A gamma-ray Laue lens focusing telescope aboard a balloon experiment

The future of the soft gamma–ray astronomy (>100 keV) is connected with the development of focusing instruments. Laue lenses are the best candidate instruments. We propose a balloon experiment in order to test for the first time a new concept of focusing gamma–ray telescope that makes use of Laue lenses made of mosaic crystals in transmission configuration, now developed in our institutes. We discuss here the features and requirements of this balloon experiment. In 10000 s of observing time per each source at 3 mbars we expect to reach the sufficient sensitivity to demonstrate the spectral and imaging capabilities of the lens we propose to test.