A high-and-flat efficiency moderated neutron detection array of 3 He counters has been recently developed for photoneutron cross section measurements at the future ELI-NP gamma-ray beam source. We have designed a three rings geometry 31 with ˜37% flat within 5% in 10 keV to 5 MeV energy interval. commissioning experiment was performed using proton beams delivered by 9 MV Tandem accelerator IFIN...