Characterization and applications of a capillary microbeam for Ion Beam Analysis

Contact:
M. Schulte-Borchers

M. Schulte-Borchers (PhD thesis), M.J. Simon, M. Doebeli


Microprobes enable the extension of Ion Beam Analysis with an additional spatial information, which allows for measurements of specific small areas of a sample or imaging of a larger area. Also fabrication and modification of microstructures can be conducted using microbeams. Typical systems involve expensive electrostatic or magnetic lenses to focus ion beams down to micro- or even nanometer scale.

Glass capillaries on the other hand have been used to demonstrate small beam diameters for MeV ion beams and thereby present an easy and low-cost way to obtain ion beams of micron or submicron scale. They are easy to adjust in only few minutes and their small beam exit even enables in-air measurements without additional pumping or an exit window. The achieved focus is independent of ion type and energy, which can thereby be changed during the measurement without further modifications. Also targeting on the sample is improved by the usage of capillaries: The outlet of the capillary can be seen with the naked eye, which enables very precisely positioned irradiations or measurements.

A capillary microprobe has been developed at our accelerator facility to be used for Ion Beam Analysis. Its feasibility for in-air measurements have already been demonstrated, e.g. in PIXE measurements on an antique figure as well as STIM measurements on a mosquito's wing.

Subject of recent experiments are investigations of the phase space of capillary focussed ions using a 2D detector and nuclear track detectors. These will give an insight into the underlying mechanisms which lead to the focussing effect, if there really is one. Also the not insignificant effect of residual air inside the capillary on in-air analysis is currently surveyed for the first time. Other features of the capillary ion beam, e.g. its expected to be quite high targeting accuracy, still have to be explored further. For the future, also an experiment to evaluate the applicability of a capillary to focus ions for MeV SIMS is planned. 

External PIXE on bronce statue