Table Top Fusion Courtesy of Tiny Bubbles 326
Erik Baard writes: "The peer-reviewed journal Science is carrying a cover story about the possibility of table top fusion. Not cold fusion, mind you, but the apparatus might look that way to some. Oak Ridge and other labs say they have gotten the fingerprints of fusion (neutron production) from collapsing bubbles in liquid, a process that heats a local area to temperatures as hot as the surface of the sun, and releases photons.
The disputes are already here -- notably from Dr. Robert Park of the American Physical Society and from critical reviewers who say they haven't repeated the neutron production. But the authors say the critics didn't calibrate their equipment correctly. Articles regarding the discovery can be found on
Eureka Alert " CD: Looks legit, but Pons and Fleishman (and the University of Utah for that matter) talked a good game. I suppose I'll belive in tabletop fusion when a generator comes atached to my next laptop. The author of this post also has a longer article up at the Village Voice
April First comes early? (Score:3, Funny)
Re:April First comes early? (Score:2, Funny)
Re:April First comes early? (Score:2)
Perhaps they need a month to iron out the bugs?
Quote from the man (Score:5, Funny)
Back to the Future (Score:2, Funny)
hopefully they'll come out with a clear casemod for it. . .
Bottled Fusion (Score:4, Funny)
RD
Not likely (Score:4, Informative)
Re:Not likely (Score:2, Interesting)
More here: http://villagevoice.com/issues/0210/baard.php
Re:Not likely (Score:5, Informative)
You'll notice the journal and/or the authors have announced the results to the media ahead of the print version being available too.
It's not like a TV station scooping a daily paper out of a story they researched or something like that.
BTW, I wouldn't consider him a professional nay-sayer, but rather skeptical, analytical (both good qualities in a scientist) and out spoken (which can be good or bad).
Re:Not likely (Score:4, Insightful)
> nay-sayer, but rather skeptical, analytical (both
> good qualities in a scientist) and out spoken
> (which can be good or bad)
Skepticism can easily exceed the bounds of
intellectual honesty. When such an excess
becomes ingrained and habitual, self-justifying
delusion sets in.
Analysis of the unknown is folly. That's why
the scientific method consists of the creative
generation of hypothesis, which is then confirmed
or disconfirmed by experimentation.
The bottom line in science is not analysis,
or orthodox dogma, or arguments from authority,
but the cold, hard facts of experimental evidence,
and the delusive skepticism of ideologues such as
Park pollute the public mind, as witness the
ignorant comments in this slashdot article, or
worse yet create in credulous factions of the
public a reactionary embrace of the entire range
of heterodox opinion, rather than just those
elements contrary to orthodoxy which are
well-attested by observation.
Re:Not likely (Score:2)
Re:Not likely (Score:2)
A true skeptic witholds belief in either side until the evidence it genuinely convincing, and is never totally convinced. A few people not associated with the original experiment failing to get the same results doesn't qualify. Even the original experimenters being unable to consistently get the described result doesn't qualify. It may merely mean that they were wrong about the required conditions. (Consider the early attempts to create transistors. As I remember, failure rate was at well over 99% for many years.)
And a true skeptic remains not totally certain about matters even when they become conventional wisdom. This tends to make them poor at arguing their case. Pity.
But calling someone a skeptic because he is dogmatic, respected, and noisy is misuse of the language. He is probably quite good at his specialty, and may even qualify as a skeptic in some areas. But citing mass publis opinion is evidence that the citer doesn't qualify as a skeptic in this area.
.
Re:Not likely (Score:2, Informative)
Under Pressure (Score:2)
The fact of the matter is the "academics" who originally wrote an article and did the little experiment had an enourmous burden of proof. They knew this at the outset. To claim that at temperatures as hot as the sun, and tiny bubbles were enough to provide the enourmous pressures needed for fusion is the very definition of increadible. Frankly, they should have been VERY suspicious of their own results. Skepticism isn't something that should have even HAD to have come from outside their project.
At least they'll have the comfort of knowing that networks will probably not pick up the story, credibility being in such short supply. Except for Fox News, they appearently don't have the exacting standards The Weekly World News insists on.
Re:Not likely (Score:2)
In the original "cold fusion" fiasco, there was a lot of misinformation or missing details about experimental apparatus. Only with a lot of work did it become clear that the experiment could not be duplicated.
Bubble fusion is not as far fetched as electrochemical fusion. Sonoluminescence is not well understood and there may very well be high enough temperatures to cause an occasional fusion reaction. After all, you can get plenty of fusion in a vacuum tube with only 150eV of potential... and that ain't much (basically, it's house voltage).
One suspicious thing, however, is the preloading of the bubbles from a neutron generator. I haven't read the paper, but I am at a loss for what effect that might have in terms of enhancing fusion.
Re:Not likely (Score:2, Informative)
Second, you speak of 150 eV (electron volts, to the uninformed) as being "house voltage". Electron volts measure energy, not potential (specifically, the amount of energy gained by an electron when going through one volt of potential) In the English system, it would be equivalent to 2.7778*10^-4 watt-hours. Second, an electron volt is not even on the scale of anything related to your house's electrical system, which delivers many kilowatt-hours, meaning that if one eV=1.602*10^-19 J and one watt-hour equals the amount quoted above, an electron volt would give about 4.45*10^-26 kilowatt hours, while a typical home would use many KWH per month. A large particle accelerator would put billions of electron volts into a single particle to get it up to speed. Quite simply, your comment (or at least the third paragraph) is full of bullshi^H^H^H^H^H^H^Hcattle excrement.
Re:Not likely (Score:4, Informative)
The fusion reactions commonly used are D-D (deuterium-deuterium) and D-T (deuterium-tritium). Deuterium ions can be boiled off a hot filament and electrically accelerated into a target that has been impregnated with deuterium and/or tritium.
See this page [mfphysics.com].
Re:Not likely (Score:2)
Second, you are partly right. (my Bad).. it isn't 150eV unless the tube is accelerating electrons (in which case, they get 150 eV of energy crossing 150V of potential). But let us not get too confused... of course voltage energy - it is potential energy (like gravitational potential energy or any other kind of field potential energy).
Re:Not likely (Score:2)
Chances are that this will turn out to be a dud. However the real tragedy of the F&P affair is that it poisoned the field for other researchers who were working in good faith and did not consider the NYT a suitable place for the first publication of their results.
Plenty of science papers turn out to be junk. It is a good thing if Science makes the effort to actually acknowledge that small scale fusion does not have to be equated with junk science.
After all the response to Harrison's chronometers by Newton and co was pretty negative. They could not imagine that any timepiece smaller than the solar system could be accurate. Today I have a mechanical contraption on my wrist that is more accurate than most quartz watches and certainly gives a better longitude fix than any observer of the moons of jupiter.
