Pressure-produced ionization of nonideal plasma in a megabar range of dynamic pressures

The low-frequency electrical conductivity of strongly nonideal hydrogen, helium, and xenon plasmas was measured in the megabar range of pressures. The plasmas in question were generated by the method of multiple shock compression in planar and cylindrical geometries, whereby it was possible to reduce effects of irreversible heating and to implement a quasi-isentropic regime. As a result, plasma states at pressures in the megabar range were realized, where the electron concentration could be as high as n(e) approximate to 2 x 10(23) cm(-3), which may correspond to either a degenerate or a Boltzmann plasma characterized by a strong Coulomb (Gamma(D) = 1-10) and a strong interatomic (Gamma(a) = r(a)n(a)(1/3) similar to 1) interaction. A sharp increase (by three to five orders of magnitude) in the electrical conductivity of a strongly nonideal plasma due to pressure-produced ionization was recorded, and theoretical models were invoked to describe this increase. Experimental data available in this region and theoretical models proposed by various authors are analyzed. The possibility of a first-order phase transition in a strongly nonideal plasma is indicated. (C) 2003 MAIK Nauka / Interperiodica.