Isentropic Compression of Substances Using Ultra‐High Magnetic Field: Zero Isotherms of Protium and Deuterium in Pressure Range up to ∼5 Mbar

Abstract

Experiments on isentropic compression of a substance using a high magnetic field pressure are described. Their goal is building of a zero isotherm in a multi-megabar pressures range. A method of the pressure and density determination of the compressed substance based on radiographic data obtained in the experiment is presented. The results of the experiments with solid (in initial state) protium and deuterium are presented. The densities that correspond to more than seventeen-fold compression are reached. Obtained experimental points are compared with extrapolation of a curve that is built in the experiments using anvil cells and with the results of several ab-initio calculations.

Isentropic compression of hydrogen: Probing conditions deep in planetary interiors

“…Our DFT-MD results agree very well with the quasiisentropic compression experiment of Boriskov et al 15 On the contrary, we cannot confirm those data of Fortov et al 13 that are located below the experimental and our theoretical cold curve. In particular, we find no signatures of a phase transition in the range of their predicted pressure-temperature data points.…”

“…However, a dynamic approach was chosen within the quasiisentropic experiment of Boriskov et al 15 They measured the density and simultaneously the pressure P (ρ) of the system via an aluminum layer in the vicinity of the sample using the experimental reference data reported in Ref. 46.…”

“…15 The sample in each experiment was compressed by high explosives using cylindrical or spherical symmetry. X-ray backlighting yielded the compression ratio and hence the density.…”

“…States off the principal Hugoniot curve can be investigated by varying the initial conditions via solid or gaseous targets, 10,11 applying reverberating shock waves, 7,8,12 or using isentropic compression that generates high pressures at moderate temperatures. [13][14][15] Isentropic compression also probes conditions along a planetary isentrope if the initial conditions are chosen appropriately. This would allow us to discriminate between competing planetary interior models.…”

A New Equation of State for Dense Hydrogen–Helium Mixtures

“…Dynamic quasi-isentropic shock wave experiments using high explosives on deuterium have been carried out up to about 1500 GPa (15 Mbar) and densities about 4.5 g cm −3 , directly probing jovian planet deep interiors. While, in some cases, both the density ρ and the pressure P (ρ) were measured simultaneously (Boriskov et al 2011), in other experiments only the densities were measured while the pressure was determined afterwards from a hydrocode with a model EOS (Fortov et al 2007). An extension of these latter experiments was carried out by Mochalov et al (2010) up ρ = 108 × ρ 0 = 4.3 g cm −3 , reaching an unprecedented experimental pressure for D 2 of 1800 GPa (18 Mbar).…”