MRI: Development of a High Resolution Neutron Detector for Decay and Reaction Studies with Exotic Nuclei

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

The scientific focus of this award is to explain the formation of elements in the Universe by studying nuclear states that are produced through specific processes and emit neutrons. That study will be done with a new multi-detector array, n5D, which will be developed with this award. This new detector will allow scientists to answer questions related to the rapid neutron capture process, which is responsible for nearly half the elements heavier than iron, and to study the properties of very neutron rich isotopes. Measuring neutron energies precisely and efficiently is one of the most difficult tasks in nuclear spectroscopy. With the high accuracy and detection efficiency of the new detector array, scientists will be able to study beta-delayed neutron emission on exotic nuclei, where knowledge of the beta strength distribution is necessary to predict nuclear lifetimes for nuclei far from stability. This MRI project will train future scientists who will conduct the bulk of the testing and operation of the array. The project will leverage recent developments in electronics and detector materials to provide a neutron detector for use not only in fundamental science but also in national security, medical, and industrial applications, and space exploration. This project will develop a new neutron detector array with unique tracking capabilities. This n5D detector array will serve decay and reaction experiments, which require neutron detection in the 100 keV to 10 MeV range of energies. In n5D, neutrons will be detected using the time-of-flight (TOF) technique. The novelty of the project is the high neutron energy resolution, which will be achieved by through tracking the interactions of the neutron as it travels through the detector material. Unlike in the case of gamma ray detection, the TOF technique does not require registration of the full energy deposited in the detector; tagging/tracking the interaction points is sufficient. The tracking will thus overcome the main limitation of a typical TOF neutron detector, where the detector thickness required to maximize efficiency degrades the neutron energy resolution. Bright neutron-gamma-discriminating plastic scintillators will be used. They will enable experiments with otherwise limiting levels of gamma-ray background and will improve the signal to noise ratio. Scintillation readouts will be achieved using compact segmented photomultipliers facilitating the high detector granularity required for tracking, a key advancement in this field. Digital electronics will be implemented for signal processing providing the timing and neutron-gamma discrimination as well as the flexibility needed to implement new scintillators or light readout sensors in the future. An array of about 40-50 modules will be constructed for decay and reactions experiments. The University of Tennessee, Knoxville/Tennessee Tech University team will build upon its expertise in neutron detector development and digital signal processing. Key elements of the project are optimization of single-detector module performance and an efficient production cost, such that the array is easily scalable to work with large systems at major research centers throughout the world. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.