Britain's newest fusion reactor has been fired up, taking the UK one step further towards generating electricity from the power of the stars.
The heart of the Tokamak ST40 reactor in Oxfordshire - a super-hot cloud of electrically charged gas, or plasma - is expected to reach a temperature of 100 million centigrade in 2018.
That is how hot it needs to be to trigger fusion, the joining together of atomic nuclei accompanied by an enormous release of energy.
The same process enables stars to shine and in a less controlled way provides the destructive force of H-bombs.
It is Tokamak Energy's third upgraded reactor and represents the latest step in a five-stage plan to bring fusion power to the national grid by 2030.
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"Today is an important day for fusion energy development in the UK, and the world," Tokamak Energy chief executive Dr David Kingham said after the reactor was officially turned on and achieved "first plasma".
"This will allow fusion power to be achieved in years, not decades."
The plasma, seven times hotter than the centre of the sun, has to be contained in a doughnut-shaped "magnetic bottle".
Tokumak Energy has raised AGBP20 million ($A34.53 million) from private contributors but Kingham says the project is only half way to the goal of fusion energy and still needs "significant investment".
