Differentiating Sources of Non-Thermal ION Energy in Gas-Puff Z-Pinches Using Thomson Scattering

The conditions and dynamics of neon gas puff z-pinch plasmas near pinch time are studied on the COBRA pulsed power generator (current rise time of ~240 ns and ~0.9 MA peak current). A 526.5 nm, 10 J Thomson scattering diagnostic laser enables probing of the plasma conditions of these implosions with both spatial and temporal resolution. Plasma conditions imply that collective scattering spectral profiles will be observed, in which case electron and ion temperatures and plasma fluid element drift velocity can be obtained. The use of two laser pulses, both with a FWHM of 2.2 ns, that can be separated by 10ns allows observation of time-resolved spectra for a total consecutive time of ~6 ns in the present experiments. Spectra from the same scattering volume but collected by optics at differing angles with respect to the laser repeatedly imply ion temperatures that are inconsistent across viewing angles if the width of the ion features in the scattered spectral profile are interpreted as solely due to ion temperature. This indicates the presence of a source of non-thermal peak broadening that changes with scattering angle. Multiple methods of fitting the Thomson scattering spectral profile show that the presence of hydrodynamic drift velocity distributions in the plasma at stagnation can, together with ion temperature, give a better fit to the observed ion feature peak widths than ion temperature alone.