Operation and performance of RPCs in the ARGO-YBJ experiment

The ARGO-YBJ array for EAS detection at high altitude (4300 m a.s.l.) is the largest RPC-based detector in operation at present (active area of 6700 m 2 out of a total instrumented surface of about 10 4 m 2 ). The constant monitoring of the main operational and environmental parameters is essential for both keeping the detector status under control and understanding the detector behaviour more deeply. Exploiting the information provided by the ARGO-YBJ Detector Control System, the present status of the detector is described and some correlations between the environmental and the operational parameters of the ARGO-YBJ RPCs are shown. This study was performed using the monitored data from the complete ARGO-YBJ array which has been in operation since October 2007. Preliminary results on the observations of the Moon shadow and of γ -ray point sources are also presented.