The Oxford scanning proton microprobe
The Scanning proton microprobe uses a focused beam of MeV protons to give analytical information by exploiting two physical processes, particle induced X-ray emission (PIXE) and Rutherford Backscattering (RBS). Scanning transmission ion microscopy may also be included in the nuclear microscopy package to give imaging data. PIXE is particularly appropriate for biomedical research as signals from hydrogen, carbon, nitrogen and oxygen, which are the main components of a biological matrix, are not detected and therefore signals from inorganic elements with z > 10 will not be swamped by signals from the matrix. Elements with z < 10 can, however, be detected using RBS when present at higher concentrations.
Apart from the biomedical field, the SPM has wide-ranging applications spanning diverse areas such as archaeology, materials science and environmental chemistry. This paper reviews the theory of ion beam analysis, the Oxford Scanning Proton Microprobe and outlines some of the work currently being carried out at Oxford.