Stitched-pulse, focal-zooming laser drive on the Bosque polar-direct-drive implosion campaign at the NIF*

The LANL Bosque campaign is a Polar Direct-Drive (PDD) implosion campaign looking to study the effects of incomplete mix and thermalization of fusion reactants in Inertial Confinement Fusion (ICF) systems. In these experiments, the targets are capsules of thin spherical plastic shells with interior 3D-printed, two-photon-polymerization (2PP) plastic lattices. We use a novel approach to study mix by exploring how DT fusion yield changes when the deuterium is contained within a deuterated plastic lattice. As part of this campaign we have explored different laser pulses to implode these capsules. One method uses all 192 beams in a long laser pulse which includes a low-energy foot, a linear ramp, and then a flat top at peak energy. The second method uses a stitched-pulse, focal zooming drive with 96 beams per pulse. The first stitch recreates the initial 7 ns from the single-pulse drive. The second pulse is a variable length square pulse with reduced defocus to increase laser coupling on the in-flight capsule surface. The second pulse is also able to continue the laser drive until bang time, unlike the single-pulse drive. Initial results suggest that the stitched-pulse drive increases the yield. We present the design considerations, data, and initial analysis of these experiments.