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A series of experiments to study the behavior of thick wires (0.5–2 mm in diameter) driven by currents of about 1 MA has recently been conducted on the Zebra facility at the University of Nevada, Reno. The objective of these experiments was to study plasma formation on the surface of conductors under the influence of megagauss magnetic fields. Laser shadowgraphy, filtered optical and extreme ultraviolet photodiodes, and extreme ultraviolet spectroscopy used in the experiments provided data on radial expansion of wires and on plasma radiation. This paper focuses on numerical simulations of these experiments. Simulations with wires having diameters up to 1.6 mm demonstrated plasma formation with temperatures above 3 eV, which is in preliminary agreement with the experiment. For 2-mm-diameter wires, although plasma can be observed in the simulations, it has substantially smaller optical thickness than in the simulations of the smaller diameter wires, and the radiation fluxes prove to be much lower. This can shed light on the experimental results where the radiation of the 2-mm wires was very weak. The simulated time dependences of the wire radii agree rather well with the experimental results obtained using laser diagnostics and visible-light imaging. The experimental data of the photodiodes also agree well with the simulated time dependence of the detected radiation. [ABSTRACT FROM PUBLISHER]

An alternative concept for fusion energy production is magnetized target fusion using metal liners to compress a mixture of magnetic flux and plasma fuel. In liner flux compression experiments, megagauss fields are produced at peak compression that heats the surfaces of aluminum walls of the liner cavity. Some radiation magnetohydrodynamic (MHD) modeling indicates that plasma formation should occur between 3 and 5 MG; however, such modeling depends on assumed material properties, which are a topic of ongoing research. Load hardware and diagnostics have been developed to study metal vapor and plasma formation on aluminum surfaces subjected to pulsed megagauss fields on the University of Nevada Zebra facility. The experiment is designed to study this interesting threshold for plasma formation. A current of 1 MA is pulsed along a stationary central rod to generate magnetic fields of 2-4 MG. The goal is to observe and diagnose the formation of metal vapor and plasma in the vicinity of the rod. The simple geometry enables easy access by diagnostics, which include magnetic sensors, filtered photodiode measurements, optical imaging, and laser schlieren, shadowgraphy, and interferometry. From these measurements, the magnetic field, the temperature of the surface metal plasma, the radiation field, and the growth of instabilities can be inferred. The diagnostics are time resolved to individually examine the distinct phases of heating, surface plasma formation predicted by radiation MHD modeling, and instability. [ABSTRACT FROM AUTHOR]

Describes the use of resonant laser scattering to detect ion plasma waves in multiply ionized, laser-produced plasma. Problems inherent in the detection of ion plasma waves; Minimization of frequency smearing of the scattered signal by plasma gradients; Comparison of the theoretical dispersion relation with the wave data.

Examines the onset of stimulated Brillouin scattering (SBS). Variation of the effective F number of the optical system used to irradiate a performed longitudinally uniform hydrocarbon (CH) plasma; Quantitative comparison between theory and experiment; Implications for the National Ignition Facility.