Hydrogen microscopy and analysis of DNA repair using focused high energy ion beams

Abstract

The ion microprobe SNAKE (Supraleitendes Nanoskop für Angewandte Kernphysikalische Experimente) at the Munich 14MV tandem accelerator achieves beam focussing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, i.e. 4–28MeV protons or up to 250MeV gold ions. Due to these ion beams, SNAKE is particularly attractive for ion beam analyses in various fields. Here we describe two main applications of SNAKE. One is the unique possibility to perform three-dimensional hydrogen microscopy by elastic proton–proton scattering utilizing high energy proton beams. The high proton energies allow the analysis of samples with a thickness in the 100μm range with micrometer resolution and a sensitivity better than 1ppm. In a second application, SNAKE is used to analyse protein dynamics in cells by irradiating live cells with single focussed ions. Fluorescence from immunostained protein 53BP1 is used as biological track detector after irradiation of HeLa cells. It is used to examine the irradiated region in comparison with the targeted region. Observed patterns of fluorescence foci agree reasonably well with irradiation patterns, indicating an overall targeting accuracy of about 2μm while the beam spot size is less than 0.5μm in diameter. This performance shows successful adaptation of SNAKE for biological experiments where cells are targeted on a sub-cellular level by energetic ions.