Investigation of Visbile Line Emission in Gas PUFF Z-pinches at 1-MA on Cobra*

In high current (>1MA) z-pinches, it is a challenge to use visible spectroscopy because there are not many detectable visible lines in the hot plasmas. We have identified several visible spectral lines in 1 MA 200 ns COBRA z-pinch plasmas. These pairs of visible lines are Ar VIII 5168 and 5181 Å, and C IV 5801 and 5812Å, which have been observed from the imploding plasma shell. The other possible line pair is Ne IX 4650 and 4672 Å. In these experiments, a triple-gas puff z-pinch is imploded with and without an external B_z field. Radially resolved Thomson Scattering is used to measure the imploding plasma density, temperature and velocity and to locate the plasma boundary. Visible light from the plasma is focused onto 20-channel fiber linear optical linear arrays. It views cross over the diameter of the plasma. Emission vs. chord radius is dispersed by a 0.75M imaging spectrometer and the spectra are recorded by gated ICCD cameras. The spatially resolved double line-profiles of Ar VIII, C IV, and/or Ne IX are captured. A de-convolution model for the spectrum is used to deduce the Zeeman, and Doppler shifts in the plasma as well as the rotation velocity due to the external B_z field. Details of the experiments will be presented.