<title>Novel high-resolution PeV gamma-ray telescope</title>

Abstract

Most high energy Cosmic Rays are charged but a few are gamma rays generated by extremely energetic processes which are not understood. Precise directions for the gamma rays will indicate their sources. The most energetic gamma rays produce Extensive Air Showers (EAS) in the atmosphere. From the earliest days of radar there have been attempts to use radio techniques to measure the energy of Cosmic Ray air showers. None have used radio techniques to measure the direction of Cosmic Ray induced Extensive Air Showers. This paper examines the different mechanisms by which radio waves of a wide range of frequencies are reflected from both the relativistic shower front of the EAS and the temporary column of ionization left behind. It is shown that under certain conditions there is a relatively strong reflected signal. It is estimated that a few percent of the high energy (PeV 10<SUP>15</SUP> eV) cosmic ray flux reaching the earth are gamma rays. The current angular resolution of Cosmic Ray detectors is little better than one degree. This paper considers the possibility of scattering radio waves from the ionization produced by an EAS to provide, in conjunction with a ground based EAS gamma ray telescope, a new form of high energy gamma ray telescope. It will provide precise direction coordinates for the primary cosmic ray particle significantly better than the best current methods for single events. Precision direction coordinates should reveal gamma sources against the general background of charged cosmic ray events. A design is proposed for a novel high resolution, high energy gamma ray telescope.