Turbulence in Gas-Puff Z-Pinch Implosions*

The studies over the last decade have shown that close to stagnation time, spectroscopic analysis of the non-thermal component of the ion kinetic energy [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 [2]. A recently published study [3] found that the non-thermal kinetic energy term is inconsistent with laminar velocity gradients.

In this study, we demonstrate the direct experimental evidence of the turbulent gas-puff z-pinch implosion. We use the imaging refractometer [4], which is sensitive to density fluctuations and measures the phase correlations in the transverse laser beam profile. By applying statistical analysis [5] to the images, we show that the phases are randomized and that laser speckle patterns emerge, which necessitates random density distribution. Moreover, we employ the XMHD PERSEUS code in 3D on the Bridges-2 supercomputing facility [6] to achieve high spatial resolution. These simulation runs indicate the need for Hall physics, and we have also used an anomalous resistivity model based on the lower-hybrid-drift instability, to achieve a good match to the experimental results.