Wednesday, 23 July 2014
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System may herald nuclear fusion power generation

UK researchers are developing a high-intensity laser system that could bring nuclear fusion power generation a step closer.

The technology, which aims to increase laser pulse intensity by up to 300 times, could also produce intense X-rays for seeing through dense materials that would otherwise be impenetrable to the radiation.

A team of scientists led by the Science and Technology Facilities Council (STFC) Central Laser Facility (CFL) have used computer simulations to demonstrate the feasability of the technique called Raman amplification, where laser pulses are intensified in ionised hydrogen plasma.

The researchers claim the breakthrough, detailed in a paper in the journal Nature Physics, could allow expensive and complex laser equipment to be replaced with smaller and more cost-effective systems.

‘We’re looking to be able to produce laser pulses with the right intensities to compress pellets of fusion fuel,’ Bob Bingham of the CFL and Strathclyde University told The Engineer.

The shortness of the laser pulses could also be used to create a stroboscopic effect that would allow scientists to study the fast-moving fuel pellets in a laser fusion reactor.

To produce the intense beam, two laser pulses will be fired into the plasma, with one pulse up to 1,000 times longer than the other. Using this system, the team were able to simulate using a four-terawatt pulse to create a two-petawatt pulse.

‘The long pulse contains a lot of energy and its intensity is not that high,’ said Bingham. ‘The short pulse doesn’t contain a lot of energy initially but gains the energy from the long pulse. We get about 60 per cent or more energy conversion, which is incredible.’

The experiment has previously been performed at lower intensities but the CFL researchers have been able to use computers to calculate the correct conditions that would prevent the pulse from being destroyed before it was amplified to a higher intensity.

Using a plasma-based laser system rather than a glass one would allow the researchers to create much more intense pulses, said Bingham. ‘If you fire a high-intensity laser through glass it will explode, but plasma can tolerate a much higher intensity – up to 100,000 times more.’

Bingham expects the technique to be ready to use within a year. Other potential uses of the laser include studying the formation and reactions of biological molecules, and etching silicon wafers at the nanoscale with ion beams.

The team included researchers from St Andrews, Lancaster and Strathclyde universities, Imperial College London and the Portuguese Instituto Superior Tecnico.

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