External milibeam imaging applications at LAMFI-USP

(1) Institute of Physics, University of Sao Paulo, Rua do Matão, Tr. R 187, 05508-090, São Paulo, SP, Brazil
(2)
Proton micro and nanobeams for Ion Beam Analysis have become much of the attention, with astonishing results and over 400 publications since 1980. Millibeams however, though less complex to be implemented, have not earned equivalent recognition especially if considering its analytical potential. In a proton sub-millimeter beam the beam is kept steady and the sample is rastered by means of a precise XYZ stage. Such external millibeam has just been installed at LAMFI-USP. A ~3MeV proton beam is extracted to air through a 7 micrometer thin Al window (the Al 845 and 1014 keV gamma rays are used for charge normalization) onto a target installed on a wide range high precision (60.0000 ± 0.0005 cm) XYZ computer controlled stage. A star-like detector array with 2 X-ray detectors, a particle detector, a light spectrometer, laser for alignment and a CAM for pictures allows simultaneous measurements of the irradiated spot for several interesting applications. The combination of a sub-millimeter beam with the large range XYZ robotic stage is being used to produce elemental maps of large areas in samples like paintings, ceramics, stones, fossils, and all sort of samples. The precise positioning feature is especially important in the selection of points in TID studies in electronic devices irradiation. Due to its particular characteristics, this is one the few devices of its kind in the world, in the sense of a multi-technique ion beam analysis of large areas. The continuous development of the external beam setup coupled to the robotic XYZ stage at LAMFI, is becoming a robust and reliable option for regular analysis of trace elements (Z > 5) competing in most cases with the traditional in-vacuum Ion Beam Analysis, with the additional advantage of simpler sample loading and absence of vacuum constrains of the sample. The authors like to express the enormous help and dedication of R.F. Assis, A.R. Leite, and M.R. Antonio in the development of LAMFI’s external millibeam setup.