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Low-power table-top fusion 89

Posted by sengan
from the not-a-power-source dept.
SEWilco writes "Lawrence Livermore National Laboratory scientists described Tuesday producing fusion with a mere million-dollar machine. It was described at this APS Centennial session. Bursts of neutrons are detected, the hallmark of fusion that `cold fusion' was missing" Update: 03/27 02:27 by S : In somewhat related news, muggs wrote in about a new laser-based method for watching atoms bond. It relies on using X-ray diffraction patterns to locate the moving atoms.
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Low-power table-top fusion

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  • If, indeed this is true, then the next few years are going to make the industrial revolution look like a flea on a lumbering elephant. We are living the revolution, folks. Love every minute of it.
  • Well, that may be overstating it a bit. Cheap neutron are nice but this seems more evolutionary.

  • by Anonymous Coward
    Yes and no, this is good.

    In the 60s the folks at Zion, IL promised the electricity from the twin nuclear reactors would be so inexpensive we could get rid of our electric meters, it wouldn't be worth the effort of ComEd to read them. Not.

    Now with Zion/Byron/Dresden decommissioned, you want to run the meter reader off your property.

    I wonder if this will ever make it to electric production.

    I wonder if this technology will ever get into the hands of those who want revenge against the US. There are so many.

    Considering the espionage that has occurred at Lawrence Livermore in the last two years, we should 1 fear this will be used against us 2 just give it to our enemies and apologize to the families of the Rosenbergs.
  • I'm just curious about how the energy output of this thing compares to the energy required to power the laser. From reading the article, I'm pretty sure that it absorbs more than it releases, but if its not too big a difference, just a little more work could possibly turn this into a much bigger deal.
  • The article states (well, infers) that the intended purpose of the device is to produce neutrons, not to provide power.
  • by Anonymous Coward on Friday March 26, 1999 @07:34PM (#1960440)
    Phil Farnsworth, who invented TV, sold out most of
    his interest in TV and went on to be a borderline
    crackpot with something called the Farnsworth
    Fusor well into the 1960's -- it was a
    similar-sounding fusion device. Others thought
    that he was on to tomething. (See "The Farnsworth
    Chronicles" somewhere on the web) Anybody know how
    much connection there is between Farnsworth and
    this project?


    GE demonstrated fusion at the NY World's Fair in
    1964. They had some giant device that would charge
    up all kinds of coulombs, and then k-blamm -- a
    big flash and a bang -- and they would announce
    that fusion (but probably only a half-handful of
    nuclei or so) had taken place. Same story, lots
    of energy in, little energy out. But still there
    are scientific uses for the neutrons.

  • Analog magazine had an article a few months ago
    describing how to duplicate Farnsworth's fusion
    system with roughly high-school level physics lab
    equipment. Recommended. Wear your lead BVDs.
  • by bolx (30818) on Friday March 26, 1999 @07:58PM (#1960443) Homepage
    A while ago, when I was a lad, doing 'A' level physics (16 to 17 years old), I did some research into renewable energy sources, to discover that some people consider the holy grail of renewable energy lies in the field of genetic engineering, and since hearing their ideas, I tend to agree. Some may consider it a `Frankenstein science', but just for a moment imagine a world where a photosynthesis reaction provides the decomposition of water to its base elements, hydrogen and oxygen. These may then be re-combined in an exothermal reaction to provide heat. Bearing in mind that it is heat which powers almost all continuous electricity generation to this day -- granted some hydro-electric power (eg. the Dinorwig [fhc.co.uk] plant in Wales) provide extra energy to the National Power Grid during eg. the cup final -- whithout which there'd be no WWW, no /. and I'd never have found out that it was researchers not far from home who discovered cold fusion [bbc.co.uk].

    Oh yeah, I mentioned a derivative of fusion energy. Well it's the Sun that fuels the plants that would energise the reaction, and we all learnt in school that the Sun is only the solar system's biggest ever fusion reactor.


    PS. Why the nick? Well it's the mutt's nuts!
  • Wired had an interesting piece on cold fusion a few months ago. After reading it i had the feeling that CF really does exist. Unfortunately it is very dependent on some unkown qualities of an expensive metal that is needed for the process and is also very unreliable. It also does not seem to be able to produce enough energy output to be overly useful (at least at this time). Due to the bad PR of the "scandal" CF is also a very unfashionable thing to be doing research in.
  • It seems to me that the efficiency of the
    device is most likely pretty bad. I dont know for
    sure, but it looks like the clusters would have to
    be in the laser beam, and even then its random how
    many of the atoms colide.
  • I worked at Princeton U's Plasma Physics Labs around '80-82 as a tech. The motor/generator set for the TFTR (last one built) weighed 270 tons, if that's any indication of why the "desk-top" part is cool about this story.

    Now THAT was a cool job. That's where I first saw a trackball. It was hand-size, military-looking with two buttons at the top, and we had to build the interface ourselves.

    Uphill in the snow, both ways. :-)
  • The femto-laser fissions Uranium, it doesn't fuse anything (though it could be used for fusion, the point is that it's being used for fission).

