9322583 Cronin This award is to operate the Chicago Air Shower Array (CASA) at Dugway Utah for three years. The array was constructed with NSF funding over a period of three years to verify the existence of isolated high energy gamma sources which had been reported in the literature. This is the largest array of this kind in the world and it operates in conjunction with a muon array built by the University of Michigan (MIA) on the same site. The combination of the two make a powerful tool to distinguish between incident gamma rays and incident charged particles. They have operated for about one year and their results as well as the results from other experiments have shown that the alleged sources no longer exist. If the sources are episodic, CASA hopes to find them over the course of the next three years. In addition they will be able to make significant contributions to our knowledge of the cosmic ray composition and to the energy spectrum. They also have a program to extend their energy reach by coordinating their observations with those of the Fly's Eye, another detector at Dugway operated by the University of Utah that looks at even higher energies by detecting atmospheric fluorescence, and which overlaps CASA in coverage and in energy. ***
