Characterization of Plasma Properties and Turbulence in Gas-Puff Z-Pinch Implosions

This study aims to better understand the non-thermal component of ion kinetic energy in gas-puff Z-pinch implosions produced using Ne and Ar gases on the 1 MA, 100-220 ns rise time COBRA pulsed power generator. Previous experiments have shown that close to stagnation time, spectroscopic analysis of this non-thermal component [1] suggests that turbulence provides a physically meaningful description. Moreover, the assumption of turbulent flow improves the analysis of Thomson scattering data, as supported by the findings in Ref. [2]. A recently published study [3] found that the non-thermal kinetic energy term is inconsistent with laminar velocity gradients.

To investigate the non-thermal ion kinetic energy in more detail, the current study employs the recently developed Imaging Refractometry technique [4]. This method is a variation of schlieren imaging and enables the measurement of the spectrum of angular deflections of a laser beam that can be linked to the wavenumber spectrum [5] as it propagates through the plasma. The Imaging Refractometer is being used with a visible light streak camera to provide time resolution and a time-integrated CMOS sensor based camera to provide spatial resolution of the wavenumber spectrum. Also, a 3D Beam Propagation Method (BPM) simulation [6] was developed to analyze the measured results and compare with synthetic ones where turbulence was artificially introduced.

Spatially resolved and time-resolved measurements obtained with the Imaging Refractometer along with BPM simulations will be presented and discussed.