GALI - a GAmma-ray burst Localizing Instrument: results from full-size engineering model

We present a full-size engineering model of GALI - The GAmma-ray burst Localizing Instrument, composed of 362 CsI(Tl) small cubic scintillators, distributed within a small volume of ∼ 2l, and read out by silicon photomultipliers. GALI can provide directional information about GRBs with high angular accuracy from angledependent mutual obstruction between its scintillators. Here, we demonstrate GALI’s laboratory experiments with an ²⁴¹Am source, which achieved directional reconstruction of <3° accuracy, in agreement with our Monte- Carlo simulations. GALI has a wide field view of the unobstructed sky. With its current cubic configuration, GALI’s effective area varies between 97 cm² (face on) and 138 cm² (from the corners at 45°), which is verified in the current experiment.