Development of a 3D-Imaging Calorimeter in Lanthanum Bromide for Gamma-Ray Space Astronomy

International audienceGamma-ray astronomy, in the energy range from 0.1 up to 100 MeV, holds many understudied questions connected with stellar nucleosynthesis, the Sun, neutron stars and black holes. To access the physics behind, a significant increase in instrumental sensitivity, compared to previous missions, e.g. NASA/CGRO and ESA/INTEGRAL, is needed. One of the promising concepts is an Advanced Compton telescope. It has good discovery potential and is able to avoid problems like high background in the MeV energy band. Under the project of creating a prototype of such instrument, we study cerium-doped lantanum(III) bromide (LaBr3:Ce) inorganic scintillator. Its internal qualities, especially good energy resolution and radiation tolerance, make it a smart choice for the calorimeter part of a future spaceborne telescope. At CSNSM Orsay, we have created a new detection module from 5x5 cm2 area and 1 cm thick LaBr3:Ce crystal scintillator coupled to 64 channel multi-anode photomultiplier and read out by the ASIC MAROC, used previously for the luminometer of the ATLAS detector (CERN). Characterization, thorough measurements with various radioactive sources, as well as, single photoelectron detection have been done. Furthermore, we made a comparison with the detailed GEANT4 based simulation including tracking of the optical photons. Finally, we have studied the 3D reconstruction of the first interaction point of incident gamma-ray, utilizing a neural network algorithm. This spatial position resolution plays a crucial part in the future implementations and together with the other measured properties makes our detector module very interesting for the next generation of space telescopes operating in the MeV range