GALI - A GAmma-ray burst Localizing Instrument: Results from Full Size Engineering Model

gamma-ray bursts - GRBs - are the most luminous transient events in high-energy astrophysics with durations of 0.1 ~100 seconds. Their non-thermal energy spectrum is in the soft gamma regime between several keV to several MeV. Long GRBs (duration > 2 s) are thought to be associated with stellar core-collapse supernovae, and short GRBs (duration < 2 s) are associated with compact stellar mergers of two neutron stars or a neutron star with a black hole. The detection of GRBs has always been intertwined with the challenge of identifying the direction of the source. Accurate angular localization of better than a degree has been achieved to date only with heavy instruments on large satellites. SWIFT-BAT uses a coded aperture mask to localize GRBs within a few arc minutes with a limited field of view. Conversely, Fermi-GBM uses scintillators dispersed around the satellite covering the entire sky, but with moderate localization accuracy .In this talk, we will introduce GALI - A GAmma-ray burst Localizing Instrument built according to a novel configuration of scintillators, which enables accurate localization of GRBs. Its working principle is based on angle-dependent mutual obstruction between the many small scintillators, which are distributed within a small volume. We will demonstrate GALI's laboratory experiments with a 241Am source, which achieved directional reconstruction of accuracy, in agreement with our Monte-Carlo simulations.