Vallania, P (reprint author), Ist Nazl Fis Nucl, Sez Torino, Via P Giuria 1, I-10125 Turin, Italy.
The ARGO-YBJ experiment has been designed to study the extensive air showers with an energy threshold lower than that of the existing arrays by exploiting the high altitude location (4300 m a.s.l. in Tibet, PR China) and the full ground plane coverage. The lower energy limit of the detector (E similar to 1 GeV) is reached by the scaler mode technique, i.e. recording the counting rate at fixed time intervals. At these energies, transient signals due to local (e.g. Forbush decreases) and cosmological (e.g. Gamma ray bursts) phenomena are expected as a significant variation of the counting rate compared to the background. In this paper, the performance of the ARGO-YBJ detector operating in scaler mode is described and discussed. (C) 2008 Elsevier B.V. All rights reserved.