Scanning Microscopy


Most published PIXE (proton-induced X-ray emission) work concerns thin targets. Recently progress in improving both the fundamental data base and in developing a range of standardization techniques has propelled thick target analysis to the forefront of activity in the PIXE field. Limits of detection are a complex issue depending not only on the continuous background but also on the characteristic X-rays of the matrix; in favorable cases a few ppm may be reached in convenient analysis times. The unfolding of multi-element PIXE spectra is akin to the same problem in EPMA (electron probe microanalysis), and EPMA methodologies, especially as regards background removal, have a role to play: accurate analytic lineshapes for Si(Li) detectors are a crucial ingredient of accurate extraction of peak areas. Analyses of a binary compound and of the NBS aluminum alloy SRM 1258 illustrate the current capabilities of TTPIXE (thick-target PIXE). Recent computer simulation work extends TTPIXE's capability from the customary smooth specimens to targets with curved or randomly rough surfaces.

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