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 presen ted. Besides the current through the probe and the voltage across it, the diameter of the wire material and its surface temperature have bee n measured. The final aim of this investigation is the determination o f the thermophysical properties of a high-melting liquid metal up to i ts 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 u sed so far, a one-dimensional numerical model in Z-pinch geometry has been used which gives the time evolution of the profiles of temperatur e, density, and pressure across the wire. The model describes well the main features observed in these experiments. A physical explanation f or the maximum in the time dependences of the surface temperature is p roposed. This behavior is related to special thermodynamic properties of a two-phase (liquid-gas) mixture forming in a peripheral layer arou nd the liquid metal. The temperature limit is determined for which the re are no remarkable gradients of temperature and density across the w ire. The specific heat, the thermal expansion coefficient, and the ele ctrical as well as thermal conductivity of liquid tungsten can now, in principle, be obtained. The parameters of the critical point of the l iquid-vapor phase transition can also be estimated.