FAQ - Why no neutrons exit atoms in natural decay processes

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Chris Bradley
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Chris Bradley »

I've no idea what, or why, you are blithering on like this, but if you perform any neutron measurement at sea level you find there are enough around to measure a healthy signal with a sensitive enough detector.

Now, I can assure you that I've not seen any lightning around where I live in a real long time. So where are all these neutrons coming from that I can measure?

Muon flux at sea level is around 1 muon per cm^2/sec with a mean energy of 4 GeV (plenty enough energy to cause all sorts of trouble for an unsuspecting nucleus!), and are well known to be formed by cosmic ray bombardment of the upper atmosphere.
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Carl Willis
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Carl Willis »

Production of neutrons by electron capture on hydrogen was distinctly YOUR idea, David. It's not supported by anything I've ever read (including the PRL paper you mention now, which instead offers a much more reasonable photonuclear hypothesis for lightning-generated neutrons). That's why I asked you about your source.

That most neutrons at Earth's surface have cosmogenic origin is not my idea either, but it is the mainstream understanding communicated in the field's references of first recourse, and as Chris points out it's consistent with even simple everyday hobby-style measurements of neutron background whereas lightning activity isn't. Quite a number of us have experience operating large, sensitive, neutron detectors. The origin of the neutron background isn't really a matter of speculation.

Lightning-related production of radiation (neutrons, terrestrial gamma-ray flashes, relativistic electrons, etc.) is an interesting subject, and the 2011 paper you cited is therefore interesting, but it doesn't deal with what you were talking about. Your assertions look like pseudoexpertise parading as definitive statements, something that will not make you my friend or probably anyone else's on this site.

Finally, you mention being saddened by people not googling "lightning neutrons". By "people" I suppose you mean me. Allow me to retort. Lightning neutrons have been discussed on this site before. I have posted a Nature paper about the subject here before. Years ago. Did you use the search feature?

Lame!

-Carl
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DavidStewartZink
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by DavidStewartZink »

[ I'm not sure what the lightning flux at your house (or whether you can see it) has to do with the global values. No doubt it is very cool at your house, so you know the arctic ice cannot possibly have melted. But it is certainly worth noting that both lightning & thermal neutron flux vary by location & season ]

I thought we were discussing neutron flux (not muons), which I understand to be around (5-10 / m^2 / s) from cosmogenic sources, or about (3-5 * 10^15 / Earth / s).

"Thermal" flux (i.e. the "summer" flux resulting from the chain outgassing of Radon etc => alpha-decay => alpha-bombardment => loose neutrons) has an annual average near 0/m^2/sec but will (in the right parts of the world) reach spiky peaks around 100/m^2/sec.

A single bolt of air-ground lightning seems to produce in excess of many millions of low energy neutrons which reach the surface. How many reach earth from air-air lightning or what the effects of positive versus negative lightning, or what curve connects neutrogenicity with stroke power I've seen no data on.

It's important to note that the scientists had failures at first measuring the numbers of neutrons produced because of concurrent arrivals being treated as single neutrons. Not certain what your techniques are like, but if you live in a lightning free zone it hardly matters.

You also need to be sensitive to low energy neutrons, of course.

There are only about 20 air-ground and 80 air-air lightning strokes per second globally, so production from an average single stroke of all types would need to exceed 5*10^13 in order for lightning to be the global leader. That probably doesn't happen. Globally. There should be locations and regions where the lightning neutron flux dominates the averages.
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by DavidStewartZink »

Not to critique your reading comprehension, but the PRL paper REFUTES the photo-nuclear hypothesis.

"The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed."
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by DavidStewartZink »

CW: "The origin of the cosmic secondary neutrons is not explained by electron capture on hydrogen"
DSZ: "Of course cosmic rays don't produce neutrons through electron capture, that's a silly idea, and also: yours."
CW: "Production of neutrons by electron capture on hydrogen was distinctly YOUR idea, David."

Seriously?
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Chris Bradley
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Chris Bradley »

David Stewart Zink wrote:
> I'm not sure what the lightning flux at your house ...has to do with the global values.
....because neutrons made 'globally', miles away, are not going to make it to my house for me to measure. The neutrons will thermalise before getting here and have insufficient energy, nor lifetime, to make the distance. 50% of the neutrons I measure were made locally in the previous 611 seconds .... more than 99.9% of them were made nearby in the last 2 hours.

> I thought we were discussing neutron flux (not muons)
..yes, neutrons which are made by muon bombardments....

