Noise.
On Tue, Feb 11, 2014 at 5:00 PM, Kevin O'Malley <kevmol...@gmail.com> wrote: > > http://www.csmonitor.com/2005/0606/p25s01-stss.html > > > Coming in out of the cold: nuclear fusion, for real > > By Michelle Thaller, csmonitor.com / June 6, 2005 > > > > PASADENA, CALIF. > > For the last few years, mentioning cold fusion around scientists (myself > included) has been a little like mentioning Bigfoot or UFO sightings. > > > After the 1989 announcement of fusion in a bottle, so to speak, and the > subsequent retraction, the whole idea of cold fusion seemed a bit beyond > the pale. But that's all about to change. > > A very reputable, very careful group of scientists at the University of > California at Los Angeles (Brian Naranjo, Jim Gimzewski, Seth Putterman) > has initiated a fusion reaction using a laboratory device that's not much > bigger than a breadbox, and works at roughly room temperature. This time, > it looks like the real thing. [Editor's note: The original version misnamed > the scientists' institution.] > > Before going into their specific experiment, it's probably a good idea to > define exactly what nuclear fusion is, and why we're so interested in > understanding the process. This also gives me an excuse to talk about how > things work deep inside the nuclei of atoms, a topic near and dear to most > astronomers (more on that later). > > Simply put, nuclear fusion means ramming protons and neutrons together so > hard that they stick, and form a single, larger nucleus. When this happens > with small nuclei (like hydrogen, which has only one proton or helium, > which has two), you get a lot of energy out of the reaction. This specific > reaction, fusing two hydrogen nuclei together to get helium, famously > powers our sun (good), as well as hydrogen bombs (bad). > > Fusion is a tremendous source of energy; the reason we're not using it to > meet our everyday energy needs is that it's very hard to get a fusion > reaction going. The reason is simple: protons don't want to get close to > other protons. > > Do you remember learning about electricity in high school? I sure do - I > dreaded it whenever that topic came around. I had a series of well-meaning > science teachers that thought it would be fun for everyone to hold hands > and feel a mild electric shock pass their arms. Every time my fists > clenched and jerked and I had nothing consciously do with it, my stomach > turned. > > In addition, I have long, fine hair, and was often made a victim of the > Van de Graf generator - the little metal ball with a rubber belt inside it > that creates enough static electricity to make your hair stand on end. > Yeesh. > > Anyway, hopefully you remember the lesson that two objects having > different electrical charges (positive and negative) attract one another, > while those with the same charge repel. It's a basic law of electricity, > and it definitely holds true when two protons try to get close together. > Protons have positive charges, and they repel each other. Somehow, in order > for fusion to work, you've got to overcome this repulsive electrical force > and get the things to stick together. > > Here's where an amazing and mysterious force comes in that, although we > don't think about it in our day-to-day lives, literally holds our matter > together. There are four universal forces of nature, two of which you're > probably familiar with: gravity and electromagnetism. > > But there are two other forces that really only come in to play inside > atomic nuclei: the strong and weak nuclear forces (and yes, the strong > force is the stronger of the two, the weak is weaker. Scientists really > have a way with names, dont they?) I'm going to focus on the strong force, > as that's the one responsible for nuclear fusion. > > The strong force is an attractive force between protons and neutrons - it > wants to stick them together. If the strong force had its way, the entire > universe would be one big super-dense ball of protons and neutrons, one big > atomic nucleus, in fact. > > Fortunately, the strong force only becomes strong at very small scales: > about one millionth billionth of a meter. Yes, that's 0.000000000000001 > meters. Any farther away, and the strong force loses its grip. But if you > can get protons and neutrons that close together, the strong force becomes > stronger than any other force in nature, including electricity. > > That's important- all protons have the same charge, so they'd like to fly > away from each other. But if you can get them close together, inside the > volume of an atomic nucleus, the strong force will bind them together. > > > The whole trick with fusion is you've got to get protons close enough > together for the strong force to overcome their electrical repulsion and > merge them together into a nucleus. The sun does this pretty much by brute > force. The sun has over 300,000 times the mass of the Earth, which means > there's a lot of gravity weighing down on its core. > > > That pressure gets the sun's internal temperature up to several millions > of degrees, which means that particles inside the sun's core are flying > around at huge velocities. Everything is moving around so fast that protons > sometimes get slammed together before their charges have a chance to repel. > The strong force takes hold, and a new atom (helium) is born. > > In this process, some of the mass of the protons is converted into energy, > powering the sun and producing the light that will eventually reach the > Earth as sunlight. > > Scientists have gotten fusion to occur in the laboratory before, but for > the most part, they've tried to mimic conditions inside the sun by whipping > hydrogen gas up to extreme temperatures or slamming atoms together in > particle accelerators. Both of those options require huge energies and > gigantic equipment, not the sort of stuff easily available to build a > generator. Is there any way of getting protons close enough together for > fusion to occur that doesnt require the energy output of a large city to > make it happen? > > The answer, it turns out, is yes. > > Instead of using high temperatures and incredible densities to ram protons > together, the scientists at UCLA cleverly used the structure of an unusual > crystal. > > Crystals are fascinating things; the atoms inside are all lined up in a > tightly ordered lattice, which creates the beautiful structure we associate > with crystals. Sometimes those orderly atoms create neat side-effects, like > piezoelectricity, which is the effect of creating an electrical charge in a > crystal by compressing it. Stressing the bonds between the atoms of some > crystals causes electrons to build up on one side, creating a charge > difference over the body of the crystal. Other crystals do this when you > heat or cool them; these are called pyroelectric crystals. > > The new cold fusion experiment went something like this: scientists > inserted a small pyroelectric crystal (lithium tantalite) inside a chamber > filled with hydrogen. Warming the crystal by about 100 degrees (from -30 F > to 45F) produced a huge electrical field of about 100,000 volts across the > small crystal. > > The tip of a metal wire was inserted near the crystal, which concentrated > the charge to a single, powerful point. Remember, hydrogen nuclei have a > positive charge, so they feel the force of an electric field, and this one > packed quite a wallop! The huge electric field sent the nuclei careening > away, smacking into other hydrogen nuclei on their way out. Instead of > using intense heat or pressure to get nuclei close enough together to fuse, > this new experiment used a very powerful electric field to slam atoms > together. > > Unlike some previous claims of room-temperature fusion, this one makes > intuitive sense: its just another way to get atoms close enough together > for the strong force to take over and do the rest. Once the reaction got > going, the scientists observed not only the production of helium nuclei, > but other tell-tale signs of fusion such as free neutrons and high energy > radiation. > > This experiment has been repeated successfully and other scientists have > reviewed the results: it looks like the real thing this time. > > For the time being, don't expect fusion to become a readily available > energy option. The current cold fusion apparatus still takes much more > energy to start up than you get back out, and it may never end up breaking > even. In the mean time, the crystal-fusion device might be used as a > compact source of neutrons and X-rays, something that could turn out to be > useful making small scanning machines. But it really may not be long until > we have the first nuclear fusion-powered devices in common use. > > So cold fusion is back, perhaps to stay. After many fits and starts, its > finally time for everyday fusion to come in out of the cold. >