    Both /. and the news site have it wrong, unless they're leaving something out of the article.

  • I have read a bit about the Farnsworth fusion devices.

    They weren't crackpot "fringe science," but ultimately they lost funding when just about everything was focused onto magnetic confinement (pardon the accidental pun, please).

    Farnsworth's device worked by rerouting electron beams and creating a spherically shaped region of electric potential that would trap protons and cause them to fuse.

    I think if you fueled it with deuterium, it would produce neutrons but not break even.

    There are about a zillion different ways of producing fusion at about this stage of development, i.e. throw a bit less than a million dollars at it, (probably in Farnsworth's case, a lot less), and produce neutrons, but not approach breakeven.

    I think some of them might be a lot better than Tokamaks if they received Tokamak-level funding.
    Phil Fraering "Humans. Go Fig." - Rita

  • You don't find this interesting????? Spaceships drives.

  • by Anonymous Coward
    This isn't a way to make lots of power - the cool thing is that there is some fusion going on and hence some neutrons coming out. These neutrons can be used for everything from medical research to technology development. The artical pointed out that it's not a generator!!

    Very cool - saw stuff about a similar device in New Scientist a few years ago and had been wondering recently what had happened to it. This ain't the same device, but it does the same job...
  • The femto-laser fissions Uranium, it doesn't fuse anything ...
    Both /. and the news site have it wrong, unless they're leaving something out of the article.

    I do believe you only read the box at the end of the article. The story is on D+D->He fusion.

    But speaking of which, I was at an Open House in the Univ. of Illinois (UIUC) physics department in 1994. They were showing off a small fusion reactor (a sphere about a meter across) which accelerates plasma into the center, and causes fusion and hence produces neutrons. The idea was to use this source to calibrate the detectors for Princeton's (?) tokamak reactor.

    In other words, small scale fusion reactors already exist, so why is this one special, other than being novel for using a laser for acceleration instead of an high-voltage electric field?

  • by Anonymous Coward
    While there is a fair bit of use for such a fuel, it won't solve the world's energy requirements. As you pointed out, the energy comes from the sun, and there is only so much energy in solar radiation. This isn't to say that it will not be useful, just wanted to point out that the most important thing is still to design stuff that's as efficient as possible and so minimises energy consuption in the first place...
  • The article wasn't there! My only access to the net currently is through a menu-based shell account. Sorry.

  • Fair enough, in all honesty it is a pipe-dream, but if it were to be produced, it would be self replicating and incredibly cheap to implement, especialy if some sort of oceanic hydroponic plantation were set up -- again a *long* way off.
  • by Anonymous Coward
    Geez, these guys should win an award for finding a more expensive method for doing the same job worse than an existing technology.

    A few years ago, you could buy a pulsed neutron generator (model 811-A) from Schlumberger-EMR Photoelectric for about US$100000. (I believe that was the correct price.) It could generate 2x10^8 neutrons per second when operated at 100kV. (Of course the duty cycle isn't a full second.) Some laboratory neutron generators have achieved maximum neutron fluxes of 1.4x10^12 n/cm^2/sec.

    The oil industry uses these things for well logging. You can measure the porosity of rock strata with neutrons by counting the number of neutrons reflected by the interstitial water. You lower one of these things down a borehole along with a neutron detector. You pulse the source and count the number of neutrons reflected back to your detector as a function of time. The more porous the stratum, the longer you see neutrons being backscattered.

    Fred Bacon
    Aerodyne Research, Inc.
    (but not speaking for them at this moment.)
  • I know I should know this, but... What's the difference between Fusion and Cold Fusion? Is it what it sounds like (Cold Fusion generates less heat)?

    Yeah, I know, I'm an idiot.

    -Eric
  • I personally wouldn't want to be anywhere near a fusion explosion of a "half-handful of nuclei or so" -- or where you talking about how many you could count on one hand?
  • by remande (31154) <remande.bigfoot@com> on Friday March 26, 1999 @08:45PM (#1960459) Homepage
    Of all things...fission.

    Currently, fission requires a critical mass of fissionable material. This is because you need the neutrons that a fission reaction gets to hit other fissionable material to keep the reaction going.

    If tabletop fusion becomes cheap enough, you could put it in the center of a subcritical mass of fissionable material and stop relying on the fission reaction to supply its own neutrons. It would be fail-safe as well, because you stop the reaction by turning off the laser.

    And the above may result in tabletop _fission_. Usable as a power supply or a weapon. Atomic-powered airplanes, or nuclear SAMs to shoot them with. Either way, I'm scared.
  • What's the difference between Fusion and Cold Fusion? Is it what it sounds like (Cold Fusion generates less heat)?

    Ah, well, normal fusion (as takes place in stars) requires extreme temperatures and pressures to work. H-Bombs, which are fusion weapons, used to use an A-Bomb (fission) as a trigger. Nowadays I think they use some sort of really neat plastic explosive, but it's still not really useful for power generation or anything.

