STIM imaging for mammalian cell samples before micro-PIXE analyses in air environment at JAERI Takasaki light ion microbeam system

In TIARA facility of JAERI, a scanning transmission ion microscopy (STIM) technique was introduced to the light ion microbeam system, so as to make direct beam positioning to samples for micro-PIXE analyses in the atmosphere. STIM is a low current (less than fA level) and high efficient sample imaging technique, which does not induce radiation damage even to biological cells for beam positioning before micro-PIXE analysis. The sample (bovine aortic endothelial cells) was prepared using a freeze-dry method on a thin polymer film which act not only as a sample backing foil but also as a beam extraction window to the atmosphere. A Si PIN photodiode (cover glass removed) was set just behind the sample in the atmosphere to measure the energy of proton microbeams passing through the sample and the window. STIM images were obtained in a short time, and corresponded with elemental maps obtained by subsequent micro-PIXE analyses. This paper will describe details of the experimental system and show preliminary results of STIM imaging and micro-PIXE analyses. (author)