Team Confirms UCLA Tabletop Fusion 354
An anonymous reader writes "A team of New York physicists has confirmed that a tabletop contraption made at UCLA does in fact generate nuclear fusion at room temperatures, using pairs of crystals and a small tank of deuterium. But unlike less reliable reports back in the 1980s, there's no talk this time of producing endless supplies of power. Rather, the technology could lead to ultra-portable x-ray machines and even a wearable device that could provide safe, continuous cancer treatment."
Key Application Overlooked (Score:5, Informative)
From TFA: I'm surprised that the article didn't go into more depth on the explosives detection angle, as a neutron generator is an excellent method for detecting fissionable material, and I'm sure the folks over at Homeland Security would like a better way to guard against nuclear devices being smuggled into our country.
For more info on neutron generators and their possible application in fissionable materials detection, please look here (PDF warning) [latech.edu].
Interesting (Score:4, Informative)
Re:Cool (Score:3, Informative)
Sorry to disappoint, but it's just not going to happen. These types of methods of fusion are always going to require more energy input than output. Efficient artificial reactors may be possible in the future, but for now they remain a pipe dream--especially 'cold fusion' ones.
Re:What? (Score:2, Informative)
Re:Interesting (Score:5, Informative)
So I'm assuming that there is no way even in principle this technology could be scaled to yield more power than it uses.
From the sound of what's going on, I think that's correct. The thing about a confined fusion generator is that it works through having the plasma at enormous temperatures. At these high temperatures the particles are slamming into each other at high speed, occasionally so hard they fuse together. This fusion itself produces more heat, so there's a feedback loop that's sustaining the reaction. This device sounds like it works through just accelerating particles with an electric field to high speeds, and then smashes the particles into one another. I don't see any potential for feedback here, so a sustained reaction seems unlikely.
Get the paper here (Score:5, Informative)
Re:Oh great... (Score:5, Informative)
Fallout is caused by one of two events:
1. Excess nuclear materials not consumed in the reaction are left behind.
2. The neutron radiation from the event interacted with nearby materials (such as the dirt on the ground) to create new radioactive materials.
Nuclear fusion is "clean" in that there are no radioactive materials left over from the reaction. However, it does produce an incredibly strong neutron flux which can easily create radioactive fallout in nearby materials.
http://en.wikipedia.org/wiki/Nuclear_fallout [wikipedia.org]
Given how destructive neutron radiation is, I'm somewhat surprised that they'd be talking about strapping a reasonably strong source to someone's person.
Re:This sounds oddly familiar (Score:5, Informative)
That's where Pons and Fleishman got hosed. They claimed a 300% power surplus without experimental verification. This announcement is different from that for several reasons.
1) These guys are specifically not claiming excess power.
2) They're claiming to have lots of high-energy neutrons.
3) This is actually the announcement of a second group of scientists repeating the experiment and successfully verifying the results of the first group.
In short, this announcement is nothing like the cold fusion debacle of the late '80s.
Regards,
Ross
Re:Get the paper here (Score:2, Informative)
Pyroelectric particle accelerator (Score:2, Informative)
Re:IS this really FUSION? (Score:3, Informative)
Re:Get the paper here (Score:1, Informative)
Re:Room temperature? (Score:2, Informative)
Wrong. Heat is random motion. If simple kinetic energy was all it took to have heat, then any gas cloud out in space with a large velocity relative to us would be extremely "hot." But we all know intuitively that things do not change temperature just because they speed up. The air in a moving car is not hotter than the air in a parked car. Heat is the random motion of particles with respect to each other. The collision of a few particles doesn't qualify.
When gas quickly depressurizes, it cools down. Ever wonder why? It's because as the gas escapes, the particles which are near each other tend to all move in the same direction (outward) and thus their random motions with respect to each other are decreased. Thus, the temperature drops. Or consider how a rocket nozzle works by focusing the molecular motions in a particular direction (by forcing the gas through a small opening to increase the pressure and then into a cone to suddenly decrease it), thereby converting the high pressure and heat of the exhaust gas into directed kinetic energy.
Learn more before making these kinds of proclamations.
Re:Oh great... (Score:4, Informative)
And what are neutrons? Oh yeah, just one of the most penetrating and dangerous forms of radiation. Why else do you think that when they had to find a form of radiation that could kill tank crews inside their vehicles, the viable choice was the neutron bomb?