    Cold fusion is much less demanding. The much-hyped cold fusion thing a while back was said to take place in a glass jar. Unfortunately for me and my nearly working DeLorean, it looks as though this was a hoax - at any rate no one seems to have reproduced Fleischmann and Pons' results.

    The real trick is to get any sort of controllable and safe fusion process to output more (lots more, really) energy than it consumes. Then it'll be practical. Oh, don't go assuming that it's entirely safe, as it may indeed output a good deal of radiation, with solid waste in the form of the actual reactor. OTOH, we finally get some more helium (a non-renewable resource, IIRC).

  • Here's why you should not be happy about this story. This device doesn't produce useful fusion energy, but it does produce hot neutrons, and it does so cheaply. What good are hot neutrons? They can be used to transmute non-fissionable isotopes of into fissionable isotopes.

    Fissionable isotopes are rare. Denying third-world bohemian have-nots access to fissionable isotopes is the linchpin of our nuclear non-proliferation strategy. Therefore, if someone can easily cook up fissionables in his basement, then a future imperialist meddling in some irrelevant nowhere country's civil war could provoke a nuclear response by the Elbonians.

    Be afraid, be very very afraid.
  • Fusion that occurs in the hearts of stars does so at a relatively high temperature. Millions of degrees. Various fusion research projects focused upon somehow replicating this temperature on earth. (This is relatively hard to do unless a nuclear explosion is going on in the immediate vicinity.)

    "Cold Fusion" demonstrations took place at room temperature. Since room temperature even in August w/o air conditioning is far less than several million degrees is so much cooler (relatively speaking) as to be deemed "cold."

    Cold Fusion would be a Bad Thing, too, since it would permit Bad Guys to build nuclear weapons materials using their Mr. Fusion power generators' neutron flux.

    btw, after the Elbonians cook up cheap fissionables, they can design their nukes using Beowolf clusters of 486s.

    Sleep well, America.
  • why?
    Well, think about this development in terms of the US's usual military-industrial complex. Tabletop fusion? The pricetag would probably be a few million at least for an apparatus. The usual mindset has been to think bigger, more powerful, etc.
    It is only in the past few years, with the mars observer, etc, that our government (and its research partners) have been able to see the benefit of smaller, leaner programs. Why spend many billions now on a collider an ingenious solution such as tabletop fusion can be designed? Hopefully, as developments like this occur more and more, our government will be spendig our money on a barrage of smaller, more intelligent programs rather than just a few large, impracticle, monolithic ones. Besides, how many more torii (is that the plural of torus?) facilities do we really need at several billions dollars each?

    --Andrew Grossman
    grossdog@dartmouth.edu
  • A few years ago, you could buy a pulsed neutron generator (model 811-A) from Schlumberger-EMR Photoelectric for about US$100000. (I believe that was the correct price.) It could generate 2x10^8 neutrons per second when operated at 100kV. (Of course the duty cycle isn't a full second.)

    Are these high speed neutrons? How are these neutrons generated?

  • by wayne (1579) <wayne@schlitt.net> on Friday March 26, 1999 @10:20PM (#1960468) Homepage Journal
    How many people would like to see more articles like and less on Linux, the latest OSS flamefest, star wars, katz, etc.? I'm not saying do away with those topics, but geez, if I want the Linux Today, I know where to find it. (On the right hand side of my /. screen, of course. :-)
  • Yeah. MF Physics [mfphysics.com] makes neutron generators using D-D or D-T reactions. Electronic acceleration with high voltages instead of this story's weak laser beam.

    I see that the tabletop experimenters have experience with the big fusion equipment as well, so they do have a good idea what they are doing.

  • by NumberCruncher (19377) on Friday March 26, 1999 @11:06PM (#1960470) Homepage
    Well, I just got back from Atlanta and the meeting about an hour ago. It was great. Stephen Hawking spoke on "The Universe in a Nutshell" and I saw many friends, mentors, and even my thesis advisor running around.

    As a friend would say, it was a "geek fest". I spent the plane ride back with an acquaintance talking about his research. Funny how much interest there is in this stuff... only if there were... ya know... JOBS in it?

    Ok... ok. Most of the stuff talked about would put the most hardy computer geek to sleep. I dont think anyone here cares much about floppy modes of macromolecules, or CCSD calculations, or non-uniform sampling of distributions in Monte Carlo simulations in order to examine rare events (some of the talks I went to). But on the other hand, there were some very cool talks, and a large number of nobel laureates, not to mention some really cool exhibits.

    How does any of this tie into the slashdot effect?

    In a nutshell, think of the slashdot effect (SE) as an avalanche, or a statistical mechanical critical exponent problem. Once a link is posted, it is only a matter of a short time (tau) that this information gets out, and in short order you get a polynomial in tau times something like exp(-t/tau) people following that link. Thus, the target of the link, with a server that is not configured to deal with recognizing the first derivative of this number of people as a function of time, falling over and coughing uncontrollably until it starts doing things like

    dd if=/dev/null of=/dev/hda bs=65536

    Properly set up servers frequently check slashdot for existance of links, so they have measurements of tau, and estimates of the polynomial. With this in hand, they can detect a slashdot avalanche, and quitely disconnect the port...

