Experimental Measurement of Surface Motion and Emission on Metal Rods Driven by Intense Current

Complex plasma-material interactions are found in many fusion and HEDP experiments that may dramatically affect the performance of the device through both material and MHD instabilities. Accurate modeling of electrically driven conductors is challenging due to uncertainties in the equation-of-state (EOS) and electrical conductivity during the metal-insulator transition. Photonic Doppler velocimetry was used to measure the surface motion of extremely smooth mm-diameter 5N Al rods driven to 0.8 MA in 100 ns by the Sandia Mykonos generator. For the first time, uncoated Al rods were measured to compress 40 nm radially before expanding. Subsequently, the reflective surface experiences several changes in acceleration during the current rise. Taking advantage of PDV's sensitivity to multiple simultaneous velocities, the time dependence of the distribution of velocities in the reflective material is being investigated. Visual emission data from photodiodes and streaked-visual-spectroscopy diagnostics is being used to investigate the temperature and radiation of the metal rods. The experimental measurements are being used to benchmark MHD calculations, and thereby inform the choice of EOS and conductivity tables for modeling.