ARGO-YBJ data acquisition system

The ARGO-YBJ experiment is reaching its final design configuration. An array of single layer Resistive Plate Counters (RPCs) covering an area of ∼5800m2 will collect a huge amount of data. The throughput required from the final detector strongly depends on the trigger rate. The DAQ system must be able to sustain a data transfer rate estimated to be the order of 15 MB/s and a high peak of data flow. Data are read out using a typical front-end acquisition chain built around a custom bus. Specialized electronics have been designed and efficient software had to be written to perform this task. Data are then sent to the on-line farm through a switch exploiting gigabit-ethernet protocol. In this paper we will describe the design of the DAQ system, the software which deals with data collection and network sending and the performances. The architecture of the on-line farm is also described together with the monitoring system.