Development of a method for the quantitative analysis of hydrogen in minerals with a high-energy proton microbeam

This report describes our recent development that mainly aims at the quantitative determination of hydrogen concentration in melt inclusions confined in minerals. The method is based on the proton-proton elastic scattering at 20 MeV. Since the stopping power of protons at 20 MeV is very small in materials as silicates, protons pass through a 200 μm thick sample without appreciable energy loss. It is feasible, therefore, to carry out non-destructive hydrogen analysis of melt inclusions with sizes in the range from a few tens to approximately 200 micrometers. Besides the depth profile of hydrogen, a map of the three-dimensional hydrogen concentration is observable using a scanning microbeam. An example is presented on a melt inclusion in quartz from pyroclastic rocks collected at Enda, Zaoh-machi, Miyagi Prefecture, Japan.