Generating high energy density plasmas using the flow Z-pinch concept

Abstract

Summary form only given. The ZaP Flow Z-pinch experiment <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Profiles of the plasma's axial flow are measured with a multi-chord ion Doppler spectrometer. A sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by the following diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ; and fast framing photography for global structure. Recent experimental modifications demonstrate that the plasma lifetime appears to only be limited by plasma supply and current waveform. With a new gas injection configuration, stable plasmas persist for the duration of the current pulse. The flow Z-pinch concept provides an approach to achieve high energy density plasmas <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> (HEDP), energy densities exceeding 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Pa, which are large, easy to diagnose, and persist for longer durations. A new experiment, ZaP-HD, will investigate this approach. Experimental plans and scaling analyses will be presented.