Session MH: Instrumentation V

The next generation neutron detector for the studies of exotic nuclei

The development of radioactive ion beam facilities which can create very neutron rich nuclei necessitates detectors with improved neutron energy resolution and neutron selection. Exotic nuclei near the neutron drip line are far from beta decay stability and become more likely to undergo beta delayed neutron emission processes. The Neutron dEtector with Tracking (NEXT) will be a high resolution neutron detector designed as neutron-gamma discriminating-plastic scintillator coupled to silicon photomultipliers (SiPM's). The NEXT configuration will be based on ToF measurements with improved time resolution and interaction localization. Recent advancements in PSD plastic scintillators and SiPM's are the foundation of the compact design of the NEXT detector. Current development of the prototype includes optimizing SiPM timing capabilities and determining PSD characteristics of different plastic scintillators. Monte Carlo simulations have been developed to design a scintillator with optimal light collection and timing resolution. Results from ongoing project development will be presented in this contribution.   

Development of an array of liquid-scintillator-based bar detectors: SABRE

Advanced neutron detectors will play a key role in future measurements involving radioactive ion beams (RIBs), where experiments require high solid angle coverage, high efficiency, good position resolution and good neutron-gamma discrimination to overcome low reaction yields and high gamma backgrounds. To address this need, an array of prototype organic liquid-scintillator-based neutron detectors has been developed at Oak Ridge National Laboratory for use in nuclear reaction studies. The Scintillation Array of Bars for Reaction Experiments (SABRE) consists of five 12” long, 2” diameter cylindrical bar detectors filled with custom organic liquid scintillator with individual photomultiplier tube readouts at each end. Use of custom liquid reduces the cost without sacrificing the resolution of the energy (via time of flight) or position determination. In-house purification of the scintillator mixtures resulted in improved pulse shape discrimination and increased light output. Discussion of the liquid scintillator development and the design and commissioning of SABRE will be presented.   

Preparing for beta-delayed neutron emission studies in 78Ni region with VANDLE at RIBF

 The measurement of the beta decay strength distribution in the decay of doubly magic nucleus 78NI was proposed at RIBF RIKEN. The experiment will utilize VANDLE neutron detector combined with the high-efficiency gamma-ray array to measure a complete cascade of the decay to both neutron bound and unbound states in 78Cu.    The experiment will provide a critical test of the predictions of the decay strength, which are foundational for the lifetime calculation for the very neutron-rich nuclei in the region of the nuclear chart, where the r-process originates. The new configuration VANDLE detector setup was designed and is mounted at RIBF RIKEN and is ready to experiment. The details and improvements of the detection setups will be presented.   

Direct Neutron Scattering Observations in BC408 Scintillator, and Comparison to Simulation

Monte Carlo simulation is important for interpretation of experimental data from fast neutron-scintillator interactions (involving elastic and inelastic scattering from C and H nuclei), especially in experiments requiring multiple neutron detection, such as in studies of neutron-unbound nuclear states above the 2n threshold, owing to the difficulty of distinguishing single and multiple neutron interactions in the detector volume. To test our GEANT4 modeling we transported 16 detectors from MoNA (the Modular Neutron Array at NSCL/MSU), each consisting of a 200x10x10 cm$^3$ bar of organic plastic scintillator BC408 with a PMT fixed to each end, to Los Alamos National Lab.  The detectors were arranged in two different stacking geometries in the 90-m station on LANSCE/WNR flight path 4FP15L and exposed to a tightly-collimated beam of spallation neutrons ranging in energy from 0.5 to 800 MeV. GEANT4 Simulation predictions (using both the GEANT4 physics package as well as MENATE\_R) were compared with scattering observations for 20-200 MeV neutrons.  Simulation was most accurate for events involving the first neutron scatter, but differences (some significant) existed for modeling a neutron scattering multiple times.  Results will be presented.