Position sensitive scintillation neutron detectors using a crossed-fiber optic readout array

The Spallation Neutron Source (SNS) under construction at the Oak Ridge National Laboratory will be the most important new neutron scattering facility in the United Sates. Neutron scattering instruments for the SNS will require large area detectors with fast response (< 1 microsecond), high efficiency over a wide range of neutron energies (0.1 to 10 eV), and low gamma ray sensitivity. We are currently developing area neutron detectors based on a combination of ⁶LiF/ZnS scintillator screens coupled to a wavelength-shifting fiber optic readout array. A 25 × 25-cm prototype detector is currently under development. Initial tests at the High Flux Isotope Reactive have demonstrated good imaging properties coupled with very low gamma ray sensitivity. In addition, we have developed a multi-layer scintillator/fiber detector to replace existing He-3 gas detector tubes for higher speed operation. This detector has demonstrated a neutron detection efficiency of over 75% at a neutron energy of 0.056 eV or about twice thermal. The response time of this detector is approximately 1 microsecond. Details of the design and test results of both detectors will be presented.