Electrode gauge as an instrument for studying shock compression and metallization of the substance

An electrode gauge for particle velocity is used to study condensed substances that acquire high electrical conductivity under shock compression. Thin metallic electrodes are placed into the substance. A shock wave propagates over the substance along the electrodes in a transverse magnetic field. A moving conducting substance closes the electrodes and generates an electromotive force on them. To justify the operation principle of the electrode gauge, the electrical conductivity of selenium and aluminum powders is measured. The high electrical conductivity of the powders (up to $\approx$10$^4$ $\Omega^{-1}$ $\cdot$ cm$^{-1}$) allows the electrode gauge to be used for determining the kinematic characteristics of the shock wave. The voltage on the electrodes is proportional to the mean value of particle velocity in the probing conducting layer located directly behind the shock front. Introduction of additional electrodes into the measurement cell allows the wave velocity to be found. This technique is used to plot the shock adiabats of selenium and aluminum powders of different densities. The experimental data obtained are presented as linear dependences of wave velocity on particle velocity. For a powder with large particles, the thickness of the probing layer is commensurable with the shock-transition width. This offers a possibility of using the electrode gauge to study the structure of the shock transition and the phase of substance metallization.