Magnetically imploded cylindrical metal shells ( -pinch liners) are attractive drivers for experiments exploring hydrodynamics and properties of materials at extreme conditions. As in all -pinches, the outer surface of a liner is unstable to magneto Rayleigh-Taylor (RT) modes during acceleration, and large-scale distortion arising from RT modes could make such liners unuseable. On the other hand, material strength in the liner should, from first principles, reduce the growth rate of RT modes, and material strength can render some combinations of wavelength and amplitude analytically stable. A series of experiments has been conducted in which high-conductivity, soft, cylindrical aluminum liners were accelerated with 6-MA, 7-s rise-time driving currents. Small perturbations were machined into the outer surface of the liner and perturbation growth monitored. Two-dimensional magneto-hydrodynamic (2-D-MHD) calculations of the growth of the initial perturbations were in good agreement with experimentally observed perturbation growth through the entire course of the implosions. In general, for high-conductivity and soft materials, theory and simulation adequately predicted the behavior of magneto-RT modes in liners where elastic-plastic behavior applies. This is the first direct verification of the growth of magneto-RT in solids with strength known to the authors.

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The generation of pulsed high-energy-density plasmas by electromagnetic implosion of cylindrical foils (i.e., imploding liners or hollow Z pinches) has been investigated experimentally and theoretically at the Air Force Weapons Laboratory. The experimental studies involve discharging a 1.3-μsec 1.1-MJ capacitor bank through 7-cm-radius 2-cm-tall 3–30-mg cylindrical foil liners. Typical discharge parameters are 7–12-MA peak current and 1–1.5-μsec current rise time. Current and voltage waveforms indicate strong coupling of the load to the capacitor bank, and analysis of the waveforms indicates good implosion of the current sheath. Optical- and magnetic-probe measurements are consistent with 1–2-cm thickness of the imploding plasma shell and with final implosion velocities ∼15–20 cm/sec. Radiation-diagnostic measurements indicate ultrasoft x-ray yields ∼50–100 kJ with the FWHM of the photon pulse ∼80–100 nsec. The radiation data is consistent with a quasiblackbody spectrum (T∼30–50 eV) comprising most of the energy, with additional higher temperature and optically thin spectral components. Al11+ and Al12+ line and recombination radiation is frequently observed. Comparison of electrical, magnetic, and radiation data with one-dimensional MHD and two-dimensional MHD calculations is presented. The prospects for improving the performance with the present energy source and scaling to larger energy sources are briefly discussed.

Data are presented that are part of a first step in establishing the scientific basis of magnetized target fusion (MTF) as a cost effective approach to fusion energy. A radially converging flux compressor shell with characteristics suitable for MTF is demonstrated to be feasible. The key scientific and engineering question for this experiment is whether the large radial force density required to uniformly pinch this cylindrical shell would do so without buckling or kinking its shape. The time evolution of the shell has been measured with several independent diagnostic methods. The uniformity, height to diameter ratio and radial convergence are all better than required to compress a high density field reversed configuration to fusion relevant temperature and density.

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