Yes, likely; cold fusion is REAL, says the US Navy (Score:3, Interesting)
What really gets my goat is that the editors of Slashdot are apparently unaware of the position of the U.S. Navy's Naval Ocean Systems Center in favor of cold fusion, and their long-suffering and pioneering work on the particular kind known as codeposition fusion:
http://www.spawar.navy.mil/sti/publications/pubs/t r/1696/tr1696.pdf
[navy.mil]
I have copied that tech report, along with a diagram you can use to do cold fusion on your desktop for less than US$500, in this directory:
http://www.bovik.org/codeposition [bovik.org]
Please mod me up; I am posting as AC due to time pressures and a different browser in use at the moment. Thanks in advance.
Sincerely,
James Salsman
james at bovik dot org
Re:Not likely (Score:5, Insightful)
I'm no scientist, and I've never researched the issues involved, so I'm certainly not proposing to pass judgement on whether this (extraordinary) claim has any likelihood of being justified, or whether Dr. Park's quoted reasoning is sound. But I will say that Dr. Park's eagerness not only to reject the possibility as quickly as possible but to quickly silence those who entertain the possibility through mockery as fast as possible cannot inspire confidence about his judgement.
Dr. Park and his ilk work to make a pariah of any scientist who gives any credence to an extraordinary claim which is subsequently proven false (or is considered to have been proven false, or in fact why bother waiting for proof at all?) The resulting social impulses to avoid exclusion and join in pelting the menacing sinner are what make this a powerful means of winning arguments. "Hark: A COLLECTIVE GROAN CAN BE HEARD . Better join in the groans fast before anyone starts looking your way!"
But for Heaven's sake, if we accept that the normal process of review will be able to effectively determine whether these results are sound or not, then the absolute worst that can happen is that some time and money will be spent in finding that the results are not sound, and that some people will thus be proven wrong. In science people are proven wrong, through the expenditure of some time and expense, all the damn time! Being willing to consider new ideas necessarily entails the risk that you will consider, or take seriously, ideas that turn out to be false. If you're terrified of ever believing something that turns out to be wrong, don't do scientific research. The exact same standard should hold for extraordinary claims as for more mundane ones: if they have some prima face credibility, let them join the rough-and-tumble of review. Extraordinary claims do merit searching, skeptical examination: those who make or consider them surely don't deserve any more or less odium than scientists who turn out to have been fraudulent, or foolish, or just mistaken in regard to more mundane ones.
Oh, and for all you freshly minted M.Sc.s and docs out there who are saddling up to join the posse and defend the faith in this forum: consider first that in all academic fields it tends to be the young postgrads who are loudest and most confident in defending the current thinking. Older academics are (on average, of course) a little less sure of themselves: could it possibly be that they have learned something?
Re:Not likely (Score:2, Insightful)
Re:Not likely (Score:3, Insightful)
I'm not sure what a 'scientist' really is anymore... but I think I play one on weekdays (and particularly productive weekends).
>Dr. Park and his ilk work to make a pariah of any scientist who gives any credence
This is the nature of scientific research. The more outlandish your claim, the greater the feeding frenzy will be if/when you are proven wrong. Of course, if your results hold up... you might get a Nobel Prize (or even a Fields Medal!).
This isn't necessarily a bad thing. In fact, a good scientist is always skeptical... they want to know *all* the details and be thoroughly convinced before accepting a new result. This is healthy and, in my opinion, good for science.
On the other hand, if skepticism is taken too far, it becomes dogma. Dogmatic faith is the antithesis of good science.
Now, I'm in absolutely no position to pass judgement on Dr. Park (I believe I fall into your "young postgrads" category) but personally I could never see myself interjecting a personal opinion of this sort in a scientific context.
If one has an issue with the facts presented in a paper, one takes up those issues explicitly. Innuendo about 'groaning', etc. seems unprofessional and out of place to me. To Dr. Park's credit he *does* make some very good points; most specifically that other respected scientists in the field have been unable to duplicate the results. This is very significant and valid criticism.
In the end, I think the situation is summed up very well by a quote I heard on a TV show once (I think it was 'Law & Order'):
"Scientists have a star system that make Hollywood look like a socialist love-in".
The comment offended me at the time.. but objectively speaking, there is a lot of truth in it.
Re:Not likely (Score:2, Insightful)
Not so. The worst that can happen is that a lot of time and money will be spent in finding that the results are not sound. Meanwhile people less familiar with the scientific process will see the special on Dateline saying the energy revolution is here, and believe it.
I don't feel qualified to say much about the merits of this particular experiment, but I did just get finished reading Park's Voodo Science (and so, you know, I'm an expert). In it he discusses many ways that the label "science" had been attached to products and experiments that end up tricking people. One example he uses in his book is the fear people have had that power lines cause cancer. After around 20 years of research, no statistically relevant connection has been found. Hundreds of millions of dollars and huge amounts of time and energy spent by people, activists in an uproar, etc.
Park might have a bit of a tendency to be condescending or quick to jump to conclusions, but he seems to have a lot of experience and maybe he sounds jaded for a reason. I'm convinced his basic point is sound: the scientific community and it's accepted methods are effective and exist for a reason. Bad things can happen when the accepted procedures of peer review aren't adhered to.
Re:Not likely (Score:2, Insightful)
It was submitted for review to Science. Science is, after all, a scientific journal. It was submitted by Science for review to a number of scientests. They looked at the results and recommended against publishing it.
Let's go over that again. Paper submitted for review. Paper reviewed. Paper rejected.
Now, move foward to the present, and the paper not only is getting published, it is going on the front page of the magazine.
It would be one thing to just present theoretical data that might need work, this IS done all the time. But they are presenting experimental data which absolutely should be reproducable. There is no way around it. Thier data FAILED initial review. It will get many more chances to be reviewed, and perhaps they will get together and calibrate the instruments properly and get this all sorted out.
Right now it is not fit for publication, except as a theory.
Park was more critical of Science in his little blurb than the actual study, and rightly so.
Re:Not likely (Score:2)
Or only the established ones can dare afford to challenge the orthodoxy... even if they many realize its bogus.
Re:Not likely (Score:2, Interesting)
Only up to a point - a 31 year old researcher may be in a better position to question the orthodox theory than a 21 year old one, but he's also far more likely to do so than the average 61 year old professor. New and radical theories tend to finally win out when the younger researchers become the senior lecturers and the supporters of the old one retire.
apply this before posting these physics stories (Score:5, Funny)
A simple method for rating potentially revolutionary contributions to physics.
-5 point starting credit.
1 point for every statement that is widely agreed on to be false.
2 points for every statement that is clearly vacuous.
3 points for every statement that is logically inconsistent.
5 points for each such statement that is adhered to despite careful correction.
5 points for using a thought experiment that contradicts the results of a widely accepted real experiment.
5 points for each word in all capital letters (except for those with defective keyboards).
5 points for each mention of "Einstien", "Hawkins" or "Feynmann".
10 points for each claim that quantum mechanics is fundamentally misguided (without good evidence).
10 points for pointing out that you have gone to school, as if this were evidence of sanity.
