DUELING PROBES: A COMPARISON OF FIELD EMISSION MICROPROBES WITH OLDER TUNGSTEN FILAMENT MICROPROBES

We compare sets of elemental data including suites of ultramafic meteorites , carbonate cemented sandstones and mudstones, and piston cylinder experiments, which have each been analyzed using the new, state of the art, field emission electron microprobe, as well as older, tungsten thermionic, electron microprobes. Since the development of electron microprobe over forty years ago, they have become an indispensable instrument for analytical investigations in the areas of metallurgy, mineralogy, chemistry, and biology. Our comparisons focus on data generated using the JEOL JXA 8530F housed in the Southeastern North Carolina Regional Microanalytical and Imaging Center (SENCR-MIC) with analyses of the same samples performed in other laboratories with tungsten filament electron microprobes. Current results indicate similar detection limits prevail. However, the advances in spatial resolution in terms of imaging and points of data generation allow for much refined assessments of micron-scale phase differences. Optimum analytical areas can be obtained at low accelerating voltages. A field emission microprobe can maintain a very small electron beam spot size even at low accelerating voltages, and, therefore, can take advantage to the greatly reduced interaction volumes obtained under these conditions. The smallest analytical areas are obtained at around 6-7 kV, for typical silicates, resulting in an analytical area of only a couple hundred nanometers.