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Yet Another Method Of Achieving Nuclear Fusion
deglr6328 writes "Recent research has seen the use of the pyroelectric effect, the compression of bubbles using ultrasound and gas jet irradiation for producing nuclear fusion on small tabletop-scales. Yet another method can now be added to the list which uses ultraintense laser irradiation striking a borated plastic target to heat a plasma to billion kelvin temperatures and achieves aneutronic (clean) proton-boron fusion. (The PRL paper can be read online.) Though, like the other recently discovered exotic methods of attaining fusion, it does not look like a method which can be scaled up to ignition or even anywhere near break even, it still may have important use in the laboratory for the examination of such incredibly high temperature plasmas."
Why does a Hydrogen Bomb produce far more energy in the fusion phase than is put in during the fission phase? My only guess is that the extra energy is coming from the energy released by the nuclear bonds during the forceful disintegration of the atom. Any physics majors care to chime in?
Ever wonder why all those protons like to sit happily in the nucleus together even though they're all positively charged? Well it turns out that at REALLY small scales there is a force called (aptly) "the strong nuclear force" which is about a million times as strong as electromagnetism.
The amount of energy it takes to liberate a single nucleon from a nucleus is called the "binding energy per nucleon". . For different elements this value is different. The reason fusion and fission can both release energy is due to change in this binding energy per nucleon from the start of the reaction to the end of the reaction.
If you look at this graph you will see that at the begining of the graph it rises very steeply. The change from Hydrogen to Helium looks about 10MEV. This energy has to go somewhere and it's released as heat and light.
At around Iron the graph flattens out and then slowly starts to decend. Uranium sits right down at the bottom tail of the graph. Energy is released in fission because the end products sit further up the curve than Uranium.
Per reaction, Uranium fission produces a lot more energy than Hydrogen. Fission release around 250MeV and fusion releases around 17.6MeV. So why do we get so much additional power from a Hygrogen bomb? Well one mole of Uranium weighs 238 grams. In contrast, one mole of hydrogen weighs only 1 gram. The conclusion? We have a lot more hydrogen atoms per unit mass than we do Uranium. This means that we get 17 times more energy per unit kilogram than we do from Uranium . This is the reason the primary power source for the Hydrogen bomb is the Hydrogen and not the Uranium starter charge.
Simon.