Development of a micro-PIXE system using tapered glass capillary optics

The performance of a compact micro-PIXE system using a tapered glass capillary for beam focusing was examined with the help of Monte-Carlo simulations. The effective beam spot size was evaluated by an edge-scanning method and a two-dimensional element mapping was successfully demonstrated by using a copper fine-mesh target. The spatially resolved energy-spectrum measurement revealed that even protons scattered at the inner wall of the capillary have kinetic energies enough to induce the X-ray emission in the target. Monte-Carlo simulations showed that the beam-focusing factors of the capillaries used in this study are about 1.7. The uniformity of the beam does not depend so much on the distance from the capillary outlet, but the beam radius was found to be twice larger than its original size even at 1 mm from the capillary outlet, which was consistent with the effective beam spot size measurement.