X-Ray Spectroscopy of Shock-Ignition Implosions

We discuss the observation and spectroscopic analysis of argon K-shell x-ray line spectra from argon-doped deuterium-filled OMEGA direct-drive shock-ignition implosions based on data recorded with streaked crystal spectrometers. The argon line spectrum is primarily emitted at the collapse of the implosion thus providing a spectroscopic signature of the state of the imploded core. The observed spectra includes parent and satellite line transitions in H-, He- and Li-like Ar ions thus covering a broad photon energy range from 3200 eV to 4200 eV with a spectral resolution power of approximately 500. Both optically thick and thin lines are simultaneously modeled, including line overlapping and Stark-broadening effects. The spectroscopic analysis results show core temperature and density time-histories associated with the collapse implosions. A comparison is also made with LILAC hydrodynamic simulations.