Scientists have fired the world's most powerful laser.

The laser delivered 500 trillion watts of power, and 1.85 megajoules of ultraviolet light - which is more than 1,000 times the power used by the United States at any instant in time.

The historic stream was made up of 192 individual beams when they were fired on 5 July at the Lawrence Livermore National Laboratory's National Ignition Facility.

The combined laser was said to be not only the most powerful ever fired, but also the "most precise and reproducible". A structure more than 10 storeys in height was needed to produce the beam, which was fired at a target just 2mm in diameter.

Eventually the NIF hopes powerful lasers of this type will be used to start nuclear fusion reactors.

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Above: the laser's target, just 2mm across


"NIF is becoming everything scientists planned when it was conceived over two decades ago," NIF Director Edward Moses said.

"It is fully operational, and scientists are taking important steps toward achieving ignition and providing experimental access to user communities for national security, basic science and the quest for clean fusion energy."

When plans for the laser were first drawn up in 1990, the optical technology required to withstand the intense light did not exist.

The researchers had to work with industrial partners to reduce the number of defects in an optical lens before they could safely fire such a powerful beam.