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Creating a neutron source

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Andy

Sat Dec 01 2012, 02:20AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Would the below picture work for a neutron source using electron capture, if it was at atmosphere pressure and over 140kv for tungsten(blue)?
What would be the mean free path of a neutron at atmosphere pressure and 100kev.

Cheers

Patrick

Sat Dec 01 2012, 03:15AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

first, i dont know.
second, were you inspired to build this in the way X-ray-electron-bombardemnt vacuum tubes works?

Andy

Sat Dec 01 2012, 03:25AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Type of, I thought that a spark is electrons get stripped from air. Probably driving a xray tube above that voltage would do it but I would like the ability to build it into something else.

Electrons don't travel there far in atmosphere pressure...

GrantX

Sat Dec 01 2012, 04:58AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

A quick search of neutron sources on wikipedia shows that most methods either involve radioactive isotopes, particle accelerators, or hydrogen/dueterium/tritium fusion reactions (like farnsworth fusors or Z-pinches).
They do mention neutrons generated by high energy photons: "Typically photons begin to produce neutrons on interaction with normal matter at energies of about 7 to 40 MeV"
I am not sure if it would be possible with only 100keV in open atmosphere. In a vacuum chamber, you could easily power a fusor with 100kV.

I'm not very well informed on this subject, but I've been reading a lot of fusor.net in an attempt to learn.

EDIT: Sorry if this is silly, but what are the yellow and grey parts in the diagram?

Andy

Sat Dec 01 2012, 05:33AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Electrode and insulator :).
Just guessing here ,electron capture is p + e â†’ n + Î½e and wiki says for tungsten
iso half-life DM DE (MeV) DP
181W 121.2 d Îµ 0.188 181Ta

Maybe increase the voltage for the less mass of a electron instead of a proton...

Ash Small

Sat Dec 01 2012, 09:54AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

First, building a neutron source is illegal in most countries. The Fusor builders get round this by saying neutrons are produced as a by-product of fusion, and the equipment isn't designed to produce neutrons, just do fusion.

Second, the easiest way to produce neutrons is with a Hirsch-Meeks Fusor. Plenty of amateur builders have achieved count rates of over 1,000,000 neutrons per second.

Third, Wikipedia article on Neutron Generators:

Proud Mary

Sat Dec 01 2012, 12:32PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

As Mr Ash has pointed out, a neutron generator would constitute a 'radioactive apparatus' in the United Kingdom (and hence in the entire EU) whose use, location, security, and safety management are regulated by law.

However, numerous interesting experiments are now being done with cosmic ray spallation neutrons, which have enjoyed a revival of interest in the search for new ways of detecting nuclear contraband.

Andy

Sat Dec 01 2012, 11:14PM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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What about isotopes, creating them. Smoke alarms have radioactive components. What would the limit be before it comes illegal.
I always thought they could use CCl to detect nuclear stuff on the other side off the world by neutrinos

Thanks for the heads up

Ash Small

Sun Dec 02 2012, 12:50AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Andy wrote ...

What would the limit be before it comes illegal.

If it's designed to produce ionising radiation it's illegal without a licence.

EDIT: There are exceptions, Proud Mary has a thread about X-rays of less than 5keV, and you don't need a license for equipment that accelerates particles to less than 1MeV, but anything designed 'to produce neutrons' is illegal.

(As I mentioned earlier, the 'fusioneers' get around it by saying 'it's not designed to produce neutrons, they are a by-product of fusion')

Andy

Sun Dec 02 2012, 04:47AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Posts: 874

Thanks
In the fuser does the reaction happen 2H + p -> 3H + n

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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