A novel approach to nuclear fusion. First a laser strips electrons then a second accelerates a proton beam. This achieves 10x higher fusion output than using the laser directly and thousands of times better output than hitting a solid target with a laser.
Physicists have now produced fusion at an accelerated rate in the laboratory without generating harmful neutrons. A team led by Christine Labaune, research director of the CNRS Laboratory for the Use of Intense Lasers at the Ecole Polytechnique in Palaiseau, France, used a two-laser system to fuse protons and boron-11 nuclei. One laser created a short-lived plasma, or highly ionized gas of boron nuclei, by heating boron atoms; the other laser generated a beam of protons that smashed into the boron nuclei, releasing slow-moving helium particles but no neutrons.
The lasers that Labaune’s teams used to generate fusion do so in brief spurts separated by up to 90 minutes. But the same experiment could be repeated with faster lasers that would generate fusion reactions continuously, says laser physicist Gérard Mourou at the Ecole Polytechnique, who was not involved in the research.
The study was not designed to attain fusion’s holy grail — ignition, the break-even point at which the energy generated by the fusion process equals that of the input energy required to power the lasers. But leaps in the power and miniaturization of lasers and the simplicity of the two-laser system “makes this scheme practical” as a future power source.
Timing was crucial for the success of the experiment, says study co-author Johann Rafelski, a theoretical physicist at the University of Arizona in Tucson. The boron plasma generated by the laser lasts only about one-billionth of a second, and so the pulse of protons, which lasts one-trillionth of a second, must be precisely synchronized to slam into the boron target. The proton beam is preceded by a beam of electrons, generated by the same laser, that pushes away electrons in the boron plasma, allowing the protons more of a chance to collide with the boron nuclei and initiate fusion.
NBC News – The new experiment coaxed a boron atom to fuse with a hydrogen nucleus, using a little help from incredibly powerful laser and proton beams. The fusion produced alpha particles, which are more easily converted to usable energy than the high-energy neutrons produced by prior fusion methods.