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Nuclear Fusion Discovered
prostoalex writes "Both USA Today and The New York Times are reporting on research group from UCLA led by Seth J. Putterman which has discovered a form of nuclear fusion. The impact of the discovery? 'While the device is probably too inefficient to produce electricity or other forms of energy, the scientists say, egg-size fusion generators could someday find uses in spacecraft thrusters, medical treatments and scanners that search for bombs.' The findings are published in Nature magazine."
First of all, humans "discovered" fusion in 1953 with the first fusion bomb, or "hydrogen" bomb. What this speaks of is controlled fusion.
Secondly, this isn't fusion on even a battery scale; this is a few thousand atoms per second or so. So unfortunately, it's not a matter of scaling up to produce a reactor. The amount of energy being put into the system dwarfs by thousands of times the energy from fusion being put out.
Third, this isn't even the discovery of table-top laboratory scale fusion. As an undergraduate, I worked on a muon catalyzed fusion experiment at TRIUMF in Vancouver. By the time I was working on the experiment in 1994, the fusion reaction in the experiment was so well understood that it was being used to analyze other properties of solidified Hydrogen.
And I'm afraid it's a little bit of a dodge to say it's "at room temperature". The article doesn't say this, but presumably this takes place in a vaccum, where temperature is basically undefined in any conventional sense.
So a very nifty result, but not a discovery, I'm afraid. It will very likely be useful to study the fusion process, or perhaps other things as well.
Craig Steffen
http://www.craigsteffen.net
A UCLA collaboration (Seth Putterman, Brian Naranjo and Jim Gimzewski) appear to have developed a fusion device powered by a pyroelectric crystal, a type of crystal used in cell phones to filter signals. When heated, such a crystal produces a large electric charge on its surface. The UCLA researchers placed a lithium tantalate (LiTaO3) pyroelectric crystal so that one side touches a copper disc. A tiny tungsten probe is then placed at the center of the copper disc. When the crystal is subsequently heated, a very large large electric field is produced at the end of the tugsten tip, ~25 billion volts per meter. This field gradient is so high that it strips the electrons from nearby deuterium atoms. The ionized deuterium atoms then accelerated by this field towards a solid target of erbium deuteride (ErD2). They collide with it at such high energies that some fuse with the target. A measurement of almost 900 neutrons per second was observed. This is 400 times the background! Although the amount of energy produced in this initial experiment was miniscule (~1E-8 jules), this technology could be used for things like microthrusters. There are pictures and movies on the UCLA's physics site. Reader richmlpdx adds a link to coverage at MSNBC.
I would have thought that the editors would have gotten enough complaints about this being a dupe. Oh well.
:-/
What this device really is, is not so much of a fusion generator as it is a neutron source. Nuclear physicists use sources such as these for processes such as starting atomic reactions and changing elements. (e.g. You can make lead into gold with enough radiation. Although plutonium production is a far more useful change.)
A nuclear physicist I know suggested that the Sonofusion concept might be useful for the same reasons. Unfortuntely, we are quickly piling up ways of using fusion as neutron sources, but have yet to come up with a single one to produce energy.
Javascript + Nintendo DSi = DSiCade
First of all, this is a dupe
Secondly, they haven't discovered fusion, they have invented a new type of fusion-based neutron generator. Several types of neutron generators are commonly known, and some are simple enough that you could build a working one in your garage. All of them use the same principle, more or less - high voltage, on the order of 100kV, accelerates deuterium ions into a deuterium (or tritium) containing target. So does this one.
The novelty is that they used a pyroelectric crystal to generate the high voltage. This makes the device small and self-contained, with no need for high-voltage electric machinery. All you do is heat-cycle the crystal with some 50 degree C temperature span, and you get fusion neutrons.
Note that like all fusion devices to date (other than bombs), this gadget produces a lot less fusion energy than is put in, and brings us no closer to having a fusion-based power source.
But it's a neat idea. And it makes a neat cheap laboratory neutron source.
"Cold" fusion is when the nuclei fuse at "low" temperature. Not just the outside of the reactor that is cold, but the actual nuclei that fuse are "cold". When you're talking about the temperature of atoms, or nuclei, the temperature is the same as energy. This reactor accelerates the ions to high energy, so it's not "cold fusion".
The original "cold fusion" apparatus (the one that didn't work, or at least no one was ever able to replicate the experiment) used an electrolytic cell with palladium electrodes in an electrolyte. Nowhere in the apparatus were the deuterium nuclei accelerated to high speed. The theory was that the current somehow induces the deuterium to infuse into the palladium electrode, where the deuterium nuclei get close enough to each other to fuse, without you having to clash them together at high energy.
That was the cool thing about it (pardon the pun). You didn't have to put much energy into the system, so you had more energy coming out than you had to put in, making it a feasable power source. If it worked:-).
They're not claiming it's self-sustaining. They're just claiming that it's novel, which it is, and that it's a neutron generator, which it is.
A commentary article in the current journal of Nature points out that "...portable neutron generators have found a wide range of applications, including welllogging for oil exploration, and the screening of baggage for airline security," but that "high-voltage power is required, and the apparatus is fairly complex."
This device is much simpler and more straightforward.
Third, this isn't even the discovery of table-top laboratory scale fusion.
True, but it is probably one of the simplest and most compact fusion/neutron generating techniques invented to date.
And I'm afraid it's a little bit of a dodge to say it's "at room temperature". The article doesn't say this, but presumably this takes place in a vaccum, where temperature is basically undefined in any conventional sense.
