33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE

Abstract: The LAGO project is an international effort of many groups in different countries to operate a network of water Cherenkov detectors (WCDs) in high-altitude sites in Latin America. Although data taking started in 2007, up to date no GRB has been observed, but we have set limits on 40 GRBs, the most stringent one being for GRB080904 in the 0.5 GeV- 100 GeV energy range. Currently we are undertaking an upgrade of the detection system at the Sierra Negra site (4550 m.a.s.l.) in Mexico. Four new WCDs of 40 m2 have been installed, and are fully instrumented. The new detectors are cylindrical and segmented in four parts, with 7.3 m of diameter and 1.15 m height. The body and the bottom of the detectors are covered with a high diffusive and reflective banner bag. This bag is filled with purified water of high quality up to a height of 1.1 m Four 8 ” PMTs are distributed at 2.4 m from the center, with a regular separation, one for each segment. New electronics has been developed for the new LAGO detectors. The new system consists of an ADC daughter board running at 100 MSPS.We present the performance test of the new detectors with this new data acquisition system