Investigation of the hydromotion and ion and electron temperatures of stagnating Z-pinch plasma using time- and space-resolved K-line spectra

Summary form only given. Even though the physics of Z-pinch systems is understood in general, there is a severe lack of detailed experimental data on the thermalization processes and dynamics that govern the pinch behaviour, and on the plasma parameters during the stagnation phase. Here, we report on a novel spectroscopic system, used to determine temporally-resolved ion kinetic energy and temperature, electron temperature and density, and spatial correlation between different charge-states species of the stagnating plasma. We use a neon Z-pinch, imploding under a 500-kA, 500-ns current pulse, and observe a hot-and-dense plasma core stagnating on axis for ~10 ns, emitting ~1 kJ of radiation. A two-spectrometer diagnostic system is employed, simultaneously recording two groups of optically-thin lines: He-like satellites to Lyα and high-n H-like Lyδ and Lyε lines, with ultra-high spectral, temporal and spatial resolutions. All data are axially imaged across the stagnation column. The ion temperature is obtained simultaneously from the Stark broadening of hydrogenic-line emission and from the Doppler broadening measurements coupled with energy-balance considerations, and is found to be substantially lower than the hydrodynamic-motion energy. Furthermore, the two-spectrometer system provides a unique insight into the temporal and spatial correlations between the intensities of the spectral lines emitted by different ionic charge-states in the stagnating plasma. Together with kinetics modeling and argumentation, these measurements allow for inferring space-and time-resolved electron density and temperature. This also includes determining the gradients of the electron temperature, and the mechanism of populating the doubly-excited states, along the pinch column.