Cosmic ray astrophysics, an active area at the cutting edge of basic research, investigates particles (or rays) that arrive at the earth's surface from the sun and beyond (even extra-galactic sources). Project GRAND is an extensive detector array which studies these rays in two energy bands depending on the trigger selected: the primary band (solar), from 30 to 300 GeV (GeV is giga, or billion, electron volts); and secondary band (extrasolar), from 100 to 100 000 TeV (TeV is teva, or trillion eV).
The original goal of this array is to study stellar point sources of gamma rays with sub-second precision. This study requires: good angular resolution, good particle identification, and sufficient running time to gather statistics. This project has pioneered the use of tracking detectors (proportional wire chambers, PWCs) in cosmic ray research; tracking detectors have the advantage of providing superior angular resolution and instantaneous particle identification. These PWC tracking detectors are ideal for studying our latest research goals: to look for the highest-energy particles generated by our Sun.