OCAS replaced its former EPMA with W-gun by a brand new FEG-EPMA equipped with an SXES (soft X-ray emission spectrometer) and Ar sputter gun. A field emission gun (FEG) typically achieves a probe size 1/2 to 1/8 smaller than a tungsten gun. In addition, the FEG can produce a probe current 20 to 100 times higher than the tungsten (W) gun with the same probe size. As such, a spatial resolution of 0.1 µm can be reached in optimum conditions, compared to 1 µm for a W gun. The new FEG-EPMA will have an improved analytical performance combining high lateral resolution and sensitivity.
On top, OCAS also invested in a soft X-ray emission spectrometer allowing for the detection of X-rays with energies as low as 50 eV. The Soft X-Ray Emission Spectrometer (SXES) is an ultra-high resolution spectrometer consisting of a newly-developed diffraction grating and a high-sensitivity X-ray CCD camera. It has a 10 fold better energy resolution than WDX and a 5 to 10 times better detection limit. This feature is especially of interest for light elements. The enhanced energy resolution also enables the analysis of the chemical state.
Moreover, an Ar sputter gun is present on the introduction chamber of the FEG-EPMA. It enables the removal al surface contamination prior to analysis. As such, “real” values of carbon concentration can be assessed.