Pure fusion bombs create huge numbers of neutrons. If the explosion is near the ground, these neutrons can activate the debris that gets sucked into the mushroom cloud and create plenty of fallout. (Not to mention, most bombs use a natural uranium case to get a cheap energy boost when it's fissioned by the extra fusion neutrons. Most of total the energy output is often still fission.)
And any amount of emissions that's intense enough to kill cancer tumors isn't exactly "small".
Also: Nowhere in the article does it mention anything about breaking apart massive atoms and leaving behind radioactive isotopes that are chemically reactive in the human body; Which, I assume, is what you're so worried about.
Instead, you add neutrons to the the elements already inside your body, thereby turning them into dangerous radioactive isotopes where they sit.
Re:Key Application Overlooked (Score:2, Informative)
SpeakerToManagers
A whole 2% are opened (Score:2, Informative)
Although the figure is somewhat disputed by the US Customs, who claim they inspect a larger percentage of what they deem "high risk" containers, apparently about 2% of all containers entering the US are actually inspected (i.e. opened and the contents examined).
Re:Key Application Overlooked (Score:5, Informative)
Let's do the math [nuclearweaponarchive.org]. A 1 MT nuke detonated at optimal blast height will knock down residential structures at a radius of 10 km, more solid buildings at 7 km, and at 5 km knock down reinfored buildings and kill people outright from the blast (and all other effects, such as high doses of radiation, have smaller radii). A surface blast would have a far smaller effect. The only real point of a surface blast is to generate radioactive fallout (an air blast generates surprisingly little, though it would still hinder clean-up and rebuilding).
So yes, in theory, a terrorist with a high-quality military nuke (let's imagine a few were sold out of the old USSR armory, and somehow still worked today (the tritium would have to be replaced, which is quite technical, but lets imagine a scientist came with the bomb)) could sit a couple of kilometers off the coast and destroy some structures along the coast. Good for psycological impact, but not much else, and insanely expensive to carry out. A 50 kt fission bomb, a far more likely scenario for a terrorist, would have less than 40% of the blast radius of the high quality military bomb, and would probably need to be within 1 km to be effective.
A surface blast over *land* is what a terrorist wants, because the radioactive fallout would cause a world of hurt. You'd get very little of that even 1 km off the coast, and even a ship at a dock would produce far less fallout than a bomb 1 km inland. It's *definitely* worth checking for nukes at ports of entry: the threat just goes down very fast as the bomb moves away from land.
Re:This sounds oddly familiar (Score:4, Informative)
I think the more important difference between this and Pons and Fleishman's cold fusion is that this is clearly fusion, and P&F wasn't. The effects P&F observed were probably the result of a chemical reaction and/or bad experimental design. They didn't observe any of the characteristic radiation or products.
FYI, this isn't the first tabletop deuterium fusion discovered. See bubble fusion [wikipedia.org].
Re:Fission? (Score:3, Informative)
You can think of their experiment like the classic Rutherford experiment, except they've got D+ ions being shot at a sheet of D. The two D+D fusion reactions happen with equal probability:
D + D -> T (1 MeV) + p (3 MeV)
D + D -> He3 (0.8 MeV) + n (2.5 MeV)
What they did in the experiment was to look for 2.5 MeV neutrons, because that reaction will _always_ produce a 2.5 MeV neutron. They also looked at associated X-rays. (If it was a fission neutron, it would probably be a different energy, and again, I can't find any reference to such a phenomenon.) Then they correlated their results to a computer simulation. I don't know why they didn't bother to look for the H and T. They may not have had the equipment, or they considered it outside the scope of the experiment's purpose as a neutron source.
The caveat to this experiment is that neutron and x-ray detection is something of an art, and must be done correctly; I'm not qualified to comment on their setup. This experiment makes sense according to normal physics, though.
Re:Room temperature? (Score:2, Informative)
In this case, I am almost certain (without reading more than the first 5 paragraphs of the article) that the particles are not thermalized, are not, in fact, in equilibrium, and therefore do not have a temperature. In that case, you should assume right off the bat that if someone mentions words like "temperature", "heat", "hot", that they are referring to the kinetic energy of the particles, as that is the custom (at least within physics), and indeed, only interpretation that makes sense.
Furthermore, you miss the obvious point that there weren't even trying to make fusion. This should have been clear from the fact that when they said "room temperature" they meant that it was relatively hot and not cold (that is to say, not at cryogenic temperatures). The article is simply bad reporting by people that don't understand what they're talking about (unfortunately, not so uncommon).