Shock temperature measurements in Mg₂SiO₄ and SiO₂ at high pressures

Abstract

Temperatures in the high pressure shock state have been determined by measurement of optical radiation from pure samples of forsterite (Mg2SiO4), α—quartz, and fused silica. Shock waves of known amplitude were produced by tantalum flyer impact using a two‐stage light gas gun. Shock pressures in the ranges 150‐175 GPa and 70‐115 GPa for Mg2SiO4 and SiO2 respectively were achieved, and temperatures in the range 4500‐6800 K were measured. The observed temperatures in Mg2SiO4 are consistent with the occurrence of a shock‐induced phase transition with a transition energy of ∼ 1.5 MJ/kg. Measured Hugoniot temperatures versus pressure in both fused and crystalline SiO2 shocked to the stishovite regime suggest the occurrence of a previously unknown transition, beginning at pressures of approximately 107 GPa and 70 GPa for α—quartz and fused quartz, respectively. The energies and temperatures appear to be consistent with the onset of melting of stishovite under shock loading.

Shock Vaporization and the Accretion of the Icy Satellites of Jupiter and Saturn

“…Shock temperatures were also calculated and compared with previous relatively low pressure data of Kormer (1968). Other work by Lyzenga and Ahrens (1980). Lyzenga et al (I983a,b), Ahrens et al (1982), Nellis et al (1984), and Boslough et al (1984) for a variety of solids and fluids demonstrate that upon comparing calculated and measured shock temperature TH versus shock pressure, P, the absolute value of TH at a given pressure was very sensitive to the total energy budget of the material (e.g.…”

Thermodynamically complete equation of state of MgO from true radiative shock temperature measurements on samples preheated to 1850 K

“…Metastable states in shock-compressed quartz and fused silica have been inferred by several groups on the basis of nonmonotonic trends in discrete (shock T versus P ) [104][105][106][107][108] or continuous (emitted radiant power versus time for decaying shocks) [104,105,108,109] data. Recent decaying laser shock experiments by Millot et al confirmed the anomalous response of quartz and fused silica but revealed no metastable states in directly shocked synthetic stishovite [19].…”

“…Indeed, that was the motivation to do these experiments. Instead, we must reason by analogy and estimate the potential degree of superheating upon shock melting of B1 phase MgO with reference to the melting behavior of those substances with properties similar to MgO whose static and dynamic melting behaviors are both well-studied: SiO 2 (fused silica, quartz, and stishovite) [19,[104][105][106][107][108][109], Mg 2 SiO 4 forsterite [106,110], and single-crystal aluminum [111,112].…”

Fiber optic diagnostics for Z-experiments

“…[3] The shock heated fiber temperature can be estimated from Equation of State tables for quartz [4]. Typical shock pressures on Zexperiments are in the 3 megabar range which corresponds to about 25,000 o Kelvin.…”