Advanced neutron tomography

Abstract

A neutron tomography system has been developed as a nondestructive technique for quantitative assessment of impurity concentrations in metal castings. Neutrons maximize the sensitivity for certain isotope while tomography provides the threedimensional density information. A specific application is the detection ofhydrogen down to 200 ppm weight in aircraft engine compressor blades. A number ofpreprocessing corrections have been implemented for the projection images in order to achieve the detection requirements at a testing rate ofthree blades per hour. Among the procedures are corrections for neutron scattering and beam hardening. Post processing ofthe reconstructions consists of aligning test object images with standard object images. With these procedures the artifacts in tomographic reconstructions are shown to be less than the signal for 100 ppm hydrogen in titanium alloy samples.