Analysis of phase transformations in shock-compressed potassium chloride and $\alpha$-quartz in terms of x-ray crystallography

X-ray diffraction patterns of shock-compressed samples of potassium chloride and $\alpha$-quartz were analyzed in order to estimate the physical state of the substance in the phase coexistence region and the effect of the relaxation process on the location of experimental Hugoniot points in this region. The experimental results are consistent with the interpretation that the state of a substance on the transition curve connecting the Hugoniots of the initial phase and the high-pressure phase can be represented as a state of the substance with an incomplete relaxation process. The degree of incompleteness is determined by the ratio of the residence time of the substance at the shock front to the full time of the relaxation process.