of 100 MHz. Both the Zeus and SDC systems have three levels of data acquisition and triggering. In this paper issues of architecture, data storage and analysis for these system are discussed