Scientists Make Nuclear Fusion Breakthrough With Help From World's Biggest Laser

U.S. scientists have used the world's largest laser to take a "critical step" towards self-sustaining nuclear fusion power.

Nuclear fusion power has been hailed as one of the most pressing goals in physics since it would offer an effectively unlimited source of clean energy if scientists can work out how to do it.

The process involves fusing two particles together which releases large amounts of energy. It's the same phenomenon that powers stars, including our own sun. On Earth, scientists are attempting to recreate this process artificially.

The problem is that forcing particles together also requires immense heat and pressure in the first place. Scientists have managed to get the particles to fuse, but they've ended up using more energy to achieve this than the fusion process has given out. In other words, it's an overall energy loss.

One of the steps towards achieving a reaction that provides a net energy gain is creating what's called a burning plasma state, in which the fusion reactions themselves are the primary source of heating.

This week, researchers at the Lawrence Livermore National Laboratory in California say they have cracked this step—and they did it with a massive laser.

The laboratory is home to the National Ignition Facility (NIF), a laser capable of generating temperatures of more than 180 million degrees Fahrenheit—several times hotter than the core of the sun—and pressures more than 100 billion times that which we experience on the Earth's surface.

These extreme conditions are achieved by focusing 192 powerful laser beams onto a target the size of a pencil eraser for a very brief time, temporarily delivering around 500 trillion watts of power. To put that in perspective, many household lightbulbs use around 60 watts.

The laser is so powerful thanks to a vast array of amplifiers that increase the laser's power from 1 billionth of a joule at the beams' origin to millions of joules in a fraction of a second. The beam's journey from source to target chamber is about 1,500 meters long, but takes 5 microseconds to complete.

In the nuclear fusion power tests, scientists directed these laser beams towards a fuel-containing capsule in a special container called a hohlraum. Exposed to such intense energy, the target generates plasma—an electrically charged gas.

Fusion reactions occur in this gas, providing the heat necessary for further fusion to occur. In principle, at least.

"Fusion experiments over decades have produced fusion reactions using large amounts of 'external' heating to get the plasma hot," said Alex Zylstra, a physicist at the lab, in a press release. "Now, for the first time, we have a system where the fusion itself is providing most of the heating."

However, the scientists were still some way off from achieving a net energy gain.

A study outlining the achievement was published in the journal Nature on January 26. It reads: "Obtaining a burning plasma is a critical step towards self-sustaining fusion energy."

The scientists will now aim for even higher levels of fusion performance as the race to produce a viable nuclear fusion reactor continues.

NIF target chamber
A scientist works inside the NIF laser target chamber to precisely align a target. The laser produces temperatures much hotter than the sun's core. LLNL/NIF