Sonofusion in the news again.

[Edward Miller]

Great article. The headline is: "Sonofusion Experiment Produces Results Without External Neutron Source"

but wait.. further in the article we find... "the researchers dissolved natural uranium in the solution"

http://physorg.com/news10336.html

[wbongianni]

Why do articles like this never address the obvious question? Were more neutrons detected after the sound was applied, then was present from the uranium already present.

[BrettWilder]

i think it's because the intended audience doesn't know what a neutron is.....

just a thought

-b

[Carl Willis]

The sonofusion efforts continue to receive a lot of "casual criticism"--i.e. from people who have not seen the data--because they rely on nuclear methods of seeding the bubbles. This is a legitimate concern, until we look at the data from such an experiment.

Below is a graph from Nigamutin, Taleyarkhan and Lahey Jr., "Evidence for nuclear emissions during acoustic cavitation revisited." Proc. Inst. Mech. Eng. A, J. Power Energy (UK) no. A5 2004, p 345-64. I think my putting it up here qualifies as "fair use" but if anyone knows otherwise please let me know.

These are parallel plots made with a multichannel scaler. The detector is a big plastic scintillator and the instrumentation uses pulse-shape discrimination to select neutron detection events. A pulsed neutron generator (the "seed" generator) is fired at T = 0 in both cases, but in the upper plot the acoustic driver that causes sonoluminescent implosion of the seed bubbles is turned off.

Both plots show the huge neutron pulse from the PNG, right around T = 0. But these fast neutrons are slowed down, captured, and diffused away nearly entirely by ~ 100 us. The bubbles seeded by these neutrons implode much later, peaking at ~ 1000 us. You can see that in the lower plot. If the acoustics are turned off, seed bubbles may be formed but are not imploded by the SL phenomenon, and no neutrons are detected. The implication, of course, is that SL is producing neutrons. The time differentiation between the seed pulse and the onset of bubble implosion makes it easy to separate the effects of the two in the detection system.

There's no magic or strange new theory behind why these researchers variously use PNGs or uranium salts to seed the SL bubbles. Keep in mind that the process of seeding the bubbles works here the same way that a bubble chamber like the BTI dosimeter works. The process for seeding bubbles using high-LET radiation like fast neutrons, or alphas from a dissolved uranium salt, is well-understood.

-Carl

[BrettWilder]

you are awesome carl. where did you get this graph? i would like to read more, but all of the real articles/reports that i find online cost $$ to read.

i really would like to build a SL reactor using the free neutrons of my fusor. i actually made a post about this a few weeks ago, but it doesn't seem like i could pull it off with my relatively low budget.

do you have any external links where i can read more?

thanks,

-brett

[Carl Willis]

Brett,

The reason you have to pay so much money to access online papers is that the journal publishers are into the "business of science." Sure, there are some costs to offset, but mainly they're in it for a big ol' slice of green. Universities, funded by tuition fees, subscribe to citation databases and the publishers' full-text content, so when a person from the university's IP surfs there the site recognizes it as a paid user and doesn't pop up the usual outrageous bill of $20 to $50. It's handy to point and click a paper like this without having to leave my chair...but it's another contributor to the unaffordability of higher education.

The papers by Rusi Taleyarkhan are the ones to read first on this topic. The References in the previously mentioned paper are a good place to start. For example

Science 8 March 2002: Vol. 295. no. 5561, pp. 1868 - 1873 (Taleyarkhan's first big paper on these experiments)

Science 6 September 2002: Vol. 297. no. 5587, p. 1603 (Two other Oak Ridgers sent technical comments disputing the fusion claims of the previous article; also has Taleyarkhan's response with clarifications)

Sonofusion doesn't look like a hobby project yet, at least not an affordable one. The PNGs used don't really outstrip the average capabilities of a hot amateur fusor, but their instantaneous emission rates certainly do (10^8 - 10^10 / s), because they use tritium and because they have better ion sources . You'd be able to seed plenty of bubbles with a fusor, but you would not be capable of the careful timing that makes things so clear in the graph. The rate of neutron production from SL in deuterated acetone is estimated to be about (0.5-1.2) x 10^5 / s in the paper from which the graph was taken, so it is detectable but likely to be an order of magnitude below the emission of the seed source. All of this would just add demands to the care and calibration of the detectors. Of course, the biggest hurdle is getting a chamber that is acoustically appropriate for sonofusion to occur. Sonoluminescence is one thing--it can be done at home in a boiling flask--but getting the compression to cause fusion is a matter of spending $100,000 and up on chambers.