10 points for beginning the description of your theory by saying how long you have been working on it.
10 points for mailing your theory to someone you don't know personally and asking them not to tell anyone else about it, for fear that your ideas will be stolen.
10 points for offering prize money to anyone who proves and/or finds any flaws in your theory.
10 points for each statement along the lines of "I'm not good at math, but my theory is conceptually right, so all I need is for someone to express it in terms of equations".
10 points for arguing that a current well-established theory is "only a theory", as if this were somehow a point against it.
10 points for arguing that while a current well-established theory predicts phenomena correctly, it doesn't explain "why" they occur, or fails to provide a "mechanism".
10 points for each favorable comparison of yourself to Einstein, or claim that special or general relativity are fundamentally misguided (without good evidence).
10 points for claiming that your work is on the cutting edge of a "paradigm shift".
20 points for suggesting that you deserve a Nobel prize.
20 points for each favorable comparison of yourself to Newton or claim that classical mechanics is fundamentally misguided (without good evidence).
20 points for every use of science fiction works or myths as if they were fact.
20 points for defending yourself by bringing up (real or imagined) ridicule accorded to your past theories.
20 points for each use of the phrase "hidebound reactionary".
20 points for each use of the phrase "self-appointed defender of the orthodoxy".
30 points for suggesting that a famous figure secretly disbelieved in a theory which he or she publicly supported. (E.g., that Feynman was a closet opponent of special relativity, as deduced by reading between the lines in his freshman physics textbooks.)
30 points for suggesting that Einstein, in his later years, was groping his way towards the ideas you now advocate.
30 points for claiming that your theories were developed by an extraterrestrial civilization (without good evidence).
40 points for comparing those who argue against your ideas to Nazis, stormtroopers, or brownshirts.
40 points for claiming that the "scientific establishment" is engaged in a "conspiracy" to prevent your work from gaining its well-deserved fame, or suchlike.
40 points for comparing yourself to Galileo, suggesting that a modern-day Inquisition is hard at work on your case, and so on.
40 points for claiming that when your theory is finally appreciated, present-day science will be seen for the sham it truly is. (30 more points for fantasizing about show trials in which scientists who mocked your theories will be forced to recant.)
50 points for claiming you have a revolutionary theory but giving no concrete testable predictions.
You forgot... (Score:4, Funny)
Warning: Do not fuse your dog to anything. If you do decide to fuse a cat, use a strong superglue or firm adhesive to ensure they don't escape and claw your head off. Because it doesn't take Einstein to tell you, Cats = Evil^2.
Re:apply this before posting these physics stories (Score:3, Interesting)
I'm concerned that it hasn't been duplicated yet, but hopeful.
Re:apply this before posting these physics stories (Score:2, Interesting)
"When a distinguished elder scientist states something is impossible, he is almost always wrong."
-Arthur C. Clarke
Yet one more. (Score:2)
100 points more for getting Village Voice Slashdotted at the same time.
I'm patient, really I am. I have a friend who told me a couple of years ago that he sees the future in his dreams. I'd like him to prove it and suggested methods to do so. One day, he will supprise me. It will come before somnambulist fusion.
Re:apply this before posting these physics stories (Score:2)
How many points for stating that your theories were revealed to you directly from God? I'm not making this up, I heard it just today.
-Rob
Sause for the goose, sauce for the gander. (Score:2)
Re:apply this before posting these physics stories (Score:2)
I seem to recall... (Score:3, Funny)
If you don't get a lot of those pesky neturons, it'd be fun to tinker with one of these in the garage. What's deuterium go for these days?
MMMmm Sonoluminescence (Score:5, Informative)
Sonoluminescence: an Introduction [llnl.gov]
Single Bubble Sonoluminescence HOWTO [physik3.gwdg.de]
Since sonoluminescence dosent seem to scale up (to my knowledge) this seems like a moot point. It is sort of cool to have a cheap way to study micro-fusion though.
Re:MMMmm Sonoluminescence (Score:5, Interesting)
The big pain of it is the bubbles are so small its extremely hard to make measurenents. Back in 98 when I did my experiment it wasnt even clear in the literature if the light was black body nor what temperature the radiation source was. The water surrounding the bubble has a cut off in the ultra violet and the peak frequency in the emitted light was not observable. I think we found some rather crude theories of shock wave development to would explain some ionization..but i dont think the theories made any estimates of temperatures rivaling that needed for a useful fusion cross section...but of course I didn't know much plasma physics then...it would be interesting to model this in the way ICF target implosion is modeled
If its fusion...I can't imagine this be an extremely useful power source...the bubbles are so small and short lived...if extractable power were produceable I'd imagine the power would heat the sorrounding liquid to the point that the gas dynamics driving the bubble formation would break down well before you could extract any useful heat load from the bulk volume.
Even it its not fusion temperatures in the bubble...its still a very interesting effect....pico sized oven for chemical reactions. Nanotube technology is big now...a pico sized high temp reaction chamber might be very useful for nanotech. My parter and I had a whole shopping list of crude measurements we wanted to try making . Looking for some assymetries in the radiation pattern was the one we really wanted to do.
-jef
Re:MMMmm Sonoluminescence (Score:2, Interesting)
Since most of the web pages I have seen are either basic (it is a bubble, it makes light, try it) or has information that seems to be full of errors and typos. I have found a quite a few papers on environment modifications resulting changes in output but am at a loss for hard data. the best site that I have found is one by Sci. Am. and I think most people here already that half there stuff is crap (they cant tell the diffrence between F and K SciAm:Ask the experts:Phy [sciam.com]
And since I am still in HS I dont have a chance in hell of getting access to a decent library (or online access to nature/science/ojps/etc...). Oh well its only another month or two.
Re:MMMmm Sonoluminescence (Score:2, Funny)
Nanotube technology is big now
logically inconsistent! 3 points!
Downloadable copies of the articles (Score:5, Informative)
Cold fusion was BS (Score:2, Insightful)
I believe that anything related to tabletop fusion coming from Pons and Fleischmann should be treated with the highest circumspection, bearing in mind that those two might have an agenda. I doubt very much top-class scientists around the world would have been trying to build Tokamaks at the cost of billions of dollars, and been through so much frustration with them, if it was even remotely possible to do fusion with a pyrex full of deuterium and a paladium electrode in a second grade lab in Utah.
So, even though there is an infinitesimal chance that P. and F. have stumbled on something legit and promising, there a much greater chance that they're crooked scientists, and an even greater chance that they're just plain crackpots.
Re:Cold fusion was BS (Score:4, Insightful)
Re:Cold fusion was BS (Score:4, Informative)
Some facts in the case
1) They used heavy water (D_2O) in their experiments. Steven Koonin, a theoretical nuclear physicist, confronted them at a conference with a simple question : Had they done the simple test of using ordinary water? (Which wouldn't have produced fusion.) The answer was damning : No, they hadn't even thought of it.
