Creating a neutron source

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
Andrew Haynes
Posts: 90
Joined: Sat Dec 01, 2012 6:25 am
Real name: Andrew Haynes

Creating a neutron source

Post by Andrew Haynes » Sat Dec 01, 2012 6:29 am

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
Attachments
electroncature.PNG
electroncature.PNG (5.51 KiB) Viewed 4487 times
Andrew Haynes

Chris Trent
Posts: 291
Joined: Tue Jan 17, 2006 9:24 pm
Real name:

Re: Creating a neutron source

Post by Chris Trent » Sat Dec 01, 2012 8:36 am

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
Posts: 90
Joined: Sat Dec 01, 2012 6:25 am
Real name: Andrew Haynes

Re: Creating a neutron source

Post by Andrew Haynes » Sat Dec 01, 2012 10:55 am

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
Andrew Haynes

User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 11:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: Creating a neutron source

Post by Carl Willis » Sat Dec 01, 2012 4:54 pm

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.

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277

Andrew Haynes
Posts: 90
Joined: Sat Dec 01, 2012 6:25 am
Real name: Andrew Haynes

Re: Creating a neutron source

Post by Andrew Haynes » Sat Dec 01, 2012 11:04 pm

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.
Attachments
penning.PNG
penning.PNG (7.17 KiB) Viewed 4487 times
Andrew Haynes

User avatar
Frank Sanns
Site Admin
Posts: 1722
Joined: Fri Jun 14, 2002 6:26 pm
Real name: Frank Sanns
Location: Pittsburgh, PA USA

Re: Creating a neutron source

Post by Frank Sanns » Sun Dec 02, 2012 4:43 am

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.

Frank Sanns

Andrew Haynes
Posts: 90
Joined: Sat Dec 01, 2012 6:25 am
Real name: Andrew Haynes

Re: Creating a neutron source

Post by Andrew Haynes » Sun Dec 02, 2012 5:14 am

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
Andrew Haynes

User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 11:05 am
Real name:

Re: Creating a neutron source

Post by Chris Bradley » Sun Dec 02, 2012 6:12 pm

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

Chris Trent
Posts: 291
Joined: Tue Jan 17, 2006 9:24 pm
Real name:

Re: Creating a neutron source

Post by Chris Trent » Sun Dec 02, 2012 6:46 pm

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.

Andrew Haynes
Posts: 90
Joined: Sat Dec 01, 2012 6:25 am
Real name: Andrew Haynes

Re: Creating a neutron source

Post by Andrew Haynes » Sun Dec 02, 2012 7:02 pm

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?
Andrew Haynes

Post Reply