    Ok, its been a long day, with one canceled flight out of Atlanta...
  • NumberCruncher (landman@mediaone.net) said:
    I dont think anyone here cares much about floppy modes of macromolecules, or CCSD calculations, or non-uniform sampling of distributions in Monte Carlo simulations in order to examine rare events (some of the talks I went to).

    You're right. I'm much more interesting in conformational modes of floppy molecules (as for pharmacophore prediction). And CCSD? I try to stay away from ab initio work and stick with classical molecular dynamics. Regarding the last of your three, we leaned more towards steered umbrella sampling, and the closest thing to Monte Carlo was the Langevin term.

    :)

    think of the slashdot effect (SE) as an avalanche, or a statistical mechanical critical exponent problem.

    I model it more like queuing theory. There is a population of N people checking Slashdot. Different people check /. at different time intervals, which creates a distribution of checking frequencies n(t), most likely with a Poisson distribution.

    I believe most people will follow a link the first time it comes up, though this also has a distribution. (A few people will check a link several times, but the effect is lessened somewhat by caching.)

    Thus, I would expect to see a roughly t*exp(-t) shape to the Slashdot effect, so it should start linear and have an exponential tail.

    As it turns out, there is some data [bnl.gov] to test this theory. Alas, it isn't very good data given the large-ish bin size and the existance of the data in graph form only. It looks like it can be eyeball fit by a Poisson function.

    Still, I don't really see an exponential growth curve as you suggest (though again it's hard to tell) and I don't intuitively feel that your description is correct.

    Ahh, there is a possibility. If I view a link then forward to friends, who forward it to friends, etc, then there should be an S-shaped growth curve. But I only see about a couple percent of the /. articles forward to the different groups and mailing lists I read. (Though extrapolation from one datum is rather imprecise :).

    Still, I assert it's less precise to describe it as a critical exponent problem than as a Poisson distribution.

  • Under the "Fusion vs. Fission" part of the ABCNEWS fusion article (at the bottom), they say "one million millionths of a second"!! Last time I checked, that can be written as "one second".

    It's in the third or fourth paragraph, depending on whether you count the first sentence as a paragraph or not.
  • An AC wrote:
    While there is a fair bit of use for such a fuel, it won't solve the world's energy requirements. As you pointed out, the energy comes from the sun, and there is only so much energy in solar radiation. This isn't to say that it will not be useful, just wanted to point out that the most important thing is still to design stuff that's as efficient as possible and so minimises energy consuption in the first place...

    Re: renewable fuels via biomass. First of all, I think a good deal of energy falls on the earth from the sun, more than enough to power our energy needs. Furthermore, a system whereby we "burned" some distilled crop or peat is environmentally friendly over the long term because the crop growth reabsorbes released carbon-dioxide generated during the burn. Hemp makes an excellent example of a crop which could be both grown in marginal soil and which output is high; several times more than corn. Burning oil, which is basically dead plant matter accumulated into pools over hundreds of millions of years, by its very nature releases all the stored carbon-dioxide accumulated over the eons. We're literally burning ourselves back to the Jurrasic. Or before.

    So, if you agree with this supposition, do you think humanity has much of a choice? I'll take fusion when it arrives, but until then I'd like a sane long term engery generation and consumption policy.
  • At least with modern technology, you probably wouldn't want normal fusion in your household. By the time you've got a good fusion reacton going, your china set has been vaporized. Not a very pleasant experience AT ALL!

    Cold Fusion is the holy grail because instead of heating the apparatus by a few million degrees, it could raise it anywhere (depending on how good the technology is) from 10 to 1000 degrees. That sort of temperature is far more useful for everyday things... not just vaporizing your neighborhood.

    Cold Fusion (called "cold" compared to a nuclear inferno) could be captured in a generator, a heater, a weaponm or just plain used to zap a bird in the oven. But you'd probably want to use it in a generator to power other devices.
  • I feel so incredibly nerdy for understanding 2/3 of what each of you have said =)

    I actually don't have my own intuitive idea of the physical model for Slashdot, but the S-shaped growth curve does exist, in a way, because what Rob & Co do is review submissions and then post them, much like friends forwarding links to friends, and in this way, Rob & Co forward links to their friends, us. Similarly, other news sites and such who frequent /. may also post interesting links, so while we can't rely on a statistical model of individuals forwarding interesting links, I think there may be a connection between sites and organizations doing such things.

    Are you two both bi-chem majors or something?

    Geez. I wonder if this stuff is preventing the majority of /.-ers from replying because they have no clue to what you're talking about =)

    AS
  • Several points and concepts I can think of:
    This definitely points at the fact that a low powered(relatively) setup can *start* the fusion process, while a secondary setup and process would maintain it, whether it be tokamaks or more lasers and such.

    Another point about the efficiency; it needn't truly be able to generate more energy than it uses if some way of tapping into non-useable energy(such as heat or solar) can be used. Imagine a system that is 92% efficient, but if 10% of the energy needed to operate the system could by harnessed by solar collectors in orbit, and we only need to provide 90%, the 2% difference would then be useable by us, with the remainder used to power the system.

