DEVELOPMENT OF AN IN-AIR ON/OFF AXIS STIM SYSTEM FOR QUANTITATIVE ELEMENTAL MAPPING

Abstract

We have developed an in-air on/off axis STIM for simultaneous density mapping with PIXE and RBS, which will be useful for damage-monitoring in cell analysis and for yield correction based on the thickness distribution of X-ray self-absorption in samples. The in-air on/off axis STIM system provides a mass concentration map in the cell analysis. In the system, a thin scattering foil is placed downstream of the sample and scattered protons are detected by a Si -PIN photodiode set at 30 degrees with respect to the beam axis. These components are set in a He -gas-filled chamber to reduce energy loss, scattering and sample damage. Using this system, areal density mapping is carried out for RBL-2H3 cells simultaneously with PIXE and RBS. Correction for self-absorption is performed and areal density map of elements is converted into a mass-concentration map using the measured matrix density. The areal density distribution of P corresponds to that of matrix and mass concentration of P is uniform in the cell region. On the other hand, Br is concentrated in the nucleus, even in the mass concentration map. The Br accumulation in the nucleus is first confirmed in mass concentration using the on/off axis STIM and PIXE system. The in-air on/off STIM system will be effective for monitoring changes in cell density during beam irradiation.