New breakthrough gets fusion fuel closer to reality

Scientists at Lawrence Livermore National Laboratory (LLNL) have taken a step to bring fusion fuel closer to reality.

Lead author Omar Hurricane said what's really exciting is that they are seeing a steadily increasing contribution to the yield coming from the boot-strapping process they call alpha-particle self-heating as we push the implosion a little harder each time.

Boot-strapping results when alpha particles, helium nuclei produced in the deuterium-tritium (DT) fusion process, deposit their energy in the DT fuel, rather than escaping. The alpha particles further heat the fuel, increasing the rate of fusion reactions, thus producing more alpha particles.

This feedback process is the mechanism that leads to ignition. As reported in their paper, the boot-strapping process has been demonstrated in a series of experiments in which the fusion yield has been systematically upped by more than a factor of 10 over earlier approaches.

The experimental series was carefully designed to avoid breakup of the plastic shell that surrounds and confines the DT fuel as it is compressed. It was hypothesized that the breakup was the source of degraded fusion yields observed in previous experiments.

By modifying the laser pulse used to compress the fuel, the instability that causes break-up was suppressed. The higher yields that were obtained affirmed the hypothesis, and demonstrated the onset of boot-strapping.

The experimental results have matched computer simulations much better than previous experiments, providing an important benchmark for the models used to predict the behavior of matter under conditions similar to those generated during a nuclear explosion, a primary goal for the NIF.

The study has been published online in the journal Nature.