Development and evaluation of an ion induced X-ray emission system for the analysis of light and medium weight elements
The present work describes the development of a proton induced X-ray emission (PIXE) analysis system, especially designed and built for routine quantitative multi-elemental analysis of a large number of samples. The historical and general developments of the analytical technique and the physical processes involved are discussed. The philosophy, design, constructional details and evaluation of a versatile vacuum chamber, an automatic multi-sample changer, an on-demand beam pulsing system and ion beam current monitoring facility are described. The system calibration using thin standard foils of Si, P, S,Cl, K, Ca, Ti, V, Fe, Cu, Ga, Ge, Rb, Y and Mo was undertaken at proton beam energies of 1 to 3 MeV in steps of 0.5 MeV energy and compared with theoretical calculations. An independent calibration check using bovine liver Standard Reference Material was performed. The minimum detectable limits have been experimentally determined at detector positions of 90° and 135° with respect to the incident beam for the above range of proton energies as a function of atomic number Z. The system has detection limits of typically 10- 7 to 10- 9 g for elements 14 < Z < 42 for lOµe of charge. Computer programmes have been written for data analysis and calculations of areal density of thin foils using Rutherford backscattering data. Amniotic fluid samples supplied by South Sefton Health Authority were successfully analysed for their low base line elemental concentrations. In conclusion the findings of this work are discussed with suggestions for further work.