The status of PIXE in geochemistry

PIXE is only one of several in-situ microanalytical techniques available to geochemists, but it occupies a unique niche in terms of a combination of accuracy and sensitivity. PIXE is 1-2 orders of magnitude more sensitive than electron probe analysis and has comparable accuracy at present. In the future, the simpler PIXE X-ray production physics could allow an order of magnitude greater accuracy for major element analysis. Secondary ion mass spectrometry has greater sensitivity, but, although progress has recently been made, SIMS has no general scheme for correcting for matrix effects on ion yields. In contrast, the conversion of observed x-ray counts to concentrations for PIXE is based on well understood physics. Synchrotron X-ray fluorescence has comparable accuracy and perhaps slightly better sensitivity than PIXE, but has much worse depth resolution. The excellent signal to noise inherent in PIXE could be fully realized with the use of efficient crystal spectrometers instead o the Si(Li) detectors utilized in essentially all studies to date.