Plasma results from Tokamak Energy’s record-breaking machine advances commercial fusion mission

Tokamak Energy’s record-breaking fusion machine has broken new ground following a series of upgrades.

The company’s ST40 reached a plasma temperature of 100 million degrees Celsius last year, the threshold required for commercial fusion energy and the highest ever achieved in a privately funded spherical tokamak.

Tokamak Energy’s advances during the recent campaign, which ended at the end of September, focused on improving understanding and developing high-performance diverted plasma scenarios in a high field spherical tokamak.

Dr Steven McNamara, Tokamak Energy’s Head of Plasma Systems, alongside other members of the team, will present the full results at next week’s International Atomic Energy Agency (IAEA) Fusion Energy Conference at the Queen Elizabeth II Centre in London.

In a diverted configuration, the magnetically confined hot gas is separated from the wall and its exhaust is directed to a dedicated ‘divertor’ region that extracts heat and particles, keeping the core plasma cleaner and therefore significantly improving overall performance.

In a fusion pilot plant, the heat loads on the divertor are expected to be similar to a space shuttle during re-entry.

An infrared camera was installed in collaboration with Oak Ridge National Laboratory (U.S.) to measure the power load distribution on the divertor targets, helping to improve understanding of plasma exhaust and boost confidence in future power plant designs.

Some of the hardware, including the infrared camera and endoscope, was funded through the UK Government’s Department for Energy Security and Net Zero Advanced Modular Reactor (AMR) Feasibility and Development Phase 2 programme.

Dr McNamara said: “We’re delighted with these latest machine enhancements and results, and proud of how ST40 continues to expand our understanding, further validating future power plant designs on our path to delivering clean, secure and affordable fusion energy in the 2030s.”

To achieve its milestones, Tokamak Energy upgraded the ST40 plasma control system as diverted plasmas are vertically unstable and require precise control. This enabled the team to exceed its target by achieving a diverted plasma with higher currents, sustained for longer durations.

In addition, the team also established diverted H-mode plasmas across a range of parameters and developed scenarios with a high fraction of non-inductive current drive. These scenarios will be used in future operations to further develop key understanding of the performance of high-field spherical tokamaks.

ST40 is a high-field spherical tokamak with copper magnets built and operated by Tokamak Energy. It is a step on the company’s roadmap to develop commercial fusion power plants.

After breaking the 100 million degrees record in 2022, ST40 has been through a series of hardware upgrades to improve its capabilities, including new power supplies and diagnostic systems. It will be back in operation in early 2024 following further upgrades and maintenance.

553 538 Stuart White
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