Early-Time Symmetry Quantifying With Thin-Shell Capsule Radiography For Pulse Shaped Implosion

To achieve ignition with high gain in inertial confinement fusion, precise symmetry control is one of the key issues to guarantee the PdV work converting into the inner energy efficiently and maximize the pressure of the hot spot. The shaped pulse is used to maintain a low adiabat of the shell. A longer pulse and more compressible shell require more rigorous symmetry control, especially the driven symmetry during the picket pulse and main pulse. A surrogate capsule with high Z materials is usually used for the early-time symmetry tuning. The passive diagnosis of the re-emission spheres gives the time-resolved measurement of the first 2ns, and the precision is mainly affected by the weak signals due to the low radiation temperature of the hohlraum. To compare with the re-emission technique with high Z surrogate capsule, we demonstrated the early-time symmetry tuning for picket pulse by using thin-shell capsule radiography technique. Combined with 1D hydrodynamics simulation and backlit imaging simulation, the driven asymmetry was quantified. A view factor assessment was also carried out by IRAD3D and coincided with the experimental consequences.