ANALYSIS OF UNSECTIONED SPECIMENS - 2D AND TOMOGRAPHIC PIXE WITH STIM

Two techniques for quantitative analysis of heterogeneous thick specim ens are reviewed. First, a measurement of the total zinc content in th e abdomen of a fly is reported. The calculation used to determine the uncertainty in this measurement is detailed. STIM measurements at two different angles were used to determine the possible range of the X-ra y production cross section and the X-ray attenuation factors. The abdo men content of zinc was determined to be 0.022(+0.009, -0.006) mug. Se cond, a PIXE-STIM microtomographic determination of metal concentratio ns in the sting of a scorpion is reviewed. STIM tomography was used to determine the X-ray production cross sections and the X-ray attenuati on factors for points inside of the specimen. Details of how this info rmation was then used for reconstructions of PIXE tomographic data are given. Finally, 2D PIXE measurements on a thick section of this sting are reported. On this section the measured concentration of zinc reac hed 22(+/- 3)% of dry mass, in satisfactory agreement with the results from tomography, 25(+/- 3)%.