A HIGH-EFFICIENCY, LOW-BACKGROUND NEUTRON AND GAMMA-DETECTOR FOR COLD-FUSION EXPERIMENTS

The present apparatus (named by the acrostic ''FERMI'' also to celebra te the 60 yr of the discovery, by Enrico Fermi and collaborators at Ro me University, of the effects of moderation of neutrons) is mainly a m oderated neutron detector developed for the search of cold fusion even ts. It is based on 7 BF3 and 2(3)He proportional counters with detecti on efficiency for neutrons 40%-8% in the range 1 keV-20 MeV, pulse sha pe acquisition and good time resolution for neutron bursts; it also al lows us to perform a good reconstruction of the average original neutr on energy. The neutron background measured in the Gran Sasso INFN unde rground laboratory is about 0.09 Hz. Gamma rays are revealed mostly by a complementary low background NaI detector with 26% solid angle cove rage. The performances are controlled by a full MC simulation, experim entally tested. A high multiplicity (up to similar to 100) neutrons' e vent has been detected during background runs. The system is being upg raded by the detection and identification of charged hadrons.