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3.7 Methodological Developments

The continuing development of new experimental apparatus and techniques allows the Geoinstitut to remain at the forefront of experimental research in the Geosciences. Development of new apparatus and modification of existing equipment to meet new requirements demand not only scientific insight and innovation in design, but also a high level of technical expertise. The Geoinstitut is only able to make such advances due to the high quality of our technical support in the areas of sample preparation, machining and electronic design. In the last year, a new shear-wave generator has been designed and constructed that will revolutionise our ability to measure elastic wave velocities and elastic constants for small samples, such as those produced in high-pressure apparatus. This new technology is particularly exciting, given our recent success using GHz transducers with diamond-anvil cell technology to perform elastic constant measurements at high pressures. Significant progress has also been made in applying electron energy loss spectroscopy to the analysis of small samples fabricated at very high pressures and temperatures, providing insight into the oxidation state of the lower mantle and the partitioning of ferric iron between the dominant mineral phases.

The Geoinstitut is one of the institutes in which electrical conductivity measurements have been made successfully at very high pressures. Recently, this technology has been applied to monitor the effects of grain size on semiconductor-metal transitions in nanocrystalline semiconductors at high pressures. In-situ techniques have also been developed for the measurement of volume changes for fluid-bearing molten samples at high pressure, permitting continuous monitoring of the process of vesiculation during depressurization, as occurs during volcanic eruptions. Modifications to the fragmentation apparatus allow improved measurement of fragmentation speed during rapid depressurization. The effects of shock waves on calcite have been studied with a device for that generates shock waves using high explosives. Such measurements are important in understanding the effects of natural impacts on past climate on Earth, such as when the Chicxulub bolide impacted calcite-rich rocks around 66 million years ago. Further development and refinement of nuclear magnetic resonance as an analytical tool in the Geoinstitut has lead in the last year to improved simulation of spectra and the complete characterization of the bonding structure in several chemical compounds.