Sources of Ion Acoustic Wave Feature Broadening in the Thomson Scattering Spectrum of Gas-Puff Z-Pinches

Ion acoustic wave (IAW) feature broadening in collective Thomson scattering in neon gas-puff z-pinch plasmas is investigated on the COBRA pulsed power generator (rise time ~240 ns to 0.9 MA peak current). A 526.5 nm, 10 J, 2.3 ns Thomson scattering diagnostic laser enables probing of the plasma conditions with < 1 mm spatial and < 1 ns temporal resolution. Electron temperature and plasma flow velocity can be obtained routinely from IAW spectra, but the width of the IAW peaks depends on both ion temperature, $T_i$, and on fluid velocity distributions within the scattering volume. In some cases, electron temperature ($T_e$) and density ($n_e$) can be obtained from the high-frequency electron plasma wave spectral feature (EPW). The width of the EPW depends on $T_e$, but is also affected by fluctuations in $n_e$. By comparing the values of $T_e$ derived from both scattering features, it may be possible to detect the presence of small-scale, local density variations in the plasma. Past experiments show that including a spatial velocity distribution when fitting the IAW improves the fit quality for a range of times before stagnation; with density fluctuations included in the analysis, the presence of non-thermal, small scale hydromotion in the scattering volume may be indicated.