Wavelength dispersive x-ray spectrometer WDS

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. 

Wavelength dispersive X-ray spectrometry (WDS) for a more detailed elemental analysis of samples in the SEM. JEOL Four-Crystal Spectrometer attached to the JSM-35C SEM can be used for l-pm spot analysis, digital and analog line scans, and X-ray image mapping, elements detection from Be to U, minimum detection limit of 0.01% by weight, fully quantitative results by extended cp-p-z. 

Wavelength dispersive X-ray fluorescence spectrometric (xrf) methods, 25 60 Wavelength dispersive spectrometer (WDS), 76 488, 26 433-434 Wavelength dispersive X-ray fluorescence (WDXRF)... 

An X-ray fluorescence spectrometer needs to resolve the different peaks, identify them and measure their area to quantify the data. There are two forms of X-ray spectrometers (Fig. 5.5), which differ in the way in which they characterize the secondary radiation - wavelength dispersive (WD), which measures the wavelength, and energy dispersive (ED), which measures the energy of the fluorescent X-ray (an illustration of the particle-wave duality nature of electromagnetic radiation, described in Section 12.2). 

The electron probe microanalyzer (EM or EPMA) uses 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 ESCA) and the emission of an X-ray photon. The X-ray photons emitted have wavelengths characterishc 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 XRE spectrometry... 

The instrumentation for EM uses the same type of X-ray spectrometers discussed in detail in Chapter 8, with an electron beam as the source and a UHV system that includes the sample compartment. An ED X-ray spectrometer allows the simultaneous collection and display of the X-ray spectrum of all elements from boron to uranium. The ED spectrometer is used for rapid qualitative survey scans of sample surfaces. The wavelength dispersive spectrometer has much better resolution and is used for quantitative analysis of elements. The WD spectrometer is usually equipped with several diffracting crystals to optimize resolution and to cover the entire spectral range. The electron beam, sample stage, spectrometer, data collection, and processing are all under computer control. 

Left Energy-dispersive X-ray system (EDX) with Si(Li) detector Right Wavelength-dispersive spectrometer (WDS) with bent crystal... 

Two different types of X-ray spectrometer exist wavelength- and energy-dispersive sjjectrom-eters (WDS and EDS, see Section 29.2.2.12.1), which can be used in either an X-ray microanalyzer (XRMA) or an SEM. 

As with X-ray fluorescence, the characteristic X rays are analysed using wavelength dispersive spectrometers (WDS) based on the selective reflection of radiation by a monochromator crystal. The related analytical performance levels are ... 

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... 

The phase compositions of the SHS products were characterized by using XRD, XRF and EPMA techniques. The morphologies of the products were characterized by electron probe microanalysis (EPMA, CAMECA SX-100) with using three WDS (Wavelength Dispersive Spectrometer) units. X-ray analyses of obtained alloys and slags were performed with Thermo Scientific Niton XL3t XRF device and PANalytical X Pert Pro PW3040/60 XRD device. 

Two different systems presently are utilized to detect and measure X-ray generation in electron beam instruments wavelength dispersive spectrometers (WDS) and energy dispersive spectrometers (EDS). 

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