Landmark fusion breakthrough achieved by scientists for a second time

Watch: US scientists repeat nuclear fusion breakthrough

A landmark 2022 breakthrough that could lead to a method of curbing climate change has been repeated for a second time.

The National Ignition Facility at Lawrence Livermore National Laboratory has twice achieved net energy gain – where more energy comes out than is put in – in a nuclear fusion reaction firing immensely powerful lasers at a small pellet of hydrogen.

The California-based lab repeated the feat on 30 July, with a higher energy yield than when it first did so in December.

Every nuclear reactor currently operating on Earth is a fission reactor, using energy released when heavy atoms such as uranium decay into smaller atoms, a process similar to the one used in the first nuclear weapons.

A fusion reactor works in the opposite way, harvesting the energy released when two smaller atoms join together.

Lawrence Livermore National Laboratory scientists focused a laser on a target of fuel to fuse two light atoms into a denser one, releasing the energy.

That experiment briefly achieved what's known as fusion ignition by generating 3.15 megajoules of energy output after the laser delivered 2.05 megajoules to the target, the US Energy Department said.

In other words, it produced more energy from fusion than the laser energy used to drive it.

Read more: Scientists hail nuclear fusion breakthrough but caution climate change remains a crisis

The US Energy Department called it "a major scientific breakthrough decades in the making that will pave the way for advancements in national defence and the future of clean power".

Scientists have known for about a century that fusion powers the sun and have pursued developing fusion on Earth for decades.

Such a breakthrough could one day help curb climate change if companies can scale up the technology to a commercial level in the coming decades.