The Impact of the Beam-to-Target Ratio in Direct-Drive DT Cryogenic Implosions on OMEGA*

The performance of laser-direct-drive cryogenic DT inertial confinement fusion implosions depends strongly on the ratio between the radius of the laser beams that illuminate the shell and the target radius (R_b/R_t). The analysis of previous experiments using targets of varying radii at constant beam radius, has shown that laser imprint is most likely the dominant cause of this dependency at moderate illumination intensity (∼5×10¹⁴ W/cm²). To study the effect of target composition on the observed scaling with R_b/R_t, a new series of experiments with targets that contain 5% of Si doping in the outer ∼5 µm of the plastic shell, which contains the DT ice layer. Targets of 780-µm, 870-µm, and 1010-µm diameter were used scanning R_b/R_t from ∼1.09 to ∼0.85. A detailed comparison of the experimental observables from both neutron and x-ray detectors with the theoretical modeling will be presented.