First results on the performance of the HEGRA IACT array

Abstract First results concerning the performance characteristics of the HEGRA IACT array are given based on stereoscopic observations of the Crab Nebula with four telescopes. The system provides a γ-ray energy threshold around 0.5 TeV. The Crab signal demonstrates an angular resolution of about 0.1°. Shape cuts allow to suppress cosmic ray background by almost a factor 100, while maintaining 40% efficiency for γ-rays. The Crab signal is essentially background free. For longer observation times of order 100 h, the system in its present form provides sensitivity to point sources at a level of 3% of the Crab flux. Performance is expected to improve further with the inclusion of the fifth telescope and the implementation of advanced algorithms for shower reconstruction.