SIGNATURES OF TARGET PERFORMANCE AND MIXING IN TITANIUM-DOPED, LASER-DRIVEN TARGET IMPLOSIONS

Absorption spectroscopy measurements using an embedded titanium layer have been performed on laser implosions of spherical shells. Predicted absorption features formed by the titanium layer were observed: absor ption lines due to 1s-2p transitions in titanium ions of incomplete L shell, as well as K-edge absorption in cold titanium. Also observed we re oscillations due to EXAFS (Extended X-Ray Absorption Fine Structure ) above the Ti K edge. The core temperature and shell areal density an d temperature are derived from the measurements and are found to fall short of the values predicted by one-dimensional code simulations. Thi s shortfall is attributed to the lack of irradiation symmetry, which l eads to hydrodynamic instability and mixing (smoothing by phase plates was not used in this experiment). Signatures of mixing include the em ission of the He-alpha line of Ti+20 due to titanium migrating to the core, as well as the EXAFS spectrum indicating cold titanium close to peak compression.