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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."
You also assume that hydrogen is already available and its potential is 0 then you bring in the gravity and eventually the energy from the gravity gets emmited during fusion.
Some energy should have already been spent combining and 'creating' the hydrogen from the Big Bang soup of protons, neutrons and electrons. Of course the energy for the Big Bang should have come from some place, but that is another question [God anoyone? - *warning* lame flamebait attempt]
To release that energy you would need to break the nuclear bonds of hydrogen and then it will become helium. Think of it as wanting to get over a very tall mountain and on the other side there is a much deeper valey than the one you are on. But to get to the longer downward slope, on the other side, you need to overcome the upward slope in front of you.
In case of H and He transition, as someone already pointed out, the difference in the energy is just a little (the valey on the other side is just a little deeper than the one are on now). But when you have billions and billions of small differences -- they add up and you get the Sun (or an H bomb).
Yeah. You should have been tought that in high school physics. The Strong Nuclear Force (the one which holds nuclei together) is the strongest force available to us, by a wide margin (followed by electro-magnetism, then weak nuclear followed by gravity. Someone recently figured out that the weak nuclear force can be tied into electromagnetism, and I think they actually call it "electroweak" or something like that.. I can't quite recall at this moment.. all that Grand Unifying Theory stuff's still a little vague to me).
Basically, if you can overcome the electromagnetic repulsion forces that force the protons apart due to their like charges, the strong nuclear takes over and the two protons come colliding together at emense forces. If you're looking for an answer to what actually drives the Strong Nuclear Force, well, take a ticket and get in line. Once they figure that one out, we'll have figured out what make the "fundamental forces" fundamental, and know a hell of a lot more about how our universe is put together.
It's possible that Desktop Nuclear Fusion that yields positive energy to us is just around the corner. And with all of the discoveries recently on how the internals of the "subatomic" particles work, I'd say we're closer to it than we have ever been. But these are the kinds of things that simply can't happen overnight, and I guarentee that if anyone did come up with the solution, it'd take us 60 years just to get it into service. So many industries out there who rely on this kind of technology not existing. Imagine what all of the coal refineries, natural gas refineries, solar power farms, nuclear power plants.. they'd all instantly be out of business if this thing could even pull of a 1% positive yield. But of course, this is all speculation. My guess is that we're still a good twenty years off at least, and that the positive solution will have something to do with how neutrinos work/are produced.
"Victory means exit strategy, and it's important for the President to explain to us what the exit strategy is." G.W.Bush
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.
Seriously, the problem here is that you're required to input a tremendous amount of force to overcome the nuclear bonds that hold the atoms together. As long as you have to put that force into the system, you're not going to get surplus energy out of the system. Simple physics. You can't get more energy out of a reaction than it takes to reverse it. The same reason why hydrogen cars that run on electrolyzed water don't work.
Nice idea, but, I'm afraid it's not like that. There are basically two forces involved here: electomagentic forces and the strong nuclear force. The EM force tends to keep atomic nuclei apart, since they are all positively charged. In "normal" matter they stay far enough apart to allow a bunch of electrons (negatively charged) to get in between and "screen" the charges. Meanwhile the strong nuclear force wants to pull nucleons together to make bigger nuclei. It's really powerful, as its name suggests, but also really short range.
The net effect of the interplay between these two forces (and some other considerations which I will overlook for now) is that the most stable (equivalently lowest energy) state for matter in quantities of less than a few solar masses (beyond which gravity starts to play a role) is as iron-56 nuclei. This is basically as many protons and neutrons as you can squash together and stillhave them all be in range of each others strong nuclear forces. Put in more and the electrostatic repulsion starts to dominate, put in fewer and the strong nuclear force would still pull in more if it could.
So, you can, in principle, get energy from any nuclear reaction that moves things towards iron -- fusion of light elements, or fission of heavy ones.
So, why is the whole universe not made of iron already? Basically the answer is that it got stuck!. When the universe was very hot and very dense indeed, it was a see of protons and neutrons constantly smashing into one another, sticking briefly to make nuclei and then being smashed apart by the next collision. The temperature was so high that thermal motion of the particles overcame the electromagnetic repulsion. When it cooled, it did so so quickly that the protons and neutrons didn't have time to form into iron nuclei, or indeed into many nuclei at all. That's why, before stars got into the game the universe was mostly hydrogen, with a decent amount of helium and only traces of other things.
Now, at the temperatures found in most of the universse, when two light nuclei collide, the electromagnetic forces cause them to bounce before they get close enough for the strong forces to make them stick. In a star, or a hydrogen bomb, or one of the pieces of borated plastic in this laser experiment, temperatures and densities are high enough that sometimes two nuclei smash together had enough to get past the EM repulsion and feel the strong force attracting them, whereupon they "snap" together, releasing a lot of energy.
If you want a very poor analogy, consider a room with a powerully magnetic roof a vibrating floor and a lot of ball-bearing. Initially, all the bearings are on the floor. Even though it would be a lower energy state for them to be stuck to the magnets in the roof. It we turn up the vibration (temperature), initially not much happens, but eventually we reach a temperature where a few bearings get close to the ceiling and are then pulled in hard by the magnets, releasing lots of energy as they "thunk" into the ceiling. This is what we are trying to do in a fusion reaction.
If we take the same analogy and turn up the heat still hotten, we recreate conditions in the original big bang. Now the room is full of flying ball bearings moving so fast that they are as likely as not to knock free any that get stock to the ceiling.