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Nuclear fusion breakthrough: Germany's reactor sets a new record after running for 43 seconds - taking the world closer towards limitless clean energy
In the core of the sun, a fiery reaction known as nuclear fusion is taking place 24/7.
The process involves two light atomic nuclei combining to form a single heavier one while releasing massive amounts of energy.
If we can replicate nuclear fusion on Earth for long enough, we may be able to unlock clean, affordable energy for people's homes.
Now, scientists in Germany have taken a giant step closer towards making this a reality.
Using the Wendelstein 7-X nuclear fusion reactor in the city of Greifswald, they've set a new world record for a crucial metric in fusion physics.
The record marks the highest performing sustained fusion experiment that ran longer than 30 seconds – with fusion lasting for an impressive 43 seconds.
Wendelstein 7-X is part of a worldwide effort to harness nuclear fusion, which could replace fossil fuels and conventional nuclear fission reactors.
The pretzel-shaped machine, which has a diameter of 50 feet and a height of 16ft, uses an extremely low-density and electrically charged hydrogen gas as fuel.
The €1.6 billion (£1.3 billion) Wendelstein 7-X device, which began operations in December 2015, was built to 'recreate conditions inside stars'.
Officially, it is a 'stellarator' – a type of fusion device that confine hot, charged gas, otherwise known as plasma, that fuels fusion reactions in twisty magnetic fields.
Plasmas must meet three conditions for nuclear fusion to occur – reaching sufficient temperature, density and confinement time.
Together, these factors comprise what is known as the 'triple product', described as a crucial metric of nuclear fusion physics.
A higher triple product indicates greater fusion power and better potential for a successful, self-sustaining fusion reaction.
According to the researchers, the Wendelstein 7-X stellarator managed to achieve a new world record for the triple product.
On May 22, the final day of its latest research campaign, plasma inside Wendelstein 7-X was raised to over 20 million °C, reaching a peak of 30 million °C.
In the record-breaking experiment, the machine sustained a high-performance plasma for 43 seconds.
The device is the world's biggest of its kind and is paving the way for operational nuclear fusion technology, which, if successful, would revolutionize electricity production. Nuclear fusion fuses hydrogen nuclei to form helium, which generates energy from a nearly endless supply of hydrogen on the Earth
What is the triple product?
The triple product - also known as the Lawson criterion - is the key metric for success on the path to a fusion power plant.
Only when a certain threshold is exceeded can a plasma produce more fusion power than the heating power invested.
This marks the point where the energy balance becomes positive, and the fusion reaction can sustain itself without continued external heating.
The triple product is derived from three factors:
- the particle density of the plasma
- its temperature (more precisely the temperature of the ions between which fusion reactions take place)
- energy confinement time - the time it takes for the thermal energy to escape from the plasma if no additional heat is supplied.
The new record beats previously set values by the Japanese Tokamak JT60U (decommissioned in 2008) and the European Tokamak facility JET in Britain (decommissioned in 2023).
Both of these devices were the more widely-used tokamaks, which are slightly different fusion machines from stellarators. Stellarators have the same doughnut shape as a tokamak but use a complicated system of magnetic coils instead of a current to achieve the same result.
Tokamaks are much better studied due to their simpler design compared with stellarators, which are far harder to build, but easier to operate.
Novimir Pablant, the division head for stellarator experiments at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL), said passing the 30-second mark is a key milestone.
If a stellarator can reach this record for 30 seconds, there's no reason these plasma conditions couldn't be sustained for weeks, months or even years because 30 seconds is long enough for the scientists to see the relevant physics at work.
'This experiment ran long enough that nothing is changing any longer in terms of the plasma or experiment conditions,' Pablant said.
In the experiments, a key role was played by a new pellet injector, developed at Oak Ridge National Laboratory in Tennessee. which injects a steady supply of frozen hydrogen pellets into the plasma, enabling long plasma durations through continuous refueling.
During the experiment, about 90 frozen hydrogen pellets, each about a millimeter in size, were injected over 43 seconds, while powerful microwaves simultaneously heated the plasma.
W7-X demonstrates that stellarators can achieve the outstanding properties predicted by nuclear fusion theory, the Max Planck Institute for Plasma Physics (IPP) said in a statement.
There are already nuclear power plants around the world, but they use nuclear fission, which has the disadvantage of generating unstable nuclei, some of which are radioactive for millions of years.
Fusion, on the other hand, does not create any long-lived radioactive nuclear waste but instead helium, which is an inert gas.
Fusion fuel is made up of deuterium and tritium, which are isotopes of hydrogen, the most abundant element in the universe, giving scientists hopes of 'unlimited energy'.
Thomas Klinger, head of operations at Wendelstein 7-X, said the new record is a 'tremendous achievement' by the international team.
'Elevating the triple product to tokamak levels during long plasma pulses marks another important milestone on the way toward a power-plant-capable stellarator,' he said.
WHAT IS A STELLARATOR REACTOR AND HOW DOES IT DIFFER FROM A TOKAMAK?
Stellarators are a type of nuclear fusion reactor and are less widely used than tokamak reactors.
Instead of trying to control plasma with just a 2D magnetic field, which is the approach used by the more common tokamak reactors, the stellerator works by generating twisted, 3D magnetic fields.
Stellarators confine the hot, charged gas, otherwise known as plasma, that fuels fusion reactions in these twisty magnetic fields.
In contrast, tokamaks use a strong electric current to trap plasma inside a doughnut-shaped device long enough for fusion to take place.
The tokamak was conceived by Soviet physicists in the 1950s and is considered fairly easy to build, but extremely difficult to operate.
The twisty configuration of stellarators enables them to control the plasma with no need for the current that tokamaks must induce in the gas.
