First measurements with the ARGO-YBJ detector

The detection of small size air showers at high altitude allows the search for γ-ray point sources at few hundreds GeV energy threshold. The ARGO-YBJ experiment, currently under construction at the Yangbajing Cosmic Ray Laboratory (4300 m a.s.l.), has been designed to meet these requirements by exploiting the RPC technology and a dedicated DAQ system based on a custom high-speed read-out architecture. About 1600 m2 of detector have been instrumented and put into operation for calibration runs devoted to test the performance of the individual components and their integrated operation. Events collected with a ’shower mode’ trigger have been recorded to check the consistency of physics data. We present the current status of the experiment and report on future prospects

The Trigger System of the ARGO-YBJ detector

The ARGO-YBJ experiment has been designed to detect air shower events over a large size scale and with an energy threshold of a few hundreds GeV. The building blocks of the ARGO-YBJ detector are single-gap Resistive Plate Counters (RPCs). The trigger logic selects the events on the basis of their hit multiplicity. Inclusive triggers as well as dedicated triggers for specific physics channels or calibration purposes have been developed. This paper describes the architecture and the main features of the trigger system