Investigating the Time Evolution of Plasma Density Structures in the ZaP-HD Flow Z-pinch

Abstract

The Sheared-Flow-Stabilized Z-pinch is understood to be a promising plasma confinement configuration for applications in fusion energy. The application of a radial velocity shear offers stabilization against the Magneto-Rayleigh-Taylor instability, which causes classical Z-pinch plasmas to collapse at the densities and temperatures required for thermonuclear fusion. This thesis aims to characterize the spatiotemporal evolutions of electron density structures in the ZaP-HD Flow Z-pinch device using a 4-chord laser interferometer. The interferometer is based on a modified Mach-Zehnder configuration, and employs heterodyne and quadrature signal processing techniques. The most significant deviation from the standard Mach-Zehnder is the use of scene and reference beams with unequal path lengths. Data from a benchtop proof-of-concept experiment is provided to demonstrate the functionality of the unequal path configuration. The region of interest for this investigation is the segment of the pinch extending 20-30 centimeters axially downstream of the outlet of the coaxial accelerator in the ZaP-HD device, which is responsible for producing the radial shear. Data from an earlier science campaign is briefly discussed as motivation for the study of density structures in this specific region. Interferometer data is presented and analyzed to obtain characteristic scale lengths of density gradients. Analysis of the interferometer data is supported by data from a fast-framing camera and azimuthal magnetic field probes.