A multi-mass-point model for drive asymmetry of double-shell capsules

Drive asymmetry is one of the main sources that degrade the implosion performance of double-shell capsules in inertial confinement fusion. In this paper a multi-mass-point theoretical model under the time-invariant radiation source is proposed to investigate the transfer of drive asymmetry in double-shell capsules and its impact on the fusion performance. In this model, the capsule is divided into independent azimuthal slices by ignoring the azimuthal motion and then assembled to investigate the effect of drive asymmetry. Each slice is described by different models according to the characteristics of different stages. The theoretical predictions exhibit good agreement with the results from radiation hydrodynamic code MULTI. It is found that the radiation asymmetry generates the asymmetry of the ablated mass and velocity in the outer shell during ablation. Then, the outer shell asymmetry is transferred to the inner shell through the acceleration process due to the shell collision. This method can calculate how drive asymmetry develops, propagates, and affects fusion yield during the implosion process of double-shell capsules, while simultaneously providing scaling laws for the relationship between capsule parameters and the transfer of drive asymmetry.