-Carl

[Carl Willis]

The whole uranium-as-seed issue has got me thinking: it seems theoretically feasible with such a setup to cause a nominally subcritical U-235 / acetone solution under cavitation to go critical. Or for that matter, criticality might be a feature of SL solutions themselves:

Assume that the bubble population is proportional to the fast neutron population (> 100 keV) in the liquid; that the fusion rate is proportional to the number of bubbles; and that each bubble is capable of producing in excess of one fast neutron on average. If all the above are at least approximately valid, we've got a multiplying medium that will have criticality behavior. Seeding a subcritical SL reactor with a pulse of high-LET radiation will result in a bubble population that decays over time. A critical system will be capable of running on its own indefinitely after only one initial pulse. Furthermore, there's considerable delay between bubble seeding and fusion-producing implosion. This has implications for the dynamics and control of the "reactor" which may be very useful if criticality is possible and energy production is desired on a large scale.

I suspect it's exceedingly difficult to get a critical SL reactor. Frequency of the acoustic cavitation, density of the medium, size, and acoustic power available might be critical to this ability.

Another thought is that an SL solution, itself a multiplying medium as proposed above, might be combined with a more traditional multiplying medium. For example, a deuterated acetone + U-235 salt solution. Here you could have a homogenous multiplying medium capable of criticality, but with more ease than the SL-alone case and with less than the nominal critical mass of U-235 alone.

I might as well point out that criticality implies nothing about the level of power a system can realistically attain. So a critical SL device might practically be very boring with only a few milliwatts per hour being produced. Then again, it could be a big deal. My hunch is that the bubble density cannot exceed a certain value or the ability to transfer acoustic waves through the medium is seriously disrupted, so maybe this is all a moot point.

Anybody want to comment?


-Carl

[Edward Miller]

I think all that Sonofusion needs is a Keanu Reeves http://www.imdb.com/title/tt0115857/

On a more serious note, it's good to see alternative fusion sources. It would be interesting to find a way to do multiple drivers in the liquid. I think there were shrimps doing cavitation somehow, but if you could multiply that mechanical process maybe you could put together a hybrid bubble system.

[Richard Hull]

Carl may have given away a farm here on the criticality issue. You are too fast Carl. Keep lookin' over your shoulder.

As regards the original response by Wayne; there are virtually no neutrons from uranium! As Carl noted they are using it in solution for the LET value of its alphas.

Carl helped a lot of folks see the light on Sonofusion. It won't make power, but it will show that fusion can be done in kinder gentler environments. I feel this is one of many steps in a discovery adventure on fusion or fusion like systems that don't involve the classic thermal path.

At the very least it will provide an incredible new side venture into new, unappreciated physics and, at its best possible outcome, it will change the whole ball game.

We will see.

Richard Hull

[Wilfried Heil]

Carl, thanks for pointing at this article. Indeed, it does look like fusion, in small bursts every 50 us (at 20 kHz). I will try to get the entire article and see what controls have been done.The question is then what makes it happen. It could be thermal fusion due to the bubble implosion. I think more likely would be a charge separation in the imploding or exploding bubbles, which may accellerate some deuterons to a few keV energies. In effect, a bunch of pulsed electrostatic micro-fusors.

If so, one might be able to do fusion simply by rubbing a deuterated piece of plastic. The electrons would knock loose some deuterons, which would then become charged and accellerated.

What kind of neutron detector did this group use?

[wbongianni]

A couple of points. The original work used neutrons as the nucleating site. Are you sure that alpha particles are now the particle of interest, why not fission fragments or the recoiling atom. The range of the alpha would be about 50 microns. Hydrodynamic forces might collapse them to a point, but its unlikely given the aspect ratio of the track. Also what would be the lifetime of such a microvoid.
The d-d reaction yields a 25 Mev output, against 4 Mev alpha (a nice little gain of 6 or so), so a chain reaction is not completely crazy, assuming every bubble resulted in at least one fusion. And assuming that the fused particle's seed void remains for the next cycle. Or even provided a seed for the current one.
Do all particles match the fusions? That is, is there at least one neutron for every alpha? Natural uranium is not the most prodigous producer of alpha particles, why not use a more radioactive source? Does the experiment scale with the amount of uranium salt used? The classic fusor is defeated by the presents of a physical electrode which ultimately intercepts the accelerated particles, what limits the sonofusion?

