The original MAST experiment took place at the Culham Centre for Fusion Energy, Oxfordshire, England from December 1999 to September 2013.

[1] A spherical tokamak is shaped more like a cored apple than the conventional, doughnut-shaped toroidal design used by experiments such as ITER.

The extensions off the top and bottom are plasma flowing to the ring divertors, a key feature of modern tokamak designs.

Finally, different scenarios have been successfully tested to decrease the energy flow in the central solenoid vs plasma current, which represents another fundamental point for designing a demo spherical tokamak.

The upgrade, which cost £45M, started in 2013 and was expected to significantly exceed MAST’s heating power, plasma current, magnetic field and pulse length.

[6] The design of the next generation Spherical Tokamak for Energy Production (STEP) began in 2019 with £220 million in government funding.