Zeeman splitting measurements of local magnetic fields in wire z-pinch plasmas

Abstract

Summary form only given. Wire z-pinch experiments at the University of Michigan are in progress to test potential spectral lines for use as a local magnetic field diagnostic in dense plasmas driven by high currents. The goal of these experiments is to determine several spectral lines that can be used to reliably characterize the magnetic field and current density profiles of high energy density plasmas. Initial feasibility experiments were performed on a compact pulser, in which 50-60 kA currents were conducted in a single wire with 400 ns risetime. A lower-inductance, higher-current pulser is currently under construction. An optical fiber collected visible light emission from the wire ablation plasma for measurement by a timegated ICCD coupled to a 0.75-m optical spectrograph. Spectra have been collected for several plasmas including W, Mo, Na, and Al. Magnetic fields of 5-6 T have been measured using Zeeman splitting.In planned experiments, several optical fibers will be placed along a planar foil on the UM 1-MA LTD (Linear Transformer Driver) and local magnetic field measurements will be taken using spectral lines from the feasibility experiments. Laser shadowgraphy has previously been used to image the foil plasma for measurement of the MRT (Magneto Rayleigh-Taylor) instability growth rate [1]. Anisotropy of the planar foil plasma MRT growth is seen in the shadowgraphs; localized magnetic field measurements are expected to yield more insight into this effect.