Zhou Xian-Ming

Restudy of Grüneisen Parameter of Iron in the Pressure Range of 90-160 GPa

The Hugoniot equation-of-state (EOS) of porous iron with an average initial density of 6.904 g/cm3 has been measured in the pressure range from 90 to 160 GPa, and a good straight fitting D = 2.997 + 1.603 u has accordingly been obtained, where D is the shock wave velocity and u the particle velocity, both in units of km/s. Combining this with the Hugoniot EOS of non-porous iron, the Gruneisen EOS and the Rankine-Hugoniot energy conservation relation, and taking the possible solid-liquid transition correction, we have calculated the Gruneisen parameter γ of iron and obtained the result γ0ρ0 = γρ = const, with γ0 = 1.945 and ρ0 = 7.856 g/cm3, ρ being the density. PACS: 62. 50. +p, 65. 90. +i, 91. 35. -x

Sound Velocities in Porous Iron Shocked to 177 GPa and the Implications for Shock Melting

Sound velocities in shock-loaded solids are not only important to determine bulk moduli of solids at high pressures, but are also crucial to inform the shock melting of solids upon loading. In this letter, we first report on shock melting of porous solids at high pressures by measuring sound velocities in the porous iron of average density 6.90 g/cm3 in the pressure range of 110-180 GPa. The measured sound velocity softens at pressures from 122 to 156 Gpa, which may be attributed to shock melting of the porous iron.

Equation of state of fluid helium at high temperatures and densities

Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2, and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., theD ≈u relation,D=C0+λu (u<10 km/s, λ=1.32) in a low pressure region, is approximately parallel with the fittedD ≈u (λ=1.36) of liquid helium from the experimental data of Nellis et al. Our calculations show that the Hugoniot parameter λ is independent of the initial densityρ0. TheD≈u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10−3.

Opacity of Shock-Generated Argon Plasmas

Argon plasmas with uniform density and temperature are generated by a planar shock wave through argon gas. The opacities of argon plasma, covering the thermodynamic states at temperatures of 1.4-2.2 eV and in densities of 0.0083-0.015 g/cm3, are investigated by measuring the emitted radiance versus time at several visible wavelengths. Comparison of the measured opacities with those calculated demonstrates that the average atom model can be used well to describe the essential transport behaviour of photons in argon plasma under the above-mentioned thermodynamic condition. A simplified and self-consistent method to deduce the reflectivity R(λ) at the baseplate surface is applied. It demonstrates that the values of R(λ) are all around 0.4 in the experiments, which are basically in agreement with those given by Erskine previously (1994 J. Quant. Spectrosc. Radiat. Transfer 51 97).