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More Evidence for Tabletop Fusion
heptapod writes "Researchers at Purdue University have statistically significant evidence that their tabletop fusion experiments were successful. Yiban Xu's experiment different from an earlier Oak Ridge experiment using a different and cheaper source of neutrons than Oak Ridge's pulse neutron generator. Surpassing break-even point still eludes the grasp of science."
"Surpassing break-even point still eludes the grasp of science."
hmmm does it?
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"When it's time to railroad, you get railroads." Or however the saying goes.
This question is one I've been thinking about for a few years now due to an idea for an invention I've got (not cold fusion, though), plus some stories I know of. The most relevant one is an episode of Outer Limits (the series from the 90s, not the one from the 60s).
In the story, an expelled physics student detonates a small 'cold fusion bomb' in a campus clocktower as proof of the technology, then takes a physics class hostage with another device. He demands that the people who have tormented him in the past be brought to the courtyard and shot in front of him, or he'll detonate the more powerful device he's got with him.
While the military is trying to figure out what the hell it was that detonated (since they don't believe in a cold fusion bomb), the negotiator is trying to figure out what the deal is with the hostagetaker. It comes out that, among other things, he believes there's a reason we've not found any signals from other species. The cold fusion technology is so simple that anyone can make it. When a species gets advanced enough to realize how easy cold fusion is, he says it's inevitable that a species will destroy itself before it can get mature enough to handle its technology. The negotiator then says, well, tell us what led you to the idea, and we can try to steer science around that until we can mature enough to handle it. The guy thinks back to what started him on the path to cold fusion - a physics test with the question, "Demonstrate why cold fusion is impossible."
I'd say it's inevitable that we WILL have this technology. How simple it winds up being is unknown at this point, of course, but hopefully it'll be complex enough that not every nut in a garage can do it.
What about the energy costs of gasoline production? I love how people, in their attempt to discredit new technologies, talk about the "hidden" costs of these new technologies (I do realize they exist, however) while not remembering that our standard energy sources also have a signifigant number of "hidden" costs.
But, even though you do have a small point, at least all the pollution is centered in one or two locations, instead of being spread all over thousands of miles by the vehicles themselves.
I wouldn't toss ITER aside before I get to at least read the journal article on a few of these desktop setups. I'd still like to see what pressure they're operating at, temperature ranges, D/T enrichment, reaction rate, bubble size, mcnp models (a vised geometric plot at the least), fluent models, etc. I just don't trust science magazine or a run of the mill newspaper to publish groundbreaking science that's on par for an engineer to read, since those cater to people without much knowledge of the engineering feat discussed in the article. But that's the nuclear field (or any engineering for that matter), we're supposed to be skeptical as hell until it's widely duplicated. If I can do it in my lab, then I'll believe it. Or at least see it in someone else's lab who built it from scratch from nothing but the other researcher's blueprints. And controlling plasma with magnets isn't too hard, in fact it's down to nearly an exact science where only a few unknowns remain, mainly the occurance of MARFE's, diverter material protection, and so forth. The largest problem lies with protecting the magnets from the 14-MeV neutron flux exiting the core. But still, I wouldn't toss aside ITER just yet. It's got some work to do, but it's a pretty sound model for a large scale fusion power plant.
I am not a Physicist but in any energy producing technology the source of fuel is the bottleneck. For ex. the antimatter propellant which is highly effecient but creating the fuel source(positrons) is the problem. I smell something similar here but I might be wrong.
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Where's the nuclear powered car we were promised back in the 1950s?
Some genius figured out that providing every man, woman, and child with sufficient nuclear material to create an atomic pile wasn't such a good idea?
From a technology perspective, there were a few other problems as well. Off the top of my head:
- Radiation: You need a lot of shielding to stop the "hard" stuff like Gamma, Neutron, and X-Ray bursts from escaping a functioning pile.
- Weight: All that shielding results in a lot of extra weight.
- Inefficiency: A "simple" atomic pile may be relatively safe (from a runaway reaction perspective), but it's not particularly efficient, nor can it be actively controlled.
In any case, the Ford atom car was never seriously developed. It was just an "Atoms for Peace" idea that was kicked around as a promotional gig.
A far better use for nuclear tech is in Merchant ships. Today's merchies pay extraordinary amounts for diesel fuel, have limited range, and burn fuel at the rate of gallons per feet. Nuclear reactors could provide these ships with more cargo space (no fuel tanks!), greater speed, longer endurance, and better turn-around times.
Unfortunately, the case of the NS Savannah turned off the private sector to the idea of a nuclear merchant ship. There was no real problem with the ship herself, but rather the fact that she was ahead of her time (crude was still VERY cheap back then) and one of a kind (no infrastructure to support her) meant that she couldn't compete in the market.
The equation today is a very different one from the equation back then, but concerns related to the control of reactors and nuclear fuels have placed road-blocks in the way of reviving the idea.
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It's interesting that the original professor's experimental results were discredited by the methods he used to detect fusion. First he detected neutrons, but then there was controversy about whether he was detecting fusion neutrons or png neutrons. Then, when he changed certain things, and still detected neutrons... everyone questioned whether or not they were background neutrons or fusion neutrons. Basically, they wanted to see the moment of neutron detection coincide with the moment of light creation down to the nanosecond (I think).
Now, these guys are using other methods of detecting fusion by neutron energy levels, and tritium. I just hope that the levels they detected were WAY above the statistical normal amount of 2.5MeV neutrons and tritium in deuterized-acetone controls.
"The two researchers used an identical "carbon copy" of the original test chamber designed by Taleyarkhan"
If memory serves, when the Taleyarkhan et al. originally published their results, hundreds of scientists tried to reproduce the experiment. (After all, sonoluminescence is a cheap experiment to set up) I think only one group got a positive result.
