Laser image confirms fusion

17 Jun 2002

An image of an imploding fusion pellet verifies that researchers are closer to creating controlled nuclear fusion.

Fusion Pellet

Researchers at the US Sandia National Laboratories have used a high-energy laser to take images of a pellet approaching fusion whilst under rapid compression. John Porter and colleagues believe that the images prove they are closer to controlling nuclear fusion and unleashing an unlimited energy source.

Known as the Z-beamlet, the pulsed solid-state Nd:Glass laser was built by scientists at Sandia and Lawrence Livermore, US, over three years. Costing more than USD 12 million, the laser takes X-ray images of events, such as simulated fusion, at Sandia's powerful X-ray "Z-facility".

"I believe that this is the third largest laser of its kind," John Porter told optics.org. "The main laser cavity is 30 m long [and produces] a beam that is 32 by 32 cm in size."

Z-Beamlet

To create a pellet image the beam travels 72 m to the Z-facility, where it is focused to a 50 micron spot behind the pellet. The beam emits an intense pulse of X-rays that are absorbed by the pellet to produce a pellet-shaped shadow. Porter and colleagues then capture the shadow on a X-ray film.

"This is the same as taking a dental image," explained Porter. "But the Z-beamlet laser pulse duration is only 300 ps in order to freeze the motion of the pellet."

Porter says this latest image has made the team more optimistic than ever. "We can now see the pellet during implosion and can accurately describe what's happening," he added.