MHD Modeling of Plasma Generation and Radiation Transport Driven by the MG Field at the Metallic Surface

Abstract

Summary form only given. Recent experimental campaign at 1 MA (120 ns current rise time) Zebra pulse power generator reveals quite interesting dynamic picture of plasma production and evolution at the surface of the cylindrical metallic rods. Different rod diameters and rod materials have been explored. Multi-type plasma diagnostics included magnetic field probes, laser shadowgraphy, photodiodes, streak camera imaging etc. Radiation MHD modeling of plasma generation and evolution helps to interpret the experimental data and reveal additional features of plasma dynamics, hidden from direct experimental observations. Simulations have been performed with the Eulerian radiation and resistive two-temperature MHD code POS, modified to include both optically thin and optically thick plasma models into a single simulation. Radiation MHD modeling shows the generation of relatively hot and low-dense plasma fraction (that can be referred to as "corona") adjacent to the metallic surface, while the bulk of in plasma the metallic rod (or the "core") remains relatively cold, maintaining approximately the same mass density. Parameters of the coronal plasma depend on the road diameter and material used. This core-corona structure resembles the structure of the exploding wire. Simulations show that the coronal fraction of plasma is the main radiation emission source, while the intense radiation cooling keeps its temperature below 20 eV and prevents corona from further expansion after 80 ns. The intensity of the radiation transport in plasma has been compared against the kinetic transport effects, such as electron and ion thermal conductivities. Radiation post-processor of the radiation MHD code POS is used to resolve the radiation intensity versus the radiation wavelength and to rearrange the simulations data in the formats convenient for the direct comparison with such experimental data as the photodiode signals and streak-camera and laser shadowgraphy images.