Determination of the Grüneisen γ for Beryllium at 1.2 to 1.9 Times Standard Density
The curve that represents the locus of material states attainable directly by single-shock compression is termed a Hugoniot. Most existing very-high-pressure equation-of-state information is obtained by shock techniques and thus lies on that curve. The shocking process results in an increase in entropy. Thus the isotherm, the isentrope, and the Hugoniot, centered at a common initial-state point, correspond to successively higher energy states for a given material compression. The region in the pressure-volume plane between the principal isentrope and principal Hugoniot will be the subject of this report. That region will be investigated by using flash radiography to directly observe shocks and rarefactions in preshocked materials. The experiments to be described here will be interpreted in terms of the Mie-Grüneisen equation of State. Values of the Grüneisen parameter will be determined by comparing experimentally-attained states with states of corresponding volume on the principal Hugoniot. The results of different experimental techniques and different final compressions can thereby be reduced to a common basis of comparison — the Grüneisen parameter — and some conclusions concerning the high-pressure equation of State of beryllium can be formulated.
KeywordsIncident Shock Shock Velocity Regular Reflection Collision Angle Final Compression
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