Researchers at Lawrence Livermore National Laboratory have made a groundbreaking discovery that could pave the way for the future of fusion energy. By confirming the crucial role of symmetry in pre-ignition fusion experiments, they’ve taken a significant step towards achieving the long-awaited goal of ignition.
The Symmetry Factor
A major goal for researcher working on fusion energy is to achieve the burning plasma state, but this has not been easy. A significant factor that has been holding their progress back is the problem of asymmetry.
The simple physics of the issue is described by the researchers like this: trying to achieve fusion with an asymmetric plasma is akin to a heavy left wing on an airplane. It may seem to you that it will work on the ground, but then comes time for take off and suddenly the imbalance is a big problem.
Published recently in Nature Communications, the new study has offered an empirical degradation factor for mode-2 asymmetry in the burning plasma regime. When added to the other previously identified degradations going into varying radiative mix and mode-1 asymmetry, this accounts for the occurrence of reduced variability in fusion performance observed between the two highest-performing experimental campaigns performed at the NIF.
The Path to Ignition
This discovery is not underestimated. Creating a burning plasma was an ‘important milestone’ for the team, verifying decades of theoretical and experimental research and laying the groundwork for future progress.
Balance is crucial in fusion, and by measuring and correcting the asymmetries in their laser-driven implosions the team has ensured that they will reach conditions needed for ignition, much like making certain that an airplane’s cargo holds are correctly ‘balanced’ before take off.
From a suite of coupled 2D radiation hydrodynamic simulations, the researchers also find that mode-2 asymmetry sensitivity is in agreement with experiments at Omega only when alpha-heating effects are included. By refining their models, they have been able to increase the accuracy of their predictions and at the same time reveal more of what factors are underlining in this pursuit.
These results are a key step in the quest for ignition, which could pave the way to eventual practical fusion energy. The researchers managed to overcome the problem of asymmetry, thereby breaking into new areas within existing research directions in which significant progress has already been made.
Conclusion
Experiments conducted in recent years at the Lawrence Livermore National Laboratory have further driven home the importance of symmetry to pre-ignition fusion. The researchers have made a major achievement in pursuit of fusion energy by quantifying the performance sensitivity to mode-2 asymmetry and including it in their models. The finding is not only a validation of years of theoretical and experimental work but also places the field on a firm foundation for further progress. With a few remaining technological challenges, as scientists work the kinks out and understand the pieces of how to make this happen at a reactor scale, that bright future in which we have limitless clean energy through fusion is starting to become more realistic.
