A British nuclear fusion reactor has reached temperatures hotter than the centre of the sun in a test that marks a key step toward limitless clean energy.

The Tokomak reactor hit 15 million°C (59 million °F) at a facility in Oxfordshire as part of preparations to supply the UK grid with fusion power by 2030.

Researchers at Tokomak Energy are attempting to build an affordable fusion reactor that turns hydrogen into cost-effective green energy.

With fusion energy, one tablespoon of liquid hydrogen fuel could generate as much energy as 28 tons of coal with no radioactive waste.

The latest test takes Tokomak Energy a step closer to its ultimate goal of heating high-energy gas to 100 million degrees centigrade (212 million °F) later this year.

At this temperature - seven times hotter than the centre of the sun - the reactor will trigger nuclear fusion, a joining together of atomic nuclei that releases enormous amounts of energy.

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A British nuclear fusion reactor has reached temperatures hotter than the centre of the sun in a test that marks a key step toward limitless clean energy. Pictured is the reactor at the Tokomak Enegery facility in Milton, Oxfordshire

This same process powers stars, and Tokamak Energy, based in Milton, Oxfordshire, is working to recreate it in a device called a compact spherical tokamak.

The company aims to produce industrial scale fusion energy by 2025 before its technology is integrated into Britain's power grid.

Tokamak Energy's 15 million°C landmark was achieved in a prototype device dubbed ST40 that was commissioned last year.

ST40 is the third machine in a five-stage plan to achieve abundant, clean fusion energy.

Dr David Kingham, co-founder of Tokamak Energy, said: 'The world needs abundant, controllable, clean energy.

'Our business plan is built on strong scientific foundations and this major milestone provides further validation of our compact spherical tokamak route to fusion power.

The Tokomak reactor heated a gas to 15 million degrees centigrade (59 million °F) at a facility in Oxfordshire as part of preparations to supply the UK grid with fusion power by 2030. This image shows the high-energy gas, known as plasma, inside the ST40 reactor

Researchers at Tokomak Energy are attempting to build an affordable fusion reactor that turns hydrogen into cost-effective green energy. The reactor used in the latest test is called ST40 (pictured), the third machine in a five-stage plan to achieve abundant, clean fusion energy

WHAT IS A TOKAMAK NUCLEAR FUSION REACTOR? The tokamak is the most developed magnetic confinement system and is the basis for the design of many modern fusion reactors. Plasma is contained in a vacuum vessel, which is then heated by driving a current through it. A combination of two sets of magnetic coils creates a field in both vertical and horizontal directions, acting as a magnetic 'cage' to hold and shape the plasma. The heating provided by the plasma current supplies a third of the 100 million°C temperature required to make fusion occur. The tokamak (artist's impression) is the most developed magnetic confinement system and is the basis for the design of many modern fusion reactors Additional plasma heating is provided when neutral hydrogen atoms are injected at high speed into the plasma, ionized and trapped by the magnetic field. As they are slowed down, they transfer their energy to the plasma and heat it. High-frequency currents are also induced in the plasma by external coils. The frequencies are chosen to match regions where the energy absorption is very high. In this way, large amounts of power may be transferred to the plasma. Advertisement

'Fusion is a major challenge, but one that must be tackled.

'We believe that with collaboration, dedication and investment, fusion will be the best means of achieving deep decarbonisation of the global energy supply in the 2030s and beyond.'

Tokamak Energy's 15-million-degree landmark was achieved in a prototype device dubbed ST40 (pictured)

Fusion involves placing hydrogen atoms under high heat and pressure until they fuse into helium atoms.

The same process enables stars to shine and in a less controlled way provides the destructive force of H-bombs.

Fusion power holds out the promise of almost unlimited supplies of clean energy. It uses special forms of hydrogen as fuel, produces no greenhouse gases, and the only waste product is helium.

But harnessing and raining in the mighty forces involved is a daunting challenge.

Tokamak Energy's ST40 achieves its dizzying temperatures using a technique known as merging compression.

This releases energy as rings of super-hot cloud of electrically charged gas called plasma that crash together, forcing the plasma's magnetic fields to reconfigure.

Merging compression involves putting high electric currents through internal coils of the tokamak, which requires power supplies to deliver thousands of amps in a matter of seconds.

With fusion energy, one tablespoon of liquid hydrogen fuel could generate as much energy as 28 tons of coal with no radioactive waste. Pictured is the SV40 reactor

Tokamak Energy grew out of the Culham Centre for Fusion Energy in Oxfordshire.

A key innovation is that the company combines spherical tokamaks with the latest generation of high temperature superconducting magnets (HTS).

Jonathan Carling, CEO at Tokamak Energy, said: 'We are taking significant steps towards achieving fusion energy, doing so with the agility of a private venture, driven by the goal of achieving something that will have huge benefits worldwide.

'Reaching 15 million degrees Celcius is yet another indicator of the progress at Tokamak Energy and a further validation of our approach.

The latest test takes Tokomak Energy a step closer to its ultimate goal of heating high-energy gas to 100 million degrees centigrade (212 million °F) later this year

At 100 million degrees centigrade (212 million °F) - seven times hotter than the centre of the sun - the reactor will trigger nuclear fusion, a joining together of atomic nuclei that releases enormous amounts of energy

'Our aim is to make fusion energy a commercial reality by 2030.'

In 2017, Tokamak Energy was selected by the International Energy Agency (IEA) as one of three leading innovative ideas in fusion.

Tokamak Energy has raised private investment of more than £30 million, with investors including Oxford Instruments, Legal & General Capital and the Institution of Mechanical Engineers.

Tokamak Energy's ST40 (pictured) achieves its dizzying temperatures using a technique known as merging compression. This releases energy as rings of super-hot cloud of electrically charged gas called plasma that crash together