An Experimental Design for Measuring P, V, T, and Conductivity Simultaneously

We have designed an experiment in which it appears that we can measure the pressure, volume, temperature, and electrical conductivity of a metal simultaneously. These data aid in the modeling of conductivity and equation-of-state relations for metals that are driven to extreme states, for example in z-pinches, imploding liners, or high-power electrical fuses. Recent advances in the technique of measuring the temperature of a surface with variable spectral emissivity can produce measurement accuracy of a few percent. The experiment is arranged so the fuse material investigated is subject to one-dimensional movement only. In addition, conditions must be such that the state parameters are nearly uniform throughout the region being measured. In one such arrangement, a thin planar foil is sandwiched between two pieces of lithium fluoride and a suitably large current is passed through the foil. The initial heating is not one- dimensional due to the time required for the magnetic field to diffuse into the foil; however, for certain geometries of the foil (such as 3 cm wide and 0.008 cm thick), the conditions at the center of the foil satisfy the conditions of one-dimensionality after a few microseconds. The displacement of the foil interface with the lithium fluoride allows the computation of the density of the foil material (typically copper or aluminum). The velocity of the surface together with the known equation of state of the lithium fluoride gives the pressure at the interface and, by the one-dimensionality of the conditions, the pressure through the center of the foil. The conductivity is measured by measuring the electric field using voltage probes, with the current density inferred from a local measurement of the magnetic field at the surface of the foil. Other fuse geometries such as rods or cylindrical foils are also candidates for the experiment. Detailed two-dimensional calculations of the current and material flow have been performed and will be discussed.