This week (Feb 12), scientists at Lawrence Livermore National Laboratory in California reported a significant achievement in the future of energy production here on Earth. In a complex the size of a football stadium they have concentrated the light from 192 lasers into a peppercorn sized pellet lined with fuel, crushing hydrogen atoms together with enough energy to fuse into helium outputting, for the first time, more energy than was put in.
From Forbes: In the National Ignition Facility at Lawrence Livermore National Laboratory, this spherical hohlraum target, about to be blasted by lasers sufficient to ignite a nuclear fusion event, contains a polished capsule about two millimeters in diameter, filled with cryogenic hydrogen fuel – deuterium and tritium super-cooled to 426°F below zero. Source: NIF
Now, before we jump up and down, one of the researchers, Omar Hurricane whose name certainly warrants his position as a nuclear fusion badass, says that though the energy that fused the hydrogen was less than the resulting output, only about one percent of the lasers' energy ever reached the fuel. This means that until we have more efficient ignition, nuclear fusion as a viable energy solution here on Earth persists only in concept.
Still, this gives some light to the probability of harnessing an essentially boundless and clean energy source. Contrary to nuclear fission, performed in modern nuclear power plants capturing the energy from breaking apart heavy uranium atoms leaving unstable and radioactive lighter elements, free neutrons and gamma radiation, the synthesis in fusion has no significant ill effects. In both fusion and fission we're dealing with the two strongest forces in the universe: the Coulomb electric force which repels positively charged protons from each other, and the nuclear strong force which holds those same positively charged protons together at close range. In fusion, if you push protons together, they will exponentially repel more greatly the closer they get... However, there is a energy with which you can push the particles together allowing the close-range attractive nuclear strong force to overtake the repulsive electric force and seal them together with great ferocity. This surmounting attraction from the nuclear force will release all of the potential energy built up from the Coulomb electric force in surplus of the energy put in (when performing this with light elements like hydrogen). Alternatively, in fission (and with heavy atoms like uranium), the net Coulomb electric force between all of the particles is greater than the nuclear strong force between any one pair of particles. In such this reaction, we separate the atoms just enough so the electric force overtakes the short-range nuclear force releasing loads of energy, though notably less than fusion.
Using concentrated light instead of gravity, scientists are performing a feat that can only otherwise be found within the hearts of stars. In the sun, immense gravity crushes four hydrogen atoms (1 proton each) to one helium atom (2 protons). In the process of fusion, two of the hydrogen atoms are annihilated releasing an exorbitant amount of energy in the form of Gamma radiation, the highest energy radiation there is. By the time the photons reaches the surface of the sun (upwards of 40,000 years due to a photon's meandering and bouncing amongst the mass and free electrons that make up the sun-soup), the entire spectrum of light is represented from Infrared, through visible light, with some surface photons retaining their Gamma energy. The sun consumes 6.224 x 1011 kg (622 billion kg) of hydrogen every second releasing all of the wonderful energy we take for granted today and will for another 4-5 billion years.
Hydrogen is readily available, as it's the simplest atom and thus the most abundant in the universe. One day we may see our world energized by little suns around the world. Yet, though scientists at Livermore were successful in producing more energy out of the single pellet than was put in, there's still a long way to go before the entire experiment can claim such odds. Stay tuned.
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