Deceleration-Phase Hydrodynamic Instability Growth in Dynamic Shell Inertial Confinement Fusion Designs

A new dynamic shell concept¹ has been recently proposed for inertial confinement fusion implosions that allows for control of the mass density in the central, lower-density region of the dynamically formed target. The central density affects the shell convergence ratio (CR), and consequently, perturbation amplification during the final stages of an implosion. Besides the CR, the Rayleigh–Taylor instability is another critical aspect of deceleration-phase instabilities. It develops on the inner surface of the shell during the deceleration phase where the growth rate is suppressed because of mass ablation driven by thermal conduction in the form of “fire polishing” and the “rocket effect.” With dynamic shell formation, shell convergence at the start of the deceleration phase and the mass ablation rate from the inner part of the shell can both be changed by varying the density of the central region via appropriate laser pulse shaping. Using DEC2D, a 2-D hydrodynamics code, we optimize robustness of a dynamic shell design against perturbation amplification during shell deceleration.