2) Their work detecting neutrons (a certain biproduct of fusion, cold or not) from their experiment was presented in a most misleading fashion at conferences. They displayed figures without labels, and did not perform proper calibrations of their detection -- it was impossible to determine whether their "signals" were simply background. (Of course, their detections were orders of magnitude too small -- had the signal been commensurate with the heat produced, they would have been dead from the radioactivity.)
3) Moreover, when confronted with the the fact that their "signals" lacked a crucial feature known as the "Compton edge" (as any physics major has observed this in their labs classes) which must accompany any real signal, they further lopped off their plots so as to show only the spurious peak, making it impossible to realize that they were lacking the Compton edge.
4) They presented their research to the press prior to publication. This turned the scientific process into a media circus, impeding progress, and doing immense damage to the public conception of the scientfic process.
5) Rather than openly describing their methodology (a standard practice in any scientific discipline) to allow other researchers to reproduce their work, they kept their methods secret. I recall several groups were forced to set up their experiments using bits of video footage from the evening news.
6) Later claims by a number of researchers that some extraneous heat was being produced is quite a distinct issue from the original work of Pons and Fleischman. Pons and Fleischman's original claims were much bolder -- they claimed a very large extraneous heat output. It was later determined that they had simply done their calorimetry accounting wrong (a common error in calorimetry, but nonetheless surprising, because they were experts in calorimetry).
In sum, the way Pons and Fleischman conducted their work on cold fusion was a prime example of how science is not to be done. The image of Pons and Fleischman as two revolutionary figures taking on the physics establishment is simply not commensurate with the facts of the case -- they practiced very poor science, by the standards of any scientific discipline.
Bob
Re:Cold fusion was BS (Score:2, Insightful)
In other words, these folks have just reproduced results in a different medium for CF (no, it isn't cold, even in the original P&F studies - cold is a relative term). And they've corroborated results put forth by more reliable CF studies done after the original failures. Lastly, the same critics so quick to dismiss CF are using the same arguments with the same amount of diligence as last time (hint - if you can't get it to work, see the original authors to work out problems)
In all likelihood, P&F were on to something - they just failed to do the appropriate research before announcing their discovery. They failed to do several control tests, mostly involving differing control materials; they also failed to ensure reproducibility.
And, for their efforts, the establishment scientific community ridiculed them rather than actually visiting to see what they had found. Better to keep their own jobs.
--
What drivel! (Score:2)
I was at the Supercomputer Computations Research Institute at FSU during the P & F cold fusion period. This institute was heavy on physicist. We had nuclear physicists, high-energy physicists, string theorists, physicists working on QCD, spin systems up the wazoo, and incestuous connections with CERN and Fermilab.
Of all of those people, at first, every single one wanted cold fusion to be true.
Let me repeat that for jelly-brained Kuhn addicts: Every. Single. Physicist.
It was one of the most exciting times at the Institute. Every week we had "brown bag lunches" where some researcher from somewhere gave an informal lecture on some possibility for the mechanism.
It was only after various groups withdrew their early claims of replication, when the details didn't come, and after the fateful exposition of the calorimetry problems that physicists, in some cases almost reluctantly, concluded that it was a tempest in a teapot.
The so-called snubbing of "upstart chemists" by a physics priesthood never happened. At all. Even remotely. In spite of the fact that chemists and physicists hate each others' guts, it never happened and was entirely made up after the fact by people with sociological leanings who were not in the thick of things.
Re:Cold fusion was BS (Score:2)
You say first:
it was at best bad science ... to get funds or to serve some industry's interests.
Then you say:
top-class scientists around the world would have been trying to build Tokamaks at the cost of billions of dollars
How much grant money is in building a Tokamak? Billions, according to you. How much in sonoluminescence? Easily two or three orders of magnitude less. If I were to pull a big, evil corporate scam, I'd be in the Tokamak business, not the shady science business.
Here's my neck, aim ax at dotted line... (Score:3, Funny)
Q: What does a neutrino detector actually detect?
A: The presence of funding.
Theorists were convinced that neutrinos would be observed jumping from tau to mu versions
Or am I just a clever troll?
Re:Here's my neck, aim ax at dotted line... (Score:2)
There are some more exotic, interesting experiments too like AMANDA [berkeley.edu] which uses antarctic ice for neutrinos to interact with, rather than piles of iron.
Yes, the technology to get to 10,000,000 Kelvin. Plasma physicists have been working on it for a long time. Ummm...what? You ain't gonna get a metal to 10M Kelvin. What metal is that exactly? The experiment described takes place in bubbles of gas suspended in a liquid medium. High temp superconductors are having their problems because there is no good theory to explain how they work. So instead people try random things, and some of them work. Because 10M Kelvin isn't "cold", and we have a good theory to explain fusion. We've fused things lots of times (A hydrogen bomb is a fusion device -- and like it or not, we tested many of them). We also smash protons, deuterons, and now even gold atoms (RHIC) at temperatures going far, far higher than the temperatures required for fusion. We think we understand what protons/neutrons/atoms are made of and how they interact, and we can predict with accuracy how to make them fuse.-- Bob
You've got neutrons and neutrinos mixed up (Score:2, Informative)
but we look for fast (Mev) neutron production to verify fusion, since they're much easier to detect.
this test was what fail F&P as well, BTW.
Re:Here's my neck, aim ax at dotted line... (Score:2, Informative)
The Pons and Fleischmann experiment, if it had actually worked as well as they said it did, would have killed them [washington.edu] from the neutron radiation. They didn't bother to do even the most basic accounting of what was going where and when, and they never compared what they measured to what they would have expected to see had they actually produced fusion. Worse, they hid details from their experiment for a considerable period of time, before saying "Wait, you weren't doing it right!" and giving the details of their palladium electrodes when the evidence was mounting against them.
The current experiment, even if it is wrong, at least was performed by experimenters who appear to understand the importance of collecting as much information as possible before hypothesizing models that explain it. The trouble with reproducibility might indicate a problem with their instrument calibration, plus the measured neutron flux and the detected tritium are in disagreement on how much fusion is taking place. However, at least the experimenters acknowledge this, and give a detailed enough description of their setup that others can try to reproduce it. It probably won't pan out, but I won't hold it against them.
sounds like a movie (Score:2)
Who is getting their physics PHD's from the university of Hollywood?
Friends of mine have been working on this (Score:2, Informative)
People I respect have been working on this using deuterium. Stainless steel cell, palladium side with the ultrasound attached to it.
Very repeatable response: clean relationships between ultrasound energy, neutrons and helium.
I have thought 'cold fusion' was real from the beginning. It is very normal for scientific breakthroughs to take a long time to reliably replicate: The early work with semi-conductors required elements from particular mines in Chile, etc.
Lew
Re:Friends of mine have been working on this (Score:2)
I'm sorry but I won't be happy until... (Score:2)
Anything short of that, while it might be "OK", is just not good enough in my opinion.
