Operation and performance of RPCs in the ARGO-YBJ experiment

The ARGO-YBJ array for EAS detection at high altitude (4300m a.s.l.) is the largest RPC-based detector in operation at present (active area of 6700m2 out of a total instrumented surface of about 104m2). 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 g-ray point sources are also presented

Search for gamma ray bursts with the ARGO-YBJ detector in scaler mode

The ARGO-YBJ experiment has been designed to decrease the energy threshold of typical Extensive Air Shower arrays by exploiting the high altitude and the full coverage, consisting of a 6700m2 carpet of Resistive Plate Chambers located at Yangbajing (Tibet, PR China, 4300m a.s.l.). The lower energy limit of the detector (1 GeV) is reached with the ‘‘Scaler Mode’’, recording the counting rate at fixed time intervals. Here we present results concerning the search for emission from Gamma Ray Bursts (GRBs) in coincidence with satellite detections

Gamma Ray Astronomy with the ARGO-YBJ

ARGO-YBJ is the first EAS detector combining a very high mountain altitude (4300 m a.s.l.) to a "full coverage" detection surface. These features allow ARGO-YBJ to work with an energy threshold as low as a few hundreds GeV. The high duty cycle and the large field of view (~2 sr) make ARGO-YBJ suitable to monitor the gamma ray sky searching for unknown sources and unexpected events, like Active Galactic Nuclei flaring episodes or high energy Gamma Ray Bursts. In this paper we present the first observations of ARGO-YBJ concerning gamma ray astronomy, in particular the detection of the Crab Nebula and the blazar Markarian 421 during the 2006 and 2008 outbursts, and the results of a search for Gamma Ray Bursts emission in the GeV energy range using the scaler mode technique

The Yangbajing Super Complex Array Plan Based on the ARGO Carpet

Following the completion of the 5700m2 RPC carpet-like AS array at YangBaJing this year, a further plan based on the ARGO Carpet is raised. It characterizes with its high altitude site, its full-coverage detector array and the multi-parameter measurements. Apart from studies on TeV and sub-TeV energy range, UHE Gamma-ray sources and the Knee Physics will become its characteristic subjects. In the first phase of the plan, the Yangbajing Super Complex Array (YSCA) will include a 104m2 RPC Carpet, five indoor μ-detectors (∼170 m2each), four big outdoor μ-detectors (∼432 m2 each) and a traditional field scintillation detector array surrounding the Carpet. Monte-Carlo study shows that, with such an array in YBJ (4300m a.s.l.), γ-ray induced air showers can be separated from proton induced air showers clearly using only the observed electron and μ data event by event. To assist the classification of UHE air showers induced by different primary nuclei groups without severe interference by Composition/Model Entanglement, a second phase plan having a Central Burst Detector Array (CBDA) and some pulse shape detectors is schemed