LENDA: A low energy neutron detector array for studies of (p,n) reactions with radioactive beams

Charge-exchange reactions at intermediate energies have been used extensively in nuclear structure studies as a sensitive probe of the spin-isospin response of nuclei. Experimental investigations have been mostly limited to stable targets. There are, however, compelling scientific arguments to extend these studies to unstable nuclei. The Low Energy Neutron Detection Array (LENDA) is designed to facilitate the study of (p,n) charge exchange reactions in inverse kinematics using unstable beams. The array, which is designed to measure neutron energies and angles with high detection efficiencies, is currently under development at the National Superconducting Cyclotron Laboratory (NSCL). The final array will consist of 24 plastic scintillator bars each with dimensions of 300× 45 × 25 mm. The neutron energy will be determined by the time-of-flight technique, while the position of interaction will be deduced using the timing and energy information from photomultipliers attached to both ends of each bar. A prototype of the final array has been constructed and characterized in a simple test setup. Results of test measurements and simulations have demonstrated a neutron energy threshold of <13 keV and overall time (position) resolution of ≤ 1 ns ( ∼4 cm).