Portable and Handheld Systems for Energy‐Dispersive X‐ray Fluorescence Analysis

Abstract

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, completely portable 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). These spectrometers can be employed for on‐site analysis in various fields, such as works of art, alloys, soil, environmental samples, forensic medicine, paper, waste materials, mineral ores and their products, or anywhere a portable apparatus would be required. This article reviews the present status of the development and application of EDXRF portable systems. 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 (Positive‐Intrinsic‐Negative), Si‐drift, CdTe, CdZnTe, HgI 2 , and others. Commercial systems are considered, and finally the most common and significant applications are described, with particular emphasis to the field of works of art.

Non-Invasive Characterisation of the Wall Paintings in the Byzantine Church of Palazzo Simi (Bari, Italy) and Digital Photogrammetric Survey for a Pigment Mapping

“…Low counts of the characteristic emission Kα line of Ni, Cu and Zn were always present in the background of the acquired spectra due to the instrument components (slit and case). Considering the operating condition (40 kV and 95 µA), the target (Au) used, the working distance (1.5 cm) and the elements identified-assuming a composition similar to plaster for wall painting, due to the laws of absorption-the depth analysed was less than 300 µm, for, e.g., Fe [55]. The real situation was, of course, much more complicated, and depended on the pigment present and surface coating [56].…”

A novel portable energy dispersive X-ray fluorescence spectrometer with triaxial geometry

“…Even though it has the disadvantage of reducing even more the beam's intensity, a compromise has to be made between the collimator apertures and the intensity of the resulting spectra. Figure 1b presents the structure piece to couple the X-ray tube [1] to the secondary target [2] and the collimator for the outgoing beam [3]. This piece was developed in aluminum and inwardly and outwardly covered with lead for shielding [4].…”

“…Energy Dispersive X-ray Fluorescence (EDXRF) is a well established laboratory technique and constitutes one of the few atomic spectroscopy techniques that can be used for portable instrumentation. Piorek [1], Cesareo et al [2,3], and more recently Bosco [4], reported the history of the development of portable XRF spectrometers: the first-generation instruments appeared in the 60 s, which used radioisotopes and targeted at single element detection such as sulfur in oil [1]. In the 80 s, the third-generation portable energy dispersive spectrometers with semiconductor detectors was developed [2] and in the 90s, the size reduction of the devices has been accelerated due to the development of personal computers, detectors, and batteries [4].…”

“…Piorek [1], Cesareo et al [2,3], and more recently Bosco [4], reported the history of the development of portable XRF spectrometers: the first-generation instruments appeared in the 60 s, which used radioisotopes and targeted at single element detection such as sulfur in oil [1]. In the 80 s, the third-generation portable energy dispersive spectrometers with semiconductor detectors was developed [2] and in the 90s, the size reduction of the devices has been accelerated due to the development of personal computers, detectors, and batteries [4]. An important step, the miniaturization of the X-ray tube, was achieved by insulating the tube with resin or ceramic instead of insulating oil.…”

Multi-Element Analysis by Portable Total Reflection X-ray Fluorescence Spectrometer

“…It is not only due to the increment of the background intensity, but also due to the detector saturation caused by the highly intense scattered X-rays of non-monochromatic X-rays from a high power X-ray source. Considering a typical X-ray tube working at 30 -40 kV, it emits bremsstrahlung radiation at the order of a few units × 10 7 photons/μA s. 23 The maximum count rate of a Si-drift detector is up to 10 6 counts/s. Although the detector can be used for the non-monochromatic X-rays from the high power X-ray source, shaping time should be shortened in order to make a measurement at the maximum count rate.…”