Scientists have not yet been able to produce nuclear fusion on a large commercial scale. But two new studies published in Physical Review Letters by scientists at the National Ignition Facility (NIF), which officially opened last year at the Lawrence Livermore National Laboratory in Livermore, California, have produced some promising results.
The scientists are developing inertial confinement fusion (ICF), a type of fusion in which high-energy lasers heat and compress an inch-long gold fuel pellet called a “hohlraum” that contains the hydrogen isotope nuclei to be fused. The goal of ICF reactions is to achieve ignition, where the fusion reactions generate enough heat to be self-sustaining. The scientists hope that the fusion reactions inside the fuel pellets will generate 10-20 times more energy than that provided by the lasers that start the reactions.
In their recent experiments, the scientists at the NIF have achieved two of the most important components of ignition: extremely high “Sun-like” temperatures and uniform compression so that the targets don’t lose their shape. In the current experiments, the scientists used two-millimeter-diameter plastic spheres as the targets instead of hohlraums because they were easier to analyze.
The experiment involved focusing 192 laser beams onto the plastic spheres, each of which contained helium. The lasers generated large amounts of heat energy that was converted to X-rays with nearly 90% efficiency, and produced temperatures of up to 3.6 million degrees Celsius (300 eV). At these temperatures, the diameters of the two-millimeter spheres shrunk to about one-tenth of a millimeter.
While these altitude attending promising, accurate agitation will absorb some altered components. Instead of helium, the ammunition pellets will accommodate the aspect beryllium, which itself will accommodate the hydrogen isotopes deuterium and tritium. The laser-generated X-rays will account the beryllium to explode, bearing a acknowledging entering abortion that sends shockwaves into the hydrogen isotopes. The shockwaves added access the temperature of the deuterium and tritium nuclei to the point area they can affected their alternate abhorrence and fuse.
The accepted abstracts accept apish the altitude for such a acknowledgment to action in a added astute way that any antecedent experiment. However, the advisers plan to booty baby accomplish against the final ambition of ignition. They’re currently testing spheres that accommodate diff quantities of deuterium and tritium in adjustment to investigate the achievability of agee implosions.
Edward Moses, Associate Director of the NIF, hopes that the ability will authenticate absolute agitation in the bounce or summer of 2012. However, he cautions that abstruse and accurate setbacks could baffle with the timeline. For instance, aftermost January, Moses and others at the NIF had hoped to authenticate agitation by the end of 2010.