Outlook for future high-pressure shock experiments on minerals
Abstract
Recent technical progress in several areas related to shock wave experiments in geophysics is enabling a number of new classes of investigation. We will review three particular areas that promise to yield abundant high-quality data in the near future. The timing precision attainable with a simple and effective two-magnet projectile detector has turned out to be unexpectedly good. It enables shock experiments on targets pre-heated to temperatures 1400-1700 degrees C without the use of contact trigger pins at light gas gun shock pressures. The use of in-flight precision projectile detection and realtime computing yields calculated trigger signals to that are accurate to +/-100 ns and allow the highest resolution streak recordings. This development will enable much higher throughput of pre- heated experiments on silicate liquids, minerals, and metals in our lab. The method of data reduction for multichannel pyrometry recordings of shock temperature has been dramatically improved. The measurement of sample absorbance as outlined by Boslough (1989) permits direct calculation of emissivities vs. wavelength for semi-absorbent minerals and obviates previously required assumptions regarding grey-body radiation. As a result data uncertainties have decreased from typically +/- 500 K to +/-100 K for states in the ~5000 K range. This development should enable a new generation of high- precision shock temperature determinations, as well as retrospective re-analysis of archived data. Recently the superheating method of detection of shock melting discovered at Caltech has been extended to the sub-nanosecond shock state region using the laser-driven shock apparatus and appears to give radiance histories which are in complete agreement with much longer duration light gas gun experiments. The short duration laser-driven shock experiments have great possibility to study the details of shock-induced phase transformations and melting in the future.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMMR53D..01A
- Keywords:
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- 3611 Thermodynamics (0766;
- 1011;
- 8411);
- 3919 Equations of state;
- 3924 High-pressure behavior;
- 3944 Shock wave experiments