A calibration procedure for the detection efficiency of energy dispersive X-ray spectrometers (EDS) used in combination with scanning electron microscopy (SEM) for standardless electron probe microanalysis (EPMA) is presented. The procedure is based on the comparison of X-ray spectra from a reference material (RM) measured with the EDS to be calibrated and a reference EDS. The RM is certified by the line intensities in the X-ray spectrum recorded with a reference EDS and by its composition. The calibration of the reference EDS is performed using synchrotron radiation at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt. Measurement of RM spectra and comparison of the specified line intensities enables a rapid efficiency calibration on most SEMs. The article reports on studies to prepare such a RM and on EDS calibration and proposes a methodology that could be implemented in current spectrometer software to enable the calibration with a minimum of operator assistance.

In order to maintain the thermo-mechanical durability of ITER it is proposed to castellate the interior surface of the first wall and divertor by splitting them into small-size cells [W. Daener et al., Fusion Eng. Des. 61&62 (2002) 61]. A concern is the accumulation of fuel in the gaps of the castellation. In TEXTOR, molybdenum limiters were exposed in the scrape-off layer (SOL) plasma to assess fuel accumulation. The first limiter was exposed under deposition-dominated conditions. Carbon deposits were formed both on top surfaces and in the gaps. About 0.12% of the impinging D-fluence was found in the gaps. Another castellated limiter was exposed under erosion-dominated conditions. Deposited layers were found only on the plasma shadowed areas of the gaps. A significant amount of molybdenum from the limiter was found intermixed in the deposit. The gaps contained $0.03% of the impinging D-fluence. Modeling was performed to simulate carbon transport into the gaps.

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Performing X-ray microanalysis at beam energies lower than those conventionally used (`10 keV) is known to signi®cantly improve the spatial resolution for compositional analysis. However, the reduction in the beam energy which reduces the Xray interaction diameter also introduces analytical dif®culties and constraints which can diminish the overall analytical performance. This paper critically assesses the capabilities and limitations of performing low beam energy, high spatial resolution X-ray microanalysis. The actual improvement in the spatial resolution and the reduction in the X-ray yield are explored as the beam energy is reduced. The consequences for spectral interpretation, quantitative analysis and imaging due to the lower X-ray yield and the increased occurrence of X-ray line overlaps are discussed in the context of currently available instrumentation.Conventionally, X-ray microanalysis on scanning electron microscopes (SEM) with energy dispersive spectrometers (EDS) has been performed with relatively high primary energies (b 10 keV). For most samples this results in reasonably good separation of the generated X-ray line series from different elements enabling unambiguous identi®cation and therefore accurate qualitative analysis. Under these circumstances it is widely accepted that quantitative analysis of polished bulk samples is possible on a routine basis with relative errors around 1 ± 57 and detection limits of the order of 0.1 wt7. A new generation of high resolution ®eld emission gun (FEG) SEM instruments which can operate with much improved beam sizes at low beam energies (E P ) down to and below 1 keV has opened a wide range of new applications in surface and materials characterisation. The instruments, which are as straightforward to operate as conventional high vacuum SEMs, provide a new, more detailed and realistic view of surfaces. Additionally, the capability of investigating insulating samples without the requirement of a conductive coating becomes possible by utilising low E P operation.The ability of these instruments to maintain high spatial resolution performance at low E P when providing suf®cient beam current to enable practical microanalysis, in conjunction with the ultra-thin window energy dispersive spectrometers (EDS) has also opened new possibilities for materials characterisation. In particular, the analysis of new advanced materials with thin layers and sub-micron features appear to be realistic goals.In general, according to the literature there are several improvements connected with the application of beam energies below those conventionally used for microanalysis, i.e. E P`1 0 keV: ± The electron range and thus the information depth in X-ray microanalysis signi®cantly decreases with decreasing E P and enters the magnitude of a few 10 nm. ± Owing to the small beam diameters in FEG SEMs and the shrinking excitation volume the lateral resolution for X-ray microanalysis can theoretically be improved by reducing E P . ± The analysis sensitivity of near-surface features such as...