STEREO ARRAY of 30 m imaging atmospheric Čerenkov telescopes: A next-generation detector for ground-based high energy gamma-ray astronomy

Abstract

The construction of the H.E.S.S. ( High Energy Stereoscopic System), a superior system of four 12 m imaging atmospheric Čerenkov telescopes, has been completed recently in the Namib desert close to Windhoek, at 1800 m above sea level. This new generation of ground-based gamma-ray detectors has an energy threshold of about 100 GeV in observations at zenith and a sensitivity of about 1% Crab flux for a point-like γ-ray source. Such high sensitivity was achieved due to 0.1° angular resolution, as well as, severe cosmic ray background rejection acquired from multi-fold imaging of individual atmospheric showers. In addition H.E.S.S. has a rather good energy resolution of 15%. H.E.S.S. has been taking routine observations of the γ-ray sources since December 2003. Similar stereoscopic arrays are currently under construction at Kitt Peak, Arizona, and at Woomera, Australia. Two telescopes of somewhat larger size of 17 m diameter are being built by the MAGIC collaboration on the Canary Island of La Palma. The first of these two telescopes has been taking data since the Fall of 2003. The outstanding physics results achieved with H.E.S.S. already in a first year of its exploitation strongly encourage further development of imaging atmospheric Čerenkov technique for high-quality γ-ray observations, which is basically driven by father reduction of the energy threshold of a forthcoming major future γ-ray detector. Here we are dealing with such a detector, which may allow us to achieve an energy threshold as low as 10 GeV given a unique sensitivity of about 2 × 10 −13 erg cm −2 s −1. Basic results on performance and sensitivity for a single stand-alone 30 m imaging atmospheric Čerenkov telescope, as well as for a system of two and five Čerenkov telescopes, derived from appropriate Monte Carlo simulations, are discussed here.