One of the criticisms of the original work was that the original experimental set up was a little dodgy. It was suggested (among other things) that Taleyarkhan was receiving false positive spikes though inductive pickup between the drive for the neutron generator and the detector.
Further, most of the work I've read on sonoluminescence indicates that the estimates of the temperature and pressure inside the imploding bubble are not as high as the numbers that require fusion. Sure, when work on sonoluminescence was young, there were lots of crazy ideas and claims flying about. But now, it is considered unlikely that the bubble could stay perfectly spherical during the collapse. Experimentally, it has been shown that the presence of gasses in the water dramatically affect the intensity of the produced light. (See work by Putterman) One theories actually rely on the gasses causing imperfections in the bubble wall as it collapses, allowing a high pressure jet of water to shoot from one side to the other, fracturing the opposite wall. (Prosperetti)
Another theory is that the the light observed during sonoluminescence is blackbody or bremsstrahlung radiation, because the sorts of pressure and temperature mentioned in this article would allow this (and the experimentally observed spectrum is pretty close to that predicted by these models) but you should also see other effects on the water afterward, like disassociation and experimentally, this has not (as far as I know) been observed (see Eberlain's papers)
Not only that, but fuel for very large diesel engines contains lots of residual oil, and is very high in sulfur. 5000 ppm plus. I understand that England recently traced the source of some acid rain problems to maritime activity. They've practically eliminated their sulfur output from coal power plants, etc, so boats are now the biggest producer.
That heavy diesel fuel is nasty stuff. Basically, its what's left over after they boil off all of the gasses, gasoline, kerosene, road use diesel fuel and the lower grade heating oils. They have to pre-heat it quite a bit to get it to burn in an engine, otherwise it's about as good as filtered crude oil--slightly less viscous.
Nuclear power would be a huge step forward in this area... I can't agree more. Throw in some modern reactor and propulsion designs and you'd have a terribly efficient and manuverable ship. Might even make fuel a bit cheaper for the rest of us if it caught on... Bonus.
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Its the other way round. Cavitation *does* seem promising. They didn't scale it up yet. In theory, surpassing break-even should be possible with it.
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There was a BBC Horizon documentary on this nuclear fusion sonoluminescence phenomenon that casts strong doubt on the validity of previous work conducted by this researcher. The acid test for the occurence of fusion is the release of a neutron at the exact instant that the flash of light from sonoluminescence occurs. The Horizon team used a detector that can record the neutron releases at the required instant in time. After recreating Taleyarkhan's experiment according to his published journal papers, results were disappointing. None of the neutrons that were detected occurred at the same instant of any of the sonoluminescence flashes. The extra neutrons were explained away as originating from the emitter used to generate bubbles, or from external sources. No doubt rivals will challenge the statistically significant tritium claim. Tritium does occur naturally in significant quantities in any mass of heavy water (deuterium oxide).
Unfortunately, there are still problems with modern-day pirates in a few places in this world. Worrying about the loss of a standard diesel powered ship is bad enough, but the loss of a nuclear powered ship would be even worse.
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So what would happen if you used deuterated acetone in a cavitaion device such as the hydrosonic pump? (see, http://www.hydrodynamics.com/product_pics.htm)
Everything I see on this shows there doing the work under atmospheric pressure. I really think they need to move to very high pressures and check the fusion rates agianst pressure. Although sonolumnescence under extreme pressures is probably a big research area in general you would expect the liquid/phase to become more ordered resulting in higher collapse energys potentially very high somewhere in the phase diagram. In fact if I'm right then there is a very high probability that gas giant planets actually heat themselves via this sort of high pressure desktop fusion instead of simply heat from contraction. I bet with the wealth of organic/organometallic substances/mixutures and high pressure phases you can hit the perfect system. I googled around to see if anyone has measured neutron emission from gas giants and drew a blank. Does anyone know if its ever been measured ?
I hear it's ~10 $G for iter. That's not exactly chump-change. Especially since we're not actually sure that even after ITER we'll have a working plant or a path to one. In addition, your scaling arguments (I've heard elsewhere that the minimum size of a plant would have to be ~10 GW) imply very very large plants. That may be to large to be feasible - a 10GW plant is a pretty big investment.
One problem with very large tokamaks is that although they are above breakeven, it's not by much - which means that you have to recirculate large amounts of power. That makes for a very large and expensive generator facility.
I also understand that the amount of tritum circulating in a working plant would be enormous; much, much larger than ever used before. Tritium is notoriously hard to keep contained - so it's not obvious that a fusion plant wouldn't have issues with radioactivity releases...
My personal opinion is that it is best to stick with our Gen-IV nuclear plants when it comes to fission.
(Actually, I wasn't thinking of a hybrid based on tabletop fusors, but rather tokamaks). Wouldn't a hybrid allow you to use a smaller (and presumably more feasible) tokamak as a neutron source, while at the same time the sub-critical fission blanket could be designed very safe, since neutron economy isn't such a driving concern? You can imagine a blanket that gives a gain factor of 100, and a tokamak at 0.1 of breakeven, and you still have a feasible plant.
In addition, it would allow you to burn U238 or even nuclear waste instead of just U235. Seems like a win-win-win to me. Fusion gets operational experience and increased development funding, the country gets a good nuclear energy source, we're no longer oil-dependent or dependent on limited amounts of U235, and it reduces the waste issue (which is what is going to kill even the Gen IV plants). As an aside, it's interesting to note that even nuclear weapons are fission/fusion hybrids... we've never extracted pure fusion energy in any quantities, controlled or not.
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