Linear accelerator and photo nuclear reactions

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jaaz95
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Linear accelerator and photo nuclear reactions

Post by jaaz95 » Mon Mar 26, 2012 1:55 am

Hey everyone, it's been a while
I posted a long while ago about building a fusor. Unfortunately I think that project will be many years away. However in my quest to build one I did rack up quiet a bit of equipment. I was gonna sell some of it off when I had an idea. Why sell it when you could build something interesting. The goal, is to build a small (5') linear accelerator (drift tube style to start). It'll be powered by a van de graffe and the goal will be to eventually run it at 1 Mev. I'll be starting closer to 200 Kev though. Now building it wont be a problem and i've got most of that sorted already. The problem is what to do with something like that. It has been suggested to me the I could try and achieve some photo nuclear reactions. Im not really familiar with them and not entirely sure how they work but have the gist. So my question really is what interesting science could be done with a device of this size. I through around the idea of fusing hydrogen nuclei to something like iron to make cobalt but I doubt that it has enough energy to do that. I through around the idea of accelerating something heavier than hydrogen or helium, like tin for example, but I dont think it'll have enough energy to do anything interesting other than make some nasty xrays. I also considered attempting to make litchenberg figures which at the moment seems like the only viable thing I can do. So any ideas?

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Chris Bradley
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Re: Linear accelerator and photo nuclear reactions

Post by Chris Bradley » Mon Mar 26, 2012 6:19 am

Justin Atkin wrote:
> The goal, is to build a small (5') linear accelerator (drift tube style to start). It'll be powered by a van de graffe and the goal will be to eventually run it at 1 Mev. I'll be starting closer to 200 Kev though. Now building it wont be a problem and i've got most of that sorted already. The problem is what to do with something like that. It has been suggested to me the I could try and achieve some photo nuclear reactions. Im not really familiar with them and not entirely sure how they work but have the gist.

Sorry, one of us is a bit confused over what you are intending to do.

So, I gather you are intending to make a 200keV to 1MeV 'easy-to-build' x-ray machine that has sufficient intensity that its output can produce measurable nuclear reactions, based on a flimsy knowledge of accelerators?

Is it me?

John Futter
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Re: Linear accelerator and photo nuclear reactions

Post by John Futter » Mon Mar 26, 2012 7:57 am

Justin
protons only make characteristic x-rays of the target material
Lichtenberg figures require an electron beam not a proton beam (other polarity)
200kV helium ion (ie alphas are enough for RBS (Rutherford back scattering) although you will need pretty good detectors SSD's but these can be made from photo pin diodes.

do some more reading --its fascinating

jcs78227
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Re: Linear accelerator and photo nuclear reactions

Post by jcs78227 » Mon Mar 26, 2012 10:40 am

Chris Bradley wrote:

> Is it me?

No Chris, it isn't you. I felt the same way after reading the post. A dozen different directions for this "accelerator" and no solid goal. The fusor that was planned fell through, but a linac...not as big a challenge? At least he gets the gist. (/facepalm)

And I had the same idea John did: read. Buy a really thick textbook, start with contemporary physics, a complete course, and then when you're done come back and ask something specific. FAQ's might suffice, but they have been available and here Mr. Atkin is. Not that I discourage experimentation, but a little knowledge here, and a little knowledge there is not even the beginning of what is required to put an accelerator together. If you're messing up on fundamental particles (charges, for instance), well you have a way to go.

Justin, good luck and read, read, read!

-Jonathan

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Carl Willis
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Re: Linear accelerator and photo nuclear reactions

Post by Carl Willis » Mon Mar 26, 2012 5:26 pm

The lowest photonuclear threshold is around 1.8 MeV, for Be-9(g,n). This cannot be done with a 1-MV beam. It could be done using a cancer-therapy electron linac, which probably exists close to where you live in a cancer clinic. Making arrangements to borrow time on one for that purpose is going to be your only credible avenue to success in the short term.

On the Van de Graaff tangent, I know of NO examples of amateur-built Van de Graaff accelerators reaching MV terminal voltage. All amateur VdGs are air-insulated, and thus quite limited in the voltages they can attain. Maybe some of the largest and most well-constructed machines can crack the 500-kV mark. 200 kV seems more reasonable for homebrew machines of modest size, driving microampere beams in well-designed beamlines adhering to standard air-insulated HV technique.

Photonuclear reactions require accelerated electrons. Protons have different physics. The proton nuclear reactions accessible at 200 keV are quite limited, but perhaps F-19(p,ag) can be accomplished in enough quantity to detect. No amateur successes with proton reactions are known, although they have been attempted using amateur low-energy cyclotron beams.

I mention all this, not to make the point that what you want to do can't be done, but to make the point that every aspect of it breaks new ground and thus won't come easy. A fusor, relatively speaking, is easy.

-Carl
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Richard Hester
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Re: Linear accelerator and photo nuclear reactions

Post by Richard Hester » Tue Mar 27, 2012 5:04 am

Protons - at one time (40 years or so ago) I wanted to use the same reaction that Cockroft & Walton exploited in their voltage multiplier accelerator (they got a Nobel) for fusion energy (Li7 + p = 2He4). Unfortunately, the activation energy is really pretty high, though not out of the range of a properly appointed electrostatic accelerator. Having said that, I never investigated to see what the low energy tail of the reaction rate looked like. Is there any low energy tail? One might be better off investigating protons and a Boron target...

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