Question of Sound Fusion Power Generation

Morbius

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Astronuc said:
Morbius,

I was thinking about electron beams and perhaps Z machine, but I don't know where they are in comparison with other methods. At the moment, the Z-machine is producing lots of X-rays with temperatures of the wire ~1.6 million K (or about 140 eV). They need about 100 times that amount IMO - 14 keV (160 million K) for any reasonable attempt at fusion.

I wonder when they will get there?
Astronuc,

Yes - there are lots of different proposals - all in different states of development.

Before LLNL decided on builing NIF - and all we had was Nova; which had pretty
much reached its maximum capability; I was really wondering if the inertial
confinement community would turn more to something like Sandia's Z-Machine.

It is interesting to look at all the diferent concepts. In the magnetic fusion arena,
everybody thinks about tokamaks. However, there were magnetic fusion devices
before tokamaks - simple magnetically wound torus, then the stellarator with
helical windings, also yin-yan magnets, magnetic mirror machines [ MFTF ], ...

Who knows what type of machine will be the next "bright idea"?

Dr. Gregory Greenman
Physicist
 

vanesch

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ZapperZ said:
So vanesch, what is your gut feeling about Taleyarkhan's claim in all of this, knowing the type of measurement he claim to be doing?
Honestly, I don't know. Detecting neutrons with a neutron detector is not such a difficult thing to do, but you need - as with anything - to know what you're talking about - so, like you, I'm puzzled by some strange statements which are indeed red flags - and it is more a matter of psychology than anything else to establish whether or not this is an indication of fraud or bad practice, or just an overlooked detail.

Nevertheless, it would be rather simple to establish whether or not there are neutrons produced. I haven't read the original article so I don't know whether this was done, but it seems to be rather elementary practice, independent of the type of neutron detector used.
First of all, you measure the background (there are cosmic neutrons, there's noise in the detector...). Next you bring in a known neutron source, and you verify whether you count them. Next, you bring in a gamma source, and you verify your sensitivity to any gamma radiation. Finally, you do an "electromagnetic perturbation" test, where you switch on all the electrical appliances, but without the potential source you want to measure: you should fall back on your background. If not, it simply means your detector (or its wiring-up) is an antenna for the electromagnetic activity in the neighbourhood (something which is very, very often the case and a real pain!).
Next, you do your measurement.
Finally, if you really want to be sure, you redo all the tests after the measurement.
If you see a clear neutron signal above background, no effects of any perturbation, and a low gamma sensitivity, and the measurements are repeatable, then I'd consider that the presence of neutrons has been established.

But all this sounds simply like elementary good lab practice, *especially* if your claim stands or falls with the established presence of neutrons. If I were there, I'd do all this, just for myself, in order to be sure! So I'd assume, from the start, that this is done, in which case, indeed, it doesn't matter exactly WHAT kind of neutron detector is used. The procedure should indeed be rather insensitive to the kind of detector used.
In fact, it would be easy to silence any negative comments by INVITING people to come and measure the neutron activity for themselves, and by letting them do the entire procedure above themselves. It's done in an afternoon !

EDIT: I forgot: a very good test to establish that you've really seen neutrons, is by redoing the experiment, but by wrapping the detector (inside the polyethylene) in a sheet of cadmium. This should drastically lower the counting rate of real neutrons.
 
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vanesch

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Astronuc said:
As for gamma radiation (~0.48 MeV), it does come from the decay of 7Li* which is produced in approximately 94% of (n, [itex]\alpha[/itex]) reaction with 10B. But it is not clear that is what they were doing.
No, this is gamma radiation during the neutron detection event, but it means that there IS already a neutron detected. The incomprehensible thing was the talking about gamma radiation produced by neutrons in the poly-ethylene. To my knowledge, neutrons on polyethylene doesn't produce gammas at all.
 

vanesch

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Astronuc said:
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PLEEE8000069000003036109000001&idtype=cvips&gifs=yes [Broken]
Phys. Rev. E 69, 036109 (2004) (11 pages)

:confused: :confused: He uses a PULSED NEUTRON SOURCE to generate the bubbles ???

