Phase-contrast x-ray imaging for nondestructive evaluation of materials

Phase-contrast x-ray imaging has been studied intensively in the past, mainly with applications to low density biological materials. In this work experimental and theoretical aspects of phase-contrast microfocus x-ray imaging of structural materials (metals and polymers) are considered. The diffraction field in an object from a point x-ray source is simulated and the effects of geometrical and material parameters on the x-ray phase-contrast image are obtained. It is shown that higher-order terms should be retained in the asymptotic expansion of the Green function in the image plane to accurately image discontinuities in structural materials. Experimental phase-contrast images of small defects are obtained with a 5 mu m microfocal x-ray source and compared with those from computer simulation as a function of geometrical magnification and photon energy. The phase-contrast x-ray imaging provides enhanced image contrast and improved edge definition and is important for further development of nondestructive evaluation of structural materials. (c) 2006 American Institute of Physics.