Giant Laser set to trigger Fusion Reaction

The world's largest laser is approaching the long-sought goal of igniting a fusion reaction that produces more energy than the laser delivers.

Lasers are intended to do this by super-heating a fusion fuel pellet until it implodes, heating and compressing its central core to the temperatures and pressures needed for nuclear fusion.

Past experiments have been plagued by irregular implosions that wasted most of the input energy. But now, researchers led by Brian MacGowan of the Lawrence Livermore National Laboratory in California have managed to squeeze targets of material into spheres rather than pancakes or more lopsided shapes, paving the way for future attempts at fusion.

The work was performed at Livermore's 192-laser beam National Ignition Facility (NIF), which began operating in 2009.

The team used targets that did not contain the key ingredients for fusion – two isotopes of hydrogen known as deuterium and tritium. But the symmetrical implosion of the targets suggests that NIF should be able to ignite fusion with laser pulses of 1.2 to 1.3 megajoules – well below its full 1.8-megajoule capacity.

"From everything we can see, we're on the right path here," Jeff Wisoff, a top NIF manager told New Scientist.

Researchers spent last year slowly cranking up the output of the laser, ultimately reaching a total energy of more than 1 megajoules. Now they're pausing to mount new instruments on the 10-centimetre-thick aluminium target chamber and to install giant concrete doors to contain neutrons they expect to produce in future fusion experiments.

In a few months, they will begin testing a series of new targets designed to assess beam interactions and compression. If all goes well, they could try for fusion ignition by the end of the year.