Dependence of Hot-Spot Mix in DT Cryogenic Implosions on the Design Adiabat

The measured dependence of hot-spot mix[1] on the design adiabat (a = Pshell/PFermi) for laser direct drive (LDD) implosions of DT cryogenic targets on the 60-beam, 30-kJ, 351-nm OMEGA laser is presented. The adiabat of the implosion was controlled by adjusting the temporal shape of the laser drive pulse. Perturbations seeded by debris, target imperfections, engineering features, such as the stalk or fill tube, and laser imprint are amplified by the Richtmyer–Meshkov instability during the shock transit of the shell and by the Rayleigh–Taylor instability of the ablation front during the acceleration phase.[2] The mixing of Ge-doped plastic ablator material with the interior DT fuel was diagnosed with x-ray spectroscopy at stagnation.¹

[1] S. P. Regan et al., Phys. Rev. Lett. 111, 045001 (2013).

[2] I. V. Igumenshchev et al., Phys. Plasmas 20, 082703 (2013).