This research addresses the excitement generated in the field of cosmic ray physics by reports of point sources of Ultra High Energy (UHE) gamma rays detected by conventional sea level Extensive Air Shower (EAS) arrays. The investigator plans the completion of construction (already 25% complete) of an array using a new concept involving position sensitive detectors which, it is claimed, provides superior angular resolution of one quarter of a degree by directly measuring individual angles of the charged secondaries in the air showers. This array (GRAND) would consist of 64 stations (with 10 complete in December 1990) over a 100 meter by 100 meter area. Each station consists of eight planes, with area 1.25 square meters, of position sensitive detectors spaced vertically. The bottom two planes are separated from the top six by a thin steel absorber used to distinguish muons from electrons or soft secondary photons. Crucial features of the planned array then are smaller angular resolution (reducing background by a factor of nine relative to other comparable arrays) and muon, electron and soft photon identification.
