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New record temperature for spherical tokamak




14th March 2022

New record temperature for spherical tokamak

Tokamak Energy, based near Oxford, UK, has demonstrated a world-first with its privately-funded ST40 spherical tokamak. The reactor achieved a plasma temperature of 100 million degrees Celsius, the threshold required for commercial fusion energy.

At nearly seven times hotter than the centre of the Sun, this is by far the highest temperature ever generated within a spherical tokamak and also by any privately-funded tokamak. The ST40 had previously achieved a temperature of 15 million degrees in June 2018. While several government laboratories have reported plasma temperatures above 100 million degrees in conventional tokamaks, this milestone has been achieved in just five years, for a cost of less than £50m ($70m) and in a much more compact fusion device. This provides further proof that spherical tokamaks are a viable route to the delivery of clean, secure, low cost, scalable fusion energy.

With over 25 diagnostic tools in the ST40 and utilising the latest precision measurement technologies, the record high temperature result has been verified by an independent advisory board consisting of international experts. Tokamak Energy plans to share these results with the scientific community.



The ST40 uses a novel technique to generate and heat the plasma – “merging compression”. Normally, start-up is the role of the solenoid. While the ST40 still has a solenoid at its centre, it is used to maintain the plasma current, rather than generate it. Not relying on the solenoid is important in spherical tokamaks as there is only limited space in the core of the machine.

“We are proud to have achieved this breakthrough, which puts us one step closer to providing the world with a new, secure and carbon-free energy source,” said Chris Kelsall, CEO of Tokamak Energy. “When combined with high temperature superconducting (HTS) magnets, spherical tokamaks represent the optimal route to achieving clean and low-cost commercial fusion energy. Our next device will combine these two world leading technologies for the first time and is central to our mission to deliver low-cost energy with compact fusion modules.”

The ST40 will now undergo an upgrade and be used to develop technologies for future devices. The ST-HTS, set to become the world’s first spherical tokamak to demonstrate the full potential of HTS magnets, is due to be commissioned in the mid-2020s. This device will demonstrate multiple advanced technologies and will inform the design of a world-first fusion pilot plant, to be commissioned in the early 2030s.

“Fusion energy could be the ultimate power of the future – low carbon, safe and sustainable – and this is another crucial step towards it. I congratulate all of those who contributed to this important milestone,” said Kwasi Kwarteng, Secretary of State for Business, Energy and Industrial Strategy. “The Government’s fusion strategy, published last year, is designed to support companies like Tokamak Energy to make fusion energy a reality. I look forward to further milestones in the months and years ahead.”



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