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NanoSims

The Cameca NanoSIMS 50L arrived at the Open University in April 2007. This is the latest generation of Secondary Ion Mass Spectrometer (Ion Microprobe) instrumentation, allowing high sensitivity compositional analyses of up to 7 species (elements, molecules or isotopes) simultaneously at a nominal spatial resolution of down 50 nm, and with high mass resolution (>6000 M/ΔM).

The instrument consists of two primary ion beam sources (oxygen and cesium), an optical microscope with CCD camera, a secondary electron imaging system, 7 movable/adjustable electron multipliers for high sensitivity (ppb level) and 3 Faraday Cups for high abundance multi-collection measurements. The secondary ions are produced by sputtering the sample surface with impinging high-energy primary ions. All detectors are located in the focal plane of the large magnetic sector mass analyser. Primary and secondary ions are focused through co-axial optics that are normal to the sample surface. Sample erosion is minimal, compared to earlier instruments, such as the Cameca ims 6f with a spatial resolution of ~1 μm. This allows the analyses of very thin sections (in the order of ~50-100 nm), such as those produced with a Focused Ion Beam Scanning Electron Microscope for Transmission Electron Microscopy. Sputtering is not necessarily an unwanted side effect, as it can be used to obtain three-dimensional depth profiles.

The NanoSIMS requires ultrahigh vacuum (<10-7 torr). Two sample holders can be stored within the UHV system; an airlock system permits reasonably rapid exchange of new sample holders.

This is only the 17th NanoSIMS instrument to have been installed worldwide, almost half of which work in areas of cosmochemistry such as the study of isotopic anomalies of micron to sub-micron-sized presolar grains. The CEPSAR instrument will be used to perform high spatial resolution isotopic problems in:

•  Primitive meteorites

•  Martian and lunar samples

•  Cometary material brought back by Stardust

•  Interplanetary dust particles

•  Terrestrial rocks

•  Experimental analogues and simulations

•  Other materials – biological and materials

 

Samples must be conductive and non-degassing, and should be mounted on various suitable sample mounts (or should have the same dimensions). Samples must not be too rough; ideally, they are pressed into the conductive substrate or polished.

 

 

Contact Information

Lead Academic - Dr Ian Franchi

i.a.franchi@open.ac.uk

Telephone: +44 (0) 1908 655173 (office)

 

Laboratory Manager -

@open.ac.uk

Telephone: +44 (0) 1908 ****** (office)