Search

The use of thermal neutrons in contact radiography and tomography [Schlenker and Baruchel, Physica B 137, 309 (1986)] provides a powerful nondestructive analysis technique for materials that are difficult to study with x rays [Kirz et al., Quart. Rev. Biophys. 28, 33 (1995)]. Since x rays are strongly absorbed by the heavier elements and neutrons are preferentially scattered by light elements, neutron radiography is well suited to the visualization of light elements in the interior of metallic objects. In this letter, we demonstrate neutron radiography using a number of different contrast mechanisms. We find we are able to obtain radiographs showing features hitherto unobservable.

The application of neutron interferometry to the measurement of the atom density of polymer thin films (

The water sorption of proton-exchange membranes (PEMs) was measured in situ using high-resolution neutron imaging in small-scale fuel cell test sections. A detailed characterization of the measurement uncertainties and corrections associated with the technique is presented. An image-processing procedure resolved a previously reported discrepancy between the measured and predicted membrane water content. With high-resolution neutron-imaging detectors, the water distributions across N1140 and N117 Nafion membranes are resolved in vapor-sorption experiments and during fuel cell and hydrogen-pump operation. The measured in situ water content of a restricted membrane at 80 °C is shown to agree with ex situ gravimetric measurements of free-swelling membranes over a water activity range of 0.5 to 1.0 including at liquid equilibration. Schroeder’s paradox was verified by in situ water-content measurements which go from a high value at supersaturated or liquid conditions to a lower one with fully saturated vapor. At open circuit and during fuel cell operation, the measured water content indicates that the membrane is operating between the vapor- and liquid-equilibrated states.

Here the authors introduce a Fourier based method for phase contrast neutron imaging, report its experimental implementation, and show results for a one-dimensional test phantom. This approach makes use of neutron interferometry to achieve both phase contrast and to spatially code the phase of the neutron with a linear phase grating. The spatial information is recovered from the coherent interference of this phase grating and a spatial phase distribution due to the sample. By moving neutron imaging from real to reciprocal space they avoid the need for position sensitive detectors and improve the potential image resolution.