Temperature and x-ray diffraction measurements along the high-pressure Ta melting curve

Tantalum is a bcc metal at ambient conditions and up to its melting point along the principal Hugoniot. However, direct temperature measurements and measurements of its atomic structure off-Hugoniot do not exist. We present simultaneous x-ray diffraction, reflectivity, and surface temperature measurements of shock-released Ta. The Ta is initially shocked into the solid, solid-liquid coexistence, and liquid phases and its shock-released and subsequent reverberated states are measured with pyrometry and velocimetry. The surface temperature measurements suggest a change in the slopes of the release isentropes when they intersect the melting curve and the solid or liquid state is confirmed with x-ray diffraction. This method can be used to constrain the off-Hugoniot melting curve and structure of simple metals under dynamic compression.