Experimental results on tungsten-wire explosions in air at atmospheric pressure - Comparison with a one-dimensional numerical model

Experimental results on exploding tungsten wires in air at atmospheric pressure at current densities greater than or equal to 10(7) A.cm(-2) and a current rise greater than or equal to 10(10) A.s(-1) are presented. Besides the current through the probe and the voltage across it, the diameter of the wire material and its surface temperature have been measured. The final aim of this investigation is the determination of the thermophysical properties of a high-melting liquid metal up to its critical point. Here a first step should be made to demonstrate the reliability of the method and to justify the crucial assumptions. To determine the limits for the applicability of a homogeneous approach used so far, a one-dimensional numerical model in Z-pinch geometry has been used which gives the time evolution of the profiles of temperature, density, and pressure across the wire. The model describes well the main features observed in these experiments. A physical explanation for the maximum in the time dependences of the surface temperature is proposed. This behavior is related to special thermodynamic properties of a two-phase (liquid-gas) mixture forming in a peripheral layer around the liquid metal. The temperature limit is determined for which there are no remarkable gradients of temperature and density across the wire. The specific heat, the thermal expansion coefficient, and the electrical as well as thermal conductivity of liquid tungsten can now, in principle, be obtained. The parameters of the critical point of the liquid-vapor phase transition can also be estimated.