Small neutron source

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George Schmermund
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Re: Small neutron source

Post by George Schmermund »

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'!
Anything obvious in high vacuum is probably wrong.
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Richard Hull
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Re: Small neutron source

Post by Richard Hull »

Rhodium is excellent if you can get it! But those are the big three.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Small neutron source

Post by Dennis P Brown »

Protons from any fusion events wouldn't travel through any significant amount of material (a few microns to tens of microns at best) if I recall from my calculations; be rather difficult to measure any considering that limitation even if they were accessible. Detector windows except for maybe beryllium wouldn't generally work for such low energy protons (a few MeV.)

Glad the x-ray radiation is not an issue!

Again, very nice experiment both for the design and confirmation method - your neutron flux is much higher than I would ever have expected considering such a simple apparatus.

I am curious about your target of zirconium - how did you fill it with deuterium?
Rapp Instruments
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Re: Small neutron source

Post by Rapp Instruments »

Hi George, hi Dennis

in the early days of nuclear research desintegration was mostly proved by protons. Researchers used a scintillator screen (ZnS) and counted the flashes with a microscope. The screen was mounted on the vacuum side of the tubes, you so only need a optical window. They were able to discriminate the protons flashes from the continous glow from x-rays, human multi chanel analyzers.
But I think with the most probably D-D reaction D + D > n + He3 there no proton emitted, the second reaction chanel with much lower probability D + D > p + H3 a proton would be emitted.

Zirkonium like some other metalls ( Titan, Palladium) readily absorb hydrogen/ deuterium from surrounding atmosphere, also the ion beam helps to load the surface layer with deuterium.

Hi Richard

altough the price for rhodium has fallen the last years it is still very expensive, but I can try my luck with rather cheap rhodium plated coins, maybe there enough material to see it.

Thomas
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Chris Bradley
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Re: Small neutron source

Post by Chris Bradley »

Rapp Instruments wrote:But I think with the most probably D-D reaction D + D > n + He3 there no proton emitted, the second reaction chanel with much lower probability D + D > p + H3 a proton would be emitted.
Those two routes are approximately (not quite) equal. It is the D+D->4He + hv reaction that is rare, about 1/20000 as likely as the others.

It could be a challenge to look out for the very high energy 24MeV gamma out of that rare reaction.

If you have that level of gamma spectrometry sufficient to discriminate this, another possible case for an interesting experiment is to mix your D with H, and try to detect the D+H->3He + hv gammas. Your linear target setup might lend itself better to that reaction. That would be the first detected amateur non-DD fusion if you could.
Rapp Instruments
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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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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
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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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