Electron density and ionization dynamics in an imploding <i>z</i>-pinch plasma

Abstract

The time-dependent radial distributions of the electron and ion densities during the implosion phase of a gas-puff z-pinch plasma are determined from measurements of continuum radiation, as well as time-dependent collisional-radiative analysis of the observed particle ionization history in the plasma. It is shown that during the 140-ns-long time interval close to the end of the ∼620-ns-long implosion phase, the total imploding-plasma mass increases by ∼65%, found to be consistent with the continuous ionization of the gas ahead of the plasma shell. Furthermore, the densities obtained, together with the previously determined radial distributions of the electron temperature, magnetic field, and particle radial velocities, are used to analyze the energy terms that support the radial propagation of the ionization wave seen in the plasma, thereby explaining the time-dependent radial distribution of the ion charge states in the plasma.