Wavelength dispersive x-ray spectrometer

An energy-dispersive X-ray spectrometer and at least one wavelength-dispersive X-ray spectrometer... 

Before the development of semiconductor detectors opened the field of energy-dispersive X-ray spectroscopy in the late nineteen-sixties crystal-spectrometer arrangements were widely used to measure the intensity of emitted X-rays as a function of their wavelength. Such wavelength-dispersive X-ray spectrometers (WDXS) use the reflections of X-rays from a known crystal, which can be described by Bragg s law (see also Sect. 4.3.1.3)... 

Part VI Wavelength Dispersive X-ray Spectrometers , Anal. Proc.,... 

Recent studies on iron sulfide minerals in coals, minerals in coals, and in situ investigation of minerals in coal all used the scanning electron microscope (SEM) as the primary analytical tool. The ion microprobe mass analyzer (IMMA) is more sensitive than either the energy-dispersive x-ray spectrometer or the wavelength-dispersive x-ray spectrometer, both of which are used as accessories to an electron microscope. 

A Jeol-35 Scanning Electron Microscope equipped with energy-and wavelength- dispersive X-ray spectrometers was used for elemental analysis. Spot analyses were carried out these covered approximately 0.5 pm for the pyrite and 1 pm for the coal. The standard atomic number, absorption and fluorescence (ZAF) corrections were applied to all analyses, using counting times of 200 seconds, an accelerating voltage of 15 kV and a pyrite crystal as standard. 

In this analysis, three wavelength-dispersive X-ray spectrometers were used to simultaneously measure the characteristic X-ray intensities for copper, barium, and yttrium, at each point in the scan, producing two-dimensional X-ray intensity arrays. Complete quantitative analysis corrections, using the NBS theoretical matrix correction procedure FRAME (2), were performed at each picture element (pixel) in the image scan. 

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). 

Abstract. Modern elemental analysis using wavelength-dispersive x-ray spectrometers ensures a nondestructive and environmentally safe analytical method. All the elements of the periodic table from beryllium to uranium can be determined using qualitative, semi-quantitative and quantitative measurements in solids, powders and liquids. Depending on the specific application (element and matrix), concentrations from the 0.1 ppm level up to 100% can be analyzed. Advantages of x-ray fluorescence (XRF) analysis include easy and fast sample preparation, multielement capability, high precision and reproducibility, and very short measuring times. 

Light element analysis by XRF is applied in very different scientific and industrial fields. Boron analysis with modern x-ray spectrometers is very important in the semiconductor, ceramic and glass industries or in geosciences. Determination of beryllium in bronze could be an interesting application for XRF analysis in the future. Modern wavelength-dispersive x-ray spectrometers achieve the analytical capability to analyze beryllium in bronze with a limit of detection (= LLD) lower than 0.1%, boron in glass with a LLD of 0.04% and carbon in steel or cement below 100 ppm. 

From what has been described above it is obvious that the unfiltered, thick anode, x-ray tube offers considerable flexibility in achieving broadband excitation. Once the appropriate anode material has been selected, the question of the optimum tube voltage and current settings arises. Fundamental differences in the characteristics of the energy-dispersive and wavelength-dispersive x-ray spectrometers lead to different criteria for choosing the optimum tube voltage and current. 

Analytical Methods Committee (1990) Evaluation of analytical instrumentation. Part VI. Wavelength dispersive X-ray spectrometers. Analytical Proceedings 27 324-333. 

In a wavelength dispersive x-ray spectrometer (WDS) the x-rays fall on a bent crystal and are reflected only if they satisfy Bragg s law. The crystal is set to focus x-rays of one specific wavelength onto a detector and rotates to scan the wavelength detected. Only one element can be detected at a time with one crystal. The resulting WDS spectra are quite sharp and elemental overlap is minimal due to the good signal to noise ratio. 

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