Identification Techniques II: X-ray techniques and X-ray fluorescence with portable systems

Energy-dispersive X-ray fluorescence (EDXRF) portable spectrometers are becoming very popular in many fields for the on-site analysis of elements. This is mainly because EDXRF is a nondestructive, multielemental technique that is extremely well suited for the analysis of any material. An EDXRF spectrometer mainly consists of an X- or γ -ray excitation source, an X-ray detector with electronics, and a pulse-height analyzer. Recent technological developments have resulted in small, low-power, dedicated X-ray tubes, thermoelectrically cooled semiconductor detectors, and small pulse-height analyzers. Therefore, completelyportable EDXRF spectrometers are available that can be assembled on-site, having the size of a book and a weight ranging from as light as 500 g (using a radioactive source) to a few kilograms (using an X-ray tube). This article start with a short introduction to X- ray physics than reviews the present status of the development of X-ray radiograpy, X-ray diffraction and EDXRF portable systems in the field of Cultural heritage. The various components of a portable system are described: the radiation source, i.e. small, low-power, dedicated X-ray tubes or, alternatively, radioactive sources that emit X-rays or low-energy γ -rays; and X-ray detectors, i.e. proportional gas counters and semiconductor detectors, with special emphasis on the more recent thermoelectrically cooled X- ray detectors: Si-PIN (silicon positive-intrinsic-negative), Si-drift, CdTe, CdZnTe, HgI2, and others. Commercial systems are considered, and finally the most comon and significant applications are described, with particular emphasis to the field of works of art.