title: Multishock Compression Properties of Warm Dense Argon.
abstract: Warm dense argon was generated by a shock reverberation technique. The diagnostics of warm dense argon were performed by a multichannel optical pyrometer and a velocity interferometer system. The equations of state in the pressure-density range of 20-150 GPa and 1.9-5.3 g/cm(3) from the first- to fourth-shock compression were presented. The single-shock temperatures in the range of 17.2-23.4 kK were obtained from the spectral radiance. Experimental results indicates that multiple shock-compression ratio (ηi = ρi/ρ0) is greatly enhanced from 3.3 to 8.8, where ρ0 is the initial density of argon and ρi (i = 1, 2, 3, 4) is the compressed density from first to fourth shock, respectively. For the relative compression ratio (ηi' = ρi/ρi-1), an interesting finding is that a turning point occurs at the second shocked states under the conditions of different experiments, and ηi' increases with pressure in lower density regime and reversely decreases with pressure in higher density regime. The evolution of the compression ratio is controlled by the excitation of internal degrees of freedom, which increase the compression, and by the interaction effects between particles that reduce it. A temperature-density plot shows that current multishock compression states of argon have distributed into warm dense regime.
authors.affiliation: Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan, P. R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan, P. R. China.
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan, P. R. China.
authors.forename: Gu
authors.initials: G
authors.lastname: Yunjun
authors.affiliation: Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan, P. R. China.
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Li
authors.affiliation: Laboratory of computational Physics, Institute of Applied Physics and Computational Mathematics, P. O. Box 8009-26, Beijing, P. R. China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Shen