Novel neutron detector for high rate imaging applications

Next generation neutron science facilities, such as the Spallation Neutron Source, require improved thermal neutron detectors, with high counting rate capability, high spatial resolution, low cost per unit area, and adaptability to unique geometries. We propose a neutron detector technology, based on arrays of boron-lined plastic straws, that satisfies the above requirements. The elemental component of this detector is a B₄C-lined mylar straw, 4 mm in diameter and 1 m long, and operated as a proportional counter with an Ar/ethane gas mixture. Thermal neutrons captured in ¹⁰B are converted into secondary particles, which ionize the gas contained within the straw. Using a deep stack of such straws, with 20-25 layers, neutron detection efficiencies up to 80% can be achieved in the 1-10 Å neutron wavelength range. In such a highly segmented array, exceedingly high count rates can be achieved, on the order of 200×10⁶ cps/m². Gamma ray discrimination was on the order of 10⁶ for an energy threshold of 50 keV; position resolution of a 1-m long detector was measured to be 5.5 mm FWHM, and a highly linear readout was achieved using resistive charge division.