Energy dispersive XRF spectrometer

The light-weight Elva-X energy dispersive XRF spectrometer employed for this study has an air-cooled rhodium target anode X-ray tube with 140 micron Be window and a thermoelectrically cooled Si-PIN diode detector. The detector... 

The analyses were performed at The Henry Francis du Pont Winterthur Museum on a Kevex 4525P energy dispersive XRF spectrometer low-level radioactive isotopes were used for the incident radiation (4). The pigment area analyzed was successively irradiated by an iron-55 source, an americium-241 source, and a cadmium-109 source. A qualitative pigment analysis takes only 6 min. Neither the coloring matter nor the silk fabric is altered in any way by the measurement. Figure 8 shows our XRF system setup for the analysis of pigments on painted and printed silks. 

All three types can be found in use in cement works control laboratories, but the preferred system is the multichannel type fitted with channels for the simultaneous determination of the eight elements Fe, Ca, K, S, Si, Al, Mg, and Na. Depending on the local geology, a chaimel for the determination of fluorine may be fitted if the limestone deposit is close to a source of fluorspar (CaF2). (The determination of fluorine is beyond the scope of an energy-dispersive XRF spectrometer.) At some works a channel is added to monitor the chlorine content of the clinker, which can be introduced from the fuel used to fire the kiln. 

Since the equipment used in XRF technique including radioisotope source is portable, the energy dispersive XRF spectrometers are used in various divergent fields like that in the metal industry, in gold mines, in oilfields for oil analysis (to determine sulfur in petroleum products and residual catalysts, monitor additives in lubricating oils, analyze regular wear metal in lubricants... 

In 2006, a table-top energy-dispersive XRF (ED-XRF) spectrometer was acquired by the Archaeometry Lab to facilitate non-destructive analysis of obsidian and other types of artifacts. One of the first projects performed on the new XRF spectrometer was the re-analysis of the geological samples from sources in Peru. As a result, it is now possible for the Archaeometry Lab to use either XRF or NAA to successfully determine the provenance of obsidian artifacts from Peru. Due to its light weight, the spectrometer also has the potential to be transported from the laboratory to museums and to archaeological sites for in situ analysis. 

Fig. 11.15 Energy-dispersive XRF spectrum of a multi-element standard, obtained in a TXRF spectrometer.

Qualitative analysis is, in principle, very simple with XRF and is based on the accurate measurement of the energy, or wavelength, of the fluorescent lines observed. Since many WD-XRF spectrometers operate sequentially, a 20 scan needs to be performed. The identification of trace constituents in a sample can sometimes be complicated by the presence of higher order reflections or satellite lines from major elements. With energy-dispersive XRF, the entire X-ray spectrum is acquired simultaneously. The identification of the peaks, however, is rendered difficult by the comparatively low resolution of the ED detector. In qualitative analysis programs, the process is simplified by overplotting so called KLM markers onto... 

ABSTRACT X-ray spectroinetty (XRF) is a versatile instrumental method for elemental analysis in a wide variety of materials. The performance of three different XRF systems will be con sared a high power wavelength dispersive x-ray spectrometer (WDXRF), a low-power WDXRF, and a bench-top energy dispersive instrument (EDXRF). 

Energy Dispersive (ED) or Wavelength Dispersive (WD) XRF spectrometer 15,000-150,000 Very common... 

The electron probe microanalyzer (EM or EPMA) nses a beam of high-energy electrons to bombard the surface of a solid sample. This results, as we have already seen, in the removal of an inner shell electron. As discussed in Section 14.2, this can result in the ejection of a photoelectron (the basis of XPS) and the emission of an X-ray photon. The X-ray photons emitted have wavelengths characteristic of the elements present. The EPMA uses either a wavelength dispersive (WD) or energy dispersive (ED) X-ray spectrometer to detect and identify the emitted X-rays. This is very much analogous to XRF spectrometry (Chapter 8), where the primary beam was of X-rays, not electrons. This instrument was discussed at the end of Chapter 8, which should be reviewed if necessary. 

In order to find out the phase composition of fine laterite ore reduced with reduction temperature of 1375°C, the atomic ratio of C/O of 1.2, and the percentage of CaO of 12%, the samples were examined by X-Ray fluorescence(XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS). The chemical compositions of the fine ore by reduction-magnetic separation was shown in Table 3.1, the XRD pattern of fine ore by reduction-magnetic separation was seen in Fig.3.5, and the SEM pattern of fine ore by reduction-magnetic separation was shown in Fig.3.6 and the chemical compositions of observed district in SEM pattern was shown in Table 3.2. 

Inert sampling could be done when desired. Zr, W and Ni were determined by XRF, Ti and Cr by neutron activation analysis (NAA), Mg by AAS, C with a Leco carbon analyzer and Cl by potentiometric titration. FTIR in diffuse reflectance mode was used to follow the chemisorption and to detect possible decomposition of the reactant. Scanning electron microscopy with an energy dispersive spectrometer (SEM/EDS) was used to determine element concentrations through the particles. The specific surface area and pore volume were determined by means of nitrogen adsorption and condensation with Micromeritics ASAP 2400 equipment. Detailed experimental conditions used in the characterization are in Ref. 16. 

In most XRF spectrometers an X-ray tube is used as the photon source. Alternatively radioactive isotopes can be applied for the excitation of the characteristic X-rays from the sample. X-ray tubes can be used in both wavelength-dispersive and energy-dispersive systems. Due to their lower beam intensities, application of radionuclides is restricted to energy-disp>ersive systems. 

XRF spectrometers have two major objectives (a) to determine the spectral distribution of the X-rays emitted from the sample (b) the measurement of the intensity of the selected spectral component. In wavelength-dispersive XRF, the spectrum is dispersed into different wavelengths by Bragg diffraction at different crystals. Intensities are measured by electronic detectors. In energy-dispersive spectrometers both energy dispersion and intensity measurement are performed by electronic detectors thus for... 

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