    Just a thought

    AS
  • But the researchers feel there is applicable research into generating sustainable fusion reactions. Hot neutrons evidently aren't the only thing; are you arguing that all the cheaper sources you've sited were also sources of fusion? If so, then my arguments are wrong and I apologize. If they were not the products of fusion, then this product/development allows the study of the fusion process on a fairly intimate scale, compared to a tokamak or other more exotic setups of lasers and such

    AS
  • It's similar thinking to a few hundred years ago:
    Wow. So some scientist discovers electrons. Yippee. What is the average agrarian uneducated illiterate peasant going to do with this? What is the average uneducated illiterate noble going to do with this? What a waste of money/effort/time.

    So in 10 years we can figure out a way to apply this towards real sustainable fusion, or table top fission(As another reply to your post mentioned...), or something else totally wacky unthought of (like computers - electrons!)...

    It's research, and its science, which means it doesn't have/need applications. That's what us engineers are for... And I guess complaining about the process is what you're good for? Geez

    AS
  • Anonymous Shepherd (louisjr@cco.caltech.edu) said:
    the S-shaped growth curve does exist, in a way, because what Rob & Co do is review submissions and then post them, much like friends forwarding links to friends, and in this way, Rob & Co forward links to their friends, us.

    To be a good S shaped curve, you and I would have to tell roughly as many friends as Slashdot has readers. I know I don't! So the effect is strongly driven by Rob & Co. and only weakly affected by us. But I don't know how weak "weakly" is.

    other news sites and such who frequent /. may also post interesting links

    If you take a look at the graphs I referenced you'll see some consequence of that effect. Some of the download freqencies overlap. Still, to see real evidence of that you'll likely need to watch some place with a much broader audience, like CNN.com when the US started the attacks.

    Otherwise I suspect that the peak timescale (which seems to be about an hour or two) is smaller than the combination of 1) the time it takes for an article to be rewritten/posted/linked at another news site and 2) the number of different sites people visit in a day. (I can only stay on top of about 4 sites.)

    Are you two both bi-chem majors or something?

    I guess "something." I'm no longer. a student. If you really want to know what I do, you've enough info to web search me and ask direct.

  • I believe they meant a millionth of a millionth of a second or 10^-12 seconds. But I agree that it wasn't totally clear.
  • I missed that one since I was giving my talk in a different session at the same time. Oh well.
  • Someone else mentioned this possibility;
    take a non-critical fissionable mass, and start it on the path to fission with this laser; as long as it produces more power than is necessary to power the laser, we now have a fission reactor that generates its own power, and can't melt down because of a failure in the control process; if the laser shuts down, then the entire system stops fissioning! Instead of huge containment and control systems, a simple fuse and feedback loop to kill the laser if it overworks itself would do the job!

    Yeah, there are always negative consequences to new discoveries and revelations, but imagine if sustainable fission in a room the size of your closet were possible?

    AS
  • Well the whole point of the "football stadium" that is mentioned casually in the article is to break even (i.e. energy out > energy in) with fusion. To my knowledge it hasn't yet been done, that's why the NIF [llnl.gov] (National Ignition Facility) project is under development. It is interesting what can be done on a small tabletop scale, however I'm not really sure what you can practically use it for. On the other hand, the NIF is sorta expensive (1.2 billion), unless you compare it to defense $$. I don't know much about the tokemak approach, LLNL is mostly using lasers [llnl.gov] to try to break even. Interesting stuff.

  • When I just got my ADSL line at home, I stumbled upon the Farnsworth Chronicles [songs.com]. Fascinating story. I stayed up late until 3 in the morning to read about them. Admittedly, this guy didn't receive the credits where credits are due, but I still got the feeling he was no better than the rest. Everyone wants to be the Bill Gates of his time, isn't it?
  • by redhog (15207)
    Isn't either heat or pressure requered for fusion? I.e. cold fusion would requere high pressure? Or what am I missing?
  • I read that wired article as well. IIRC the process requires the palladium electrodes to have particular kinds of holes in them to get the hydrogen to bond to them and fuse.

    It certainly sounds like something was going on there to me. Whether it is useful or not is another matter.
  • Seeing the number of biochemy people reminded me of a good use for this thing, that the other, cheaper neutron source mentioned a bit ago can't do, cause those neutrons aren't fast enough: Neutron Diffraction. I do a little bit with studying Protein+DNA binding, and it could be nice to know which of those dots is water, and which is a sodium ion. Because neutron diffraction needs serious accelorators to perform, not very many complexes have been studied...Mabey this could make neutron studies as common as x-ray diffraction is today.
  • At the very least, they've managed to use a very low powered laser to trigger fusion. Because these fellows have been wrestling with the megawatt fusion lasers, I'm sure they have some interesting engineering ideas for this design. At least they don't have to produce as much output to reach the break-even point.

    With technology this simple (vacuum chamber with laser windows?), perhaps all that's needed is a steel chamber with laser ports...it's easy enough to generate electricity from hot steel.

