Data acquisition system for intermediate energy nuclear experiments

The data acquisition system for the OBELIX experiment at the LEAR (Low Energy Antiproton Ring) antiproton beam is presented. The experimental setup is composed of five detectors with different readout systems. The data acquisition is designed to allow the five detectors to run together as well as in stand-alone mode, the introduction of some data reduction steps, global hardware control, and statistically significant event control. These goals are reached through a tree of VME crates controlled by a medium-range computer and four workstations; most of the data is transmitted on a combination of VME and VSB buses, while the system is completely controlled by the Ethernet bus. This design allows high modularity either in the hardware or in the software