Homogeneity study of an Fe impurity in unalloyed Zn using PIXE

We have studied the distribution of an Fe impurity in unalloyed Zn material along line scans in spots of 1 mm diameter each using PIXE. En order to ac hieve the necessary precision (1%) in the determination of this low Fe cont ent (about 100 mg/kg), a sufficient counting rate of Fe X-rays is needed wi thout overloading the counting electronics with Zn X-rays at the same time. Therefore, the development of our PIXE analysis system had to take into ac count: (a) optimising the thickness of a Ni absorber foil in order to selec tively reduce the counting rate of Zn without adding an unproportionally hi gh Ni counting rate, (b) implementing a triggered ion beam deflection syste m capable of handling very high counting rates (up to 8 kcps), (c) developi ng the spectrum evaluation code to take account of the selective absorption by the Ni foil. The results of our PIXE measurements showed an inhomogenei ty in Fe of up to 10%, considered too high to accept this zinc material as a new reference material. (C) 1999 Elsevier Science B.V. All rights reserve d.