A large area muon tracking detector for ultra-high energy cosmic ray astrophysics—the GRAPES-3 experiment

Abstract

Certain aspects of ultra-high energy (UHE) cosmic ray astrophysics require correlated studies on the electron and muon components of air showers, namely, the search for cosmic ray sources through γ -ray astronomy and studies on the variation of the nuclear composition of primary cosmic rays with energy. While studies on the electron component provide basic information about the arrival direction and energy, it is the muon component that plays a crucial role in distinguishing primary γ -rays from charged cosmic ray particles and in determining the composition. A large area (560 m 2 ), tracking muon detector of the GRAPES-3 experiment, operating at Ooty in southern India, has been designed for detailed studies on both of these aspects of UHE cosmic ray astrophysics. We present here the details of the muon detector, associated electronics and the data acquisition system. A brief discussion of the potential of the muon detector is presented through simulation studies.