Neutron Scintillators Using Wavelength Shifting Fibers

Abstract

A proposed design for an optically-based, one-dimension scintillation detector to replace the gas-filled position-sensitive proportional counter currently used for a wide-angle neutron detector (WAND) at the High-Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) is presented. The scintillator, consisting of a mixture of 6 LiF and ZnS(Ag) powders in an epoxy binder, is coupled to an array of wavelength shifting optical fibers which provide position resolution. The wide-angle neutron detector is designed to cover a 120 degree arc with a 75 cm radius of curvature. The final detector design provides for 600 optical fibers coupled to the scintillator screen with an angular resolution of 0.2 degrees. Each individual pixel of the detector will be capable of operating at count rates exceeding 1 MHz. Results are presented from the measurement of neutron conversion efficiencies for several screen compositions, gamma-ray sensitivity and spatial resolution of a 16 element one-dimensional array prototype.