New detector concept with neutron interaction localization capabilities J. Heideman a , D. P´ erez-Loureiro a , R. Grzywacz a,c,* , J. Chen a , L. H. Heilbronn b , S. K. Neupane a , K. Schmitt a,1 , C. R. Thornsberry a , M. M. Rajabali d , A. R. Engelhardt d , C. W. Howell d , L. D. Mostella d , J. S. Owens d , S. C. Shadrick d , E. E. Peters f , A. P. D. Ramirez f , S. W. Yates f , S. Munoz e a Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee , 37996 USA b Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee , 37996 USA c Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA d Department of Physics Tennessee Technological University, Cookeville, Tennessee, 38505, USA e Joint Institute for Nuclear Physics and Applications, Oak Ridge TN 37831 USA f Department of Physics and Astronomy and Chemistry, University of Kentucky, Lexington, Kentucky, 40506 USA Abstract A new high precision time of flight neutron detector concept for beta-delayed neutron emission and direct reaction studies is proposed. The Neutron dEtector with Xn Tracking (NEXT) array aims to maintain high instrinsic neutron detection efficiency while reducing uncertainties in neutron energy measurements. A single NEXT module will be composed of thin segments of neutron-discriminating plastic scintillator, each optically separated, coupled to a position sensitive photo-detector. By incorporating a position sensitive photo-detector with a large optically separated scintillator, NEXT will achieve high precision determination of neutron time of arrival and interaction position within the active volume. A design study has been conducted based on simulations and experimental tests leading to construction of prototype units. First results from neutron measurements will be discussed. Keywords: β-delayed neutron emission, direct reactions, time of flight 1. Introduction New generation radioactive ion beam facilities enable access to very neutron rich nuclei, approach- ing, and even reaching the neutron drip-line in cer- tain cases [1]. Far from stability, neutron separa- tion energies decrease as beta-decay endpoint ener- gies become large, increasing the likelihood of beta- delayed neutron emission. Neutron spectroscopy becomes essential to obtain important information about the nuclear structure for these very neutron- rich nuclei [2, 3, 4]. Neutron dEtector with Xn Tracking (NEXT) has been devoloped to observe beta-delayed neutron emitters with improved pre- cision. These improvements will also be applicable to proton transfer reactions which probe discrete states of exotic nuclei. NEXT has been designed * Corresponding author Email addresses: jheidema@vols.utk.edu (J. Heideman), rgrzywac@utk.edu (R. Grzywacz) 1 Present address: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA around neutron-gamma discriminating scintillator in order to improve background rejection. Preve- lant gamma-ray background common in decay and reaction experimental setups can be reduced signif- icantly in neutron spectra, further improving neu- tron energy measurements [5]. Proof of principle tests for the NEXT design study will be shown in this paper along with results from first neutron measurements. 2. Detector Design When the neutron kinetic energies are measured via time-of-flight (ToF), the energy resolution is given by the following expression [6]: ΔE E =   2Δt t  2 +  2ΔL L  2 , (1) in which t is the time-of-flight of the particle (Δt is uncertainty in time-of-flight) and L is the corre- sponding flight path-length (ΔL is the uncertainty Preprint submitted to Elsevier October 31, 2019 arXiv:1904.01662v1 [physics.ins-det] 31 Mar 2019