Why use a neutron source, if the significant effect you want to see, are a few neutrons ??

Then all bets are off, honestly. You have a MODERATOR there in your lab, and a pulsed fast neutron source. When you change your moderator (like, when generating bubbles in it), you modify the neutron transport problem, and nothing tells you that you're not going to deflect part of the initial pulse of neutrons to be detected later, no ?

Also, I don't understand his neutron spectrum. You would expect the neutrons going in and coming out to be at least partially moderated, no ?

EDIT:
when looking at:
http://www.kayelaby.npl.co.uk/atomic_and_nuclear_physics/4_7/4_7_3.html

I see some significant problems.
For instance, the average absorption length in water is 27 mm, which is probably why, with normal acetone, he doesn't see much: all the moderated neutrons are absorbed.
In heavy water (~ heavy acetone ?), this length is 970 mm, so they surely come out again.

Also interesting, the slowing down time in normal water is 6 microseconds, and in heavy water is 53 microseconds. This could explain why nothing is seen "just after" the pulse, and only later.
The lifetime of neutrons in heavy water is 100 MILLIseconds, so a pot of heavy water can contain such neutrons for quite some time.

So a pulse of fast neutrons on a pot of heavy water (or heavy acetone ?) will "saturate" it after about 53 microseconds with neutrons, which will then diffuse out slowly until 100 milliseconds later. I don't know what is the effect of making bubbles into this: do neutrons get out faster ?
 
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Astronuc

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a very good test to establish that you've really seen neutrons, is by redoing the experiment, but by wrapping the detector (inside the polyethylene) in a sheet of cadmium. This should drastically lower the counting rate of real neutrons.
Or alternatively, one could use a Pu-Be or Sb-Be neutron source of strength comparable to that which Taleyarkhan's group claims for sonofusion. With a neutron source of known strength, it would be possible to test the detection arrangement.

I haven't read the paper, and the kayelaby link isn't working for me at the moment.

Thermal neutron capture gammas (2.2 MeV) from hydrogen in the polyethylene, (ref: http://www.hps.org/publicinformation/ate/q5218.html) [Broken]
but that still doesn't resolve questions about reliability of the results. I'd have to read the paper.

The presence of bubbles would increase the transport/diffusion distance, but only in the acetone (obviously).

Vanesch, I am not saying I agree with what has been reported, and in fact I share your skepticism. You raise some very good questions, which any responsible scientist/engineer should raise.
 
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vanesch

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:redface: Concerning the neutrons on polyethylene, I didn't think of the absorbed neutrons, you're right there. Usually when you put polyethylene around a detector to moderate them in order to detect them better, you want this layer to be thin enough not to absorb most neutrons, so that this yield is small. That's why we never see them (and I didn't think of it).
But you're entirely right, neutron capture by hydrogen, producing deuterium, gives gammas of the order of the binding energy of deuterium.

