LONG DISTANCE TEST OF THE CLAIRE GAMMA-RAY LENS

摘要

The objective of CLAIRE is to prove the principle of a Laue diffraction lens for nuclear astrophysics. CLAIRE's lens consists of 556 Ge-Si crystals, focusing 170 keV γ-ray photons onto a 3x3 matrix of Ge detectors placed at its focus. In June 2001, the instrument was flown on a stratospheric balloon by the French Space Agency CNES. CLAIRE's first light consisted of some thirty diffracted photons from the Crab nebula, corresponding to a 3 σ detection. This result called for further tests to confirm the performance of the instrument. In May 2003, CLAIRE was tested on a 205 m long optical bench that was set up at an aerodrome near Figueres, on the Spanish Mediterranean coast. In this paper we describe the test and report measurements of the lens efficiency, the relation between diffracted energy and distance, the quality of the lens tuning, the evaluation of de-pointing effects and the verification of the optical axis.