Exploring the Hydrodynamic Stability of Dynamic-Shell Formation Designs for Inertial Confinement Fusion*

A dynamic-shell formation (DSF) concept in direct-drive inertial confinement fusion utilizes the conventional central hot-spot–ignition scheme using an easy fabricated spherical pellet of liquid deuterium–tritium [V. N. Goncharov et al., Phys. Rev. Lett. 125, 065001 (2020)]. Since it starts from a pellet and not a shell, this concept employs additional stages of target conditioning. The pellet is initially compressed by convergent shocks, initiated by laser pickets, which results in a bouncing and expansion of the pellet mass from the center. The expanding mass then decelerates and forms a shell with the help of subsequent converged shocks. The shell is finally imploded, producing thermonuclear energy using the main laser pulse, as in the conventional scheme. The target-conditioning stages result in developing hydrodynamic instabilities in addition to those that develop in conventional implosions during the target acceleration and deceleration stages. A numerical study employing 3D radiation-hydrodynamic ASTER simulations have shown that DSF designs are more susceptible to low- and high-mode perturbations because of their additional growth primarily during the bouncing stage. Specifications of required laser-illumination uniformity in well-performing DSF design simulations are discussed.