To come back to the original discussion, until your cited paper, I didn't realise that there was a neutron source in the game, so I thought it was about a neutron-free lab in which suddenly an apparatus started producing neutrons. When there's a pulsed source in the neighbourhood, I'd say that all bets are off. It must be extremely difficult to prove that the neutrons are not lost neutrons from the source, but rather newly produced fusion neutrons.
If the only reason for the source is to nucleate bubbles, the effort should be put on finding another, neutron-free way to make these bubbles arise, otherwise I'd never believe it.
When I set up a neutron instrument, it is amazing where neutrons can come from. Usually, the first accusation is that my detector is counting gammas. I then have to go, with the instrument user, through a lot of procedures to show him that it are genuine neutrons.
An anecdote: Once I had the problem that there was a small defect in a detector image, but only when it was placed on the instrument. When I took it to the lab to analyse it, I couldn't reproduce the defect. The defect was in fact a design error, there was a small piece of stainless steel behind the detector which reflected a small fraction of the neutrons that got through the detector unnoticed, and hence got a second chance to be detected, a 0.3 % effect in the image, easily corrected in software, but we wanted to understand where it came from.
But the problem was that I couldn't reproduce it with a source in the lab... Until I put some polyethylene and B4C BEHIND the detector structure. In fact, the lab was surrounded by big plexiglass windows which partially reflected the neutrons of the source, so that the lab was actually bathing in a kind of uniform isotropic background neutron radiation, and the source was not the single point source I thought it was. This bath of neutrons, also irradiating the back of the detector, completely swamped the small reflection from the metal piece. I went outside, repeated the measurement, and I COULD reproduce it.
 

Morbius

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vanesch said:
Nevertheless, it would be rather simple to establish whether or not there are neutrons produced.
vanesch,

One would think so...

However, I remember watching an interview with a professor at Georgia Tech that
had been one of the early verifiers of the Pons-Fleischman experiment in "cold
fusion".

They had a technician who was very gingerly handling the neutron detector by its
cable - and putting it in the electrolytic cell to get a neutron count, and then moving
it behind a lead shield. Back and forth they went - in what they thought was a
controlled experiment - the neutron count rate when up when the detector was in
the "cold fusion" cell - and the neutron count rate went down when the detector was
moved behind the shield.

Then they switched to another technician. This one actually handled the detector
itself, and his hand was still around the detector when it was placed behind the
lead shield. However, the neutron count rate with the detector behind the shield
with the technician's hand around it - was just as high as when it was in the cold
fusion cell.

They then realised that the increased neutron count rate was due to the additional
moderation provided either by the water in the cold fusion cell, or the water in the
hand of the technician.

As the research group had already announced to the world that they had confirmed
the results of Pons-Fleischmann; the professor announced to his team, "Gentlemen,
we are in trouble!" The professor stated in the interview, that there are other things
that can give you counts in a neutron detector - other than what you think you are
measuring.

Yes - it is a simple matter to establish whether neutrons are produced - but you
better have people who understand neutron physics well enough to give you an
accurate measurement.

Dr. Gregory Greenman
Physicist
 

Astronuc

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One of my pet peeves regarding nuclear research is the way people make announcements via press releases, even before the results are independently verified. This is really inexcusable.

There should be a protocol by which an important experiment is independently reviewed (there appear to be capable independent reviewers at PF :biggrin: ) and then independent tested. This could be done confidentially under the auspices of the National Academies of Science or Engineering in the US and comparable organizations elsewhere.

I detest sloppy science and engineering. :grumpy: :yuck:
 
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vanesch

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Astronuc said:
I detest sloppy science and engineering. :grumpy: :yuck:
I hate sloppy science, but I like sloppy engineering. It gives you room to improve things, and have a second success with it :biggrin:
 

ZapperZ

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Astronuc said:
One of my pet peeves regarding nuclear research is the way people may announcements via press releases, even before the results are independently verified. This is really inexcusable.

There should be a protocol by which an important experiment is independently reviewed (there appear to be capable independent reviewers at PF :biggrin: ) and then independent tested. This could be done confidentially under the auspices of the National Academies of Science or Engineering in the US and comparable organizations elsewhere.

I detest sloppy science and engineering. :grumpy: :yuck:
I think, subconsciously, that whole incident shapped my present-day view on why I will only pay attention to peer-reviewed journals. I'm not saying that papers appearing in such journals are correct or valid, but at the very least, someone who has some knowledge in that field had a look at it. It is why I cringe when someone calls a press conference to announce some result, or someone already touting some e-print Arxiv paper (which is now a common practice in several fields in physics, including String, etc.).

