My question is specific "what methods are there to generate free neutrons"? With a few aside queries and confirmations of undertanding

Now as I understand free protons are far easier to create than free neutrons for human use (free meaning unbounded to a nucleus of an atom). Since neutrons have no charge, it is also more difficult to control their direction, as opposed to protons and electrons that can be directed and targeted.

Protons can be created by simply stripping off the electrons from hydrogen gas. I believe this can be achieved by electromagnetic field (please feel free to expand or correct). I believe this is how CERN produces protons (please can you confirm).

Neutrons are far harder to obtain.

Possible options are:

  1. Fission reactions;
  2. Fusion reactions;
  3. Spallation.

Are there any other methods in addition to the above?

Neutron Production in the universe: Now, I've heard of neutrons stars where protons and electrons combined to neutrons - this is likely to be at very high pressure since the star's gravitation field is so high.

Economical method to generate free neutrons: I was wondering what would happen if protons are accelerated in a CERN type machine and fired into a cloud of electrons. Would neutrons be produced or would hydrogen, or a percentage of both (could this be added to my list of options 1-3)? Would the energy required be large in comparison with any benefit for use in nuclear reactor or medicine applications?


closed as too broad by rob Nov 14 '17 at 23:52

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Relevant: How are the protons for collisions in the LHC made? $\endgroup$ – John Rennie Nov 13 '17 at 12:18
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    $\begingroup$ You seem to have three questions here which are only loosely related. Are you interested in (a) proton production at CERN, (b) possible methods of neutron production, or (c) proton-electron scattering? Each of these is a pretty broad topic I'm going to put your question on hold to give you a chance to clarify; be careful as you edit that you don't invalidate the existing answers. $\endgroup$ – rob Nov 14 '17 at 23:52
  • $\begingroup$ Hi Rob, Thank you for your comments. This forum should be open to all. As a non-physicist I am not qualified to judge whether things are loosely related or not. Science is driven by apparently unrelated concepts being pulled together, and my points are related! Since you are only one person, please can you put my message out to other moderates to vote on the hold? The question raised 2 answers and 2 comments so was a success. The points you raised are logical (right hemisphere of the brain), but my approach is holistic (left hemisphere). I request the hold is released. Thank you. $\endgroup$ – SPIL Nov 15 '17 at 10:23
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    $\begingroup$ This forum should be open to all. Stack Exchange sites are not forums; they're Question & Answer sites. $\endgroup$ – Kyle Kanos Nov 15 '17 at 10:58
  • $\begingroup$ Hi Kyle, yes but there is discussion and debate around the question, otherwise there would be no options to comment. My question is specific "what methods are there to generate free neutrons"? With a few aside queries and confirmations. $\endgroup$ – SPIL Nov 15 '17 at 11:09

CERN produces protons by removing the electrons from hydrogen using an electric field.

Depending on the energy, your idea could create neutrons (as well as neutrinos) and/or hydrogen, at a relatively low probability. That's supposing a "cloud of electrons" is a thing- it isn't really. Electrons are strongly repelled from each other, so if you did have a cloud of electrons, they wouldn't stay around long.

You have the right idea, though. One way to make a neutron beam is to fire a beam of protons or deuterons into a beryllium target, which produces neutrons of roughly the same energy of the protons going in.

If you don't need a neutron beam, this is a very expensive way to produce neutrons, energy-wise. So it's not so useful in conventional reactor applications. There is research into reactors that work with a neutron beam, though. It is what is used in medical applications, however, where a beam is quite necessary.

  • $\begingroup$ Thank you for the interesting answer. I failed to consider the cloud of electrons issue, and did know about beryllium. A couple of other queries, protons can decay to neutrons via beta decay, why can neutrons decay to protons via positron release (seems counter intuitive by conservation laws)? Could we initiate nuclear fission by firing protons at fissile material. Obviously there is a repulsion barrier to overcome, but I wondered whether protons potentially could "proton tunnel" as do electrons when they "electron tunnel"? If yes, would this be of benefit for nuclear reactor design? $\endgroup$ – SPIL Nov 13 '17 at 15:03
  • $\begingroup$ @SPIL there exists bet+ decays , they take energy en.wikipedia.org/wiki/Beta_decay#.CE.B2.2B_decay_2 $\endgroup$ – anna v Nov 13 '17 at 15:34
  • $\begingroup$ Hi Anna, thanks for that. Sorry if my question are slightly naïve, but this forum is open to all questions from people with different backgrounds. I suppose neutron tunnel is not relevant since protons and neutrons are much larger than the electrons. $\endgroup$ – SPIL Nov 13 '17 at 16:17
  • $\begingroup$ @SPIL Free protons cannot decay to neutrons because they are less massive- it's only in a bound state (nucleus) that protons decay into neutrons. Indeed protons can initiate fission, but because they are charged it takes much more energy to reliably cause fission, generally more than you can get back. Protons can tunnel, but the probability is low. There is research into reactors that work by firing neutrons into the fuel though. $\endgroup$ – Chris Nov 13 '17 at 18:53
  • $\begingroup$ Hi Chris, Thank you for your answer. The point about free protons I was unaware of. What equations would I need to calculate the amount of energy protons are required to initiate fission? How can I find out more about proton tunnelling? Is it the probability of tunnelling correlated to the mass of the particle? $\endgroup$ – SPIL Nov 15 '17 at 10:35

You can fire a proton beam into a sample of tritium gas and produce neutrons. Neutron scattering labs often use this method for neutron production. There are several other nuclear reaction methods like this one for neutron production. Several labs use a Van de Graff accelerator to produce a beam of protons or other charged particles to make neutrons.

  • $\begingroup$ Thanks for your answer. That is similar to the snooker analogy of knocking the white ball (proton) against a triangle of three (tritium). I'll look into the Van de Graff accelerator. $\endgroup$ – SPIL Nov 15 '17 at 10:27

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