Determination of the time-dependent radial distributions of the electron density, electron temperature, and ion charge states in a cylindrically imploding plasma

We have recently reported the time-dependent measurements of the particle velocity and magnetic field distributions during the implosion phase of a moderate-density gas-puff Z-pinch plasma. Here we will discuss the results on spectroscopic determination of electron density Ne, electron temperature Te, and charge state distribution under the same conditions. The gas-puff system is used to produce a hollow cylinder of C02 gas in the 1 .35-cm wide anode-cathode gap. A high-voltage discharge circuit produces a plasma pinch in about 600 ns with a peak current of 220 kA. The spectroscopic measurements with a temporal resolution of 10 ns, were carried out by observing the plasma along the z axis at various radio] locations throughout the implosion process, thereby providing a complete mapping in (r, t) of the line emission from plasma. The time-dependent electron density radial distribution was determined from the measured Stark line widths of the different ions of oxygen at different radial positions. The time-dependent intensities of the visible lines from the same or successive charge states were used to obtain the electron temperature. Both the electron density and temperature were determined self-consistently by measuring the ionization times of the various charge-state ions. These results are used together with the collisional-radiative (CR) calculations to determine the time-dependent plasma composition. The CR simulations with the NOMAD code were carried out with account of temporal variations of the electron density and opacity effects