Neutron depth profiling of elemental concentration using a focused beam

Neutron Depth Profiling (NDP) is a nondestructive analytical technique for measuring the concentration of certain light elements as a function of depth near the surface of a solid matrix. The concentration profile is determined by analyzing the energy spectrum of the charged particles emitted as a result of neutron capture by the elements. The measurement sensitivity is directly proportional to the neutron beam current density. A more intense neutron beam achieved by focusing improves sensitivity for specimens of small area. In addition, a narrowly focused beam adds lateral spatial resolution to the technique, which is advantageous compared with that obtained by collimating the beam size using apertures. Capillary neutron lenses have been shown to focus a neutron beam to sub-millimeter spot size. Preliminary tests have been performed in the NDP geometry using such a focusing device. A lateral resolution in the sub-millimeter range is demonstrated by a specimen of non-uniform lateral distribution composed of a row of borosilicate glass fibers.