Developing a focused neutron probe for materials analysis

Long wavelength neutrons have optical properties analogous to those of photons, and may be focused to produce significantly higher fluxes using the principle of multiple mirror reflection from smooth surfaces at small grazing incident angles. Narrowly focused beams of cold neutrons (with wavelengths greater than 0.4 nm) allow greater spatial resolution for analytical applications than previously available, and will improve the detection limits of neutron absorption measurements (which are dependent on the neutron capture reaction rate) for quantitative analysis. Since the absorption cross section increases linearly with neutron wavelength, the reaction rate for a given isotope increases with the use of cold neutrons. This suggests microprobe capabilities which complement other radiation techniques for multidimensional microanalysis of trace elements in materials science. Among the techniques which will benefit by the development of focused neutrons are prompt gamma activation analysis and neutron depth profiling, by increasing the elemental sensitivity, lowering the detection limits, enhancing multi elemental as well as spatial analysis.</jats:p