The role of symmetry in indirect-drive laser fusion

Good radiation drive symmetry will be crucial for achieving ignition in laboratory inertial fusion experiments. The indirect-drive inertial confinement fusion (ICF) method utilizes the soft x-ray field in a radiation-containing cavity, or hohlraum, to help achieve a high degree of symmetry. Achievement of the conditions necessary for ignition and gain will require experimental fine tuning of the drive symmetry. In order to make tuning possible, a significant effort has been devoted to developing symmetry measurement techniques. These techniques have been applied to a series of experiments that give a graphic picture of the symmetry conditions in the complex hohlraum environment. These experiments have been compared with detailed, fully integrated theoretical modeling. The ultimate goal of this work is the detailed understanding of symmetry conditions and the methods for their control. Comparison with experiments provides crucial benchmarking for the modeling---a key element in planning for ignition