This neutron transmission imaging technique combines the hardware used for conventional neutron radiography with the Bragg edge transmission features of time-of-flight methods. The main component of the energy-selective radiography set-up was a gated image-intensified CCD camera that viewed a neutron-sensitive scintillation screen via a mirror. Energy resolution was obtained via synchronization of the lightintensifier with the pulse structure of the neutron source. A main advantage of the imaging method at a pulsed source is that energy-selection can be achieved for a large field of view and with high wavelength resolution in terms of the band width. Contrast variation and enhancement of materials that are indistinguishable by conventional neutron or X-ray radiography can be straightforwardly achieved taking advantage of the excellent crystallographic-phase sensitivity of the method, by collecting images below and above characteristic Bragg edges of the phases. Microstructural features such as crystallographic texture can be directly visualized with high spatial resolution, in principle even for distinct texture components.
G Frei, P Vontobel, EH Lehmann (Paul Scherrer Institut, Switzerland), JR Santisteban (CNEA, Argentina), W Kockelmann (ISIS)
Research date: December 2007
W Kockelmann et al., Nucl. Instr. Meth. A 578 (2007) 421