Investigation of the dynamics of stagnating high-energy-density plasma using a novel technique for the determination of the ion temperature

Summary form only given: The thermalization and energy conversion to radiation in high-energy-density plasma is a topic of broad interest in laboratory plasmas and in astrophysics. Knowledge of the ion temperature is of decisive importance, since this parameter determines the rate of various processes, including that of the energy transfer to electrons. We here report on the development of a novel spectroscopic method for determining the ion temperature in the stagnating plasma, based on the Stark broadening of hydrogenic-line emission from moderately-coupled ions in the stagnating plasma. We use a neon Z-pinch, imploding under a 500-kA, 500-ns current pulse. Two spectroscopic systems with ultra-high-resolutions in spectrum, space, and time are employed simultaneously. A major emphasis has been put on measurements of the spectra of two different optically-thin lines: satellites to Lyα and Lyδ. While the optical thinness is invaluable in diagnosing the ion velocity distribution, the electron density, and the ion temperature, the low-intensity of such lines required the use of toroidal crystals, for enhancing the light-collection efficiency. All data were axially imaged across the stagnation column. We demonstrate the first employment of the spectroscopic method, which yields an ion temperature that is compared to previous measurements that were based on Doppler broadening and energy-balance considerations^1,2. In addition, the data allowed for observing temporal and spatial correlations between the shapes of the various lines that are used to infer details of the distributions of the electron density and temperature in the stagnating column.