Free-surface velocity measurements of opaque materials in laser-driven shock-wave experiments using photonic Doppler velocimetry

We present a novel photonic Doppler velocimetry (PDV) design for laser-driven shock-wave experiments. This PDV design is intended to provide the capability of measuring the free-surface velocity of shocked opaque materials in the terapascal range. We present measurements of the free-surface velocity of gold for as long as similar to 2 ns from the shock breakout, at pressures of up to similar to 7 Mbar and a free-surface velocity of 7.3 km/s with an error of similar to 1.5%. Such laboratory pressure conditions are achieved predominantly at high-intensity laser facilities where the only velocity diagnostic is usually line-imaging velocity interferometry for any reflector. However, that diagnostic is limited by the lower dynamic range of the streak camera (at a temporal resolution relevant to laser shock experiments) to measure the free-surface velocity of opaque materials up to pressures of only similar to 1 Mbar. We expect the proposed PDV design to allow the free-surface velocity of opaque materials to be measured at much higher pressures. (C) 2021 Author(s).