A NEW METHOD FOR ONLINE TRUE-ELEMENTAL IMAGING USING PIXE AND THE PROTON MICROPROBE

A rapid matrix transform method called Dynamic Analysis (DA) has been developed for the production of true elemental images using PIXE and t he Proton Microprobe that are free of image artefacts due to continuum background and overlap with X-ray lines and detector response feature s (e.g. tails and escape peaks) from other elements. The method has be en installed at the CSIRO and the NAC for the on-line projection of tr ue elemental images. These on-line images are also quantitative, and o nly require minor off-line correction(similar to 10% typically) to obt ain accurate true elemental images at major and trace element levels. Correction issues discussed include the variation of PIXE yields with sample composition across a scan area, and dead-line corrections. The method is now in routine use and enables on-line quantitative true ele mental imaging at the CSIRO and the NAC using a simple procedure invol ving the fitting of a preliminary scan spectrum to build the DA transf orm matrix; spectrum fitting and matrix construction are part of the G eoPIXE software package. The method has been extensively tested using samples which display complex multi-element overlaps, the DA method su ccessfully projecting accurate images for elements obscured by the lin es of interfering elements.