External micro-ion-beam analysis (X-MIBA)

In-air or external ion-beam analysis combined with 10-100 μm spatial resolution, is a truly unique feature of the nuclear microprobe technique. PIXE has been performed externally for many years, but, recently, other IBA techniques such as backscattering and nuclear reaction depth profiling measurements have been made in air. Presently, the use of external micro-ion-beam analysis or X-MIBA, is being attempted at a growing number of microprobe facilities; however, the full potential of this new technique remains relatively unexploited. This paper will review the X-MIBA technique with emphasis on (1) optimization of exit foil geometries, (2) beam focusing and spot size considerations, (3) external IBA techniques, and (4) radiation hazards associated with the direct and scattered beam, nuclear reaction products and radionuclei production in the air. The unique in-air analysis advantages of no pump down, and essentially unrestricted sample size or state (solid, liquid etc.), has resulted in a myriad of applications of this technique at Sandia, which are featured as examples. (orig.)