Quasi-isentropic compression of dense gaseous helium at pressures up to 500 GPa

Thermodynamic properties of a nonideal helium plasma at quasi-isentropic compression by a factor of 575 at a pressure of 3000 GPa

“…8 in (pres sure-density) coordinates along with the data from [16,24]. Isentropes 1 and 2 in this figure describe the result of this work and the experiment [16], respec tively.…”

“…7 (in (pressure-compression) coordinates) along with the data on the compressibility of helium in spherical [14][15][16] and cylindrical [24] setups.…”

“…Gryaznov with the SAHA He pro [14][15][16] at the equal pressure in both cavities P 01 = P 02 ≈ 25 MPa and (*) in cylindrical setups [24]. The calculations: (dashed line) with a variable pressure in the inner cascade at a constant pressure of the gas in the outer cavity P 01 = 40 MPa, () P 01 = P 02 = 40 MPa, and (solid line) approximation of the data from [16].…”

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

“…3), melting (15,16) and solid-solid insulator-conductor transformation in Xe (18,19). Prior data are squares (conductivity) (13,17,22,54) or circles (absorptivity) (12,18) with red indicating σ < 1 S/cm, α < 0.1 μm −1 , and black indicating σ > 1 S/cm, α > 0.1 μm −1 ; black triangle is region of anomalous emission in Ar (29); red (black) crosses indicate insulating (metallic) electrical behavior in Xe (19); and black diamond indicates dense plasma conditions in He (24). Also shown are interior conditions of Jupiter (brown) (6), Saturn (blue) (7), and white dwarfs (green) for effective temperatures of 8.0, 6.5, and 4.5 × 10 3 K (9).…”

“…Ne is predicted to have the highest metallization pressure of all known materials-10 3 times that of Xe and 10 times that of He (14,18,20,21)-and has never been documented outside of its insulating state. Experimental probes of extreme densities and temperatures in noble gases have previously relied on dynamic compression by shock waves (12,13,17,(22)(23)(24). However, in such adiabatic experiments, light and compressible noble gases heat up significantly and can ultimately reach density maxima (12,13,17,21,24,25), so that conditions created often lie far from those deep within planets (7,8) and stars (9).…”