Scientists in the UK and the Netherlands have made significant strides in tackling two critical challenges in fusion energy research: managing the intense heat within reactors and controlling fuel density in the core. These advancements, achieved through experiments on the MAST Upgrade reactor in the UK and at the Dutch research institute DIFFER, bring us closer to realising the potential of fusion as a clean, limitless energy source.
The first challenge involves distributing the immense power generated by a nuclear fusion reactor more evenly across the vessel wall. Researchers have explored a configuration known as “double-null,” which involves installing an additional divertor at the top of the machine. This setup directs most of the power to the outer divertors, protecting the more vulnerable inner targets. However, maintaining balanced power-sharing between the divertors is a complex task. Experiments on MAST Upgrade, conducted in collaboration with DIFFER, revealed that even minor misalignments in the reactor’s magnetic fields can instantly shift where the heat and particles go. This finding underscores the need for extremely precise control systems in future reactors, such as the UK’s STEP and the international ITER project.
The second challenge revolves around controlling the core density of the reactor, which directly impacts the production of fusion power. Researchers developed a core density controller for MAST Upgrade that uses a gas valve to inject fuel and a laser interferometer to measure the core plasma density. This system has significantly improved the success rate of experiments, contributing to roughly 20% more successful outcomes. Additionally, the team developed a predictive controller that can handle the complexities of pellet injection, ensuring that plasma edge density limits are not exceeded. This controller was tested using high-fidelity simulations of ITER plasma operation, demonstrating its effectiveness in managing core density control.
These advancements are crucial for the development of future fusion power plants. The UK’s STEP programme, in particular, stands to benefit from these innovations. The project, which began in February 2022, focuses on further developing exhaust control and particle control. The work on MAST Upgrade and DIFFER has laid the groundwork for more robust and efficient control strategies, paving the way for the successful implementation of fusion energy.
As fusion research continues to progress, these findings highlight the importance of precise control systems and innovative solutions to the challenges of managing heat and fuel density. The insights gained from these experiments will be instrumental in shaping the future of fusion energy, bringing us closer to a sustainable and limitless power source.