  • Almost 10 years to the day that Fleishman & Pons announced their little ol' contraption. At least this announcement was at APS... right?
  • The low-powered laser makes the clumps of Deuterium atoms explode. Some of these energetic atoms collide. Some of the collisions happen to cause fusion.

    It's sort of the reverse of the usual laser-initiated design. The most common design involves having the fusion fuel inside a container such as a tiny glass bead. The huge laser blast causes the container and part of fuel to explode, causing a plasma shock wave going both outward and inward. The inward shock wave is what the design uses to actually trap and ignite the fusion fuel.

    This table-top design is actually using an outward-traveling blast. By making many blasts, some of them collide in interesting ways.

  • by Anonymous Coward
    They are 14.1 MeV neutrons from D-T fusion.
  • Posted by AnnoyingMouseCoward:

    *Argh!* This is the third [expletive-deletive] time that I have tried to comment to this posting! Whenever I use the preview button, it trashes my comment!

    *Ahem!*. Anyway, to learn about *real* *cold* *fussion*, check out the muonic hydrogen homepage at

    http://www.triumf.ca/muh/muh.html

    As to all of this "cold fussion", I'm sorry, but get real. Any idiot can induce "cold fussion". Just get a bar of Lithium-6/7 alloy and a neutron detector and wait for a high energy cosmic ray to hit the lithium.

    It would be really nice to think that there are simple ways to produce neutrons, but I'll wait until this has been replicated by other groups before I say nay or yae.
  • Posted by Zyca:

    Next thing you know would be Colts, S&W, Brownings and other gun manufacturers making "Nutron Gun/Rifles"...

    "Perfect for hunting! No need to worry about biting on your own bullets!" :)
  • by joss (1346)
    Linux is a good OS

    Can we move on now

    There is more to a nerds life than that

    For most people an OS is something on which to achieve other things, not an end in itself. Is there a "news for writers" site which is obsessed with the latest and greatest typewriter.

  • >I'm not a physicist, but I know fision is a lot easier than fusion, right?

    Fission is easier than fusion in general, but NOT in deuterium! (Uranium fission is a heck of a lot easier than deuterium fusion, basically because the U nucleus is large and rather unstable in the first place -- hit it with a neutron and it will break apart easy). It's pretty damn hard to just split a deuterium nucleus -- essentially impossible with a laser . Anyway, the neutrons come from fusion, and this is not at all surprising - no need to specifically look for He.
  • Just in passing, Dinorwig isn't really your average hydro-electric plant, it's a pump storage scheme. Off-peak (cheap) electricity is used to pump water from a lower reservoir to a higher one. Then, when there are peaks in demand during the day, the water is released back down to add a chunk of megawattage back into the Grid at a few seconds notice. Very cool place; I was lucky enough to get a guided tour inside before it was finished, many years ago...
  • There is a site collecting articles by Richard Hull explaining how to build a fusor at Jochen Kronjaegers High Voltage Page [uni-marburg.de]. Also Tom Ligon, who wrote the Analog article you mention, produced a supplement [digivill.net] to that article which points out many of the safety issues with building these things.
  • Actually tritium would be produced instead of helium. Interestingly enough, that's what cold fusion scientests claim to have produced. To badd it couldn't be repeated independently :(.
  • So in 10 years we can figure out a way to apply this towards real sustainable fusion, or table top fission(As another reply to your post mentioned...), or something else totally wacky unthought of (like computers - electrons!)...


    This device was developed as a research tool for producing energetic neutrons. It's very useful in that regard, but research on this device doesn't contribute much towards fusion power generation. That's what the other laser that the article mentioned is for :).


    I hadn't thought of using this as a fission trigger, though. That might actually be practical.

  • It seems to me that the efficiency of the device is most likely pretty bad. I dont know for
    sure, but it looks like the clusters would have to be in the laser beam, and even then its random how many of the atoms colide.


    The efficiency of the device is *extremely* bad, mostly because the small clusters don't retain energy long enough to keep fusion going long enough to produce much energy (look up the "Lawson Criterion" for interesting information on this subject).


    The laser delivers about 1000 J of energy over the course of 1 picosecond. The fusion produces about 10,000 neutrons. Making a _very_ rough estimate, let's assume that each reaction producing a neutron liberated a total of 10 MeV. This corresponds to a total energy produced of about 100 GeV, or 1.6e-8 J.


    That puts its energy efficiency at about 0.000000001%, plus or minus a couple of orders of magnitude :).


    To keep enough plasma confined for long enough to produce a useful amount of energy, you need to use larger amounts of deuterium (pellets a few tens of microns across IIRC), and extremely powerful lasers. This is what the other laser facility mentioned in the article is for.


    There are at least two other ways to produce fusion relatively economically; we'll see which is finally adopted for power production some time within the next 50 years or so.

  • This definitely points at the fact that a low powered(relatively) setup can *start* the fusion process, while a secondary setup and process would maintain it, whether it be tokamaks or more lasers and such.


    An interesting idea, but it turns out that this isn't necessary. All three of the styles of fusion reactor design that I know of have no problem triggering fusion. The difficulty is in keeping the plasma concentrated enough and hot enough for fusion to be sustained for a useful length of time.


