Acquisition of an Ultra-High Temperature Acoustic Interferometer

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9903070LangeThis grant provides partial support of the costs to acquire an ultrasonic acoustic interferometer for the High Pressure and Temperature Laboratory at the University of Michigan. This instrument will be used to measure the compressibilities of multicomponent silicate liquids. The ultra-high temperature capability of the apparatus ( 2000 degrees centigrade) will allow access to a wide range of melt compositions, including those with high liquidus temperatures (e.g. peraluminous liquids, molten peridotite) and those that are too viscous to obtain relaxed sound speeds below 1600 degrees centigrade (e.g. molten rhyolite). Constraints on the temperature dependence of melt compressibility will be substantially improved by measuring relaxed sound speeds over temperature intervals spanning several hundered degrees. The interferometer will also be used at lower temperatures on volatile-bearing liquids (containing fluorine and phosphorous) and a variety of carbonatite liquids under conditions where it is established that volatile loss does not occur. An additional application is to examine variations in the compressibility of silicate melts undergoing composition-induced coordination change of cations (Al3+, Fe3+, and Ti4+) at one bar. These experiments will provide analogies for understanding the consequences of pressure-induced coordination change of these cations on melt density. In addition to the P.I., Rebecca Lange, other faculty at the University of Michigan who are likely to utilize the equipment in their research include Associate Professors Youxue Zhang and Lars Stixrude. This will be the first acoustic interferometer that is capable of ultra-high temperature work on liquids and is thus likely to attract outside users throughout the U.S.***