:)
What's different this time (Score:5, Insightful)
- a peer-reviewed article appearing in a major (if not the major) scientific journal,
- reporting an experimental result (not a business plan),
- that we're hearing about because the article is going to press (not because it was planned or submitted; admittedly, we're hearing it a little early because of advance reports).
These are all good signs of good science. The better sign will be attempts to reproduce the experiment, with both successes and failures published in the same professional manner.It's an extraordinary claim, and will require extraordinary evidence. Yes, this is just a first step; but at least it's in the right direction.
Want to make some fusion yourself? (Score:5, Informative)
You too can make sonoluminescence happen [physik3.gwdg.de]. Try it with some deuterium and see if you can get fusion. Sound complicated, just use this easy to follow guide [physik3.gwdg.de]. It will give you step by step instructions for reproducing that special kind of magic that is sonoluminescence. All you need is:
- sinus generator: (sounds a bit painful)any function generator working around 25kHz, adjustable to +/-1Hz
(+/-10Hz may work, too)
- amplifier: nearly any kind of audio amplifier will do. If you're not sure, measure
the saturation voltage: 40V peak-to-peak should be enough.
- 2-trace oscilloscope
- 2 piezoceramic Transducers (drivers): [physik3.gwdg.de]around d=16mm in diameter, h=8mm thick
- piezoceramic pill-transducer (microphone): [physik3.gwdg.de]around 3mm in diameter, 1mm thick
- three finger clamp
- laboratory stand
- flask:take a 100ml Pyrex/Duran spherical flask, diameter 65mm, with a small neck. An industrial one has poor optical quality, so better take a free blown one.
- coil(s): around 20mH, see text [physik3.gwdg.de]
- resistors: 1M, 10k, 1R
- coaxial cable
- quick-drying epoxy glue
- an eyedropper or a syringe (one of those little do-it-yourself subcutaneous is very good)
- degassed [physik3.gwdg.de] distilled water:
- Pyrex/Duran Erlenmeyer flask (0.5 or 1l) and airtight stopper with pipe, rubber hose and clamp to close it
- aluminium/highgrade steel drinking bottle (0.5 or 1l) with screw cap; one of those found in camping stores, a bare one without varnish
- a bubble
;-)
oh, and it is nice to have:or
- second oscilloscope
- vacuum pump
- high-pass filter
- laser
Go for it kids. By the way, my favourite part is this quote: "Increase the driving voltage until you hear a horrible screeching noise, which sounds like your flask is going to crack. Don't be surprised if it does".I have to fill in some more text here, becasue slashdot sais I have too few characters per line. Well its just a bloody list of things. Of course there won't be much to each line, what do you expect?
Nice to have a laser (Score:5, Funny)
In the "nice to have" section, it mentions a laser.
Well, der, I think this is obvious. Its always nice to have a laser. You could put this on basicaly any list of "nice to haves" for anything:
Re:Nice to have a laser (Score:4, Funny)
7. a laser
8. a superconductor
9. an electron microscope
10. a magnetic resonance imaging device
11. superfluid helium
12. a terraflop computer
13. a microsecond - gigawatt capacitor bank
14. antimatter
15. a gravity wave detector
16. a thermonuclear device
17. a naked singlarity
18. a dyson sphere
19. exotic matter with negative energy density (quite useful for preventing wormholes from collapsing)
20. a heisenberg compensator
21. an infinite improbability drive
He who experiments with the coolest toys wins!
Correction - temperature of *center* of sun (Score:3, Informative)
The article claims "simulations also indicate that temperatures inside the collapsing bubbles may reach up to 10 million degrees Kelvin, as hot as the center of the sun." and "Temperatures inside these bubbles can be as high as 5000-7000 degrees Kelvin, about as hot as the sun?s surface. But, recent experiments by a number of researchers suggest that bubble temperatures can reach even higher temperatures--closer to the heat needed for nuclear fusion
Deuterium 'burns' at much lower temperatures than the ordinary hydrogen burning that powers our sun (where reaction rates are so slow it will take billions of years to use up the fuel supply.)
Paper in PDF and Abstract (Score:5, Informative)
Here is a link Science Magazine is providing:
Science Magazine [sciencemag.org]
It has a pdf [sciencemag.org] version of the article in question. Here is the abstract.
Bubble temperatures are not well-known. (Score:5, Informative)
The evidence for fusion-capable temperatures inside a sonoluminescing bubble lies in two main categories:
- You can examine the emission spectrum of the bubble. The spectrum is continuous, with a peak which depends on a variety of factors (noble gas content, temperature of the fluid, etc.), so you can try to figure out the temperature based on the emission expected from a blackbody of a similar temperature. The last I heard, the temperature was at least an order of magnitude less than what you would need.
- You can run simulations which make assumptions about the bubble collapse mechanism. If the bubble remains perfectly spherical during the collapse, then you may get the temperatures being quoted in the article. But there are other theories for the collapse, and requiring the bubble to remain perfectly spherical during a violent collapse doesn't seem intuitively obvious to me.
It's been a few years since I worked with this stuff, so take this with a grain of salt, but I'm not optimistic about this paper being validated.No wonder P&F got it wrong (Score:2)
Nothing new here ... (Score:4, Informative)
The talk was pretty good. Their models were able to explain most of the features reasonably well without having to resort to exotic physics (i.e. quantum electrodynamic weirdness). I mostly remember sitting at this talk because the presenter made a reasonable witty comment (remember, talks like this are usually dry and boring with many audience members nodding off because they are always scheduled after lunch): `Scientists at LLNL have an innately superior understanding of all physics
However, the talk did run into a credibility problem when the presenter said the next step was too look for fusion. Several people in the audience correctly pointed out that the temperatures were several orders of magnitude too low. The presenter's response was that the
Without seeing the paper from the ORNL people, I really can't say if they have upped the sophistication or not though.
By the way, the temperatures at the surface of the sun are only ~6K (except in the wispy corona). Not nearly hot enough for fusion
Kevin
Re:Nothing new here ... (Score:2, Funny)
Please tell.
Re:Nothing new here ... (Score:5, Interesting)
A electric discharge creates a plasma such that a fraction of the argon and mercury become ionized (it is a very small fraction). As a result, lots of free electrons are running around. Some of these electrons cause excitation of mercury (either directly or indirectly) which after some radiation transport magic is converted to visible light. Some of the electrons cause further ionization which keeps the discharge around.
For ionization and excitation to occur, the electrons have to be at a high temperature. Argon ionizes at 15eV and to have enough electrons that hot you need electron temperatures over 10,000K (typically 40,000K+). The conversion is roughly 1eV to 11,600K.
The catch is that the electron mass is about 70,000 times less than that of argon. To picture what is going on, electrons are ping-pong balls and argon / mercury are bowling balls. Even if you throw a ping-pong ball really really hard, a bowling ball won't notice it.
As a result, the electrons are able to heat up to very high temperatures. Meanwhile, the glass tube at room temperature keeps the Ar/Hg mix cool. Thus, even though the electron temperatures are high, the heat conduction is incredibly low and the tube feels cold to the touch.