Can I ask you, do you think it is better to learn something about the subject you are hoping to discuss, before trying to discuss it?

I think there is a lump of posts here that might be better deleted, as this is meant to be a FAQ.
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Carl Willis
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Carl Willis »

Not quite.

"It means that neutrons observed during the enhancement
event are generated in the air and in the upper layer of
the ground, what may indicate the possibility for neutrons
to be born in photonuclear process by rays generated in
atmospheric discharge." (p. 4)

The rest of p. 4 is the author's discussion about extremely limited data on photon fluxes in and around thunderstorms, and to be fair to you, yes, the point that his measurement challenges the photonuclear hypothesis in the context of the limited findings of one other experiment. It's not fair to call this a "refutation" of the only hypothesis the author actually advances; it's better to say that he calls attention to a reasonable hypothesis, noting that it isn't entirely consistent with spare data from a single other source.

You also want to pick a bone with me about who said what, further up this same thread. I think where you're missing the point of something I wrote has to do with a syntactical lack of clarity in one of my sentences. So let's rephrase my point in a way that gets that manufactured non-issue out of the way. My point is that you said two things, one about the source of most earthly free neutrons, and something else about how they probably come from electron capture, and neither has any attribution to a reliable source, nor is either commonly held to be true in my field. So my point was, and is, that I would like to see your source for those assertions. Very simple, really.

Our experimental hobby fusion community welcomes all honest and respectful comers who want to contribute from their own experience. Chest-thumping wars and pseudoexpertise dropped on a FAQ thread is an inauspicious beginning, though. Let's wrap this nonsense up and move on.

-Carl
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Dan Tibbets
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Dan Tibbets »

David, before others chip in on your misconceptions. Let me make some points. The cosmic rays are not neutrons. Mostly, they are protons. It is not neutrons falling to earth, nor is it electron capture. It is is a pure hammer approach. The kinetic energy of the cosmic ray particles is so high ( over a few MeV, they are atom smashers. They literally tear the target (and possibly themselves) apart. A shower of particles- muons, protons, neutrons, etc are produced.


Google atom smasher, particle accelerators, the Oppenheiner (sp?) effect, etc.

Electron capture can happen in hydrogen, but it is an incredibly rare event, even in the core of the Sun. The cross section is ~ 10^-45 .
In comparison hot deuterium fusion has a cross section of ~ 10^-27, A billion billion times more likely.

Despite cold fusion claims , I know of no evidence for this occurring outside of very dense and hot environments like the core of the Sun.

There is electron captures that occur at significant rates, but this is mostly in heavier elements in the incredibly hot environments of super nova explosions.

Dan Tibbets
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Richard Hull
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Richard Hull »

I hope my last word on this as this post morphs from its original theme of "little to no natural isotopic matter decay neutron emission" to earthly neutron sources.

If there is no thunderstorm in your immediate area, right now, you will measure 0.000000 lightning based neutrons. The neutrons or shall I say the "detection events" in a large volume, sea level based 3He detector are mostly from neutrons created at or near the surface or tube wall/gas events caused by cosmic rays that have made it through the atmosphere or other local, to the detector, cosmogenic events whereby freshly created particles of huge energy are reacting with the tube or gas. Due to a well adjusted discriminator, We can warrant that most events will be neutronic in nature, but when a 10-100mev particle hits the tube wall and stars into the gas, it will be detected! a carefully watched DSO hooked to the output of the tube's preamp will show neutrons versus cosmogenic events as pulse heights that are amazing compared to normal neutron detects.

For our data collecting purposes it is all background. A background that we must subtract from any fusor operational efforts. Whether every background event in our detectors is a neutron of not is of no significance, but we can be sure that anything above this background is a neutron based on a fusion event within our fusors.

For my large 3He detector which is not massive, but just large, I regularly measure only 5-8 events per minute, background, and have recorded a near doubling of this at certain times after a very large CME event on the sun.
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Steven Sesselmann
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Re: FAQ - Why no neutrons exit atoms in natural decay processes

Post by Steven Sesselmann »

?

Am I missing something in this thread...., why would a neutron be kicked out of a stable nucleus?

There is no Coulomb repulsion between the neutron and the other nucleons, so what if anything would kick it out and why?

In the case of fusion neutrons, I think there is a simpler explanation.

When two deuterons are captured in each others cross section, the angular velocity around each other may increase to a point where bits literally fall off, sometimes it is a neutron and sometimes it is a proton. A slingshot effect, similar to that used by spacecraft, to gain additional velocity by moving in a close rendezvous with a planet.

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