There are a surprising number of experiments an amateur nuclear physicist can perform, from making a Geiger counter to fusing hydrogen atoms in a fusor. One project which we haven’t seen before is a neutron generator, such as the benchtop neutron generator made by [Rapp Instruments] (translated).
This particular generator takes a feedstock of pure deuterium, which it ionizes and accelerates into a titanium target. The first deuterium nuclei to hit the target react with it to form titanium deuteride, immobilizing them until more ions strike them and they undergo nuclear fusion. The fusion reaction mostly forms helium-4, but sometimes forms helium-3 and a free neutron, which is radiated away. The radiated neutrons are slowed down by a block of high-density polyethylene, and a portion of them strike a silver or indium foil wrapped around a Geiger counter tube. The neutrons activate the silver or indium, and the Geiger counter detects the resultant increase in radioactivity.
The design is a linear particle accelerator built inside an evacuated glass tube. It uses two high-voltage power supplies: a 20 kV supply which ionizes the deuterium gas fed into the tube, and a 100 kV supply which accelerates ions emitted from the source into the target. The target itself is surrounded by a cup-shaped electrode to capture secondary electrons emitted during impact. To prevent arcing, the tube needs to be at a very low pressure, reached by extensive use of an oil diffusion pump.
Radioactivity measurements of the silver and indium foils showed that the generator did work; when irradiating the silver foil for five minutes, it generated 175 counts per second after the neutron source was turned off. Plotting the count rate versus time suggested that a mixture of two silver isotopes was being generated, Ag-110 and Ag-108, based on their half-lives. Irradiation of indium produced a similar exponential decay in radiation.
We recommend checking out the rest of the site; it’s a gold mine of projects, such as this mass spectrometer. For more background on neutron generators, we’ve covered their theory and some of the more common varieties.
A Benchtop Neutron Generator For The Home Reactor
Playing with neutrons is a great project if you want to suddenly pop up on government watch list or even do jail time for creating radioactive materials.
I don’t know what got you excited but your interaction cross section is way to small. I suggest a nice relaxing bath to thermalize. Heavy water if you have it.
Is there anything left, that’s interesting, doesn’t make you fat, and doesn’t cause you end up on a government watchlist? I doubt it.
You could join the army. Instead of being on a government watchlist, you’ll be on a government payroll.
Many of us have done both. Personally, I think if your bosses and local FBI offices aren’t slightly nervous at the prospect of you getting up in the morning then you aren’t working hard enough. It was a good week if I got my O3 to blurt out profanity and my name in the same breath, bonus points if it was in a briefing with the CO.
That’s the “fun” part.
A neutrino beam on the other hand could kill nukes
https://up-ship.com/blog/?p=53262
Travel to a “weakness universe” too:
https://en.wikipedia.org/wiki/Weakless_universe
Now, neutrino communication would eliminate comsats
https://www.reddit.com/r/AskPhysics/comments/1cm18k3/communicate_with_neutrinos/
“…An overall data rate of about 0.1 Hz was realized…”
(https://arxiv.org/pdf/1203.2847)
How are they going to know?
What’s sad is this we’ve reached a level of technology that for mete pennies you can safely generate your own power for mere pennies. There’s no longer a need for huge power plants
This mode of neutron generation isn’t “fast” like a neutristor. It therefore doesn’t have applications in nuclear weapons. While I haven’t done the calculations to validate the assertion, my gut says that the quantity of neutrons generated is also not useful for making neutron (fission) cross section measurements.
i enjoyed that differentiating isotopes of silver — which seems impossible to my intuition — is accomplished by comparing the decay rate over time. If you know what to look for, very tiny and insubstantive things are still detectable
Thank goodness, there’s finally a fun use for all that leftover deuterium I have taking up space in the larder!
It is very expensive to make, not complex in any way. I think Cody’s Lab had a video on making miniscule amounts using the exact same technology used in Norway at the Vemork hydroelectric plant in Rjukan in the 1940’s. There is even a Kirk Douglas 1965 film about the sabotage of the plant called “The Heroes of Telemark”.
And if you run out of deuterium, you can always make more in your electrolytic cell cascade.
Don’t ever play with neutrons, unless you know very well you are doing. I worked as researcher for a few years at an accelerator lab, and we never, never entered the accelerator building when experiments having to do with neutrons were ongoing.
The description of the experiment is however very questionable. Who wrote it clearly ignores that the yield of the reaction D + D -> He4 is much, much lower than that of D + D -> He3 + N (neutron stripping).
I wonder what they are actually measuring…
If you have any thoriated welding rods in your workshop make sure you remove them before running this experiment.
Scarry.
Would be great to have a bit more documentation/theory of operation on the design. Here are some questions I’ve come up with while looking into it:
* Why is there this long feed capillary? What’s the advantage of feeding in the Deuterium via a long pipe like that, is this just for limiting the throughput? Also have you considered using a needle valve similar to what is typically used for DIY fusors, see for example https://fusor.eu/reactor.html#Gas_Needle_Valve
* What vacuum level is required for the project? I’d assume the mean free path will need to be at least in the same order of magnitude as the travel distance of the Deutrium beam.
* Do I understand it correctly that there is a significantly higher pressure before the cathode opening so that the 20 kV supply can generate a gas discharge (leading to ionization) there? And is the hole diameter specifically matched to keep this pressure difference while allowing some ions to get through?
* Do you have an estimate of the Neutron output (and the associated danger level)?
* Have you investigated the initial turn-on behavior? My assumption is that it will take a while to accumulate enough Deuterium atoms in the Titanium to have a real chance of hitting one, so it could take some time with the neutron output going up quadratically until it eventually saturates.