SCIENTISTS are to use the world’s most powerful laser system to replicate the fiery core of the sun in experiments that may ultimately offer humanity a clean source of energy.

After more than 50 years of experimentation, physicists are hoping to develop the first form of nuclear fusion technology that produces more energy than it consumes.

Within the next fortnight, researchers at the National Ignition Facility (NIF) in California will fire 192 separate laser beams capable of generating 500 trillion watts - 1,000 times the power of the US national grid - for a fraction of a second.

The energy pulse will be concentrated on a tiny pellet of hydrogen in an attempt to mimic the reactions that take place inside the sun.

The scientists hope to refine the process over the next year until they trigger a nuclear reaction capable of producing large amounts of energy.

“We hope the ignition experiments will show that we can generate more power than we put in and that fusion can be the source of a supply of carbon-free energy,” said Ed Moses, director of the NIF.

“I think the old joke about fusion being just 50 years away, no matter when you ask, is about to become defunct.

“If we succeed, public perception of fusion will change because it is the ultimate energy source - no carbon, limitless, safe and secure.”

NIF was built to test designs for thermonuclear weapons. However, its research will also show how fusion might be used as a peaceful source of energy.

It is among a handful of international projects focused on delivering nuclear fusion.

In France, work has begun on building the £8 billion Iter fusion project, which uses magnetic fields rather than lasers to create the conditions for fusion. However, Iter’s first “burn”, or reaction, is not expected until 2022.

A British-led fusion project, the high power laser programme (HiPER), is expected to build a reactor at the Rutherford Appleton Laboratory (RAL) in Oxfordshire by 2020.

The fusion process mimics reactions that take place inside the sun. Unlike nuclear fission reactions - in which atoms are split apart - the fusion process squeezes atoms together under enormous pressures and temperatures until they fuse, releasing huge quantities of energy.

“It’s long been said by scientists that fusion is just around the corner,” said John Collier, head of the HiPER project. “But if the NIF gets it right, I think we’ve overcome the critical hurdle by showing that we can gain more energy than we put into the reaction.”

The next step would be to create a reactor capable of producing a steady stream of energy.

“The limitation with NIF is you can only fire it around once a month,” said Collier. “HiPER is designed to look at the next step - designing a prototype to show this technology can be commercially viable.”

Even if scientists are able to tame fusion reactions, most experts believe we would still be at least 25 years away from being able to build fusion power stations that could provide a clean alternative to fossil fuels.

Such power stations would use hydrogen atoms extracted from sea water as fuel to generate carbon-free electricity with minimal radioactive waste.

Last week leading scientists issued a plea to politicians to take action on climate change now or face decades of war and social unrest and a planet that becomes unrecognisable.

Mike Dunne, a director at RAL, believes the time has come to invest in nuclear fusion. “If the NIF succeeds, as we expect it to, I fully expect a dramatic public and political response,” he said.

“But to fully take advantage of its success, politicians must start investing in fusion now.

“We probably need around £10 billion internationally. That’s obviously a large sum but, to put it into context, the global energy market is worth around £1.4 trillion annually.”

However, the NIF experiment is not without controversy. The Californian facility’s primary purpose is to allow munitions to be tested without a radioactive fallout, which would contravene the nuclear test ban treaty.

Critics fear the US military is using the NIF complex to develop a new generation of advanced nuclear weapons, although a spokesman for the facility denied this.

Additional reporting: Helen Brooks

Fusion race

Research centres around the world are racing to harness nuclear fusion as a clean power source. They include: National Ignition Facility (California, US) Joint European Torus (Oxford, UK) Iter (Cadarache, France) HiPER (Oxfordshire)

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