Conductivity and Permittivity of Hydrogen Under Isentropic Magnetic Compression up to 3 Mbar

An experimental technique for isentropic compression of solid and liquid substances up to ultrahigh pressures is discussed. A pulsed ultrahigh magnetic field up to 1000 T is produced by an explosive flux-compression generator MC-1. A smooth shock-free pulse of pressure in a coaxial metal chamber of few cubic centimeters is obtained. A radio-frequency technique of conductivity and permittivity measurement is applied. The conductivity of solid hydrogen isentropically compressed with the initial temperature less that 14 K was estimated at about 1 (Ohm m)(-1) under the pressure of 3 Mbar. A sharp rise of the relative permittivity as a precursor of a metal-insulator transition was observed.