Portable ART Analyser (PART)

X-ray fluorescence (XRF) analysis is one of the most widely used analytical techniques for the scientific study of cultural heritage today. Its biggest advantage is the non-destructiveness of the investigation, providing not only qualitative information on the composition of an object but often also (some) quantitative information. Recent developments enabled the construction of portable XRF systems of various types, some focussed on flexibility, others on easy mobility. Nevertheless, one of the still unsolved problems during in situ analysis - where low energy radiation is absorbed in air - is the detection of low Z elements. The Kunsthistorisches Museum (KHM) with its affiliated institutions, the Museum of Ethnology Vienna and the Austrian Theatre Museum holds extensive collections of highly valuable objects - often unique in the world. Within this rich variety of outstanding (art) historical objects the materials, forms and sizes, and restrictions for transport are manifold offering a wide range of applications for in situ XRF analysis. Therefore, an XRF instrument capable for the use at the KHM has to be highly flexible, easy to move, and has to possess a broad elemental detection range. Recently a prototype portable XRF instrument was constructed at the International Atomic Energy Agency (IAEA), Seibersdorf Laboratories, together with the Atominstitut der Österreichischen Universitäten Wien (ATI). By using a vacuum chamber, designed to house the measuring head, the problem of the detection of low Z elements is to be solved. Through a Kapton window the investigated spot can be focussed at about 1-2 mm distance outside of the chamber, therefore, minimising absorption losses in the excitation and x-ray fluorescence radiation paths. Test measurements applying this instrument at the KHM showed the need for several improvements, especially concerning: the detection limits of low Z-elements (i.e. sodium) for the investigation of glass and enamel, the size and shape of the vacuum chamber, the bending of the vacuum window, the flexibility and positioning of the whole instrument, and the fast evaluation of the in situ analysis. Therefore, within this project, an improved portable XRF instrument will be developed and constructed that meets the high demands of the KHM based on a co-operation of the Conservation Science Department of the Kunsthistorisches Museum (KHM), the Atominstitut der Österreichischen Universitäten Wien (ATI), and the International Atomic Energy Agency (IAEA), Seibersdorf Laboratories. This improved instrument will be used for performing some selected case studies on the composition of unique and valuable artworks with an emphasis on the investigation of glass and enamel as well as of pigments and metal alloys. For example a collection of 16th century glass jewellery from the area of Archduke Ferdinand II, the collection of so called "Rudolfinisches Email", and about 30 enamelled gold and silver objects of the 15th and 16th centuries will be investigated concerning the glass/enamel composition. In addition, analyses of metal objects - e.g. the collection of Renaissance and Baroque bronzes held in the Collection of Sculpture and Decorative Arts and of ancient Sasanian silver coins - and partly complexly shaped paper objects from the Austrian Theatre museum will be done in connection to ongoing research projects, scientific studies and conservation work.

X-ray fluorescence (XRF) analysis is one of the most widely used analytical techniques for the scientific study of cultural heritage today. Its biggest advantage is the non-destructiveness of the investigation, providing not only qualitative information on the composition of an object but often also (semi-) quantitative information. In a co-operation of the Conservation Science Department of the KHM (Kunsthistorisches Museum Vienna) with the ATI (Atomic Institute of the Vienna University of Technology) and the IAEA (International Atomic Energy Agency) a portable XRF instrument was designed and constructed, optimized to cope with the diverse analytical problems of a wide-spread museum collection as it is kept at the KHM. This new system is focused on the detectability of low-Z elements (from sodium onwards), portability, safety of the objects (e.g. stability) and good accessibility to object details.The resulting instrument is mounted on a stable frame with steerable and lockable wheels for transportation. The measuring head is mounted on three electronically controllable translation stages in x-, y- and z-direction. In the z-direction (up and down) the traverse amounts 100 cm, in x- and y-direction 20 and 30 cm, respectively. These large traverse distances are necessary to be able to analyze also big objects or paintings. The new design of a stable stand combined with the ability of moving the measuring head very flexible (allowing an overhang up to 40 cm in the forefront of the frame) enables measurements with fewer restrictions to the size and shape of the objects and their holders. For the detection of the low-Z elements a measuring head with a vacuum chamber was employed. The refinement in reference to a precursor model regards on the one hand its design which is based on the need of good accessibility to the different parts of the museum objects: A conical shape with a tip was employed. On the other hand the fixation of the Kapton window was enhanced, avoiding bending of the window, when the vacuum is employed. The air gap between the chamber window, where the x-ray beams pass through, and the sample is about 1 mm, minimizing absorption losses in the excitation and x-ray fluorescence radiation paths and enhancing the sensitivity for light elements.For the operation of the equipment three x-ray tubes (Pd, Mo and Cr) are available. They can be used depending on the analytical problem. During the project time it could be shown, that the detection limits could be improved in comparison to the precursor instrument. Also the improvement of the positioning possibilities could be tested in several applications. The new portable art analyzer (PART) was used successfully in a great diversity of applications like: pigment analysis in paintings and on other surfaces like ceramics, lime stone and marble; analysis of glass, glace and enamel; investigations of different metals of coins and medals; investigations on the presence of inorganic pesticides; investigations on the presence of purple.