Small neutron source

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
Rapp Instruments
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Real name: Thomas Rapp
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Re: Small neutron source

Post by Rapp Instruments »

Hi Chris,

I agree that I was wrong with my assumption about D +D < p +H3. It should be possible to see the proton with a scintillator screen.

I only have a small volume NaJ (Tl) scintillator and a homemade mca
http://www.rapp-instruments.de/Radioakt ... lation.htm
tested to 1.4 MeV (K40), I don't know if I can see very high energy quants, but I'm going to try.

I will buy hydrogen because I already planned to do desintegration of Li, B, C and F and so I can do the H/D mixing experiment.

For the desintegration I need some higher voltage. I found that arround 100..120 kV ist the highest voltage for the actual design of the single stage tube. I plan to build a multi stage tube like Dennis Brown has done. The individual stages will be feed by the stages of a Cockcroft-Walton multiplier

Thomas
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Chris Bradley
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Re: Small neutron source

Post by Chris Bradley »

Thomas, as I am sure you already know, a conventional CW multiplier does not provide equal current at each node (thus unequal acceleration voltage).

If you would like to improve that then you might like to take a look at an invention of mine:
viewtopic.php?f=11&t=4887
Rapp Instruments
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Real name: Thomas Rapp
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Re: Small neutron source

Post by Rapp Instruments »

Hi Chris

a smart design.
But if I understand the circuit right then the feeding capacitors C1,C2,C3... have to have increasing voltage ratings. For examble, in a 200 kV suppy the last feeding capacitor should have at least 200kV plus the value of the feeding voltage, such high voltage types are not easy to find. If one use serial connection of capaitors to increase the voltage rating one have to use a lot of them. To get the same capacitance at every stage you need one for the frist stage, four for the second, eight for the third and so on.

Thomas
prestonbarrows
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Re: Small neutron source

Post by prestonbarrows »

George Schmermund wrote:Have you given any thought to detecting protons from the DD fusion? That should be doable and you could then petition to be the first candidate to be enrolled into the 'Proton Club'!
This is extremely difficult to do since protons have practically negligible range through any material. This means the detector must be inside the vacuum vessel. Since there is all sorts of other, non-fusion based, charged particles flying around in the plasma environment, you need a pretty sophisticated filter/analyzer to reject all the noise. This usually involved some type of bending magnet and faraday cup; given the MeV energy levels, this requires some pretty serious bending magnets.

It has been done before in the literature for fusors, but only at the University level that I am aware of. The main point is detecting fusion from advanced fuels like He-3 which don't readily put out neutrons. For DD, there is not really a need to mess with proton detection since neutrons are so much simpler to find.
George Schmermund
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Re: Small neutron source

Post by George Schmermund »

pb - It looks like your confused again. This thread is about a beam-on-target accelerator, NOT a fusor. OF COURSE a detector would have to go into a vacuum chamber at the target end of the system. That's why they make scattering chambers for BoT experiments. The chamber need only be large enough to accommodate the experiment, which in this case could be rather small.

The 2" bending magnet I demonstrated (some time back) for use with the micro-cyclotron could be adapted to analyze ~3 Mev protons with a very simple arrangement of slits. The basic construction of the slits could follow the plan of the uC and be adjusted accordingly.

In fact, if a scattering chamber seems too ambitious, the whole magnet assembly and slits w/detector could sit outside the target chamber and still be pumped to high vacuum with a suitable flange. It doesn't get easier than this!
Anything obvious in high vacuum is probably wrong.
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