Since this site is interested in computers, these types of plasmas are used in almost every step of semiconductor processing. Because the electron energies are so high, exotic high temperature chemisty can be performed without melting your wafer. And because there are charged species, etchant flux can be electrically manipulated (which is why you have microchips which small features nowadays; look up plasma enhanced anisotropic etching).
As for dangerous experiments, I can think of a few but rather than get sued
Kevin
Re:Nothing new here ... (Score:2)
I'll take a wild guess and say he's refering to microwave ovens. They will cause both flourescent and normal lightbulbs to light up quite nicely. Lotsa fun stuff there.
Of course there's always that lovely qoute to the effect of "people who play with hazadous materials materials sometimes get injured or killed".
Most of the really fun stuff is dangerous. So far I've managed to avoid any serious injury, but I can tell you accidentally inhaling a bit of Sulfur Dioxide is quite unpleasant.
-
Re:Nothing new here ... (Score:2)
Re:Nothing new here ... (Score:2)
To keep things on topic, sonolumenscence typically gets temperatures of 100,000K to 1,000,000K.
Also, the surface of the sun isn't hot compared to the core of the sun (6,000K with a near vacuum mass density at the surface versus about 15,000,000K in the core with a mass density greater than lead). Fusion only happens in the core. Fusion requires a hell of a lot more energy that fluorescence.
By the way, the K here is for Kelvin (not for thousands). Plasma physicists measure temperature in electron volts (eV) or Kelvin. Here are the conversions off the top of my head:
[eV] = 11,600 [K]
[C] = [K] + 273.16
[C] = 5 * ( [F]-32 ) / 9
Enjoy,
Kevin
Re:Nothing new here ... (Score:2)
Since you asked, temperature is usually a measure of the random energy. That is, if I know the temperature of gas, I can say the average molecule has such and such energy, the molecules have such and such a velocity distribution and as a result chemical reactions proceed at this rate
However, temperature is a tricky concept in both plasma physics and quantum statistical mechanics. In plasmas far from thermal equilibrium (most are), temperature can actually be pretty meaningless. In quantum statistical mechanics temperature has to do with how the number of microscopic states available to the system changes with changes in total system energy (as a result, some spin magnetic systems can actually have a negative temperature). However, mostly physics grad students really worry about those technicalities.
I didn't mean to insult. However, if people were reading the temperatures though that K was an abbreviation for thousands, they might either:
- Go running around telling people that The Man is fusion down
- Think I have no clue (which remains to be seen).
Kevin
Re:Nothing new here ... (Score:2)
You are quite perceptive about accreation disks. A class of supernovae is thought to be due to surface fusion in a neutron star binary system (the regular star is eaten by the neutron star and fusion of spiraling cannablized material occurs on the neutron star surface
Some chirped pulse tabletop laser experiments have achieved miniscule amounts of fusion. Basically, if you hit anything with 10^20 W/cm2 weird stuff will happen.
It is possible for a couple of random H's to slap into each other to fuse. At low temperatures and densities though is it exceedingly unlikely (wait the lifetime of the universe kind of thing).
Muon catalyzed fusion was experimentally shown to make fusion easier to do at lower temperatures in the 1960s. Muons are just like electrons but 207x more massive. In muonium (i.e. a hydrogen atom with the electron replaced by a muon), the muon has a much tigher orbit than regular hydrogen. The muon shields out much of the proton's electrical charge
Tomamaks get some fusion but it is still quite a ways off. Depending on how optimistic you are about electrical power extraction and economic feasibility, we currently have reactors near breakeven (I've seen technical articles indicating if you fusion as a breeder for fission, we are beyond breakeven). I could speak at length about various forms for controlled fusion, but I have some old slashdot posts that talk about the matter a bit (look up the one called "Ass-talking").
Kevin
Interesting if true... (Score:2)
interesting way to demonstrate nuclear fusion
to freshman physics students. However, if it
works, it is just another unproductive fusion
technique. Call me when they refine it to
give off more energy than it consumes.
2 thoughts (Score:2)
Just because there's fusion of 2 D's into T doesn't necessarily mean it puts out more energy than went in.
And wouldn't it be cool if these guys get together with the guys that figured out how Guiness makes some bubbles sink. They could make a movie with Yahoo Serious.
SPACE.com article (Score:2, Informative)
Laptop Power (Score:2)
That would be cool, but it's probably not going to help on airplane trips...
"Once again, the operation of nuclear fusion reactors is not permitted on this aircraft while in the air or while taxiing on the ground. Nuclear fusion reactors are also not permitted at any time when sitting in a row with a child under 3 years old, due to the neutron flux. Please be considerate of your fellow travelers who have small children."
Those mean scientists, using good instruments (Score:4, Funny)
A Dean drive generates reactionless force of a special type. To measure this force, we use a special unit, the Bathroom Scale pound. BS pounds are whatever my bathroom scale measures. My bathroom scale seems to be more sensitive than Dean's. When I stand still on it, I weigh about 195 BS pounds. If I shake my arms at the right speed, my weight drops to 175 BS pounds. That is better than .1 BS G thrust. I suspect a carefully tuned counter-weighted drill motor can do far better.
So when I finally get my device perfected and my paper published, some mean professor is going to explain that measurement equipment may produce incorrect readings in certain situations. That it isn't enough to get the reading you want, you actually have to show you got a valid reading.
For those who want to duplicate my experiments so far, get an aged Health-O-Meter spring scale. Other types of scale have some weird reality field around them that interferes with crack pot physics.
You *can* do tabletop fusion (Score:2, Interesting)
See for example this [uni-marburg.de], or this [uni-marburg.de].
"I'm not hot doggin ya!"
-dB
Some Questions (Score:2)
1) What is cold fusion and how does this compare to it?
2) It doesn't produce nuclear waste, but what are still the side-effects?
3) How far away are we from ever using this as a real energy producing system?
4) Were we "supposed" to be at this point so soon? I always thought fusion was "hundreds of years away."
Thank you. I'm trying to better grasp this.
Strange... (Score:3, Interesting)
The way this is sounding - it is sounding like so much "voodoo science", simply because of the irreproducibility of it (but, who knows? Maybe others will have success - may be too early to tell)...
Taleyarkhan apparatus includes neutron source (Score:3, Interesting)
It also explains why 2.45 Mev neutrons, which Teleyarkhan claims are the byproduct of the fusion of Hydrogen-2 into Helium-3, are seen coming out of the flask. They are simply 14 Mev neutrons which have slowed down by bouncing off various nuclei.
Re:Taleyarkhan apparatus includes neutron source (Score:3, Interesting)
I am observing desktop fusion right now. (Score:4, Funny)
Trust those Nordic types to always be one step ahead! Next they're going to be inventing, like, operating systems, or something, on their tabletops!
'Looks legit' (Score:2)
How about about
Ah well that's better a good venting always helps the old blood pressure.
