An Advanced Triggerless Data Acquisition System for GRAPES-3 Muon Detector

The large area 560\,m$^2$ directional muon telescope at Gamma Ray Astronomy at PeV Energies phase -3 (GRAPES-3) experiment in Ooty, India was designed primarily to study the extensive air showers (EAS) and made operational in year 1998. It has turned out to be an unique instrument to make fascinating study of exotic phenomenon by introduction of a new parallel data acquisition system (DAQ) in year 2000 to measure the muon directional flux. The recent discoveries of transient weakening of Earth’s magnetic shield probed by a Cosmic Ray Burst and measurement of the electrical properties of a thundercloud through muon imaging has demonstrated the capabilities of this instrument. The design of new triggerless muon data acquisition system (TM-DAQ) using Field-programmable gate array (FPGA) would enhance the present capabilities and open a new window on several physics fronts such as, a) precise measurement of the muon flux for thunderstorm studies, b) study of large angle EAS using the muon component, c) search for exotic particles characterized by early or delayed arrivals. We present here the key salient features of the TM-DAQ along with initial observations.