Creating a neutron source

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Andrew Haynes
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Creating a neutron source

Post by Andrew Haynes »

Hi would the below picture work for a neutron source using electron capture, if it was at atmosphere pressure and over 188kv for tungsten(blue)?
What would be the mean free path of a neutron at atmosphere pressure and 100kev.

Just guessing here ,electron capture is p + e → n + νe and wiki says for tungsten
iso half-life DM DE (MeV) DP
181W 121.2 d ε 0.188 181Ta
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Chris Trent
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Re: Creating a neutron source

Post by Chris Trent »

This would not appear feasible for a number of reasons.

First, Please read up on electron capture. As I recall the neutron is retained by the nucleus and you will instead get a 188KeV gamma.

Second, an electrical arc will not impact the rate of radioactive decay (which is already quite fierce for the isotope you listed).

Third, but perhaps most important, 181W is a highly radioactive artificial isotope that is a byproduct of nuclear fission. Not only is it dangerous to handle, only a few governments in the world have the capability to produce it. I cant imagine that any appreciable quantity would ever end up in civilian hands.

Do some more research, and good luck.
Andrew Haynes
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Re: Creating a neutron source

Post by Andrew Haynes »

Was only thinking about 181W, because of the low MeV.

Is there anyway to make isotopes with electron or proton of less than 1.022MeV at standed atmosphere
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Carl Willis
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Re: Creating a neutron source

Post by Carl Willis »

Andrew, can you please post some kind of introduction in the appropriate forum as the forum rules specify? Without knowing your background or intentions, answering these kinds of inquiries is kind of a shot in the dark. I'd also like to be assured that this is not some "fishing expedition" in which a person drops in to crowdsource their own homework / professional information needs and has no intention of participating meaningfully in the amateur nuclear fusion community.

I don't understand the basic operating principle your drawing is supposed to illustrate. I see some charged conductors (presumably) and some insulation. You suggest a reaction with an electron and a bound proton that produces a free neutron. Have you looked at the energetics of this hypothetical process? It's not the same as electron capture, where all nucleons remain bound. Can you describe what the electrode / insulator assembly is supposed to do? Why is the tungsten piece disposed at the angle shown?

Another question you asked is about neutron interactions in air, but to address your true information needs requires that you tell us what you want to do. It's not difficult to obtain a very accurate result from a simulation in a program like MCNP, but the effort to set up and run that problem is likely to be wasted unless we know more. Maybe you care about the mean free path of unscattered 100 keV neutrons, which is constant. But you might care about something more complicated, like shielding or dose calculations, where you care about contributions from all the neutrons including scattered ones. Obviously a neutron downscattered to thermal energies has a different mean free path than a fast neutron at 100 keV.

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Re: Creating a neutron source

Post by Andrew Haynes »

Its just a hobby, generator power hopefully

I was going to use a penning trap with a neutron source that would fire into a Ca isotope which is double beta decay, with a hydrogen main source. The idea was to get a type of chain reaction with two electrons coming off for the price of one.

I've download all isotope information and thought that the energies listed were the ones that will create the isotope or decay. I thought electron capture was a proton and electron getting captured and release a neutron, but after rereading it is a gamma ray that comes off.
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Re: Creating a neutron source

Post by Frank Sanns »

The process of electron capture is not and electrostatic process. It is a nuclear process. Bombarding a proton rich atom with electrons will not cause any transmutation. The transmutation occurs when a proton in a nucleus absorbs an already existing electron in the inner shell and converts to a neutron. The space formerly occupied by the inner shell electron is filled with electrons in the outer shells with corresponding photons (gamma rays) being emitted for each energy transition. Once all of this happens, the atom will take on another electron from the local environment. The reverse process of putting electrons in first has no effect as there is no hole for the electron to fill.

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Andrew Haynes
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Re: Creating a neutron source

Post by Andrew Haynes »

Thanks that cleared it up abit,Even if you hit it with alot of energy from a electron it won't create the isotope?.

If you have 3H isotope of 0.01861MeV, if you hit 2H with 18kev with proton ,gamma ray or electron(?) will it turn into 3H, or do you need like 10MeV
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Chris Bradley
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Re: Creating a neutron source

Post by Chris Bradley »

Andrew, I've had a quick look to see if there are any basic 'primers' on this, so you don't have to punt any more of your random guesses about atomic physics into the forum.

Regrettably, there doesn't seem to be much that is particularly simple yet also comprehensive on the web. Maybe we should come up with something here on the forum, but it's always difficult to second-guess what level of spoon-feeding a newb might be expecting. In any case, here are a couple I happened to come across, maybe they will hit the spot for you, and will initiate further self-study:

http://www.s-cool.co.uk/category/subjec ... -structure
http://www.zamandayolculuk.com/cetinbal/uraniumatom.htm
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Re: Creating a neutron source

Post by Chris Trent »

As Chris Bradley says in a later post, we really need to find/create a really good, succinct primer on nuclear physics.

Making isotopes is one thing, any chunk of uranium ore is making a variety of new isotopes all the time. Separating them from one another is something else entirely.
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Re: Creating a neutron source

Post by Andrew Haynes »

Thanks for the links. Firing a electron at a heavy metal will cause back scatting release a xray not a isotope which needs a neutron. Ionizing hydrogen with a voltage will make a positive ion, if that's accelerated at 18kev into another hydrogen atom it might make one because of the proton or neutron?
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Chris Bradley
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Re: Creating a neutron source

Post by Chris Bradley »

If the hydrogen atoms are both 'heavy hydrogen' (deuterium) then that sort of collision energy may result in fusion (into protons, neutrons, tritons and 3He/4He). That's what this whole web-site is about.