Please RTFA before you critique it. This method uses a pyroelectric crystal, heated presumably up to 100-200 Celsius or so, and a thin deuterium gas and a target made of erbium deuteride, both of which are presumably at or near room temperatures.
In any case, by "cold" fusion we typically mean "at temperatures easily maintainable in a lab," to distinguish from "hot" fusion which occurs at many thousands or millions of degrees.
Also, you should know that even in a "perfect" vacuum, temperature is and can be well-defined, usually by thermal radiation equilibrium with the enclosure. Even outer space has a well-defined thermal radiation background, which I think is within a couple degrees of absolute zero.
Their setup: The 'crystal' mentioned in the mainstream articles, is a z-cut lithium tantalate crystal (LiTaO3), with the negative axis facing outward onto a hollow copper block. A tiny tungsten probe (80 microns long and 100 nm wide) is then attached to the other crystal face. This probe acts as a tiny mast for the electric field so that there is a powerful electrical field at the tip of the probe. Then there were a bunch of fancy neutron-counters and single-photon counters bundled around it.
What they did: First they added deuterium gas (at 0.7 Pa) and then cooled the crystal down using liquid nitrogen (to 240 K). Then they used a little heater to increase the chamber temperature slowly.
What happened: Less than 3 minutes later, and still below 273 K (0 degrees Celcius), the neutron signal rose above the background level. There were x-rays coming from the probe tip, and a whole bunch of neutrons. After a few more minutes, the electric field was so strong that it caused arcing between the probe tip and the enclosure (because they kept heatingthe crystal, and the field thus kept getting stronger). The arcing stopped the process (and I'd guess it damages the crystal?).
They added a few links in the article to previous papers: a pdf describing the concept they are trying to harness, another pdf with more about how they use the crystals with the deuterium gas, and a brief abstract.
I think this is pretty cool. I bet/hope that before long (within 10 years), this will be powering small extrasolar probes.
Pretty neat stuff. I don't even mind dupe posts when they're on such important stuff.
Why would you waste a perfectly good fusion device to make a dirty bomb? Especially a fusion device which absorbs more power than it produces. The point of a dirty bomb is to, you know, explode. I guess you could powder the device with cesium and then hit it really, really hard with a sledgehammer...
Oh, and the department of defense funds this because the department of energy has no interest in higher-sensitivity methods of detecting fissile materials. They can find their fissile materials just fine with the technology they have, thanks.
...it's really a sad day for America when we require a goddamn ACT OF CONGRESS to make our DVD players work properly. ~
neutrons are a lot better for producing radiographs, for instance if you X-Ray a bullet you can see the bullet itself, the cartrige caseing, and a bit of the primer, with neutrons, you can easily see everything the X-Ray saw, but even the gun-powder grains grains inside the bullet's cartrige.
The difference is enough to tell the difference between a CD player boom-box, and a bomb inside a boom-box even when the explosive are hidden inside the batteries or capacitors.
A far as detecting fissile material I doubt that they need any help; when I had a thallium stress test, there was a sign telling us not to cross the border for a couple of days, without telling customs we had just had a stress test because they'd detect the radiation we were giving off.
Apocalypse Cancelled, Sorry, No Ticket Refunds
This was covered yesterday.
.XData
Going briefly over the available documents on this, it appears that this technique consumes orders of magnitude more energy than it produces. This would preclude energy generation as one of the potential applications, which is usually regarded as the most promising potential application of cold fusion. Most of the other potential applications mentioned in the articles use this as a neutron generator, but there are other well known ways of achieving that...
The road to hell is paved with good intentions.
The only other ways to achieve neutron flux (that I'm aware of) are to (1) use a particle accelerator collision to release neutrons (i.e.: spallation) or (2) to use a radioactive source (or running nuclear recator) and guide the flux of exiting neutrons. Both of these are quite large and not very portable.
Although this research is not going to give us energy production, it is the smallest neutron source I've heard of (palm-sized according to article). This in and of itself is quite exciting, and it would have numerous applications in industry. Neutron sources right now are used to image industrial materials (it can be used to map the internal stress distribution in pipes, aircraft components, etc... and it can get images through materials that would block x-rays). Having portable neutron-imagers would be useful to industry for doing stress analysis/imaging on components while they are in actual use. I can think of lots more applications, but I'll leave it at that.
For those interested, here is the abstract of the Nature article in question (the article is already available online, to subscribers, even though it officially releases in tomorrow's issue of Nature):
Nature 434, 1115-1117 (28 April 2005) | doi: 10.1038/nature03575
While progress in fusion research continues with magnetic[1] and inertial[2] confinement, alternative approaches--such as Coulomb explosions of deuterium clusters[3] and ultrafast laser-plasma interactions[4]--also provide insight into basic processes and technological applications. However, attempts to produce fusion in a room temperature solid-state setting, including 'cold' fusion[5] and 'bubble' fusion[6], have met with deep scepticism[7]. Here we report that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions. The electrostatic field of the crystal is used to generate and accelerate a deuteron beam (> 100 keV and >4 nA), which, upon striking a deuterated target, produces a neutron flux over 400 times the background level. The presence of neutrons from the reaction D + D --> 3He (820 keV) + n (2.45 MeV) within the target is confirmed by pulse shape analysis and proton recoil spectroscopy. As further evidence for this fusion reaction, we use a novel time-of-flight technique to demonstrate the delayed coincidence between the outgoing alpha-particle and the neutron. Although the reported fusion is not useful in the power-producing sense, we anticipate that the system will find application as a simple palm-sized neutron generator.