Spectroscopic diagnosis of OMEGA direct-drive low-adiabat implosions*

We discuss the observation and data analysis of K-shell line spectra from argon-doped deuterium-filled OMEGA direct-drive low-adiabat 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 diagnostic of core implosion conditions. The observed spectra includes resonance and satellite 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 appoximately 500. Both optically thick and thin lines are simultaneously modeled, including line overlapping and Stark-broadening effects. The spectroscopic analysis yields the details of temperature and density time-histories in the compressed core.