    For reference, the three styles that I know of are laser-induced fusion, magnetic confinement fusion, and a rather nifty scheme involving heating and confinement via extremely intense x-ray radiation produced by incandescent plasma.


    Another point about the efficiency; it needn't truly be able to generate more energy than it uses if some way of tapping into non-useable energy(such as heat or solar) can be used. Imagine a system that is 92% efficient, but if 10% of the energy needed to operate the system could by harnessed by solar collectors in orbit, and we only need to provide 90%, the 2% difference would then be useable by us, with the remainder used to power the system.


    I'm not sure that I follow your logic here; IMO, we'd be better off using the 10% from the solar satellites directly as opposed to the 2% surplus that we'd acheive from such a scheme. Also, there is the more significant problem of efficiency being closer to a billionth of a percent.


    Bringing the efficiency up seems to require very large devices, though these are still buildable.

  • moment imagine a world where a photosynthesis reaction provides the decomposition of water to its base elements, hydrogen and oxygen. These may then be re-combined in an exothermal reaction to provide heat.


    IMO, it would be easier and just as useful to just crow appropriate crops and ferment them to produce methanol. Methanol burns almost as cleanly as hydrogen, is easier to store and transport, and can be used in appropriately designed internal combustion engines.


    The main problem with methanol is that it can corrode metal engines at high temperatures, but I hear that good progress is being made re. ceramic engines, which are much more resistant to chemical attack (and are lighter to boot).


    You don't have to worry about people drinking the methanol. Ethanol is drinkable; methanol is poisonous.


    However, as another poster pointed out, your power production is still limited to the amount of power received by the earth from the sun in this scheme.

  • In other words, small scale fusion reactors already exist, so why is this one special, other than being novel for using a laser for acceleration instead of an high-voltage electric field?


    Because it's cheap, if I understand correctly :).


    Also, they've been using a similar (though less powerful) laser at the University of Toronto for energy absorption studies to assist laser fusion research, so there is some additional tangential benefit. I'm curious as to whether duterium microclusters might absorb energy more efficiently than the pellets used in most laser fusion schemes. Just a thought.

  • Here's why you should not be happy about this story. This device doesn't produce useful fusion energy, but it does produce hot neutrons, and it does so cheaply. What good are hot neutrons? They can be used to transmute non-fissionable isotopes of into fissionable isotopes.


    Fissionable isotopes are rare. Denying third-world bohemian have-nots access to fissionable isotopes is the linchpin of our nuclear non-proliferation strategy.


    Then I'm afraid you'll have to find an alternate strategy. As another poster pointed out, you can produce copious quantities of hot neutrons quite cheaply by firing a deuteron beam into a lithium target. Anyone who's taken high-school physics can infer this if they're reasonably bright. Unless you intend to burn all physics textbooks, your have-nots will be perfectly capable of building their own devices regardless of whether they can buy yours or not.


    A similar argument applies to strong encryption techniques.

  • three styles I know of

    You left out gravitational confinement.

    Of course, that requires a ball of hydrogen about a million miles in diameter, and shielding is a bit tricky unless you're about 93 million miles away...
  • Someone else mentioned this possibility;
    take a non-critical fissionable mass, and start it on the path to fission with this laser; as long as it produces more power than is necessary to power the laser, we now have a fission reactor that generates its own power, and can't melt down because of a failure in the control process; if the laser shuts down, then the entire system stops fissioning! Instead of huge containment and control systems, a simple fuse and feedback loop to kill the laser if it overworks itself would do the job!


    Yeah, there are always negative consequences to new discoveries and revelations, but imagine if sustainable fission in a room the size of your closet were possible?


    There are a couple of difficulties with this. First of all, while you will get a short chain reaction starting, it will be _pretty_ short - unless you're using a sample that's _just_ shy of critical mass, I don't think you'll get more than a factor of ten magnification of your energy input. This sounds good, until you realize that most neutron production schemes are abysmally inefficient (millions-to-one inefficient or worse). If you try to increase the magnification factor by using a barely-subcritical mass, you have the problem of someone sneezing and its geometry changing to be within the critical envelope (or the original builder adding a milligram too much material).


    However, there's a bigger problem with closet-sized fusion reactors - radiation. A conventional fission plant has several metres of concrete between the reactor core and anything else. This isn't because of the amount of radiation produced, but because of its penetration distance. Gamma rays can go a very long way through solid material before being stopped. A closet-sized fission reactor would slowly kill everyone on the block.


    There are also issues of the size of the steam turbines and the multiple layers of isolation that prevent a reactor from easily leaking radioactive material, but I'll leave those for now.


    So, a neat idea, but a bit dangerous to implement in practice :).


    Heck, if you had weapons-grade U235 and weren't worrying about radiation, you could build a fission-powered steam generator the size of a breadbox without needing a neutron source.

  • Actually tritium would be produced instead of helium.


    No, they're producing helium-3. D + D -> He3 + n. Other fusion chains may produce tritium, but this is claimed to be the dominant one.

