Adaptation of existing facilities to isentropic compression experiments
We demonstrate that the established pulsed power infrastructure at the National High Magnetic Field Laboratory - Pulsed Field Facility (NHMFL-PFF) at the Los Alamos National Laboratory can be adapted to obtain high quality isentropic compression experiment (ICE) data on materials in extreme conditions of dynamic high pressure. Experiments utilized a single-turn magnet pulsed power system at the NHMFL-PFF that was originally designed to measure actinide samples in extremes of high magnetic field (to 300 Tesla). A simple modification to the single-turn magnet has converted it to a fast turnaround dynamic high pressure measurement system. This paper details the work done including important background details that indicate that much more can be accomplished with optimization of the load characteristics in terms of ultimate peak pressures. To match the rise time of the NHMFL capacitor bank ({approx}2 {mu}s versus {approx}0.5 {mu}s for the Sandia Z-machine) the sample dimensions can be relatively large, i.e., up to 5 mm thickness. The maximum stresses are {approx}50GPa (0.5 Mbar) at the maximum bank voltage (60 kV) and higher pressures may be possible if the sample is tamped. For the design and predictions of performance of the NHMFL-ICE experiment it is important to have good predictive models. A SPICE code simulation was chosen to model all aspects of the experiment, electrical and physical. To this end, accurate dynamic load models were developed to simulate the compression and expansion of the dynamic load at high pressures using shock physics principles. A series experiments have been performed which demonstrated the feasibility of the NHMFL-ICE technique. The results will be shown and discussed. The NHMFL-ICE technique is an excellent method for measuring equations of state (EOS) at megabar pressures. Because a complete EOS can be obtained in one experiment from zero to the peak pressure, and because many shots can be fired in one day, the technique promises to provide high quality EOS data at relatively low cost.