I suppose that scientists, like people in general, are guilty of having short memory span and forget about these debacles.

Zz.
 

ZapperZ

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ZapperZ said:
More problems with the bubble fusion claim. Read this soon before you require a registration access.

http://www.nature.com/news/2006/060508/full/060508-8.html

Zz.
This mess just won't go away.

I'm going to copy this off of Science daily news update, because it annoys the hell out of me that a university administration seems to think an "internal" matter such as this should be kept under wraps. It looks bad on Purdue officials.

ScienceNOW Daily news said:
Purdue University officials today announced that they have completed a review on controversy swirling around Purdue nuclear engineer Rusi Taleyarkhan, the chief proponent of the contentious notion that sound waves can cause bubbles to collapse in a way that yields energy. Contrary to earlier statements by the university, officials now say they have no plans to make the review public or to reveal any potentially forthcoming disciplinary actions. "Specific recommendations of the examination committee and any subsequent steps by the university will be treated as confidential internal matters," said Purdue University Vice President for Research Charles Rutledge in a statement.
Rutledge appointed the review committee in March after an article in Nature described several Purdue colleagues as upset with Taleyarkhan because he had allegedly obstructed their work by removing shared equipment. They also said he tried to stop them from publishing results that contradicted his own. Other articles at the time also raised new questions about Taleyarkhan's scientific results (Science, 17 March, p. 1532). Calling the concerns "very serious," Purdue officials said they would launch a review and make the results public. Asked why Purdue reversed the decision to publicize the results, Purdue spokesperson Joseph Bennett would say only that "there was some confusion about that."

One possibility, outsiders suggest, is that Purdue limited the scope of its inquiry to Taleyarkhan's alleged inappropriate research behavior and did not extend it to the scientific controversy surrounding bubble fusion. University officials have declined to release either the committee's precise charge or the names of the committee members. But several sonofusion experts, who are both critics and coauthors of Taleyarkhan, say they were never contacted by the Purdue committee. "I don't think they contacted anyone [outside Purdue] and are looking at it as a personnel matter," says Ken Suslick, a sonofusion expert at the University of Illinois, Urbana-Champaign. "God forbid they talk to anyone who knows anything," adds Richard Lahey, Jr., a longtime collaborator of Taleyarkhan's at Rennselaer Polytechnic Institute in Troy, New York. Taleyarkhan and other Purdue University colleagues did not reply to phone or e-mail queries from ScienceNOW.

Taleyarkhan first reported that bubbles could collapse with enough force to fuse atomic nuclei four years ago in Science (Science, 8 March 2002, pp. 1808 and 1868). The work held out the prospect that the effect might be harnessed and scaled up to produce an inexhaustible supply of energy. But the findings have remained controversial ever since. Now, with Purdue's decision to seal their report, the controversy swirling around bubble fusion shows no signs of quieting down anytime soon.
But not making it public, it creates even MORE of mess, and throws doubt not just on the credibility of Taleyarkhan, but also on Purdue.

What were they thinking?!

Zz.
 

selfAdjoint

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ZapperZ said:
This mess just won't go away.

I'm going to copy this off of Science daily news update, because it annoys the hell out of me that a university administration seems to think an "internal" matter such as this should be kept under wraps. It looks bad on Purdue officials.



But not making it public, it creates even MORE of mess, and throws doubt not just on the credibility of Taleyarkhan, but also on Purdue.

What were they thinking?!

Zz.
Perhaps they were thinking of not being sued by Taleyarkhan?
 

Astronuc

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I hear you ZZ. This is ridiculous.

The work held out the prospect that the effect might be harnessed and scaled up to produce an inexhaustible supply of energy.
I wish people would quit making grandiose claims, and that includes research scientists. :grumpy: :yuck:

Four years later and there are still questions is problematic.

An internal review committee should have been in place 4 years ago, and a thorough review of the claims of sonofusion performed. Then they can make a press announcement.
 

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