In the heart of Oxfordshire, the Joint European Torus (JET) has been pushing the boundaries of nuclear fusion, and recent experiments have yielded promising results that could revolutionize the energy sector. A team of scientists, led by M. Lennholm, has demonstrated a novel method for controlling the fusion burn rate in a deuterium-tritium (D-T) plasma, a significant step towards practical fusion power.
The JET facility is unique in its ability to operate with tritium, a rare and radioactive isotope of hydrogen. In experiments conducted during the third JET D-T campaign in 2023, the team successfully controlled the ratio of deuterium to tritium in the plasma, thereby regulating the fusion burn rate. This is a crucial development, as controlling the burn rate is essential for the safe and efficient operation of future fusion power plants.
The team measured the D:T ratio using visible spectroscopy and injected tritium via gas valves, while deuterium was injected either via gas valves or pellets. They found that the fusion power, measured via the neutron rate, responded promptly to variations in the D:T ratio. This indicates that, even though the plasma is fueled mainly at the edge, rapid mixing of the isotopes occurs throughout the plasma.
Lennholm explained, “This demonstrates that controlling the D:T ratio is an effective way of controlling the burn rate. It’s a significant step towards making fusion power a viable option for the energy sector.”
However, sustaining a stable plasma is not just about controlling the burn rate. The team also had to manage the edge localized modes (ELMs), which are instabilities that can damage the reactor walls. They found that both the total fueling rate and the D:T ratio influence the ELM frequency, with higher rates and ratios resulting in more frequent ELMs. To address this, they combined the D:T ratio controller with an ELM frequency controller in a multi-input multi-output controller. This allowed for successful simultaneous decoupled control of the D:T ratio and ELM frequency, using a combination of pellet and gas fueling.
This is the first demonstration of such an advanced burn control scheme in a D-T plasma, and it opens up exciting possibilities for the future of fusion power. By precisely controlling the burn rate and ELM frequency, future fusion reactors could operate more efficiently and safely, reducing the risk of damage to the reactor walls and improving the overall lifespan of the reactor.
The implications for the energy sector are significant. Fusion power has the potential to provide a virtually limitless source of clean energy, with no greenhouse gas emissions and minimal radioactive waste. However, achieving this goal requires overcoming significant technical challenges, and the work at JET is a major step in that direction.
The research was published in PRX Energy, a journal that translates to ‘Physical Review X Energy’ in English. It is a testament to the ongoing efforts of scientists around the world to harness the power of the stars and bring fusion power to Earth. As Lennholm put it, “We’re not there yet, but we’re getting closer. And that’s an exciting place to be.”
The success of these experiments at JET could pave the way for future developments in fusion technology. Other tokamaks, such as ITER in France, could benefit from these findings, potentially accelerating the timeline for commercial fusion power. Moreover, the multi-input multi-output control scheme demonstrated at JET could be adapted for use in other types of fusion reactors, further broadening its impact.
As the world seeks to transition to clean, sustainable energy sources, fusion power offers a promising solution. The work at JET brings us one step closer to that future, and it’s an exciting time for the energy sector. The fusion community is buzzing with anticipation, and the results from JET are a significant contribution to the ongoing global effort to make fusion power a reality.
