PIXE and the nuclear microprobe: Tools for quantitative imaging of complex natural materials

The 40 year history of nuclear microscopy has seen sustained progress in the development of technology needed to improve PIXE analysis and trace element imaging performance. Focussing systems have been developed for improved spatial resolution, detector systems have evolved to collect more signal, full-spectral scanning data acquisition approaches have been devised. The complexity of PIXE spectra has driven the development of techniques for fitting numerous overlapping components in spectra for quantitative analysis, methods have been developed for specialized problems in geology, such as the analysis of fluid and melt inclusions in minerals, and techniques for the deconvolution of elemental components in full-spectral scanning data sets have been developed to produce accurate element images. The future of nuclear microscopy using PIXE is promising. Lens system approaches have evolved and point towards 'full bore' acceptance, optimal matching to accelerator emittance, high current density and sub-μm spatial resolution using many nA beam currents. Detector arrays and integrated data acquisition and scanning systems are emerging that can collect all events across a large solid-angle collection area and process these events for element image display in real-time. The combination of these advances provides a path to greatly enhanced sensitivity for PIXE analysis and imaging and a more productive user experience. The emergence of detector array approaches for scattered particles and reaction products, and the development of software tools for coupled PIXE-RBS data reduction, suggest a path towards complementary RBS and NRA tools. The stage is set for an exciting and productive future for PIXE imaging on the nuclear microprobe.