The detection of very high energy cosmic gamma rays using the atmospheric Cerenkov technique

Abstract

This thesis is concerned with the detection of very high energy cosmic gamma rays using the atmospheric Cerenkov technique. A general introduction to gamma ray detection techniques is followed by a detailed discussion of the principles of the atmospheric Cerenkov technique and the history of its use prior to this work. The design and operation of the University of Durham facility in Dugway, Utah is described in depth. Monte Carlo computer simulations have been developed to assist in both the understanding of the equipment and the analysis of the results for the Durham facility. The variation of the response of the array with zenith angle and detector threshold has been investigated and the aperture function of a single telescope calculated. The latter has been found to be a complicated function of both zenith angle and detector threshold. Computer simulations have also been developed to aid in the design of a camera to record two-dimensional Cerenkov light images from small extensive air showers, and to provide a means of testing analysis routines; these are discussed. The camera is located at the F.L. Whipple Observatory in Arizona. The techniques employed in the analysis of data recorded by the Dugway facility are discussed, and a computer package developed to aid in the routine aspects of the analysis is described. Results of observations from two sources, Cygnus X-3 and PSR0531, are presented, with particular reference to periodicities inherent in the sources and to bursts of gamma ray emission. The discussion of the results includes a review of the various models which have been proposed for Cygnus X-3.