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Non-nuclear energy

Spherical Tokamaks

Fission and radiation protection

Spherical tokamaks are toroidal plasma confinement devices related to tokamaks.

The plasma shape of spherical tokamaks compared to a conventional tokamak. © Image: UKAEA

The plasma shape of spherical tokamaks compared to a conventional tokamak.
© Image: UKAEA

In a spherical tokamak (ST) the plasma is confined in basically the same way as for the conventional tokamak. The main difference, as the name suggests, is in the magnetic geometry. In an ST device the aspect ratio (the ratio of the device’s width to its height) is low. An ST looks like a sphere with a hole through the middle rather than the doughnut shape of a conventional tokamak. ST research is a relatively young subject, and is therefore much less developed than the conventional tokamak. Nevertheless, it is moving forward rapidly, and there are indications that some of the theoretically predicted advantages may be achievable. For example, it has been shown that an ST may be more efficient than a conventional tokamak in terms of plasma performance for a given engineering cost.

Spherical tokamak configuration © Image: UKAEA

Spherical tokamak configuration
© Image: UKAEA

The Culham laboratory of the UKAEA Fusion Association, has operated two ST devices. Initial experiments with START (Small Tight Aspect Ratio Tokamak) demonstrated a number of attractive features of the ST, which are now being pursued with the Mega Ampere Spherical Tokamak (MAST) device.