Examining energy partitioning in gas-puff z-pinches using Thomson scattering *

The conditions of 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, 2.3 ns (FWHM) Thomson scattering diagnostic laser enables probing the plasma conditions with spatial and temporal resolution. Electron and ion temperatures, flow velocity, and electron density can be obtained from the ion acoustic and electron plasma wave features. Splitting the laser into two pulses allows observation of time-resolved spectra for more of the implosion time. Spectra from the same scattering volume but collected by optics at differing angles to the laser imply ion temperatures that are inconsistent across viewing angles if the width of the ion features in the spectral profile are interpreted as only due to ion temperature. This suggests an additional source of peak broadening that scales with angle. Multiple methods of fitting the Thomson scattering spectral profile show that the presence of flow velocity distributions in the plasma at stagnation can, along with ion temperature, give a better fit to the observed ion feature peak widths than ion temperature alone.