DENSITY AND COMPOSITION ANALYSIS USING FOCUSED MEV ION MICROBEAM TECHNIQUES

Nuclear microscopy uses focused MeV ion microbeams to non-destructively characterize materials and components with micron scale spatial resolution. Although a number of accelerator-based microbeam methods are available for materials analysis, this paper centers on the techniques of Ion Microtomography (IMT) and Particle-Induced X-ray Emission (PIXE). IMT provides quantitative three-dimensional density information with micron-scale spatial resolution and 1% density variation sensitivity. Recently, IMT has become more versatile because greater emphasis has been placed on understanding the effects of reconstruction artifacts, beam spatial broadening, and limited projection data sets. PIXE provides quantitative elemental information with detection sensitivities to 1 mu g/g or below in some instances. By scanning the beam, two-dimensional maps of elemental concentration can also be recorded. However, since X-rays are produced along the entire path of the ion beam as it penetrates the sample, these measurements only give depth-averaged information in general. PIXE tomography (PIXET) is the natural extension from conventional PIXE analysis to the full three-dimensional measurement and forms the bridge linking the complementary techniques of PIXE and IMT. This paper presents recent developments and applications of these ion beam techniques in a diverse range of fields including characterizing metal-matrix composites, biological specimens and inertial confinement fusion targets.