Progress and application of the Tohoku microbeam system

A microbeam system was constructed at the Tohoku University Dynamitron laboratory and optimization of the system was performed. Parasitic field contamination from tungsten carbide slit chips and an annular Si surface barrier detector limited the beam spot size to 2 × 2 μm2. By replacing these components, the parasitic field contamination of the system was reduced and the performance of the microbeam system was remarkably improved. A measured beam spot size of 0.4 × 0.4 μm2 at a beam current of several tens of pA has been accomplished. The results obtained using the grid shadow method show that a beam spot size of less than 0.4 μm is obtainable in the low-current regime. For easy tuning and operation of the microbeam system, a human–machine interface (HMI) was developed based on the user participatory design concept. The HMI has been accepted favorably by users and is used in routine operations. The analysis system has been re-developed and is applicable to simultaneous in-air/in-vacuum PIXE, RBS, SEM, and STIM analyses and 3D μ-CT. The system is now applied for studies in biological, environmental, and other fields.