Competing effects of collisional ionization and radiative cooling in inertially confined plasmas

We describe an experimental investigation, a detailed analysis of the Ar XVII 1s(2 1)S-1s3p P-1 (He beta) line shape formed in a high-energy-density implosion, and report on one-dimensional radiation-hydrodynamics simulation of the implosion. In this experiment trace quantities of argon are doped into a lower-Z gas-filled core of a plastic microsphere. The dopant level is controlled to ensure that the He beta transition is optically thin and easily observable. Then the observed line shape is used to derive electron temperatures (T-e) and electron densities (n(e)). The high-energy density plasma, with T-e approaching 1 keV and n(e) = 10(24) cm(-3), is created by placing the microsphere in a gold cylindrical enclosure, the interior of which is directly irradiated by a high-energy laser; the x rays produced by this laser-gold interaction indirectly implode the microsphere. Central to the interpretation of the hydrodynamics of the implosions is the characterization and understanding of the formation of these plasmas. To develop an understanding of the plasma and its temporal evolution, time-resolved T-e and n(e) measurements are extracted using techniques that are independent of the plasma hydrodynamics. Comparing spectroscopic diagnostics with measurements derived from other diagnostic methods, we find the spectroscopic measurements to be reliable and further we find that the experiment-to-experiment comparison shows that these implosions are reproducible.