engleski

Development and construction of a mili/micro hand held instrument for X-ray fluorescence analysis

Introduction Hand-held instruments for X-ray fluorescence (XRF) analysis enable in situ investigations of objects regardless of their size, shape or place where they are located or exhibited (e.g. in case of application in cultural heritage field) and can be used under practically any conditions. However, typically these highly portable devices can be used to analyse only larger areas (diametar of ca. 1-2 mm and more) and are not equipped with X-ray optics to allow micro-XRF applications. The goal of this project was to develop and construct a hand-held XRF instrument, which, depending on the analytical needs, provides both mili and micro X-ray beam for sample excitation. Experimental The X-ray beam is provided by a low power end-window X-ray tube (50 kV, 0.2 mA) and the fluorescent radiation is collected by a Peltier cooled SDD with an energy resolution of ca. 140 eV. A motorized collimator interchanger switches between a pinhole collimator (spot size ca. 1.5 mm) and a polycapillary lens (spot size ca. 50 µm). The instrument’s component control and spectra acquisition is carried out via self developed software. The instrument is battery operated and therefore fully autonomous. Results Depending on the problem posed, it is possible to choose whether a mili or a micro X-ray beam will be used to excite the sample, thus allowing one to choose the size of the investigated area. When working in a micro-XRF mode a stand for the instrument, as well as a motorized 3D stage for precise positioning of a sample should be used. This micrometer stage also allows one to make predefined line and area scans and perform 2D elemental distribution mappings over the area of interest. Conclusions The combined use of a mili and micro X-ray beam in a single handheld device expands the versatility and potential usage of portable XRF instrumentation to an even wider range of applications. When in a mili mode it allows precise screening and bulk analysis, and when in a micro mode it allows micro-XRF applications for investigation of microsamples or microscopic details on a larger artefact. These possibilitites are demonstrated on a real object. Acknowledgements The research project is funded by the UKF fund (Unity through knowledge fund), with joint participation from the World Bank and the Croatian Ministry for science, education and sport. Special thanks to Prof. M. Schreiner (Academy of fine arts, Vienna) and Prof. P. Wobrauschek (Atomic institute, Vienna).

portable xrf; mili beam; micro beam

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