Spectroscopic investigation of the implosion dynamics of a gas-puff Z-pinch plasma

The time dependent properties of the imploding plasma produced in a gas-puff, 1.6 µs, 320 kA Z-pinch device are determined. Line emission of ions up to the sixth ionization stage is observed along various chords and in the axial direction. Measurements of radial ion velocity distributions from Doppler broadening and shifts, and of the radial charge state distribution across the plasma shell demonstrate the existence of an ionization front propagating radially inward with nearly constant velocity of 1·10⁷ cm/s. Line intensity ratios and observed particle ionization times are used to determine the electron temperature. The electron density is obtained from Stark broadening and continuum radiation measurements. These measurements, combined with collisional-radiative calculations, yielded the absolute ion densities. The radial distribution of the magnetic field in the plasma is determined from Zeeman splitting using polarization spectroscopy. This gives the current density and the skin depth, yielding the Ohmic heating as a function of time and radius.