eli5 – how are neutrons “fired” ?

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I recently went to see Oppenheimer. In the film they talk about neutron bombardment to split an atom.

How exactly do you “fire” neutrons? I assume its not with some sort of gun lol

Do you put some material in a confined spce and the neutrons fizz around, eventually splitting an atom?

What is done practically?

Explanations welcome, thx

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5 Answers

Anonymous 0 Comments

It depends on what you are trying to do with the neutrons. There are several reactions that produce neutrons. For example, if an alpha particle is absorbed by beryllium, this ejects a neutron. So you could put a strong alpha emitter (like Polonium-210) next to a bunch of beryllium and they’ll start producing neutrons. In the center of the implosion bomb in the movie they have a tiny mixture of beryllium and polonium separated by a gold foil. When the implosion crushes the capsule, the beryllium and polonium mix, creating neutrons. Something similar was used in the early experiment that discovered fission — a mixture of materials that was known to produce neutrons (the Germans used a radon–beryllium source) was put near the uranium they wanted to irradiate, basically.

You could also do a version of this with a particle accelerator, which can spin lots of charged particles up to high speeds. If you accelerate a bunch of deuterium nuclei (“deuterons”) and smash them into beryllium, they’ll also produce a bunch of neutrons.

You could also make a very tiny, not very powerful nuclear fusion source. Nuclear fusion reactions generate a lot of neutrons.

If you want the neutrons you make to be mostly going in one direction, you put the neutron source in a box made of something that can absorb neutrons and then put a little hole in it, so that only neutrons going in one direction can go out of the hole.

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