Characterisation of the University of Surrey Ion Beam Centre in-air scanning microbeam

摘要

The University of Surrey Ion Beam Centre has recently commissioned a new in-air scanning microbeam. The new external beam uses a magnetic quadrupole doublet to focus a beam-spot of μm dimensions on the vacuum exit window so that there are no beam defining apertures close to the analysis region. A pre-lens magnetic dipole allows beam scanning for measuring two dimensional elemental distributions. The scanned area is limited by the diameter of the exit window to 3 mm diameter at present. The sample is positioned using a front viewing video microscope and an alignment laser, and detectors for X-rays (high energy and low energy), backscattered particles and gamma rays are installed. This paper will detail the ion optical characteristics of the in-air scanning microbeam, and the methods used in the characterisation. A comparison between calculated optical properties of the in-air scanning microbeam, using the ray-tracing software TRAX, and the measured properties of the beam will be presented.