Development of a new high-resolution neutron detector to study exotic nuclei.

An efficient neutron detection system with good energy resolution is required to correctly characterize decays of neutron-rich nuclei where beta-delayed neutron emission is a dominant decay mode. Precision neutron spectroscopy instrumentation is essential to probe nuclear structure effects in neutron-rich nuclei in new-generation radioactive beam facilities. A new high-resolution detector system, Neutron dEtector with Xn Tracking(NEXT), was constructed, characterized, and tested in decay and reaction experiments. Its essential capability is the interaction position localization, which improves energy resolution without compromising detection efficiency in the neutron time-of-flight measurement. Neutron-gamma discrimination capability of NEXT allows for performing experiments even in high background conditions. The first measurements were performed with beta-delayed neutron emitters using a small array of NEXT at Argonne National Laboratory(ANL) and National Superconducting Cyclotron Laboratory(NSCL). The detector concept, design, and results from the first measurements will be presented.