  • Anyone who's taken high-school physics can infer this if they're reasonably bright.

    Yup. So can physics, chemistry, or engineering majors. I think that one of the great failures in limiting nuclear proliferation has been permitting foreign nationals to attend US colleges and uiniversities. It makes all the sense in the world to me for the US to open its borders and permit people of all nations to renounce their native citizenship, live in the US, become US citiznes, and learn all they want to. It strikes me as the height of insanity to train foreign nationals in fields which would permit their national governments to conduct a nuclear war against us.

  • Aha... I think I know you :-)

    Actually it would be interesting to model the /. effect, and present a paper somewhere :-)

    The floppy macromolecule talk was Leslie Kuhn, Mike Thorpe, and a post-doc whos name eludes me at this moment. It was interesting, though not specifically set up for pharmacore identification. It was more in line to examine the action of HIV protiease, and the actual physics of its actions. I thought the analysis was quite striking in terms of being able to determine which parts of the molecule act as rigid bodies, and which parts are flexible. Kind of a mechanical version of SAR. Using this information, they are looking for new methods of attacking/disabling the protiease by enhancing or decreasing flexibility in various regions. I do not know if this has more general pharmacophore applicability, but it is a neat idea.

    As for ab initio and other fun things, these guys are trying to convince me that I need to jettison DFT in favor of CCS{D,DT,DTQ,...} in order to get better energetics for my MD codes... Unfortunately an additional seven orders of magnitude in algorithm time doesnt appeal to me. I like to study things with many thousands of basis functions, and something of order 10**30 ((10**3)**10) is kinda hard to calculate ... quickly.

    If you want to continue this discussion outside this forum, email me at landman@sgi.com.

    Joe
  • When I type quickly, I cannot seem to spell pharmacophore. Oh well..

    Actually, my model (guessed at from the concepts I mentioned) is basically a polynomial times a decaying exponential. No exponential growth here, just ordinary impulse and decay. The critical exponents are features of the statistics, and allow you to avoid talking about nested distributions.

    I was unaware of that paper. I agree that the binning is unfortunate.

    Joe
  • "Anyone who's taken high-school physics can infer this if they're reasonably bright."


    Yup. So can physics, chemistry, or engineering majors. I think that one of the great failures in limiting nuclear proliferation has been permitting foreign nationals to attend US colleges and uiniversities. It makes all the sense in the world to me for the US to open its borders and permit people of all nations to renounce their native citizenship, live in the US, become US citiznes, and learn all they want to. It strikes me as the height of insanity to train foreign nationals in fields which would permit their national governments to conduct a nuclear war against us.


    I sincerely hope that you're being sarcastic.


    Firstly, the idea of restricting knowledge sufficiently that nobody in a target nation can figure out how to build nuclear weapons is extremely disturbing. It simply _isn't_that_hard_. You would literally have to restrict everything down to basic physics texts, which seriously hampers the ability of the target nation to perform R&D in any modern industries. Is this a tolerable goal? IMO, *no*.


    Secondly, it is physically impossible to restrict knowledge to the required extent. Take a look at the "anarchy" text files that were endemic in the BBS world ten years ago. Any country with a communications network of any reasonable efficiency can distribute information more quickly than it can be destroyed. All it would take is one person smuggling in a high school physics textbook - or one person to download a semi-accurate "how to build a nuke" text from the 'net - to make all of your effort worthless. Should you then destroy the communications network also? IMO, this isn't tolerable either.


    So, in order to forcefully prevent countries that you don't like from learning _how_ to develop nuclear weapons, you would have to destroy both their industrial base and their communications network, and leave them locked at an early 1900s technology level. This doesn't sound justifiable to me. I was under the impression that the US supported freedom for everyone, not just themselves.


    There are other alternatives. IMO, a combination of all of them would be the most effective approach:

    • Develop a good "nuclear umbrella".

      Mutually assured destruction was a wonderful deterrent to nuclear war. The cold war actually _ended_, because both sides realized that they'd really rather not fight.

    • Aim your policies at catching people who produce useful amounts of weapons-grade material.

      Producing enough plutonium for a nuclear weapons program takes a nuclear reactor. These put out enough gamma radiation that you can detect them from space without any difficulty, even if they're shielded. The US already has a network of satellites that does this, if I understand correctly. This network also detects any nuclear tests that are performed.

      A terrorist organization could try producing enough material in their basement for one bomb, by any of several methods, but that too can be detected if you put up an umbrella of improved satellites, or overfly suspicious locations with planes carrying radiation detectors.

    • Promote education, democracy, and peace.

      It's counterproductive to nuke someone. You just don't get a net benefit. Tyrranical leaders might not be concerned with this, but elected leaders are answerable to the people. Education allows industry to flourish, which gives the working class more money. More money in the hands of the working class means more personal freedom, and luxuries like communications networks that allow new ideas to filter in. These set the stage for governmental reform, which leads to checks on the leaders' power, even more freedom among the populace, and economic ties to the rest of the world, making nuclear war even less attractive.


    So, in summary, I think that there is a better approach than the unfair one that you propose.

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