A high efficiency, low background neutron and gamma detector for cold fusion experiments

The present apparatus (named by the acrostic “FERMI” also to celebrate the 60 yr of the discovery, by Enrico Fermi and collaborators at Rome University, of the effects of moderation of neutrons) is mainly a moderated neutron detector developed for the search of cold fusion events. It is based on 7 BF3 and 2 3He proportional counters with detection efficiency for neutrons 40%–8% in the range 1 keV-20 MeV, pulse shape acquisition and good time resolution for neutron bursts; it also allows us to perform a good reconstruction of the average original neutron energy. The neutron background measured in the Gran Sasso INFN underground laboratory is about 0.09 Hz. Gamma rays are revealed mostly by a complementary low background NaI detector with 26% solid angle coverage. The performances are controlled by a full MC simulation, experimentally tested. A high multiplicity (up to ∼ 100) neutronsʹ event has been detected during background runs. The system is being upgraded by the detection and identification of charged hadrons.