If the hydrogen atoms are both just plain, regular one-proton hydrogen then the probability of any sort of fusing event is too small to quantify. Only in the depths of a star, at plasma densities many times that of lead, is such a reaction likely to take effect. At much higher collision energies, though, at GeV levels, then two colliding protons will cause their disintegration and many odd-ball particles can then be observed as they break up, this being the principle of 'collider' physics studies of fundamental particles.
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Re: Creating a neutron source

Post by Andrew Haynes »

Would the reaction of pair production at 1.022 MeV produce enough protons for the probability of fusing to happen.
Some people have talked about SRIM would that be-able to predict it.

Cheers for you patients
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Chris Bradley
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Re: Creating a neutron source

Post by Chris Bradley »

andrew haynes wrote:
> Cheers for you patients
Most of them have lived...




> Would the reaction of pair production at 1.022 MeV produce enough protons for the probability of fusing to happen.
No idea what that means. Sorry. Self-study is king here ... an ever-recommended activity.
Andrew Haynes
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Re: Creating a neutron source

Post by Andrew Haynes »

I'm in the process of building a marx generator to test this out. The only measuring equipment I've got is a multimeter.... if I ground the negative terminal and put the positive in the proton stream, what amount of voltage could I expect , F=mv2 , E = F/q

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Re: Creating a neutron source

Post by Chris Trent »

If the only measuring equipment I've got is a multimeter, then you are truly a long way from any of what you have described in your posts thus far. If you are going to be dealing with nuclear science you will first need the appropriate tools to measure the results. If part of your process is supposed to generate neutrons, then you need to have a way to detect them. You will need other detectors to make certain that you are not being exposed to harmful levels of various other radiation along the way (UV, X-Ray, etc).


As far as your proposed Marx generator. Without having the specifications of your proposed generator, I cannot even begin to guess what voltage, if any, you should expect.

I would recommend that you not do anything with such high voltage until you have learned enough on the subject to confidently predict the voltage that you should expect on your own. You will also need to study how to protect both yourself and your equipment from that voltage, it's not as easy as it sounds, and accidents can be deadly.

There are a number of very helpful HV forums out there that would be good reading. Feel free to post your design and voltage predictions in those forums or here for critique and safety tips. It may be a bit off topic, but we want you to be safe and HV is the most dangerous part of what we do.


One last comment: Start small.
It may sound rudimentary, but before building a massive generator, I challenge you to first design and build a circuit to generate 1000V from a single nine volt battery. I further challenge you to measure it and prove that it generates 1000V, (without destroying your multimeter).
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Re: Creating a neutron source

Post by Andrew Haynes »

Just working on the caps, should allow rapid fire, might at later stage get more cw stages.
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Re: Creating a neutron source

Post by Jim Cotton »

Danger Will Robinson...

Don't try this at home yet.

If you have no clue what you are doing, the 15 kV transformer is a great way to get killed.

Without scaling resistors the multimeter lets the smoke out between .4-1kV.

The meter leads may not even be good to 1kV (insulation).

STOP. read, learn.

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Chris Bradley
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Re: Creating a neutron source

Post by Chris Bradley »

(A smoking multimeter is the least of the issues....)
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Re: Creating a neutron source

Post by Chris Trent »

I wasn't kidding on that 1000 volt circuit first. Build it, then try get up to 2000V and 3000V from the 9v battery. If you make mistakes you will learn from them VERY quickly, sometimes in a rather spectacular or painful fashion.

15KV is far more dangerous and difficult to handle than you may realize. Make the wrong mistakes with that and you will die.
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Re: Creating a neutron source

Post by Andrew Haynes »

I've been experimenting with a ignition coil, and yes discharge a homemade cap throught both hands....lesson learned build it then stand away when you turn the power on, and use one hand.

To move forward I need to use more voltages, i'm also learning stuff from 4hv.org, read all general purpose and high voltage sections.

I will take it slowly thanks for the warnings
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Re: Creating a neutron source

Post by Richard Hull »

I think a re-reading of Carl's reply post, above, is in order. A bit of self study on nuclear matters is in order and perhaps a discussion specific to the HV device might better be handled on one of the many web based high voltage discussion boards.

This discussion is no longer theroetical, (this forum), and is drifting in the direction of the fusor power supply forum.

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Re: Creating a neutron source

Post by Andrew Haynes »

Carl the idea is to send a spark into tungsten to release a neutron or proton. What I understand is a xray will come off. They only data I could find that might make a proton would be if its at 1Mev and the xray will break down to proton and anti proton. The angle is to deflect xray at 90degrees, trying to copy a xray tube from wiki.

There was some book describing a spark chamber with the xrays sent into hydrogen to produce a neutron, but I don't have any ideas about the energy need or how to find out, or what to search for. I do plan on staying I just need to get my head around the numbers, and I thought the capacitor arrangement on the marx might help someone out.

The neutron distance in air was at atmosphere pressure, and how far away the target can be, I'm assuming that above the energy to make a neutron come off, if you add more, the neutron will come off at a high energy level.

If you could fire a proton into D to make He and neutron using 1Mev you could get 2Mev out?, Is it just a small target?

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Re: Creating a neutron source

Post by Frank Sanns »

Andrew,

Enough information has been passed to you by other members of the forum as well as the administrators here. Please do a proper introduction of yourself according to the protocol of fusor.net and search the FAQs or other sources for the information that you seek.

This thread is now closed.

Frank Sanns
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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