MAST (Mega Amp Spherical Tokamak) is the UK's fusion energy experiment, based at Culham Centre for Fusion Energy. Along with NSTX-U – a complementary experiment at Princeton in the USA – MAST is one of the world's two leading spherical tokamaks (STs).

The MAST tokamakExperiments on MAST are important because they test ITER physics in new regimes and they help determine the long-term potential of the ST, which may eventually be suitable as the basis for a power station. A design based on MAST may lead to a compact Component Test Facility, which would reduce risk and accelerate the development of commercial fusion power.

Many experiments on MAST are carried out as collaborations with UK universities, other Euratom Associations and with non-European fusion laboratories. Several are joint experiments with other tokamaks usually under the auspices of International Tokamak Physics Activities expert groups.

MAST plasmaOver 30,000 man-made ‘stars' have now been created by experiments inside MAST. They have provided a wealth of data, enabling many advances in key research areas including plasma instabilities and start-up methods. This is assisted by MAST's impressive suite of diagnostics for analysing plasmas, which is among the best of any tokamak now operating.

To take STs to the next level, more powerful and flexible machines will be needed. With this in mind, Culham Centre for Fusion Energy is implementing a major upgrade that will give MAST unique capabilities. Main features of the upgrade include:

  • An increase in the pulse length by a factor approaching ten;
  • More heating power;
  • Better control and pumping necessary to contain the resulting higher temperature, longer-pulse plasmas;
  • Capability to test advanced 'divertor' solutions to handle high exhaust powers from the plasma.

This will allow scientists to study plasmas which approach ‘steady-state' conditions – operating regimes that could be used for the design of future fusion machines, which must run for hours or days rather than the seconds of today's devices.

MAST parameters (before Upgrade)

1,300,000 amps
Core temperature
up to 23,000,000°C
Pulse length
up to 1 second
Plasma volume
1020 particles/m³
approximately 3m

Vacuum vessel
Stainless steel 304LN
Toroidal field
24 turns, 0.6 tesla @ 0.7m radius
Total mass of load assembly
70 tonnes
Neutral beam heating power
5,000,000 watts @ 75,000 volts