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 $\sim 2$l, and read out by silicon photo-multipliers. GALI can provide directional information about GRBs with high angular accuracy from angle-dependent mutual obstruction between its scintillators. Here, we demonstrate GALI’s laboratory experiments with an ${}^{241}$Am source, which achieved directional reconstruction of $<$3${}^{\circ }$ 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 cm${}^2$ (face on) and 138 cm${}^2$ (from the corners at 45${}^{\circ }$), which is verified in the current experiment.