Development of a microbeam PIXE system for additive light elements in structural materials

A new submicron scanning nuclear microprobe beam line was constructed in early 2016 at the accelerator facility of the University of Tsukuba, Japan. A microbeam scanning endstage (OM-2000, Oxford Microbeams, Oxford, UK) was installed at the end of this system. The distance from the object slit to the target position is 8730 mm and the working distance is 180 mm. This ion microbeam system will be used mainly for X-ray imaging of two-dimensional distributions of light elements in structural materials using particle-induced X-ray emission (PIXE). A silicon drift detector (SDD) with a thin window of Si₃N₄ was installed to detect characteristic X-rays emitted from light elements such as B, C, and N, which are common additive elements in structural materials. In addition, a superconducting tunnel junction (STJ) array detector is going to be installed to perform PIXE measurements more efficiently. By combining a microbeam scanning technology with the X-ray detectors, we plan to obtain two-dimensional maps of additive light elements in structural materials. Experiments for obtaining proton microbeams are ongoing, and a 6 MeV proton beam with a diameter of between 12 and 20 μm has been obtained to date.