Calibration and in-flight performance of the Compton telescope prototype LXeGRIT

The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is the first balloon-borne instrument developed to validate the concept of a monolithic detector with 3D imaging capability as a Compton telescope for MeV astrophysics. The geometrical area is about 350 cm(2), an order of magnitude smaller than that of COMPTEL and the thickness of sensitive LXe is 7 cm, of equivalent stopping power as COMPTEL D2 detector. The spectroscopic and imaging response of LXeGRIT has been fully characterized in calibration experiments on the ground and during balloon flight experiments. During its most successful flight campaign of 27 h from Ft Sumner, in Fall 2000, the LXeTPC was operated without any external shield. The gamma-ray background, measured at float altitude in the 0.5-10 MeV energy band, is well explained by the known atmospheric gamma-ray flux. Results on the LXeGRIT in-flight performance, effective area, minimum flux sensitivity and background level are presented in this paper. (C) 2003 Elsevier B.V. All rights reserved.