Electrophysical properties of water and ice under isentropic compression to megabar pressures

The relative permittivity and specific conductivity of water and ice are measured under isentropic compression to pressures above $300$ GPa. Compression is initiated by a pulse of an ultrahigh magnetic field generated by an MK-1 magnetocumulative generator. The sample is placed in a coaxial compression chamber with an initial volume of about $40$ cm$^3$. The complex relative permittivity was measured by a fast-response reflectometer at a frequency of about $50$ MHz. At the compression of water, its relative permittivity increases to $\varepsilon=350$ at a pressure of $8$ GPa, then drops sharply to $\varepsilon=140$, and further decreases smoothly. It is shown that measurements of the relative permittivity under isentropic compression make it possible to determine interfaces between ordered and disordered phases of water and ice, as well as to reveal features associated with a change in the activation energy of defects.