While scientists have tried to harness fusion as a clean energy source for decades, many technical challenges remain unsolved. One such challenge is providing the massive amounts of energy required to induce a fusion state. Previous efforts have tried using lasers as an indirect drive inside a hohlraum to compress a fuel-filled capsule into a hot and dense state for fusion reactions. However, the energy coupling efficiency from the laser to the capsule has been limited to roughly 10%.
Ping et al. demonstrate experimentally that a 30% coupling efficiency is possible, by tuning the symmetry of Al capsule implosions in Au hohlraums to shape like rugby balls. They found by modifying the hohlraum shape, a good shell symmetry can be achieved.
“The most innovative aspect of this research is that the shape of the hohlraum is changed from cylindrical to ovoid like a rugby,” says author Yuan Ping. “Both simulations and experiments have shown that such a shape change leads to many beneficial effects, including accommodating larger capsules for higher energy coupling, and tunability for symmetry control.”
These results support the idea that higher coupling efficiency and control can be achieved through novel target shapes.
“This experiment is eye-opening to the community that there exist other potential schemes toward fusion ignition besides the mainstream approaches,” said Ping. “The extreme conditions created by this kind of research can simulate certain environments in the universe to help with tests of current models.”
For next steps, the researchers are planning to design a proper capsule and conduct hohlraum-driven single-shell volume ignition experiments.
Source: “Symmetry tuning and high energy coupling for an Al capsule in a Au rugby hohlraum on NIF,” by Y. Ping, V. A. Smalyuk, P. Amendt, S. Khan, R. Tommasini, E. Dewald, J. E. Field, F. Graziani, E. Hartouni, S. Johnson, O. L. Landen, J. Lindl, A. MacPhee, A. Nikroo, R. Nora, S. Prisbrey, J. Ralph, R. Seugling, D. Strozzi, R. E. Tipton, Y. M. Wang, Y. Kim, E. Loomis, K. D. Meaney, E. Merritt, D. Montgomery, N. Kabadi, B. Lahmann, and R. Petrasso, Physics of Plasmas (2020). The article can be accessed at https://doi.org/10.1063/5.0021183.
