Tokamak Energy builds super magnets for fusion plant testing

Creating sustainable fusion energy requires strong magnetic fields to confine and control the extremely hot, positively charged hydrogen fuel, which becomes a plasma several times hotter than the sun.

The details: According to Tokamak Energy, its new Demo4 facility will consist of 44 individual magnetic coils recently manufactured using 38 km of HTS tape, which carries currents with zero electrical resistance and requires five times less cooling power than traditional superconducting materials.

Demo4 will have a magnetic field strength of more than 18 tesla, nearly 1 million times stronger than the Earth’s magnetic field.

The testing: Demo4 will comprise 14 toroidal field limbs and a pair of poloidal field coil stacks to form a cage-shaped structure. It will need be tested at an extremely low temperature of −253°C–just 20 degrees above absolute zero.

Strong magnetic fields are generated by passing large electrical currents through arrays of electromagnetic coils that will surround the plasma in future power plants. The magnets are wound with precision from the HTS tapes, which are multilayered conductors made mostly of strong and conductive metals, but with an internal coating of rare earth barium copper oxide (REBCO) superconducting material.

The tapes are typically 12 mm wide and less than 0.1 mm thick, containing just a “human hair” of REBCO deposited as a thin coating, according to Tokamak Energy.

Full assembly at Tokamak Energy’s headquarters in Milton Park, near Oxford, U.K., will be completed this year. Testing will extend into 2024, informing designs and operational scenarios for the company’s advanced prototype, ST80-HTS, and the subsequent fusion power plant, ST-E1.

They said it: Chris Kelsall, Tokamak Energy chief executive officer, said, “Tokamak Energy has been a pioneer in recognizing the opportunity to apply and develop high-temperature superconducting technology for fusion energy. The learnings from Demo4 will be a key catalyst for delivering the global deployment of compact, low-cost spherical tokamak power plants. We are proud to be delivering this world-first, complete system of HTS magnetic coils, which will now be assembled into a full tokamak configuration for testing.”

Rod Bateman, HTS magnet development manager at Tokamak Energy, added, “This is a huge, visible moment that we’re really excited about. Our magnets enable the construction and operations of spherical tokamaks, and so are a game changer for getting clean, limitless fusion energy on the grid faster. Demo4 will allow us to create substantial magnetic forces and test them in fusion power plant–relevant scenarios. Importantly, it will substantially progress the technology readiness level of HTS magnets as a key part of our mission to demonstrate grid-ready fusion in the early 2030s.”