Some physics comments on the manuscript (Score:3, Insightful)
Just finished reading the pdf of the manuscript. My biggest concern is the magnitude of the observed effect- a few standard deviations above background. The data acquisition runs lasted 7 or 12 hrs (or for several iterated 300s runs with another detector). The question raised here is, if you've got marginal statistics (particularly for an exceptional effect, if truly observed), then why not run the experiment longer, like a month? That should yield a strong enough signal that statistics are no longer an issue. With a small set of runs, there lies a risk of subconsicously self-selecting a fraction of the runs as the 'good' ones. I'm not saying that's what happened, but it can't be ruled out based on the data at hand.
Second concern is the accuracy of the shock hydrodynamic simulations, both the assumption of perfect spherical symmetry (which is crucial to a high concentration of energy at the very center) and the treatment of the complex interactions in the plasma during compression (Born-Mayer potentials, as used here, are outside their realm of validity when the substance ionizes, I suspect).
I'm not prepared to say "obviously wrong," (open mind = good) but there are red flags...
yeah, this is interesting but... (Score:2)
This observation doesn't seem to be especially useful, at least for power generation. The article doesn't give any numbers, but I'm guessing that they number of hydrogen atoms they are claiming reacted is quite small, like hundreds. In that case the energy generated would be quite small, just a few joules, on the close order of 1-10.
I think it would be foolish to assert that hydrogen fusion NEVER occurs at low energies, thats just ridiculous, random hydrogen atoms must bump into each other occasionally and undergo fusion, its just very unlikely to occur frequently at low temperatures.
BUT, this discovery, if it checks out, will probably just be a scientific curiosity, it's almost certain that this reaction would be unable to scale up to levels required for practical power generation of any kind. On the upside for the scientists, they'll probably get a footnote in the history books as the first people to observe and produce proof of nuclear fusion at low energies. Which is worth something, if not the nobel prize.
Table-top fusion has already been done (Score:3, Informative)
The solution is simple... (Score:2, Funny)
The solution to desktop fusion is simple:
You take P and F's deuterium electrolysis experiment and stick it inside a sonoluminescence vessel.
The electrolysis produces the bubbles, the sound waves batter them so hard that fusion is created within them.
Hell, if Keanau Reeves can do it in the movie Chain Reaction then surely these researcher types can manage it.
(big fat grin)
Hold your horses everyone (Score:2, Interesting)
It does claim that fusion is a possible explanation for sonoluminescence and that the results are still under review.
I would like to say this at this juncture. The discipline of science requires the vigorous investigation of phenomena, explanation of phenomena, and the vigorous critical review of explanations of phenomena.
All of this requires public review as often as possible. Vast misinterpretation of reports and massive derision do not help the cause of science.
The researchers claim simply that sonoluminescence may be explained by fusion achieved when a)the proper isotopes are present and b)small bubbles collapse to generate high energy for a moment. This ocurs after seeding with neutrons.
Sounds plausible to me. They do explain how this is happening, and performed a control test. Next comes replication of results. And please folks, dont rely on the first two attempts. Do you think the first replications of experiments by the Wright Brothers, Fermi, Marconi, or Tesla worked? Science is rife with failure to the extent that after something graduates to technology it is still not reproducible. Anyone ever buy a solid state laser that did not work? Does that mean that laser theory is wrong?
Besides, one reason we all measure gravity in high school physics is because we are rigorosly testing Newton. Every time. Every calculation. To make sure.
This is not religion, it does not happen overnight. The Science Pope cannot decree "fusion in a bottle". It might just mean that here there be fusion at an overall loss.
I for one hope it is true, it could be a way to regain energy as pressure increases outside an airframe during reentry, utilizing the increasing air pressure to drive the fusion process.
Dont be so quick to deride this, dont be too quick to embrace it. Remain skeptical as to it's possibility and it's uses. Just cause it seems so, dont mean it is. And just cause it's not know dont mean it wont.
Is it background or is it real? (Score:4, Insightful)
At the close of 1939, a woman sat on a snow covered log in a Swedish forest and re-read a letter from a chemist in Germany. The chemist had detected barium where he hadn't expected to find any. He wrote her because he couldn't figure out where the barium was coming from. The woman, Liese Mietner, figured out that the chemist, Otto Hahn, had split Uranium. Without Mietner's insight into the underlying physics, Hahn's observation might have been dismissed. So there might indeed be "some crazy chemistry..." taking place.
On the other hand, as soon as Mietner's nephew got back to England from his Christmas break, the British were reproducing Hahn's experiment. Without reproducible results, the results could just be background noise.
Cool, Just Like that Keanu Reeves Movie (Score:2)
BTW, Sonoluminescence [sciam.com] (a form of acoustic cavitation) is the same effect behind Wint-o-Green lifesavers making 'sparks' when you crunch them. Luckily the temperatures of the lifesavers doesn't get anywhere near the temperature needed for nuclear fusion.
Science Editor Makes Statement (Score:3, Informative)
Donald Kennedy, Editor
http://www.sciencemag.org/feature/data/ho
Every once in a while, we at Science receive a paper that causes us to
exercise particular care in handling, because it may be controversial or
because it is importantor both. The paper by Taleyarkhan et al. on p. 1868
of this issue is a case in point. It qualified for careful, responsible
treatment on both counts. And its history with us has exposed some of the
more unusual challenges that can arise in the publication process.
The paper reports experiments in which sonoluminescence is induced in
solutions of deuterated acetone subjected to sound waves and neutron
irradiation. These conditions cause bubbles to grow and then implode,
locally generating high pressures and temperatures and the emission of
sonoluminescent light. The authors present evidence for the production of
tritium in the solution, and for neutron emission coincident with the light
emission. They cautiously interpret these observations as evidence that
deuterium-deuterium fusion occurred in the imploding bubbles. That prospect
naturally encouraged us to treat the paper with care.
After the external review process had been completed, we scheduled the paper
for publication. Then we were contacted by senior science managers at Oak
Ridge National Laboratory (ORNL), who said that certain reservations had
developed
about the findings and their interpretation. In a series of telephone and
e-mail contacts, they urged that we delay the scheduled publication of the
paper. The authors participated in a series of meetings to discuss
objections raised by the ORNL managers, including some findings made by a
second group of scientists who had been asked to perform additional tests,
using the same apparatus but a different detector.
After some negotiation, a compromise was reached in which the authors
responded to criticisms and subsequently made some modifications in the text
to accommodate them. They also agreed to cite a short nonpeer-reviewed
communication in which the second group present measurements that disagree
in some respects with theirs, along with their own response to it. While
these agreements were being reached, Science received communications from
two distinguished scientists in this field, raising objections to the paper
and urging that we reconsider our plans to publish it. And the matter became
even more public on 1 March when Robert Park issued an airy, premature
dismissal from the American Physical Society. By this time, it had become
clear that a number of people didnt want us to publish this paper.
