Phase transition in a strongly nonideal deuterium plasma generated by quasi-isentropical compression at megabar pressures

High-explosive driven generators of cylindrical and plane shock waves in D2 and H2 were used for the generation of warm and dense strongly nonideal matter with an intense interparticle interaction and Fermi statistics. Highly resolved flash x-ray diagnostics were used to measure the adiabatic plasma compressibility. The thermodynamic measurements demonstrated the 20% increase of density at megabar pressure, just in the density range, where the electrical measurements indicated a sharp--5 orders of magnitude--increase of electrical conductivity due to pressure ionization in strongly coupled plasmas.