Data acquisition system for the Belle experiment

We built a data acquisition system for the Belle experiment at the KEK B-factory. The system is designed to record the signals from the detectors at 500 Hz trigger rate with a less than 10% dead time fraction. A typical event size is 30 kbyte, which corresponds to a data transfer rate of 15 Mbyte/s. Main components are two kinds of detector readout systems, an event builder, an online computer farm and a data storage system. The system has been reliably in operation at the design performance for a half year. We have completed cosmic-ray data taking for 2.5 months and have started physics data taking on Jun. 1, 1999.