Quantitative Bulk and Trace Element X-Ray Mapping Using Multiple Detectors

Moran, Ken; Wuhrer, Richard

doi:10.1007/s00604-006-0507-z

Cited by 21 publications

(20 citation statements)

References 2 publications

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“…Traditionally, the EDS is used for fast elemental analysis to determine what elements are present and the WDS then utilised to acquire precise major and trace elemental quantitative analysis. The WD spectrometers exhibit far better spectral resolution than the conventional EDS, as can be seen in figure 1 [1,6].…”

Section: Microanalysis (Eds and Wds)mentioning

confidence: 96%

“…The combination of EDS and WDS produces a very powerful analytical technique also allowing for excellent quantitative X-ray mapping (QXRM) [1][2][3][4][5]. Traditionally, the EDS is used for fast elemental analysis to determine what elements are present and the WDS then utilised to acquire precise major and trace elemental quantitative analysis.…”

Section: Microanalysis (Eds and Wds)mentioning

confidence: 99%

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A new life for the wavelength-dispersive X-ray spectrometer (WDS): incorporation of a silicon drift detector into the WDS for improved quantification and X-ray mapping

Wuhrer

Moran²

2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The wavelength-dispersive X-ray spectrometer (WDS) has been around for a long time and the design has not changed much since its original development. The electron microprobe operator using WDS has to be meticulous in monitoring items such as gas flow, gas purity, gas pressure, noise levels of baseline and window, gas flow proportional counter (GFPC) voltage levels, count rate suppression, anode wire contamination and other detector parameters. Recent development and improvements of silicon drift detectors (SDD's) has allowed the incorporation of a SDD as the X-ray detector in place of the proportional counter (PC) and/or gas flow proportional counter (GFPC). This allows minimal mechanical alteration and no loss of movement range. The superiority of a WDS with a SDD, referred to as SD-WDS, is easily seen once in operation. The SD-WDS removes many artefacts including the worse of all high order diffraction, thus allowing more accurate analysis. The incorporation of the SDD has been found to improve the light and mid element range and consequently improving the detection limit for these elements. It is also possible to obtain much more reliable results at high count rates with almost no change in resolution, gain and zero-peak characteristics of the energy spectrum. IntroductionThe electron probe microanalyser (EPMA) instrument has been around for a long time, which utilises the X-ray microanalysis techniques of wavelength-dispersive and energy-dispersive X-ray spectrometry (WDS and EDS). The WDS design has not changed much since its original development. WDS exhibits far better spectral resolution than the conventional EDS. The combination of EDS and WDS produces a very powerful analytical technique allowing for excellent quantitative X-ray mapping (QXRM). However, the electron microprobe operator using WDS has to be meticulous in monitoring items such as gas flow, gas purity, gas pressure, noise levels of baseline and window, gas flow proportional counter (GFPC) voltage levels, count rate suppression, anode wire contamination and other detector parameters.Over the last couple of years we have been developing and testing alternative configuration WD spectrometers, using Amptek PIN (p-intrinsic-n type diode) and silicon drift detectors (SDD's) in place of the sealed proportional counter (SPC) and gas flow proportional counters (GFPC's) respectively.

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Section: Microanalysis (Eds and Wds)mentioning

confidence: 96%

Section: Microanalysis (Eds and Wds)mentioning

confidence: 99%

A new life for the wavelength-dispersive X-ray spectrometer (WDS): incorporation of a silicon drift detector into the WDS for improved quantification and X-ray mapping

Wuhrer

Moran²

2018

IOP Conf. Ser.: Mater. Sci. Eng.

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“…Images are then created from the fully background corrected, overlap corrected and inter-element corrected calculation at each pixel in the image. As there is a very large dynamic concentration range to be considered (5 orders of magnitude) it is important to understand that the precision at each level will depend on how well this characterization is carried out [1]. To achieve this, time is no longer an issue but a means to accomplish a more precise result.…”

mentioning

confidence: 99%

“…One interesting outcome of this is that we now need to improve the collection efficiency of our WDS detectors to enable them to perform at these lower beam currents [1][2][3]. To take advantage of this increased precision and sensitivity of QXRM, careful attention to all those parameters necessary for high quality analysis is required.…”

mentioning

confidence: 99%

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Dedicated X-Ray mapping system with single and multiple SDD detectors for quantitative X-Ray mapping and data processing

Wuhrer

Moran²

2015

Microsc Microanal

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A JEOL 840 SEM/EDS system has been converted into a dedicated X-Ray Mapping (XRM) instrument, due to the needs of many users from varying disciplines including materials science and engineering, biology, geology and environmental science. The system performs 24 hours-7 days per week XRM electron microscopy (XRMEM). The system has just been upgraded with an Amptek 123 FAST123 silicon drift detector (SDD) with an Ultra Thin C1 window to allow for faster mapping. The XRMEM is setup to maximize its ability to operate with a larger working distance so that the instrument can perform x-ray maps at very low magnifications and high pixel resolution (1024x1024). This is now requested by a large number of users. With the use of the high count rate detectors, such as the Amptek SSD, our research team is collecting XRM's from over 3 hours and up to several days; this is especially true when trace elemental analysis and mapping is required.Quantitative X-ray mapping (QXRM) using multi-detectors and combined detectors, such as WDS/EDS, not only reduces mapping time, but also improves the ability to map minor and trace elements very accurately. One interesting outcome of this is that we now need to improve the collection efficiency of our WDS detectors to enable them to perform at these lower beam currents [1][2][3]. To take advantage of this increased precision and sensitivity of QXRM, careful attention to all those parameters necessary for high quality analysis is required. Important characteristics such as resolution, gain zero calibration, pulse pileup and other artifacts need to be well characterized for each detector used. Images are then created from the fully background corrected, overlap corrected and inter-element corrected calculation at each pixel in the image. As there is a very large dynamic concentration range to be considered (5 orders of magnitude) it is important to understand that the precision at each level will depend on how well this characterization is carried out [1]. To achieve this, time is no longer an issue but a means to accomplish a more precise result. Thus, if we can introduce more efficient detection then we can achieve this result in a shorter time. This may be achieved by counting more x-rays with one detector, as long as the critical quantitative characteristics of the detector is not compromised, or this can easily be achieved by adding more detectors.For QXRM to work correctly for multi-detector systems, the characteristics of each detector must be accurately determined so that the final quantification of the individual detectors can be summed. To accomplish this more effectively, the full spectrum at each pixel for each SDD detector should be saved. As a final check for consistency between detectors, a technique was developed called "Colouring Verification Technique (CVT)" that involves assigning a different RGB colour for each detector for the same element (Fig. 1). When combining the three maps of the same element, a grey scale map should be obtained (Fig. 1), not a colour map. This ind...

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