Sensitive 3D hydrogen microscopy by proton proton scattering

Elastic proton proton scattering is a sensitive and fast method for hydrogen analysis. Utilising a nuclear microprobe it is actually the only technique for the absolute quantification of hydrogen distributions with micrometer or even better lateral resolution. High proton energies, e.g. 20 MeV, allow a wide field of applications since even materials, some 100 μm thick, can be analysed. Irradiation damage is reduced to a minimum compared to all other known ion beam analysis techniques, because a large solid angle of detection of some stradian can be used and the nuclear scattering cross section for protons at these energies is enhanced nearly three orders of magnitudes compared to Coulomb scattering. As a consequence, a sensitivity in the ppm range for hydrogen microscopy is possible. However, the large solid angle of detection induces geometrical effects in the energy analysis which are kept within a physical limit by an angular resolution of 10 mrad e.g. by utilising an annular silicon strip detector of 2.3 sr solid angle of detection. Therefore, the third dimension is provided with a depth resolution better 10 μm using the energy information of the scattered protons.