[Brian McDermott]

The RPI group uses a proton-recoil fast neutron scintillator.

[Carl Willis]

1) Very few fissions occur in this experiment, probably only a couple per minute, just to take a guess. They wouldn't have a noticable impact on the results.

2) the DD reaction has a total yield of 3.3 MeV, of which the neutron gets about 2.5 MeV through kinematic constraint. Watch the decimal point! However, there's still the possibility for an energy gain, since neutrons in the 10^4 eV range and up can still cause nucleation in a superheated liquid.

3) I think they chose uranium because it avoids the regulatory complications that would pertain to other strong, unsealed alpha emitters. It isn't the best choice from a functionality perspective.

4) The fusor has no possibility for chain-reacting critical behavior such as I outlined for sonofusion (and even then, I suspect the frequency of cavitation is an essential key to the possibility). Energy-recovery-wise, it has the same drawbacks as sonofusion, mainly that the energy produced by fusion either escapes the reactor or is converted into low-quality heat.

-Carl

[Richard Hull]

As Carl noted uranium is avaialble in common water soluable compounds. Rest assured that did NOT dissolve a fertilizer bag load of u nitrate in the thing. Probably , it was only a few grams.

Alpha's would probably do a better job than neuts in nucleation as they would not thermalize over a long track, but spend their energy (4-5mev) in a massive form over a mico track. As they are evenly distributed in the fluid, there are no hot spots just uniform emission throughout the fluid.

Richard Hull

[wbongianni]

Richard:
The alpha emission is not a hot spot, but distributed over a 50 micron range. The nucleation spot is in the sub micron range, so the alpha track is huge by comparison. Also how does the nucleation track, diameter about 2-3 angstroms, remain around long enough for a cycle to trigger on it? A 25 kHz, means a 40 microsecond cycle.

[Richard Hull]

By hot spot I meant the alpha emission is uniform thoughtout the liquid with no alpha hot spots.

The alpha emission is continous and as such goes on every second, every millisecond every microsecond, every femptosecond. It need not be timed to cyclic nucleation activities. Some fractional portion of alphas will be available at all instants in time.

Other alpha emitters would be far more desirable and efficient than uranium, but illegal or require complex NRC licenses or nasty radiation spill and cleanup efforts and containment.

The researchers used alphas mainly to shut down the "whiners" who poo-poo'd their neutron results for using a blast of neutrons to make neutrons.

There are no neutrons in uranium spontaneous fission reactions at the level of the few grams of U chemicals in the solution. At the dilution of the solution, very few sono-fusion, N related U fissions will occur, either. Once the fusion neuts slow to below 1mev in the fluid, they can't induce any fissions anyway.

It is like Carl said, a few fissions per sonofusion burst at best. These few neuts would create no noise issues in and amongst the true sonofusion blast of neutrons

Richard Hull

[wbongianni]

Here is the abstract in Phys Rev Let, 96:

Nuclear Emissions During Self-Nucleated Acoustic Cavitation
R. P. Taleyarkhan,1 C. D. West,2 R. T. Lahey, Jr.,3 R. I. Nigmatulin,4 R. C. Block,3 and Y. Xu1

1Purdue University, West Lafayette, Indiana 47907, USA 2Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA 3Rensselaer Polytechnic Institute, Troy, New York 12180, USA 4Russian Academy of Sciences, 6 Karl Marx Street, Ufa 450000, Russia
(Received 19 September 2005; published 27 January 2006)

A unique, new stand-alone acoustic inertial confinement nuclear fusion test device was successfully tested. Experiments using four different liquid types were conducted in which bubbles were self-nucleated without the use of external neutrons. Four independent detection systems were used (i.e., a neutron track plastic detector to provide unambiguous visible records for fast neutrons, a BF3 detector, a NE-113-type liquid scintillation detector, and a NaI ray detector). Statistically significant nuclear emissions were observed for deuterated benzene and acetone mixtures but not for heavy water. The measured neutron energy was 2.45 MeV, which is indicative of deuterium-deuterium (D-D) fusion. Neutron emission rates were in the range ~5×103 n/s to ~104 n/s and followed the inverse law dependence with distance. Control experiments did not result in statistically significant neutron or ray emissions.

©2006 The American Physical Society

The only number here is the 10e4 neutron/sec. which should be interesting to anyone here. Without need for a PNS, it could be verified by anyone with a moderate budget.