I have been asked, "Why are you going forward with a paper attached to so
much controversy?" Well, thats what we do; our mission is to put
interesting, potentially important science into public view after ensuring
its quality as best as we possibly can. After that, efforts at repetition
and reinterpretation can take place out in the open. Thats where it
belongs, not in an alternative universe in which anonymity prevails, rumor
leaks out, and facts stay inside. It goes without saying that we cannot
publish papers with a guarantee that every result is right. Were not that
smart. That is why we are prepared for occasional disappointment when our
internal judgments and our processes of external review turn out to be
wrong, and a provocative
result is not fully confirmed. What we ARE very sure of is that publication
is the right option, evenand perhaps especially
when there is some controversy.
A reporter also asked me whether this was the only time pressure has been
put on Science not to publish a paper. Although this case is exceptional, it
is not unique; we have been there before. The motivations for urging us not
to publish have varied from one case to another. Often they rest on serious
legitimate scientific differences of opinion, although sometimes that is not
so clear. In this instance, we see no good reason for abandoning our plans
to publish the paper, and we can see no merit whatsoever in the efforts to
discredit it in advance. Both the premature critics and those who believe in
the result would do well to wait for the scientific process to do its work.
Anniversary of cold fusion (Score:2)
I remember the cold fusion begin on the start of a
spring break exactly 13 years ago.
Must be something in the air that turns men's minds
to fantasy.
The Village Voice loves its cold fusion, huh? (Score:2)
Which is to say take their article with the requisite grain of NaCl.
Re:Mmmm... tabletop fusion generator (Score:2)
You're confusing fusion with zero-point energy.
... which is already in your tabletop, so I guess that still counts...
Re:Fusion: Efficient and dangerous (Score:2, Interesting)
Okay, if you had read the article, you would know that this is barely the first step. They haven't even ascertained if the reaction produces more energy than what it requires to sustain. If it doesn't (with this method), then it's just an interesting way to produce neutrons and tritium, period.
Second, IF it is determined that more energy is coming out than goes in, a way has to be devised for the neutrons of one set of reactions to seed the next set (preferably the next hundred set).
Third, just because something is potentially dangerous doesn't mean we should restrict it. AN OBJECT IS DEAD WITHOUT AN ACT OF WILL TO USE IT! If you've got problems with the way people use technology, then you need to go after the causes, the reasons WHY people decide to do nasty things, not try to restrict the technology itself.
You know, if flight technology had been restricted, the events of 9/11 would never have occured..
Re:Fusion: Efficient and dangerous (Score:5, Informative)
People like you are going to drive me prematurely bald...
Fusion reactors != fusion bombs
Fustion reactors are so damned far removed from fusion bombs that it's been about 50 years since we developed the second and we still haven't figured out the first. I'm willing to bet it will take at least another 50 years after the development of fusion reactors before we can make a fusion bomb that doesn't require a fission bomb to actually get the thing to go off.
"While it's true that a nuclear explosive based on this current method wouldn't spread as much harmful radiation as a uranium based explosive,"
You're right about that, but you have no idea how right you are.
First and foremost, the act of fission frees neutrons from their parent atoms. A lot of neutrons. Enough neutrons to set off the fission reaction. Fusion generates far fewer free neutrons (if at all, depending on your fuel) because it's busy trying to form atoms instead of breaking them apart.
Secondly, when people think of "radiation" from a bomb they think of the fallout (since the actual radiation from the explosion lasts as long as the actual explosion). Fusion in and of itself has no fallout. The fallout from modern hydrogen bombs is from the fission bomb that's used to set it off. No fission bomb, no fallout.
"it's potential damage far outweighs that of a dirty bomb."
Now here is where you need to lay off the crack pipe.
Getting a fission reaction to start is pretty easy: get a neutron-producer close to a clump of unstable atoms. Getting a fusion reaction to start, on the other hand, requires a LOT of input heat in the beginning in order to generate the plasma the reactions takes place in. So much heat that the pressure at the heart of Jupiter isn't enough to start a sustainable reaction. In the past 50 years the only way we've been able to pull it off is with a fission bomb.
But let's pretend that a pure fusion bomb is possible in the short term. Although it's possible to squeeze a fission bomb into something the size of a suitcase, your average 20 megaton device is more or less a cubic meter in size. But it's only that small because the heat generator is a tiny little suitcase-sized fission bomb. If we try to use a fusion reactor to generate the heat instead of a fission bomb, I don't see the device being small enough to fit into a cargo container (probably the largest possible size for a device to be useful to terrorists).
But what if they try to blow up a fusion power plant? Fission reactors are heavily shielded to keep the inside in. Probable fusion reactors would be heavily shielded to keep the outside out. If a tokomak loses magnetic containment, the plasma expands, cools, and reverts back to a gas. If it loses its physical containment, air gets in, conducts/convects away heat from the plasma, the plasma cools and reverts back to a gas. If you try to blow it up you just end up with a negligible amount of hot gas on top of the explosive.
Personally, I'd be a hell of a lot more frightened of an attack at a coal-fired plant. Have you ever seen what a spark can make coal dust do? Or what about popping off the fuel tanks at a natural gas power plant? And while I'm on the subject of boiling liquid-vapor explosions, oil refineries look awfully unprotected...
Re:Fusion: Efficient and dangerous (Score:4, Interesting)
Regarding the number of neutrons produced by fusion and fission reactions, yes a D-T fusion reaction produces only one neutron while a U or Pu fission produces between about 3, depending on energy. But take into account that a single fusion reaction produces only 17.6 MeV while a single fission produces about 200 MeV. Add to that the fact that a large fraction of the neutrons in a fission reaction are used for inducing further fissions in the material. Remember neutron bombs? Tactical nukes meant to kill the crews of sovient tank hordes, while hopefully leaving the rest of West Germany relatively intact. They had very minimal amount of fission material in them, about 95% of the energy produced was by fusion. The reason was to have a as high as possible neutron flux, and also to minimize fallout. Most strategic warheads deployed today have only about 50% fusion output. The reason is that the casings are made of enriched uranium, the reason being that the Ulam-Teller staged radiation implosion type bomb needs a casing made of high-Z material for refllecting x-rays produced by the primary. So by additionally making the casing of fissionable material (it wont fission by itself, only fission induced by the fusion neutrons) you get better bang-for-weight.
And regarding detonating a fusion bomb without a fission primary, I read some rumors a while ago that the russians reportedly had some chemical explosive called "red mercury" capable of detonating a fusion bomb directly. As it IMHO sounds quite improbable, I'd guess it's just some rumor.
Re:Nobody better tell Osama ... (Score:2)
Re:kinda OT: Mirrors... (Score:3, Interesting)
Re:kinda OT: Mirrors... (Score:2, Interesting)
1) Mirror the site privately, no public links. This should fall under fair use as long as nobody is able to access it from the slashdot main page.
2) Send an email to the webmaster stating that you are about to link to his site, thus throwing an ungodly amount of hits his way, and that you can toss up a mirror to reduce the strain on his poor, poor webservers.
3) Wait a hour or two for a reply. Its not like
Tim