Studies on dynamical shell formation for direct-drive laser fusion

Conventional targets for direct-drive laser fusion consist of a spherical shell with a thin inner layer of frozen deuterium-tritium fuel. Such targets can be effectively imploded at the velocities required for thermonuclear ignition by the ablation pressure generated by collisional absorption of laser light. Recently, a new concept has been proposed using much simpler homogeneous spheres. In this case, the shell is formed dynamically. A first laser pulse produces an imploding shock wave, which after bouncing from the center turns into a blast wave. Interaction of this blast wave with imploding waves driven by subsequent laser pulses eventually generate the shell, ready to be imploded as in the conventional approach. A reduced-scale proof-of-principle experiment on dynamic shell formation is now under design (at Rochester’s LLE OMEGA Laser). We present and discuss relevant numerical hydrodynamic studies performed with Sapienza’s DUED code. We have defined pulse timing and power required for shell formation using 1-D simulations, and studied robustness to deviations from spherical irradiation with 2-D simulations.