The inverse Z-pinch as a physics test bed, and, possibly, a target plasma, for magnetized target fusion (MTF)

Abstract

Summary form only given, as follows. From an overall fusion system perspective, the possibility of compressing a magnetized target plasma with beta greater than unity by a magnetically driven imploding liner, or other target pusher driver, appears very exciting. This approach, known as magnetized target fusion (MTF), operates in a density regime that is intermediate between the twelve orders of magnitude in density that separate MFE and ICF. Even if plasma transport is Bohm-like, the MTF parameter space appears accessible with existing drivers, i.e., MTF does not require a major financial investment in driver technology. The confinement directly by material walls and the thermal transport of magnetized, high-beta plasma in the MTF regime has been studied only a little, theoretically, computationally, and experimentally. We are computationally evaluating, using the well-benchmarked two-dimensional radiation-MHD code MHRDR, and other tools as appropriate, the inverse z-pinch as an experimental test bed to study MTF transport and confinement. Existing facilities being considered include the 2terawatt Zebra generator at the Nevada Terawatt Facility, the Colt capacitor bank at LANL, and the Atlas capacitor bank at LANL. According to MHRDR, the plasma is expected to evolve into a near-equilibrium. Thin sheaths next to the outer cylinder and end walls contain steep temperature and density gradients. The plasma should take microseconds to cool, even in the presence of considerable convection. This cooling rate is much slower than would result if free-streaming losses of ions or unmagnetized-electron conduction losses were present. Experimental verification and understanding of the energy transport in this simple wall-confined plasma would provide increased confidence in the design of integrated liner-on-plasma experiments. We are also evaluating the inverse z-pinch as an MTF target plasma for integrated liner-on-plasma experiments.