Abstract
Laser diagnostics provides powerful tools for the investigation of dense Z-pinches. In this paper, wire-array Z-pinches are investigated at the 1 MA Zebra generator using laser diagnostics at different wavelengths coupled with x-ray diagnostics. Plasma dynamics during the ablation, implosion, and stagnation stages are observed by multiframe diagnostics. Cascading and nonprecursor implosions are studied in wire arrays. Ultraviolet diagnostics allows deep penetration into the Z-pinch plasma at stagnation. End-on probing reveals the complicated structure of the precursor. Strong magnetohydrodynamic instabilities are found in a dense pinch hidden in the trailing plasma. Small-scale instabilities are seen in the Z-pinch plasma with micrometer resolution. Probing of the pinch from four directions shows asymmetrical trailing plasma in some configurations of wire arrays. Faraday rotation diagnostics reveals the magnetic fields and the current distribution in the plasma of the precursor and Z-pinch. Redistribution of current in the trailing plasma is seen during kink and sausage instabilities in the stagnation stage. The formation of micropinches and hot spots in the Z-pinch is analyzed with coupled laser and x-ray diagnostics. Different laser diagnostics allow the study of Z-pinch plasmas in all stages, including fast dynamics and instabilities.
Highlights
Z-pinches are efficient laboratory sources of powerful x-ray radiation
Wire-array Z-pinches are investigated at the 1 MA Zebra generator using laser diagnostics at different wavelengths coupled with x-ray diagnostics
Plasma dynamics during the ablation, implosion, and stagnation stages are observed by multiframe diagnostics
Summary
Z-pinches are efficient laboratory sources of powerful x-ray radiation. They can be applied in a number of areas of high-energy-density laboratory plasma physics, including laboratory astrophysics, atomic and radiation physics and spectroscopy, studies of material properties, and fusion research. there has been impressive experimental progress in Z-pinch physics and its applications at currents of 10–20 MA, many aspects of the physics of dense Z-pinches can be studied at load currents in the range 1–2 MA. Faraday rotation diagnostics has allowed the investigation of magnetic fields and reconstruction of the current distribution in wire arrays. The main features of the formation and evolution of the dense pinch and trailing mass have been studied with laser diagnostics at a wavelength of 532 nm. Laser diagnostics in the optical range cannot be applied to the stagnation phase of Z-pinches owing to strong absorption and refraction of the laser beam in the dense plasma. UV high-resolution diagnostics is deployed at the 1 MA Zebra generator and allows detailed investigation of the stagnation stage in a dense Z-pinch. The structure of the magnetic fields is revealed and the redistribution of current in the trailing plasma and Z-pinch is reconstructed using Faraday diagnostics. Laser probing in four directions reveals strong asymmetry of some wire-array Z-pinches. The dynamics of implosion and stagnation and the development of instabilities in Z-pinches are in agreement with three-dimensional MHD simulations
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