Evolution of fusion ignition burn through ultrafast reaction history measurements*

The NIF is now routinely making multi-MJ fusion yields, creating a burning, igniting plasma. With advanced diagnostic technology, the time evolution of the fusion can be measured at extreme time resolution (10 ps). With novel reaction history measurements, the transition between an igniting and non-igniting plasma has stark differences in the fusion evolution. The measurements are starting to be used to infer the fusion deposition rate, the explosion rate, and used with other measurements to estimate the hot spot trajectory through temperature and fuel areal density. These measurements can help inform the hot spot formation conditions which ultimately determine the capsule performance. The new measurements offer a novel window into the evolution of an igniting, burning plasma.