Detection of Atmospheric Cherenkov Radiation Using Solar Heliostat Mirrors

The gamma-ray energy region between 20 and 250 GeV is largely unexplored. Ground-based atmospheric Cherenkov detectors offer a possible way to explore this region, but large Cherenkov photon collection areas are needed to achieve low energy thresholds. This paper discusses the development of a Cherenkov detector using the heliostat mirrors of a solar power plant as the primary collector. As part of this development, we built a prototype detector consisting of four heliostat mirrors and used it to record atmospheric Cherenkov radiation produced in extensive air showers created by cosmic ray particles.Comment: 16 latex pages, 8 postscript figures, uses psfig.sty, to be published in Astroparticle Physic

The TIGRE Instrument for 0.3–100 MeV Gamma-Ray Astronomy

The Tracking and Imaging Gamma-Ray Experiment4 (TIGRE) uses multilayers of silicon strip detectors both as a gamma-ray converter and to track Compton recoil electrons and positron-electron pairs. The direction and energy of the Compton scattered gamma ray and pair particles are measured with arrays of small CsI(Tl)-photodiode detectors. With a large ?-steradian field-of-view, the prototype instrument described here is sensitive to gamma rays from 0.3 to 100 MeV with a typical energy resolution of 3% (FWHM) and a 1-? angular resolution of 120 arc min. at 2 MeV. It has a high absolute detection efficiency of 8% over the full energy range. The telescope will be described and Monte Carlo calculations will be presented. Measurements with a small desktop instrument are presented elsewhere in this volume. © 1995 IEEE.National Aeronautics and Space Administration: NAGW-1996 Sharif University of Technology1 visiting from Cukurova University, Adana, Turkey 2 also at Riverside Community College, Riverside, CA 92506 3 visiting from Sharif University of Technology, Tehran, Iran 4supported by NASA Grant NAGW-199

Atmospheric gamma rays at geomagnetic latitudes of -29° and +43°

We present results of atmospheric gamma ray measurements obtained during two balloon flights from Alice Springs, Australia (? = -29°), and Fort Sumner, New Mexico, United States of America (? = 43°) at geomagnetic cutoff rigidities of 8.5 GV and 4.3 GV, respectively. The fluxes, in the energy range of 1-15 MeV, are derived as functions of zenith angle, residual depth, and latitudinal rigidity. We find while the downward moving gamma ray flux at the float level (4.8 g cm-2) is not a strong function of rigidity the upward flux at ? = -29° is, on average, by factors of 2 to 4 lower than at ? = 43°. The energy spectra of the downward moving gamma rays at various altitudes are harder than the upward moving gamma rays. The spectral indices for both upward and downward fluxes at ? = -29° are lower than at ? = 43°. Copyright 1997 by the American Geophysical Union